한국정보디스플레이학회 2005년도 International Meeting on Information Displayvol.I
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The major display contenders: LCDs, CRTs, PDPs, projection displays, FEDs, SEDs and OLEDs are each examined in terms of the most critical display characteristic, the luminous efficiency. Each technology has great opportunity for improvement, but which one will win the race?
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We have achieved 180-degree angle of view performance using Super-PVA (S-PVA) technology first time in TFT-LCD industry. 82" full high definition (
$1920{\times}1080$ ) TFT- LCD panel, the world's largest TFT-LCD, have been developed. In addition to the size breakthrough, this product achieves 600nits brightness, over 1200:1 contrast ratio, viewing angle free, 92% color gamut, and 8ms response time. Several key enabling technologies were developed to achieve these specifications, including two transistor direct driven independently controlled S-PVA subpixels, non even area ratio sub-pixels for optimal offaxis gamma, gate overlap driving for larger driving margin, new CCFL technology for higher color gamut, and advanced fabrication techniques including the use of Samsung's new$7^{th}$ generation line. -
In order to implement high pixel density in AMLCDs, high aperture ratio is a very important design factor. We have implemented VGA panels with IPS and TN modes. IPS mode is a very attractive solution to meet the requirement for mobile phone displays. It provides much higher aperture ratio as well as wider viewing angle at extremely high pixel density over 400 ppi.
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We developed Super IPS mode TFT-LCD TV which have contrast ratio over 800:1. To increase contrast ratio, polarizer film, TFT design and color filter photoresist are investigated. In this report, we describe the basic concept and effectiveness of each item. The application of a newly developed color filter photoresist was the most effective for achieving this high contrast ratio.
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A prerequisite for a wide market acceptance of 3D displays is the ability to switch between 3D and full resolution 2D. In this paper we present a robust and cost effective concept for an auto-stereoscopic switchable 2D/3D display. The display is based on an LCD panel, equipped with switchable LC-filled lenticular lenses. A demonstrator of this concept is made. We will discuss measurements and numerical simulations of the key optical characteristics of this display. The switching characteristics of LC-filled lenticular lenses are discussed and the overlap of the view distributions is introduced as a figure of merit for crosstalk. The 0.62 overlap in our present demonstrator design, gives an excellent 3D image quality, combined with a good depth impression.
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Integral imaging is an attractive three-dimensional display technique providing full-parallax full-color three-dimensional images in real-time without any viewing aids. In this paper, we present the recent progress on the three-dimensional display based on integral imaging focusing on its depth and viewing angle enhancement and the three-dimension/twodimension convertibility.
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A new algorithm of the image mapping which is a technique of the elemental image generation is proposed. The proposed method is based on the characteristics of the lens array such as the number, the size and the focal length of the elemental lens. The 3D image generated by 3D graphic API such as OpenGL can be directly adopted without the complex adaptation. Since the image mapping using the proposed method can enhance the speed of the elemental image generation, the computer- generated integral imaging system can be applied to virtual reality system.
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In this paper, a novel 2D/3D convertible display system based on integral imaging is proposed. Combining two liquid crystal display panels with integral imaging, it is possible to convert the display between two-dimensional mode and three-dimensional mode without mechanical movement. The proposed method is proven by preliminary experiments.
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An analysis on the viewing parameters of floating display system based on integral imaging is introduced. A floating display system based on integral imaging is a three-dimensional display system which can display three-dimensional moving pictures with impressive feeling of depth. The analysis given in this paper will optimize the design of the floating display system for the specific application.
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We have recently developed new organic TFT technologies such as self-aligned self-assembly (SALSA) process and a high-resolution color active-matrix LCD panel. A new method to realize high-resolution printable organic TFT array to drive active-matrix flat-panel display will be discussed.
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Suh, Kyung-Soo;Kang, Seung-Youl;Ahn, Seong-Deok;Oh, Ji-Young;You, In-Kyu;Kim, Gi-Hyun;Baek, Kyu-Ha;Kim, Chul-Am;Hwang, Chi-Sun;KoPark, Sang-Hee;Yang, Yong-Suk;Chung, Sung-Mook;Lee, Jeong-Ik;Do, Lee-Mi;Chu, Hye-Yong;Kang, Kwang-Yong 61
Pentacene based OTFT on PC and PES plastic substrates have been fabricated in a scale of 5 inches. We could get a small OTFT device enough to be applicable for AMOLED by acquiring the at least misalignment margin through a contact aligner. And also we could find out the degradation of device parameter through the integration processes and improve the properties by using a buffer layer as an etch stopper in an active patterning. Through these, the mobility of device is more than about$0.2cm^2/Vs$ and$I_{on}/I_{off}$ is higher than$10^5$ . -
We fabricated an array consisting of organic TFTs(OTFT) and organic LEDs (OLED) in order to demonstrate the possible application of OTFTs to flexible active matrix OLED (AMOLED). The panel was composed of
$64{\times}64$ pixels on 4 inch size polyethylene-terephehalate (PET) substrate in which each pixel had one OTFT integrated with one green OLED. The panel successfully displayed some letters and pictures by emitting green light with a luminance of$1.5\;cd/m^2$ at 6 V, which was controlled by the gate voltage of OTFT. -
There have been various efforts to achieve a better PDP TV, which have low power consumption, high image quality and low price. As the results, the power consumption of LG's new 42 inch HD PDP could be lower than 42 inch LCD under the general movie display load condition. And the address discharge time lag of
${\sim}1\;{\mu}s$ for 42 and 50 inch XGA single scan by which the cost can be reduced and image quality can be improved was achieved by using new MgO material and driving waveform. In addition, we have suggested TCA (Triangular Color pixel Arrangement) cell structure for realizing the full HDTV of 60inch diagonal size, which has$1920{\times}1080$ resolution. The luminous efficiency of the suggested TCA structure has been increased about 40% compared with that of the conventional cell structure. -
We have studied the needs for developing plasma displays with 1080p quality and the possibilities to construct an affordable 42-inch full HD PDP. It seems impossible to get a prototype unless we overcome technical difficulties. First, we should find a way to innovatively improve luminous-efficacy and interconnection problems. At the same time, we should find a way to overcome image quality degradation in single scan.
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A prototype of 25-inch SMPDP module had been developed by the end of 2004. Most driving technologies succeeded to those of the previous 34-inch SMPDP module .In this work, we make an optimization effort on the driving waveforms, especially for setup period. Long ramp waves show good wall voltage controllability, with which we can get a reliable addressing and better sustain stability.
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A low-cost and high-speed PDP color inspection system can be constructed by using a CCD camera against a colorimeter. Though the inspection can be done using RGB signals obtained by a camera, it has some difficulty to introduce human color sensitivity. Thus, it is quite desirable to convert the RGB values into the XYZ values that can be compared to the values of a colorimeter. Accordingly, the current study proposes a color conversion method that can analytically calculate the RGB-to-XYZ conversion matrix by utilizing the RGB primaries and the reference white. Experiments on Macbeth colorchecker colors showed that the average color difference between the converted XYZ values of the proposed method and the measured XYZ values of a colorimeter is much below the threshold of distinguishing two adjacent color patches.
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In this paper, a general performance of the PSS-LCD or Polarization Shielded Smectic Liquid Crystal Display is discussed. This smectic base LCD does not use any spontaneous polarization, but uses induced polarization just same with current nematic base LCDs. Specific initial molecular alignment as well as specific cell design realizes extremely fast optical response speed with native wide viewing angle. Moreover, this performance is provided by full compatible electronics for current conventional LCDs. A general performance of the PSS-LCD is introduced here.
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The recent Bistable Nematic (
$BiNem{(R)}$ ) LCD technology presents long term bistability, high level passive matrix multiplexing and high optical quality. The BiNem device, based on anchoring breaking, needs specific low anchoring strength materials - alignment layers and liquid crystal mixtures. We present here our approach to develop nematic mixtures with wide enough temperature range and low zenithal anchoring energy. -
Recently, competition between LC modes for LC TVs becomes high. In this paper, status of each mode is briefly reviewed with commenting on its electro-optic characteristics and possible application fields. Further, to understand effects of carbon nanotubes (CNTs) dispersed in nematic liquid crystal on electro-optic characteristic and orientation of the LC, CNT-doped NLC cells are made and evaluated. The hysterisis studies of voltage-dependent capacitance show that the amount of residual dc is greatly reduced due to ion trapping by CNTS.
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We demonstrate an electro-optical device based on the flexoelectric effect of a short-pitched cholesteric liquid crystal. By using a dual-frequency switchable nematic, a small amount of chiral dopant and a small amount of phase-separated polymer localized on the surface, we were able to create a device that operates in amplitude (flexoelectric) and phase(dielectric) modes. At high frequency the dual frequency liquid crystal suppresses the phase mode at higher voltage, which improves the switching speed, and thereby preserving the in-plane-switching mode.
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This paper describes work by the authors aimed at reducing the mismatch between accommodation and convergence when viewing stereoscopic 3D images. Two methodologies, one a simple system with a mono-focal lens and the other a dynamic system using a moving LCD, were introduced as experimental 3D displays with optical correction. The results of usage evaluations suggest improvements in health and amenity can be achieved with stereoscopic representation with accommodation.
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The proposed method is based on extracting information from 3-D Fourier spectra calculated from some projection incoherent images. Three colored computer-generated holograms (CGHs) are synthesized from 3-D Fourier spectra. Optically reconstructed full-color images are presented.
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A field-sequential color projection system can display color images using panel. However, it suffers from a characteristic trichromatic separation known as "color breakup". The viewing of images exhibiting color breakup may cause visual fatigue and mental stress. In this study, the authors examine, from the standpoint of human factors, the objective and subjective symptoms that can result from the viewing of images with color breakup.
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The visual perception tests were conducted to determine limits of luminance of a LCD TV from a viewpoint of glare. The results showed that people, who watch TV in their living room, perceive glare above
$410\;cd/m^2$ at full window and$590\;cd/m^2$ at 1/25 window. -
An integrated pattern profile distortion is newly proposed to analyze various two-dimensional test patterns. The unit is converted to a time to make parameters comparable for various types of displays. In addition, this can be compared with that of extended blur edge width in time scale, which has been reported.
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Organic light emitting transistors (OLET) which are vertically combined with the organic static induction transistor (OSIT) and organic light emitting diode (OLED) are fabricated and the device characteristics are investigated. High luminance modulations by relatively low gate voltages are obtained. In order to realize the flexible electronic circuits and displays, we have fabricated OSIT on plastic substrates. The OSIT fabricated on plastic substrate show almost same characteristics comparing with those of nonflexible OSIT on glass substrate. The OLET described here is a suitable element for flexible sheet displays.
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Cho, Kil-Won;Kim, Do-Hwan;Park, Yeong-Don;Jang, Yun-Seok;Hwang, Min-Kyu;Lee, Hwa-Sung;Lim, Jung-Ah 147
We report on high-performance organic field-effect transistors by promoting surface-mediated two-dimensional molecular ordering in organic semiconductor. To achieve this goal, we have controlled the intermolecular interaction at the interface between organic semiconductor and the insulator substrate. -
Kwon, Jang-Yeon;Kim, Do-Young;Jung, Ji-Sim;Kim, Jong-Man;Lim, Hyuck;Park, Kyung-Bae;Cho, Hans-S;Zhang, Xiaoxin;Yin, Huaxiang;Xianyu, Wenxu;Noguchi, Takashi 149
We present the characterization of poly-Si TFT fabricated below on Plastic Substrate below$170^{\circ}C$ on plastic substrate using excimer laser crystallization of Xe sputtered Si films. Gate insulator with a breakdown field exceeding 8 MV/cm was deposited by using inductively coupled plasma CVD. Finally, we successfully fabricate TFT with a electron field-effect mobility value greater than$290\;cm^2/Vsec$ . -
Computer simulations of a pdp discharges provide unique information necessary for their analysis, unavailable otherwise. Statistical instability of the ramp discharge and the role of exoemission, nature of striations during sustain discharge, physical mechanism responsible for the propagation of the cathode ionization wave, and line loading effects are just a few examples when simulations can be successfully used.
