한국정보디스플레이학회:학술대회논문집
The Korean Infomation Display Society (KIDS)
- Annual
Domain
- Electricity/Electronics > Display
2004.08a
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Two different kinds of subjects are discussed. One is " Enhanced color space for displays" and the other one is"An application for large format displays". Originally defined color space by NTSC has never been used widely for TVs and information displays as there have been no available display devices. LCD panels with new light sources for backlighting will provide much wider color space. LCD monitors which use these new panels will meet almost 100% with the color space defined by NTSC or Adobe. Now, It is the time to deploy wider color space defined by such as the NTSC or Adobe as the standard of LCD display panels. As the large format display devices with reasonable price have not been available till plasma panels became available, application of these panels as an information display in public space is a quite new experience for us. Various kinds of practical applications are observed and coming out. It will generate many and new types of businesses.
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Recent progress of the in-plane switching (IPS) TFT-LCD technologies is reviewed. We call the improved new technology 'advanced super IPS TFT-LCD(AS-IPS)'. After suppressing the viewing angle dependency of essential display characteristics, recent brightness, viewing angle and motion picture quality has been highly improved. The stage is now introducing it into consumer information appliance for higher display performances, by which we could open a large size digital LCD TVs application.
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A 30-inch WQXGA+ TFT-LCD Monitor has been developed based on in-plane switching mode with multi-domain. This product adopts Cu electrode which, in spite of low resistivity, was not applied to TFT LCD products because of productivity and reliability problems etc. This low resistivity material makes it possible to clear the problem caused by line delay in such high resolution TFT-LCDs. As a results of successful adoption of innovative materials and technologies, our world's largest TFT-LCD Monitor has best performance for high information display.
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Present status of picture quality and the future target status for FPD TV's are shown based on the evaluated result of FPD TVs and CRT TVs. FPD TV will be required to be design under ergonomics concept and to be revised some of the definition for to enrage the market.
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S-PVA is a new technology which enables screen quality advantages over S-IPS and MVA, including high transmittance, >1000:1 contrast ratio, sub-10ms response time, and wide angle of view with no off-axis image inversion and undetectable gamma distortion. This new technology will be described in detail. This paper also addresses the other remaining performance issues facing LCD-TV, including Samsung's plans for addressing these challenges. For example, until recently, inter-gray response time and associated motion blur were significant issues for achieving LCD-TV images quality. Samsung has invented DCC-II technology to achieve sub-10ms response time, and this achievement is described herein. Other technology advancements, including next-generation color performance and ultra-low black performance and improvement of off axis image quality are also discussed in this paper.
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Yoshida, Yasuhiro;Furukawa, Hiroyuki;Ueno, Masafumi;Ikuta, Eiji;Daly, Scott;Feng, Xiaofan;Sezan, Ibrahim;Kikuchi, Yuji;Fujine, Toshiyuki;Sugino, Michiyuki 30
Sharp has developed industry's largest high-definition LC TV, Aquos LC-45GDI. In this paper, we discuss its 10-bit signal processing as one important enabler of its excellent picture quality. Utilizing 10 bits signal processing, in combination with full-spec High-Definition panel and "Intelligent Environment Illumination Sensor", we have succeeded to realize a beautiful gigantic LC TV. -
Electrochromic displays offer the possibility of providing high brightness in reflective mode due to the fact that no polarization of the incident or reflected light is required. The use of appropriately roughened reflective layers can enable the diffuse or Lambertian reflection of light. truly imitating the optical nature of paper as a reading medium. Furthermore, the use of an electrochromic system, essentially an electrochemical device, allows for the integration of charge storage layers, endowing such devices with an on-state memory and associated low power consumption. In this paper we describe the
$NanoChromics^{TM}$ system and overview the several strategies employed towards the migration of this technology to flexible display formats. -
Plasma polymerized para-xylene (
$PP_PX$ ) deposited by plasma-enhanced chemical vapor deposition (PECVD) was used as the barrier layer on the polyethylene terephthalate (PET) substrate to improve lifetime of the flexible organic light-emitting diodes (FOLEDs). The$PP_PX$ barrier layer deposited on top of the PET substrate with plasma power of 30 W at deposition pressure of 0.2 torr showed transmittance spectra good enough to be applied in FOLED on PET substrates. FOLEDs with the$PP_PX$ barrier layer (barrier-FOLEDs) showed similar I-V and B-V characteristics to FOLEDs without the$PP_PX$ layer (control-FOLEDs). The lifetime of barrier-FOLED was two times longer than that of the control-FOLED. With$PP_PX$ passivation layers, lifetimes of both control and barrier-FOLEDs were improved by more than 4 times. These results show that PECVD deposited$PP_PX$ layers can be used as barrier layers for FOLEDs on plastic substrates as well as passivation layers for general OLEDs. -
Fabrication of barrier layer on PES substrate and plastic OLED device by atomic layer deposition are carried out. Simultaneous deposition of 30nm of
$AlO_x$ film on both sides of PES gives film MOCON value of 0.0615g/$m^2$ .day (@38$^{\circ}C$ , 100% R.H). Introduction of conformal$AlO_x$ film by ALD resulted in enhanced barrier properties for inorganic double layered film including PECVO$SiN_x$ . Preliminary life time to 91% of initial luminance (1300 cd/$m^2$ ) for 100nm of PECVD$SiN_x$ /30nm of ALD$AlO_x$ coated plastic OLED device was 260 hours. -
Yi, Jeong-Doo;Kim, Joon-Yeon;Chae, Su-Yong;Kim, Tae-Woo;Cho, Sung-Chun;Chun, Byoung-Min;Kim, Jeong-Nam;Cho, Yoon-Hyoung 51
We have developed a new PDP cell structure called MARI(${\underline{M}}ulti$ ${\underline{A}}node$ for${\underline{R}}eduction$ of${\underline{I}}onic$ effect) and new driving scheme achieving a high luminous efficacy. The MARI PDP has middle electrode inserted between X and Y main electrodes. In the MARI PDP, reset and scan voltage is applied to middle electrode and sustain voltage is applied to X and Y electrode. Using a long gap sustain discharge we accomplished a high luminous efficacy. And we developed 42”full panel adopting MARI structure and new driving scheme and attained luminous efficacy of 2.35lm/W. -
High Xe-content PDP characteristics are discussed. A high efficacy, up to 5 lm/W for a 50% Xe in Ne gas mixture, is realized in 4-inch color PDP test panel designs with low cost stripe-type barrier rib structures, that are powder blasted in soda lime glass. Furthermore, for a high Xe-content a high luminance can be obtained with a relatively small electrode area. Therefore the inter cell gap and the driving margin can be increased in a stripe-type barrier rib structure. Finally, for a high Xe-content the panel lifetime increases, due to increasing luminance and firing voltage stability. Clearly, these findings may direct the design development for next generation PDPs towards a high Xe-content
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We investigated the effect of Xe content variation on the luminous efficiency of two different sub-pixel types, i.e., segmented electrode in delta color arrayed enclosed sub-pixel (SDE) and conventional stripe barrier type, in an ac plasma display panel through three-dimensional numerical simulations. The conventional cell type was found to have higher VUV generation efficiency as compared with that of SDE structure, but as the Xe content increased, the SDE type showed higher improvements in efficiency due to the lower plasma loss to the barrier walls.
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Transparent MgO thin films were deposited on glass substrates by electron beam evaporation of MgO (99.99%) under
$O_2$ atmosphere at 150-250$^{\circ}C$ . These films were characterized for their useful properties such as thickness, transmission, and refractive index using ultraviolet / visible (UV/VIS) spectrophotometer, scanning electron microscopy (SEM), and Spectroscopic Ellipsometry. The thickness of MgO films were measured by alpha step instrument and found to be 600 nm to 1000 nm and are meeting the stoichiometry. The transmission spectrum of these films shows transmittance values${\sim}$ 92%.. -
System-on-glass technology made with low temperature poly-Si TFT has been rapidly advancing in recent years. We have developed a low-power, narrow edged frame, 1.9inch system-on-glass LCD which fully integrates a 16-bit RGB interface driver and all power circuits required for driving the LCD. In this paper, the latest poly-Si TFT circuit technologies used in the newly developed LCD are discussed. The development trends are also reviewed.
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By the SOG (System-on-Glass) technology with excimer laser anneal process, the number of IC chips and the area of the mounted IC chips on the printed circuit board are reduced. In new circuit integrations on the glass substrate, we have developed D/A converter including the new capacitor array, amplifier comprising the original comparators and new display device with capturing images by integrated sensor into a pixel. This paper discusses the application of circuit integration of low-temperature poly-Si.
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Required characteristics of poly-Si TFT's are investigated for the implementation of analog circuits to be integrated on System-on-Glass (SoG). Matching requirements on resistor values, threshold voltage and mobility of poly-Si TFT's are derived as a function of the resolution of display system. Effective mobility of poly-Si TFT's required for the realization of source driver is analyzed for various panel sizes.
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Kim, Chul-Ho;Kim, Chul-Min;Moon, Kook-Chul;Park, Kee-Chan;Kim, Il-Gon;Joo, Sueng-Yong;Park, Tae-Hyeong;Maeng, Ho-Suk;Jung, Eu-Jin;Kim, Chi-Woo 85
2-inch qVGA (240${\times}$ 320) TFT-LCD with integrated 6-bit source driver is reported. The pixel density is over than 200ppi and the operation frequency is about 2.8MHz. In order to improve TFT characteristics, TS-SLS (Two-Shot Sequential Lateral Solidification) technology has been employed. A 1:6 demultiplexing scheme has been successfully implemented in the source driver owing to the superb characteristics of the TS-SLS TFTs, which resulted in small driver circuit area. -
We report on the opto-electronic properties of red, green, and blue poly (fluorene) co-polymer light-emitting devices (PLEDs) fabricated on a flexible plastic substrate. The plastic substrate used has a multi-layer structure with water vapor and oxygen transmission rates of less than
$10^{-5}$ g/$cm^2$ -day-atm and$10^{-7}$ cc/$cm^2$ -day-atm, respectively. We obtained a wide range of color gamut and a maximum emission efficiency of 0.7, 10, and 1.7 cd/A for red, green, and blue PLEDs, respectively. Finally, a simple equivalent circuit model is proposed to simulate PLED current density-voltage characteristics. -
We studied a low temperature ion doping process for poly-Si Thin Film Transistor (TFT) on plastic substrates. The ion doping process was performed using an ion shower system, and subsequently, excimer laser annealing (ELA) was done for the activation. We have studied the crystallinity of Si surface at each step using UV-reflectance spectroscopy and the sheet resistance using 4-point probe. We found that the temperature has increased during ion shower doping for a-Si film and the activation has not been fulfilled stably because of the thermal damage against the plastic substrate. By trying newly a pulsed ion shower doping, the ion was efficiently incorporated into the a-Si film on plastic substrate. The sheet resistance decreased with the increase of the pulsed doping time, which was corresponded to the incorporated dose. Also we confirmed a relationship between the crystallinity and the sheet resistance. A sheet resistance of 300
${\Omega}$ /sq for the Si film of 50nm thickness was obtained with a good reproducibility. The ion shower technique is a promising doping technique for ultra low temperature poly-Si TFTs on plastic substrates as well as those on glass substrates. -
We report a novel manner for preparing single layer anti-reflective coatings with excellent optical properties (<1% reflection) over a broad wavelength regime. The technology is based upon the self-assembly and UV curing of reactive nano-particles, leading to nano-structured coatings with a gradient in refractive index. The single processing step leading to such coatings is fast, robust and cost effective. Furthermore in this paper we will address the mechanical durability of such nano-structured coatings.
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The plasma tube array display is expected to realize the wall size display with very high luminous efficacy. The cell design for high luminous efficacy was investigated. Also discharging in plasma tube was observed to investigate the structure for high luminous efficacy. As the result, high luminous efficacy of 5.4 lm/W was achieved.
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Park, Sang-Dae;Lee, Seung-Hun;Shin, Nam-Hoon;Lee, Kyo-Sung;Park, Sung-Yun;Kim, Sang-Ho;Shin, Bhum-Jae;Choi, Kyung-Cheol 109
The effect of auxiliary electrode on the discharge characteristics in AC PDP with long sustain-gap was investigated. The auxiliary electrode was placed between scan and common electrode. When the pulse was applied to the auxiliary electrode during sustain period, the luminance of Ne + 13%Xe gas-mixture discharge increased and the discharge current decreased. The auxiliary pulse plays a role of improving electron excitation efficiency. When the auxiliary pulse was applied during address period, the address discharge time lag of Ne + 13%Xe gas-mixture could be reduced remarkably. -
In this study, the causes of temporal bright image sticking problem in an AC PDP were investigated. The temporal bright image sticking problem in an ac PDP is observed to be a relatively lower luminance following several minutes on-time at a high gray level compared to that of the ordinary turned-on image area. We focused on the detailed causes of image sticking, which are directly related with the visible emission such as the changes in the characteristics of phosphor, MgO surface and gas dynamics. The experimental results show that the thermal quenching of phosphor and temperature-dependent discharge characteristics change cause the image sticking problem.
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This paper describes low temperature poly-Si (LTPS) TFT system on glass (SOG) technology developed in NEC. High resolution SOG-LCDs such as a 230 ppi reflective type LCD, a 2.5", 333 ppi 2D/3D autostereoscopic LCD, and a 2.1" single voltage driven full integration LCD for mobile applications and a 0.9", XGA light valve for projectors are reviewed from the perspective of the high resolution technologies
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A Poly-Si and a ITO films with surface roughness 1.8 nm and 0.5 nm of root mean square (
$R_{rms}$ vakue) values were developed, respectively. A 3 inch UXGA LTPS TFT-LCD with 667 ppi resolution and a 10 inch VGA LTPS OLED have been developed and demonstrated using PMOS technology. -
The development of fabrication processes of polycrystalline-silicon-thin-film transistors (poly-Si TFTs) at low temperatures is reviewed. Rapid crystallization through laser-induced melt-regrowth has an advantage of formation of crystalline silicon films at a low thermal budget. Solid phase crystallization techniques have also been improved for low temperature processing. Passivation of
$SiO_2$ /Si interface and grain boundaries is important to achieve high carrier transport properties. Oxygen plasma and$H_2O$ vapor heat treatments are proposed for effective reduction of the density of defect states. TFTs with high performance is reported. -
This paper describes the architecture, the basic operation principle and detailed experimental results of digitally programmable high-voltage generators that can be used in monolithic low-power high-voltage bistable LCD drivers. Two different design approaches, depending on whether the application allows the use of external passive components or not, are analyzed.
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A QVGA active-matrix backplane is produced on a 25
${\mu}m$ thin plastic substrate. A 4-mask photolithographic process is used. The insulator layer and the semiconductor layer are organic material processed from solution. This backplane is combined with the electrophoretic display effect supplied by SiPix and E ink, resulting in an electronic paper display with a thickness of only 100${\mu}m$ . This is world's thinnest active-matrix display ever made. -
Miyasaka, Mitsutoshi;Hara, Hiroyuki;Takao, Hiroki;Tam, Simon;Payne, Rob;Rajalingham, Prem;Inoue, Satoshi;Shimoda, Tatsuya 145
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A new joint source channel coding reduces both input-width and average current consumption to transmit image data to LCD source drivers. As a source coding, it is based on entropy coding of differential pulse code modulation scheme, especially using median edge detector of image predictor. As a channel coding, it is not a simple pulse amplitude modulation, but linked by source entropy to reduce average amplitude. Simulation results show 1/4 width is achievable by 16-valued transmission with keeping conventional current consumption (0.36 to 1.3).
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A newly developed flexible active-matrix (AM-) electrophoretic display (EPD) is reported. The AM-EPD features: (1) low-temperature polycrystalline silicon (LTPS) thin film transistor (TFT) technology, (2) fully integrated scan- and data-drivers, (3) flexibility and light-weight realized by transferring the whole circuits onto a plastic substrate using
$SUFTLA^{TM}$ (Surface Free Technology by Laser Annealing/Ablation) process. A large storage capacitor is formed in each pixel so that driving electric field can be kept sufficiently strong during a writing period Two-phase driving scheme, a reset-phase which erases a previous image and a writing-phase for writing a new image, was chosen to cope with EPD's high driving voltage. The flexible AM-EPD has been successfully operated with a driving voltage of 8.5 V. -
We have introduced fourth generation PDPs last year. The performance of these PDPs is the highest level among TV displays. At the same time the power consumption of them has reached to the lowest level among FPDs (Flat Panel Displays). High panel luminous efficacy and low address power are necessary for the reduction of total power consumption. Following technologies have been developed and applied to the fourth generation PDPs. High panel luminous efficacy: T-shape electrode, waffle rib structure, high Xe content gas Low address power; CLEAR driving method, etc.
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Choi, Joon-Young;An, Jung-Soo;Kim, Hun-Hee;Lee, Ho-Jun;Lee, Hea-Jun;Kim, Dong-Hyun;Park, Chung-Hoo 164
Misfiring is often observed during the high temperature quality assurance test of plasma display panel. This limits the productivity of PDP industry. In this paper, experimental observations on the misfiring at high panel temperature have been performed through time dependent discharge light output and static margin measurement. For the high temperature condition, firing voltage increment is found in both surface and facing discharges. This in turn increases time lag in address discharge, and results in increment of misfiring probability. In order to reduce this kind of misfiring, a new method that applies automatically different slope of ramp erasing pulse on the common electrode according to temperature variation is proposed. The experimental results show that controlling the slope of ramp erasing pulse is quite effective for compensating temperature-dependent variation of reset and address discharge. -
Choi, Joon-Young;Choi, In-Ju;Park, Mi-Young;Lee, Ho-Jun;Lee, Hea-Jun;Kim, Dong-Hyun;Park, Chung-Hoo 171
Need of a dimmer function becomes more important with increasing interest on a HDTV for home theater applications. In a conventional ac PDP, a possible method to reduce luminance of a whole panel is to reduce a total number of sustain pulses and then to change the gray level. However, the reduction of the total sustain number causes the step of luminance to be rough Moreover, it is impossible to control the luminance of the panel for a given gray level. In this paper, a simple and robust method is proposed to control linearly the luminance of whole panel by applying the asymmetric sustain pulses in the display period of the ADS driving scheme. As the range of luminance control by the proposed method is about 50% for a given gray level. Moreover, it is experimentally verified that the proposed method shows similar dynamic margin performances compare with the conventional method. -
The effects of a temporal image sticking phenomenon on the subsequent dark and white background images are investigated in 42-inch PDP-TV and the reducing method is proposed In addition, the changes in luminance and temperature with an increase in time with the conventional and large sustain gap. The temporal dark image sticking was reduced considerably by decreasing background luminance and it was found that the temporal image sticking with large sustain gap was reduced when compared with the conventional sustain gap.
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Kim, Sung-Han;Hsu, Che;Zhang, Chi;Skulason, Hjalti;Uckert, Frank;Lecloux, Dan;Cao, Yong;Parker, Ian 183
The most significant degradation problem of PLED has been described and new buffer layer material aimed for use as HTL in PLED to solve this issue has been studied. This approach has enabled the increase of the green device efficiency (${\sim}$ 2x) and lifetime (${\sim}$ 5-6x). -
As an effort to reduce cost and lead-time and to increase flexibility and responsiveness, manufacturers are using digital printing in numerous process steps. Typically, these processes require the precise dispensing of various fluids. Piezo ink jet printheads are proving to be reliable tools for depositing active materials such as light emitting polymers (LEP) for mobile phone displays and color filter inks for liquid crystal displays. Ink jets are also being used to provide uniform coatings of polyimide alignment layers and spacers for LCDs. Success with legend printing on PCBs using ink jets has encouraged the design of equipment for directly printing both etch resist and solder mask for PCBs. Development of printers for passive components such as capacitors and resistors is underway. This paper will present the attributes of an ink jet printhead designed to a precision deposition tool and discuss how it is being used to digitally print electronic and flat panel display components. Status of commercialization of digital printing will be discussed along with issues to be resolved before wide adoption takes place.
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The effect of the temperature dependence of the smectic layer spacing in the smectic-A (SmA) phase on the formation of defects in the ferroelectric smectic-
$C^{\ast}$ ($SmC^{\ast}$ ) phase is investigated with x-ray scattering technique. The study is based on thin parallel-aligned surface stabilized ferroelectric liquid crystal cells with two different alignment conditions, high pretilt$SiO_x$ , alignment and low pretilt polyimide films. It is found that defects observed in the$SmC^{\ast}$ phase have much more profound dependence on the layer changes and chevron formation in the SmA phase than in the$SmC^{\ast}$ phase. We find that thermal layer expansion with decreasing temperature in the SmA phase suppresses the formation of defects observed in the SmC phase. -
We have developed a multi-domain vertically aligned liquid crystal display (MVA-LCD) that produces natural gray-scale images even at high viewing angles. We divided each pixel into two areas and set different threshold voltages for each sub-area. A transparent electrode in a sub-area is not connected directly to the source electrodes but via the capacitance of the SiN layer. In particular, light-orange skin color appears very natural, even at a high inclination angle. The contrast ratio is over 500 in the normal direction and over 10 from any viewing angle.
