한국정보디스플레이학회:학술대회논문집
The Korean Infomation Display Society (KIDS)
- Annual
Domain
- Electricity/Electronics > Display
2005.07b
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Barrier ribs in the plasma display panel (PDP) function to maintain the discharge space between the glass plates as well as to prevent optical crosstalk. Patterning of barrier ribs is one of unique processes for making PDP. Barrier ribs could be formed by screen-printing, sand blasting, etching, and photolithographic process. In this work photosensitive barrier rib pastes were prepared by incorporating binder polymer, solvent, functional monomers photoinitiator, and barrier rib powder of which surface was treated with fumed silica particles. Studies on the function of materials for the barrier rib paste were undertaken. After optimization of paste formulation and photolithographic process, it was applied to the photosensitive barrier rib green sheet and was found that photolithographic patterning of barrier ribs could be formed with good resolution up to
$110{\mu}m$ height and$60{\mu}m$ width after sintering. -
Producing high transparency dielectric is still one of the most important subjects in the PDP process for improving luminous efficiency. It has been reported by many workers that transparency is improved by controlling the composition of the frit, the frit size and distribution, and the firing atmosphere. To understand the mechanism of discoloration of frit,
$Bi_2O_3$ and$B_2O_3$ glasses were used for a leaching test using water and alcohol solution in milling. As a result, the frit prepared by wet milling had lower chemical durability than that prepared by dry milling. The leached layer around the frit showed high stability for heat treatment because the frit surface was covered with hydroxides or hydrates which was resulted from a reaction between the frit and the solution during milling. -
Organosilicate Glass has quite a long history in the Semiconductor industry but has received very limited evaluation for Display industry applications. In this paper, we would like to introduce several kinds of Organosilicate Glasses for Display applications.
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In order to enhance discharge efficiency of Plasma Display Panel (PDP), we used an electride as electron emission layer for PDP during PDP discharge process. As the electride used in this study,
$12CaO7Al_2O_3$ , has low work function, it is expected to yield high electron emission during glow discharge process.$12CaO7Al_2O_3$ powder was synthesized from$CaCO_3$ and$Al(OH)_3$ powder and Ca treated for realization of electride characteristics. The$12CaO7Al_2O_3$ powder was coated on the surface of dielectric layer of PDP and discharge characteristics of electride material were evaluated. -
There has been a new trend to integrate various kinds of circuits by low temperature polycrystalline silicon thin film transistor (LTPS TFT) on insulator substrates to achieve System on Panel (SOP) for flat panel displays. In this paper, we will review the trend of the SOP and discuss the utility and future possibility of the SOP.
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Quick-Response Liquid Powder Display (
$QR-LPD^{(R)}$ ) is a promising device for ultra-low-power applications. Several driving methods for this display were investigated in terms of image quality and power consumption. The power consumed both in a panel and in the output circuits of driver LSIs was evaluated by analog circuit simulation and discussed. -
This paper presents issues of display hardware architecture, relating to memory, display driver IC architecture, and chip-to-chip interface. To achieve a low power and low cost mobile phone, not only the display architecture must be carefully selected, but also the driver-ICs optimized to accommodate the different modes of operation found in typical handheld devices. The technique of forming a photo sensor in each pixel using TFT and display module architecture are developed to add multi functions in display such as fingerprint recognition, image scanning, and integrated touch screen. Detailed architectures of IC partitioning, high-speed serial interface, D/A converter, and multi functions such as fingerprint recognition and image scanning using photo sensors are important to a power optimized system.
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We developed new circuit architecture for reducing the power consumption and chip-size of driver ICs. In this paper we describe a new drive scheme, based on the concept of time -sharing output and optimal circuit design based on color resolution. In case of 132 x 176-pixel class, we used only 8 O p-A mps for a 262-k color display.
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The industry of LCD monitor and LCD/TV production is complicate, so there are several OEM/ODM companies concentrated on technical and professional skills. Brand name company establishes its own brand name, sells its own product, and reflects market request. Therefore, the main duty of brand name company is on sales and marketing. This article explains the operating flow on LCD monitor and LCD/TV industry, operating relationship between brand name company and OEM/ODM, and advantage and disadvantage on different points. Furthermore, future trend of LCD monitor and LCD/TV can be reviewed in the article.
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In recent years, we use overdriving scheme to improve the response time of the liquid crystal. Since conventional overdriving scheme uses memory to perform ideal processing, it is desired to reduce system cost by decreasing the data stored in these SDRAMs. As a general compression method, quantization, sub-sampling and Block Truncation Coding ( BTC ) are used, which process data in block base and cause block effect. So we proposed new data compression method by color space conversion. Because this method compresses luminance and chrominance signal by different ratio, it can efficiently reduce error of block effect in decompression image.
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High-pixel-density displays are now under development to meet the needs of next-generation mobile devices; methods to more efficiently build such displays are described. Displays based on subpixel rendering and RGBW technologies, known as PenTile
$Matrix^{TM}$ RGBW, are shown to offer the best approach to meeting the demanding requirements of low manufacturing cost, high brightness, and low power. -
Recent developments in Dual Select Diode (DSD) AMLCD technology are described. They include a novel array design and drive method with shared select lines, which leads to higher aperture ratio and a further reduction of module cost. A Color-On-Array DSD process and pixel layout compatible with In-Plane-Switching is also proposed.
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We report a cell gap variation tolerant liquid crystal display(LCD). Since the cell gap variation of the LCD results in the variation of brightness and contrast ratio, we should control carefully the process to get the uniform cell gap. For the projector application, this is more significant and the one reason of the low yield. We observed that the brightness variation of LCD is suppressed by insertion of dielectric layer between the pixel electrode and liquid crystal.
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Park, Hyun-Woo;Kim, Soo-Hwan;Kim, Gyoung-Bum;Hwang, Sung-Woo;Kim, Su-Ki;McCartney, Richard I. 882
As the TFT-LCD panels become larger and provide higher resolution, the distributed capacitive and resistive lines induce the propagation delay, reduce the TFT-on time and deteriorate the pixel chargingratio. A number of the compensation methods, like the H-LDC (Horizontal Line Delay Compensation), have been proposed to compensate the propagation delay of the large and high resolution panels [1]. These methods, however, require the comparatively accurate gate propagation delay estimates at each column driver. In this paper, by observing the actual gate and data waveform from 15-inch XGA TFT-LCD panels, we could predict the propagation delay along the row and column line. -
In this paper, key issues of stainless steel foil substrates for display applications have been described. We studied and analyzed technical issues on substrate passivation/planarization to control surface roughness and capacitive coupling from conductive substrates. A thick (either multiple or single) passivation/planarization layer needs to be applied on the nonelectronic-grade stainless steel substrate to provide a smooth surface and electrical insulation from the conductive substrate. Especially for large size, high-resolution display applications, low k and thick passivation/planarization layers should be used for appropriate capacitive coupling. Based on our initial study, a unit area capacitance of less than
$2nF/cm^2$ of passivation/planarization layers is needed for 32" HD TV OLED displays. -
We report QLA (Quenching-rate controlled Laser Annealing) system as new concept using pulsed DPSSL and CW lasers. This process can control temperature quenching-rate of poly-Si crystallization by additional CW laser and fabricate high quality poly-Si with faster scanning speed than conventional processes. In this paper, QLA system, the experimental results and theoretical discussion will be introduced.
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We propose a novel pixel structure using bootstrapped voltage programming for amorphoussilicon TFT backplane of AM-OLED (Active Matrix-Organic Light Emitting Diode) displays. The proposed structure is composed of two TFTs and one capacitor. It operates at low drive voltage (
$0{\sim}5V$ ) which can reduce power consumption comparing with the conventional pixel circuit structure using same OLED material. Also, it can easily control dark level and use commercial mobile LCD ICs. In this paper, we describe the operating principle and the characteristics of the proposed pixel structure and verify the performance by SPICE simulation comparing with the conventional pixel structure. -
A novel active matrix organic light diodes (AMOLEDs) voltage-programming pixel structure with current-correction method is proposed for largesize and high-resolution poly-Si AMOLED panel applications. The HSPICE simulation results shows that the maximum error of emission current in proposed pixel is 1.536%, 2.45%, and 2.97% with the
${\pm}12.5%$ mobility variation and${\pm}0.3V$ threshold voltage variation for 30-, 40-, and 50-inch HDTV panels, respectively. -
Micro-patterns of
$Pb(Zr_{0.53}Ti_{0.47})O_3$ , PZT, thin films with a MPB composition were deposited on$Pt/Ti/SiO_2/Si$ substrate from molecular-designed PZT precursor solution by using self-assembledmonolayer(SAM) as a template. This method includes deposition of SAM followed by the optical etching by exposing the SAM to the UV-light, leading to the patterned SAM as a selective deposition template. The pattern of SAM was formed by irradiating UV-light to the SAM on a substrate and/or patterned PZT thin film through a metal mask for the selective deposition of patterned PZT or lanthanum nickel oxide (LNO) precursor films from alkoxide-based precursor solutions. As a result, patterned ferroelectric PZT and PZT/LNO thin film capacitors with good electrical properties in micrometer size could be successfully deposited. -
It is expected that the inkjet technology offers prospect for reliable and low cost manufacturing of FPD (Flat Panel Display). This inkjet technology also offers a more simplified manufacturing process for various part of the FPD than conventional process. For example, recently the novel manufacturing processes of color filter (C/F) in LCD, or RGB patterning in OLED by inkjet printing method have been developed. This elaborates will be considered as the precious point of manufacturing process for the mass production of enlarged-display panel with a low price. On this point of view, we would like to review the status of inkjet technology in FPD, with some results on forming micro line by inkjet patterning of suspension type silver nano ink as below. We have studied the inkjet patterning of synthesized aqueous silver nano-sol on interface-controlled ITO glass substrate. Furthermore, we designed the conductive ink for direct inkjet patterning on bare ITO glass substrate. The first, the highly concentrated polymeric dispersant-assisted silver nano sol was prepared. The high concentration of batch-synthesized silver nano sol was possible to 40 wt%. At the same time the particle size of silver nanoparticles was below
$10{\sim}20nm$ . The second, the synthesized silver nano sol was inkjet - patterned on ITO glass substrate. The connectivity and width of fine line depended largely on the wettability of silver nano sol on ITO glass substrate, which was controlled by surfactant. The relationship was understood by wetting angle. The line of silver electrode as fine as$50{\sim}100\;{\mu}m$ was successfully formed on ITO glass substrate. The last, the direct inkjet-patternable silver nano sol on bare ITO glass substrate was designed also. -
We describe that an elastomeric stamp of poly(dimethylsiloxane) (PDMS) can modify the surface energy of some surfaces when brought into conformal contact with the number of stamping. We focus on an increase of the hydrophobicity of the patterned surface due to diffusion of low molecular weight (LMW) silicone polymer chains. The transfer of PDMS to the surface during patterning is relevant to and calls for attention by those who are using this method in applications where control of the surface chemistry is of importance for the application.
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Inkjet printing technology is a highly proprietary process. We have evaluated the possibility of using inkjet technique to prepare color filters. Product specification for TV application was used as a template to examine process capability. Technical aspects of ink composition, jetting ability, and surface interaction were discussed.
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This paper contains a review of methods to analise static and dynamic properties of trap states in TFTs. The Gap Density of States is extracted from C-V and I-V characteristics. Switch on transients and small signal ac measurements are used in conjunction with simulation and an analytic model to extract traps dynamic parameters.
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The characteristics of a-Si:H TFTs with silicon oxide as passivation layer were reported. It was studied that the insulating characteristics and step coverage characteristics of low temperature silicon oxide before applying to a-Si:H TFT fabrications. With the optimum deposition conditions considering electrical and deposition characteristics, low temperature silicon oxide was applied to a-Si:H TFTs. The changes in characteristics of a-Si:H TFTs were analyzed after replacing silicon nitride passivation layer with low temperature silicon oxide layer. This low temperature silicon oxide can be adapted to high resolution a-Si:H TFT LCD panels.
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Jang, Yong-Ho;Yoon, Soo-Young;Kim, Binn;Chun, Min-Doo;Cho, Hyung-Nyuck;Cho, Nam-Wook;Sohn, Choong-Yong;Jo, Sung-Hak;Choi, Seung-Chan;Kim, Chang-Dong;Chung, In-Jae 944
Highly stable gate driver circuit using a-Si TFT has been developed. The circuit has dual-pull down structure, in which bias stress to the TFTs is relieved by alternating applied voltage. The circuit has been successfully integrated in 4-in. QVGA and 14-in. XGA TFT-LCD with a normal a-Si process, which are stable for over 2,000 hours at$60^{\circ}C$ . The enhancement of stability of the circuit is attributed to retarded degradation of pull-down TFTs by AC driving. -
Yoo, Soon-Sung;Cho, Heung-Lyul;Kwon, Oh-Nam;Nam, Seung-Hee;Chang, Yoon-Gyoung;Kim, Ki-Yong;Cha, Soo-Yeoul;Ahn, Byung-Chul;Chung, In-Jae 948
New technology that reduces photolithography process steps from 4 to 3 in fabrication of TFT LCD is introduced. The core technology for 3mask-TFTs is the lift-off process [1], by which the PAS and PXL layer are formed simultaneously. To evaluate the stability of this lift-off process, outgases from photo resist on a substrate during ITO deposition and the quality of ITO film were analyzed and the conventional photo resist stripper machine which operates lift-off process was examined to see its ability to reduce particle problems of the machine. Through the development of total process and design for TFTs using this 3mask technology, panels in TN and IPS modes which exhibit same performances of a display using a conventional process were achieved. In addition, this process was already verified in the mass production line and now some products are being produced by the 3mask technology. -
Blochwitz-Nimoth, Jan;Birnstock, Jan;Wellmann, Philipp;Werner, Ansgar;Romainczyk, Tilmann;Limmert, Michael;Grubing, Andre 955
Power efficiency, lifetime and stable manufacturing processes are the crucial parameters for the success of organic light emitting diodes (OLEDs) in display and lighting applications. Highest power efficiencies of PIN-OLEDs for all principal colours and for bottom and top emission OLED structures have been demonstrated. The PIN structure, which means the incorporation of intentionally doped charge carrier transport layer in a suitable OLED layer setup, lowers the operating voltage to achieve highest power efficiencies. Up to now the n-doping of the electron transport layer has been done by alkali metal co-deposition. This has main draw-backs in terms of manufacturability, since the handling of large amounts of pure Cs is a basic issue in production lines. Here we present in detail results on PIN-OLEDs comprising a newly developed molecular n-dopant. All the previous OLED performance data based on PIN-OLEDs with alkali metal doping could be reproduced and will be further improved in the future. Hence, for the first time, a full manufacturing compatible PIN-OLED is available. -
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The search for stable electron transporters and hole injectors has become particularly intense over the last 18 months as OLED manufacturers are poised to start production of OLED panels. We report here a proprietary electron transporter (E246), which reduces the operating voltage, increases the efficiency and the lifetime of OLEDs made of fluorescent or phosphorescent systems when compared with Alq3 as an electron transporter. We also report a novel proprietary hole injector (buffer, E9363) which also reduces the operating voltage, increases the efficiency and doubles the lifetime compared to CuPC. These two materials are now available commercially for display manufacturers.