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The plasma ion density in AC-PDP has shown to be increased from
$5.6{\times}10^{11}cm^{-3}$ to$9.0{\times}10^{11)cm^{-3}$ as the Xe mixture ratio to neon increase from 1 % to 10 %, respectively, at fixed pressure of 400 Torr, by using the micro-Langmuir probe. It is noted that the plasma ion density is density increases as the gas pressure increases in this experiment. The electron temperature decreases from 2.3 to 1.2 eV as the Xe mole fraction increases from 1 % to 10 % at fixed pressure of 400 Torr, which is measured by the micro Langmuir probe and high-speed ICCD camera in this experiment. It is noted that the electron temperature decreases as the gas pressure increases from 150 to 400 Torr in this experiment. It is also observed that the exited Xe atom density and the plasma ion density are in strong correlation sharp between each other in this experiment. It is noted that$5.2{\times}10^{12}cm^{-3}$ in the$1s_5$ metastable state and$1.2{\times}10^{12}cm^{-3}$ in the$1s_4$ resonance state for the PDP cell with gap of 50 um distances under the fixed gas pressure of 400 Torr and Xe content ratio of 10 %. -
The mechanism of striation in the coplanar- and matrix-type plasma display panel (PDP) cells has been studied using the particle-in-cell Monte-Carlo Collision (PIC-MCC) model. The striation formation is related to the ionization energy of neutral atoms and the well-like deformation of space potential by space charge distribution. Negative wall charge accumulation by electrons on the MgO surface of the anode region is also one of the key factors for the formation of striation. The clearness of the striation phenomenon in PIC-MCC code in comparison with fluid code can be explained by using nonlocal electron kinetic effect.
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Experimental measurements are reported and compared with the results of a two-dimensional fluid simulation for the investigation of the discharge characteristics regarding the change of the mixture ratio of Ne-Xe-He noble gases. The increase of Xe contents results in the increases of luminance and luminous efficiency while it also results in the increase of the breakdown voltage and the discharge time lag. The addition of He gas increases the brightness and the luminance efficiency. When Xe partial pressure is low, the luminance efficiency increases with the amount of He at the same total pressure. When Xe partial pressure is high, however, the luminance efficiency has a maximum value when the partial pressure of He is about 10% of the total pressure for a standard AC PDP cell with Xe fraction of
$10{\sim}30%$ . -
Lee, Kyo-Sung;Shin, Nam-Hoon;Shin, Bhum-Jae;Choi, Kyung-Cheol;Jang, Sang-Hun;Park, Hyoung-Bin;Lee, Seong-Eui 175
The spatio-temporal behaviors of Infra Red(IR) emission images of the sustain discharges were observed in AC PDP with various coplanar-gaps and auxiliary electrode. When the height of barrier rib was fixed, IR intensity of the sustain discharges in AC PDP did not increase with increase of coplanar-gap. The IR efficiency of sustain discharges showed the similar behavior with the IR intensity. The IR intensity had its maixmum value when the coplanar-gap was$200\;{\mu}m$ and the height of barrier rib was$150\;{\mu}m$ . It was also found that the auxiliary electrode in the front plate enhanced IR emission during sustain discharge when the pulse was applied to the auxiliary electrode. -
We demonstrate that the finite rate of dielectric relaxation in liquid crystals which has been ignored previously causes profound effects in the fast dielectric reorientation of the director. The phenomenon is relevant for submillisecond switching of the director when the switching rate approaches the rate of dielectric relaxation through the reorientation of the molecular dipoles. A submillisecond switching (
$15-400\;{\mu}s$ for an optical retardation shift$0.3-2.2\;{\mu}m$ in$10-15\;{\mu}m$ thick cells) is demonstrated for dual frequency nematic cells with high pretilt that maximizes the dielectric torque acting on the director. We propose the theory of dielectric response in which the electric displacement depends not only on the present (as in the standard theory) but also on the past values of electric field and director. We design an experiment in which the standard "instantaneous" model and our model predict effects of opposite signs; the experimental data support the latter model. -
Alignment pattern of checkerboard was constructed by the stylus of atomic force microscope. Orientational bistability of the nematic liquid crystal was realized on that frustrated surface alignment. Macroscopic orientational switching between two perpendicular directions took place by an appropriate in-plane electric field. The threshold electric fields decreased in both switching directions as temperature increased. The focused laser heated up only the limited domains in the cell including a light-absorbing medium. Irradiating the laser concurrently with an appropriate electric field, we switched the selected unit domains in the alignment pattern. The switched domains maintained stably the switched direction without the disturbance from the exterior. Extending and repeating this process, we realized extremely fine devices of bistable switching.
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Evaluating methods of the polar and/or azimuthal anchoring strength coefficients by means of the renormalized transmission spectroscopic ellipsometry are demonstrated. The Anchoring strength coefficients can be evaluated from the measurement of ellipsometric parameters measured by the oblique incident transmission ellipsometry, where the effect of multiplebeam interference is eliminated. The device parameters such as the pretilt angle and cell gap can be determined simultaneously even in the case of the twisted nematic liquid crystal sample cells.
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Using theoretical analysis based on Landau theory, it is shown that only five phenomenological parameters are necessary to describe the twelve bulk elastic constants of a biaxial nematic phase. Further, a simple method for determining the values of these five parameters experimentally is given. Comparison with the values of the well-known splay, twist, and bend elastic constants of the uniaial nematic is made.
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We have studied the origin of coherent director rotation [CDR] as well as memory behavior in thiol-ene polymer stabilized ferroelectric liquid crystal [FLC]. The ene constituents are found to be always located at the inter-layer space and induce the coherent director rotation motion of liquid crystal molecule. On the other hand, the thiols are more intersticed between ferroelectric liquid crystal molecules at intra-layer as the thiol gets longer, and these intersticed thiols enhance the multistability and the resolution of memory state of FLCs.
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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 of NEC MT 1060R, light loss of the proposed system occurring in the polarization process is found to be zero and the resultant stereoscopic video image projected from this system is also found to be 213%, 75% and 300% brighter than those projected from the conventional Type-1 LCD projector-based, Type-2 LCD projector-based and Type-3 projector-based systems, respectively.
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High-density directional display provides natural three-dimensional images. A large number of directional images are displayed in different horizontal directions with directional rays. There are two different types of display configurations. One is the projection-type and the other is the thin-type. The 64-directional and 128-directional displays using the projection-type configuration and the 72-directional display using the thin-type configuration are presented. The human responses are also shown.
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To find the optimal expansion of the color gamut of a display, we investigated various 4-primary display systems based on DLP. Via comparing the volume of the color gamut in a 3-D uniform color space CIELUV, the best 4-primary system on the premise of keeping the existing three primaries is brought forward.
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To make real 3D vision available, we have established a volumetric 3D display system that based on rotating LED matrix. The paper introduced a method to correct the problem that pixels are not symmetrical but circumferential in space, which causes the resolution of the edge area much lower than that of the central area.
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The concepts of flexible displays and plastic electronics have become some of the most talked about new product opportunities for direct view flat panel displays in recent years. The potential advantages are frequently cited, but the achievement of commercially viable products will require many significant technological innovations in new materials and manufacturing technology. This paper will provide a very broad overview of the rationale for developing flexible displays, the market drivers, the applicable display technologies, the major hurdles that must be overcome and the required evolution of new manufacturing technologies that are essential for successful commercialization. This is intended to provide the outline and context for the series of presentations on specific aspects in each of these topics that will be delivered and discussed at the Plastic Electronics Special Session of the 2005 IMID conference.
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In this paper, we discuss the potential applications for electronic systems on flexible substrates. The barriers to the successful development of commercial markets are analyzed. For each promising application, the critical technical features are identified. Ways to bridge the gap between research and commercialization are suggested.
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True electronic paper displays are being enabled by the development of two core technologies - plastic electronics for display backplanes and electrophoretic ink for use as the imaging layer. Electrophoretic ink developed by E Ink Corporation continues to advance performance along with parallel technology breakthroughs in flexible TFT backplanes. An overview of these advances in the ink imaging material will be discussed with special emphasis of the expected impact on the emerging flexible display applications.
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The commercialization of an active matrix e-reader display using E Ink microencapsulated electrophoretic (MEP) ink marked a big step towards comfortable reading over an extended period of time in an electronic book, as the high resolution display, jointly realized by Philips, E Ink and Toppan, has a true paper-like look and feel. Alternative electrophoretic material systems are being developed by SiPix and Bridgestone and progress has been made in the past two years. In this paper, electrophoretic material systems are briefly reviewed, after which the perspectives and challenges of electrophoretic displays are addressed and methods for generating gray tones are presented and discussed.
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The discharge characteristic of a novel AC PDP with Shadow mask (SM-PDP) has been studied with 2-D and 3-D simulations. Compared with the conventional coplanar PDP, the SM-PDP has lower ignition voltage, higher response frequency and higher brightness. It's easy to realize a high definition display while keeping a good performance with the SM-PDP. The discharge process as measured with a fast Intensified CCD (ICCD) compares favorably with the simulation results.
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Lee, D.K.;Choi, J.H.;Choi, W.S.;Ok, J.W.;Kwon, B.S.;Lee, H.J.;Lee, H.J.;Kim, D.H.;Park, C.H. 247
In this paper, new address electrode having separated dual electrodes is suggested to reduce addressing time in ac PDP. It had been found that both the formative and jitter width of the suggested electrode are improved by$10{\sim}20$ % compared with the conventional one on IMID 04'. So we experiment other several kinds of the separated electrodes, and the change in discharge characteristics is analyzed by using a two-dimensional fluid simulation. The key feature of the suggested structure is that the distribution of Xe and Ne ion is controllable during the address periods without significant increases in the capacitive load of the address electrodes. -
Cho, Byung-Gwon;Tae, Heung-Sik;Ito, Kazuhiro;Song, Jun-Weon;Lee, Myoung-Kyu;Kim, Sang-Chul;Jung, Nam-Sung;Lee, Kwang-Sik 251
A new driving waveform was proposed to reduce the cost in PDP-TV based on Vt close curve by eliminating the common (X) board under the conventional 42-inch panel structure. Due to the serious misfiring problem during a sustain-period when applying the new driving waveform, the wall voltage was measured and analyzed after the reset-period using Vt close curve. As a result of adopting the proposed driving waveform designed using Vt close curve analysis, the cost of PDP module could reduce compared with the conventional PDP module without any misfiring discharge. -
In this study, new types of counter electrode discharge cells for PDP were designed. The counter electrode discharge cells were designed to realize long-gap discharge mode, low firing voltage and moderate conductance for evacuation and sealing process of the panel. In order to test the concept of the design, macro discharge cells were prepared and the discharge characteristics were evaluated. The results indicate that discharge behavior may be modified significantly by changing the morphology of discharge cells.
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Image retention is a kind of fatal shortcoming of the AC PDPs for realizing high-quality picture. In this work, the measurement method of image retention was proposed using temporal measurement of luminance, CIEXYZ tristimulus values, IR emission of reset pulse, and temperaturel. On the base of temporal measurement of luminance, CIEXYZ tristimulus value, and IR emission of reset pulse, the retention time of Ne+5%Xe gas-mixture discharge was about 2 hours after white window image. However, it was about 20 minute on the base of temporal measurement of temperature.