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We study theoretically optical properties of thin layered stacked monochrome cholesteric liquid-crystal displays. Thin thickness of the layers (
${\sim}1{\mu}m$ ) allows us appreciably to reduce driving voltage and use such displays in smart cards. Good selective reflection is achieved due to stacked structure. Dependence of the reflectivity of this type of displays on the quantity of the layers, their thickness, and liquid crystal birefringence is investigated. -
Song, Jang-Kun;Jun, Man-Bok;Park, Bo-Yoon;Seomun, San-Seong;Lee, Kye-Hun;Choi, Kwang-Soo;Kim, Sang-Soo 205
The switching mechanism of multi-domain vertical alignment mode LCD and delayed on response time phenomenon in special conditions are investigated. A modified DCC (Dynamic Capacitance Compensation), DCCII has been developed for the fast response time performance in PVA TFT-LCD TVs. DCCII applies a pre-tilt voltage to addressed pixels during the previous frame in addition to an overshoot voltage. In result, the response time less than 8 msec, has been obtained for all moving images through the DCCII technique. -
A navel fast-switching LCD with dual-domain bend (DDB) mode is described DDB alignment is achieved using antiparallel-rubbed cell filled with chiral-doped LC. Initial alignment is mono-domain 180-degree twist. Tilt direction is controlled by oblique electric field to be counter direction in each domain Twist-to-DDB deformation occurs continuously so that DDB mode does not require high-voltage initialization which is inevitable in Optically Compensated Bend (OCB) mode. DDB gives wide and symmetric viewing angle in contrast to mono-domain bend formed from 180-degree twist showing strong asymmetry.
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We reported two new techniques of barrier rib formation that are applicable to a variety of structures for high-efficiency PDPs suitable for mass-production [1]. These two methods are mold replication and direct glass sculpting. Especial progress has since been made in improving these methods to be more suitable for high-efficiency PDPs with the DelTA cell structure. This paper reports photolithographic fabrication methods for the masters used in mold replication. The masters for more complex barrier rib forms are easier to make with these methods. The paper also reports a process that combines the direct glass sculpting method with an ink-jet printing method of electrode formation.
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Feasibility of BaO-ZnO-
$B_2O_3$ (BZB) based glass system in the light of dielectric and thermal expansion properties are reported in the literature. Effects of addition of various types of ceramic fillers to the BZB-based glass on the thermochemical stability and mechanical properties were investigated in the present work. The studied filler-glass system demonstrated a capability to host various types of ceramic fillers to form thermochemically stable microcomposites at the processing temperature suitable for PDP systems. At the same time, mechanical strength of the filler-glass composites was much improved as compared to the glass itself These observations brighten the feasibility of the Pb-free BZB-based glass system as a host to employ various types of crystalline ceramic fillers so that it can be applied to barrier rib material in plasma display panels. -
MgO thin films were deposited bye-beam evaporation on
$SiO_2$ /Si wafers for the application of a protective layer in alternating current plasma display panels (AC-PDPs). Three different MgO sources, single crystal, melted polycrystal and sintered polycrystal, were used to find out the change of the properties of MgO protective layer depending on the source type. The properties of MgO thin films such as density, orientation and surface morphology were influenced by the source type. MgO thin films deposited with the melted polycrystal source had the highest density with the highest (100) preferred orientation, whereas the films deposited with the sintered polycrystal source had the lowest density with less preferred orientation. Such a result seems to be originated from the different mobility of adatoms on the surface of the deposited MgO thin films. Different microstructures of MgO thin films deposited even in the same deposition condition were observed depending on the MgO source type, resulting in different discharge characteristics. -
Phosphor layers on rear plate of PDP were formed via osmosis coating process in an attempt to improve thickness uniformity of phosphor layer and eventually to enhance luminance and its efficiency of plasma display panel. The phosphor layers were formed uniformly not only on the sidewalls of barrier ribs but also on the dielectric layer of rear plate by the process. The processing parameters affecting the thickness uniformity of the phosphor layer formed by the osmotic coating process were investigated.
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Choi, Kwang-Yeol;Min, Byoung-Kuk;Kim, Tae-Hyung;Song, Byung-Soo;Yoo, Eun-Ho;Kim, Jin-Young;Jung, Yun-Kwon;Kim, Won-Tae;Yang, Hee-Chan;Ryu, Jae-Hwa 231
High performance 42 inch XGA PDP with high luminance of 1,000 cd/$m^2$ has been developed using high efficient electrode structure, discharge gas and closed barrier ribs. For high speed addressing with single scan technique, address discharge time lag was reduced over 40% with FAST driving scheme and new materials. High dark room contrast ratio of 5,000 : 1 was achieved and picture quality was improved using new algorithm for eliminating false contour and improving gray level linearity. -
This paper presents a novel contrast enhance algorithm for images displayed with bright environment light. This algorithm is designed to preserve local contrast based on the luminance ratio of the pixel to its local surround in attention. This algorithm improves image quality of projectors in a bright room.
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In this paper, we have proposed the contrast control method using brightness preserving on the FPD(Flat Panel Display). The proposed algorithms consist of three blocks: the contrast enhancement, the white-level-expander, and the black-level-expander. The proposed method has employed probability density function in order to control the brightness of the image changed extremely. In order for real-time processing, we have calculated cumulative density function using the linear approximation method. The image histogram and image quality were compared with the conventional image enhancement algorithms. The proposed methods have been used in display devices that need image enhancement such as LCD TV, PDP, and FPD.
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We have developed a system that measures the visual contrast of people of various ages (from teens to those in their 70s) when they look at different color patterns. We have applied this system to Web-safe colors (216 colors), and have developed an age-related visual contrast checker that can be used to quickly determine whether a color pattern consisting of any two colors is easy to see.
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We developed a novel Fame interpolation method to interpolate a frame between two successive original frames. Using this method, we are able to apply a double-rate driving method instead of an impulse driving method where a black Fame is inserted between two successive original Fames. The double-rate driving method enables improvement to the motion blur of LCDs caused by the characteristics of human vision without reducing the luminosity of the whole screen. Here, we report on the initial model of our frame interpolation method.
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Yuuki, A.;Agari, M.;Iwsaki, N.;Sasagawa, T.;Tahata, S.;Satake, T.;Murakami, O.;Oda, K.;Ito, A.;Miyake, S. 255
We have developed the Scan-backlight Stereoscopic LCD that is a kind of field-sequential -Stereoscopic LCD combining the Dual-Directional-Backlight and the fast-response OCB panel. The Dual-Directional-Backlight using a double-sided prism sheet can change the direction of light by switching the LED light sources. The OCB panel using Feed-Forward Drive can realize frame rate of 120 Hz. As a result, the Scan-backlight Stereoscopic display works at its original resolving power, and produces flicker-free stereoscopic images. This auto stereoscopic display can resolved the problems of the double images and the pseudoscopic images in case of watching at oblique angles. -
We propose novel schemes to enhance the expressible depth range of integral imaging. The implemented system that adopts the mirror barrier array has the compact thickness that is suitable for the practical use. With this system, the expressible depth range of the integral imaging is increased to over 120mm. The system that eliminates the mechanical motion also had been implemented. Experimental results are presented and the way to resolve the problem of occlusion is also discussed.
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We have developed a highly efficient and stable blue organic electroluminescent device (OLED) based on the blue fluorescent p-bis(p-N,N-diphenyl-aminostyryl)benzene (DSA-Ph) dopant in a morphologically stable high-bandgap host material, 2-methyl-9,10-di(2-naphthyl)anthracene (MADN), which achieved an EL efficiency of 9.7 cd/A and 5.5 lm/W at 20 mA/
$cm^2$ and 5.7 V with a Commission Internationale d'Eclairage coordinates of(x = 0.16, y = 0.32). This sky blue device which could also alleviate the problematic current induced quenching at high current achieved a half-decay lifetime ($t_{1\;2}$ ) of 46,000 h at an initial brightness of 100 cd/$m^2$ . -
In this report, high-performance organic light-emitting diodes (OLEDs) with polytetrafluoroethylene (Teflon) buffer layer are demonstrated. Compared with conventional buffer layer, copper phthalocaynine (CuPc), Teflon film shows lower absorption in the wavelength from 200nm to 800nm The OLEDs with Teflon and CuPc buffer layer were fabricated under same conditions, and the device performances were compared. The results indicate that when the thickness of Teflon is 1.5nm, the performance of OLEDs is greatly enhanced with an efficiency of 9.0cd/A at the current density of 100mA/
$cm^2$ , while the device with an optimized 30-nm-thick CuPc buffer layer only shows an efficiency of6.4cd/A at the same current density. -
Great strides in organic light emitting device (OLED) technology have resulted in a number of commercial products. To continue this growth into large area displays, for example televisions, an understanding of the mechanisms that drive the OLED device efficiency and lifetime performance is critical. In this work, we consider maximizing the efficiency lifetime product based on phosphorescent OLED (
$PHOLED^{TM}$ ) technology. We report green PHOLEDs with luminous efficiency of 82 cd/A, 5.7 V and 10,000 hours lifetime at 1,000 cd/$m^2$ ,red PHOLEDs with CIE of (0.67,0.33), 11 cd/A and 35,000 hours lifetime at 500 cd/$m^2$ and recent progress in blue demonstrating efficiencies of 18 cd/A at 200 cd/$m^2$ . -
Thin-film photosensors on organic light emitting diode (OLED) glass substrates using active-matrix OLED TFT manufacturing processes have been constructed and optimized, and their performance has been characterized. Suitable control circuitry and applications are proposed. The photosensors may be integrated into OLED displays for detection of ambient illumination and for detection of OLED light emission, thereby enabling output, uniformity, and aging compensation.
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Photo-induced memory effect of an organic light-emitting diode(OLED) composed of a hydrazone-derivative(DBAH) dispersed in bis-phenol-A type polycarbonate polymer(PCA) in the presence of thio-Michler's ketone, was investigated by the measuring of the current density and luminance at the various conditions. After the light exposure, the current of the OLED was decreased approximately one order, and the luminance of the OLED also decresed. This memory effct was erasable by heating the OLED to the temperature higher than the glass transition temperature(Tg). As shown in this result, we found the memory effect was erased by heating and returned to its original state in the hole injecting layer(HIL) of the OLED. A series of these phenomena was suggested the possibility of the application to the imaging plate.
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We report on the development of ferronematic liquid crystals, new materials that consist of a dilute suspension of ferroelectric particles in a nematic liquid crystal host. The particles share their ferroelectric properties with the nematic liquid crystal and impose a spontaneous dielectric polarization of about 10 nC/
$cm^2$ to the entire medium, typical for many ferroelectric liquid crystals. As expected, these new materials have enhanced dielectric anisotropy and are sensitive to the sign of an applied electric field. The potential of their use in a number of devices are discussed. -
Barron, Cecile;Angele, Jacques;Bajic, Lorenzo;Dozov, Ivan;Leblanc, Francois;Perny, Sebastien;Specht, Jorg;Brill, Jochen 289
We have successfully fabricated$Binem^{(R)}$ displays on thin flexible plastic substrates. The fabrication is based on the standard$Binem^{(R)}$ process for glass which has been adapted to plastic with new materials and technologies. The first application is targeted to an embedded display for smart card products. -
We first report an application of plastic LCDs to 2D-3D convertible mobile phones. Plastic LCDs are proven to be most suitable solution for filter LCDs attached on main LCDs of 3D mobile phones in terms of quality and cost wises. The design and fabrication of plastic LCD filters are discussed in this paper.
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Buchnev, O.;Reshetnyak, V.;Reznikov, Yu.;Tereshchenko, O.;Dusheiko, M.;Cross, L.;Kwon, Soon-Bum 297
We developed a rollable bistable LCD whose substrates are bonded by elastic glue and slide over one other when the LCD is rolled. We produced a 2.5 inch active area, 16x16 pixels prototype and demonstrated multifold bending and rolling of the display in a tube with 2 cm diameter. -
Lee, J.H.;Kim, Y.H.;Sohn, C.Y.;Lim, J.W.;Chung, C.H.;Park, D.J.;Kim, D.W.;Song, Y.H.;Yun, S.J.;Kang, K.Y. 305
We present a novel process for the ultra low temperature (<150$^{\circ}C$ ) polycrystalline silicon (ULTPS) TFT for the flexible display applications on the plastic substrate. The sequential lateral solidification (SLS) was used for the crystallization of the amorphous silicon film deposited by rf magnetron sputtering, resulting in high mobility polycrystalline silicon (poly-Si) film. The gate dielectric was composed of thin$SiO_2$ formed by plasma oxidation and$Al_2O_3$ deposited by plasma enhanced atomic layer deposition. The breakdown field of gate dielectric on poly-Si film showed above 6.3 MV/cm. Laser activation reduced the source/drain resistance below 200${\Omega}$ /ㅁ for n layer and 400${\Omega}$ /ㅁ for p layer. The fabricated ULTPS TFT shows excellent performance with mobilities of 114$cm^2$ /Vs (nMOS) and 42$cm^2$ /Vs (pMOS), on/off current ratios of 4.20${\times}10^6$ (nMOS) and 5.7${\times}10^5$ (PMOS). -
Static and transient behaviour of Low Temperature Poly-Si TFTs (LTPS-TFTs) and Single Grain TFTs (SG- TFTs) are compared 3-D simulation is applied here for the first time to TFTs to account for the structure and twin boundaries in SG-TFTs.
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We developed a vapor induced crystallization (VIC) process for the first time to obtain high quality polycrystalline Si films by sublimating the mixture of
$AlCl_3$ and$NiCl_2$ . The VIC process enhanced the crystallization of amorphous silicon thin films. The LPCVD amorphous silicon thin films were completely crystallized after 5 hours at 480$^{\circ}C$ . It is known that needle-like grains with very small width grow in the Ni-metal induced lateral crystallization. In our new method, the width of grains is larger because the grain can also grow perpendicular to the needle growth direction. Also the interface between the merging grain boundaries was coherent. As the results, a polycrystalline film with superior microstructure has been obtained. -
We report on progress in developing high-power excimer lasers as well as UV-optics for creating low-temperature poly silicon (LTPS). A new high-power excimer laser offers 315 Watts with high pulse to pulse energy stability. Larger substrates can now be processed in better quality with either the SLS process or the new optics for line beam excimer laser annealing.
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Novel surface profiler system for inspection of the display components is demonstrated In the case of the liquid crystal display, for example, not only the flatness of the alignment film but also the quality of rubbing can be inspected. Furthermore, the shape of the component such as the color filter, electrode and mirror can be inspected without removing each component.
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In order to stabilize the rubbing process for liquid crystal panels, the authors developed "the sparkling dot area ratio evaluation method". This method quantifies the fiber length dispersion of rubbing cloths, which is a major cause of mura defects. The newly developed method enables quantitative evaluation of rubbing cloths and contributes to the improvement of rubbing process uniformity.
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A new measurement scheme is proposed to generate an optimized boost table for video rate LCD response time compensation. This method, which closely follows basic theory, enables up to a 90% reduction in the lookup table creation time compared to conventional methods. Furthermore, while conventional approaches require all measurements to be repeated in order to load the entire LUT whenever key parameters such as refresh rate or boost intensity are modified, the method proposed in this paper allows the new table to be calculated by utilizing saved waveform data without the need for any repeated measurements.
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Since 1992, Philips has been developing polymer OLEDs resulting in a first commercial monochrome display just 10 years later. Philips is now focusing on the technology development required to mass-produce full-color polymer OLDE displays, based on passive and active-matrix addressing. High precision inkjet printing has been chosen as the deposition technology for the OLED material. In this paper, we give an overview of the activities of Philips in the area of mobile OLED applications and explore the route towards large screen OLED television.
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Nathan, Arokia;Alexander, Stefan;Sakariya, Kapil;Servati, Peyman;Tao, Sheng;Striakhilev, Denis;Kumak, Anil;Sambandan, Sanjiv;Jafarabadiashtiani, Shahin;Vygranenko, Yuri 343
As a first demonstration of proven stability for a-Si, over 7000h of stability data for a high drive current a-Si AMOLED pixel driver circuit was presented at SID 2004. Also demonstrated was an AMOLED display operating at 6V using the IGNIS 4-T pixel driver circuit [1] and based on a top-emission reverse OLED architecture. In this paper, an update to that information is presented with test data that is representative of lifetime in excess of 25,000 hours taking into account pertinent acceleration factors, extracted from high current drive and high temperature stressing conditions. Lifetimes will continue to increase, given the high and ever-increasing OLED efficiency. -
We describe a new approach for building organic light-emitting diodes (OLEDs), which is based on physical lamination (i.e. soft contact lamination (ScL)) of thin metal electrodes supported by an elastomeric layer (polydimethylsiloxane) against an electroluminescent organic. We find that the devices fabricated have much better performance than those constructed with conventional vacuum deposition process. In addition, the ScL is intrinsically compatible with the technique of soft lithograph so that it is easy to build patterned OLEDs with feature sizes into the nanometer regime.
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In this paper we fabricated and succeeded to demonstrate a test panel for AMOLED on 2" glass and PET substrate. The test panel consisted of an array of 64 x 64 pixels in which OLEDs was driven by pentacene TFT. OTFTs were made of the inverted staggered structure and employed polyvinylphenol as the gate insulator and pentacene thin film as the active layer, producing the filed effect mobility of 0.3
$cm^2$ /V.sec and on/off current ratio of$10^5$ . OLEDs were composed of TPD for HTL and Alq3 for EML with 35nm thick each, generating green monochrome light. -
Polarizers with high polarizing efficiency and other advanced optical films based on Lyotropic Dichroic Dyes have been developed for LCD and other applications. The developed optical films reveal both rod-like chromophores structure in a case of positive, or O-films and disc-like one for negative, or E-film.
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We present a family of elaborate numerical models for simulation and systematic optimization of complex LCDs for demanding applications (e.g. LCD-TV). These numerical models comprise modules for solving LCD-related problems in one, two and three dimensions. The three modules feature an intuitive graphical user surface for a jump-start into modeling, a common database for a range of materials and components as well as sophisticated and proven algorithms with more than 15 years of reliable performance in the LCD-industry. Methods for obtaining data required for the modeling of key components are presented.
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Orientation of E7 liquid crystals(LCs) confined to 200 nm-diameter cylindrical cavities of Anodisc membranes are investigated by FTIR dichroism techniques. The cavity walls of the confining pores are chemically modified with different perfluorinated carboxylic acids (PCA,
$C_nF_{2n+1}$ COOH, n=3, 4, 5, 6). From the FTIR spectra of PCA treated alumina Anodsic membranes, we found the salt formation between -COOH group of PCA and Anodisc membrane. From the FTIR spectra of LC filled Anodisc membranes, we found abrupt alignment direction change of LC molecules between n=4 and 5 for 1 mM PCA treated Anodisc membranes, from parallel to perpendicular direction to the cavity walls. But 5mM PCA treated Anodisc membranes, alignment direction of LC molecules changed between n=3 and n=4, from parallel to perpendicular direction. -
The measurement of diffraction of LCOS microdisplay with various pixel size, interpixel gap, pixel height and coatings demonstrates that pixel size is the leading factor for diffraction loss, while the role of varying pixel gap is less significant comparatively. One-dimensional diffraction simulation is found to be in good agreement with the measurement. Noticeable deviation occurs when pixel size is as small as 8um.
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Microoptics has become the key technology in liquid crystal display systems due to its capabilities of miniaturization and design flexibility. We successfully demonstrate five different microoptical components for enhancing the image quality, providing better functions, increasing light efficiency, and generating 3D images in LCD applications.
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In this paper an alternative Active Matrix LCD technology is described with scalable, low cost processing. The Dual Select Diode AMLCD requires 60% lower capital investment in the array process than a-Si TFT arrays and results in 20% lower cost LCD modules. Development at several AMLCD manufacturers is in progress.
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A new dithering algorithm, "Hi-FRC", to enable full (16,777,216) color display on LCD panel with 6-bit source D-IC's is presented. The conventional FRC can display only 16,194,277 colors. In addition, The LCD panel with Hi-FRC can meet the color grayscale linearity of TCO '03 because it can improve the color shift problem.
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To get rid of cell assembly margin and have more process room of upper substrate, we developed truly COT (Color Filter On TFF Array) LCDs in that B/M (Black Matrix) as well as C/F (Color Filter) layer is located on TFT substrate. Novel B/M material is also developed for this COT structure. Difficulty in making contact hole through C/F layer was solved by making each C/F pattern isolated from others. We think this configuration will be core technology for prominent COT LCDs.