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Amorphous silicon photo diodes incorporated in a polyLED stack are applied in in pixel opticalfeedback to compensate for polyLED degradation. Large quantum efficiencies and perfect linearity are demonstrated. The photosensitivity is in agreement with optical modeling of the stack. A new scheme for ambient and cross talk light cancellation is given.
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For display drivers employ typically a-Si n-channel field effect transistors, they require an inverted OLED structure with a cathode as the bottom contact. ITO is regarded as the bottom cathode and can be applied to large size AM-OLED and transparent inverted OLEDs. We report the effective structure to improve the efficiency of electron injection from ITO cathode to
$Alq_3$ . We report the effective structure to improve the efficiency of electron injection from ITO cathode to Alq3 and studied the current density-voltage characteristics of trilayer ($Alq_3-LiF-Al$ ), LiF and Mg inserted between ITO and$Alq_3$ , respectively. We discovered that 1 nm Mg afforded the highest efficiency. -
Electron injection in OLED organic layers is improved by using alkali metals as cathode layer or as dopants inside organic layers. An innovative alkali metal dispensing technology has been developed to overcome handling problems and to ensure controlled and reliable alkali metal layers for OLED.
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Many flat panel displays displays rely on polymeric substrates with thin film coatings, such as anti-reflective, anti-static and hardcoats, to improve optical and mechanical properties of the display. In this paper we briefly discuss the principles underlying the mechanical robustness of such coated structures, and examine two fitness-for-use tests currently employed by the industry. We compare the teachings with some results obtained with our hardcoats and anti-reflective coatings.
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Many applications, such as the lenses of mobile phones, involve complex 3D shapes. Delivering effective AR/AG surfaces in 3D is becoming an important challenge to the display industry. This paper shows how the combination of motheye structured AR hardcoats and In-Mold Decoration techniques can deliver this desirable functionality.
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Lee, Woo-Jae;Hong, Mun-Pyo;Seo, Jong-Hyun;Rho, Soo-Guy;Hong, Wang-Su;Jeon, Hyung-Il;Kim, Sang-Il;Chung, Kyu-Ha 988
A 5.0-inch plastic TFT-LCD with the resolution of$400{\times}3{\times}300$ lines (120ppi) was developed. The device is a transmissive type with the transparent PES plastic substrates. The PES films with one side barrier coating were used for the device. In order to produce the high resolution display device, the alignments between all the layers for the TFT and CF are essential. The fundamental shrinkage effect and the thermal expansion behavior of the plastic substrates with and without the barrier coatings were studied. The proper annealing processes followed by immediate second bar-rier coating processes provide the optimal alignment between all the layers of the TFT and CF.. -
We have successfully commercialized a novel optical compensation film, OCB-WV film, for OCB-LCD-TVs which has fast response time and wide viewing angle. The OCB-WV film consists of a 45degree-aligned discotic layer and a high Rth biaxial TAC film, which is suited for a roll-to-roll polarizer manufacturing process. This OCB-WV has brought out the excellent features that OCB intrinsically has, making nextgeneration fast-response LCD-TVs possible and free from image blurring in conjunction with an impulsive driving scheme.
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A plastic substrate for flexible display is developed. The gas barrier and optical properties of the substrate is improved through depositing silicon oxide/nitride layer and coating polymer layer on plastic film by sputtering process and wet coating process. Roll to roll processes will guarantee the productivity in the whole production process of the plastic substrate.
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We report the development of the equipment that can measure the transmittance of the polarizer for TFTLCD application versus azimuth angle of the linear polarization at each micro spot in the section, and therefore measure the degree of iodine permeation and alignment quantitatively at each area of the section.
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Dean, K.A.;Coll, B.F.;Dinsmore, A.;Howard, E.;Hupp, M.;Johnson, S.V.;Johnson, M.R.;Jordan, D.C.;Li, H.;Marshbanks, L.;McMurtry, T.;Tisinger, L.Hilt;Wieck, S.;Baker, J.;Dauksher, W. J.;Smith, S.M.;Wei, Y.;Weston, D.;Young, S.R.;Jaskie, J.E. 1003
We demonstrate color video displays driven by carbon nanotube electron field emitters. These nanotubes are incorporated into the device by selective growth using low temperature chemical vapor deposition. The device structure is simple and inexpensive to fabricate, and a 45 V switching voltage enables the use of low cost driver electronics. The prototype units are sealed 4.6” diagonal displays with 726 um pixels. They represent a piece of a 42” diagonal 1280x720 high definition television. The carbon nanotube growth process is performed as the last processing step and creates nanotubes ready for field emission. No activation post-processing steps are required, so chemical and particulate contamination is not introduced. Control of the nanotube dimension, orientation, and spatial distribution during growth enables uniform, highquality, color video performance. -
Chi, Eung-Joon;Choi, Jong-Sick;Chang, CheolHyeon;Park, Jong-Hwan;Lee, Chul-Ho;Choe, Deok-Hyeon;Lee, Chun-Gyoo 1008
In this study, the field emission display with carbon nanotube emitter is developed for the large size HDTV application. Two structures for electron beam focusing are developed on the typical top-gate cathode. The metal grid and focusing gate structure are proved to be effective for the focusing. The data switching voltage for the double gate structure is lower than 30V which is competitive value in respect of the cost for driver electronics. The brightness and color gamut are comparable to those of the commercial product such as CRT. -
Nakata, S.;Sawada, T.;Fujikawa, M.;Nishimura, K.;Abe, F.;Hosono, A.;Watanabe, S.;Yamamuro, T.;Shen, Z.;Suzuki, Y.;Okuda, S. 1012
We have developed the technique of fabricating triode structure with simple stacking method using a polymer insulator that is suitable for large panel and the activation method after the fabrication. By the techniques, a test panel was manufactured and proves good emission property and uniformity. -
Kim, Do-Yoon;Yoo, Ji-Beom;Berdinski, A.S.;Han, In-Taek;Kim, Ha-Jong;Jin, Yong-Wan;Kim, Jong-Min 1016
We studied the density control of carbon nanotubes (CNTs) which were grown on the iron nanoparticles prepared from iron-acetate [$Fe(II)(CH_3COO)_2$ ] solution using freeze-dry method. The density of CNTs was controlled for the enhancement of field emission. The patterning process of iron-acetate catalyst-layer for the fabrication of electronic device was simply achieved by using alkaline solution, TMAH (tetramethylammonium hydroxide). We applied this patterning process of catalyst layer to formation of the electron emitter with under gate type triode structure. -
We have fabricated a high electron source from carbon nanotubes (CNTs) using hot-press method. Using hot-press method, we are able to control the tube density and the morphology of CNT films. We propose that the high emission current is due to the solid adhesion between the CNTs and substrates and uniform morphology of CNT film.
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Kim, Hyun-Jae;Diep, Bui Van;Bonnassieux, Yvan;Djeridane, Yassine;Abramov, Alexey;Pere, Roca i Cabarrocas 1025
Microcrystalline Si (${\mu}c-Si$ ) TFTs were fabricated using a conventional bottom gate amorphous Si (a-Si) process. A unique${\mu}c-Si$ deposition technique and TFT architecture was proposed to enhance the reliability of the TFTs. This three-mask TFT fabrication process is comparable with existing a-Si TFT procesess. In order to suppress nucleation at the bottom interface of Si, before deposition of the${\mu}c-Si$ an$N_2$ plasma passivation was conducted. A typical transfer characteristic of the TFTs shows a low off-current with a value of less than 1 pA and a sub threshold slop of 0.7 V/dec. The DC stress was applied to verify the use of${\mu}c-Si$ TFTs for AMOLED displays. After 10,000 s of application of the stress, the off-current was even lowered and sub-threshold slope variation was less than 5%. For AMOLED displays, OLED pixel simulation was performed. A pixel current of 13${\mu}A$ was achieved with$V_{data}$ of 10 V. After the simulation, a linear equation for the pixel current was suggested. -
A 262K-color QVGA LTPS AMLCD was developed. This panel has integrated gate driver and data multiplexer (1:3) by p_Si LTPS TFT process. The commercialized driver IC was adopted to implement this display. Fine image quality, low powerconsumption and cost-efficiency feature make the panel be suitable for mobile application.
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Kang, Myung-Koo;Lee, Joong-Sun;Park, Jong-Hwa;Zhang, Lintao;Joo, Seung-Yong;Kim, Chul-Ho;Kim, Il-Kon;Kim, Sung-Ho;Park, Kyung-Soon;Yoo, Chun-Ki;Kim, Chi-Woo 1033
High resolution 2.1” QVGA LTPS LCD (190ppi) having high aperture ratio of 65% could be successfully developed using state-of-the-art SLS technology and active/gate storage structure. Cost effective P-MOS 6-Mask structure was used. Full gate and transmission gate circuits are integrated in the panel. The high aperture ratio was obtained by using active/gate capacitance structure, which can reduce storage capacitance area. The aperture ratio was increased to 65% from 49% of conventional gate/data capacitance structure. The brightness was increased from 180cd to 270cd without any degradation of optical properties such as contrast ratio, flicker or crosstalk. -
Zhang, Lintao;Kang, Myung-Koo;Lee, Joong-Sun;Park, Jong-Hwa;Joo, Seung-Yong;Moon, Kuk-Chul;Kim, Il-Kon;Kim, Sung-Ho;Park, Kyung-Soon;Yoo, Chun-Ki;Kim, Chi-Woo 1035
2.32-inch$320{\times}350$ TFT-LCD with high resolution (206PPI) for advanced mobile phones could be successfully developed. The compact pixel design based on PMOS SLS technique is used to achieve this high resolution. Gate driver and part of data driver are integrated onto the glass substrate. High brightness (170cd) and contrast ratio (400:1) were obtained with very low flickering and crosstalk levels. -
Lee, Seok-Woo;Kang, Ho-Chul;Oh, Kum-Mi;Kim, Eu-Gene;Park, Soo-Jeong;Lim, Kyoung-Moon;Kim, Chang-Dong;Chung, In-Jae 1038
Linear kink effect (LKE) induced mainly by selfheating on the reliability of divided channel poly-Si TFTs has been studied. The LKE was enhanced for compact designed structure to achieve narrow bezel, which was explained by the difference in heat dissipation capability, thus self-heating immunity in TFT. -
Kim, Sung-Han;MacPherson, Charlie;Srdanov, Gordana;Chen, Peter;Stevenson, Matt;Baggao, Erlinda;Yu, Gang;Parker, Ian;O’Regan, Marie 1044
Rapid progress has been achieved towards commercially viable full color polymer OLED devices. New full color polymer OLED displays which incorporate a novel hole injecting-transporting layer show high efficiency, low operating voltage and long lifetimes. The performance of a 14.1" WXGA a-Si based solution processed AMOLED full color display is described. -
Rhee, Jung-Soo;Lee, Dong-Won;Chung, Jin-Koo;Wang, Jian-Pu;Hong, Sang-Mi;Cha, Soon-Wook;Choi, Beom-Rak;Jung, Jae-Hoon;Kim, Nam-Deog;Chung, Kyu-Ha;Gregory, Haydn;Lyon, Peter;Creighton, Colin;Bale, Mark;Carter, Julian 1046
We have developed polymer LED displays using ink jet printing without visible swathe marks which can be observed during display operation. In addition, we have also developed a single-pass printing technology for hole-conduction layer deposition to significantly reduce the complexity of interlacing printing across the panel which is known as an alternative to remove the swathe mark. -
We report the development frontiers that are dictating the speed of adoption of polymer organic light emitting diode (P-OLED) technology in market applications. Our presentation includes both the developments taking place in materials and the rapid advances in the manufacturing processes used for solution processable P OLEDs. On the manufacturing side, the latest progress in ink jet printing process is discussed. On the materials side, we look at both fluorescent and phosphorescent material performance including the CDT development roadmap.
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Electrical and optical characteristics of MEH-PPV-based PLEDs with the LiF anode interfacial layer were investigated. The maximum luminance efficiency of the device with a LiF anode interfacial layer of 1-nm-thick was 3.0 lm/W, which is higher than 1.97 lm/W of the device without a LiF layer. By inserting LiF, excess injected holes from ITO anode can be blocked and hence the recombination ratio of electrons and holes can be increased in the emitting layer to improve device efficiency.
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Analytical solutions are obtained for the director reorientation dynamics of both VA and IPS modes by considering a possible effect of the molecular flow, providing a theoretical basis of the relations between the response characteristics of the display and the physical properties of the liquid crystal material used. The relevant properties of practical liquid crystal mixtures are quantitatively reviewed and the features of superior substances, used in formulating those mixtures, are presented.
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A large size flat panel LCD-TV must fulfill different requirements than a desktop LCD-monitor: The contrast must be much larger, the viewing angle should be as wide as possible and the switching times must be shorter to allow moving pictures to be displayed naturally. The "Vertically Aligned" technology is most promising to realize such a product. LC-material development for this technology began at Merck about 10 years ago. New materials based on the 1,1,6,7-tetrafluoroindane skeleton were recently synthesized via ortho-metallation and intramolecular Heck cyclization followed by an oxidative fluorination procedure. The materials offer improved properties over liquid crystals currently employed in flat panel LCD-TVs.
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TAC film is an indispensable optical component that protects the polarizing PVA (polyvinyl alcohol) film from being deteriorated and gives high durability, due to its unique features. The newly developed technology of controlling the birefringence of TAC film, together with the coating technology of a discotic material layer, enables excellent viewing angle characteristics and a cost-effective roll-to-roll polarizer manufacturing process.