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Han, Yong-gyu;Lee, S.B.;Jeong, S.H.;Son, C.G.;Yoo, N.L.;Lee, H.J.;Lim, J.E.;Lee, J.H.;Jeoung, J.M.;Ko, B.D.;Oh, P.Y.;Moon, M.W.;Choi, Eun-Ha 263
In the alternative current plasma display panel(AC-PDP) technology, it is very important to remove the image sticking for improving an image quality. In this paper, we have investigated the driving method of alternative current plasma display panel(AC-PDP) for preventing image sticking. We have investigated the driving method of alternative current plasma display panel(AC-PDP) for preventing image sticking. The preventing method of image sticking was proposed by adopting the Sticking Remove Pulse(SRP). The variation of brightness is most affected by the MgO to be formed at the surface of the phosphor layer. As a result, the image sticking is reduced when the driving method adopted an SRP. -
Kim, Yong-Hae;Chung, Choong-Heui;Yun, Sun-Jin;Park, Dong-Jin;Kim, Dae-Won;Lim, Jung-Wook;Song, Yoon-Ho;Moon, Jae-Hyun;Lee, Jin-Ho 269
Using optimized sputtering condition of a-Si and$SiO_2$ thin film, we can obtained the large grained poly-Si film on PES substrate. The gate dielectric grown by plasma enhanced atomic layer deposition, laser activation and organic interlayer dielectric material make TFTs on PES possible with mobility of$11cm^2/Vs$ (nMOS) and$7cm_2/Vs$ (pMOS). -
The high stability of a-Si:H TFTs device is studied with different deposited conditions of
$SiN_x$ films by PECVD. The process parameters of$N_2$ ,$NH_3$ gas flow rate, RF power, and pressure s of hydrogenated amorphous silicon nitride are taken into account and analyzed by Taguchi experimental design method. The$NH_3$ gas flow rate and RF power are two major factors on the average threshold voltage and the a-SiNx:H film's structure. The hydrogen contents in$SiN_x$ films were measured by FTIR using the related Si-H/N-H bonds ratio in$a-SiN_x:H$ films. After the 330,000 sec gate bias stress is applied, the threshold voltages ($V_th$ ) shift less than 10%. This result indicates that the highly stable a-Si:H TFTs device can be fabricated with optimum gate$SiN_x$ insulator. -
The proposed Novel OverDriving Technology with Optimum Look-up-Table(LUT)is suggested to be a better solution to reducing the occurrence of overshooting caused by the traditional overdriving method implemented to normally liquid crystal (VA mode). Chunghwa Picture Tubes, LTD. (CPT) has successfully implement this tech into 20 inch TFTLCD TV module at the present day. The proposed technology can speed up gray-to-gray response time of LCD less than one half of frame time. On the side, Optimum LUT construction apply the compression scheme to record total actual grayscale transfer characteristics instead of applying the normal spread method such as linear / non-linear interpolation. The memory space is been reduced and the distortion of the image quality is lesser.
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Hong, Sung-Jin;Kim, Jin-Hong;Shin, Kyung-Ju;Chai, Chong-Chul;Choi, Jung-Ye;Park, Cheol-Woo;Suk, Jun-Hyung 280
Recently, the demands of the high quality LCD display device have increased. We have developed the smart LCD that photo sensor is integrated in. Amorphous silicon TFTs have photo leakage current characteristics when the channel of TFTs are lighted on. This characteristic has applied in our device. We expect that photo sensor integrated LCDs have lots of merits in mobile display device, note PC panel and LCD TV. -
Yoon, Ji-Mo;Yoo, Juhn-S.;Yu, J.S.;Kim, E.;Son, C.Y.;Park, J.K.;Yoo, Y.S.;Lim, K.M.;Kim, C.D.;Chung, I.J. 285
A 2.8 inch fully integrated SOP employing a high performance LTPS CMOS TFT technology has been developed for mobile display applications. The LCD module is directly interfaced with 3V 6-bit RGB source via timing control circuitry. The integrated data driver comprises a 6-bit hybrid type DAC with low power analog buffer. -
New poly-Si TFTs have been proposed and fabricated in order to increases the output channel resistance (
$r_o$ ). The counter-doped($p^+$ ) source is tied to the$n^+$ source and is extended into the channel region so that it employs the reverse bias depletion in the channel. As$V_{DS}$ is increased, the depletion width is increased and the effective channel width is reduced. Therefore, the output current saturates well and the$r_o$ is increased successfully. The proposed CMOS devices may improve the amplifier gain of data driver in active-matrix displays -
The differences between floating and grounded body effects in polycrystalline silicon thin-film transistors (polysilicon TFTs) are investigated by making a body contact. The floating body effects such as kink effect, subthreshold slope change, and body current characteristics are explained and modeled by impact ionization, which causes source body turn on, and activates the parasitic bipolar junction transistors (BJTs). These effects become crucial for channel lengths of 4㎛ or shorter. Our data show that making a body contact reduces kink effects significantly and identifies impact ionization mechanism in polysilicon TFTs.
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We developed new WV-TN panel which has 170/170 viewing angle and 8ms response time. This viewing characteristics almost catch up with those of VA. To extend the viewing angle we optimized the cell design and LC parameters. This new technology strongly increase the demand of TN monitors especially for the monitor market larger than 19"
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Characteristics of Poly-Si TFTs Fabricated on Flexible Substrates using Sputter Deposited a-Si FilmsThe characteristics of polycrystalline silicon thin-film transistors (poly-Si TFTs) fabricated using sputter deposited amorphous silicon (a-Si) precursor films are investigated. The a-Si films were deposited on flexible polymer substrates using argon-helium mixture gases to minimize the argon incorporation into the film. The precursor films were then laser annealed by using a XeCl excimer laser and a four-mask-processed poly-Si TFT was fabricated with fully self-aligned top gate structure. The fabricated pMOS TFT showed field-effect mobility of
$32.4cm^2/V{\cdot}s$ and on/off ratio of$10^6$ . -
A low-power gate driver IC, which can be used for TFT-LCD application, is proposed. The short-circuit current of the output buffer is greatly reduced. An experimental prototype gate driver implemented in a
$0.35-{\mu}m$ CMOS technology demonstrates that the power reduction of 16 % is obtained. -
We report the self-aligned low temperature poly silicon (LTPS) TFT process using simple doping process. In conventional LTPS-TFT, the Lightly Doped Drain (LDD) doping and source/drain doping are processed separately by aligning the gate with the source and drain during the gate lithography step. This ne w process not only fabricates fully self-aligned low temperature poly silicon TFTs with symmetric LDD structure but also simplifies the process flow with combined source/drain doping and LDD doping in one step. LDD doping process can be achieved using only source/drain doping process according to the new structure. In this paper, the TFT characteristics of NMOS and PMOS using the new doping process will be discussed.
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We investigated light absorption layer effect on metal-induced lateral crystallization (MILC) growth rate and MILC thin films transistors (TFTs). As annealing method, we used scanning-rapid thermal annealing (RTA). MILC growth rate which was crystallized by light absorption layer and using scanning-RTA was 3 times than normal MILC which was without light absorption layer growth rate. Also we compared MILC TFTs characteristics which were combined to light absorption layer with conventional MILC TFTs. After scanning-RTA process, MILC-TFTs which were with light absorption layer were superior to conventional MILC-TFTs. With this new MILC-TFTs structure, we could reduced crystallization time and obtain good electrical properties.
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CW laser dopant activation (CLDA) is suggested as an alternative to conventional thermal annealing. The sheet resistance of the ion doped poly-Si after CLDA is sufficiently low compared to the value measured after thermal annealing. The surface damage due to ion doping on the poly-Si can be recovered while CW laser scan for dopant activation. Therefore, the CLDA can be applied to LTPS processing.
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Light flicker is a notorious phenomenon influencing light quality. The flicker of the light flux outputs from the light sources perceived by human eyes depends upon the lamp brightness fluctuations for projector display. This paper describes a ballast ignition control system, which makes the lamp strike frequency phase lock the blanking time period to minimize the flicker effect
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We report experimental and simulation results of L0 state using inner retarder film compared with normal retardation film. In short wavelength range, the reflectance of inner retardation film is three times compared with that of normal retardation film. This results in blue color of L0 state, as retardation decreases or polar angle increases, the color shifts toward purple, finally yellow color, as expected in the simulation results.
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We report a microcapsule-based electronic ink display technique, containing hollow titania particles which were prepared via a complex coacervation method using gelatin and gum arabic. In order to reduce density mismatch between nanoparticels and dielectric medium, hollow titania particles were introduced. Microcapsules were then prepared using gelatin to improve the elasticity of the microcapsule wall and their electrophoretic characteristics were
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We propose a novel technique for evaluating the azimuthal anchoring strength of the alignment film on the nematic liquid crystal (LC). In our evaluation, a unique cell, which has two domain in one cell, was used; one is hybrid aligned nematic (HAN) region, the other is twsited nematic (TN) region (viz. HAN/TN two domain cell). From the comparison of director angles on the front substrate with each region, we are able to determine the angle between easy axis and real director axis on the front substrate. From this evaluation, the azimuthal anchoring strength was obtained accurately.
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Inorganic alignment layer (IAL) was deposited on an indium-tin-oxide (ITO) by using reactive sputtering deposition method. After deposited, IAL was irradiated by
$Ar^+$ ion beam (IB) for liquid crystal (LC) alignment. IAL treated by various conditions such as IB energy, IB incident angle, and IB irradiation time had excellent alignment property and electro-optical property the same as that of PI. We investigated into the stability of ion beam treated IAL after a lapse of long time. However IAL irradiated IB did not occur degradation of electro-optical property. The results implied that IAL irradiated IB was adopted as LC alignment layer instead of rubbed polyimide. -
We investigated the liquid crystal (LC) alignment phenomena using a-C:H and a-C:F:H thin films. Homogeneous alignment is obtained using ion beam treated hydrogenated amorphous carbon (a-C:H) thin films. Homeotropic alignment is obtained using F treated a-C:H thin films, namely, fluorinated amorphous carbon (a-C:F:H) thin films. We investigated the relationship between the surface properties of amorphous carbon based alignment layer and LC alignment phenomena.
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We have found that the hysteretic behavior of a polymer stabilized ferroelectric liquid crystal system coincides with Blinov et. al's model qualitatively. The hysteresis inversion frequency could be promoted up to 7000 Hz by connecting external capacitor and resistor in serial. In addition, the influence of temperature and the amplitude of the applied field on hysteresis-free switching of the cell could be minimized.
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We have examined the aspects of the orientational ordering deformation of ferroelectric liquid crystal during bending performance of plastic substrate by analyzing the polarizing optical microscope texture and the birefringence of the cell. Striped texture becomes more prominent as the radius of curvature of substrate gets smaller. The optic axis of the adjacent stripes domain was not same and the relative angle between them becomes larger as the radius of curvature gets smaller. Especially, the optic axis rotation angle of one domain was lager than the other and the liquid crystal molecules in each domain became more coherent. In addition, the birefringence data with obliquely incident light shows the polar direction shift of liquid crystal molecule by bending performance.
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We have simulated a symmetric dual-gate TFT which has triple floating n+ channel to improve the on-current of the dual-gate TFT. We achieved a low hole concentration at the source and channel junction causes the improvement the potential barrier so that we observed the reduction of the kink-effect. In this paper, we observed the reduction of the kink-effect compared with the conventional single-gate TFT and the improvement of the on-current compared with the conventional dual-gate TFT.
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Lee, Seong-Ryong;Jhun, Chul-Gyu;Yoon, Tae-Hoon;Kim, Jae-Chang;Noh, Jeong-Dong;Suh, Dong-Hae;Lee, Jung-Yeal 345
In this paper we propose a configuration for an optically compensated bend (OCB) mode using circular polarizers with wide-band wide-viewing-angle (WBWA) quarter-wave plates (QWPs). Parameters of LC material and compensation films are optimized for wide viewing angle characteristics and excellent spectral properties of the OCB mode. -
You, Jae-Geon;Kim, Sung-Ju;Gwag, Jin-Seog;Lee, Hyun-Kyung;Lee, Dae-Kyu;Ahn, Jun-Yong;Jun, Jung-Mok;Lee, Jung-Yeal 349
In this paper, we have investigated the hydrogen effects on Diamond-like Carbon (DLC) as an LC alignment layer of the FFS mode. By change of a Hydrogen content in the DLC sputtering process, the image sticking and electro-optic characteristics of Black-White panel with DLC / IB technology were examined. -
We have characterized the mechanical stability of the Pixel-Isolated Liquid Crystal (PILC) mode for plastic LC display applications. In our device, the LC molecules are fully isolated in the pixels by the phase-separated polymer walls. The experimental results of microscopic observation and electro-optic characterization show that our flexible PILC device has good mechanical stability against external point pressure or bending distortion due to the polymer walls in our structure.
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A novel wide viewing angle flexible liquid crystal display will be demonstrated. The crossed matrix-type micro-cell structure was adopted in this design. The LC domains were divided into four different tilted directions by the combination effect of pixel fringe field and crossed matrix type micro-cell. It can create four domains without rubbing process and form the cell gap without spacer. For flexible color fabrication, a novel inkjet printing technology is adopted. This cost effective wide viewing angle color flexible LCD technology can be a good solution for high performance flexible LCD.