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We developed an a-Si TFT-LCD panel with integrated gate driver circuit using a standard 5-MASK process. To minimize the effect of the a-Si TFT current and LC's capacitance variation with temperature, we developed a new a-Si TFT circuit structure and minimized coupling capacitance by changing vertical architecture above gate driver circuit. Integration of gate driver circuit on glass substrate enables single chip and 3-side free panel structure in a-Si TFT-LCD of QVGA(240
$^{\ast}$ 320) resolution. And using double ASG structure the dead space of TFT-LCD panel could be further decreased. -
You, Jae-Sung;Kim, Young-Joo;Jung, Yun-Ho;Seo, Hyun-Sik;Kang, Ho-Chul;Lim, Kyong-Moon;Kim, Chang-Dong 401
Transfer characteristics of poly-Si TFTs within process window of laser energy are investigated. In terms of surface morphology and transfer characteristics, process window of laser crystallization is evaluated. While maximum mobility exists in lower edge of process window in n-channel TFTs, maximum mobility exists in higher edge of process window in p-channel TFTs. -
We have optimized the low temperature growth of microcrystalline silicon at 80
$^{\circ}C$ . This material has been used to fabricate bottom gate${\mu}c$ -Si:H TFTs by using a layer-by-layer nitrogenation process. By using this process the amorphous incubation layer can be converted into silicon nitride and leads to an increase in field effect mobility of the TFT -
Color filter is a fundamental and necessary component to make a full-color TFT-LCD, its quality intensively influence the performance of TFT-LCD in the application of Notebook Computer, Monitor and Television. Color filter in chromaticity also make an effect for human visual system and video enjoyment. Recently, mother glass size is enlarged for demand of large-size panels and new generation color .filter technology for large-size liquid crystal cell panels is also developed. Here, latest generation color filter technology in TFT-LCD will be discussed.
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We have developed nucleation control methods applicable to a zone-melting recrystallization excimer laser annealing process for poly-Si films. Ribbon-shaped Si grains of 2
${\mu}m$ -width were successfully aligned side by side by means of a comb-shaped beam, and we have successfully fabricated TFTs with channels formed in those grains. Electron mobility in the TFTs is as high as 677-$cm^2$ /Vs. -
The performance of dichroic sponge polymer dispersed liquid crystals (D-SPDLC) can be improved further by modifying the TFT diffusing reflector using a
$TiO_2$ layer. A metal-like glare was suppressed, and a wider viewing angle than previously reported was achieved. The display showed above newspaper-standard reflectivity and contrast ratio. -
In this paper, we propose a new metric called "dynamic gamma" to quantitatively evaluate the dynamic temporal response of an LC display device. The widely-used response time and corresponding 3-D bar graphs cannot fully describe the dynamic characteristics of an LC panel [1], and using response time to compare different LC panels and assessing the dynamic features of LC panels is difficult. On the other hand, the new metric MPRT mixes an LC panel's slow temporal response with its hold-type display effect. The proposed new metric, dynamic gamma, and corresponding 2-D plots, are arguably more suitable for quantitatively characterizing the dynamic characteristics of an LC panel, so comparing two LC panels becomes easy. Furthermore, dynamic gamma has the unique property that it can be used to quantify the limitations/capabilities and to assess the effectiveness of an overdrive mechanism for a particular LCD. In the paper, two LC panels using different technology are analyzed and compared using this new metric.
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Many of the problems by using the microscope are related to the fact that the eyes of the surgeon must be continually fixed to the microscope eyepieces. In this paper, we describe a development of the stereoscopic monitoring system of the stereo microscope for reduced eyestrain or operator fatigue about the long time observations of the microscope. The system consists of the stereoscopic camera part, the stereoscopic image processor device and the polarized light stereoscopic monitor. The left and right images obtained form the two CCD cameras are the same as the eyepiece images. By use of the image processor, the polarized light stereoscopic monitor displayed a real-time stereo microscope images.
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This paper proposes a new 3-D display without glasses using
$Moir\acute{e}$ system. It is possible to create a new three-dimensional expression that is different from conventional 3-Dimages. In this study we have geometrically analyzed the process by which moire takes on a three-dimensional property and validated the results of this analysis. -
The skin color of a human being is the important memory color influencing image quality for color display. Therefore, in this paper, the preferred skin color axis is defined on HSV color space by analyzing some previous research, and the preferred skin color reproduction algorithm is performed by rotating the center axis of skin distribution of an input image to the preferred skin color axis.
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Most of past image processing systems have been designed independent of image contents. Now, evolving computation power is making the "image-dependent" elegant algorithms possible to get the better image renditions on display. This paper introduces our recent approaches to quality and pleasant imaging based on image-dependent. Three typical approaches to comfortable "Sharpness", "Lightness", and "Color" renditions on display image arc presented.
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A volumetric three-dimensional (3D) display system was presented, which utilizes a rotating two-dimensional (2D) display panel of light emitting diodes (LEDs) to generate more than 10 million volume pixels (voxels) within a cylindrical volume of 165 mm in height and 292 mm in diameter. Due to persistence of vision, momentarily addressed voxel information is perceived and fused into a 3D image. Important cues for depth perception, such as binocular parallax, accommodation, convergence and motion parallax are satisfied automatically and naturally, thus it is suitable for individual or group viewing, without the need for any special visual aids.
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We report principles and results of design large FOV retinal display systems by software WinDEMOS and software for computer testing display systems TEDiS. We discuss results design head mounted and head up display. As combiner we are used volume interference recorded or synthetic HOE, and as the sours of the image high resolution transmitting or reflective liquid crystal matrixes on silicon (LCOS) or CRT.
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We developed a dynamic logic architecture which resulted better leakage current, lower power consumption and less area compared to the conventional dynamic logic structures. We demonstrated the advantage from HSPICE simulation and test chip design has been completed.
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This paper analyzes some important achievements in Ergonomics field in CRT industry. After introducing principal regulatory requirements for CRTs, including ISO 9241 and TCO standards, the paper indicates some theoretical research in ergonomics of the display devices, such as new contrast parameter for appraising the display devices and effects of environment on visual performance at the ergonomic. Then, as the pivot of this paper, some practical progress, in the ergonomics field in CRT manufacturing , are described, such as vacuum sputtering process for advanced CRTs, new developed wet process for getting the multi-coating layers on surface of the panel.
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Ko, Sung-Woo;Shin, Hyung-Cheol;Park, Byung-Gook;Lee, Jong-Duk;Jun, Pil-Goo;Kwak, Byung-Hwak;Noh, Hyung-Wook;Uh, Hyung-Soo 453
The effect of rapid thermal annealing (RTA) treatment on the growth characteristics of CNTs was investigated. We observed that Ni catalyst film was agglomerated by RTA treatment, resulting in the formation of Ni nanoparticles. The well aligned CNTs were grown from the Ni nanoparticles by plasma enhanced chemical vapor deposition (PECVD). It is shown that the size and distribution of the nanoparticles depend mainly on the annealing temperature and initial thickness of the metal layer. Also, it was found that CNTs grown through optimal RTA treatment had the more improved field emission characteristics than those of as-grown CNTs. -
Jun, Pil-Goo;Kwak, Byung-Hwak;Noh, Hyung-Wook;Lee, Soo-Myun;Uh, Hyung-Soo;Park, Sang-Sik;Ko, Sung-Woo;Cho, Euo-Sik;Lee, Jong-Duk 456
We proposed a novel triode-type carbon nanotube field emitter arrays in which extracted gate is surrounded by CNT emitters. We carried out 3-dimensional numerical calculations of electrostatic potential for the proposed CNT-FEAs using the finite element method and compared the results with those obtained from the structure of conventional CNT-FEAs. It was found that the proposed structure could reduce the turn-on voltage for electron emission and improve beam focusing. -
Han, Jae-Hee;Kim, Do-Yoon;Berdinsky, Alexander S.;Yoo, Ji-Beom;Park, Chong-Yun;Choi, Jin-Ju;Jung, Tae-Won;Han, In-Taek;Kim, Jong-Min 459
Field-emission (FE) characteristics of different photolithographically patterned carbon nanotubes (CNTs) films have been studied. The total FE current is the highest value [2.8 mA (${\sim}$ 106 mA/$cm^2$ ) at 7.5 V/${\mu}m$ ] in patterned CNTs film with the window size of 60${\mu}m$ ${\sim}$ 60${\mu}m$ and the spacing of 120${\mu}m$ . It was found that the total widow area is more important factor for the total FE current than the total window length. The contact resistance between CNTs and substrate would be a crucial factor for detachment of CNTs from the substrate. -
Kim, Do-Yoon;Yoo, Ji-Beom;Berdinsky, A.S.;Park, Chong-Yun;Han, In-Taek;Jung, Jae-Eun;Jin, Yong-Wan;Kim, Jong-Min 462
We studied the growth characteristics of carbon nanotubes which was grown from uniformly dispersed iron nanoparticles prepared from iron-acetate [Fe(II)$(CH_3COO)_2$ ]. The density of CNT was controlled from precursor concentrations. We also investigated the field emission properties of CNTs. We found that the optimization of CNT density is an important factor for field_emission properties. -
Lee, Su-Hong;Han, Jae-Hee;Lee, Tae-Young;Park, Yong-Choon;Berdinsky, A.S.;Kwan, Young-Uk;Yoo, Ji-Beom;Park, Chong-Yun 465
We presented a systematic investigation on the growth of CNTs including SWNTs on nano-catalyst-embedded particles by PECVD. For CNTs growth, the mixture of$C_2H_2$ and$NH_3$ was used. The total pressure and temperature were kept at 3.25 Torr and 650$^{\circ}C$ , respectively. Finally, we measured the field emission property from CNTs grown from nano-catalyst embedded zeolite particles in vacuum chamber (<$10^{-7}$ Torr). -
Park, Jae-Hong;Moon, Jin-San;Nam, Joong-Woo;Park, Jong-Hwan;Berdinsky, A.S.;Yoo, Ji-Beom;Lee, C.G.;Park, Chong-Yun 468
CNT pastes with different inorganic binder such as glass frit and spin on glass (SOG) were synthesized by using multi-walled nanotube (MWNT) grown by CVD. The uniformity of cathode layer after firing was enhanced and the emission current density at an applied field of 7.95V/${\mu}m$ increased from 133${\mu}A$ /$cm^2$ to 265${\mu}A$ /$cm^2$ when inorganic binder changed from glass frit to SOG. The emission properties of CNT pastes with SOG were stable and uniform although firing was carried out at relatively high temperature of 450$^{\circ}C$ under air. It is concluded that SOG is more suitable inorganic binder than glass frit for field emission application. -
We investigated field emission (FE) characteristics of multi-walled carbon nanotubes (CNTs) grown on all over patterned cathode electrode lines (CL pattern) and grown on along the central areas of the cathode lines(CL pattern). The CNTs grown on the SL pattern showed a lower threshold voltage and higher emission current than those on the CL pattern, due to the concentration of electric fields at the edges of the cathode lines. For the SL-patterned CNTs, however, the FE gradually spread out to the neighbors with time, and was instantly extinguished in some area and then slowly resumed again. Such areal- spread FE did not occur for the CL-patterned sample, leading to the stable FE together with the instant turn-on capability. It is suggested that the spread FE and instability for the SL-patterned CNTs may be related to the electrical charging on the insulator surface around the cathode line edges.
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In this paper, we describe a powerful solution for efficient LED wall calibration through the use of a quality 2D-luminance meter : the MURATest and a dedicated applicative software. The intended calibration allows adjusting individually the intensity of each LED so as to obtain a good uniformity on the module. Furthermore the intensity of each module can be adjusted one to the others so as to obtain a good uniformity on a complete display and maintain it even after module exchange for display maintenance needs.
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We report a method for simultaneous measurements of cell gap, twist angle, birefringence dispersion of liquid crystal (LC) material and alignment directions in filled reflective LC cells. The method is based on spectral measurements of the LC cell reflectivity for three orientations (
$0^{\circ},45^{\circ},90^{\circ}$ ) of the exit polarizer and may be applied for LC cells with low and high gaps. -
A CCD-based color uniformity measurement system was set up. Through measuring the two-dimensional brightness distributions of three primary colors on the screen, chromaticity coordinate distributions of combination gray can be obtained within a few seconds. This system can be widely used in the production of LCD projection.
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In order to simulate OLED evaporation process, modeling of directional distribution of the vaporized organic materials, film thickness distribution profile and pattern-mask shadow effect are required In accordance with many literatures; all of them except shadow effect modeling are studied and developed. In this paper, modeling algorithm of evaporation shadow is presented for process simulation of full-color OLED evaporating system. In OLED evaporating process the offset position of the point cell-source against the substrate rotation axis and the usage of the patterned mask are the principal causes for evaporation shadow. For geometric simulation of shadow using z-map, the film thickness profile, which is condensed on a glass substrate, is converted to the z-map data. In practical evaporation process, the glass substrate is rotated. This physical fact is solved and modeled mathematically for z-map simulation. After simulating the evaporation process, the z-map data can present the shadow-effected film thickness profile. Z-map is an efficient method in that the cross-sectional presentations of the film thickness profile and thickness distribution evaluation are easily and rapidly achieved.
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With recent experiments to add He atoms to the Ne-Xe discharge gas mixture for high luminous efficiency PDPs, we have performed simulations on a coplanar structured AC-PDP sustained in the three species He-Ne-Xe gas mixture. We found that the correct ion mobilities are essential to get the meaningful simulation results. We determined ion mobilities in the mixture gas and presented the calculated results regarding the influence of ion mobilities on discharge characteristics.
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PDP use the mixture of inert gases to generate a discharge inside display pixels. Inside of PDP, there exist highly reactive conditions in the gap between two glass panels. MgO layer and phosphor have been investigated as a function of discharge and thermal process. Impurities such as CO,
$CO_2$ , OH and$H_2O$ in discharge region may deteriorate the characteristics of PDP operation during life time. Change of impurity generation of various MgO and phosphor surfaces were measured by using x-ray photoelectron spectroscopy(XPS) and quadropole mass spectrometer (QMS). Carbon containing species such as C, CO and$CO_2$ were drastically increased on the surfaces during discharge and thermal treatment. Carbon impurities on the MgO and phosphor are the dominant factor for their instability. -
The temperature distribution of a glass plate heated in the infrared heating chamber has been investigated. Temperature of the glass panel is measured using a set of thermocouples and the optical pyrometer. Temperatures measured by thermocouples have good agreement with those by the pyrometer. The temperature uniformity of the panel is improved with wall reflectivity, which is one of the important factors to uniformly heat the panel
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In this paper, we suggest a new driving waveform for stable address discharge in AC PDP without the reduction of contrast ratio. To analyze the influence of cross-talk between discharge and non-discharge cells and verify that proposed waveform shows a stable address discharge, we measured the address discharge delay time. The proposed waveform shows the reduction of the cross-talk and concurrently the improvement of address voltage margin compared with those of selective reset waveform having one reset period in 1TV-Field..
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Oblique ion-induced secondary electron emission coefficient(
${\gamma}$ ) with low energy ..and work function${\phi}_{\omega}$ (${\theta}$ = 0 and${\theta}$ = 20) of the MgO thin film in AC-PDPs has been measured by${\gamma}$ -FIB system. The MgO thin film has been deposited from sintered material under electron beam evaporation method. The energy of$He^+$ ions used has been ranged from 50eV to 150eV. Oblique ion beam has been chosen to be 10 degree, 20 degree and 30 degree. It is found that the higher secondary electron emission coefficient(${\gamma}$ ) has been achieved by the higher oblique ion beam up to inclination angle of 30 degree than the perpendicular incident ion beam. -
ADS(Address Display period Separation) driving method has been considered to be the most appropriate driving technique for AC PDPs. However when the ADS driving method is applied to the high-resolution AC PDP, the required long addressing time often becomes a problem. In this paper, we present a new waveform for reducing the addressing time and for the stable addressing discharge. In this new waveform, a wall charge acceleration pulse is applied to the common electrode right after 80us scan time. In this way, the charge generated by the addressing discharge is accelerated to the electrodes. Experiments using the wall charge acceleration pulse showed that we could stably address an AC PDP with the scan pulses having pulse width of 1 us
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The laser absorption spectroscopy has been used for measuresurement of the xenon atoms in the resonant
$1S_4$ and metastable$1S_5$ states in coplanar AC PDP. For the purpose of improving VUV luminous efficiency and optimization of PDP cells, it is important to study behavior of excited Xe atoms in a micro-discharge cell of a coplanar AC-PDP. We measured the xenon excited density of$1S_5$ and$1S_4$ state under mixture gas of Ne-Xe(10%) with gas pressure of 350 Torr and sustaining gap distance of 150 um. -
The degradation characteristics of MgO protective layer and phosphors have been investigated in terms of the ion-induced secondary electron emission coefficient
${\gamma}$ and static margin of discharge voltages, respectively, in this experiment. The ion-induced secondary electron emission coefficients${\gamma}$ for the degraded MgO protective layer and phosphors have been studied by${\gamma}$ -focused ion beam system. The energy of Ne+ ions used is from 80 eV to 200 eV in this experiment. The degraded MgO and phosphor layers are found to have higher${\gamma}$ than that of normal ones without degradations or aged one. Also, the static margin of discharge voltages for test panels with degraded MgO protective layer and phosphors been found to be seriously decreased in comparison with those of normal ones without degradations. -
Jung, Kyu-Bong;Lee, Jun-Ho;Park, Won-Bae;Jeon, Wook;Oh, Phil-Young;Cho, Guang-Sup;Uhm, Han-Sup;Choi, Eun-Ha 522
The improvement of luminance and luminous efficiency is the one of the most important part in AC-PDPs. To achieve high luminance and luminous efficiency, high VUV emission efficiency is needed. We measured the emission spectra of vacuum ultraviolet(VUV) rays in surface discharge AC-PDP with binary and ternary gas mixtures of Ne-Xe and He-Ne-Xe. The influence of He-Ne-Xe gas-mixture ratio on excited$Xe^{\ast}$ resonant atoms and$Xe_2$ $^{\ast}$ dimers has been investigated. It is found that luminous efficiency of ternary gas mixture, He-Ne-Xe, is shown to be much higher than that of binary gas mixture of Ne-Xe. -
The ion-induced secondary electron emission coefficient
${\gamma}$ and work function for MgO thin film with$O_2$ plasma treatment has been investigated by${\gamma}$ -FIB (focused ion beam) system. The MgO thin film deposited from sintered material with$O_2$ plasma treatment is found to have higher${\gamma}$ and lower work function than those without$O_2$ plasma treatment. The energy of various ions used has been ranged from 100eV to 200eV throughout this experiment. It is found that the highest secondary electron emission coefficient${\gamma}$ has been achieved for 10 minutes of$O_2$ plasma treatment under RF power of 50W. -
The spatio-temporal variation of Infra Red(IR) emission images were obtained from a real 3-dimensional discharge space of a surface discharge type, alternating current plasma display panel(AC PDP) cell with the Ne-Xe(4%) 400Torr gas mixture. IR emissions were observed in each period of the ADS(Address and Display Separation) driving scheme with ramp initializing waveform using an images intensified charge coupled device(ICCD) camera. The roles of each electrode were identified and it was compared with the results of the discharge simulation and of the wall charge distributions measured by the electro-optic technique.
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We suggest the use of a self-assembled ultra thin organic film that can suppress the hydration of MgO protective layer in AC-PDP. We analyzed the degree of hydration of MgO layer in AC-PDP by XPS when exposed to air after vacuum deposition which proved the effectiveness of the hydration prevention. We also made PDP test panels to demonstrate the improvement in the luminance and luminous efficiency when the hydration of MgO surface is suppressed by the use of self-assembled ultra thin organic film.
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A novel ink-jet printing method was investigated for fine patterning of phosphor layer in PDP using a precision nozzle printing. A reverse emulsion method was developed for the synthesis of nano-sized phosphor powder that could be formulated in the phosphor ink. The composition of the phosphor ink including charge controlling agents, solvent, dispersant and nano-sized phosphor powder was optimized for the fine patterning of phosphor layer for high resolution PDP.
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The stress of MgO thin film, which is used as a dielectric protective layer in AC-PDP, was measured by a laser scanning method. MgO films were deposited bye-beam evaporation on glass substrates with dielectrics layer on them in various deposition temperatures ranging from room temperature to 300
$^{\circ}C$ . The compressive stress of MgO films was increased with increasing substrate temperature due to intrinsic stress accumulation, causing the densification of the films. Both firing voltage ($V_f$ ) and sustaining voltage ($V_s$ ) were reduced for the higher compressively stressed and densified films. In the other hand, another film properties such as preferred crystallographic orientation and surface roughness seemed not to influence the discharge characteristics of$V_f$ and$V_s$ significantly. -
Glass frits for dielectric layers are mostly used for screen printing process. Several additives have already been known to be well matched with lead-oxide glasses system. The use of lead oxide, however, creates environmental problems, so many recent studies on lead-free glasses compositions have been carried out. A study of the suitability between additives and lead-free glass system is needed. In this study, we have used a screen-printing method to make thick films of lead-oxide glass and lead-free glass using different additives, and analyzed and compared the transmittance of the thick films.