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A UV-cured adhesive with a low
$T_g$ below the room temperature was used as a substrate for manufacturing a film-like liquid crystal display. This film-like LCD shows a fully flexibility due to the low$T_g$ property, and the manufacture processes are roll-to-roll compatible due to the coating processes. -
Saito, Yahachi;Seko, Kazuyuki;Kinoshita, Jun-ichi;Ishida, Toshiyuki;Yotani, Junko;Kurachi, Hiroyuki;Uemura, Sashiro 1081
Dynamic behavior of carbon nanotubes (CNTs) in an electric field is directly observed by in-situ transmission electron microscopy (TEM). The CNT field emitters examined by in-situ TEM are multiwalled, double-walled and single walled CNTs. Threshold fields for electron emission and sustainable emission currents depending on the structure of CNTs are presented, and degradation mechanism of the CNT field emitters is discussed. In addition to the microscopy studies on individual CNTs, our recent development in surface treatment of CNT layers grown by chemical vapor deposition, which brings about high density of emission current and high uniformity, is also presented. -
Lee, S.H.;Jung, S.I.;Lee, T.J.;Kim, W.S.;Cho, J.H.;Kang, H.J.;Kwon, G.M.;Park, C.J.;Seo, S.H.;Jeon, K.Y.;Ha, B.;Lee, C.J. 1087
We have investigated the synthesis and field emission properties of high-quality double-walled carbon nanotubes (DWCNTs) using a catalytic chemical vapor deposition method and a hydrogen arc discharge method. The produced carbon materials using a catalytic CVD method indicated high-purity DWCNT bundles free of amorphous carbon covering on the surface. By adopting a hydrogen arc discharge method, we could obtained high-purity DWCNTs in large-scale. DWCNTs showed low turn-on voltage and higher emission stability compared with SWCNTs. -
Song, Young Il;Jeong, Hee-Jin;Choi, Ha-Kyu;Kim, Gil-Yong;Lim, Seong-Chu;An, Key-Hyeok;Lee, Young-Hee 1091
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The effect of the dielectric constant (
${\varepsilon}$ ) of bonding materials in screen-printed carbon nanotube cathode on field enhancement factor was investigated using the ANSYS software for high-efficient CNT-cathodes. The field enhancement factor increased with decreasing the dielectric constant and reaching a maximum value when the dielectric constant is 1, the value for a vacuum. This indicates that the best bonding materials for screen-printing CNT cathodes should have a low dielectric constant and this can be used as criteria for selecting bonding materials for use in CNT pastes for high-efficient CNT-cathodes -
Multi-walled carbon nanotubes (CNTs) grown on catalyst dots by thermal chemical vapor deposition were vertically aligned with a high population density. Such densely populated CNTs showed poor field emission characteristics due to the electrical screening effect. We reduced the number density of CNTs using an adhesive tape treatment. For dotpatterned CNTs, the tape treatment decreased the CNT density by three orders of magnitude, drastically improved the turn-on electric field from 4.8 to
$1.8V/{\mu}m$ , and changed the emission image from spotty to uniform luminescence. We also report long-term emission stability of dot-patterned CNTs by measuring the emission currents with time at different duty ratios. -
Single-crystal silicon thin films on glass (SOG) and on fused-quartz (SOQ) were prepared using wafer bonding and hydrogen-induced layer transfer. Thinfilm transistors (TFTs) were subsequently fabricated. The high-temperature processed SOQ TFTs show better device performance than the low-temperature processed SOG TFTs. Tensile and compressive strain was measured respectively on SOQ and SOG. Consistent with the tensile strain, enhanced electron effective mobility was measured on the SOQ TFTs.
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We propose an improved laser crystallization method based on a directional lateral growth technique. To assess the feasibility of this technique, we have developed an experimental prototype using a 351 nm XeF excimer laser and special optics to produce a long and extremely sharp, narrow beam without need for a photo type mask pattern. Using this system, we have demonstrated very uniform directional laterally grown poly-Si films without any grain boundary protrusions. We believe this method can meet the high performance and uniformity requirements needed for future TFTs in System On Panel (SOP) and OLED applications, as well as providing high process throughput for mass production.
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Lim, Hyuck;Yin, Huaxiang;Xianyu, Wenxu;Kwon, Jang-Yeon;Zhang, Xiaoxin;Cho, Hans-S;Kim, Jong-Man;Park, Kyung-Bae;Kim, Do-Young;Jung, Ji-Sim;Noguchi, Takashi 1112
In this study, we performed excimer laser activation on Phosphorus or Boron doped a-Si (amorphous silicon) film. We've got a very low sheet resistance (Rs), Rs was 60 ohm/sq. with phosphorus doping and was 65 ohm/sq. with boron doping at each optimized laser irradiation condition. We've found Rs on activated thin film showed an unprecedented behavior in both cases, because Rs had a strong dependency on the crystallinity of the activated Si film. -
Lee, Sung-Hyun;Hong, Wan-Shick;Kim, Jong-Man;Lim, Hyuck;Park, Kuyng-Bae;Cho, Chul-Lae;Lee, Kyung-Eun;Kim, Do-Young;Jung, Ji-Sim;Kwon, Jang-Yeon;Noguch, Takashi 1116
We studied laser crystallization of amorphous silicon films prepared at ultra low temperatures ($ < 150^{\circ}C$ ). Amorphous silicon films having a low content of hydrogen were deposited by using catalytic chemical vapor deposition method. Influence of process parameters on the hydrogen content was investigated. Laser crystallization was performed dispensing with the preliminary dehydrogenation process. Crystallization took place at a laser energy density value as low as$70\;mJ/cm^2$ , and the grain size increased with increasing the laser energy. The ELA crystallization of Catalytic CVD a-Si film is a promising candidate for Poly-Si TFT in active-matrix flexible display on plastic substrates. -
A selective deposition of Co thin films for thin film transistor gate electrode has been carried out by the growth with combination of micro-contact printing and metal organic chemical vapor deposition (MOCVD). This results in the elimination of optical lithography process. MOCVD has been employed to selectively deposit Co films on preformed OTS gate pattern by using micro-contact printing (
${\mu}CP$ ). A hydrogenated amorphous silicon TFT with a Co gate selectively formed on SAMs patterned structure exhibited a subthreshold slope of 0.88V/dec, and mobility of$0.35cm^2/V-s$ , on/off current ratio of$10^6$ , and a threshold voltage of 2.5V, and thus demonstrating the successful application of the novel bottom-up approach into the fabrication of a-Si:H TFTs. -
For creation of low temperature polycrystallinesilicon (LTPS) the line beam excimer laser annealing (ELA) is a well known and established technique in mass production. With introduction of Sequential Lateral Solidification (SLS) some aspects such as crystalline quality, throughput and flexibility regarding the substrate size could be improved, but for OLED manufacturing still further process development is necessary. This paper discusses line beam ELA and SLS techniques that might enable process engineers to make polycrystalline-silicon (poly-Si) films with a high degree of uniformity and quality as required for system on glass (SOG) and active matrix organic light emitting displays (AMOLED). Equipment requirements are discussed and compared to previous standards. SEM images of process examples are shown in order to demonstrate the viability.
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We report state-of-the-art phosphorescent organic light emitting diode lifetime and efficiency performances for a range of emission colors. Lifetimes in excess of 100,000hrs have been demonstrated at display luminance levels for saturated red emission. External quantum efficiencies close to the theoretical maximum (e.g. 23% without enhanced optical output coupling) are also demonstrated for devices with lifetimes in excess of 15,000hrs at a display level luminance for both orange red and green.
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In this paper, a renovated approach in the fabrication of red organic light-emitting diodes (OLEDs) is described. The hard-to-control doping process required for dopant-based red OLEDs can be avoided due to the novel red fluorophores that are not concentration quenching in solid state. Doping is in general a must for phosphorescence OLEDs because of the triplet-triplet annihilation, a common problem for phosphorophore dopants. However, we have recently found that extraordinary red iridium complex showing relatively short emission lifetime render the non-doped phosphorescence red OLED possible.
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Tokairin, Hiroshi;Kuma, Hitoshi;Yamamoto, Hiroshi;Funahashi, Masakazu;Fukuoka, Kenichi;Hosokawa, Chishio 1138
We achieved a highly efficient green OLED with an efficiency of 30cd/A by using a new electron transport material and optimizing the device structure. The luminous efficiency was 16.8lm/W at$3000cd/m^2$ and the lifetime was over 60,000hr at an initial luminance of$1000cd/m^2$ . Furthermore, we obtained a threecomponent RGB white OLED by using the highly efficient green material. This RGB white OLED shows more excellent color reproducibility for full color displays with color filters, compared to a twocomponent white OLED. -
Highly Efficient Phosphorescence Emitting Materials and Applications to Organic Light Emitting DiodeNovel series of electron-transporting hosts, pentavalent aluminum complexes containing 8 hydroxyquinoline ligands and various phenolato ligands were synthesized, and organic light-emitting diodes (OLEDs) were fabricated using these complexes as host materials of phosphorescent emitting device and the fabricated phosphorescent emitting device showed low driving voltage, high efficiency at high current density and good stability under conventional driving condition.
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The frequency of inverters for driving multi-lamp backlights for LCD TV was synchronized to reduce noise from lamps and noise generated from PWM dimming.
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Choi, Jong-Hyun;Chu, Haang-Rhym;Bang, Ju-Young;Park, Hee-Jeong;Hong, Hee-Jung;Lim, Moo-Jong;Oh, Eui-Yeol;Chung, In-Jae 1153
A backlight for large-area LCD (Liquid Crystal Display)-TVs has been developed using Light Emitting Diodes (LEDs). Performances of the backlight and the methods driving the LEDs are introduced in this research. A spectral relationship between the LEDs and the color filters of a panel were investigated as well. In order to realize a CRT like dynamic effect, the area-focused luminance control (AFLC) technology was adopted in developing the backlight. Thus, a possibility of applying the LEDs to the backlight for large-area LCD-TVs was systematically proved. -
Hong, Hee-Jung;Kwon, Kyung-Joon;Choi, Jong-Hyun;Lee, Si-Hoon;Hwang, Hak-Mo;Lim, Moo-Jong;Oh, Eui-Yeol;Chung, In-Jae 1157
In order to improve the image quality of a large size LCD-TV, the Area-Focused Luminance Control (AFLC) technology with data processing algorithm has been developed. The AFLC backlight consists of 16 U-shaped lamps, and controllable areas are divided into 8 blocks. Based on the AFLC technology, the backlight luminance of each block is automatically and separately controllable. Consequently, the contrast ratio is greatly enhanced whereas the corresponding power consumption is decreased as compared with those of conventional backlights. -
A Mercury-free, flat light source which shows high luminance and luminous efficiency simultaneously has been developed. An electrodeless, dielectric barrier discharge is used to generate the plasma using Ne-Xe mixture gas of relatively low gas pressure of a few tens torr in a 4.1 inch diagonal size of flat panel. The basic properties of the long gap glow discharge and its accompanying instabilities, which prevents us from having high luminous efficiency discharge have been analyzed. A new structure and optimized driving methods have been used to generate a glow discharge which shows a wide voltage margin of a few hundred volts. The luminous efficiency and luminance could be 110 lm/W at
$1300\;cd/m^2$ and 50 lm/W at$5500\;cd/m^2$ . -
We review discharge characteristics of fluorescent lamps having noncircular cross sections. The developmental and theoretical history of noncircular cross-section lamps is summarized chronologically. In particular, discharge characteristics of noncircular cross-section lamps will be summarized and analyzed including plasma contraction, electron temperature, and ambipolar diffusion loss, which might give us some insights into the way to develop more efficient and uniform flat fluorescent lamps, which have recently arisen as a new light source of large-size backlight units for LCD TV applications.
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This thesis provides a new digital convergence method and apparatus which uses area photo sensor and new analog to digital algorithmic to identify the correct digital pattern position factor of the projection system. This method and apparatus can be applied to the convergence correction in a TV receiver with a display that comprises a display screen with photo sensors positioned adjacent to screen edges. It also can be applied to the manufacture process detection of the projection system to adjust the associative convergence parameter. In this paper, demonstrate how this convergence detecting algorithmic was implemented with four area photo sensors of special designed pattern to the rear projection CRT TV.
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Nanosize cobalt aluminate(
$CoAl_2O_4$ ) power as filter layer was coated to improve the color purityand contrast performances on inner face of CRT panel. We simulated color properties by measuring the transmittance and thickness of the coated filter layer. Contrast performance could be improved and color gamut was also changed because of the selective light absorption of filter layer at$580{\sim}605\;nm$ . -
Nowadays, CRTs are threatened by the flat panel displays (FPD). The screen quality of the CRT is one of best among the displays, however, the depth of CRTs becomes one of the most important design factor to maintain the dominated portion in the display market. When designing slim CRTs, the structure of the glass is important design factor because of the weight and safety. The stress in the glass is increased according to the shortening the total length of tube. The residual stress of the seal is also a major factor should be considered due to the large seal edge thickness. The glass design concept for Vixlim is introduced in this paper.
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A new reset method for high contrast ratio and reduction of the reset time is presented. In this new reset method, except the first subfield, a new reset pulse with only ramp-up period is adopted. In this reset method, from the third subfield, the background luminance generated during the reset period is theoretically zero until the first subfield of the following frame. Employing the new reset method, the dark room contrast ratio improved to 3084.7:1 from 189.1:1 of the conventional reset method. The new reset method reduced the required time for reset per subfield to 160us except the first subfield.
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The ramp reset driving method proposed in [1] has been widely adopted because of its stability and high contrast ratio. However, when the conventional ramp reset method is used in PDPs of higher resolution, the long required time for reset often becomes a problem. In this paper, a new driving method that requires much less reset time and that significantly improves the contrast ratio is introduced. Using this new driving method, the required time for reset could be reduced to 150us from 350us of the conventional ramp reset method, and the contrast ratio is almost infinite because the luminance of the off-cell is almost zero.