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The transient current of STN-LCD cells was measured and simulated to characterize ionic behavior in LCD cells. An experiment was performed to investigate the contribution of LC material and PI trapping effect to mobile ions in the LC layer. We observed that most of ions are trapped on the PI surface rather than stay in the LC layer in case of normal STN-LCD, and PI surface favors larger ions in general. A linear correlation of ion density and
$V_50$ shift of the Transmission-Voltage (TV) curve between 30Hz and 1kHz at typical ion mobility was found. -
We developed a method for adhesion of two substrates with stable liquid crystal (LC) structures using patterned microstructure and LC/polymer composite materials. In the device, the LC molecules are isolated in pixels where LCs are surrounded by patterned microstructures, and two substrates are tightly attached each other by the solidified polymer produced by anisotropic phase separation by UV exposure. These devices show very good mechanical stability against external pressure.
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Hong, Kwang-Pyo;Lee, Jun-Ho;Yoon, Hyeun-Joong;Chun, Jin-Young;Ryu, Bong-Yeol;Jun, Jung-Mok;Lee, Jung-Yeal 368
High energy-efficiency TFT-LCD supporting a good image quality is developed with Data Rendering Innovation Matrix Technology. The innovative matrix consists of octal sub-pixels and sub-pixel rendering technology enhanced the light efficiency; up to 30%, and reduces the number of column drivers for the same resolution by a third. -
We demonstrated a replica molding technique for producing a self-formed multidomain structure displays (LCDs). The multidomain structure was naturally obtained on a replica mold film having periodic patterns which have two dimensional microgrooves. It was found that with the axially symmetric multidomain structure along the microgrooves exhibits excellent viewing characteristics.
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We proposed a new fabrication method for stable flexible LCDs using stamping method with durable elastomer such as poly(dimethylsiloxane) (PDMS). In the device, the LC molecules are isolated in pixels where LCs are surrounded by PDMS microstructure, and two substrates are tightly attached by phase separated polymer layer. The electro-optic characteristics of our cell are comparable to those of normal sample without PDMS microstructure. We propose cost-effective roll-to-roll process for large size of plastic LCDs with our method.
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Diamond like carbon (DLC) films are known that they show homogeneous alignment property when they are irradiated by Ar ion beam. The DLC films in most of studies were deposited by CVD and contain large mount of hydrogen. In order to identity the hydrogen effect on alignment property, DLC films is deposited by RF magnetron sputter using various ratio of Ar and H2 as reactive gas. DLC films are characterized by FT-IR, Raman and contact angle. Alignment property is estimated by measuring pretilt angle.
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Driver IC is one of the key components on the LCD monitor and LCD/TV. The function of the driver IC is to transfer and forward the input signals to LCD panel module. Inside driver IC, there are several operating units which process the input signals and generate the appropriate size and resolution to the LCD panel module. LCD panel module will display these input signals. However, there are some difficulties which driver IC designer, LCD monitor and LCD/TV maker will face. Thus, this article addresses the function and difficulties on driver IC.
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2-[4-(4-alkylcyclohexyl)-phenyl]-5-alkyl-(1,3,2)-dioxaborinane and Fluoro-substituted 1,3,2-dioxaborinane vatives were synthesized and their physical properties were measured. synthesized compound were showed nematic isotropic transition.
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Poly(amic acid) precursors were prepared by mixing various main chain dianhydrides, main chain diamines and side chain diamines. The side chain diamine has an alkylbicyclohexyl group as a side chain. The copolyimide films, produced by casting the poly (amic acids) solution, exhibited the vertical alignment property without the rubbing process in the range of the curing themperature from
$90^{\circ}C$ to$240^{\circ}C$ for 1h. The thermal and surface properties of the poly(amic acids) depending on the curing temperature was examined. -
Super In Plane Switching (S-IPS) technology is applied for large TFT-LCD panels used in TV applications. It has a lot of advantages in comparison to the alternative, VA technology. S-IPS shows excellent viewing angle properties and fast response time between intermediate gray levels. If the performance parameters which describe the actual visual performance are considered, S-IPS is much more
$advantageous.^{1)}$ However, it shows relatively low contrast ratio in diagonal direction compared to viewing angle characteristic in upper/down direction in S-IPS. In order to compensate the relatively low diagonal contrast ratio, Super-IPS applying for optical film developed, but Super-IPS still has the problem of color shift in black$pattern.^{2)}$ So we improved this problem by developing Enhanced Super-IPS. -
Park, Lee-Soon;Yoon, Hae-Sang;Hur, Young-June;Kim, Sang-Woo;Lee, Sung-Ho;Seok, Jae-Wook;Kwon, Young-Hwan 396
Effects of such factors as polymerization temperature and a newly synthesized oligomeric photoinitiator(PEDI380) on the electro-optic characteristics of polymer/LC composite films prepared by the UV-curing method were investigated. The polymer-dispersed liquid crystal cells were made with oligomeric photoinitiator PEDI380 by UV-curing method exhibited both low driving volta ge($V_90$ ) and high contrast ratio under optimum formulation condition. -
We have studied the Pixel Isolated Phase Separated Composite Organic Film (PI-PSCOF). The PI-PSCOF can be made by the anisotropic phase separation between Ferroelectric Liquid Crystals and Pre-polymer materials by irradiating the UV with optimizing its intensity and time. In the technology, the FLC molecules are isolated in pixels where FLCs are surrounded by the inter-pixel vertical polymer walls and the horizontal polymer films on the upper substrate. The good merits of this technology are fast response time, and good mechanical and thermal stability against external high pressure and temperature. We will compare the results obtained from FLC, PSCOF, and PI-PSCOF modes by using the electro-optic measurement and x-ray scattering, and mechanical method. We believe that the PI-PSCOF technology can be a best candidate for future Flexible Display Applications.
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We optimized a patterned-vertical-alignment (PVA) transflective liquid-crystal (LC) cell for small pixel application. To achieve the high resolution display performance in the mobile communication equipments such as mobile phones, personal data assistants, and tablet personal computers, we optimized the parameters of liquid crystal and the electrode structure. Both the transmittance and the reflectance are maximized at the same time.
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We report on a high speed flexible display based on a deformed helix ferroelectric liquid crystal (DHFLC) in a vertically aligned configuration. The mechanical stability of the flexible DHFLC display was achieved using a periodic array of columnar spacers formed directly on the top sides of in-plane electrodes by the photolithography technique. Several unique features of display performances such as flexibility, uniform alignment, fast response, and gray scale capability were obtained.
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We have developed a transflective liquid crystal display (LCD) with a single cell gap and a low twisted nematic (LTN) mode in combination with a self-integrated retardation layer. The retardation layer was made of UV curable liquid crystalline material in one step of photo masking process and has both the homeotropic and the planar parts. The proposed transflective configuration has advantages in a simple fabrication process, and the possibility for a single driving scheme due to the similarity between the transmittance and the reflectance.
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To understand effects of carbon nanotubes (CNTs) dispersed in nematic liquid crystal (NLC) on electro-optic characteristic and orientation of the LC, we CNT-doped homogeneously-aligned NLC cells driven by in-plane field have been fabricated. The CNTs were aligned with a LC director from the initial state to below critical ac field, whereas the CNTs disturbed the LC director field above critical ac field. We observed motional textures in the form of vertical stripes in the local area between electrodes, which were associated with a deformation of the LC director orientation. This indicates that CNTs start vibrating three dimensionally with translational motion. Further, the hysterisis studies of voltage-dependent transmittance under dc electric field show that the amount of residual dc, which is related to image sticking problem in liquid crystal displays, is greatly reduced due to ion trapping by CNTS while keeping operating voltage and response time about the same compared to the un-doped LC cell.
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We have studied transflective liquid crystal displays (LCDs) associated with fringe-field switching (FFS) mode to achieve high image quality. In the past, several cell structures were used to fabricate transflective FFS liquid crystal display s. Their structures and characteristics are carefully examined to find their merits and cons. Further, optimization of cell parameters to achieve a single driving circuit is performed.
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Reflective paper-like display (PLD) using two types of particles having different electric polarity has been developed. A positive-charged particle has
$TiO_2$ , polymer and charge control agent (CCA), while a negative-charged particle consists of carbon black, polymer and CCA. We achieved fast response time (${\sim}0.2$ msec) and passive matrix driving addressing. These methods can easily be adapted to complete a large area display and flexible display. -
The fringe-field switching (FFS) mode associated with a transition from a homogenously aligned to twist deformation require rubbing process. In this devices,
$1^o$ of misalignment in an azimuthal direction could cause voltage-dependent transmittance (V-T) to be different from that in a normal area and consequently results in a rubbing mura. According to our studies, the single domain FFS cells are much more sensitive to the rubbing mura than the dual domain FFS cell. Moreover, the FFS cells with negative LC are much more sensitive to the rubbing mura than the FFS cells with positive LC. -
Although color characteristics of IPS mode are much better than TN or VA mode, there still remains a room for improvement of the color characteristics of IPS mode compared with the conventional CRT. It has been generally as sumed that inherent color variation of IPS mode is entirely owing to dependence of the effective retardation on wavelength and role of optical axis of IPS mode has been little considered. In this study, we investigated the effects of driving voltages on the effective retardation and the effective optical axis by a computer simulation. The result shows that rotation of effective optical axis is dependent on wavelength and tends to be smaller for larger wavelength.
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Jang, Chi-Woong;Lim, Tong-Kun;Kim, Moo-Jong;Kim, Ku-Nam;Kwon, Young-Wan;Jin, Jung-Il;Bae, Jung-Hun;Kim, Han-Sik 433
We have studied the realigning behavior of liquid crystal molecules in liquid crystalline polymer/liquid crystal(LCP/LC) system when they are exposed to external stimulation such as bending and pressing. The birefringence of the LCP/LC in a flexible display device was measured as a function of bending or pressing deformation. The microscopic dynamic behavior of main chain, side chain, and the LC were characterized by FTIR and polarization optical microscopy. When the device is deformed in scattering memory state, liquid crystal(LC) director is found to align from randomly oriented domain state(scattering state) to homeotropic state. -
We have investigated electro-optical properties of an in-plane switching cholesteric liquid crystal display (LCD). Planar and focal-conic texture changes re induced by application of an in-plane electric field.
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A polymer stabilization method is employed to reduce the transition time from field-induced homeotropic(H) state to reflecting planar(P) state in the cholesteric liquid crystal(ChLC) display. To stabilize ChLC by polymer, we mixed ChLC with diacrylate of 2
$wt%{\sim}6$ wt%. Two samples were made with different method of stabilization. For one sample the diacrylate of 2 wt% was polymerized with the ChLC in P state, while for the other sample diacrylate of 16 wt% was polymerized with ChLC in H state. In the former case, the transition time was 1000 times faster then those in the pure sample. In the latter sample, the transition time was 1700 times faster than those in pure ChLC sample. -
Kim, Dae-Woo;Jung, Moo-Sung;Won, Tae-Young;Yoon, Hyung-Jin;Lee, Cheol-Su;Yoon, Suk-In;Yoon, Sang-Ho 439
In this paper, we propose a cell structure to improve transmittance and aperture ratio with FFS(Fringe Field Switching) mode. As an exemplary cell, we selected conventional FFS cell with dual domain. Optical transmittance and aperture ratio were calculated with 3DFEM numerical solver, TechWiz LCD. The simulation results revealed that transmission increases by more than 10% while aperture ratio increases by more than 4% when compared to conventional FFS mode. -
Jung, Moo-Sung;Kim, Dae-Woo;Won, Tae-Young;Yoon, Hyung-Jin;Lee, Cheol-Soo;Yoon, Suk-In;Yoon, Sang-Ho 443
In this paper, we propose an MVA mode cell structure with improved optical characteristics. Our MVA cell has an electrode with fine-slits. Optical characteristics of our proposed structure were compared with those without fine-slits. Moreover, we varied the interval as well as the widths of fine-slits in order to appreciate the effect of fine-slits. Optical characteristics of these cells were calculated with 3DFEM solver, TechWiz LCD. It was confirmed that the transmittance can be improved by more than 7% with fine-slits. -
The alignment property of liquid crystals on the two-easy axes substrate is investigated. The two-easy axes substrate frustrates the orientation of the LCs next to the substrate, and hence influences the birefringence of the LC cell. Experimental findings reveal that the ratio of the rubbing strengths in the different rubbing directions and the cell thickness substantially influence the birefringence of the LC cell. The surface anchoring energetic competition between the different rubbing directions contributes to the observed results.