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For the improvements in high transmittance, one of the most important factors of transparent dielectric is pore contents and pore size. This study have investigated the effect of frit size on the transmittance of zinc-boric system with a Pb-free composition. A mixed glass paste was used for thick films, which were made by screen printing methods on a glass substrate (PD200). These dielectric layers were measured for surface roughness, pores content and transmittance. The results show that increase of pore size and content have detrimental effects on the transmittance of films compared to those found in the PbO system.
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Barrier ribs of plasma display panel (PDP) are glass matrix composite reinforced with alumina particles. Mechanical properties of the ribs are very crucial for the improvement in reliability of the panel as the ribs might fracture during transportation and service. In this study, therefore, the effects of filler type and content on the mechanical properties of the ribs were investigated. The fillers used include
$Al_2O_3$ ,$TiO_2$ ,$ZrO_2$ and fused silica. The content of the filler was changed from 0 to 40 vol.%. The mechanical properties of the ribs measured were hardness, Young's modulus, fracture toughness, and 3-point bending modulus. The fracture toughness evaluated by micro-Vicker's indentation of the composites, in general, was measured to increase with the content of the filler until the sintered density does not decrease significantly. The improvement, however, was dependent on the type of filler employed. -
We report the effect of the particle size (D50) and PSD (Particle Size Distribution) of glass frit on the transparency of transparent dielectric layer of PDP. The milling efficiency of wet milling with water was the best among the dry milling, wet milling with IPA and wet milling with water. The transparency increased with the reduction of particle size of glass frit as the milling time increased. Also the transparency changed by the PSD of glass frit. Glass frits of broad PSD showed high transparency compared with the glass frits of sharp PSD.
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We report the effect of wet ball milling conditions on the transparency of glass frit. Generally, the particle size of glass frit decreased as the milling time increased. And the transparency of glass frit changed with the particle size variation. The transparency of glass frit A increased as the milling time increased. But, the transparency of glass frit B, containing high
$B_2O_3$ decreased as the particle size decreased. It seems to be the result of chemical reaction with water and glass frit. -
In this paper, distortion of waveform in AC-PDP module has been studied. The propagation losses and interference due to coupling between the electrodes can be considered as the causes for waveform distortion. The distorted waveform has been obtained from the calculated propagation losses. The coupling between the electrodes has been measured using a proper experimental setup. This distorted waveform could account for underfiring problem in AC PDP module.
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New address electrode having separated dual electrode is suggested to reduce addressing time in ac PDP. Addressing characteristics of suggested electrode has been investigated in the test panel with high Xe partial pressure. It has been found that both the formative and jitter width of the suggested electrode is improved by 10 -20 % over the wide range of address voltage level compared with the conventional one. The dynamic margin of the panel also greatly improved. The key feature behind this type of structure is that it can extend the controllability of the wall charge distribution during the reset and address discharge without significant increase in capacitive load of address electrode.
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A shielding effectiveness of mesh screen filter of plasma display panel (PDP) has been calculated in this paper. Since the screen filter is located near the radiation source, the near field wave impedance of the radiation source, i.e., the PDP electrodes, has been considered to calculate the shielding effectiveness. The near field shielding effectiveness of screen filter at 30
${\sim}$ 300 MHz has been estimated to be more than 65${\sim}$ 80 dB. The measured shielding effectiveness of screen filter is 10${\sim}$ 50 dB at 30${\sim}$ 300 MHz[1]. The resulting discrepancy indicates that there are other EMI emission sources such as emission from PCB and cable besides the PDP electrodes. -
Symmetric closed-cell type barrier ribs of PDP were formed by capillary molding process using molds prepared by inclined UV lithography process. The effects of inclining angle of barrier ribs on the sintering shrinkage and luminance of panel were examined. The results indicate that the barrier ribs of inclined morphology affect the sintering shrinkage and luminance efficiency significantly.
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The charging tendency of
$Zn_2SiO_4:Mn^{2+}$ phosphor surface was modified in order to improve discharging characteristic of green cell in an ac-plasma display panel (ac-PDP). The Zinc-silicate ($Zn_2SiO_4:Mn^{2+}$ ) green-emitting phosphor was coated with magnesium oxide(MgO), which is viable to have positive charge on the surface. After fabricating the green cell with MgO-coated$Zn_2SiO_4:Mn^{2+}$ , the electrical and optical properties in the cell were examined. It was found that the dynamic voltage margin could be increased while the address time was reduced. It may be ascribed to the change of charging tendency of$Zn_2SiO_4:Mn^{2+}$ phosphor by MgO coating, which makes it possible to stable wall-charge accumulation. When$Zn_2SiO_4:Mn^{2+}$ phosphor was coated with 1.3wt%-MgO, the address time was reduced 1.2${\mu}s$ and the address voltage lowered 25 V without any misfiring problem, compared to those of typical$Zn_2SiO_4:Mn^{2+}$ phosphor layer. The luminescence intensity of green cell using MgO-coated phosphor layer was also improved by 10%. -
A new DCM derivative containing the phenoxazine moiety (DCPXZ) has been synthesized for use as a red fluorescent dye molecule in organic light-emitting diodes (OLEDs). The photoluminescence and electroluminescence properties of DCPXZ were examined. The maximum photoluminescence of DCPXZ in chloroform solution (
$10^{-5}$ mol) was observed at 616 nm. EL devices were fabricated with the structure ITO/PEDOT-PSS/Cu-PC(15nm)/${\alpha}$ -NPD(45nm)/$Alq_3$ :DCPXZ(30nm)/$Alq_3$ (30nm)/LiF(0.5nm)/Al. The maximum EL emission for the 2.0% DCPXZ-doped device was at 608 nm with CIE coordinates (0.57, 0.42). The EL device exhibited a maximum brightness of 15,000 cd/$m^2$ at 19.4 V and a power efficiency of 1.04 lm/W at a luminance of 100 cd/$m^2$ . -
The light-emitting properties of poly(2-triethylgermyl-1,4-phenylenevinylene) (TEG-PPV) are compared with those of the silyl-substituted PPV homologue, poly(2-trimethylsilyl-1,4phenylenevinylene) (TMS-PPV). The precursor polymer is solution-processable. After carrying out thermal elimination on the precursor polymer film, the resulting fully conjugated polymer film was found to exhibit high thermal stability in air, and absorption that is shifted to the longer wavelength region owing to the extension of the n-conjugated system. TEG-PPV exhibits efficient green light emission; the maximum PL emission of a TEG-PPV thin film was found to be at 515 nm. The HOMO and LUMO energy levels were also determined using photo-emission spectroscopy. The performance of the TEG-PPV EL device was found to be comparable to that of the TMS-PPV device.
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We report the characterization of white light emitting devices fabricated using conjugated polymer blends. Blue emissive poly[9,9-bis(4'-n-octyloxyphenyl) fluorene-2,7-diyl-co-10-(2'-ethylhexyl)phenothiazine-3,7-diyl] [poly(BOPF-co-PTZ)] and red emissive poly(2-(2'-ethylhexyloxy)-5-methoxy-1,4-phenylenevinylene) (MEH-PPV) were employed in the blends. The inefficient energy transfer between these blue and red light emitting polymers (previously deduced from the PL spectra of the blend films) enables the production of white light emission through control of the blend ratio. The PL and EL emission spectra of the blend systems were found to vary with the blend ratio. The EL devices were fabricated in the ITO/PEDOT/blend/LiF/Al configuration and white light emission was obtained for one of the tested blend ratios.
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Polyazomethine type conjugated copolymers containing phenanthridine units, poly(PZ-PTI), were synthesized by Schiff-base reaction. This new conjugated copolymer exhibited improved solubility in common organic solvents due to the presence of alkyl side chains as well as phenanthridine groups. Double layer (ITO/poly(PZ-PTI)/
$Alq_3$ /Mg) light emitting diode (LED) exhibited enhanced EL emission and efficiency compared to that of single layer (ITO/poly(PZ-PTI)/Mg) LED. With increasing the thickness of$Alq_3$ layer in double layer (ITO/poly(PZ-PTI)/$Alq_3$ /Mg) LED the emission peak gradually shifted to the single layer (ITO/$Alq_3$ /Mg) LED, confirming good hole transporting behaviour of the synthesized conjugated copolymer. -
Kim, Mi-Kyung;Lee, Jeong-Ik;Kim, Duck-Il;Oh, Ji-Young;Hwang, Chi-Sun;KoPark, Sang-He;Yang, Yong-Suk;Chu, Hye-Yong;Kim, Suk-Kyung;Hwang, Do-Hoon;Lee, Hyung-Jong 592
We have investigated the photolithographic patterning method of light emitting polymer film for polymer light emitting diodes (PLEDs). Blue light emitting polymers based on polyfluorene, which can be cured photochemically to yield an insoluble form, have been synthesized using Ni(0) mediated Yamamoto polymerization. The relationship between patterning property and several variables such as the intensity of the exposed UV light, the concentrations of additives, has been studied by using optical microscope analysis, UV/visible spectroscopy, and photoluminescence. We have successfully fabricated PLEDs composed of the patterned emissive layer and their electroluminescence property has been also investigated. In this presentation, the detailed photolithographic patterning method and its application for polymer light emitting display will be discussed. -
A novel poly(phenylene ethynylene) derivative containing cyano group as electron-transporting moiety was synthesized via Pd-catalyzed coupling reaction. The structures of the monomers and polymer were confirmed by spectroscopy. The polymer demonstrated a wide variation of solubility, optical absorption, electrical conductivity and electrochemical properties.
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Baek, Jeong-Ju;Jeong, Young-Chul;Han, Yoon-Soo;Jeong, Jeon-Woo;Kwon, Young-Hwan;Park, Lee-Soon 599
A new blue electroluminescent conjugated polymer, poly(BP-alt-BCV), was prepared by Hornor-Emmons polycondensation and used as a host polymer for the phosphorescent dopant,$(bsn)_2Ir(acac)$ . Poly(N-vinylcarbazole) (PVK), known as a blue EL material, was also used for comparison with poly(BP-alt-BCV). Electrophosphorescence of PLEDs with these dopant/host systems was investigated in terms of luminescence, efficiency, emission color, and energy transfer. -
NPB surface morphologies deposited on different temperature substrates were investigated using atomic force microscopy(AFM). It has been found that the NPB morphology turned from island morphology at high temperature(100
$^{\circ}C$ ) to grain morphology at room temperature. To characterize the effect of NPB surface morphology, the devices with the structure of Glass/ITO/NPB/$Alq_3$ /Al were fabricated using NPB films deposited at different substrate temperature and their performances were compared. -
A novel blue-green emitting aluminum complex was developed by employing 8-hydroxyquinoline as co-ligand for enhancement of electron transport and light emission abilities so that the electroluminescent (EL) devices do not need additional electron transport layer. The aluminum complex (PAlQ) of 8-hydroxyquinoline and
${\alpha}$ -pyridoin was synthesized The structure of the PAlQ was elucidated by FT-IR, UV-Vis and XPS. The PAlQ complex showed thermal stability up to 350$^{\circ}C$ under nitrogen flow by TGA. The photoluminescence (PL) was measured from solid film of the PAlQ complex on quartz substrate. The EL device was fabricated by the vacuum deposition. The device having the structure of ITO/TPD/PAlQ/Al was studied, where N,N-bis(3-methylphenyl}-N,N'-diphenyl-benzidine (TPD) was used as a hole transporting layer. The EL device emitted a blue-green light. -
Sodium salt of photoluminescent Eu-containing polyoxometalate (Eu-POM) was newly synthesized and its chemical structure and physical properties characterized. The Eu-POM was unstable outside the pH range 5.5-8.5, and a pH just over 7 gave the best yield. We have investigated the photoluminescent properties of Eu-POM with changing the reactants ratio of heteropolytungstate and
$EuCl_3{\cdot}6H_2O}$ . The Eu-POM was characterized by UV/Vis, FT-IR,$^1H$ -NMR, PL and XPS. Eu-POM emits orange light of 590nm when excited with the light of 280nm. Furthermore, we made dodecyltrimethylammonium (DDTA) salt of Eu-POM (Eu-POM/DDTA) by exchange of the counter cation. The Eu-POM/DDTA is soluble in common organic solvents, while Eu-POM is only soluble in water. And it emits reddish orange light of 625nm when excited with light of 250nm. -
We present an extremely high efficient red organic light-emitting diodes (OLEDs) using a fluorescent dye 4-(dicyanomethylene)-2-tert-butyl-6-(1,1,7,7-tetramethyljulolidyl-9-enyl)-4H-pyran (DCJTB) doped into an emitting region which consists of multiple pairs of a doped and an undoped layer. An emitting region of OLEDs composes of a tris-(8-hydroxyquinolinato) aluminum (Alq3) codoped with rubrene of 5% wt. or a mixture of Alq3 and rubrene (1:1). The luminance yield of the codoped device and the mixed device are 6.5 cd/A and 9.2 cd/A at 10 mA/
$cm^2$ , respectively. We have considerably improved the luminance yields of red OLEDs as much as${\sim}$ 90% at 10 mA/$cm^2$ compared with that of the device doped with only DCJTB. We attribute it to both the emitting assist dopant (rubrene) and the dotted-line doping structure in an emitting region of OLED. -
The approach is based on a phenomenon of lighting on electronic transient response of a PMOLED pixel. It achieves a speedy measurement because of using a compact algorithm; therefore, the method is suitable applied to production lines for examining quality of PMOLEDs panels
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In this study, a mono-chelated compound as novel blue light emitting material,
$BPh_2$ (pbi) (pbi = 2-(2-Pyridyl)benzimidazole) was synthesized Organic light emitting Diodes (OLEDs), which has a ITO/NPB(40 nm)/Boron(30 nm)/$Alq_3$ (1 nm)/Liq(3 nm)/Al(150 nm) structure, has been fabricated. The maximum brightness of the device is up to about 900 cd/$m^2$ and 0.54 cd/A at 11.5 V. The EL peaks and CIE coordinates of our OLEDs is 457 nm and (0.26, 0.29), respectively. -
Yang, Yong-Suk;Chu, Hye-Yong;Oh, Ji-Young;Lee, Jeong-Ik;Kim, Gi-Heon;KoPark, Sang-He;Hwang, Chi-Sun;Kim, Mi-Kyung;Do, Lee-Mi;Chung, Sung-Mook;Ko, Young-Wook 623
The coating and estimation of gas and moisture barriers on polymer and glass substrates are receiving very much attention in passivation of organic light emitting devices (OLEDs). In this study, the encapsulation and lifetime measurement techniques of OLEDs were presented. The degradation mechanisms of bare and encapsulated OLEDs were investigated by the visual lifetime measurement (VLM) system with the parameters such as a pixel luminance(L), a luminance rms roughness(dL), a brightness area ratio(R), an edge degradation depth(D), etc. -
Porous anodic alumina(PAA) which has arrays of nano size holes, was incorporated into organic light emitting devices. Porous anodic alumina on glass scattered the light generated from emitting layer and was decreased the waveguiding modes within the glass. An increase in the device coupling-out factor for the scattering structure is demonstrated.
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We report on the synthesis and film formation on a variety of small molecules such as
$Alq_3$ ,$Znq_2$ , and$Inq_3$ , used as light emitting material in organic light emitting diodes (OLEDs) . The organic materials are usually susceptible to environmental aging and photo-oxidation, which influences their viability for commercial utility. Here, we examine the effects of oxygen and light on these organic materials to enhance the efficiency and lifetime of OLEDs. Optical techniques - ellipsometry, photoluminescence and infrared spectroscopies- have been used to study of environmental and light induced effects on 8-hydroxyquinoline derivative metal complex small molecules thin films -
We have studied the effect of
$TiO_2$ layer deposited by RF magnetron sputtering which is used as an ultra thin hole-injection buffer layer in organic light-emitting diode (OLED). The$TiO_2$ thin film layer prevents metallic ions from diffusing from the ITO layer to the organic layers and improves the balance of hole and electron injections and the interface characteristics between the electrode and the organic layer. With 2 nm thickness of$TiO_2$ , the quantum efficiency was improved by 45 % compared to the device fabricated without the$TiO_2$ layer. -
We have synthesized a
$Eu^{2{\cdot}}$ -activated$Sr_3MgSi_2O_8$ blue phosphor and$Ba^{2{\cdot}}$ co-doped$Sr_2SiO_4$ yellow phosphor investigated an attempt to develop white LEDs by combining it with a GaN blue LED chip. Three distinct emission bands from the GaN-based LED and the ($Sr_3MgSi_2O_8$ :Eu +$Ba^{2{\cdot}}$ co-doped$Sr_2SiO_4$ :Eu) phosphor are clearly observed at 405nm, 455 nm and at around 540 nm, respectively. These three emission bands combine to give a spectrum that appears white to the naked eye. Our results show that GaN (405 nm chip)-based ($Sr_3MgSi_2O_8$ :Eu +$Ba^{2{\cdot}}$ co-doped$Sr_2SiO_4$ :Eu) exhibits a better luminous efficiency than that of the industrially available product InGaN (460 nm chip)-based YAG:Ce. -
We have synthesized SrS:Eu red phosphor by solid state method and investigated to adopt a red phosphor for LEDs. The SrS:Eu phosphor shows broad emission band at 600nm region due to f-d energy transfer of
$Eu^{2{\cdot}}$ . Our results show that the SrS:Eu red phosphor exhibits the better luminescence efficiency than that of the industrially available product SrS:Eu phosphor. -
We have investigated luminescence properties of Ln-SiAlON materials doped with
$Ce^{3+}$ . Low-energy 4f${\leftrightarrow}$ 5d transitions were observed as compared to the luminescence of this ion doped in oxidic host-lattices.$^1$ Ce-doped Y-a-SiAlON show bright long wavelength luminescence with high absorption for 305 and 455nm excitation. In our experiment, the sintering temperature of this material(1400$^{\circ}C$ ) was lower than that of normal sintering temperature (1700$^{\circ}C$ ). However, Single phase of SiAlON was not composed we observed the YAG phase. -
We have synthesized phosphor in the system CaO-
$Al_2O_3-SiO_2$ by combinatorial polymerized-complex method. The application of combinatorial synthesis and characterization of luminescent materials has been enlarged to identification and optimization in interesting new phosphor. In this study, we investigated luminescent properties of above-mentioned materials by excitation and emission spectra. In$Eu^{2+}$ activated$Ca_1Al_2Si_2O_8$ phosphor emit the blue light. -
We have synthesized some phosphors in the system MO-
$Al_2O_3-SiO_2$ (M=Sr, Ba) by combinatorial polymerized-complex method. Composition and synthetic temperature of phosphors in the liblary was screened from the emission intensities of individual samples under 365nm excitation. As we were screened the higher luminescent candidate composition (or candidate host lattice) at 365nm excitation, investigated whether good radiation was possible at the 405 or 465nm excitation by give the host lattice to be discovered more various change. From libraries about 2 systems, the compound to be expected in long wavelength among the compound to be screened are$Sr_4Al_{14}O_{25}$ ,$Sr_3Al_2O_6$ ,$SrAl_2Si_2O_8$ , and$BaAl_2Si_2O_8$ . -
The effect of excitation energy and various dopants(Eu and Ce) on the emission wavelength and intensity were investigated. According to PL spectra, SrO-
$Al_2O_3$ phosphors had wide absorption band at nUV. By substituting Ce for Eu, the emission band and excitation wavelength were shifted to shorter wavelength. Ce doped$SrAl_2O_4$ and$Sr_4Al_{14}O_{25}$ showed greenish blue(475nm) and blue(400nm), respectively. -
Trivalent cerium (
$Ce^{3+}$ ) activated yttrium aluminum garnet ($Y_3Al_5O_{12}$ , YAG) phosphor thin films were deposited on quartz glass substrates by rf magnetron sputtering. The effects of sputtering parameters and annealing condition on the luminescent properties were investigated. The sputtering parameters were$O_2$ /Ar gas ratio, rf power, and deposition time. The films were annealed at 1200$^{\circ}C$ for 5 hours in$N_2+$ vacuum atmosphere. Polycrystalline YAG:Ce thin film phosphor could be obtained with a gas ratio of$O_2$ /(Ar+$O_2$ )=0.5 after post-annealing. PL spectra excited at 450 nm showed a yellow single band at 550 nm. -
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In this paper, it was demonstrated that the organic thin film transistors with the organic gate insulators were fabricated by vapor deposition polymerization (VDP) processing. The configuration of OTFTs was a staggered-inverted top-contact structure and gate dielectric layer was deposited with 0.45
${\mu}m$ thickness. In order to form polyimide as a gate insulator, VDP process was also introduced instead of spin-coating process. Polyimide film was respectively co-deposited with different materials. One was from a 4,4'-oxydiphthalic anhydride (ODPA) and 4, 4'-oxydianiline (ODA) and the other was from 2,2-bis(3,4-dicarboxyphenyl) hexafluoropropane dianhydride (6FDA) and ODA. And it was also cured at 150$^{\circ}C$ for 1 hour followed by 200$^{\circ}C$ for 1 hour. Electrical characteristics of the organic thin-film transistors were detailed comparisons between the ODPA-ODA and the 6FDA-ODA which were used as gate insulator. -
Oligothiophene derivatives have been well-known as an p-type channel material.