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The effects of addition of
$D_2$ to conventional gases on the discharge characteristics were investigated in this work with the aim of improving the voltage margin, the wall charge and the jitter. The addition of an extremely small gas-inlet amounts of$D_2$ increased the number of electrons which improves the$Xe^{\ast}$ density and$Xe_2^{\ast}$ density. As a result, the voltage margin, the jitter and the wall charge increased. -
Lee, H.J.;Son, C.G.;Lee, S.B.;Han, Y.K.;Jeoung, S.H.;You, N.L.;Lim, J.E.;Lee, J.H.;Moon, M.W.;Oh, P.Y.;Jeoung, J.M.;Choi, E.H. 1195
The improvement of efficiency is the one of the most important part in AC PDPs . To achieve high efficiency, high VUV emission efficiency and High ion induces secondary electron emission coefficient are needed. We have measured the emission spectra of vacuum ultraviolet rays and ion induced secondary electron emission coefficient of MgO protective layer in surface discharge AC-PDP with binary and ternary gas mixtures. We have investigated electro-optical characteristics of AC-PDPs to optimum gas mixture for high efficient. -
Inside of working PDP, there exist highly reactive conditions in the gap between two glass panels. MgO film and phosphor have been investigated as a function of discharge, also phosphor and sealing frits have been investigated as a function of temperature. Changes of impurity generation of MgO, phosphor and sealing fits were measured by using x-ray photoelectron spectroscopy (XPS) and quadropole mass spectroscopy (XPS) and quadropole mass spectrometer (QMS). Impurities such as CO,
$CO_2$ , OH and$H_2O$ were increased during discharge and heating treatment. Gaseous impurities such as carbon compounds and water deteriorated the characteristics of PDP operation during of lifetime. So metal is used to remove the impurities of phosphor and sealing frits during hearting, the result that the quantity of the impurities such as carbon monoxide and water was reduced. -
Jeong, S.H.;Moon, M.W.;Oh, P.Y.;Jeong, J.M.;Ko, B.D.;Park, W.B.;Lee, J.H.;Lim, J.E.;Lee, H.J.;Han, Y.G.;Son, C.G.;Lee, S.B.;Yoo, N.L.;Choi, E.H. 1203
Electron temperature and plasma density in coplanar alternating-current plasma display panels (AC-PDP's) have been experimentally investigated in accordance with discharge time by a micro-probe in this experiment. The resolution of a step mortor to move in micro-Langmuir probe is 10um.[1-3] The used gas in this experiment is He-Ne-Xe (4%) mixure gas. And sustain voltage is 320V which is above of firing voltage for degradation. The electron temperature and plasma density can be obtained from current-voltage (I-V) characteristics of micro Langmuir probe, in which negative to positive bias voltage was applied to the probe. And Efficiency is calculated by formula related discharge power and light emission. Those experiments operated as various discharge time ($0{\sim}72$ Hours). As a result of this experiment, Electron Temperature was increased from 2eV to 5eV after discharge running time of 20 hours and saturates beyond 20 hours. The plasma density is inversely proportional to the square root of electron temperature. So the plasma density was decreased from$1.8{\times}10^{12}cm^{-3}$ to$8{\times}10^{11}cm^{-3}$ at above discharge running time. And the Efficiency was reduced to 70% at 60hours of discharge running time. -
Lee, Soo-Beom;Jeoung, J.M.;Ko, B.D.;Oh, P.Y.;Moon, M.W.;Lee, J.H.;Lim, J.E.;Lee, H.J.;Han, Y.G.;Yoo, N.L.;Jeoung, S.H.;Son, C.G.;Choi, E.H. 1207
The MgO protective layer provides protection from the discharge, lowers the discharge voltage and prolongs the AC-PDP lifetime. We have investigated the characteristics of degradation of MgO protective layer, which correlates to the image-sticking[1] and the lifetime in AC-PDP. The degraded MgO have been changed the surface morphology of MgO. It was found that panel lifetime depended on degradation of MgO protective. -
Son, Chang-Gil;Lee, H.J.;Jung, J.C.;Park, W.B.;Moon, M.W.;Oh, P.Y.;Jeong, J.M.;Ko, B.D.;Lee, J.H.;Lim, J.E.;Han, Y.G.;Lee, S.B.;Yoo, N.L.;Jeong, S.H.;Choi, E.H. 1211
One of the important problems in recent AC-PDP technology is high efficiency. In this research, we have been investigated electro-optical characteristics of MgO protective layer after radio frequency(RF) plasma treatment using Ar,$O_2$ , and$H_2$ gases. The breakdown voltage order was$O_2$ > Ar > Nontreatment >$H_2$ . Also, brightness order was$O_2$ > Ar > Non-treatment >$H_2$ . In this experiment, the best result was obtained after$O_2-plasma$ treatment. -
Jeoung, Jin-Man;OH, P.Y.;Moon, M.W.;Lee, J.H.;Jeong, J.E.;Lee, H.J.;Han, Y.K.;Lee, S.B.;Jeong, S.H.;Yoo, C.K.;Yoo, N.R.;Choi, E.H.;Ko, B.D. 1215
One of the important problems in recent AC-PDP technology is the image sticking. In this research, we have investigated the PDP cell with constraint deposition MgO on phosphor, the electrical and optical properties in the PDP cell were examined. Also, we have investigated the correlation with image sticking and degraded MgO protective layer, phosphor in AC-PDP. As a result, we measured the secondary electron emission coefficient${\gamma}$ , discharge characteristics and Brightness for the constraint degraded phosphor are compared with those of nondegraded phosphor. -
We have developed laser absorption spectroscopy system for the measurement of excited Xe atoms in micro-discharged AC-PDP plasma. In this study, we have measured the absorption signals for the
$1S_5$ xenon metastable state in the PDP cell with the various gas mixtures of Ne-Xe(1%), Ne-Xe(4%) and Ne-Xe(10%) under fixed gas pressure of 350 Torr and the eletrode gap distance of 50um. It is found that the maximum excited xenon densities are$1.2^{\ast}10^{12}\;cm^{-3}$ ,$1.8^{\ast}10^{12}\;cm^{-3}$ and$2.7^{\ast}10^{12}cm^{-3}$ for gas mixtures of Ne-Xe(1%), Ne-Xe(4%) and Ne-Xe(10%) respectively, in this experiment. -
Yoo, N.L.;Jung, K.B.;Lee, J.H.;Lee, S.B.;Han, Y.K.;Jeong, S.H.;Lee, H.J.;Son, C.G.;Lim, J.E.;Oh, P.Y.;Moon, M.W.;Jeoung, J.M.;Ko, B.D.;Cho, G.S.;Uhm, H.S.;Choi, E.H. 1221
The improvement of luminance and luminous efficiency is the one of the most important parts in AC-PDPs. To achieve high luminance and luminous efficiency, high VUV emission efficiency is needed. We measured the emission spectra of the vacuum ultraviolet(VUV) rays in surface discharge AC-PDP with ternary gas mixture of 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. For improving discharge luminous efficiency, we have studied VUV emission characteristics of ternary gas mixture, He(50%)-Ne-Xe and He(70%)-Ne-Xe with Xe concentration and filling gas pressure. -
Barrier ribs in the plasma display panel(PDP) function to maintain the discharge space between the glass plates as well as to prevent optical crosstalk. Patterning of barrier ribs is one of unique processes for making PDP. In this work photosensitive barrier rib pastes were prepared by incorporating binder polymer, solvent, functional monomers photoinitiator, and barrier rib powder of which surface was treated with fumed silica particles. Study on the function of materials for the barrier rib paste were undertaken. After optimization of paste formulation and photolithographic process, it was found that photolithographic patterning of barrier ribs with photosensitive barrier rib green sheet could be used in the fabrication of high resolution PDP.
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We report the method of preventing the grey color of Bi based glass frits caused by reduction of
$Bi_2O_3$ . To prevent reduction of$Bi_2O_3$ , we controlled the melting temperature. Low melting temperature reduces the reduction of$Bi_2O_3$ and that makes clarity transparent glass cullets. After firing, glass frits that melted at lower temperature showed better transparency. To prevent the browning, we used some additives like CuO,$CeO_2$ , CoO and$TiO_2$ . The colors of glass cullets were varied according to additives. After firing, dielectric layer contained additives showed better transparency than the one without additives. In the point of reaction between dielectric layer and Ag electrode, CuO was the most effective additive in preventing the yellowing. -
We report a novel approach for encapsulating of cathode electrodes in DC plasma pixels. Anode and cathode electrodes are laterally placed on a single substrate. The encapsulated electrode minimizes the sputtering of the cathode without significantly altering the turn-on voltage-pressure characteristics. An abnormal glow in current-voltage characteristics is also observed.
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The effects of various sustain waveforms on the discharge characteristics, such as discharge current waveform, IR waveform, luminance, luminous efficiency, power consumption, and static margin are investigated under high Xe (20%) gas mixture at 200 kHz. The four types of sustain waveforms, such as non-overlapped sustain waveform without auxiliary pulse, non-overlapped sustain waveform with auxiliary pulse, overlapped sustain waveform without auxiliary pulse, overlapped sustain waveform with auxiliary pulse, are examined intensively. As a result, the overlapped sustain waveform with auxiliary pulse shows the best discharge characteristics under high Xe (20%) gas mixture at 200 kHz.
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To prevent deformation and fracture of barrier ribs we suggest how to evaluate the mechanical properties of barrier ribs which depend on porosity and components by indentation technology. Our experimental results show that the mechanical properties of barrier ribs are strongly correlated to porosity and components.
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Glass frit was selected to be a
$Bi_2O_3-RO-R_2O_3$ system as a sealing material to replace the current PbO system in PDP. Fillers such as a zircon, cordierite and${\beta}-eucryptite$ were added for the control of thermal expansion coefficient (CTE), flowability and strength for sealing. At$450-500^{\circ}C$ , reaction of frit and filler and interface were evaluated by a flow button test and SEM observation. The composite (frit and filler) showed CTE in the range of 70-83 x$10^{-7}/K$ and flowability of 14-20mm. It can be a candidate for the replacement of PbO system. -
In PDP, a transparent dielectric is formed on a front glass substrate so as to cover bus electrodes (Ag). During the fabrication process, sometimes, a transparent dielectric reacts with bus (Ag) electrode in the range of
$560-600^{\circ}C$ , and the reaction gives the dielectric its yellow coloration, what is called "yellowing phenomena". In this paper, we investigated the reaction between bus electrode and transparent dielectric covered with different frit content in Ag paste. -
Recently, PDP barrier ribs require the formation of complex structure so that they are usually formed by etching method. For producing the fine ribs structure, during the etching process the metal ions of matrix (glass) of barrier materials should be understood on the etching mechanism with etching condition. We analyzed the quantity of Pb, Si, and B ions from the etch solution as a function of etching time.
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The increase of secondary electron-emitting coefficient is effective to reduce the discharge voltage as well as to improve the luminance efficiency of PDP. We investigated the properties of
${\gamma}$ with composition and different dielectric constants, and the microstructure of dielectric after ion collision. As a result the dielectric of PbO system showed higher${\gamma}$ compared with Pb-free system. However, there was no difference in${\gamma}$ when the MgO protective layer was covered. -
The ramp type bias voltage applied to the common electrode during a reset-period is newly proposed to lower the background luminance and to improve the address discharge characteristics in AC-PDP. The positive ramp bias voltage is applied during the ramp-up period, whereas the negative ramp bias voltage is applied during the ramp-down period. The effects of the voltage slopes in both the positive and negative ramp bias voltages on the background luminance and address voltage characteristics are examined intensively. It is observed that the optimized positive and negative ramp bias voltages applied to the common electrode during the ramp-period can lower the background luminance and also enhance the address discharge characteristics of the AC-PDP.
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The picture quality of a plasma display panel is very sensitive to the phosphor characteristics such as decay time, surface state, and even longevity of phosphor material in itself. In this work, material characteristics of
$Zn_2SiO_4:Mn$ ,$Y_2O_3-coated$ $Zn_2SiO_4:Mn$ , and$YBO_3:Tb$ , which are dominant in commercial application, were examined for investigating the aging characteristics of green PDP phosphors. It was found that$Y_2O_3-coated$ $Zn_2SiO_4:Mn$ are easily degraded at high temperature. However, all the samples were very weak after vacuum annealing. The luminescence intensity was decreased by order of one magnitude. -
The influence of the grooved dielectric layer on discharge and luminous characteristics has been investigated for various depths of the groove to achieve a high luminance efficiency AC-PDP operated at a lower voltage. We use the voltagethreshold curve technique and address delay jitters to explain the discharge characteristics. It shows that the surface discharge voltage rely on the depth of the grooved dielectric layer. Vertical discharge voltage remains almost the same as the groove depth increases. The influence of the grooved dielectric layer on discharge and luminous characteristics has been investigated for various depths of the groove to achieve a high luminance efficiency AC-PDP operated at a lower voltage. We use the voltagethreshold curve technique and address delay jitters to explain the discharge characteristics. It shows that the surface discharge voltage rely on the depth of the grooved dielectric layer. Vertical discharge voltage remains almost the same as the groove depth increases.
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We propose a simple and efficient driving algorithm to reduce Dynamic False Contour(DFC) in Plasma Display Panels(PDPs) by using both accumulation and combination of light emission periods. Although the accumulative way of light emission in sustain period is regarded as more effective than combinational way to reduce DFC, it takes much addressing time to express high gray-scale. Therefore, we combine accumulative and combinational light emission methods to reduce DFC. In the proposed method, one TV field (16.7ms) is composed of four combinational subfields for expressing small gray scales and fifteen accumulative subfields for large gray scales. In addition, we use some Graphic Signal Processing(GSP) algorithm to get more natural images by reducing DFC.