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The ion beam alignment technique is one of the potential and fascinating methods. However, there are merely a few reports about aligning nematic liquid crystals (NLCs) horizontally for in-plane switching mode (IPS) by means of low energy ion beam exposure on inorganic materials such as DLC. In this study, we have investigated the tilted vertical alignment of NLC by the ion beam technique on the thin films of various amorphous silicon compounds as new inorganic alignment materials. Appropriate pretilt angles of NLC with preferred orientation on these thin films were achieved. And the electro-optic property of vertically aligned single domain cells has been investigated.
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Color characteristics of a dark state in the IPS-mode depending on viewing direction have been studied. IPS-mode is having a little variation of
$d{\Delta}n$ with viewing angle since the LC rotates in plane. However, this mode shows asymmetric light leakage and color characteristics with viewing angle in a dark state. This drawback can be overcome by optimized retardation value of TAC film, pre-tilt angle &$d{\Delta}n$ of LC. -
Low viscosity LCs have been developed for fast response time improvement of the TFT-LCD Monitors based on TN mode. This low viscosity characteristic s cause the pretilt angle to be changed and the uniformity to degrade. We have studied on the pretilt angle effect by the various components used for low viscosity LCs. We prepared the panels by using these various components and measured pretilt angle for this research. As a result of this research, we have found out that each low viscosity component has the different pretilt angle level and uniformity. For good display quality, it is important to keep the stable pretilt angle. The low viscosity LCs with this stable pretilt angle make it possible to prepare the high performance TFT-LCD Monitor with both fast response time characteristics and good display quality
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Hwang, Jeoung-Yeon;Kang, Hyung-Ku;Seo, Dae-Shik;Oh, Byeong-Yun;Ham, Moon-Ho;Myoungr, Jae-Min 460
We studied the nematic liquid crystal (NLC) alignment capability by the Ultraviolet (UV) alignment method on a a-C:H thin -film , and investigated electro-optical performances of the UV aligned twisted nematic (TN)- liquid crystal display (LCD) with the UV exposure on a-C:H thin film surface. A good LC alignment by UV irradiation on a a-C:H thin -film surface was achieved. Monodomain alignment of the UV aligned TN-LCD can be observed. The good electro-optical (EO)characteristics of the UV aligned TN-LCD was observed with oblique UV exposure on the a-C:H thin film surface for 1min. -
Kim, Chul-Am;Myoung, Hey-Jin;Kang, Seung-Youl;Kim, Gi-Heon;Ahn, Seong-Deok;You, In-Kyu;Oh, Ji-Young;Baek, Kyu-Ha;Suh, Kyung-Soo 464
In this paper, we present techniques to manufacture color electronic ink for multi-color electrophoretic display implementation. The charged color pigments have been prepared to have superior affinity for dielectric fluid. White$TiO_2$ nanoparticles were modified with poly(methyl methacrylate) copolymer for a microencapsulated electrophoretic display system, in order to reduce the density mismatch between nanoparticles and dielectric medium. These color balls and white pigment particle suspensions were microencapsulated through the typical microencapsulation technique. We fabricate the microcapsules to the single layer on flexible ITO substrate to test the multi-color electrophoretic display application. -
Moon, Hyun-Chan;Kang, Hyung-Ku;Park, Chang-Joon;Hwang, Jeoung-Yeon;Seo, Dae-Shik;Lim, Sung-Hoon;Jang, Jin 468
We studied the nematic liquid crystal (NLC) aligning capabilities using the new alignment material of the SiC (Silicon Carbide) thin film. The SiC thin film exhibits good chemical and thermal stability. The good thermal and chemical stability makes SiC an attractive candidate for electronic applications. A vertical alignment of nematic liquid crystal by ion beam exposure on the SiC thin film surface was achieved. The about$87^{\circ}$ of stable pretilt angle was achieved at the range from$30^{\circ}$ to$45^{\circ}$ of incident angle. The good LC alignment is main-tained by the ion beam alignment method on the SiC thin film surface at high annealing temperatures up to 300. -
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The electrical performances of liquid crystal (LC) cells with chloromethylated polyimide (CMPI) alignment layers were investigated. The CMPI layer was previously reported as a multifunctional layer that does role of LC alignment and planarization layer as well as photo-alignment material with high photosensitivity and excellent thermal stability. The capacitance-voltage (C-V) characteristics of LC cells with CMPI alignment layers were measured. Mechanical rubbing of the CMPI layer did not generate much difference in residual DC when compared to commercial PI. However, the LC cell with photo-oxidation CMPI layer shows a high residual DC value and a corresponding low voltage holding ratio (VHR) due to the photo-induced ionic charges on the alignment layer.
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Lee, Burm-Young;Han, Jung-Hoon;Kwon, Soon-Bum;Buchnev, O.;Reznikov, Yu.;Tereshchenko, O.;Dusheiko, M. 476
We developed a plastic bistable LCD based on the suspension of sub-micron ferroelectric particles in a cholesteric liquid crystal. 2.5 inch$160{\times}160$ pixel display with enhanced contrast and improved electro-optical characteristics was achieved. The display is extremely light and possesses good flexibility, demonstrating multifold bending in a radius about 1.5 cm. -
Kim, Dong-Hoon;Park, Seo-Kyu;Kwon, Soon-Bum;Buchnev, Olexander;Kurioz, Yuriy;Kurochkin, Olexander;Tereshchenko, Olexander;Reznikov, Yuri 480
We report on studies of photoalignment of cholesteric liquid crystals on photosensitive phenylon-based polymer. We found that reflective and electro-optical characteristics of cholesteric cells strongly depend on UV exposure doze. The optimized UV treatment of the polymer allowed us to obtain the same quality of alignment on standard rubbed polyimide orientants. At the same time, the photosensitive orientant possesses evident advantage of the effective control of cholesteric textures -
In order to find out LC cell spacing method suitable for flexible cholesteric LCDs with high mechanical stability, we carried out bending and mechanical shock tests by using various spacing techniques: bead spacer, photo spacer, polymer wall with bead spacer and polymer wall with photo spacer. As a result, it was found that the spacing method using polymer wall incorporated with photo spacer is the best for flexible cholesteric LCDs in terms of mechanical stability. The investigation is discussed in detail.
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We report new polymer stabilized ferroelectric liquid crystal (PSFLC) cells with mechanical stability which is achievable by introducing photospacers in the cells. It was found that the mechanical st ability of the PSFLC cell was effected by introduction of photo spacers. We analyzed the dependence of mechanical stability and memory property on the density of photospacers in the PSFLC cell. The stability and memory properties of PSFLC Cells depending on photospacer density are discussed. 1. Introduction Recently, flexible displays have attracted much attention because they have remarkable advantages: thinner, lighter, non-breakable and conformable features. Flexible displays have various potential applications such as e-book and e-paper displays utilizing the distinct features. E-book and E-paper displays demand very low power consumption, so that bistable memory liquid crystal modes are required in case of flexible plastic LCDs for those application. Three kinds of memory LC modes have been developed; bistable nematic, bistable cholesteric and bistable FLC. Among them SSFLC as one of bistable FLC has big advantages such as low driving voltage, wide view angle and fast response time, SSFLC cells are, however, very weak against mechanical shock. Polymer stabilized FLC (PSFLC) has been developed to overcome the poor mechanical stability of SSFLC. PSFLC was known to have network structure that FLCs are oriented with smectic layer ordering in polymer network. The polymer network stabilizes the FLC orientation, which leads to improvement of mechanical stability of PSFLCD. A lot of studies have been done for the application of PSFLC to flexible
$LCDs.^{[1{\sim}12]}$ However, it should be noted that PSFLC does not have sufficient mechanical stability for the particular applications such as smart card LCD, where LCD is highly bendable.Bead spacer was mainly used to maintain cell gap of conventional PSFLCDs. But the spacer density of it is not locally uniform in the cell, so that it is generally difficult that the PSFLCDs with bead spacers show sufficient mechanical stability. In order to more improve the mechanical stability of PSFLCDs, we introduced photospacers into PSFLCDs. In this paper, we describe the improvement of mechanical stability by introducing photospacers into PSFLCDs. -
The director profiles of the Bloch walls are directly visualized using fluorescence confocal polarizing microscopy. Both pure twist Bloch walls and diffuse Bloch walls are analyzed. Polar anchoring energy was measured from optical simulation of the transmitted light interference pattern or the fluorescence intensity profile of a pure twist wall..
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We reported that high dielectric hafnium oxide nano-film deposited by thermal atomic layer deposition on the poly-silicon film (poly-Si). The poly -Si film was produced by plasma enhanced chemical vapor deposition and excimer laser annealing. We used the hafniu m chloride (
$HfCl_4$ ) and water as the precursors and analyzed the hafnium oxide film by transmission electron microscope and secondary ion mass spectrometer. Hafnium oxide produced by the ALD method showed very good coverage on the rough surface of poly-Si film. While deposited with 200 cycles, these hafnium oxide films revealed a relatively smooth surface and good uniformity, but the cumulative roughness produced by the incomplete reaction was apparent when the amount of deposition cycle increased to 600 cycles. -
One of representative techniques for compensation of LC's slow response characteristic is the Response Time Acceleration (RTA) technique. The conventional data definition for the RTA is based on the manual measurement and thus it takes long time. Therefore it is almost impossible to use panel specific compensation data in MP line. We have developed a new automated measurement system and flicker minimization for this purpose, which could achieve dramatic measurement time reduction, consistency over different operator, and optimized values as well. This system laid the groundwork for the application of image quality enhancement technologies to panels individually, and using this system, we can expect very uniform image quality for all LCD panels.
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The modeling for the cell gap process characteristic on the flexible liquid crystal display (LCD) process was investigated by response surface methodology (RSM). D-optimal design is carried out to build the design matrix. The analysis of variance (ANOVA) technique was used to analyze the significance level. The statistical analysis was used to verify the response surface model. The desirability function was used in the design-space optimization.
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As FPD technology is getting improved, there are a lot of issues on signal processing and analysis, and its relative importance has been increasing day by day. In particular, response time sad in the evaluation item of FPD has been measured by oscilloscope. In this paper, we propose an effective measurement method of response time in FPD. The proposed method is to calculate the rising/ falling time by using statistical techniques of histogram and analyzing an energy distribution. Ultimately, the method has proved the utility and reliability by comparison of oscilloscope
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In plasma processing reactors, it is common practice to control plasma density and ion bombardment energy by manipulating excitation voltage and frequency. In this paper, a dually excited capacitively coupled rf plasma reactor is self-consistently simulated with a three moment model. Effects of phase differences between primary and secondary voltage waves, simultaneously modulated at various combination of commensurate frequencies, on plasma properties are investigated. The simulation results show that plasma potential and density as well as primary self-dc bias are nearly unaffected by the phase lag between the primary and the secondary voltage waves. The results also show that, with the secondary frequency substantially lower than the primary frequency, secondary self-dc bias remains constant regardless of the phase lag. As the secondary frequency approaches to the primary frequency, however, the secondary self-dc bias becomes greatly altered by the phase lag, and so does the ion bombardment energy at the secondary electrode. These results demonstrate that ion bombardment energy can be more carefully controlled through plasma simulation.
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Youn, Hyung-Jin;Lee, Cheol-Soo;Jung, Moo-Sung;Kim, Dae-Woo;Yoon, Suk-In;Yoon, Sang-Ho;Won, Tae-Young 515
In this paper, we report on our theoretical study on the effect of surface anchoring. Molecular dynamics as well as optical characteristics of PVA cell are computer-simulated with 3D-FEM numerical solver, TechWiz$LCD^{(R)}$ . Although simulation parameters are the same except for the consideration of surface anchoring, the simulation reveals that optical transmittance is improved by more than 8% for the weak anchoring case with comparison to the strong anchoring case. Moreover, capacitance between pixel and common electrode is 7% lower for the strong anchoring than that for the weak anchoring. This implies that there exists an appreciable difference between the strong anchoring case and the weak anchoring case. It is very important to take the effect of surface anchoring into account in order to figure out the optical characteristics of an LCD cell more accurately. -
The electrooptical characteristics of OMI (optical mode interference) cell were investigated as the application for LC shutters. The optical responses under dynamic driving were simulated by solving the Ericksen-Leslie hydrodynamic equations numerically. The prototypes were made accordingly for verification. The experimental data show good coincidence with the simulation results.