$^1$ Here, we report novel oligothiophene derivative containing methylene linkage as an p-type channel material. Oligothiophene derivative containing methylene linkage BHTM was synthesized and characterized. BHTM was prepared by a palladium-catalyzed cross-coupling reaction via zinc-substituted thiophene. BHTM exhibited high thermal stability and at least one transition temperature. -
The thin-film passivation technology using the poly-para-xylylene (parylene) was applied to polymer electroluminescent devices. The fabricated device shows a good luminescent characteristic of maximum 11640 cd/
$m^2$ . The measured lifetime was reached up to 28 hours, which means the effectiveness of the passivation. Applying the parylene thin-film passivation technique, 10${\times}$ 10 passive matrix display system was implemented and obtained some still images. -
This study proposes controller with voltage-compensated drivers for producing gray-scaled pictures on passive matrix organic light emitting diodes (PMOLEDs) panels. The controller includes voltage type drivers so the output impedance of the driver is far less than that of the current-type driver. Its low output impedance provides better electron-optical properties than those of traditional current drivers. A free running clock and a group of counters are applied to the gray-scaled function so that phase lock loop (PLL) circuit can be reduced in the controller. A pre-charge function is used to enhance performance of the luminance of an active OLED pixel. As a result, distribution of the low gray level portion is achieved linear relationship with input data. In this work, the digital part of the proposed controller is implemented using FPGA chips, and analog parts are combined with a digital-analog converter (DAC) and analog switches. A still image is displayed on a
$48^{\ast}64$ PMOLEDs panel to assess the luminance performance fir the controller. Based on its cost requirement and luminance performance, the controller is qualified to join the market for driving PMOLEDs panels. -
In order to develop new yellow phosphor that emit efficiently under the 450 - 470 nm excitation range, we have synthesized a
$Eu^{2+}$ -activated$Sr_3SiO_5$ yellow phosphor and investigated an attempt to develop white LEDs by combining it with a InGaN blue LED chip (460 nm). Two distinct emission bands from the InGaN-based LED and the$Sr_3SiO_5$ :Eu phosphor are clearly observed at 460 nm and at 570 nm, respectively. These two emission bands combine to give a spectrum that appears white to the naked eye. Our results showed that InGaN (460 nm chip)-based$Sr_3SiO_5$ :Eu exhibits a better luminous efficiency than that of the industrially available product InGaN (460 nm chip)-based YAG:Ce. -
$SrGa_2S_4$ :Eu green phosphor and SrS:Eu red phosphor have been synthesized by co-precipitation method, respectively. Two sulfide phosphors were influenced by oxygen defect in host materials. Excitation spectra of these phosphors have high efficiency at the long wavelength region. And emission efficiency is increased under the excitation wavelength of 465nm. The combination of thiogallate green phosphor and sulfide red phosphor based on blue light InGaN chip has made it possible to emit white light. -
Jung, Jae-Hoon;Lim, Jong-Sun;Rhee, Jung-Soo;Kim, Hoon;Lee, Sang-Pil;Kim, Nam-Deog;Ju, Byeong-Kwon;Lee, Joo-Won;Chung, Kyu-Ha 684
We have developed multi-layer passivation films of UV-polymerized film/inorganic composite film to improve the long lifetime of passivated OLEDs for very thin flat panel applications. Preliminary lifetime to half initial luminance ($L_{o}{\sim}\;3,000\;cd/m^2$ ) of order 300 Hr is achieved on the conventional encapsulated test pixel using a passive matrix drive at room temperature; 570 Hr lifetime is achieved on a de tested multi-layer passivated 9$mm^2$ test pixel. -
Shim, Hye-Yeon;Jeong, Ji-Hoon;Kwon, Hyuk-Joo;Cho, Young-Jun;Kim, Bong-Ok;Kim, Sung-Min;Kim, Chi-Sik;Yoon, Seung-Soo;Kim, Young-Kwan 688
In this study, we synthesized a new red emitting material of a Red225 doped into$Alq_3$ (tris(8-quinolinolato)aluminum (III)) and fabricated white organic light-emitting diodes (OLEDs) with a simple device structure. With a blue emitting material of DPVBi (4,4'-bis(2,2'-diphenylvinyl)1,1'-biphenyl) that can transfer effectively both a hole and an electron, OLEDs with a narrow emission layer could be possible without a hole-blocking layer. Consequently, the driving voltage and stability of devices have been improved. The devices show the Commission Internationale d'Eclairage (CIE) chromaticity coordinates of (0.36, 0.35) at luminance of 2000 cd/$m^2$ . The luminous efficiency is about 3.5 cd/A, luminance is about 12000 cd/$m^2$ and current density is about 350 mA/$cm^2$ at 12 V, respectively. -
Fabrication of photosensitive carbon nanotubes paste and its post-treatment has been developed for high resolution with good electron emission uniformity. We report novel post-treatment techniques including rubber-rolling and multiple field emission cycling from which we could improve the field emission properties of printed carbon nanotubes. These techniques would be easily applicable to large area field emission display using paste of carbon nanotubes
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Of the emissive display technologies, field emission displays using pasted carbon nanotubes offer several advantages over other competing cathode materials such as low driving voltage, possible large-area and low-cost processes. In this study, formulation of carbon nanotube paste and its electron field emission properties are characterized. Also the effects of additive powders and surface morphology on electron emission are reported.
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The dependence of environmental gases such as Ar,
$O_2$ on the emission current from carbon nanotube emitters was examined in this study. Based on our experiments, the current density is decreased in single-wall carbon nanotubes (SWNTs), but is increased in multi-wall carbon nanotubes (MWNTs) as the vacuum level decreases from$10^{-7}$ Torr to$10^{-4}$ Torr by the inflow purging gases. The current density subsequently recovered as the vacuum level increased to$10^{-7}$ Torr when gas inflow stopped. From those results, we conclude that the MWNTs have completely different degradation characteristics in comparison to SWNTs excluding the effect of binder materials. -
This paper deals with the various sealing conditions in a vacuum and the discharge characteristics. The MgO thin film is prepared by e-beam evaporation method. Sealing process was performed in a vacuum at panel temperature of 430
$^{\circ}C$ . We find the cracks on the MgO film surface, which results in higher discharge voltage and lower luminous efficiency. The vacuum in-line sealing technology does not require additional annealing process but induces the MgO cracks because of the high temperature sealing cycle in a vacuum. Therefore we modify the vacuum in-line sealing cycle which the MgO cracks are not found and the good characteristics of plasma displays are found in higher sealing pressure at sealing temperature of 430$^{\circ}C$ . -
We have proposed on dual-drive & -emission (DDE) panel based on organic light-emitting diodes (OLEDs). The device is composed on independent operation of two OLED structures with two transparent electrodes for data signals and an intermediate reflective electrode for common scan signal. Typical device structure is ITO / organic electroluminescent layer (1) /intermediate reflective electrode / organic electroluminescent layer (2) /transparent electrode. Symmetric bright emission could be obtained by applying AlNd as the intermediate reflective electrode and
$MoO_3$ as a hole injection layer for upper device structure. The proposed panel is useful for emissive face-to-face panel exhibited for different images. -
A new design for improving the aperture ratio of bottom emission type AMOLED is investigated. In conventional, the TFT of AMOLED fabrication method is "Etch Stopper (7-mask)", so the aperture ratio is limited in 28
${\sim}$ 33% by Cs(Storage Capacitor). A high aperture ratio TFT is designed by using BCE(Back Channel Etching 5-mask) fabrication way and the aperture ratio is up to 40% shown in 2.2"AMOLED display. -
Substantially improved methods for the preparation of europium-doped yttrium oxide red phosphor with the inclusion of alkali metal halides having a general formula
$(Y_{1-x}Eu_x)_2O_3$ :MX where 0.025${\leq}$ x${\leq}$ 0.2 and MX is alkali halide in the mole ratio 0.025 to 0.6, more preferably between 0.05 to 0.2 mole, are reported. Another series of the red phosphor materials with general formula$(Y_{1-x-y}Gd_xEu_y)_2O_3$ :MX where 0.05${\leq}$ x${\leq}$ 0.40 and 0.025${\leq}$ y${\leq}$ 0.20 and MX is alkali halide in the mole ratio 0.025 to 0.5, more preferably between 0.1 to 0.2 mole, has also been presented. The inclusion of alkali halide greatly increase the luminance of the materials. The materials are very soft with fine particle size less than 100nm. The phosphorescent materials have good luminance in VUV region. -
Silica coating on ZnS particles with buffer solution has been investigated. Diluted sodium silicate in water was used as the precursor material and it was diluted in water. Sodium silicate was added drop-wise in the continuously stirred suspension of ZnS in the buffer solution at room temperature. Smooth and evenly distributed silica coated ZnS phosphors has been obtained when the pH of buffer solution was 10, the concentration of sodium silicate in water was 20 wt%, firing temperature was 500
$^{\circ}C$ . -
Highly efficient blue organic light-emitting devices (OLEDs) utilizing the idea of copper phthalocyanine (CuPc)/N,N'-bis-(1-naphthyl)-N,N'-diphenyl,1,1'-biphenyl- 4,4'-diamine (NPB) composite hole transport layer (CPHTL) have been fabricated. The effect of inserting CPHTL upon the performance of blue OLEDs with 2-methyl-9,10-di(2-naphthyl)anthracene (MADN) as the blue emitter has been investigated. Compared with the luminous efficiency of the standard blue device without CPHTL (1.33 cd/A), that of the device with 40:60 CuPc/NPB CPHTL has been increased by more than twice up to 2.96 cd/A with a Commission Internationale d'Eclairage (CIE) coordinates of(x = 0.15, y = 0.10) and a power efficiency of 1.46 lm/W (20 mA/
$cm^2$ ) at 6.39 V. The increased device efficiency is attributed to an improved balance between hole and electron currents arriving at the recombination zone. -
Closed-cell type barrier ribs such as honeycomb, SDR, inverse SDR and waffle types were produced using capillary molding process. Phosphor layers were formed by osmosis coating process on those barrier ribs. Using the rear plate with closed-cell ribs, the luminance and its efficiency was measured. The results demonstrated a significant improvement in efficiency by combining closed-cell type ribs with a new phosphor forming technology
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Nowadays, CRTs are threatened by the flat panel displays(FPD). The depth of CRTs becomes one of the most important design factor to maintain the dominated portion in the display market. The slim CRT design is introduced in this paper.
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A profitable mass production of Organic Light Emitting Diode (OLED) displays needs a new type of manufacturing equipment. We have developed a vertical In-Line machine (VES400) equipped with linear etch sources (e.g. to activate an ITO layer), standard magnetron sputter sources for ITO and metal and linear evaporation sources for the organic and metal materials. We present new results concerning the linear evaporation sources for organic materials. We have optimized the vertical thickness non uniformity for the evaporation of different organic materials and achieved deviations of less than
${\pm}$ 5 % for the vertical thickness over a substrate height of 400 mm. We will further report first results about the long term stability of the deposition rate for different organic materials using rate control.. -
Striakhilev, D.;Servati, P.;Sakariya, K.;Tao, S.;Alexander, S.;Kumar, A.;Vigranenko, Y.;Nathan, A. 746
a-Si TFTs with field-effect mobility of 1.2$cm^2$ /V-s have been fabricated on plastic substrate. Pixel circuits on plastic for AMOLED were made with the same low-temperature fabrication process. The circuits compensate for$V_T$ -shift, exhibit high output current, retain functionality and drive current level during long-time continuous operation. -
Unlike OLEDs, there is no lifetime testing procedure for TFTs. In this work, we have defined such a procedure and developed a method for the accelerated stress testing of TFT pixel circuits in a-Si AMOLED displays. The acceleration factors derived are based on high current and temperature stress, and can be used to significantly reduce the testing time required to guarantee a 20000-hour display backplane lifespan.
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Flat Panel Display (FPD) application of Television (TV) application is booming. Liquid Crystal Display (LCD) is forecasted to play a dominant role for TV application in next years. We review in this presentation LC material development for LCD TV application.
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Patterned alignment of reactive mesogens on a grating was investigated for use in phase retarders. The relative importance of the topology and the surface energy of the grating for RM alignment is discussed. Possible mechanisms of RM alignment for different grating pitches are discussed.
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Lee, Taek-Joon;Hahm, Seok-Gyu;Lee, Seung-Woo;Chae, Bok-Nam;Lee, Seong-June;Kim, Seung-Bin;Jung, Jin-Chul;Ree, Moon-Hor 766
Rubbed films of a series of poly(p-phenylene 3,6-bis(4-(n-alkyloxy)phenyloxy)pyromellitimide)s (Cn-PMDA-PDA PIs), which are well-defined brush PIs composed of two aromatic-aliphatic bristles per repeat unit of a fully rodlike backbone, were investigated in detail using atomic force microscopy (AFM), optical retardation analysis and linearly polarized infrared (IR) spectroscopy in order to elucidate their surface morphology and molecular orientation. The liquid crystal (LC) alignment behavior and the anchoring energy of LC molecules on the rubbed films were also determined. -
We report on the developed fabrication method of lanthanide-doped xerogel/porous anodic alumina structures for an image formation via the aluminum anodization, the sol-gel synthesis, and the photolithography process. The structures of europium- or terbium-doped xerogel/porous anodic alumina are also considered in view of application in electroluminescent devices.
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Kim, Kyeong-Hyeon;Lyu, Jae-Jin;Chung, Dong-Hoon;Verrall, M.;Slaney, K.;Perrett, T.;Parri, O.;Lee, Seung-Eun;Lee, Hee-Kyu 773
For high end, large area displays, all current LC modes require some degree of optical compensation to improve the front of screen viewing experience. Currently most optical films are laminated to the outside of the LCD cell, between the glass and polariser. In this paper we wish to show how it is possible to integrate the compensating optical film within a VA mode LCD cell. The paper will describe the process of making the biaxial film through the process of in-situ photopolymerisation of an aligned film of reactive mesogens in the cholesteric phase using polarised UV light. The film can be made on the colour filter array side of the LCD panel. In addition the process of fabricating a VA mode LCD containing this film will be described and the performance of this module will be presented -
Establishing and maintaining optimum lamp operating temperature is critically important in backlight systems for large area displays. The information presented in this paper is based upon work completed for a tiled 37.5" AM LCD, plus projections for a 37.5", 42" & 50" monolithic display. Due to the size of the units, a requirement for highly collimated light and a requirement for high brightness, >550 nits at the display surface, significant wattage is required which generates high heat levels in the backlight display assembly and potentially, at the display rear surface. Uniformity of illumination becomes an important element in the system design because of the large area involved.
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Uehara, Shin-Ichi;Ikeda, Naoyasu;Takanashi, Nobuaki;Iriguchi, Masao;Sugimoto, Mitsuhiro;Matsuzaki, Tadahiro;Asada, Hideki 783
We have developed a 470 x 235ppi poly-Si TFT LCD with a novel pixel arrangement, called HDDP (Horizontally Double-Density Pixels), for high-resolution 2D and 3D autostereoscopic display. 3D image quality is especially high in a lenticular-lens-equipped 3D mode because both horizontal resolution and vertical resolution are high, and because these resolutions are equal. 3D and 2D images can be displayed simultaneously in the same picture. In addition, 3D images can be displayed anywhere and 2D characters can be made to appear at different depths with perfect legibility. No switching of 2D/3D modes is necessary, and the design's thin and uncomplicated structure makes it especially suitable for mobile terminals. -
The large size and high brightness backlight system for LCD panel inspection equipment was designed, fabricated, and evaluated. The cold cathode fluorescent lamp (CCFL) instead of the hot cathode fluorescent lamp (HCFL) were used as the light source. The inverters for driving multi-lamp CCFL backlight systems were also designed and fabricated. The measured luminance of the fabricated CCFL backlight system was 20,000 cd/
$m^2$ and the uniformity of the backlight was 85%. The fabricated backlight system was successfully applied to the LCD panel inspection equipment. -
In this article, we present a method to measure precisely the performances of direct-lit CCFL backlights using a luminance meter and dedicated image analysis software. The array of CCFL tubes alone can be measured directly and the luminance of each tube can be extracted along its main dimension. So, comparison of the different tubes on the same backlight can be made easily and the performances in terms of backlight uniformity improved. The influence of the diffuser sheet can be probed in the same way and the homogeneity of the entire surface of the backlight can be automatically extracted and quantified.
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Kim, Joong-Hyun;Hwang, In-Sun;Byun, Jin-Seob;Park, Hae-Il;Kim, Hyoung-Joo;Jang, Hyeon-Yong;Kang, Seock-Hwan;Kim, Min-Gyu;Kwon, Nam-Ok;Lee, Sang-Yu;Souk, Jun-Hyung;Ko, Jae-Hyeon;Lee, Ki-Yeon;Jung, Kyeong-Taek;Kim, Dong-Woo;Ha, Hae-Soo;Heon, Min;Kim, Nam-Hun;Kim, Hyun-Sook;Kim, Geun-Young;Cho, Seog-Hyun 795
After showing 32 inch two-dimensionally integrated fluorescent lamp (TIFL) and its module at SID '04, 40 inch TIFL and its module of prototype have been developed at the first time. It is the biggest size in the world as well as has a backlight unit without BEF optical film. The luminance of TIFL is 14000 nit at 190 watt power consumption and its luminous efficacy is 51 lumen/watt. The use of TIFL simplifies backlight assembly process and removes high price optical sheets. As a result, LCD TV, used by TIFL, is rapidly going to expand its market share in the large size TV area. -
Oh, E.Y.;Baik, S.H.;Sohn, M.H.;Kim, K.D.;Hong, H.J.;Bang, J.Y.;Kwon, K.J.;Kim, M.H.;Jang, H.;Yoon, J.K.;Chung, I.J. 799
In this paper, the active backlight control technology with data processing algorithm was developed in order to improve image quality for IPS-mode LCD-TV applications. The image blinking problem caused by repeatedly abrupt change of the backlight luminance was solved by algorithms-Fba(Flexible Boundary algorithm) and Cfa(Cumulative Feedback algorithm)-and the optimized number and space of backlight dimming steps based on perception. In the IPS-mode 42" TFT-LCD panel, the dynamic contrast ratio can be more than twice the typical level by means of lower block luminance and higher white luminance. Additionally, Power consumption and LCD temperature was decreased. -
Dual Mode technology has been developed as a new technology that allows to use a self-emissive display under full sunlight conditions. The new technology connects a LCD-like remissive operation mode in sunlight to an OLED-like self-emissive operation in the dark In the recent years, the focus of development has shifted towards the possibility of full colour operation.
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Amold, A.D.;Hatwar, T.K.;Hettel, M.V.;Kane, P.J.;Miller, M.E.;Murdoch, M.J.;Spindler, J.P.;Slyke, S.A. Van;Mameno, K.;Nishikawa, R.;Omura, T.;Matsumoto, S. 808
A full-color AMOLED display with an RGBW color filter pattern has been fabricated. Displays with this format require about$^1/_2$ the power of analogous RGB displays. RGBW and RGB 2.16inch diagonal displays with average power consumptions of 180 mW and 340 mW, respectively, are demonstrated for a set of standard digital still camera images at a luminance of 100 cd/$m^2$ . In both cases, a white-emitting AMOLED is used as the light source. The higher efficiency of the RGBW format results because a large fraction of a typical image can be represented as white, and the white sub-pixel in an RGBW AMOLED display is highly efficient because of the absence of any color filter. RGBW and RGB AMOLED displays have the same color gamut and, aside from the power consumption difference, are indistinguishable. -
The molecular structure influences the thermal behavior of HTM. For OLED the glass transition temperature and evaporation temperature are critical. We report how changes in structure cause changes on both parameters. The results may be of interest for chemists when they design new molecule structures for OLED.