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The influence of oxygen plasma and octadecyltrichlorosilane (OTS) treatment of
$SiO_2$ on the patterning of poly(3,4-ethylenedioxythiophene)/poly(4-styrenesulfonate) (PEDOT:PSS) is presented. A significant difference in surface energies between plasma treated and OTS treated$SiO_2$ was noted. Such heterogeneous surface energy guides PEDOT:PSS to wet and spread on the wettable region and to dewet and retract from other regions. -
The long-term stability of pentacene thin-film transistors (TFTs) encapsulated with a transparent
$SnO_2$ thin-film prepared by ion beam assisted deposition (IBAD) was investigated. With a buffer layer of thermally evaporated 100 nm$SnO_2$ film deposited prior to IBAD process, our encapsulated OTFTs sustained its initial field-effect mobility up to one month and then gradually degraded showing only 37% reduction compared to 90% reduction of non-encapsulated OTFTs after 100 days in air ambient. The encapsulated OTFTs also exhibited superior on/off current ratio of over$10^5$ to that of the unprotected devices$({\sim}10^4)$ which was reduced from${\sim}10^6$ before aging. Therefore, the enhanced long-term stability of our encapsulated OTFTs should be attributed to well protection of permeation of$H_2O$ and$O_2$ into the devices by the IBAD$SnO_2$ thin-film which could be used as an effective inorganic gas barrier for transparent organic electronic devices. -
A novel zinc complex, Zn(phen)q, was synthesized from 1,10-phenanthroline (phen) and 8-hydroxyquinoline (q) as organic ligands and its electroluminescent (EL) properties were characterized. The structure of Zn(phen)q was elucidated by FT-IR, UV-Vis and XPS. The complex Zn(phen)q showed thermal stability up to
$300^{\circ}C$ under nitrogen flow, which was measured by TGA and DSC. The photoluminescence (PL) of the Zn(phen)q was measured from the THF solution and the solid film on quartz substrate. The PL emission of Zn(phen)q exhibited green light centered at about 505nm. The EL devices were fabricated by the vacuum deposition. The EL devices having the structure of ITO/a-NPD/Zn(phen)q/Li:Al were studied, where 4,4'-bis[N-(1-naphthyl)-N-phenylamino]biphenyl(a-NPD) used as a hole transport layer(HTL). a-NPD has high Tg of$96^{\circ}C$ and thus makes the device thermally stable. The EL emission of Zn(phen)q exhibited also green light centered at 532nm. -
Jung, Keum-Dong;Jin, Sung-Hun;Park, Chang-Bum;Shin, Hyung-Cheol;Park, Byung-Gook;Lee, Jong-Duk 1284
Peripheral pentacene region gives a significant influence on C-V characteristics of metal-oxide-pentacene capacitor structure. When the gate voltage goes toward negative, the effect of peripheral pentacene region becomes larger. Remaining gate DC bias constant and changing small signal frequency, the capacitance of peripheral pentacene changes along with frequency so that the total capacitance value also changes. The influence of peripheral pentacene region should be removed to measure accurate C-V characteristics, because it is hard to take into account the effect of the region quantitatively. After removing the influence of peripheral pentacene region, acceptor concentration, flat band voltage and depletion width of pentacene thin film are extracted from an accurate C-V curve as$1.58{\times}10^{17}cm^{-3}$ , -1.54 V and 39.4 nm, respectively. -
We report on the structural and electrical properties of amorphous Yttria-stabilized zirconia (YSZ) thin films which are the potential high-k gate dielectric material of organic thin film transistor (OTFT). To investigate the influence of the oxygen flow rate on the structural and electrical properties of the YSZ films, XRD, XPS, J-E, I-V were carried out in this work. Oxygen vacancies are expected to be the most predominant type of defect in metal-oxide dielectrics. The leakage current density decreased mainly because of the reduction of oxygen vacancies with increasing oxygen flow rate.
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Hybrid insulator pentacene thin film transistors (TFTs) were fabricated with thermally grown oxide and cross-linked polyvinylalcohol (PVA) including surface treatment by dilute ploymethylmethacrylate (PMMA) layers on
$n^+$ doped silicon wafer. Through the optimization of$SiO_2$ layer thickness in hybrid insulator structure, carrier mobility was increased to above 35 times than that of the TFT only with the gate insulator of$SiO_2$ at the same transverse electric field. The carrier mobility of 1.80$cm^2$ /V-s, subthreshold swing of 1.81 V/decade, and$I_{on}$ /$I_{off}$ current ratio > 1.10 ×$10^5$ were obtained at low bias (less than -30 V) condition. The result is one of the best reported performances of pentacne TFTs with hybrid insulator including cross-linked PVA material at low voltage operation. -
We have fabricated white organic light emitting diodes. To obtain balanced white emission and improve the efficiency of devices, thin electron blocking layer (TEBL) was inserted between the emitting layers. We showed that the effective injection of electrons through the optimization of TEBL (a - NPD) embodied the balance of spectra and had a possibility of getting white emission. In a device with 0.3 nm a-NPD, it had a maximum power efficiency of 3.80 lm/w at 250
$cd/m^2$ , a luminance of 1200$cd/m^2$ at 100$mA/cm^2$ , and the CIE coordinates were (0.353, 0.357). -
We propose a new pixel design for active matrix organic light emitting diode (AM-OLED) displays using hydrogenated amorphous silicon thin-film transistors (a-Si:H TFTs). The pixel circuit is composed of five TFTs and one capacitor, and employs only one additional control signal line. It is verified by SPICE simulation results that the proposed pixel compensates the threshold voltage shift of the a-Si:H TFTs and OLED.
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The performance of OTFT with
$PVP-TiO_2$ composite, as a gate insulator, is reported, including the effect of surfactant for synthesizing the composite material. According to our investigation results, it was one of critical issues to prevent the aggregation of$PVP-TiO_2$ particles during the synthesis process. From this point of view,$PVP-TiO_2$ particles were treated using Tween80, as a surfactant, and we could reduce the aggregated$PVP-TiO_2$ clusters. As a result, the OTFT with the composite insulator showed the threshold voltage of about -8.3 V and the subthreshold slope of about 1.5 V/decade, which are the optimized properties compared to those of OTFTs with bare PVP, in this study. It is thought that these characteristic improvements are originated from the increase in the dielectric constant of the PVP-based insulator by compositing with high-k particles. -
Kim, Young-Min;Lee, Joo-Won;Park, Jung-Soo;Kim, Jai-Kyeong;Sung, Man-Young;Ju, Byeong-Kwon;Jang, Jin 1306
Highly efficient and bright organic light-emitting diodes (OLEDs) have been realized using the thin alkali compound films (TACFs) at the interface between an emitting layer and an electron transporting layer with conventional organic layers. By comparing the performance of the device as a function of position with the TACFs, we propose the optimal position of the TACFs in the tris-(8-hydroxyquinoline) aluminum (Alq3). A device with the ACFs showed high luminance of over 12 500 cd/m2, luminance efficiency of more than 12 cd/A, and power efficiency of more 4.5 lm/W, respectively. -
Ryoo, Ki-Hyun;Lee, Cheon-An;Jin, Sung-Hun;Jung, Keum-Dong;Park, Chang-Bum;Lee, Jong-Duk;Shin, Hyung-Cheol;Park, Byung-Gook 1310
Passivation of organic thin-film transistors (OTFTs) using organic and metal thin-film was presented. Parylene-C and titanium were used as an organic and metal layer, respectively. With the proposed passivation method the degradation of electric parameters of OTFTs was relieved compared with non-passivated devices. Several electric parameters such as on/off current, field-effect mobility, and threshold voltage were shown. -
In the present paper, it was investigated that adhesion layer on gate insulator could affect the electrical characteristics for the organic thin film transistors (OTFTs). The polyimide (PI) as organic adhesion layer was fabricated by using the vapor deposition polymerization (VDP) processing . It was found that electrical characteristics improved comparing OTFTs using adhesion layer to another. We researched adhesion layer as a function of thickness. For inverted-staggered top contact structure, field effect mobility, threshold voltage, and on-off current ratio of OTFTs using adhesion layer of PI 15 nm thickness on the gate insulator with a thickness of 0.2
${\mu}m$ were about 0.5$cm^2/Vs$ , -0.8 V, and$10^6$ , respectively. -
Lee, Cheon-An;Jang, Kyoung-Chul;Kim, Sung-Won;Ryoo, Ki-Hyun;Jin, Sung-Hun;Lee, Jong-Duk;Shin, Hyung-Cheol;Park, Byung-Gook 1317
Bottom contact pentacene organic thin-film transistors are fabricated at three different substrate temperatures,$70^{\circ}C$ ,$80^{\circ}C$ and$90^{\circ}C$ . The maximum effective mobility was obtained at$80^{\circ}C$ . The contact resistance was extracted by applying two different methods, TLM method and channel-resistance method, and the value shows the minimum at$80^{\circ}C$ , which is thought to be the important reason for the best performance. -
Microcrystalline silicon films were deposited on glass substrate by using plasma-enhanced chemical vapor deposition (PECVD) method. The crystalline volume fraction was estimated by means of Raman spectrometer with argon laser as light source. The high hydrogen dilution of silane gas was used for increase in content of crystal silicon phase.
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The photoluminescence, electroluminescence and surface properties of ZnS:Cu,Cl phosphor coated by sol-gel process were studies. Na-silicate was used as precursor coating material. pH of solution and the concentration of Na-silicate are the important conditions to obtain the uniform coating on the phosphors. Also, the electroluminescent devices were made with Na-silicate coated phosphor. The spectroscopic characterization is performed by photospectrometer.
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The color shifting from yellow to green of electroluminescent emission from ZnS: Cu alternating current thick film electroluminescent (ACTFEL) devices has been achieved by changing the Mg composition in the phosphor layers. The commission international de l'Eclairge (CIE) color co-ordinates of the ACTFEL devices prepared from these phosphor layers show a shifting from yellow (x=0.45, y=0.52) towards green (x=0.36, y=0.58). The various parameters influencing the emission intensity were also investigated.
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A magnesium thiogallate phosphor doped with europium was prepared by solid-state method. This phosphor has green emission near 535 nm due to the allowed transition from
$4f^65d$ at an excitation state$(T_{2g})$ to$4f^7 (^8S_{7/2}) at a ground state of$Eu^{2+}$ ion. This phosphor shows a wide excitation spectrum from ultra violet (300 nm) to bluish green (515 nm). -
Orange-yellow phosphor has been synthesized by solid-state method for inorganic EL devices. Zinc sulfide is used as host material for the phosphor and the phosphor consists of copper and manganese as activators. The dependence of the photoluminescence (PL) and electroluminescence(EL) properties on the copper and manganese concentrations has been investigated.
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We have synthesized an
$Eu^{2+}$ -activated$Sr_3MgSi_2O_8$ blue phosphor and$Ba_2SiO_4$ green phosphor and$Ba^{2+}$ co-doped$Sr_3SiO_5$ red phosphor investigated an attempt to develop white LEDs by combining it with a GaN blue LED$chip(\lambda_{em}=405 nm)$ . Three distinct emission bands from the GaN-based LED and the$(Sr_3MgSi_2O_8:Eu\; +\; Ba_2SiO_4:Eu\; +\; Ba^{2+}\; co-doped\; Sr_3SiO_5:Eu)$ phosphor are clearly observed at 460nm, 520 nm and at around 600 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_2SiO_4:Eu\; +\; Ba^{2+}\; co-doped\; Sr_3SiO_5:Eu) exhibits a better luminous efficiency than that of the industrially available product InGaN (460 nm chip)-based YAG:Ce. -
Self assembled monolayers (SAM) are generally used at the anode/organic interface to enhance the carrier injection in organic light emitting devices, which improves the electroluminescence performance of organic devices. This paper reports the use of SAM of 1-decanethiol (H-S(CH2)9CH3) at the cathode/organic interface to enhance the electron injection process for organic light emitting devices. Aluminum (Al), tris-(8-hydroxyquionoline) aluminum (Alq3), N,N'-diphenyl-N,N'-bis(3 -methylphenyl)-1,1'- diphenyl-4,4'-diamine (TPD) and indium-tin-oxide (ITO) were used as bottom cathode, an emitting layer (EML), a hole-transporting layer (HTL) and a top anode, respectively. The results of the capacitancevoltage (C-V), current density -voltage (J-V) and brightness-voltage (B-V), luminance and quantum efficiency measurements show a considerable improvement of the device performance. The dipole moment associated with the SAM layer decreases the electron schottky barrier between the Al and the organic interface, which enhances the electron injection into the organic layer from Al cathode and a considerable improvement of the device performance is observed. The turn-on voltage of the fabricated device with SAM layer was reduced by 6V, the brightness of the device was increased by 5 times and the external quantum efficiency is increased by 0.051%.
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A modified Time-Ratio Gray Scale AMOLED drive technique is described in which the frame period is split into two half-frames, each of which is divided into binary weighted sub-frames and driven in the conventional time-ratio manner. The proposed technique improves aperture ratio by reducing TFT sizes in pixel circuits.
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We report on the photoalignment process of pentacene thin film with optical anisotropy on treated buffer layers. The photopolymer, showing an anchoring transition, was used as a buffer layer to control the structural order of the pentacene molecules. Using the photoelastic modulator, it was found that the grain size and the optical anisotropy of the pentacene thin film were strongly correlated with each other.
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We report the development frontiers that are dictating the speed of adoption of polymer organic light emitting diode (P-OLED) technology in market applications. Our presentation includes both the developments taking place in materials and the rapid advances in the manufacturing processes used for solution processable P-OLEDs. On the manufacturing side, the latest progress in ink jet printing process is discussed. On the materials side, we look at both fluorescent and phosphorescent material performance including the CDT development roadmap.