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Chiu, Tien-Lung;Tseng, Wet-Yang;Chien, Chin-Cheng;Lo, Wei-Yu;Ting, Chu-Chi;Chang, Chia-Yuan;Chang, Chao-Jen;Sun, Oliver 522
The LED light source has many excellent advantages for the application of LCD backlight module. As we know, the operational temperature can significantly influence the characteristics of LEDs. Heat can damage the LED 's quality, and decrease its lifetime and output light intensity. In this paper, we perform computer software, Flomerics CFD (Computational Fluid Dynamics), to simulate heat distribution of the 20.1" LED backlight module we designing, and realize how the different heat sinks can solve the serious heat problem in practice. -
The LED light source has many excellent advantages for the application of LCD backlight module. As we know, the operational temperature can significantly influence the characteristics of LEDs. Heat can decrease LED's output light intensity and make its dominant wavelength (
${\lambda}d$ ) drift. These two factors make display's color temperature change and induce different NTSC results. Here, we perform an important relation between NTSC and the above two factors of LED-LCD display. -
In this paper, we present a new and practical method for achieving real-time wavefront measurement, dramatically increasing the resolution, dynamic range of Shack-Hartmann wavefront sensor and improving the wavefront reconstruction quality. In proposal method, a liquid crystal display panel (LCD) for the generation of an array of Fresnel microlenses is use instead of the static microlens array of the conventional Shack-Hartmann type sensor. An off-axis holographic microlens array is designed instead of the normal microlens array to increase the effective array and then the dynamic range. The focus properties of the off-axis lens are studied.
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This paper presents a new data line sharing technique for TFT-LCD panels. This technique reduces the number of data driver IC's to half by having two adjacent pixels share the same data line. This in turn doubles the number of gate lines, which are integrated directly on the glass substrate of amorphous silicon for further cost reduction and more compactness. The proposed technique with new pixel array structure was applied to 15.4 inch WXGA TFT-LCD panels and has proven that the number of driver IC's were halved with nearly 41% circuit cost reduction and 5.3% reduction in power consumption without degrading the image quality.
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We report the influence of the threshold voltage and mobility fluctuation in TFT on current mode digital circuit performance. We found that the threshold voltage showed more serious circuit malfunction. We studied new circuit configuration for improvement.
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We report how to establish the dynamic index for production control in a pilot fabrication over versatile and diverse production environments. We used dynamic index provided by a simulation model to monitor production performance. When production control is abnormal, the information system prompts administrators to classify these abnormal situations. In addition, the trend over the operation index is continuously reviewed in short-term and long-term. This simulation model is handy at setting goal for a versatile and diverse pilot production fab.
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We have investigated the alignment ability of multi-domains by using ion beam irradiation on diamond-like carbon (DLC) thin film layers. The DLC thin films were deposited by plasma enhanced chemical vapor deposition (PECVD) system and the low energy ion beam is irradiated from Kaufman type ion gun. The direction of liquid crystal alignment is varied by the direction of Ar ion beam irradiation.
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Zumer, Slobodan;Zalar, Bosjan;Lebar, Andrija;Chambers, Martin;Kutnjak, Zdravko;Finkelmann, Heino;Ferrer, Antoni Sanchez 553
The nature of the phase transition in nematic liquid crystalline elastomer is investigated using NMR and calorimetry. The balance between ordering and disordering effects of the polymer network is identified as crucial for the behavior of the order parameter near the phase transition. The change from supercritical to critical regime with adding low molecular weight liquid crystal to the elastomer is proven. -
In-situ photopolymerization of alkyl acrylate monomers in the presence of a nematic fluid provides a cellular matrix of liquid crystalline droplets in which the chemical structure of the encapsulating polymer exerts control over the alignment (anchoring) of the liquid crystalline molecules. Control is obtained by variation of the alkyl side chains and through copolymerization of two dissimilar monofunctional acrylates. Two monofunctional acrylates with opposing tendencies on copolymerization provide control over the tunability of anchoring over a wide temperature range. Using various acrylates we show that a uniform vertical alignment can be achieved over a large area. Utilizing this technique and a nematic with negative dielectric anisotropy, we have fabricated highly flexible liquid crytal based devices, with high contrast and fast response time, without using any alignment layer.
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Toshiba Matsushita Display Technology (TMD) has firstly succeeded in mass production of OCB (Optically Compensated Bend) mode liquid crystal display panels which have excellent moving picture quality almost the same as CRT. We have newly developed 32 -inch diagonal HD (
$1366{\times}768\;pixels$ ) panels using OCB mode and low temperature p-Si TFT (LTPS) array substrates. High performance of brightness of$600cd/m^2$ and contrast ratio of 600 : 1 was obtained by using pseudo-impulse driving method to insert a black period between continuous two frames, and also by using blinking backlight method. Furthermore, moving picture response time (MPRT) 6.5ms has been obtained by optimization of black insert driving and backlight blinking, without the great sacrifices of contrast ratio and luminance. -
Most researches on monostable LCD and bistable LCD have separately been carried out. We introduce a novel liquid crystal display mode which can be operated as both memory mode and dynamic mode. The novel LCD mode has not only a long term memory time of memory mode but also a fast response time of dynamic mode. We describe switching characteristics of dual mode. Electro-optical characteristics of memory mode and dynamic mode are unique and show the possibility of device application.
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High Speed Displays Based on a Nonchiral Smectic C Liquid Crystal in an Antiparallel Planar GeometryWe demonstrated a high speed liquid crystal (LC) display mode based on a nonchiral smectic C LC in an antiparallel planar geometry. In this antiparallel planar nonchiral smectic C (APNSC) LC mode, analog gray scales and wide viewing properties are achieved using a stepwise thermal annealing process (STAP). Because of an initially stable LC alignment in large area through the STAP, the APNSC LC mode exhibits the characteristics of fast response and high contrast ratio. This new APNSC mode is suitable for processing the dynamic image at a video rate in the next-generation LCDs.
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Miyazaki, Atsushi;Kawai, Hideyuki;Miyasaka, Mitsutoshi;Nebashi, Satoshi;Shimoda, Tatsuya;McCreary, Michael 575
A beautiful, flexible active-matrix electrophoretic display (AM-EPD) device is reported. The flexible AM-EPD device has a$40.0{\times}30.0\;mm^2$ display area, measures about 0.27 mm in thickness, weighs about 0.45 g and possesses only 20 external connections. The flexible AM-EPD device displays clear black-and-white images with 5 gray-scales on$160{\times}120$ pixels. The display is free from residual image problems, because we use an area-gray-scale method on$320{\times}240$ EPD elements, each of which is driven with binary signals. Each pixel consists of 4 EPD elements. In addition, since the response time of the electrophoretic material is as long as approximately 400 ms and since the display possesses a large number of EPD elements, we have developed a special driving method suitable for changing EPD images comfortably. A complete image is formed on the AM-EPD device, consisting of a reset frame and several, typically 6, image frames. -
Indium tin oxide (ITO) is a commonly used conducting transparent oxide film (CTO) used in flat panel display applications. Direct write laser ablation is sometimes employed for ITO patterning and it is important that the substrate material and remaining ITO be affected as little as possible by the laser ablation. In this investigation, femtosecond laser ablation of ITO was studied to identify laser processing parameters which cleanly ablated ITO with a minimum of damage to a glass substrate and surrounding ITO. The Ti:Sapphire chirp pulse amplified femtosecond laser used for the experiments had a wavelength of 775nm and produced pulses with a duration of 150fs at a rate of 2 kHz. Ablation was carried out at a sufficiently high panel scanning speed that single ablation spots could be studied. The pulse energy was adjusted to determine feasible spot diameters and depths which could be ablated into the ITO without damaging the glass substrate. Next, ablation of lines without glass damage was also demonstrated. Experiments were also performed with a high repetition rate (100kHz) femtosecond laser.
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It is well known that proper encapsulation is crucial for the lifetime of organic light emitting diode (OLED) displays. With the development of increasingly better barrier coatings and perimeter seals, it has now become very desirable to be able to precisely measure the rate of water vapor and oxygen permeation through barrier coatings and perimeter sealing. This paper demonstrates a new permeation measurement method that uses tritium-containing water (HTO) as a tracer material. The theoretical detection limit of this direct method is
$2.4{\times}10^{-8}g/(m^2day)$ . -
This paper shows that the defect detection in TFTarray panel can be improved by using newly developed software solution without adding additional hardware instruments. Some issues are reviewed in current TFT array test and new algorithm is explained for detecting more real defects without paying the penalty of reporting more false defects in TFT array test.
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Z-correction is new method to be used when measuring pattern registration of photomasks. The method is based on measurement of the plate profile in the Zaxis and takes into account the impact on the registration deviations caused by plate support, contamination as well as the photomask flatness itself. Z-correction further facilitates a more neutral way of judging the overlay properties between individual photomasks within a mask set.
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In this paper, we present a model to calculate the influence of the measurement spot diameter MSD on the viewing angle measurements using a conoscopic instrument. This model is verified experimentally using an EZContrast instrument and the requirements for next generation of displays are presented. We show that last generation of EZContrast XL88W and L80W allowing measurement spot diameter up to 6mm can fulfill the requirements for all the FPD generations up to 80 inches diagonal.
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Hack, Mike;Chwang, Anna;Hewitt, Richard;Brown, Julie;Lu, JengPing;Shih, ChinWen;Ho, JackSon;Street, R.A. 609
Advanced mobile communication devices require a bright, high information content display in a small, light-weight, low power consumption package. In this paper we will outline our progress towards developing such a low power consumption active-matrix flexible OLED ($FOLED^{TM}$ ) display. Our work in this area is focused on three critical enabling technologies. The first is the development of a high efficiency long-lived phosphorescent OLED ($PHOLED{TM}$ ) device technology, which has now proven itself to be capable of meeting the low power consumption performance requirements for mobile display applications. Secondly, is the development of flexible active matrix backplanes, and for this our team are employing poly-Si TFTs formed on metal foil substrates as this approach represents an attractive alternative to fabricating poly-Si TFTs on plastic for the realization of first generation flexible active matrix OLED displays. Unlike most plastics, metal foil substrates can withstand a large thermal load and do not require a moisture and oxygen permeation barrier. Thirdly, the key to reliable operation is to ensure that the organic materials are fully encapsulated in a package designed for repetitive flexing. We also present progress in operational lifetime of encapsulated T-PHOLED pixels on planarized metal foil and discuss PHOLED encapsulation strategy. -
The use of plastic substrates enables new applications, such as flexible display devices, and other flexible electronic devices, using low cost, roll-to-roll (R2R) fabrication technologies. One of the limitations of polymeric substrate in these applications is that oxygen and moisture rapidly diffuse through the material and subsequently degrade the electro-optical devices. GE Global Research (GEGR) has developed a plastic substrate technology comprised of a superior high-heat polycarbonate (
$LEXAN^{(R)}$ ) substrate film and a unique transparent coating package that provides the ultrahigh barrier (UHB) to moisture and oxygen,chemical resistance to solvents used in device fabrications, and a high performance transparent conductor. This article describes the coating solutions for polycarbonate ($LEXAN^{(R)}$ ) films and its compatibility with OLED device fabrication processes. -
OLED display are extremely sensitive to water and oxygen. Developing a thin film encapsulation for this technology has for a long time been elusive. Vitex has developed a multilayer barrier consisting of alternating inorganic and organic layers which can meet the requirements for a successful protection for such displays. In this paper we will discuss the basic process, the model, the results on top and bottom emission OLED displays as well as the application of Barix layers on plastic to create flexible OLED displays. We will show that for displays all the requirement for the telecommunication industry can be met and that the we can scale up to a mass manufacturing process.
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DuPont Teijin Films (DTF) have developed a family of films engineered specifically for the flexible electronics market.
