Jun-Hyung Souk

51.2: Reducing Gray-Level Response to One Frame: Dynamic Capacitance Compensation

A novel driving scheme, named Dynamic Capacitance Compensation (DCC), for active-matrix (AM) LCDs was developed. It takes the charge-&-hold nature of AM-LCDs into consideration to enhance the switching speed. By incorporating DCC and faster liquid crystal, a TFT-LCD whose response time was less than 10 ms for all gray levels with the on + off time of 8.4 ms was developed. DCC can be applied to any kind of LCD modes to reduce the gray response time to less than 1 frame.

9.2: Sequential Lateral Solidification (SLS) Process for Large Area AMOLED

We have demonstrated that the sequential lateral solidification (SLS) technology can be utilized for the large area AMOLED. An optimized SLS process provides us with polycrystalline Si films with well-controlled grain size and location. The thin film transistors (TFTs) with SLS-processed Si films show high performance with desirable uniformity. 14″ WXGA (1280×RGB×768) AMOLEDs were fabricated with SLS-processed TFT backplanes. We utilized RGB evaporation process with fine metal mask. The novel delta pixel arrangement results in increased aperture ratio and wider FMM process window. The advantage of SLS process will be discussed.

70.4: A 14.1inch AMOLED Display using Highly Stable PECVD based Microcrystalline Silicon TFT Backplane

We have developed a 14.1 inch AMOLED display using microcrystalline silicon (mc-Si) TFTs. Microcrystalline silicon was deposited using conventional 13.56MHz Plasma Enhanced Chemical Vapor Deposition (PECVD). Detailed thin film characterization of mc-Si films was followed by development of mc-Si TFTs which show a field effect mobility of around 0.7∼1.0cm2/V.s. The mc-Si TFTs show no significant shift in threshold voltage when applied with a long time constant current stress, indicating a stable TFT backplane. The mc-Si TFTs were successfully integrated in a 14.1 inch AMOLED display. The display shows no significant current decrease in the driving TFT of the 2T circuit, even after long time of lifetime tests. Along with improved lifetime for AMOLED display, the development of mc-Si TFTs using conventional 13.56 MHz PECVD system offers significant cost advantages over other laser or non-laser polysilicon TFT technologies for AMOLED.

69.4: Amorphous Silicon Based 40″ LCD TV Using Ultra Fast OCB Mode

The worlds largest (40 inch) size a-Si TFT-LCD HDTV (1366 × 768) panels based on OCB (optically compensated bend) mode has been successfully developed using newly developed impulsive driving method, which shows the contrast ratio over 500, viewing angle over 160 degree for all direction, brightness over 600 cd/m2 and MPRT in the range of 7 ∼ 10ms. Especially, transmittance and viewing quality of the motion picture have been remarkably enhanced by gray impulsive driving (GID) method. We are now continuing further research in order to improve the contrast ratio and reliability for commercialization.

P‐3: Panel Transmittance Analysis of PVA Mode and a Noble Pixel Design

Vertical Alignment mode TFT-LCD is divided into MVA mode through formation of protrusion, PVA mode that uses color filter ITO patterning and etc. Among these, R&D of PVA (Plus Viewing Angle) mode accomplished the practical Wide Viewing Angle through the several technical phases. The multi-domain structure by the effect of fringe-field and the application of biaxial compensation film are the examples. PVA mode has a characteristic of high transmittance compared other Wide Viewing Angle mode. However the recent requirements of diversification of a use and the requirements of improvement of a screen quality make the transmittance diminished by modification the cell parameter and etc. In the experimentation hereunder the structure of Gradual Y-slit has accomplished over 10% of transmittance than the existing chevron pattern by applying this to T-pattern. And the produced 17″SXGA T-pattern panel shows the characteristics of 300 nits of brightness, 65% of color gamut, 600:1 contrast ratio and 25ms response time.