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Lee, Hun-Jung;Kim, Sung-Jin;Lee, Sang-Min;Ahn, Taek;Park, Young-Woo;Suh, Min-Chul;Mo, Yeon-Gon;Chung, Ho-Kyoon 1361
In this paper, we report on the performance stability of solution processible OTFT devices with Au/Ti and ITO source-drain (S/D) electrodes. It appears that the contact resistance of the S/D electrode strongly affects the stability of OTFT devices. Interestingly, the devices with the Au/Ti electrode showed lower mobility than those with the ITO (S/D) devices. The field effect mobilities of the devices with the Au/Ti and ITO electrodes were 0.06, and$0.44cm^2/Vs$ , respectively. However, the mobility of the device with the Au/Ti electrode was increased up to$0.26cm^2/Vs$ after 2 weeks, while the mobility of the device with ITO electrode was slightly decreased down to$0.41cm^2/Vs$ . The experimental data show us that ITO could be used as the S/D electrode for low-cost OTFT devices. -
So, Myeong-Seob;Suh, Min-Chul;Koo, Jae-Bon;Choi, Byoung-Deog;Choi, Dae-Chul;Lee, Hun-Jung;Mo, Yeon-Gon;Chung, Ho-Kyoon 1364
In this paper, we have identified the mechanism of C-V hysteresis behavior often observed in pentacene organic thin-film transistors (OTFTs). The capacitance-voltage (C-V) characteristics were measured for pentacene OTFTs fabricated on glass substrates with MoW as gate/source/drain electrode and TEOS$SiO_2$ as gate insulator. The measurements were made at room temperature and elevated temperatures. From the room temperature measurements, we found that the hysteresis behavior was caused by hole injection into the gate insulator from the pentacene semiconductor for large negative gate voltages, resulting in the negative flat-band voltage shift. However electron injection was observed only at elevated temperatures -
Oligothiophene derivatives have been wellknown as an p-type channel
$material.^1$ Here, we report novel oligothiophene derivative containing alkylene linkage as an p-type channel material. Oligothiophene derivative containing alkylene linkage BE4TH was synthesized and characterized. BE4TH was prepared by a palladium-catalyzed crosscoupling reaction via zinc-substituted thiophene. B4TH and BH4TH exhibited high thermal stability and at least one transition temperature. -
Chung, Sung-Mook;Hwang, Chi-Sun;Lee, Jeong-Ik;KoPark, Sang-hee;Yang, Yong-Suk;Do, Lee-Mi;Chu, Hye-Yong 1374
Top-emitting organic light-emitting diode (TEOLED) was fabricated on flexible substrate of PES film. Aluminum and Chromium multilayer was used as an anode of TEOLED and the TEOLEDs of Cr(20nm)/Al(100nm)/Cr(20nm)/NPB(60nm)/Alq(60nm)/LiF(1nm)/Al(2nm)/Ag(20nm)/NPB(200nm) has been fabricated on PES film and Si wafer for control device. The TEOLED on PES film which had good anode surface morphology, showed very similar device characteristics to that on Si wafer. -
The efficiency and the optical properties of the yellow organic light-emitting devices (OLEDs) were significantly affected by the existence of the multiple quantum well (MQW) structures consisting of N, N'- bis-(1-naphthyl)-N, N'-diphenyl-1,1-biphenyl-4,4'- diamine(NPB)/5,6,11,12 - tetraphenylnaphthacene (rubrene). The maximum efficiency and the luminance of OLEDs with 3-periods of the NPB/rubrene MQWs at 41.6
$mA/cm^2$ were 3.66 cd/A and 1524$cd/m^2$ , respectively, and their Commission Internationale de l'Eclairage chromaticity coordinates were (0.34, 0.55), which indicates a yellow color. These results indicate that the efficiencies of the OLEDs by using MQW emitting layers can be improved. -
We report improved efficiency in blue electrophosphorescent organic light emitting diodes by introducing an interfacial exciton blocking layer between light emitting layer (EML) and hole transport layer (HTL). Iridium(III) bis [(4,6-di-fluorophenyl)- pyridinato -N,C2']picolinate (FIrpic) was used as blue phosphorescent dopant and JHK6-3 with carbazole and electron transporting group as host and also as the interfacial layer, resulting in drastic increase in quantum efficiency.
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We synthesized new poly(p -phenylene vinylene) (PPV) derivatives including different portions of crosslink that could interconnect the backbone of PPV for application in optoelectronic devices such as lightemitting-diodes, photovoltaic cells, and lasers. The fluorescence and electroluminescence properties of PPV including crosslink were discussed with respect of their structure and length of crosslink unit.
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Cho, Sang-Mi;Han, Seung-Hoon;Kim, Jun-Hee;Lee, Sun-Hee;Choo, Dong-June;Uchiike, H.;Oh, Myung-Hwan;Jang, Jin 1386
We report the light illumination effect on the performance of pentacene organic thin-film transistor (OTFT). The TFT performance with and without illumination were measured at various temperatures. The off-state currents increase linearly with light intensity in the region of gate voltage where the holes are majority carriers in the TFT channel. The minimum photocurrents of OTFT increase with increasing light intensity. -
We fabricated an efficient top emission organic light emitting diode (FTEOLED) on paper substrates. For water proof and surface planarization, parylene of 5mm thick has been coated on copy paper substrate by vapor polymerization. As use this coating layer, fabrication of device was possible by photolithography and wet etching. Because paper is not transparent, we adapted top emission structure with transparent cathode and reflective anode. The FTOLED on paper showed the excellent electrical characteristic,
$109cd/m^2$ , 2.3cd/A at 10V. -
Hyundai LCD Inc. and LUXELL Technologies Inc. have jointly developed a 1.5" passive matrix full color OLED display (
$132{\times}RGB{\times}96$ , 111ppi) with characteristics of enhanced contrast ratio using black layer technology. This prototype ECR OLED was fabricated with the structure of ITO/HIL/HTL/RGB EML/HBL/ETL/LiF/Black Layer/Cathode and showed significant improvement of contrast ratio comparing with that of non-filtered OLED as well as compatible with circular polarizer OLED -
A novel data driver for passive matrix organic lightemitting devices (PM-OLEDs) with high gray scale images was designed. The proposed circuit consisted of a main current bias circuit as well as sample & hold circuits in each channel of the data driver to compensate a current offset. These results indicate that a data driver designed by using the current offset compensation technique holds promise for poten tial applications in PM-OLED displays with high gray scale images.
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We present that the carrier balance can be improved by doping a hole transport layer of 4,4'- bis[N-(1-napthyl)-N-phenyl-amino]-biphenyl (
${\alpha}$ -NPD) with a hole blocking material of 2,9-dimethyl- 4,7-diphenyl-1,10-phenanthroline (BCP). The doping leads to disturb hole transport, which can enhance the balance of electron s and holes concentration in the emitting layer, aluminum tris(8 -hydroxyquinoline) (Alq3), resulting in enhanced electroluminescence (EL) quantum efficiency for the device with the doped${\alpha}$ -NPD. -
We have fabricated organic light-emitting diodes using poly(N-vinylcarbazole)(PVK) doped with N,N'- diphenyl-N,N'-bis(3-methylphenyl)-[l,l'-biphenyl]- 4,4/-diamine (TPD) as the hole transport layer. TPD molecules act as the trapping sites in PVK and reduce the hole mobility, which can enhance the electronhole balance in the emitting layer, resulting in the enhanced device performance. We have found the optimum ratio of TPD to PVK for the EL efficiency.
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Organic light-emitting diodes (OLEDs) of metalsemiconductor-metal (MSM) structure have been fabricated by using m-MTDATA [4,4',4"-tris (3-methylphenylphenylamino) triphenylamine] as a hole-injection layer (HIL). The m-MTDATA is shown to be an effective hole-injecting material for the OLED, in that the insertion of m-MTDATA greatly reduces the roughness of anode surface and improves the device performance.
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We present that the electroluminescence (EL) efficiency can be improved by doping an electron transport layer (ETL) with organic materials which can make electron current increase. The electron transport layer of aluminum tris(8 -hydroxyquinoline) (Alq3) is doped with 2-(4-Biphenylyl)-5-(4-tertbutylphenyl)- 1,3,4-oxadiazole) (butyl-PBD) to enhance the electron mobility of the ETL. The higher quantum efficiency of device having ETL using Alq3 doped with butyl-PBD can be attributed to the improved electron and hole balance.
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The OTFT performance depends strongly on the interfacial properties between an organic semiconductor and
${\alpha}$ metal electrode. The contact resistance is critical to the current flow in the device. The contact resistance arises mainly from the Schottky barrier formation due to the work function difference between the semiconductor and electrodes. We doped pentacene/source-drain interfaces with$F_4TCNQ$ (2,3,5,6-Tetrafluoro-7,7,8,8-tetracyanoquinodimethane), resulting in p-doped region at the SD contacts, in order to solve this problem. We found that the mobility increased and the threshold voltage decreased. -
A new DCM derivative containing a phenothiazine moiety, 4-(dicyanomethylene)-2-t-butyl-6-(9-ethylphenothiazine-2- enyl)-4H-pyran (DCPTZ), has been synthesized as an orange-red fluorescent dye molecule for organic lightemitting diodes (OLEDs). EL devices with the structure of
$ITO/PEDOT-PSS/{\alpha}-NPD/Alq_3:DCPTZ/Alq_3/LiF/Al$ have been fabricated with changing the doping concentration of the DCPTZ. Maximum EL spectra of the devices ranged from$580{\sim}620$ nm depending on the doping concentration of the dye molecule. An EL device with 0.5 % doping concentration showed CIE coordinate (0.51, 0.47) at luminance of 100$cd/m^2$ . White light-emitting devices with the structure of$ITO/PEDOT-PSS/{\alpha}-NPD/{\alpha}-NPD:DCPTZ/DPVBi/Alq_3/$ LiF/Al have been also fabricated. The thickness of blue light-emitting 1,4-bis(2,2- diphenylvinyl)benzene (DPVBi) layer was changed to obtain a white light-emission. A white light-emission from the device was observed when the thickness of the DPVBi layer became thicker than 10 nm. -
We have synthesized a photo patternable blue lightemitting polyfluorene (PF) derivative containing cross-linkable oxetane units. Poly(9,9-bis-(4-octyloxyphenyl)- fluorene-2,7-diyl-alt-9,9-bis-((3-hexyloxy-3'- ethyl)-oxetane)-fluorene-2,7-diyl) has been synthesized by Suzuki coupling 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 UV/visible spectroscopy, photoluminescence and scanning electron microscope (SEM). We obtained fine patterns with 10 mm resolution using the polymer film after exposure and development. This patterning method using conjugated polymers can be applicable to make fine pixels for PLEDs and OFETs.
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A new light-emitting poly(p-phenylenevinylene) (PPV) derivative containing a polyhedral oligomeric silsequioxane (POSS-PPV) and its MEH-PPV copolymers, [Poly(POSSPV-co-MEHPV)]s, have been synthesized through the Gilch polymerization, and their light-emitting properties were investigated. The synthesized polymers were characterized by NMR, GPC, thermogravimetric and elemental analysis. The POSS-PPV and copolymers showed almost the same optical properties as the MEH-PPV, regardless of copolymer composition. The POSS-PPV and MEHPPV all showed their peak absorption at 505 and 496nm, and PL emission maxima at 578 and 581nm. POSSPPV showed higher PL quantum efficiency than the MEH-PPV. Synthesis, characterization and electroluminescent properties of the polymers will be presented.
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In this paper, we studied on the application of Organic Thin Film Transistors (OTFTs) to the active matrix organic light emitting diodes (AMOLED). We designed organic transistor based pixel circuits for AMOLED. The pixel circuit is consisted of two-transistor, one-capacitor and one-OLED. We report the simulation results of the pixel circuits that OLED current varied as the data line and scan line voltage. Also, we will describe the fabrication process of the Pentacene OTFTs arrays and the organic light emitting diodes. The driving results of the fabricated unit pixels and their 4x4 arrays are also presented.
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Organic molecular-beam deposition of Mg:Ag thin films with a low Mg concentration on tris (8-hydroxyquinolino) aluminum
$(Alq_3)$ layers at room temperature was performed to investigate the feasibility of using Mg:Ag thin films as cathode electrodes in organic light-emitting devices (OLEDs). The effective barrier height of the$Mg:Ag/Alq_3$ heterointerface, determined from current-voltage measurements, was as low as 0.23 eV. These results help improve understanding the electrical properties of the$Mg:Ag/Alq_3$ heterointerfaces in OLEDs. -
Kim, Mu-Gyeom;Kim, Sang-Yeol;Lee, Tae-Woo;Park, Sang-Hun;Park, Ju-Cheol;Park, Jong-Jin;Pu, Lyong-Sun 1432
We report failure mode observed in polymer EL blue devices, relating with life curve. The modes are analyzed by observing compositional and morphological variation using TEM-EDX, STM, and reverse engineering method as destructive ways, and also investigated mobility changes of hole and electron by measuring transient EL as a nondestructive way corresponding to life curve. We believe that the postulated failure modes in polymer EL devices can present right directions to obtain better performance, especially life time, of polymer devices in material and device structural designing points of view. -
A novel current-type data driver for active matrix organic light emitting diode (AMOLED) is proposed for current uniformity enhancement among its output channels. New architecture is composed of shadow DACs that precharge output stages, a single-real DAC that correct the output level to a real target current level and output stages that operate in 3 states of sampling, correcting and driving. Simulation results show that the proposed driving method and circuits improve the current uniformity among output channels of a current-type driver IC.
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We have fabricated vertical type organic thin film transistors (OTFTs) using organic semiconductor materials such as F16CuPc, NTCDA, PTCDI C-8 and C60. The layers of OTFT were fabricated by vacuum evaporation technique and spin casting method onto the Indium Tin Oxide (ITO) coated glass. I-V characteristics and on-off ratios of the fabricated OTFTs were investigated. In addition, we have fabricated light emitting transistor using MEH-PPV and then investigated EL electroluminescent properties.
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Jeong, Hee-Jin;Song, Young-Il;Choi, Ha-Kyu;Kim, Gil-Yong;Yu, Tong;Lim, Seong-Chu;Lee, Young-Hee 1443
We have synthesized thin multi-walled carbon nanotubes (t-MWCNTs) using a catalytic chemical vapor deposition (CCVD) method with FeMoMgO catalyst. The number of tube walls were 2${\sim}$ 6 with the corresponding diameters of 3${\sim}$ 6 nm. We obtained high production yield of over 3000 wt% compared to the weight of the supplied catalyst. These t-MWCNTs revealed the intermediate structural characteristics between single- and multi-walled carbon nanotubes (SWCNTs and MWCNTs). We have also characterized the field emission properties such as turn-on field and emission current, and current degradation from these t-MWCNTs together with SWCNTs and MWCNTs. -
Carbon nanotube field emission display devices were fabricated using screen printing techniques. The CNT pastes are composed of organic binder, CNT, and additive materials such as glass frit, silver or ITO powders. The change in mixing ratio of various organic binders in CNT paste varied the electron emission characteristics. With increasing the contents of additive materials in CNT paste, turn-on field were increased, leading to decrease in electron emission current. The post-treatment process in this study induced the vertical alignment of carbon nanotubes on glass, resulting in the improvement of electron emission uniformity.