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Hatwar, T.K.;Spindler, J.P.;Ricks, M.L.;Young, R.H.;Cosimbescu, L.;Begley, W.J.;Slyke, S.A. Van 816
White-emitting OLEDs have been prepared that provide emission close to 6500 K color temperature (D65) with exceptional stability and high efficiency. The combination of host and dopant materials offers significant improvement for full color displays, in terms of power consumption, with minimal changes in color and efficiency with current density. These features are important for fabricating RGB and RGBW full color displays using white OLEDs with color filters. -
We present high reflective anode for top emission OLED. Anode consists of two layers, which are increasing the ability of hole injection and the reflectivity of emitted light. Thin Cr is deposited on AlNd that has a high thermal resistance and reflectivity. The current-voltage characteristics of Cr(30
${{\AA}}$ )/AlNd(1000${{\AA}}$ ) anode are poor but these of Cr(50${{\AA}}$ )/AlNd(1000${{\AA}}$ ) anode are superior to these of Cr(30${{\AA}}$ )/AlNd(1000${{\AA}}$ ) and the work function of cr(50${{\AA}}$ )/AlNd(1000${{\AA}}$ ) is higher that of Cr(30${{\AA}}$ )/AlNd(1000${{\AA}}$ ). -
Schwambera, M.;Gersdorff, M.;Reinhold, M.;Meyer, N.;Strauch, G.;Marheineke, B.;Heuken, M.;Zhou, T.X.;Ngo, T.;Brown, J.J.;Shtein, M.;Forrest, S.R. 824
High performance green$Ir(ppy)_3$ -based phosphorescent OLEDs (PHOLEDs) have been fabricated by organic vapor phase deposition ($OVPD^{TM}$ ). In addition to demonstrating both efficiency and operational device lifetime comparable to devices built by vacuum thermal evaporation, we report on the controllability and stability of the$OVPD^{TM}$ process. Specifically, run-to-run and day-to-day deposition rate reproducibility of better than 2 % for three consecutive days is demonstrated. -
Kang, Seung-Gon;Kim, Seong-Ho;Song, Seock-Cheon;Park, Won-Sang;Yi, Chung;Kim, Chi-Woo;Chung, Kyu-Ha 831
A novel transflective-type LC mode with good display performance has been developed In order to drive both transmissive and reflective modes simultaneously without any modulation of gamma in a single-gap structure, we have introduced a new design concept in the reflective region, where the capacitance is separated into liquid crystal($C_{LC}$ } and organic layer($C_{OL}$ ), playing a key role as a voltage divider in our cap-divided VA-mode. With this cap-divided method having both merits of simplifying process and good legibility, we have achieved good optical characteristics such as high contrast ratio and wide viewing angle in a single-gap homeotropic panel design. -
We report on a simple method of fabricating multimode transflective liquid crystal displays (LCDs) using the photoalignment technique. Using a self-masking process of ultraviolet light by the reflector as a photomask as well as a reflective mirror, the periodic multimode is obtained with no additional fabrication processes. Moreover, variations of the cell gap are not required for such trasflective LCDs
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We present a fast-switching electro-optical device based on flexoelectro-optic effect in short pitch cholesterics oriented in uniform lying helix texture. The device has two operating modes: amplitude and phase modulation mode. The amplitude modulation mode is a fast in-plane switching of the device optic axis that enables to achieve a high percent of modulation of the transmitted light intensity whereas the phase mode gives a continuous change of the refractive index and thus of the phase shift of the transmitted light. By using a small concentration of diacrylate monomer and selecting the illumination conditions we have been able to create a inhomogeneous polymeric network mostly localized at both substrate surfaces and stabilize the two switching modes.
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Lim, C.S.;Lee, J.H.;Choi, H.C.;Oh, C.H.;Yeo, S.D.;Lee, Seung-Eun;Jin, Min-Ok;Kang, Doo-Jin;Klasen-Memmer, M.;Tarumi, K. 843
For the fast growing Liquid Crystal Display (LCD) TV market, it is essential to make the LCD panels to show moving images without any visual difficulties such as blurring or tailing. Owing to reduction of the cell gap and the improved Liquid Crystal (LC) mixtures with low viscosity, it is possible that our S-IPS TFT-LCDs feature a response time (R/T) as fast as 1-frame time (16ms) for a white-black operation and less than a 16rns in all gray levels without Over Driving Circuit (ODC) technology. Currently, mass production of the large size IPS panels with high speed has been successfully achieved. In order to achieve faster response time, new LC mixtures have been developed, optimizing the physical properties of rotational viscosity (${\gamma}$ 1) and elastic constants (Kii). Also, the LC mixtures with high elastic constant allow us to increase the cell gap. In this paper, realization of fast switching time in IPS mode with optimized '${\gamma}$ 1/Kii' parameter in the LC mixtures forms the core of this paper. -
We studied a low density 8CB liquid crystal-hydrophobic aerosil dispersions imbedded in submicron-size cylindrical pores. The nanosize spherical aerosil particles are adsorbed at the pore wall and hinder the planar anchoring. The adsorption is temperature dependent, and an axial to radial molecular configuration transition occurs within the cylindrical pores.
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Lee, Chun-Gyoo;Lee, Sang-Jo;Cho, Sung-Hee;Chi, Eung-Joon;Lee, Byung-Gon;Jeon, Sang-Ho;Ahn, Sang-Hyuck;Hong, Su-Bong;Choe, Deok-Hyeon 851
By approaching the counter electrode to the CNT emitter, remarkable reduction of the cathode operating voltage has been accomplished in the under-gate CNT cathode structure. The peak emission current density of 2.5 ms/$cm^2$ , which is sufficient for high brightness CNT field emission display, was obtained at the cathode-to-gate voltage of 57 V when the CNT-to-counter electrode gap was 2.2${\mu}m$ . The gate current was less than 10 % of the anode current. The CNT cathode with low driving voltage can help the cost-effective field emission display implemented. -
The Japanese National Project "Carbon Nanotube FED" is developing a high image-quality and low power-consumption field emission display (FED) by applying carbon nanotube (CNT) to the electron source. A uniform electron source with a flat-film CNTs and fine structure triodes Fir suppressing the deviation of emission is required. For realizing an FED panel, it is also necessary to develop the glass-bulb technologies for vacuum sealing, and display technologies for driving the panel by circuit electronic and for evaluating the picture quality by measuring. By achieving these technologies, an FED compatible with conventional Cathode Ray Tubes (CRTs) will be realized.
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Uemura, Sashiro;Yotani, Junko;Nagasako, Takeshi;Kurachi, Hiroyuki;Yamada, Hiromu;Ezaki, Tomotaka;Maesoba, Tsuyoshi;Nakao, Takehiro;Ito, Masaaki;Saito, Yahachi;Yumura, Motoo 860
Field emission display(FED) using carbon nanotubes (CNT) as field emitters is expected to large-area panels with high luminance and low power consumption. In order to perform the uniform luminance with low driving voltage, we introduced a new electrode to apply higher electric potential over the CNT cathode in 2003.[1] In the study, we described the luminance uniformity of the panel and the improvement of emission uniformity by increasing the emission-site density. The luminance uniformity of the several ideal dots which were selected over the display area in the panel was 2.8%. [2] The CNT cathode was irradiated by excimer-laser, which was effective to improve emission uniformity and lower driving voltage. A prototype of CNT-FED character display was performed for middle size message displays. The prototype panel had 48 x 480-dots and the resolution was 1-mm. The panel realized high luminance at low power consumption. It will be important characteristics for legible and ubiquitous displays. [3] -
Kwon, Sang-Jik;Shon, Byeong-Kyoo;Chung, Hak-June;Lee, Sang-Heon;Choi, Hyung-Wook;Lee, Jong-Duk;Lee, Chun-Gyoo 866
A carbon nanotube field emission display(CNT FED) panel with a 2 inch diagonal size was fabricated by using a screen printing of a prepared photo-sensitive CNT paste and vacuum in-line sealing technology. After a surface treatment of the patterned CNT, only the carbon nanotube tips are uniformly exposed on the surface. The diameter of the exposed CNTs are usually about 20nm. The sealing temperature of the panel was around 390$^{\circ}C$ and the vacuum level was obtained with$1.4{\times}10^{-5}$ torr at the sealing. The field emission properties of the diode type CNT FED panel were characterized Now, we are developing a triode type CNT FED with a self-aligned gate-emitter structure. -
New Oligothiophene derivatives having liquid crystalline property have been designed, synthesized and characterized. New oligothiophene derivatives were prepared by a palladium-catalyzed cross-coupling reaction via zinc-substituted thiophene. The structures of materials were characterized by various spectroscopies. The new obtained oligothiophene derivatives showed high thermal stability above 300
$^{\circ}C$ and exhibited several transition temperatures, evidence of mesophase. In field-effect transistors, a charge carrier mobility of 1.9 x$10^{-2}$ $cm^2$ /Vs was observed. -
A method of improving device performance of OTFT was investigated. The mobility of device is more than 0.51
$cm^2$ /Vs and$I_{on}/I_{off}$ is higher than$10^6$ . An Active-matrix LCD driven by OTFT was fabricated. The resolution of this panel is 64${\times}$ 128 pixels and the pixel size is 550${\mu}m$ ${\times}$ 550${\mu}m$ . -
Jin, Sung-Hun;Jung, Keum-Dong;Shin, Hyung-Chul;Park, Byung-Gook;Lee, Jong-Duk;Yi, Sang-Min;Chu, Chong-Nam 881
The robust and large-area applicable metal shadow masks with a high aspect ratio more than 20 are fabricated by a combination of micro-electro-discharge machining (${\mu}$ -EDM) and electro chemical etching (ECE). After defining S/D contacts using a 100${\mu}m$ thick stainless steel shadow mask, the top-contact pentacene TFTs with channel length of 5${\mu}m$ showed routinely the results of mobility of 0.498${\pm}$ 0.05$cm^2$ /Vsec, current on/off ratio of 1.6${times}$ $10^5$ , and threshold voltage of 0 V. The straightly defined atomic force microscopy (AFM) images of channel area demonstrated that shadow effects caused by the S/D electrode deposition were negligible. The fabricated pentacene TFTs have an average channel length of 5${\pm}$ 0.25${\mu}m$ . -
We have prepared and investigated the properties of photoinitiator-free photosensitive polyimide gate insulatos for organic thin-film transistors (OTFTs). The precursor was prepared from a dianhydride, 3,3',4,4'-Benzophenone tetracarboxylic dianhydride (BTDA) and novel aromatic diamine, 7-(3,5-diaminobenzoyloxy) coumarine (DA-CM). Photo-patternability of the polyimide precursor film and surface morphology of the films before and after photo-patterning process were investigated and negative pattern with a resolution of 50
${\mu}m$ was obtained nicely. In addition, we have fabricated OTFTs with pentacene and photosensitive polyimide as a semiconductor and a gate insulator; respectively. According to the device geometry, the${\mu}$ , current modulation ratio and subthreshold swing of the devices were around 0.2${\sim}$ 0.4$cm^2$ /Vs, more than$10^5$ and around 3${\sim}$ 5 V/dec, respectively. -
We developed a high performance bottom contact, organic thin-film transistor (OTFT) array on plastic using a self-organized process. The effect of OTS treatment on the PVP gate insulator for the performance of OTFT on plastic has been studied The OTFT without OTS exhibited a field-effect mobility of 0.1
$cm^2$ /Vs on/off current ratio of >$10^7$ . On the other hand, OTFT with OTS, exhibited a field-effect mobility of 1.3$cm^2$ /Vs and on/off current ratio of>$10^8$ . -
We propose configurations for a transflective in-plane switching (IPS) cell using muti-domain structures. Usually, the cell configurations for a transflective liquid crystal(LC) cell have a complicated structure, because retardation change of transmissive part and reflective part are not same. The transflective LC cell should have two configurations for each part, such as a multi-cell gap structure. With the ion-beam alignment and the horizontal switching LC cell, a simple structure for a transflective LC cell is proposed. The configuration only adopts one cell gap structure, which may help the enhancement of a yield. Their original optical properties in conventional transmissive and reflective type IPS liquid crystal dispaly(LCD) are kept, it shows the wide-viewing angle and the good wavelength dispersion characteristics.
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Hahm, Seok-Gyu;Lee, Taek-Joon;Lee, Seung-Woo;Yoon, Jin-Hwan;Kim, Gha-Hee;Chang, Tai-Hyun;Ree, Moon-Hor 899
The molecular reorientations and surface morphologies of rubbed films formed from atactic polystyrene (PS) samples with various molecular weights were investigated in detail. Previously unknown surface topography features were newly discovered in rubbed films, depending on molecular weights: submicroscale groove-like meandering structures composed of fine-grooves like pebbles in tens nanometers are present, oriented perpendicular to the rubbing direction. The vinyl main chains, however, were preferentially reoriented along the rubbing direction and the planes of the phenyl side groups were preferentially reoriented perpendicular to the rubbing direction with para-directions that were positioned nearly normal to the film plane. Nematic liquid crystal (LC) molecules were found to always align on the rubbed PS surfaces along the orientation direction of the submicroscale grooves generated by rubbing. -
A
${\pi}$ cell is initially in splay state. Before driving a${\pi}$ cell, transition from splay to bend state is always necessary which originates from nucleation. We propose a novel technique to make bend transition fast and effectively by forming transition cores around the pixels with the technique of multi-domain alignment, where domain boundaries play a crucial role in splay to bend transition. This noble technique enables the splay to bend transition to occur within less than 2 seconds with a low applied voltage. -
The method of holographic building of moving bulk scene that based on the acoustooptical interaction principles is discussed. Some results of numcrical simulation of bulk image process reconstruction are given.
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This paper discusses on new two LCD technologies featured by the fast electro-optic response:one is polymer-stabilized FLCDs that exhibit V-shaped electro-optic (EO) switching called PSV-mode FLCDs with response time of 400
${\mu}$ s; and the other is TN-mode LCDs that exhibit a frequency modulation response (called PM-TN LCDs)and a peculiar sensitivity to the high frequency component of driving voltage waveforms resulting in a short decay time constant of 5ms and an enhancement in the over-driving that yields short response time of 1ms between two gray levels. -
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The Field Emission Display is potentially an excellent display with high brightness and low power consumption with wide viewing angle but more work is still needed in order to identify the ideal electron emitter for such displays. This paper will review the work that we have carried out in Cambridge aver the past couple of years on optimisation of Carbon nanotubes for use as the cold cathode emitters that are possible candidates as the electron sources in second generation FEDs.
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Song, Yoon-Ho;Kim, Kwang-Bok;Hwang, Chi-Sun;Lee, Sun-Hee;Park, Dong-Jin;Lee, Jin-Ho;Kang, Kwang-Yong;Hur, Ji-Ho;Jang, Jin 923
Active-matrix field emission display (AMFED) based on carbon nanotube (CNT) emitter and amorphous silicon thin-film transistor (a-Si TFT) is reviewed. The AMFED pixels consisted of a high-voltage a-Si TFT and mesh-gated CNT emitters. The developed AMFED panel showed a high performance with a driving voltage of below 15 V. The low-cost and large-area AMFED approach with a metal mesh technology will be discussed. -
We report on a new type of a flat and thin display with a secondary emission electron source. In this display device electrons are multiplied between two secondary emission plates under a high frequency electric field. This principle has a few important advantages over a field emission display: the emission comes from flat plates, which reduces the life-time problems of ion bombardment of field emitter tips. Furthermore, the electron emission is space charge limited which gives a uniform electron distribution. The electrons are extracted from the source and accelerated to a phosphor screen to generate light. Gray levels are made by pulse width modulation.
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We investigated a great number of polymer materials. The parameters affecting on its emission properties (namely, film thickness, temperature of polymer preparation. metal substrates and so on) were studied. We observed that emission distributed overfull polymer surface, with current densities up to several hundreds
${\mu}A/cm^2$ . Some polymer samples have shown high current emission properties up to 50${\mu}A$ in DC and more then 1.5 mA in sinusoidal regimes. -
We have studied several light guide concepts for light-valve projection engines. The aim of the light guide is to replace the array of lenses and mirrors in conventional transmission-type projection engines. Volume, cost and weight can be reduced, at a similar or better performance level. Results of a first prototype are discussed.
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In this study, we report simulation results of single-panel LCOS (liquid crystal on silicon). Reflective LCOS microdisplays are widely used in various projection and near-eye application. For one panel system, liquid crystal response time is an important variable. The panel must switch fast enough to support the display of Field color sequential with high field rates. In order to have fast response and good contrast, a vertical alignment (VA) cell was used in this study. With suitable selection on LC parameters like temperature, viscosity, elastic constant and birefringence, it is possible to get response time of around 2ms from a 2.0 um-thick vertical alignment cell. This result also indicates an ease of production control on 2.0 um cells than 1.0 um cells.
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We report the laser scanning display as an emerging technology. We show demonstration system of laser TV, Video image is made by using a high speed MEMS scanning mirror and a direct-modulated red diode laser. We designed and fabricated MEMS scanning mirror. The first demonstration system showed a NTSC-resolution video image with the image size of 5 inches. The successful development of compact laser TV will open a new area of home application of the laser light.
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The discusses of this study is that we combined the systems with a new type of LCOS optical engine and the latest color management of LMS to measure the distribution of illuminance, chromaticity and Contrast on the big size of the screen and we will focus on the distribution of temperature at the surface of the PS converter under the heat to evaluate the effectiveness of the heat dissipated faculty of the optical engine system. It will support that we design and fabricate the optics devices and optical engines.
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We report the recent reliability test results of SpatiaLight's liquid crystal on Silicon (LCOS) microdisplays. Two different types of reliability tests have been performed: 1) thermal and 2) thermal with high intensity UV light. Various important device parameters were regularly monitored including the contrast ratio, color uniformity, and switching time. The test data shows that there are no degradations that fail the pass criteria. Lifetime estimations are given from the test data.
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Kwon, Jang-Yeon;Cho, Hans-S;Kim, Do-Young;Park, Kyung-Bae;Jung, Ji-Sim;Park, Young-Soo;Lee, Min-Chul;Han, Min-Koo;Noguchi, Takashi 957
In order to realize high performance thin film transistor (TFT) on plastic substrate, Si film was deposited on plastic substrate at 170$^{\circ}C$ by using inductivity coupled plasma chemical vapor deposition (ICPCVD). Hydrogen concentration in as-deposited Si film was 3.8% which is much lower than that in film prepared by using conventional plasma enhanced chemical vapor deposition (PECVD). Si film was deposited as micro crystalline phase rather than amorphous phase even at 170$^{\circ}C$ because of high density plasma. By step-by-step Excimer laser annealing, dehydrogenation and recrystallization of Si film were carried out simultaneously. With step-by-step annealing and optimization of underlayer structure, it has succeeded to achieve large grain size of 300nm by using ICPCVD. Base on these results, poly-Si TFT was fabricated on plastic substrate successfully, and it is sufficient to drive pixels of OLEDs, as well as LCDs. -
Cho, Hans-S;Jung, Ji-Sim;Kim, Do-Young;Park, Young-Soo;Park, Kyung-Bae;Kwon, Jang-Yeon;Noguchi, Takashi 962
In this work, thin films of amorphous silicon (a-Si) were formed on plastic substrates by sputtering deposition and crystallized using excimer laser irradiation. As the entire process is conducted at room temperature, and the laser irradiation-induced heating is confined to the thin film, the plastic substrate is not subjected to thermal stresses. The microstructure resulting from the laser irradiation was dependent on the laser irradiation energy density and the composition of the underlying buffer layers. It was found that a layer of AlN deposited as a buffer between the plastic and the a-Si film increased the endurance of the a-Si film under laser irradiation, and resulted in polycrystalline Si grains up to 100nm in diameter. -
Electrophoretic display has recently stimulated tremendous interest due to potential commercialization in the filed of information displays including e-books, e-newspapers, and other low-power portable displays. A new transparent soft mold press (TSMP) process developed in this study was found to give a good electrophoretic display panel with prepatterned micropools for the filling of charged particle slurry. It was also found that charged
$TiO_2$ particles with 74.09 mV of zeta potential and 3.11${\times}$ $10^{-5}$ $cm^2$ /Vs of mobility were successfully prepared. -
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We report the fabrication of flexible plastic ITO substrates and the measurement of oxidant permeation through the substrates. The plastic ITO substrates are composed of multiple organic and inorganic thin films. The organic thin films are deposited by vapor polymerization and the inorganic films are deposited by ion beam sputtering. In order to estimate the oxidant permeation rate, the pure Ca film is formed on the substrates and the amount of CaO produced by the oxidation of Ca is measured.
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According to thin and light form-factor and additional function of today's electronic devices, it is required to decrease the pattern pitch of FPC. The high density demand is more and more important trend especially, for small size LCD module. Based on this requirement, the manufacturing process is advancing from subtractive method to super subtractive method.