P-93: High Performance 17.0″ SVGA OCB Panel with Fast Initial Bend Transition

Recently, the vigorous researches on the moving picture quality of TFT-LCDs have been made to overcome their drawbacks in replacing CRTs for TV application. Among them, the fast response OCB mode is thought to have the highest potential for TV application, even though its image quality still needs to be improved. In this regard, we have optimized the cell parameters of OCB mode to get wide viewing angle, high contrast ratio and transmittance as well as the fast response time. Based on these parameters, we have improved image qualities remarkably by adopting these to 17.0″ SVGA proto-panel, which shows the contrast ratio over 250, viewing angle over 80 degree for all direction except rubbing direction, response time under 7 ms including inter-gray scale and the transmittance of 90% of TN mode. Especially, by adopting new driving scheme, we considerably reduced the initial bend transition time, which is known as one of drawbacks in OCB mode. We are continuing further research to get the competitive image quality and good reliability, which is comparable to commercially used PVA or IPS mode.

P-259L: Late-News Poster: A 14inch Uniform AMOLED Display with Low Cost PECVD Based Microcrystalline Silicon TFT Backplanes

This paper discusses development of uniform 14.1 inch AMOLED display using PECVD based microcrystalline silicon (mc-Si) TFTs. Microcrystalline silicon was deposited using conventional 13.56 MHz Plasma Enhanced Chemical Vapor Deposition (PECVD) with novel gas precursors. The mc-Si TFTs show a field effect mobility of around 1cm2/V.s and off-current less than 1pA. Electrical stress on mc-Si TFTs for a long time shows no significant threshold voltage shift indicating a stable TFT backplane. Significant uniformity improvements were made with novel TFT structure to give uniform AMOLED display. The deposition time for mc-Si TFTs was significantly reduced by using a thin mc-Si layer. Mc-Si TFT backplanes using conventional PECVD equipment offers significant cost advantages over other competing laser and non-laser polysilicon TFT technologies for AMOLEDs.

Stability Enhanced Flexible Liquid Crystal Display Based on a Micro-Structure

We demonstrate the stability-enhanced novel flexible liquid crystal display (LCD) mode by using the micro-structure of rigid columnar spacer array and a micro-contact printing (µCP) assembling method. Specially designed multi-column structure induces self-collected structure of adhesion material which resulted in the good adhesion properties of device to an external deformation as well as enhanced mechanical stability of electro-optic characteristics for flexible display application. Moreover, suggested method can easily inherit most advantages of conventional LCD technology such as low driving scheme, established process and LC mode selection freedom within a simple fabrication procedure. This novel technique can be highly applicable for realizing practical flexible display with enhanced mechanical stability and high performance.

38.4L: Late‐News Paper: A New Vertical Alignment Mode for TFT‐LCDs

A simple and cost-effective vertical alignment mode, named Smart Viewing Angle(SVA) mode, for active-matrix (AM) LCDs was developed where all the domain dividers are fabricated only on the TFT substrate side. The crucial component is the director control electrode (DCE) under the openings of the pixel electrode. The DCE maintains higher voltage than that of the pixel electrode via additional TFTs, which distorts the electric field in such a way that stable domain division is accomplished. Compared to the conventional VA modes where the additional process is required, SVA mode can achieve the wide viewing angle without any additional processes.

49.1: Fabrication of 23” PVA LCD Panel by Laser Ablation Process of ITO

We fabricated the world first 23” PVA LCD panel of which transparent electrode (ITO) was patterned by “laser ablation process”. Generally photo process is used to pattern the transparent electrode. To simplify this photo process we tried to develop laser ablation process to pattern the ITO. Current photo process is composed of 6 steps such as Coating the Photoresist, Baking, Exposure, Development, Etching, and Stripping. But we succeeded in simplifying this process by the laser ablation process. From this experiment, we could identify the possibility of laser ablation process which can be used on the patterning process of transparent electrodes.