Shoichi Hirota

High-resolution full-color LCD driven by OTFTs using novel passivation film

A full-color twisted-nematic type liquid crystal display (TN-LCD) of 1.4-in diagonal size driven by organic thin-film transistors (TFTs) has been fabricated. This TN-LCD has 80/spl times/80/spl times/3 (RGB) pixel arrays addressed by pentacene TFTs with a channel width of 50 /spl mu/m. The contact resistance between the pentacene film and the source/drain electrodes has been reduced by selecting the exposure condition of the photoresist in patterning the electrodes. In addition, a solution-processed passivation film with a novel structure, consisting of photosensitive polyvinylalcohol and organosiloxane glass resin, has been developed to protect the TFTs against degradation induced by integration with TN-LCD devices. Consequently, it has been confirmed that the organic-TFT-driven TN-LCD fabricated in this paper is capable of displaying full-color moving images at a resolution of 80 pixels per inch.

57.1: Novel Pixel Design for a Transflective IPS-LCD with an In-Cell Retarder

We have successfully developed 2.4″QVGA transflective IPS-LCDs which maintains excellent transmissive performance and higher reflectance. We have an in-cell retarder patterned only in the reflective region. And we devised the pixel design so that the reflectance became higher. We have realized transflective LCDs with sufficient outdoor readability and wide viewing angle. Furthermore, we reduced thickness of the LCD panel at the same time.

High-mobility solution-processed organic thin-film transistor array for active-matrix color liquid-crystal displays

Abstract— A solution-processed organic thin-film-transistor array to drive a 5-in.-diagonal liquid-crystal display has been fabricated, where semiconductor films, a gate dielectric film, and passivation films have all been formed using solution processes. A field-effect mobility of 1.6 cm2/V-sec, which is among the highest for solution-processed organic thin-film transistors ever reported, was obtained. This result is due to semiconductor material with large-grain-sized pentacene crystals formed from a solution and adoption of three-layered passivation films that minimize the performance degradation of organic thin-film transistors.

P-231L: Late-News Poster: A Wide Viewing Angle Transflective IPS LCD Applying New Optical Design

Viewing angle performance of transflective LCDs, affected by many optical parameters such as Nz of retardation films and azimuth of slow axis, is improved when the optical parameters obey a simple rule. A new optical design is deduced from the rule, and applied for transflective IPS-LCD with a single gap structure and a twisted liquid crystal layer. A viewing angle performance comparable to transmissive IPS LCDs is realized in transflective IPS-LCD.

57.4L: Late-News Paper: Transflective LCD Combining Transmissive IPS and Reflective In-Cell Retarder ECB

In-cell retarder technology enables two kinds of display modes with different features to be realized in the pixels of transflective LCDs. Using this concept, we have developed a prototype 2.2″ QVGA transflective LCD that combines transmissive IPS for wide viewing angle performance and reflective in-cell retarder ECB for high reflectance.

Printable organic TFT technologies for FPD applications

In this paper, we introduce our recent results on organic thin-film transistor (TFT) technologies; self-aligned self-assembly process and a high-resolution color active-matrix LCD panel driven by organic TFT. First, a novel process for fabricating alignment-free, printable, organic thin-film transistors is presented. This process exploits a self-assembly phenomenon in which soluble nanomaterials such as metal nanoparticles and organic molecules are self-assembled into a device structure. Solution-processed source and drain electrodes were self-aligned to a gate electrode by using a hydrophobic self-assembled monolayer optically patterned onto the gate electrode with a back-substrate exposure technique. An organic semiconductor film deposited on the patterned SAM was selectively ordered and substantially self-aligned to the gate electrode. A field-effect mobility of 0.15 cm2/Vs and on/off current ratio of 105 were experimentally demonstrated when pentacene molecules were used as the semiconductor and silver nanoparticles were used as electrode materials. Second, a full-color twisted-nematic type liquid crystal display (TN-LCD) of 1.4-inch diagonal size driven by organic TFT has been fabricated. This TN-LCD has 80 x 80 x 3 (RGB) pixel arrays addressed by pentacene TFT with a channel width of 50 μm. The contact resistance between the pentacene film and the source/drain electrodes has been reduced by steepening the side slope of the electrodes. In addition, a solution-processed passivation film with a novel structure, consisting of organic and inorganic stacked layers, has been developed to protect the TFT against degradation induced by integration with TN-LCD devices. Consequently, the organic-TFT-driven TN-LCD is capable of displaying full-color moving images at a resolution of 80 pixels per inch.

A silicon-chip-based light valve with reflective twisted-nematic mode for high-definition projectors

— Crystalline-silicon-chip-based reflective light valves are suitable for realizing high definition and bright liquid-crystal projectors. We have developed an XGA (1025 × 769 pixels) silicon-chip-based light valve with a diagonal display area of 2.54 cm (1 in.). The reflective twisted-nematic mode was examined by using the Jones matrix method as a display mode, and the normally white reflective twisted-nematic mode was selected. This mode is suitable for a narrow cell gap, and a fast response time can be expected. In addition, the driving voltage of this mode is low and has good chromaticity with small retardation. The cell gap of the light valve is 2 μm. The cell gap support is made using spacer posts formed on the silicon chip with a photodefinable resin. The response time is 12 msec, including both rise and fall times. The contrast ratio is more than 1000 at 5 Vrms.

Enhancement of Viewing Performance of New Transflective In-Plane Switching Liquid Crystal Displays Using In-Cell Retarder(s)

High-viewing-performance transflective in-plane switching (IPS) liquid crystal displays (LCDs) with in-cell retarders have been developed. Transflective LCDs have pixels with transmissive and reflective display portions; the transmissive display portion is designed to have the same structure as the transmissive IPS-LCDs, and the reflective display portion is formed by patterning the in-cell retarder. The latter is designed to give a normally close mode characteristic, which has a brightness–voltage (B–V) curve similar to that of the former. The reflective display portions, which work as quarter-wave plates at dark states, can be classified into five structures according to the number of in-cell retarder(s) and the stacking order of the liquid crystal layer. In this study, on the basis of the five possible structures, the viewing performances of the transflective IPS-LCDs are investigated by simulation, and suitable solutions are also discussed.

Normally white reflective twisted nematic mode for silicon-chip-based light valves

Crystalline silicon-chip-based reflective light valves are suitable for realizing high definition and bright liquid crystal projectors. We have developed an XGA silicon-chip- based light valve with a diagonal display area of 1 inch. A normally white reflective twisted nematic mode is selected for the valve. An optimum condition of the mode is analytically solved by the Jones matrix method. This mode is suitable for a narrow cell gap and a fast response time can be expected. This mode also has a stable contrast ratio even with temperature and/or cell gap fluctuation. In addition, the driving voltage of this mode is low and it has good chromaticity with small retardation. The cell gap of the light valve is 2 micrometers . The cell gap support is made using spacer posts formed on the silicon chip with a photo- definable resin. The response time is 12 ms including both rise and fall times. The contrast ratio is more than 400 at 5 Vrms.

63.4L: Late News Paper: High Mobility Solution-Processed Organic Thin-Film Transistor Array for Active-Matrix Color Liquid Crystal Displays

We have fabricated a solution-processed 240 × 960 organic thin-film transistor array to drive a liquid crystal display, where the semiconductor, gate dielectric and passivation films have been all formed using solution processes. A field effect mobility of 1.6 cm2/Vs obtained is the highest value for solution-processed TFTs ever reported.