$Teonex^{(R)}Q65A$ is a biaxially oriented crystalline polyester with an engineered surface and it is emerging as a competitive material for the base substrate in OLED displays and active matrix backplanes. This contribution will describe the properties of this film, its uniquely different property set compared to amorphous high performance films and discuss examples of the film in use in flexible electronic applications. -
In this paper, several energy recovery circuits (ERC) for the plasma display panel (PDP) are reviewed and classified in a manner of operation characteristics. A typical ERC using the Regenerative Transformer (RT) is introduced and compared with conventional ones. RT-ERC can achieve zero-voltage-switching (ZVS) for main full-bridge switches and zero-current-switching (ZCS) for the resonant switches and diodes. The charging/discharging energy of panel capacitance is efficiently recovered with the RT and without a sub-circuit. The presented circuit is verified with simulation and experimental results.
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We propose a new address-while-display (AWD) driving method to obtain a high contrast ratio and a wide driving margin which is composed of a short ramp reset period, a sustain period and an address period as the basic unit. The short ramp reset (SRR) pulse made it possible to assure the wide operating voltage margin and minimize the background luminance by redistributing the wall charges between address and scan electrode. As a result, a high dark room contrast ratio of 10000 to 1 could be obtained with a wide operating voltage margin of 40V for stable address.
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Chen, Jyh-Wei;Lee, Chin-Yuan;Lu, Chien-Hung;Wang, Ssu-Hao;Hsia, Yi-Feng;Chang, Wei-Chun;Mo, Chi-Neng;Liu, Chia-Lin;Yang, Sung-Tse 635
An energy recovery sustaining driver with zero current switching to reduce switching losses and EMI is presented in this paper. The driver with designed snubber circuits reduces ringing voltage significantly on PDP so that the voltage rating of MOSFETs can be lower as well to reduce the cost of switches. -
A new dual-slope ramp (DSR) reset waveform is proposed to improve the dark room contrast ratio in AC-PDPs. The proposed reset waveform has two different voltage slopes during a ramp-up period. The first voltage slope is lower than the conventional ramp voltage slope, causing a reduction in the background luminance, whereas the second voltage slope is higher than the conventional ramp voltage slope, causing an increase in the background luminance. Thus, a bias voltage is also applied during the second voltage-slope period to adjust the background luminance and address discharge characteristics. As a result, the proposed dual-slope reset waveform can lower the background luminance, thereby improving the high dark room contrast ratio of an AC-PDP without reducing the address voltage margin
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We present new ramp-reset waveforms that realize fast addressing in AC-PDPs. These waveforms distort the distribution of wall charges on the surface of a phosphor layer: hence, the enhanced electric field helps to ignite a cell faster. They also reduce the black luminance: the divide of erasing ramp down discharges into two parts, i.e. a surface discharge and a vertical discharge, makes lower luminance.
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Jung, Kwang-Sig;Kim, Gop-Sig;Shin, Seung-Rok;Chae, Su-Yong;Kim, Dae-Hwan;Yoo, Min-Sun;Cho, Yoon-Hyoung 647
A new driving scheme, Address and Display Period Complex Driving for Expanding Gray Scale(ACE), is proposed by mixing Address Display period Separated(ADS) and Address While Display(AWD). In this method scan lines are divided in blocks driving by AWD and scan lines in block progress sequential high speed addressing. ADS driving get accomplished in low gray level for expanding gray scale. Scan time is reduced and the number of subfields is increased by high speed addressing of ACE. That expands the gray scale and decreases the dynamic false contour. Also, that improves contrast by using ramp reset. -
New charge-recycling structure and driving scheme for TFT-LCD source-driver IC application are proposed. The number of additional switches for the charge recycling is greatly reduced. An experimental prototype 6-bit source driver with five-level seven-phase charge recycling implemented in a
$0.35-{\mu}m$ CMOS technology demonstrates that the quiescent current is only 3.1 mA, dynamic power saving is 75 %, and the settling time, which includes the charge-recycling and data driving, is within 25$25{\mu}s$ . -
Jang, Chul-Sang;Yoo, Juhn-Suk;Lee, Dong-Hoon;Kim, Jong-Hoon;Chung, In-Jae;Kim, Jin-Ho;Choi, Jin-Chul;Lee, Jae-Sic;Kim, Seon-Yung;Kwon, Oh-Kyong 657
We designed 10bit source driver LSI, then the high color depth and the low power consumption are realized thru it. It is adopted mini-LVDS receiver with high speed data transmission and good data recovery performance, Hybrid type DAC to reduce decoder size and OP-AMP with low power consumption and high slew rate. In addition we show our results of the 10-bit gray scale TFT-LCD source driver for 42inch diagonal size and WXGA resolution TFT-LCD TV applications. -
This paper presents a new technology, Advanced Dynamic Capacitance Compensation (A-DCC), for improved dynamic performance of LCD monitors. Conventional LCD monitors suffer from certain specific artifacts, such as wire-frame flicker and line dimming, which are not an issue for the simpler motion images found in television content. A-DCC addresses these more challenging monitor cases through an advanced architecture which analyzes multi-frame data and applies more comprehensive lookup table corrections according to the specific frame sequence.
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VIATRON TECHNOLOGIES has developed FE-RTP system that enables LTPS LCD and AMOLED manufacturers to produce poly-Si films at low cost, high throughput, and high yield. The system employs sequential heat treatment methods using temperature control and rapid thermal processor modules. The temperature control modules provide exceptionally uniform heating and cooling of the glass substrates to within
${\pm}2^a\;C$ . The rapid thermal process that combines heating with field induction accelerates the treatment rates. The new FE-RTP system can process$730{\times}920mm$ glass substrates as thin as 0.4 mm. The uniform nature of poly-Si films produced by FE-RTP resulted in AMOLED panels with no laser-Muras. Furthermore, FE-RTP system also showed superior performances in other heat treatment processes involved in poly-Si TFT fabrications, such as dopant activation, gate oxide densification, hydrogenation, and pre-compaction. -
Hwang, Changhun;Han, Seung-Jin;Kim, Do-Gon;Yook, Sim-Man;Kim, Seung-Han;Kim, Jin-Hyung;Kim, Beom-jai;Won, You-Tae;Park, Ki-Joo;Kim, Kwang-Ho;Kim, Byung-Seok;Kang, Teak-Sang;Kim, Jung-Hwan;Seo, Sang-Won;Song, Ha-Jin;Sim, Hyung-Bo;Noh, Young-Bo 668
Doosan DND, OLED manufacturing equipment maker, has developed the largest deposition system to produce$730{\times}920mm$ size AMOLED devices for the first time in the world. It is necessary for producing 40" AMOLED panels to develop the large-scaled vacuum technologies including ICP plasma, stretching glass chuck, organic deposition, metal deposition and hybrid encapsulation processes. -
Ink jet printheads are now widely used in manufacturing processes that require precise dispensing of materials. Today, Dimatix manufactures a variety of drop-on-demand ink jet printheads for the industrial printing market, but emerging opportunities present fresh challenges to our technology. In response to requirements for digitally printing on flexible substrates and dispensing novel electronic fluids, we are developing next generation jetting technology based on our three-dimensional silicon MEMS technology with a piezo-driven pumping chamber integrated into the chip structure. This presentation will address the functional and physical design features and properties of Dimatix's MEMS process, its characteristics, reliability and usability. Examples of opportunities and applications for digitally printing electronic fluids on flexible substrates with MEMS-based ink jet technology will be presented.
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Nobari, Ali Reza;Mourgue, Stephane;Clube, Francis;Jorda, Mathieu;Iriguchi, Chiharu;Inoue, Satoshi;Grass, Elmar;Mayer, Herbert 676
Future Mobile displays and the emerging systems on Glass for the upcoming TFT_LCDs or Active-OLEDs based on LTPS, and the exciting c-Si critically require very-high resolution lithography. We report the methodology and latest results on the alignment, magnification control and stitching systems on a HMA500 holographic mask aligner for printing$0.5{\mu}m-resolution$ display patterns onto glass substrates of dimensions up to$500mm{\times}400mm$ . -
In this study, we investigate the characteristic of the poly-Si grain and morphology influenced by XeCl excimer laser system. The stable laser beam source is basic requested; the irradiation beam through optical lens module is more important which limit the grain size smaller than
$0.5{\mu}m$ . The homogenization lens designs control the poly-Si grain size; so we hardly get enlarge grain size by one laser irradiation scan. -
We demonstrated stability-enhanced liquid crystal (LC) displays using pixel-iosolated LC mode in which LC molecules are isolated in pixel by horizontal polymer layer and vertical polymer wall. The device shows good electro-optic properties with external pressure and bending due to the polymer structures. The polymer wall acts as supporting structure from mechanical pressure and maintains the cell gap from bending. Moreover, the polymer layer acts as adhesive for tight attachment of two substrates. We presented various methods to produce the polymer structures by using anisotropic phase separation from LC and polymer composites or patterned micro-structures.
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In an attempt to fabricate all inclusive display systems we are presenting a study on several elements that would be used as building blocks for all-on-board integrated applications on stainless steel foils. These systems would include in the same substrate all or many of the components needed to drive a flat panel OLED display. We are reporting results on both digital and analog circuits on stainless steel foils. Shift registers running at speeds greater than 1.0MHz are shown as well as oscillators operating at over 40MHz. Pixel circuits for driving organic light emitting diodes are presented. The device technology of choice is that based on poly-silicon TFT technology as it has the potential of producing circuits with good performance and considerable cost savings over the established processes on quartz or glass substrates (amorphous Silicon a-Si:H or silicon on Insulator SOI).
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Street, R.A.;Wong, W.S.;Ready, S.E.;Chabinyc, M.L.;Arias, A.C.;Daniel, J.H.;Apte, R.B.;Salleo, A.;Lujan, R.;Ong, Beng;Wu, Yiliang 697
The need for low cost flexible TFT display backplanes has focused attention on new processing techniques and materials. We have developed backplane technology based entirely on jet-printing, using a combination of additive and subtractive processing, and have applied this technique to both amorphous silicon and polymer TFT arrays. -
Seo, Jong-Hyun;Jeon, Hyung-Il;Nikulin, Ivan;Lee, Woo-Jae;Rho, Soo-Guy;Hong, Wang-Su;Kim, Sang-Il;Hong, Munpyo;Chung, Kyuha 700
A 5.0-inch transmissive type plastic TFT arrays were successfully fabricated on a plastic substrate at the resolution of$400{\times}3{\times}300$ lines (100ppi). All of the TFT processes were carried out below$150^{\circ}C$ on PES plastic films. After thin film deposition using PECVD, thin film failures such as film delamination and cracking often occurred. For successful growth of thin films (about 1um) without their failures, it is necessary to solve the critical problem related to the internal compressive stress (some GPa) leading to delamination at a threshold thickness value of the films. The Griffith's theory explains the failure process by looking at the excess of elastic energy inside the film, which overcomes the cohesive energy between film and substrate. To increase the above mentioned threshold thickness value there are two possibilities: (i) the improvement of the interface adhesion (for example, through surface micro-roughening and/or surface activation), and (ii) the reduction of the internal stress. In this work, reducing a-Si layer film thickness and optimizing a barrier SiNx layer have produced stable CVD films at 150oC, over PES substrates -
In order to clarify the heat annealing process for Magnesium Oxide (MgO), cathodoluminescent (CL) analysis was performed. Our results in the present work prove that the heat annealing has effects on not only removing water from the surface of MgO, but also increasing density of O and Mg defect pairs. It is the first work that the influence of annealing process on physical properties of the vacuum evaporated MgO thin films by using CL spectra.
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In this study, waffle type barrier ribs for counter electrode discharge cells were prepared via micro-molding process. The master mold was prepared by UV lithography and working mold was manufactured by replicating the master mold. The UV paste used in this study consisted of ceramic powders for the barrier ribs, binder, hardener, and dispersant was filled into cavities of a polymeric mold by action of capillary pressure developed between mold and paste. The results demonstrated a possibility of one-step process for the manufacturing of waffle type barrier ribs embedded with sustaining electrodes.