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Moon, Jin-San;Park, Jae-Hong;Han, Jae-Hee;Berdinsky, Alexander S.;Nam, Jae-Do;Lee, Dae-Hoi;Yoo, Ji-Beom 978
We report the preparation and properties of polymer paste solutions with CNTs using conventional paste forming process. Electrospinning has been used for the fabrication of nano-fiber composite. In this process, dispersion of CNTs is very important matter. So, we emphasize the necessity of dispersion of CNTs in the solution and investigate effects of process parameters of electrospinning. The advantage of simple electrospinning process will be discussed.. -
Ryu, Beyong-Hwan;Park, Han-Sung;Byun, Jong-Hoon;Choi, Young-Min;Kong, Ki-Jeong;Lee, Jeong-O;Chang, Hyun-Ju 981
We have studied a printability of synthesized silver nano solon ITO glass substrate. The highly concentrated polymeric dispersant-assisted silver nano sol was prepared by variation of molecular weight and control of initial nucleation and growth of silver nanoparticles, to achive dispersion stability and controlling the size of silver nanoparticles. The synthesized silver nano-sol was tested for printability to explore the possibility of micro-electrodes patterning on ITO glass substrate. The silver micro-electrode with 50${\sim}100{\mu}m$ line width was formed on ITO glass substrate. -
A plastic substrate for flexible display is developed. The gas barrier property in the substrate is improved through depositing metal and metal oxide multi layer on plastic film by PVD process. The metal/metal-oxide multiplayer on plastic film shows excellent gas barrier property and optical property.
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In the present investigation, we tried AR coating simulation by using the "Essential Macleod optical coating design and analysis" program. After various run of the program we selected appropriate materials which have specific refractive indices and for that thickness was optimized to get the low reflectance. By comparing the simulated results for the different materials,we found that
$SiO_2$ and TiN are the appropriate materials for this Flat panel device (FPD) application. Thin films of these materials were deposited using RF magnetron sputtering and Inductively Coupled Plasma Chemical Vapour Deposition (ICPCVD) methods on Polyethyleneterephthalate (PET) substrates. Spectroscopic ellipsometer (SE MF-1000) and UV-Vis spectrophotometer (SCINCO) were used for the optical characterization. The obtained experimental results are in good agreement with the simulation results. -
Jung, Sang-Kooun;Kim, Hong-Tak;Lee, Do-Kyung;Cho, Yong;Park, Lee-Soon;Park, Duck-Kyu;Sohn, Sang-Ho 992
In this study, we have grown indium tin oxide (ITO) thin films by using a low-frequency (60${\sim}$ 300 Hz) magnetron sputtering method and investigated characteristics of ITO thin films deposited on polyethersulfone substrates. The experimental results show that the films have good qualities in surface morphology, transmittance, and electrical conduction. -
In this study, we tested parylene as the passivation layer for flexible organic light emitting diodes (FOLEDs).Parylene as passivtion layer has several advantages which are good optical transparent and low moisture penetration. For more an effective passivation of FOLEDs, we suggest hybrid passivation layer with parylene and silicon oxide. We compared electrical properties and stability of the device with and without passivation layer. The lifetime of FOLED with hybrid passivation layer was increased over three times than that of non-passivated of FOLED.
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We propose and simulate a new integrated DAC analog buffer composed of only p-type poly-Si TFTs in AMLCD and AMOLED. Proposed circuit employs a voltage level shifter which
$V_{OUT}$ has a linear functional relation to$V_{IN}$ . The proposed scheme enables to allow a constant$V_{GS}$ of buffer transistor so that the charging speed of pixel data address is improved. -
We have fabricated poly-Si TFTs at 170
$^{\circ}C$ using inductively coupled plasma chemical vapor deposition (ICP-CVD) and excimer laser annealing (ELA). A Poly-Si film with large grains exceeding 5000${\AA}$ and a$SiO_2$ film with high breakdown field are deposited by ICP-CVD. A high mobility exceeding 100$cm^2$ /Vs with a low sub-threshold swing of 0.76V/dec was obtained. -
We report crystallization of a-Si using XeCl excimer laser annealing [1] on the plastic substrate. We tried to obtain higher crystallinity as the effect of
$CeO_2$ seed layer patterned. Also, we tried to control the direction of crystallization growth of silicon layer for lateral growth as the type of$CeO_2$ pattern. This crystallization method plays an important role in low temperature poly-Si (LTPS) [2] process and flexible display. -
In this paper, we present a new DC-DC converter for gate driver circuit in low temperature poly-Si TFT technology. It is composed of a newly developed charge pump circuit and a regulator circuit. When the input voltage is 5V, the efficiency of a positive charge pump used in the DC-DC converter and that of a negative charge pump is 69.0% and 57.1%, respectively. The output voltage of DC-DC converter varies 200mV when the target voltages of DC-DC converter are 9V, -6V and the threshold voltage of TFTs varies
${\pm}$ 0.5V. -
We proposed a new cross-coupled level shifter circuit using low temperature poly-Si(LTPS) TFT. The proposed level shifter can operate on low input voltage in spite of low mobility and widely varying high threshold voltage of LTPS TFT. Also, the proposed level shifter operates at high frequency and reduces power consumption for having fast rising and falling time and shortening period flowing short-circuit currents.
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High performance p-ch poly-Si TFTs with excellent stability were developed. By using a frequency doubled DPSS CW laser, the a-Si on glass could be crystallized into one dimensional single crystalline silicon named as a sequential lateral crystallization (SLC) region. We fabricated p-ch TFTs on SLC region and the typical characteristic values of the TFTs were
$u_{fe}$ = 180$cm^2$ /Vs,$V_{th}$ = -3 V, S.S. = 0.5 V/dec, and$I_{off}$ = 1 pA/um@$V_d$ = -10V. It is found that the TFTs are very stable after bias stresses such as negative and positive gate biases, hot carrier bias and high current bias. These results indicate that the poly-Si in SLC region is suitable for system on glass (SOG) application. -
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We have developed the five mask
$PMOS^1$ and the six mask CMOS process architecture for poly-Si TFT. In order to have a competitive process with that for a-Si TFT, the simple co-planar electrode structure whose data line electrode and pixel electrode are on the same plane was adopted. In addition, RGB + White four color$technology^2$ were applied to achieve high aperture ratio and transmittance. Using the aforementioned process architecture and four color technology, 2.0 inch qCIF transmissive micro-reflectance (TMR) device was successfully fabricated. -
In this paper, we have fabricated pentacene thin film transistors (TFTs) using polyvinylphenol (PVP) copolymer and cross-linked PVP as gate insulator on glass and plastic (PET) substrate. Depending on the density of PVP and cross-link material the performance has been changed. We obtained the best device performance with the mobility of 0.32cm2/V
${\cdot}$ sec and the on/off current ratio of 1.19${\times}$ 106 for the case of 10wt% PVP copolymer mixed with 5wt% poly (melamine-co-formaldehyde). Additionally using pentacene TFTs with the above PVP gate insulator, we fabricated the integrated circuits including inverter which produced the gain of 9.7. -
Kim, Jong-Moo;Lee, Joo-Won;Kim, Young-Min;Park, Jung-Soo;Kim, Jai-Kyeong;Ju, Byeong-Kwon;Oh, Myung-Hwan;Kim, Jong-Seung;Jang, Jin 1030
We herewith report for the effect of dielectric surface modification on the electrical characteristics of organic thin-film transistors (OTFTs). The kist-jm-1 as an organic molecule for the surface modification is deposited onto the surface of zirconium oxide ($ZrO_2$ ) gate dielectric layer. The OTFTs are elaborated on the flexible plastic substrates through 4-level mask process to yield a simple fabrication process. In this work, we also have examined the dependence of electrical performance on the interface surface state of gate dielectric/pentacene, which may be modified by chemical properties in the gate dielectric surface. -
In this paper we fabricated a test panel for AMOLED on glass and PET substrate. The test panel consisted of the various size of OTFTs and OLEDs and the current driving capability of OTFTs for OLEDs has been investigated. OTFTs were made of the inverted staggered structure and employed polyvinylphenol (PVP) as the gate insulator and pentacene thin film as the active layer. The OTFTs produced the filed effect mobility of 0.3
$cm^2$ /V.sec and on/off current ratio of$10^5$ . OLEDs consisted of TPD for HTL and Alq3 for EML with 35nm thick, generating green monochrome light. We found that OTFT with channel length of 70${\mu}m$ and channel width of over 3.5mm provided the sufficient current to OLED to generate the luminescence of 0.3Cd/$m^2$ . -
We developed a new photoresist which was composed of polyaniline, uv-curing agent, N-methyl-2- pyrrolidine (NMP) and N-Butyl alcohol (BuOH) as solution. The photoresist is characterized by the capability of being developed in water. We successfully patterned pentacene thin film, which was vulnerable to organic solvent and thus could not be patterned by the conventional photolithography process, with the water soluble photoresist and the minimum feature size was found to be 2um.
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As time goes by, the market demand increases and each LCD panel manufacturing company makes every effort to produce more panels in a limited time. It is necessary to reduce the cost and time of production for the improvement of productivity in manufacturing companies. The increased speed of thin films growth used in the TFT process brings improvement of productivity but it is also accompanied by a drop in display quality due to a characteristic change of the thin film. So in our dissertation, we deal with the increased speed of a-Si layer growth and the proportioned a drop in characteristic quality. We discuss a drop in display quality by a characteristic change of a-Si layer and we propose a counter-plan through panel design improvement. We have already applied our plan to the 15" XGA panel and confirmed the improved result.
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In this work, the characteristics of organic thin film transistors (OTFTs) with self-assembled monolayers (SAMs) on polymeric gate insulator have been investigated. The SAMs were formed using atomic layer deposition (ALD) method onto gate insulator. Upon the investigations, it was observed that SAMs modify the wettability of polymeric insulator and influence the growth of subsequent organic semiconductor, and thereby, electric conductivity and roughness of the pentacene film are improved.
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Performances of organic thin film transistors (OTFTs) can be detrimentally affected by the state of the gate dielectric. Because of the bad stability of polymers, OTFTs with polymer gate dielectrics often provide abnormal characteristics. In this study, we report the condensation effect of the polymer gate dielectric layer. For the observations of the effect of the condensation, the spin-coated polymer layers with various deposition conditions were fabricated and left under low vacuum condition for several days. It is observed that the thickness of polymer layer and the electrical characteristic of OTFTs vary with the condensation time.
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Kim, J.L.;Lee, C.H.;Park, S.Y.;Yoo, S.W.;Oh, J.H.;Lee, S.H.;Chai, C.C.;Park, C.W.;Ban, B.S.;Ahn, S.H.;Hong, M.P.;Chung, K.H.;Lim, S.K.;Kim, K.H.;Souk, J.H. 1049
In general, contrary to the CRTs with impulsive emission, liquid crystal displays have motion artifacts such as blurring. ghost image, decrease of dynamic CR(contrast ratio), and stroboscopic motion due to hold type driving method. In this paper, to improve motion picture quality of LCDs. impulsive driving method of black data insertion was applied to the OCB mode which is well known for its fast LC response time and wide viewing angle properties. Subject evaluation was carried out with CRT, TN, SIPS(Super IPS). and impulsive driving OCB. Moving picture image quality near CRT was obtained in impulsive OCB driving mode -
Chunghwa Picture Tubes, LTD. (CPT) has developed a Novel TFT-LCD Driving Techniquel. This new technique is developed in combination with other state-of-the-art image processing solutions such as image compression / decompression, motion detection, and noise reduction. By applying the Novel Driving Technique to the high resolution TFT-LCD, it was found that the response time can be effectively reduced with a lower overall system cost by smaller frame memory requirement, lower EMI by less memory band-width. Likewise, higher display quality can also be achieved in that the unexpected noises generated by over-drive can be eliminated. The Novel TFT-LCD Driving Technique has been successfully implemented to the 30 inch WXGA (1280
${\times}$ 768) resolution TFT LCD commercial TV module. It was found that the quality of moving picture was better improved compared with that of the conventional fast response driving method. -
Recently, According to companies of TFT LCD are making large sized products more and more. In the vortex of Products with a monitor and LCD TV is applied in a technique of a high viewing angle(FFS, IPS, VA). Also, as a high luminance, high speed response time, high degree of a color purity, and so on are continuing to develop a high performance, it is necessary to improve a specific character of high luminance that apply to LCD TV as a LCD BLU. Because a LCD panel for TV usually has a lower resolution that compare to a monitor, the structure of present backlight system can't put out its power even though it has a merit in transmission. Therefore, the examination of improvement about the high luminance direct typed BLU for LCD TV that presupposes several uses of CCFL(Cold Cathode Fluorescent Lamp) or EEFL(External Electrode Fluorescent Lamp)is actively being progressed. Although it is necessary to increase the number of lamps for applying high performance by the direct type, in this case, because we can design the character of luminance for adoption of high performance. We can satisfy with a level of luminance for LCD TV. Accordingly, we analyzed a change of the number of CCFL, mechanical and optical character to produce the direct typed backlight in 32inches spec. Consequently, we achieved luminance of 6597nit,which was including polarization film, and secured the standard for LCD TV.
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We have analyzed the cause of black "mura" and measured it in prism light guide plate(LGP). Properties of components used in a backlight uint(BLU) have changed by simulation tool. We get major factor of black "mura" for improvement in prism LGP. For the improvement of black "mura", removal of brightness "mura" at input light part must precede preferentially because of reflection characteristic of the prism LGP. Removal of brightness "mura" is improved by hanging of input light part in LGP and dispersion treatment.
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New diffuser film for LCD backlight is developed. A diffuser film was manufactured through coating UV curable monomer on a plastic film. The diffuser layer coated on plastic film showed excellent optical transmittance.
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Kim, Min-Wan;Kim, Hie-Chul;Kim, Suk-Hwan;Lee, Sang-Woo;Choi, Byung-Ho;Kim, Kyung-Hwan;Sohn, Woo-Keun 1068
We report the techniques to obtain the high uniformity of the phosphor film thickness in the cold cathode fluorescent lamps, which are widely used as a back-light for the liquid crystal display. The thickness variation of the phosphor layer was sensitive to blowing conditions. The optimum conditions were obtained at flow rate of 15 sccm for 30 min at 40$^{\circ}C$ . The optimum and uniform thickness of a phosphor layer gives good luminous output. -
Ion shower doping using a source gas of
$PH_3/H_2$ was conducted on excimer-laser-annealed (ELA) Poly-Si. As-implanted damage is accumulated more and more with the increase of an acceleration voltage and a doping time. In this study we found that dopant-activation is relatively a rapid kinetic-process while damage-recovery is not. -
In this paper, we report
$Eu^{2+}$ activated green phosphor$Ba_2CaMgSi_2O_8:Eu^{2+}$ . This phosphor absorbs ultroviolet radation and emits a green visible light. The phosphors were synthesized by conventional solid state reaction method. Reagent grade$BaCO_3$ ,$CaCO_3$ , MgO,$SiO_2$ ,$Eu_2O_3$ were used as raw materials. The raw materials were mixed thoroughly with an appropriate amount of ethanol in an agate mortar and then dried at 90$^{\circ}C$ for 2 hours. The mixture was sintered at 900$^{\circ}C$ for 2 hours and reheated at the mild reducing atmosphere 5%$H_2$ gas mixed with 95%$N_2$ gas at about 900$^{\circ}C$ to 1250$^{\circ}C$ for 2 hours. The photoluminescence spectra of the phosphor powders were measured by a fluorescent spectrophotometer. The crystal structure of phosphor powders were investigated by X-ray diffractometer. -
Dense
$BaMgAl_{10}O_{17}:Eu^{2+}$ phosphor particles with a spherical shape have been synthesized through spray pyrolysis method using basic aluminum nitrate precursor as a spray solution. Also, a thin layer of silica on the surface of$BaMgAl_{10}O_{17}:Eu^{2+}$ particles were coated by hydrolysis reaction of alkoxide sources with the particles. The correlation between PL intensity and surface treatment by coating for the dense$BaMgAl_{10}O_{17}:Eu^{2+}$ particles have been investigated. -
We applied the spray pyrolysis technique to prepare Mn-doped
$BaMgAl_{10}O_{17}$ (BAM) particles with high photoluminescence, which could be used in the plasma display device as a green phosphor. Several preparation conditions were investigated in order to tail the vacuum ultraviolet (VUV) characteristics. Some portions of barium were replaced with strontium to improve the luminescent intensity of BAM:Mn particles under VUV excitation. The content of Mn and Sr was optimized to obtain high luminescent efficiency under VUV excitation. Finally, the optimized BAM:Mn green particles showed higher photoluminescence intensity than that of commercial$Zn_2SiO_4$ and comparable with commercial barium-aluminate phosphor. -
Nazarov, Michael;Kang, Jong-Hyuk;Jeon, Duk-Young;Bukesov, Sergey;Popovici, Elisabeth-Jeanne;Muresan, Laura 1087
Samples of yttrium oxide doped with trivalent europium have been prepared by ceramic techniques, under different synthesis conditions; barium chloride ($BaCl_2$ ) and sodium tetraborate ($Na_2B_4O_7$ ) were tested as flux. The improvement of luminescence properties in dependence on substitution of$Eu^{3+}$ for$Y^{3+}$ in the host lattice, under electron and UV excitations is demonstrated The obtained results are discussed with respect to the employed processing method. -
High-luminous efficiency full-color emissions in photoluminescence (PL) were obtained in
$GdVO_4$ phosphor thin films co-doped with various amounts of Eu, Er and/or Tm and postannealed at approximately 1000$^{\circ}C$ . The$GdVO_4$ :Eu,Er,Tm phosphor thin films were deposited on thick$BaTiO_3$ ceramic sheets by r.f. magnetron sputtering using powder targets and postannealed in an air atmosphere. The rare earth (RE) content (RE/(Gd+V+RE) atomic ratio) in the oxide phosphor thin films was varied in the range from 0.1 to 2 at.%. It was found that the excitation of$GdVO_4$ :Eu.Er,Tm thin films is attributed to band-to-band transition. A white PL emission was obtained in a$GdVO_4$ :Eu,Er,Tm thin film with Eu, Er and Tm contents of 0.2, 0.7 and 1 at.%, respectively: CIE chromaticity color coordinates. (X=0.352 and Y=0.351). In addition, a white emission was obtained in a thin-film electroluminescent (TFEL) device made with this thin film. -
In this study,
$Bi_2O_3-B_2O_3-ZnO$ glass system, which was expected to have similar properties with PbO containing glass system, was selected as a PbO replaceable potential composition because the atomic weight and ionic radius of Bi is similar to those of Pb. Glasses with different modifier/former ratio were prepared by melting the raw ingredient mixtures in$Bi_2O_3-B_2O_3-ZnO$ system, and the thermal and electrical properties of the sintered samples were examined. The glass transition temperatures and the dielectric constant of the glass pellets were between 350$^{\circ}C{\sim}$ 500$^{\circ}C$ and 15-35, respectively. -
Characterization of
$BaO-B_2O_3-SiO_2$ glass for the application to PDP;Effect of BaO/$B_2O_3$ ratioFor the development of Pb-free low temperature sintering glass frits,$BaO-B_2O_3-SiO_2$ system was examined. The content of BaO and$B_2O_3$ was changed when the content of$SiO_2$ was fixed to 10 mol%. When the content of BaO was more than 60 mol% devitrification was observed. In the sintering temperature range between 520${\sim}$ 620$^{\circ}C$ , the optimum sintering temperature decreased as the content of BaO increased. When BaO${\geq}$ 45 mol%, the glasses were crystallized after sintering. Candidate compositions are suggested in$BaO-B_2O_3-SiO_2$ system, which can replace the PbO containing glass system. -
Lee, Baek-Woon;Song, Keun-Kyu;Yang, Young-Chol;Park, Cheol-Woo;Oh, Joon-Hak;Chai, Chong-Chul;Choi, Jeon-Gye;Roh, Nam-Seok;Hong, Mun-Pyo;Chung, Kyu-Ha;Lee, Seong-Deok;Kim, Chang-Yong 1103
Last year, we introduced a TFT-LCD with RGBW color system. The primary advantage of the RGBW system is that its optical efficiency is at least 50% higher than the RGB system. However, it is not a simple task to incorporate the new color system into the infrastructure of the RGB system: the driving circuitry, fabrication of color filter, and color conversion. In this report, the practical hurdles are discussed and the solutions are presented. -
LCDs show motion image blur due to slow response time and a hold-type driving method. In this paper, we investigate motion blur phenomena and quantitatively show that the motion blur can be significantly reduced through a combination of dynamic capacitance compensation (DCC) and black data insertion.
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n+ etching process is investigated in the fabrication of TFF-LCD using low resistance data line of Mo/Al/Mo. Problems of consumption of upper Mo layer and contamination of channel area are resolved. Either of HCl or
$Cl_2$ can be selected as a main etchant gas, and either of$SF_6$ or$CF_4$ can be selected as an additive. Plasma treatment after n+ etching process can reduce the off-current high problem. -
We investigated the liquid crystal (LC) alignment phenomena using hydrogenated amorphous carbon (a-C:H) thin films. For LC alignment, the surface of a-C:H thin films is treated with low energy ion beam. We investigated the relationship between the properties of a-C:H thin films and LC alignment phenomena.
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Various technologies for new reflective LCDs with high performance are reviewed in this paper. Among of them, reflective STN-LCDs with single polarizor, novel single polarizor reflective LCDs based upon R-IPS mode and VA(vertical aligned) mode reflective color TFT-LCDs are discussed comprehensively. In addition, some new technologies which are under developed for the moment are also introduced briefly, including single polorizor reflective AF-LCDs (Antiferroelectric LCD) and reflective LCDS with none polorizor. Finally, we research the method to optimize the reflective LCDs.