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Park, Jae-Hong;Moon, Jin-San;Jeong, Jin-Soo;Yoo, Ji-Beom;Park, Chong-Yun;Nam, Joong- Woo;Park, Jong-Hwan;Choe, Deok-Hyeon 1451
We report effects of inorganic binder on the emission properties of CNT paste for low cost and high low-cost and large area field emission devices or displays. Two types of photosensitive carbon nanotube (CNT) paste were formulated by using of glass frit and spin on glass (SOG) as an inorganic binder and investigated their emission properties according to inorganic binders and firing conditions. -
Kim, Do-Yoon;Yoo, Ji-Beom;Berdinski, A.S.;Han, In-Taek;Kim, Ha-Jong;Jin, Yong-Wan;Kim, Jong-Min 1455
We studied the density control of carbon nanotubes (CNTs) which were grown on the iron nanoparticles prepared from iron-acetate$[Fe(II)(CH_3COO)_2]$ solution using freeze-dry method. The density of CNTs was controlled for the enhancement of field emission. The patterning process of iron-acetate catalyst-layer for the fabrication of electronic device was simply achieved by using alkaline solution, TMAH (tetramethylammonium hydroxide). We applied this patterning process of catalyst layer to formation of the electron emitter with under-gate type triode structure. -
Carbon nanotube -copper composite structures were fabricated using composite plating method and their field emission characteristics were investigated. Multi-walled carbon nanotubes synthesized by chemical vapor deposition were used in the present study. It was revealed that turn-on field of the structures was about 3.0
$V/{\mu}m$ at the current density of 0.1${\mu}A/cm^2$ . We observed relatively uniform emission characteristics as well as stable emission currents. CNT-Cu composite plating method is efficient and it has no intrinsic limit on the plating area. Moreover, it gives strong adhesion between emitters and an electrode. The refore, we expect that CNT-Cu composite plating method can be applied to fabricate electron field emitters for large area FEDs and large area vacuum lighting sources. -
Han, Jae-Hee;Lee, Su-Hong;Berdinsky, Alexander S.;Yoo, Ji-Beom;Park, Chong-Yun;Choi, Jin-Ju;Jung, Tae-Won;Han, In-Taek;Kim, Jong-Min 1462
In this report, the FE characteristics of carbon nanotubes (CNTs) treated using both thermal annealing and mechanical coatings on the as-grown CNTs system atically studied. It was found that in the high temperature annealed samples, CNTs were attacked at its root during annealing due to a small amount of oxygen, and were pulled out of the substrate in places after FE measurements because of the contact resistance. However, for the mechanically coated samples both with spin on glass (SOG) and polymethyl methacrylate (PMMA), CNTs were found to be nearly intact after FE measurements and showed reliable FE characteristics over repeatable voltage scan. The reliability of CNTs during FE could be owing to the strong adhesion of CNTs to the substrate both by SOG and PMMA coatings. -
Park, J.H.;Moon, J.S.;Jeong, J.S.;Yoo, J.B.;Park, C.Y.;Moon, H.S.;Nam, J.W.;Kim, J.M.;Park, J.H.;Choe, D.H. 1466
We report effects of electrical aging on the emission stability of carbon nanotube (CNT) paste for low cost and high low-cost and large area field emission devices or displays. Photosensitive carbon nanotube paste was formulated by using of spin on glass (SOG) as an inorganic binder and investigated emission properties and stability depending on electrical aging condition. -
Noh, Hyung-Wook;Jun, Pil-Goo;Ko, Sung-Woo;Kwak, Byung-Hwak;Park, Sang-Sik;Lee, Jong-Duk;Uh, Hyung-Soo 1470
We proposed new triode-type Field Emitter Arays using Carbon NanoTubes(CNT-FEAs) as electron emission sources at low electric fields. The CNTs were selectively grown on the patterned catalyst layer by Plasma-Enhanced Chemical Vapor Deposition (PECVD). In this structure, gate electrodes are located underneath the cathode electrodes and extracted gate is surrounded by CNT emitters. Furthermore, in order to control density of CNTs, we investigated effect of using rapid thermal annealing (RTA). -
ZnO:Al(AZO) has been investigated for the photovoltaic cell or TCO(Transparent Conductive Oxide) of the display, because it has good electrical and optical properties. In this study, the ZnO:Al(AZO) thin film prepared on variation of substrate temperature by FTS(Facing Targets Sputtering) system. In case of TCO, because resistivity and roughness values affect the lighting of the OLED, their factors are very important. Therefore, in this paper, the electrical and optical properties of the AZO thin film were investigated with the deposition conditions and its roughness was investigated on variation of the substrate temperature. In results, AZO thin film deposited with the transmittance over 80% and the resistivity was reduced from
$1.36{\times}10^{-3}$ [O-cm] to$4{\times}10^{-4}$ [O-cm] with increasing the substrate temperature from R.T to$200[^{\circ}C]$ . Especially, we could obtain the resistivity$4{\times}10^{-4}$ [O-cm] of AZO thin film prepared at working pressure 1[mTorr], input current 0.4[A] and substrate temperature$200[^{\circ}C]$ . -
In this work, the ITO thin films were prepared by FTS (Facing Targets Sputtering) system under different sputtering conditions which were varying
$O_2$ gas flow, input current at room temperature. As a function of sputtering conditions, electrical and optical properties of prepared ITO thin films were measured. The electrical, optical characteristics and surface roughness of prepared ITO thin films were measured. In the results, as increasing$O_2$ gas 0.1[sccm] to 0.7[sccm], resistivity of ITO thin film was increased with a decreasing carrier concentration,$O_2$ gas over 0.3[sccm] the carrier mobility have a similarly value. Transmittance of prepared ITO thin films were improved at increasing$O_2$ gas 0.1[sccm] to 0.7[sccm]. And transmittance of all of the prepared ITO thin films was over 80%. We could obtain resistivity$6.19{\times}10^{-4}[{\omega}{\cdot}cm]$ , carrier mobility$22.9[cm^2/V{\cdot}sec]$ , carrier concentration$4.41{\times}10^{20}[cm^{-3}]$ and transmittance over 80% of ITO thin film prepared at working pressure 1mTorr, input current 0.4A without any substrate heating. -
Thin composite film passivation through RF sputtering method For Large-sized Organic Display DevicesLee, Joo-Won;Kim, Young-Min;Park, Jung-Soo;Bea, Sung-Jin;Kim, Na-Rae;Kim, Jai-Kyeong;Jang, Jin;Ju, Byeong-Kwon 1480
Transparent thin composite films (TCFs) were deposited on OLED devices by means of RF sputtering method and their passivation-properties were evaluated by comparing to the e-beam evaporating method. This composite film formed by mixed ratio of MgO (3wt %):$SiO_2$ (1wt %) was developed from pallet as a source of e-beam evaporator to 6-inch size target for sputtering in order to apply for large-sized organic display devices. Water Vapor Transmission Rates (WVTR) of the deposited films were measured as a function of thickness to assess the effectiveness of this film as a passivation layer and it applied to real devices. From this study, we can confirm that the passivation layer formed by TCFs using RF sputtering method sufficiently shows the potentiality of application to passivation layer for organic display devices. -
To achieve the high reliability performance in IPS cell, finding a good combination of Liquid Crystal (LC) materials and Polyimide (PI) is very important as they play a key role in IPS cell. Several LC materials and PIs have been introduced for preparation of their different combinations. Electro optical characteristics such as voltage holding ratio, residual DC and AC image sticking have been investigated for the different system of the LC material and PI in the test panels in an attempt to find the effects on the display reliability performance and image sticking.1)3)
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This study proposes a controller with the techniqu e of voltage -compensated driver for producing grayscaled pictures on passive matrix organic light emitting diodes (PMOLEDs) panels; especially, the controller overcomes the problem of luminance nonuniformity on displaying pictures. Because the controller is a voltage type driver, the output impedance of the driver is much less than that of the current-type driver. Hence, the controller provides a better electron-optical response than those of traditional current drivers. An area compensated look-up table (ACLUT) is designed in data feeding paths for removing luminance non-uniformity; thus, the proposed controller provides nearly 95% luminance uniformity.
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We have studied ink-jet printing method for patterning conductive line on flexible plastic substrates. Synthesized silver nano-particles of
${\sim}$ 20nm were used for the conductive ink and the printed patterns exhibit a smooth line whose linewidth is below 100${\mu}m$ . This ink-jet printing technique can be applied to flexible displays and electronics. -
Due to an efficient red emission,
$Eu^{+3}$ ions have doped in various host materials. Eu-doped$LaPO_4/LaPO_4$ core/shell nanophosphor which emits red light in visible range, was synthesized by using a solution system. The mean size of the nanoparticle observed by TEM was about 7-8 nm. In this core/shell system, the thickness of$LaPO_4$ shell was optimized on the basis of relative PL emission intensity. In addition, the luminescent properties of$LaPO_4:Eu/LaPO_4$ core/shell particle have been compared with Eu-doped$LaPO_4$ bulk particle and nanoparticle. -
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. This$BaMgAl_{10}O_{17}:Eu^{2+}$ particles prepared by the spray pyrolysis have shown the stronger emission intensity compared to the commercially-available$BaMgAl_{10}O_{17}:Eu^{2+}$ . However, thermal stability of the BAM:Eu b lue phosphor is very poor due to changing from$Eu^{2+}$ to$Eu^{3+}$ at the thermal process, so brightness of the phosphor decreases. To improve the thermal stability of the dense BAM:Eu phosphor, the spherical BAM:Eu particles were coated with pure$BaMgAl_{10}O_{17}$ layer using the hydrolysis reaction in a solution system. The synthesized powders were characterized by XRD, SEM and PL. On the other hand, the emission properties of the BAM:Eu phosphors coated with$BaMgAl_{10}O_{17}$ layer before and after thermal treatment at$500^{\circ}C$ for 30 min were estimated under VUV excitation. The brightness of the coated phosphor was higher than that of the uncoated phosphor. Also, the coating thickness of BAM layer in the BAM:Eu particles was optimized. -
This dissertation represents method concerning high performance prism LGP design in 17 inch TFT-LCD. By means of developing LGP with total size of 8mm that has prism on both upper side and bottom side, it is superior to previous printing way in gaining high brightness. It can realize actual material simulation on prism LGP production using 17inch injection process and about 20% luminance enhancement is achieved based on such method.
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LCD(Liquid Crystal Display) products is needed to have high reliability and are produced without harmful material. Because Substitution for CCFL of Light source used to Conventional backlight unit, research is going about product with LED of light source at present. In this experiment, We made the LED backlight unit with high quality for automotivenavigation. This backlight unit has center luminance of 6500 nit at15W power consumption. We adjusted chromaticity by using ten Blue LED and eight side emitting type White LEDs with high power LED from Lumileds company.
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The luminescent properties of
$Eu^{3+}$ and$Sm^{3+}$ doped potassium tungstate phosphor were investigated. The$K_{4-3x}(WO_4)_2:Eu_x$ ,$Sm_y$ phosphor was produced by firing the mixed precursors, followed by re-firing with a flux. The re-firing process provided the clean surface to the particles. The excitation spectra showed that the strong absorption in the region of ultra violet light occurred due to the high europium doping concentration. The incorporation of europium to potassium tungstate was easier, compared to other host materials. The excitation spectra could be controlled by the small addition of samarium. The increase of energy absorption around 405nm was assigned to the$Sm^{3+}$ ions. The comparison between real x-ray diffraction and simulated one revealed that the crystal structure of$K_{4-3x}(WO_4)_2:Eu_x,Sm_y$ phosphor is monoclinic with a space group, C2/c. -
The
$(Y,Gd)BO_3:Eu^{3+}$ phosphor was made by coprecipitation method. The precipitated powders were amorphous. The value of pH in the process of coprecipitation was critical for the luminescence of phosphors. The particle size and morphology were influenced by pH value. The lower calcination temperature and hydrothermal synthesis leads to the distortion of lattices. The distorted lattices changed the symmetry of$Eu^{3+}$ site. The broken inversion symmetry in the distorted lattice caused the increased emission of$^5D_0{\rightarrow}^7D_2$ transition. -
A cinnamate group is a well-known compound group used in the dimerization reaction by ultraviolet irradiation, and cinnamate polymers are studied as photoalignment materials. In this study, the radical reaction of cinnamate side groups attached to a flexible polymer backbone is considered feasible using thermal energy. To induce the thermal reaction of cinnamate side groups, we modified the flexibility of poly(vinyl cinnamate) by introducing a plasticizer into the polymers and investigated the thermal reaction behavior of cinnamate side groups. The plasticization of poly(vinyl cinnamate) makes the induction of the thermal reaction of cinnamate side groups easier than that of unmodified poly(vinyl cinnamate). The thermal reaction of cinnamate side groups is closely related to the enhancement of the thermal stability of the liquid crystal orientation of polymer films with polarized UV irradiation.
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$CaZrO_3:Tb$ as a new green-emitting phosphor, has been synthesized by solid state reaction. Photoluminescence and cathodoluminescence properties for the phosphor with a Perovskite structure were investigated. The$CaZrO_3:Tb$ phosphor, which has several emission peaks due to energy transfer from$^5D_4$ to$^7F_J(J=6,5,4,3)$ of$Tb^{3+}$ ion, exhibited strong green luminescence with the main emission peak centered at 545 nm. Optimum Tb concentration was 0.02mol%. -
Zinc oxide films have been actively investigated as transparent electrode materials for display. We report the effect of the working pressures on electro-optical properties of Al-doped ZnO thin films deposited by d.c. magnetron sputtering. The resistivity of the ZnO thin films was depended on atomic bombardment effect by working pressure.
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Jung, Yong-Jun;Park, Jae-Hong;Jeong, Jin-Soo;Nam, Joong-Woo;Berdinsky, Alexander S.;Yoo, Ji-Beom;Park, Chong-Yun 1530
We investigated under-gate type carbon nanotube field emitter arrays (FEAs) for back light unit (BLU) in liquid crystal display (LCD). Gate oxide was formed by wet etching of ITO coated glass substrate instead of depositing$SiO_2$ on the glass substrate. Wet etching is easer and simpler than depositing and etching of thick gate oxide to isolate the gate metal from cathode electrode in triode. Field emission characteristic s of triode structure were measured. The maximum current density of 92.5${\mu}A/cm^2$ was when the gate and anode voltage was 95 and 2500 V, respectively at the anode-cathode spacing of 1500${\mu}m$ . -
Ting, Chu-Chi;Cheng, Hao-Ping;Hsieh, Yu-Heng;Sun, Oliver;Chen, San-Yuan;Lin, Chin-Ching;Kuo, Kuan-Ting;Lee, Shu-Ping 1534
Highly luminescent efficiency phosphors have been successfully produced by surface modification and microwave irradiation treatment. The SEM image and XRD analysis reveal that the surface morphology of the white-light phosphors can be notably modified by microwave irradiation and exhibit with better crystalline property. The VUV PL spectra show that the microwave irradiation treatment can effectively enhance the luminescent efficiency by a factor of 1.5 times for intensity compared to that without microwave treatment. A further improvement in all visible emission can be made by modifying surface composition through MgO coating on the phosphor powder. These results demonstrate that such a simple approach can provide for improving luminescent efficiency of phosphors for the optoelectronic devices. -
We have made point electron sources using carbon nanotubes (CNTs). For the fabrication of point electron sources, CNTs were dispersed in a solution and attached on electrochemically etched W tips using electrophoresis. In our study, we have utilized various CNTs such as single-walled CNT (SWCNT), multiwalled CNT (MWCNT), and thin-MWCNT and threshold current, turn-on voltage, filed enhancement factor of each emitter have been studied upon a tube/bundle diameter and length. In addition, fieldemitted electron energy distribution of various CNT emitters is characterized.