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We studied the dependence of the electrical characteristics of MgO protecting layer on temperature in an AC PDP cell. Careful measurements of the surface resistance of MgO were performed for the temperature range from room temperature to
$100^{\circ}C$ with and without the VUV illumination. Experimental results show that the resistivity is affected by not only the temperature but also VUV irradiation. The measurement of wall charge distribution and the address discharge delay time as to the temperature show that the resistivity change of MgO may affect the wall voltage and consequently the discharge delay time. -
Hydrothermal synthesis and photoluminescence properties of nanocrystalline
$GdBO_3:Eu^{3+}$ phosphorNanocrystalline$GdBO_3:Eu^{3+}$ was prepared by a hydrothermal method. The as-synthesized powders were spherical shaped agglomerates of nano particles. The luminescent properties were compared with samples synthesized by conventional solid-state reaction method. Both the photoluminescence intensity and chromaticity were improved and a red-shift in the CT band was observed for the hydrothermally synthesized samples. -
Seo, Gi-Weon;Kim, Jong-Bin;Park, Seung-Tea;Seo, Young-Woo;Kim, Sung-Gyu;Lee, Sang-Han;Lee, Chang-Joon;Kim, Dae-Young;Park, Min-Soo;Kim, Je-Seok;Ryu, Byung-Gil 721
We applied the Atmospheric Pressure Plasma (AP-plasma) to the MgO film to try to control the Aging-time on the PDP production-line. The MgO film surface and the discharge characteristics of AC-PDPs were investigated, using the plasma-treated MgO film. The Aging-time change can be achieved by treating the MgO film with plasma. This method can be adapted to the mass production-line. -
Design and manufacturing process of a full color LED microdislay fabricated by standard CMOS technology and containing an array of aluminum / nanostructured porous silicon reverse biased light emitting Schottky diodes will be discussed. Being of a solid state construction, this microdisplays are cost-effective, thin and light in weight due to very simple device architecture. Its benefits include also super high resolution, wide viewing angles, fast response time and wide operating temperature range. The advantages of full integration of an LED-array and driving circuitry onto a Si-chip will be also discussed.
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Discussion of this study is that a horizontal deflection system satisfactory of operating at horizontal scan rates from 30KHz to 50KHz has been developed. It will be used in the large-area, color, high-resolution and multi-sync rear-projection CRT display device. Its characters, including the description, analysis and deflection circuit loss, are presented.
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To increase light efficiency, utilizing phosphors transfers ultraviolet ray to visible light and the fluorescent characteristic without change the electrical or optical design. Spreading phosphors on the surface of light bulb mirror can compensate the red and blue light to yield this correct white field after being stimulated by reflected ultraviolet ray.
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The discussion of this study is that we proposed a new construction to improve the potency of LCOS projection monitor. We suggest a new construction that uses special optics coating to reduce the green channel and obtains a purer white field. Compared with the voltage method to adjust on the monitor, we can get higher contrast gradient.
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The exploitable efficiency of UHP is very important in a projection system. We always use lens array for light shaping and energy distribution transformation in conventional projection system. Because of the limitation of arc gap and F/# of elements, the utilize efficiency is always dismal. In this paper we try to bring out a new method to reduce the sparkle formed on the PS converter and enhance the system efficiency.
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In direct-projected augmented reality, different position of user requires different projection on 3-D display surface. The problem is caused by the difference between the direction of projector-to-object and the direction of user-to-object. In this paper, it is demonstrated that the graphical contents are properly pre-warped according to user's viewpoint and projected onto 3-D display surface without geometric distortion.
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The mechanism responsible for liquid crystal (LC) alignment on solid substrates treated with mechanical rubbing or polarized UV is not understood. The results of x-ray reflectivity study of LC alignment on a large number of different alignment layers show that the anisotropy in the surface roughness of the substrate completely determines the LC alignment. The anchoring energy depends on the degree of roughness anisotropy and chemical interactions between the substrate and LC molecules.
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This review presents the status of our research in liquid crystal display (LCD) photo-aligning. We present the basic mechanisms of the photo-induced order in various photo-aligning materials and in azo-dye layers in particular and show that photo-aligning methods can provide a controllable pretilt angle and anchoring energy of the liquid crystal cell, as well as its high thermo and UV stability. The photo-aligning of various types of liquid crystal displays is also discussed.
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Reznikov, Yuri;Buluy, Olexander;Kurioz, Yuriy;lljin, Andery;Ouskova, Elena;Antonova, K.;Nobili, Maurizio 764
Photoaligning polymers usually possess "sofe" surface, containing flexible groups and provide relatively small anchoring energy($W < 10^{-2}$ erg$cm^{-2}$ ). In this case field-induced reorientation of director on the aligning surface is essential. We have shown that surface director reorientation can modify the aligning surface and result in gliding of the axis of easy orientation of LC. this phenomena together with adsorption/desorption of ions in electric field cause strong sticking effect in LCDs photoaligning materials. We proposed a method of decreasing of the sticking effect based on irradiation of the photoaligning surface by an unpolarized light. -
Yaroshchuk, O.V.;Liu, P.C.;Lee, C.D.;Lee, C.Y.;Kravchuk, R.M.;Dobrovolskyy, A.M.;Protsenko, I.M.;Goncharov, A.A.;Lavrentovich, O.D. 768
We present an overview of our new method of liquid crystal (LC) alignment based on the anisotropic etching of the alignment layers with a directed plasma flux. The method is realized by the use of anode layer source of "race track" geometry generating two "sheets" of accelerated plasma. These sheets are directed obliquely to the treated substrates. The static and dynamic irradiation regimes have been explored. The optimized processing conditions and materials are discussed. The technique yields an excellent uniformity of liquid crystal alignment of planar, tilted and vertical types. It is shown that the new method can be easily adapted for the alignment treatment of large area substrates used in the modern LCD manufacturing process. -
In this work, a soft embossing method is proposed to fabricate microgrooves on polyimide surfaces. Apply these resulting patterned micro-grooved polyimide surfaces as the liquid crystal alignment layers. The director of liquid crystal molecules aligns perfectly along the direction of microgrooves.
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Chung, K.;Huh, J.M.;Sung, U.C.;Chai, C.C.;Lee, J.H.;Kim, H.;Lee, S.P.;Goh, J.C.;Park, S.K.;Ko, C.S.;Koh, B.S.;Shin, K.J.;Choi, J.H.;Jung, J.H.;Kim, N.D. 781
We have developed technology to fabricate large-size active matrix organic light-emitting diode (AMOLED) displays with good color purity. Using these innovations, we have developed a 40inch diagonal WXGA AMOLED full color display. Because the TFT circuitry occupies a large portion of the pixel structure, an efficient white emission OLED is essential to integrate the device onto the active matrix backplane. The development of these technologies enables OLED displays to fulfill the requirements for larger size applications such as HDTVs -
Hong, Wan-Shick;Lee, Sung-Hyun;Cho, Chul-Lae;Lee, Kyung-Eun;Kim, Sae-Bum;Kim, Jong-Man;Kwon, Jang-Yeon;Noguchi, Takashi 785
Low temperature deposition of silicon and silicon nitride films by catalytic CVD technique was studied for application to thin film transistors on plastic substrates for flexible AMOLEDs. The substrate temperature initially held at room temperature, and was controlled successfully below$150^{\circ}C$ during the entire deposition process. Amorphous silicon films having good adhesion, good surface morphology and sufficiently low content of atomic hydrogen were obtained and could be successfully crystallized using excimer laser without a prior dehydrogenation step.$SiN_x$ films showed a good refractive index, a high deposition rate, a moderate breakdown field and a dielectric constant. The Cat-CVD silicon and silicon nitride films can be good candidates for fabricating thin films transistors on plastic substrates to drive active-matrix organic light emitting display. -
In this work we attempted to find the origin of brightness non-uniformity in SLS poly-Si TFT AMOLED. By developing a suitable SLS process with a compensation circuit, we have successfully improved the non-uniformity from 40% to 1.7%. We could fabricate 2.2" AMOLED display using SLS poly-Si.
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Jung, J.H.;Goh, J.C.;Choi, B.R.;Chai, C.C.;Kim, H.;Lee, S.P.;Sung, U.C.;Ko, C.S.;Kim, N.D.;Chung, K. 793
A structure and a design of device were developed to fabricate large-scale active matrix organic light-emitting diode (AMOLED) display with good color purity and high aperture ratio. With these technologies, we developed a full color 14.1 inch WXGA AMOLED display. For the integration of OLED on an active matrix a-Si TFT backplane, an efficient top emission OLED is essential since the TFT circuitry covers a large position of the pixel aperture. These technologies will enable up the OLED applications to larger size displays such as desktop monitors and TVs. -
Kim, Mu-Hyun;Chin, Byung-Doo;Suh, Min-Chul;Yang, Nam-Chul;Song, Myung-Won;Lee, Jae-Ho;Kang, Tae-Min;Lee, Seong-Taek;Kim, Hye-Dong;Park, Kang-Sung;Oh, Jun-Sik;Chung, Ho-Kyoon 797
We report a novel structure for a full-color AMOLED (Active Matrix Organic Light Emitting Diode) eliminating the patterning process of a blue emitting layer. The patterning of the three primary colors, RGB, is a key technology in the OLED fabrication process. Conventional full color AMOLED containing RGB layers includes the three opportunities of the defects to make an accurate position and fine resolution using various technologies such as fine metal mask, ink-jet printing and laser-induced transfer system. We can skip the blue patterning step by simply stacking the blue layer as a common layer to the whole active area after pixelizing two primary colors, RG, in the conventional small molecular OLED structure. The red and green pixel showed equivalent performances without any contribution of the blue emission. -
Tsai, Cheng-Hung;Chiu, Chen-Lun;Chen, Cheng-Ming;Shih, I-Cheng;Tang, Shun-Jyun;Huang, Chun-Yao 799
This paper described a 2.2"$QCIF^+$ ($176{\times}RGB{\times}220$ ) active matrix organic light-emitting diode display (AMOLED) using low-temperature poly-silicon (LTPS) technology. We have designed the OLED pixel to match the OLED material characteristic with COG specification and optimized pixel structure to improve color gamma adjustment and simplify signal complexity. -
A basic assessment is presented of the technical, economic and strategic challenges expected for manufacturing displays in a roll-to-roll format. Two general pathways are considered; one that results in dramatic cost reductions but results in sacrificing product performance, and another which is an extension of the conventional FPD cost-reduction from increased substrate size. While Roll-to-Roll fabrication is fundamentally possible, feasibility experiments will be required to address the most significant technical challenge: achieving and managing acceptable yield. In all respects, the efforts to achieve RTR manufacturing will be assisted by overlapping interests in other application areas such as flex circuit, photovoltaics and large area lighting.
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Inexpensive large area arrays of thin film transistors (TFTs) on flexible substrates will enable many new display products that cannot be cost effectively manufactured by conventional means. This paper presents a new approach for low cost manufacturing of electronic devices using roll-to-roll (R2R) processes exclusively. It was developed in partnership by Hewlett Packard Laboratories and Iowa Thin Film Technologies (ITFT), a solar cell manufacturer. The approach combines ITFT's unique processes for vacuum deposition and etching of semiconductors, dielectrics and metals on continuous plastic webs with a method HP has invented for the patterning and aligning the multiple layers of a TFT with sub-micron accuracy and feature size.
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Purpose-built ink jet printheads are being recognized as useful tools in manufacturing where precision deposition is required. Ink jet technology is a non-contact, non-contaminating digital process compatible with clean rooms. New manufacturing applications are driving printhead designs to smaller drops, increased productivity. This paper describes Dimatix's new tools designed to facilitate development of manufacturing processes for both rigid and flexible substrates and development of new electronic fluids.
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In this paper, we describe how specially developed polymer capped, nano-particle silver inks can be used to print circuitry for applications like displays, RFID antennas and "disposable electronics". The requirements of printing on temperature sensitive flexible substrates (such as polymer films and papers) that require low temperature curing is also discussed.
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Jeng, Shie-Chang;Lin, Yen-Rong;Liu, Kang-Hung;Liao, Chi-Chang;Wen, Chao-Hua;Chao, Chih-Yu;Shieh, Kong-King 817
Legibility of electronic paper was evaluated by using the method of letter-search task and subjective visual comfort scaling. The results show that legibility depends on the illumination level, and conventional paper has a higher visual comfort rating than electronic paper although they have the similar performance in the letter-search task.