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Park, Chang-Joon;Hwang, Jeoung-Yeon;Kang, Hyung-Ku;Seo, Dae-Shik;Ahn, Han-Jin;Kim, Jong-Bok;Kim, Kyung-Chan;Baik, Hong-Koo 1121
Carbon Nitride exhibits high electrical resistivity and thermal conductivity that are similar to the properties shown by diamond-like carbon (DLC) films. These diamond-like transport properties in Carbon Nitride come in a material consisting of$sp^2$ -bonded carbon versus the$sp^3$ -carbon of DLC. The diamond-like properties and nondiamond-like bonding make NDLC an attractive candidate for applications. Liquid crystal (LC) alignment capabilities with ion beam exposure on carbon nitride thin films and Electro-Optical (EO) performances of the ion-beam aligned twisted nematic liquid crystal display (TN-LCD) with oblique ion beam exposure on the Carbon Nitride thin film surface were studied. An excellent uniform alignment of the nematic liquid crystal (NLC) alignment with the ion beam exposure on the Carbon Nitride thin films was observed. In addition, the good EO properties of the ion-beam-aligned TN-LCD were achieved. Finally, we achieved the residual DC property of the ion-beam- aligned TN-LCD on the Carbon Nitride thin film. -
We have investigated the generation of pretilt angle for a nematic liquid crystal (NLC) alignment with rubbing alignment method on the two kinds of polyimide (PI) surfaces using thin plastic substrates. The NLC pretilt angles generated on thin plastic substrates are higher than that on the glass substrate. We study that AFM (atomic force microscope) image of rubbed PI surface with polymer film has formed the micro-groove. Also, EO characteristics of the TN-LCD with a rubbed PI surface based on polymer are almost the same as that of the TN-LCD with a rubbed PI surface based on glass.
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In this paper, we intend to make FFS mode cell with LC alignment used non-rubbing method, ion beam alignment method on the a-C:H thin film, to analyze electro-optical characteristics in this cell. We studied on the suitable inorganic thin film for FFS-LCD and the aligning capabilities of nematic liquid crystal (NLC) using the new alignment material of a-C:H thin film as working gas at rf bias condition. A high pretilt angle of about 5
$^{\circ}$ by ion beam(IB) exposure on the a-C:H thin film surface was measured. An excellent voltage-transmittance (V-T) and response time curve of the ion-beam-aligned FFS-LCD was observed with oblique ion beam exposure on the DLC thin films. -
In this paper, we have improved a novel ECB mode using bend structure with high tilt angle in the unique condition by Hot plate equipment. The new control of tilt angle for nematic liquid crystal (NLC) with negative and positive dielectric anisotropy on the rubbed homeotropic polyimide (PI) using baking method by Hot plate equipment was investigated. LC tilt angle decreased with increasing baking temperature and time. We suggest that the development of the novel ECB cell using control of tilt angle on the homeotropic surface is a promising technique for the achievement of fast response time and high contrast ratio.
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The synthetic route and physical properties for three-ring derivatives, trans-2,3,2',3'-tetrafluoro-4-alkyl-4'-(4-alkyl-cyclohexyl)-biphenyl and 4-alkyl-cyclohexane carboxylic acid 2,3,2',3',4'-pentafluoro-biphenyl-4-yl ester are presented. They exhibit broad range nematic phases exceeding 30K and low viscosity of nematic liquid crystal mixtures containing these materials. Their viscosity is compared with that of homologues with a lateral isothiocyanate group and show large negative dielectric anisotropies. The threshold voltage
$V_{th}$ was low enough to be operated at a driving voltage of 5V. Our novel LC compounds are suitable materials for the improvement of dielectric anisotropy of vertical align liquid crystal displays (VA-LDCs). -
We studied on an electro-optical (EO) hysteresis, coming from the in-plane modulation of the molecular reorientation, in highly twisted nematic liquid crystal devices. Varying a ratio d/
$P_0$ of the cell thickness d to the natural pitch$P_0$ , the EO hysteresis and the twisted angle transition were observed and analyzed in terms of the periodicity of the in-plane modulation within the continuum theory. -
In this study, we presented a novel method to calculate unknown voltages on the floating electrodes introduced in a unit pixel of TFT-LCDs using three-dimensional molecular director simulation. For the simulation of the potential distribution profiles generated under the influence of the floating electrodes, we used the floating boundary condition on the surface enclosing the floating electrodes. The constraint for the floating boundary condition was derived from the charge neutrality condition about the floating electrodes disconnected from voltage sources. For the pixel with the floating electrodes patterned between the pixel and the data electrodes, we simulated the molecular director and the potential distribution in three-dimension, and then observed the location of the disclination lines around the edge of the pixel electrode. As a result, it was revealed that the floating electrodes significantly affect the electro-optical characteristics such as the location of the disclination line.
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Ahn, Han-Jin;Kim, Kyung-Chan;Kim, Jong-Bok;Baik, Hong-Koo;Park, Chang-Joon;Hwang, Jeoung-Yeon;Seo, Dae-Shik 1155
Various inorganic alignment layers of nematic liquid crystal (NLC) molecules were investigated. Ar ion beam (IB) irradiation was utilized for alignment method and homogenous and homeotropic orientations with tilt angle were obtained on the suitable inorganic thin films. Proper doping materials were added to diamond-like carbon (DLC) films. In the case of homogeneous alignment, nitrogen doping affected the increase of pretilt angle, while the fluorine bonding in the DLC films was induced the tilted homeotropic alignment cause its extreme hydrophobic property. These results showed that ion beam irradiation method could be applied to the various alignment mode of NLC such as IPS, TN and MVA. -
Lee, Gi-Dong;Lee, Jong-Wook;Ko, Tae-Woon;Lee, Joun-Ho;Oh, Chang-Ho;Choi, Hyun-Chul;Kim, Jae-Chang 1159
A modeling of the nucleation and dynamical behavior of defects from an inhomogeneous surface configuration using fast Q-tensor method is realized. On modeling the defect nucleation and dynamics, A fast Q-tensor method is applied. From the numerical modeling, we confirmed that surface inhomogeneity which makes strong strain energy in the local liquid crystal director field could cause defects. Experimental result has compared with numerical modeling in order to verify the simulation of the defect nucleation. -
Cinnamate group is well-known for the dimerization reaction by ultra-violet irradiation and cinnamate polymers are studied for photo-alignment materials. The cinnamate groups of flexible polymer are found to produce LC alignment parallel to polarization direction of ultra-violet light, which is contrary to the LC orientation on conventional cinnamate polymers. The un-reacted cinnamate groups in the flexible polymer are also found to participate in cycloadducts formation by additional thermal reaction that preserves the orientation of cycloadducts, leading to the enhancement of thermal stability of LC alignment.
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Polarized ultraviolet irradiation techniques have been developed recently to produce alignment of liquid crystals (LC). Because of the excellent thermal stability and the alignment ablility of polyimides, polyimides has attracted considerable research interest for the photoinduced alignment layer. Hasegawa and Taira confirmed homogeneous alignment of LC by the decompostion of a polyimide induced by lineraly ultra-violet polarized light. It was reported that ultraviolet visible absorption spectra of a polyimide alignment film showed a remarkable change upon irradiation. In this study, we synthesized phthalic polyimide and a naphthalenic polyimide in order to investigate the effect of the polyimide structure. Some difference in terms of the photo-induced molecular orientaion of liquid crystals were observed with the polyimide structure.
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Polyimides are blended with photoreactive polymers in order to improve the thermal stability of molecular orientation of photoreactive groups induced by polarized UV irradiation. The polyimide/photopolymer blends can be applied for the photo-induced liquid crystal alignment layers. However, the polyimides are also decomposed by UV irradiation and this may have the negative effect on the orientation of liquid crystals. In order to elucidate the influence of polyimide on the molecular orientation of liquid crystal, non-photoreactive naphthalenic polyimide (1,4,5,8-naphthalene tetracarboxylic dianhydride} was selected for the blend alignment layers. We prepared the blends of photo-reactive coumarin polymers and naphthalenic polyimide, and investigated the orientation of liquid crystals. Thermal stability of the orientation of liquid crystals was enhanced due to the thermally stable polyimide. However, there was no other side-effect of polyimide on the orientation of liquid crystals and this might be attributed to the non-photo-reactivity of naphtahlenic polyimide.
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In a previous work we reported the bistable property by doping a chiral material in a splay cell. The bistable states are the splay state and the metastable 180
$^{\circ}$ twist state. The retention time of the metastable state can be changed by the variation of d/p (cell gap over pitch), cell gap, pretilt angle, azimuthal anchoring force, liquid crystal material, and so on. In this paper we will present uniform bend transition and twist retention time improvement in a multi-domain BCSN LC cell by using the multi cell gap method. -
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We have studied a single gap transflective liquid crystal display (LCD) associated with in-plane switching (IPS) mode. In the transmissive IPS cell, the transmittance of electrodes and above electrodes is different, that is, the degree of rotation of the LC director between electrodes and above electrodes is 45
$^{\circ}$ and 22.5$^{\circ}$ , respectively. Utilizing the different rotating angle of the LC director and in-cell retarder with a quarter-wave plate used below the LC layer, the IPS transflective LCD is realized such that the area between electrodes is used as a transmissive part and the area above electrodes is used as a reflective part. -
We have studied contrast ratio of a homogeneously aligned nematic liquid crystal (LC) display as a function of the angle between the polarizer axis and LC director. The results show that a cell configuration in which a polarizer axis facing a light source coincides with a short LC axis has a better process margin in terms of high contrast ratio than that of the cell coinciding with a long LC axis.
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We have studied a liquid crystal (LC) mode, named locked super homeotropic (LSH), where the LCs aligned homeotropically are locked by surrounding walls such as cubic, hexagonal and cylinder. In the device, the vertically aligned LCs tilt down symmetrically around the center of the cell when a voltage is applied and thus it exhibits wide viewing angle. In addition, since the LCs is locked in micro domains the LCs do not flow to the bottom of the panel by gravity.
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Polyamic acid precursors were prepared by mixing various main chain dianhydrides, main chain diamines and side chain diamines. Copolyimide films with alkylcyclohexylbenzene as a side chain were prepared by thermal imidization of polyamic acid precursors. Pretilt angles on rubbed polyimides changed according to the side chain and main chain structures of the polyimide. Consequently, we found that LC pretilt angles of polyimide films with a liquid crystal structure as a side chain showed to be approximately 90
$^{\circ}$ when a linear and rigid polyimide main chain and a side chain of suitable length were employed. -
Lee, Jae-Shin;Lee, Seok-Jae;Park, Jong-Pil;Park, Tae-Jung;Kim, Do-Hyun;Lee, Sang-Yup;Jung, Dae-Hwan;Jung, Hee-Tae;Kim, Jin-Hee;Kwon, Seong-Ku 1193
We have demonstrated the use of MWCNT as a nanoscale probe to monitor the activity of enzyme kinase. To immobilize the substrate peptide using carbodiimide chemistry, plasma or strong acid treatments were used to induce carboxyl groups on the sidewall of MWCNTs. After the susbtrate peptide immobilization, increase of conductance from MWCNT devices was observed. When peptide modified MWCNTs react with enzyme kinase, conductance decreases by several orders of magnitude, and this conductance change can be explained by the phosphorylation reaction of enzyme kinase. When the sample was incubated with phosphatase to dephosphorylate the substrate peptide, nearly complete recovery of the conductance signal has been observed. 4 for 6 devices appeared the same trends. So, we can confirm that we have monitored the kinase activity on the MWCNT surface by electrical detection. -
We have studied an optically compensated splay (OCS) mode driven by fringe electric field. The OCS configuration obtained by applying voltage to vertically aligned LCs shows a dark state when an optic axis of the OCS cell coincides with one of crossed polarizer axis. When the fringe electric field is applied, the LC director rotates in plane above whole electrode surface, giving rise to the high transmittance, the low operating voltage and wide viewing angle simultaneously.
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We investigated the molecular aligning capability of a polymer layer containing ceramic nanoparticles which can be used as a gate insulator of organic thin-film transistors (OTFTs). Because of the enhanced dielectric properties arising from the nanoparticles and molecular aligning properties of the polymer, the composite layer provides excellent mobility characteristics of the OTFTs.
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The effects of surfactant on the electro-optic properties of holographic polymer dispersed liquid crystal(HPDLC) have been studied hoping to increase the diffraction efficiency and to reduce the anchoring energy at interfaces. Octanoic acid(OA) was used as sulfactant. The 2,2,2 trifluoroethyl acrylate(TFEA) was added to the monomer mixture to enhance the phase separation and improve optical properties. The morphology of holographic gratings was examined using scanning electron microscopy(SEM). Addition of surfactant was likely to reduce the surface anchoring of the nematic droplet with the polymer surface which favors lowering of the swiching field and to improve the optical qualities.
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When irradiated with visible light in HPDLC, photoinitiator and coinitiator produce a radical for photopolymerization. According to the kinds of photoinitiator and coinitiator, quantity and rate of produced a radical is different. It is influence on photopolymerization rate relate on diffraction efficiency. Thus, this paper is about the effect of photoinitiator/coinitiator combinations in terms of diffraction efficiency and real-time first order diffraction efficiency.
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Diffraction modes of holographic grating were fabricated with polyurethane acrylates(PUA). Two types of silica (AEROSIL 200 and AEROSIL R812) were added to reduce the shrinkage of polymer matrix. It was founded that shrinkage of PUA composite film was reduced with the addition of silica. HPDLC based PUA/silica composite also showed high diffraction efficiency. The morphology of the resultant gratings was analyzed by using scanning electron microscopy(SEM) and Tg of the polymer matrix by dynamic mechanical thermal analysis(DMTA).
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LC and polymer miscibility in HPDLC has been studied in terms of solubility parameter. It was found that better grating formation and diffraction efficiency were obtained when the difference in solubility parameters between polymer and LC is greater.
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We developed a new device structure using anisotropic phase separation from liquid crystal (LC) and polymer composite materials using UV intensity variation and polymer wetting properties. In the device, the LC molecules are isolated in pixels where LCs are surrounded by the inter-pixel vertical polymer walls and the horizontal polymer films on the upper substrate. These devices show very good mechanical stability against external pressure. The electro-optic characteristics and the mechanical stability of the devices are discussed in view of the flexible display applications.
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Kwon, Myeong-Hoon;Kim, Sea-Yun;Choi, E-Joon;Lee, Jong-Chan;Zin, Wang-Cheol;Lee, Chong-Kwang 1223
A series of LC polyesters containing banana-shaped mesogen and flexible spacer were synthesized. Their structures were identified by FT/IR- and NMR-spectrometry. Thermal and mesomorphic properties were investigated by using DSC and polarizing microsope. Structure of mesophase was investigated by using x-ray diffractimetry. -
We have studied the Polymer Stabilized Continuous Director Rotation (PSCDR) mode to solve the thermal shock problem which is core and main problem in CDR mode. The cell filled 95wt. % R2301 FLC and 5wt. % UCL-001 polymer is applied a low DC voltage only near the phase transition temperature from cholesteric to chiral smectic C phase transition to get defect-free alignment. In the previous work, we also confirmed layer deformation induced by an applied DC field only near the phase transition temperature from Ch to
$SmC^{\ast}$ . Results of layer structure, and characteristics of electro-optical properties between CDR and PSCDR mode will be discussed in this paper. We are also in progress to finalize the layer structures compared between CDR and PSCDR mode by x-ray measurements. -
The ratio of optimized concentration on optical characteristics for phase-separated composite organic films (PSCOF) liquid crystal display is 30% of pre-polymer (NOA65) and 70% of ferroelectric liquid crystal (Felix). The layer structure in ferroelectric liquid crystal cell made by 30% NOA65 and 70% Felix materials is tilt-bookshelf layer structure. The angle of tilt-bookshelf structure are 17
$^{\circ}$ , 12$^{\circ}$ which are almost same of tilt angle of ferroelectric liquid crystal in Sm$C^{\ast}$ phase. We know that this result is from compensating the layer buckling. In this paper, we will discuss the effect of layer structure in PSCOF cell on ratio of concentration between pre-polymer and liquid crystal by x-ray measurements. We believe that technology of PSCOF is a good solution to solve the problems of align-defect and mechanical shock for future TV application and plastic LCD. -
We have designed High Performance Prism LGP in 17 inch TFT-LCD. In test result to embody high brightness BLU in case of LGP of base and upper surface with 17 inch, thickness 8mm adding prism construct, it is superior brightness improvement than previous that of printing form about some 20% and in this course to embody actual material it succeeded prism LGP production by 17 inch injection form process.
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We developed a new cholesteric material for bistable LCDs. The material consists of dispersion of sub-micron ferroelectric particles in cholesteric host. We found that the doping of the cholesteric with ferroelectric particles in small concentration (< 1% by weight) strongly improved basic characteristics of the transition between poly-domain planar texture and focal conic texture. Decrease of the driving voltage, increase of the reflection contrast and the steepness of the transition is associated with giant steady dipole and dielectric constant of the ferroelectric particles.
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Multi-Valued Image Entropy Coding (MVIEC) is a new class of joint source channel coding, which reduces both input-width (1/4) and average current (0.36-1.3) for LCD source drivers. This paper describes the detail results on MVIEC for several image sets in order to verify the practical performance.
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For obtaining the best panel quality of color filter on array(COA) architecture in TFF LCD, we investigated the influence of deposition temperature,
$O_2$ flow, thickness on the optical transmittance, wet etching and adhesion properties of IZO deposited onto each color photo resist(red, green, blue). Average transmittance of the pixel single layer in the visible range(between 380 and 780nm) was mainly affected by thickness and showed maximum at 1250${\AA}$ while the thickness showing peak transparency in each R, G, B wavelength was different. The relation was calculated by using bi-layer transmission and reflectance model, which corresponded to experimental data very well. The adhesion of IZO deposited on each color PR was found to have enhanced value except red PR case, compared to that of IZO which was deposited on$SiN_x$ . Wet etching pattern linearity was decreased as the thickness increased. The thickness of IZO was one of vital factors in order to optimize overall pixel process for fabricating COA structure. -
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In this paper, we report new technique of preparation of material for flexible displays and E-paper technology. This material represents porous polymeric fiber based on polyacrylonitrile filled by liquid crystal.
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Light diffraction on optically anisotropic substrates with the surface microrelief has been calculated by using the OAGSM method. Varying of the microrelief depth and material birefringence allows to realize different polarization state of the light beam transmitted or reflected by the substrate. The approach can be used to optimize the LCD backlight.
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Lee, Seok-Woo;Kang, Ho-Chul;Yang, Joon-Young;Kim, Eu-Gene;Kim, Sang-Hyun;Lim, Kyoung-Moon;Kim, Chang-Dong;Chung, In-Jae 1254
Comparative study on the effects of$H_2$ vs.$O_2$ plasma pretreatment of gate oxide on the degradation phenomenon of p-channel low-temperature polysilicon (LTPS) thin-film transistors (TFTs) were performed. After high drain current stress (HDCS) with$V_{gs}$ =$V_{ds}$ , the p-channel TFTs pretreated by$O_2$ plasma showed increased immunity to the degradation of device characteristics such as threshold voltage and maximum field effect mobility because of the higher binding energy of Si-O bond than that of Si-H bond. The investigation of degradation phenomenon of these parameters with the applied power suggests that self-heating can be the major cause of degradation of polysilicon TFTs. -
Lee, Seok-Woo;Kang, Ho-Chul;Nam, Dae-Hyun;Yang, Joon-Young;Kim, Eu-Gene;Kim, Sang-Hyun;Lim, Kyoung-Moon;Kim, Chang-Dong;Chung, In-Jae 1258
Degradation phenomenon in the low-temperature polysilicon (LTPS) thin-film transistors (TFTs) with different junction structures was investigated. A gate-overlapped lightly doped drain (GOLDD) structure showed better hot-carrier stress (HCS) stability than a conventional LDD one. On the other hand, high drain current stress (HDCS) at$V_{gs}$ =$V_{ds}$ conditions caused much severe device degradation in the GOLDD structure because of its higher current level resulting in the higher applied power. It is suggested that self-heating-induced mobility degradation in the GOLDD TFFs be suppressed for using this structure in short-channel devices. -
To increase the performance of the light diffusion films, we controlled the three dimensional microstructure of the organic fillers(beads). The refractive index, the size distribution and the three dimensional distribution of beads play an important role to determine the performance of light diffusion films for the backlight unit of TFT-LCD.
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This study focuses on the color characteristics of FFS (Fringe Field Switching). We use various methods to prove the high performance of color characteristics in the Fringe Field Switching mode. We have described a color performance of 15" XGA product by the viewing angle range using x, y parameters of CIE chromaticity diagram. And so we used the 2 dimensional analyzing to prove the color shift distribution by viewing angle.