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For reliability evaluation of AC-PDP, one of the most important factor is sealing property. In this paper, the reliability evaluation test method of the commercialized sealing glass frit in AC-PDP was studied. 6 inch AC-PDP panels were tested for evaluation of sealing glass frit by vibration shock test, thermal shock test, non -destructive X-ray inspection, residual stress inspection and residual gas detection. These test methods are proposed as a standard for testing the reliability of sealing glass frit. The main failure mode of sealing glass frit in AC-PDP seems to be the crack propagation from thermal cycling rather than mechanical factor.
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Transparent conducting aluminum-doped zinc oxide (AZO) thin films have been deposited on corning 1737 glass by DC magnetron sputter. The structural, electrical and optical properties of the films were investigated as a function of various substrate temperatures. AZO thin films were fabricated by dc magnetron sputtering with AZO ceramic target
$(Al_2O_3: 2wt %)$ . The obtained films were poly crystalline with a hexagonal wurtzite structure and preferentially oriented in the (002) crystallographic direction. The lowest resistivity is$6.0{\times}10^{-4}$ Ocm with the carrier concentration of$2.694{\times}10^{20}\;cm^{-3}$ and Hall mobility of$20.426cm^2/Vs$ . The average transmittance in the visible range was above 90%. -
Al-doped ZnO (ZnO:Al) thin films were grown on corning 1737 glass substrates by dc magnetron sputtering. The structural, electrical and optical properties of the films were investigated as a function of various discharge power. The obtained films were polycrystalline with a hexagonal wurtzite structure and preferentially oriented in the (002) crystallographic direction. The lowest resistivity is
$6.0{\times}10^{-4}$ Ocm with the carrier concentration of$2.694{\times}10^{20}$ $cm^{-3}$ and Hall mobility of$20.426cm^2/Vs$ . The average transmittance in the visible range was above 90%. -
Lee, Ki-Chan;Park, Yun-Jae;Ko, Hyun-Seok;Moon, Seung-Hwan;Park, Jin-Hyeok;Berkeley, Brian;Kim, Sang-Soo 1550
In this paper, to improve the well-known photo conductivity degradation of amorphous silicon, a new LASER immersion treatment has been applied. The optical feedback control LED backlighting system with integrated LCD panel sensor increased the color variation less than 0.008${\Delta}u'v'$ compared to 0.025 for a non-feedback system. -
We have studied the inkjet patterning of synthesized aqueous silver nano-sol on interface-controlled ITO glass substrate. Furthermore, we designed the conductive ink for direct inkjet patterning on bare ITO glass substrate. The first, 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. The high concentration of batch-synthesized silver nano sol was possible to 40 wt%. At the same time the particle size of silver nanoparticles was below
$10{\sim}20nm$ . The second, the synthesized silver nano sol was inkjet - patterned on ITO glass substrate. The connectivity and width of fine line depended largely on the wettability of silver nano sol on ITO glass substrate, which was controlled by surfactant. The relationship was understood by wetting angle. The fine line of silver electrode as fine as$50{\sim}100\;{\mu}m$ was successfully formed on ITO glass substrate. The last, the direct inkjet-patternable silver nano sol on bare ITO glass substrate was designed also. -
Lee, Sung-Ho;Jung, Sang-Kooun;Hur, Young-June;Lee, Do-Kyung;Park, Duck-Kyu;Park, Lee-Soon;Sohn, Sang-Ho 1556
Indium-tin oxide (ITO) films were deposited by a low-frequency (LF, 100 Hz) magnetron sputtering on glass substrates at the room temperature. The effects of the film thickness on the structural, electrical and optical properties of ITO films were investigated. With the film thickness the films reveal better crystallinity, showing both (222) and (400) pla nes in the XRD pattern. The optical transmittance and the sheet resistance of the films decreased with the increasing thickness. In addition, the electrical properties of ITO films were improved after annealing in a vacuum. -
Jung, Sang-Kooun;Lee, Sung-Ho;Kim, Myung-Chan;Lee, Do-Kyung;Cho, Yong;Park, Duck-Kyu;Sohn, Sang-Ho 1560
In this study, we introduce indium tin oxide (ITO) thin films grown by using a low-frequency magnetron sputtering method (LFMSM). Characteristics of the ITO thin films deposited on polyethersulfone (PES) and polyethylene terephthalate (PET) substrates are investigated. Experiments were carried out as a function of deposition time. ITO thin films on polymer substrates revealed amorphous structure. The optical, the electrical and structural properties of the films on PES substrate are better than those on PET substrates. -
ParkKo, Sang-Hee;Hwang, Chi-Sun;Kwack, Ho-Sang;Kang, Seung-Youl;Lee, Jin-Hong;Chu, Hye-Yong;Lee, Yong-Eui 1564
Zinc oxide thin films were grown at the t emperature of$100^{\circ}C$ and$150^{\circ}C$ by means of plasma enhanced atomic layer deposition (PEALD) and conventional atomic layer deposition for applying to the transparent thin film transistor (TTFT). The growth rate of$1.9{\AA}/cycle$ with oxygen plasma is similar to that of film grown with water. While the sheet resistivity of ZnO grown with water is 1233 ohm/sq, that of film grown with oxygen plasma was too high to measure with 4 point probe and hall measurement system. The resistivity of the films grown with oxygen plasma estimated to be$10^6$ times larger than that of the films grown with water. The difference of electrical property between two films was caused by the O/Zn atomic ratio. We fabricated ZnO-TFT by means of ALD for the first time and the ZnO channel fabricated with water showed saturation mobility of$0.398cm^2/V{\cdot}s$ with bottom gate configuration. -
We have evaluated thermal stability of a
$BaAl_2Si_2O_8:Eu^{2+}$ $(BAS:Eu^{2+})$ , which have polymorph property such as hexagonal, monoclinic structure depending upon firing temperature. When both polymorph$BAS:Eu^{2+}$ were baked in air at 500$^{\circ}C$ for 30 min, the photoluminescence (PL) intensity of$monoclinic-BAS:Eu^{2+}$ was maintained of the initial intensity. However, the PL intensity of$hexagonal-BAS:Eu^{2+}$ decreased significantly, corresponding to about 34 %. From analyses of Rietveld refinement, the difference of thermal stability of both$BAS:Eu^{2+}$ can be ascribed to both crystal structure of host materials and the average interatomic distances between$Eu^{2+}$ ion and oxygen their crystal structure which plays a key role of shield for Eu2+ ions against oxidation atmosphere. -
Myoung, Hey-J;Kim, Chul-A;You, In-Kyu;Kang, Seung-Y;Ahn, Seong-D;Kim, Gi-H;Oh, ji-young;Baek, Kyu-Ha;Suh, Kyung-S;Chin, In-Joo 1572
Poly(vinyl phenol)(PVP)/$TiO_2$ nanocomposite the films have been prepared incorporating metal alkoxide with vinyl polymer to obtain high dielectric constant gate insulating material for a organic thin film transistor. The surface composition, the morphology, and the thermal and electrical properties of the hybrid nanocomposite films were observed by ESCA, scanning electron microscopy (SEM), atomic force microscopy(AFM), and thermogravimetric analysis (TGA). Thin hybrid films exhibit much higher dielectric constants (7.79 at 40wt% metal alkoxide). -
With varying rapid thermal annealing (RTA) temperature, luminescence properties of
$Zn_{0.75}Mg_{0.25}S:Mn$ thin film deposited by RF-magnetron sputtering technique were investigated. In this study,$Zn_{0.75}Mg_{0.25}S:Mn$ thin film phosphor showed more red emission than those of the previous studies when annealed around 600 or$650^{\circ}C$ . Although all samples were deposited from identical source composition, a main peak wavelength of photoluminescence spectra of$Zn_{0.75}Mg_{0.25}S:Mn$ shifted toward shorter wavelengths depending upon increase of RTA temperature. The same dependence of wavelength on RTA temperature was also observed in cathodoluminescence as well as electroluminescence measurements. It was revealed that the change of the luminescence properties were originated from structural changes in$Zn_{0.75}Mg_{0.25}S:Mn$ thin film phosphor from cubic to hexagonal phases analyze using conventional X-ray pole figure mapping. The phase transition would be the origin of luminescence property changes with respect to RTA temperature. -
We report simple new techniques to express analysis of display materials. Colour Cathodoluminescence combined with scanning electron microscopy and spectroscopy is a powerful, non-destructive, high-resolution method for investigation luminescent materials. Some applications of this method to powder phosphors used in display are demonstrated.
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Although the picture quality of today's displays is very good already, a continuous improvement is desirable as the new larger display sizes increase the visibility of artifacts. A contributing factor for picture quality enhancement through smart video processing and algorithm design is the information gathered from video statistics. Interesting parameters gathered from video statistics are e.g. the image- and display load, the usage of the color gamut, the estimated power consumption and the occurrence of static image parts. Examples of applications that can benefit from video statistics are power calculations, color gamut mapping algorithms, dynamic backlight control for LCD panels and LED backlights for LCD panels.
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In this paper, we propose novel computational reconstruction technique of three-dimensional objects in integral imaging by use of a lenslet array. We applied our technique to two different integral imaging systems according the distance between lenslet array and elemental image plane. Experimental results are presented and discussed as well.
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LCDs with an additional white sub-pixel (RGBW LCDs) have been developed mainly to achieve higher panel transmittance. However this RGBW pixel structure causes the perceptual color difference between RGBW and RGB LCDs due to decreased primary color luminance. To solve this problem, we proposed and developed RGBW conversion algorithms that function adaptively as a displayed image changes. The test results show that the perceptual color difference could be solved to some degree by applying these new algorithms.
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Integral imaging attracts much attention as an autostereoscopic three-dimensional (3D) display technique for its many advantages. Recently the method that uses a curved lens array with a curved screen has been reported to overcome the limitation of viewing angle in integral imaging. This method widens the viewing angle remarkably. However, to understand the proposed system we need to know how the depth is limited in the proposed method also. We analyze the depth limitation and show the simulation results.
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In a three-dimensional/two-dimensional convertible parallax barrier display, an additional layer compensating the color dispersion for three-dimensional display can distort displayed image in the two-dimensional mode. We analyze the effect of the color dispersion compensating layer on two-dimensional image by computer simulations.
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Eye Glass Display (EGD) with microdisplay to realize the virtual display can make the large screen, so virtual image has been developed by using microdisplay panel. This paper shows study of low cost lens design and simulation for microdisplay system with 0.6" Liquid Crystal on Silicon (LCoS) panel. Lens design optimized consider to spherical aberration, astigmatism, distortion, and chromatic aberration. Code V is used and it designed an aspheric lens about exit pupil 6mm, eye relief 20mm and 35 degree of field of view (FOV). With the application this aspheric lens to LCOS type's microdisplay, virtual image showed 50 inch at 2m. One side of the aspheric lens was constituted from diffractive optical element (DOE) for the improvement in a performance. It had less than
${\pm}2%$ of distortion value and modulation transfer function in axial had 20% of resolution with 30 lp/mm spatial frequency. The optical system is suitable for display of 0.6"-diagonal with SVGA. -
A new configuration of LCD projectors for polarized stereoscopic projection having no light loss in the polarization process is suggested. In the proposed system, two polarizing filters that are employed in the conventional LCD polarized stereoscopic projection system causing additional light loss and image distortion are excluded by taking into account of polarization property of the LCD projector and image processing techniques. From some experimental results by using the Type-1 LCD projectors, light loss of the proposed system occurring in the polarization process is found to be zero.
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In this paper, a new multi-view 3D video communication system for real-time Reality teleconferencing application is proposed by usin gthe IEEE 1394 digital cameras, Intel Xeon server computer system and Microsoft's DirectShow programming library and its performance is analyzed in terms of image-grabbing frame rate and number of views. The captured two-view image data is compressed by extraction of disparity data between them and transmitted to another client system through the communication network, in which multi-view could be synthesized with this received 2-view data using the intermediate view reconstruction technique and displayed on the multi-view 3D display system. From some experimental results, it is found that the proposed system can display 16-view 3D images with a gray of 8bits and a frame rate of 15fps.
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In this paper, implementation of object-based multiview 3D display using object segmentation and adaptive disparity estimation is proposed and its performance is analyzed by comparison to that of the conventional disparity estimation algorithms. In the proposed algorithm, firstly we can get segmented objects by region growing from input stereoscopic image pair and then, in order to effectively synthesize the intermediate view the matching window size is selected according to the extracted feature value of the input stereo image pair. Also, the matching window size for the intermediate view reconstruction (IVR) is adaptively selected in accordance with the magnitude of the extracted feature value from the input stereo image pair. In addition, some experimental results on the IVR using the proposed algorithm is also discussed and compared with that of the conventional algorithms.
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The ultra thin hole injection layer (HIL) was deposited on an indium-tin-oxide (ITO) anode by using an ion beam assisted d eposition (IBAD) for the fabrication of an polymeric electroluminescence device for the first time. The device with the HIL deposited by IBAD has higher external quantum efficiency than the device with the HIL by conventional thermal evaporation. It is found that the deposited HIL by IBAD has high surface coverage on ITO anode in a few nm regions because the HIL prepared has high adatom mobility by ion beam energy.
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The thiogallate phosphors which are well known for a long time as phosphor materials for CRT or EL device were reported. Those have high luminescent properties at long-wavelength region. Among those phosphors, the samples with divalent europium doped CaGa2S4 were prepared by a simple process under the reduction atmosphere
$(5%\;H_2/\;95%\;N_2)$ without toxic gas such as H2S or CS2. The prepared phosphor shows a higher luminescent efficiency (about 120%) than that of$YAG:Ce^{3+}$ phosphor. Consequently, this phosphor is possible to be applicable to white LED lamp because of the high luminescent efficiency.