Yoshifumi Sekiguchi

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.

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.

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.

Diffraction mechanism of a light-diffusing film with an alternate-polymer-layer structure

A diffraction mechanism, and an optical model to reflect that mechanism, for a light-diffusing film with an alternate-polymer-layer structure was proposed and validated. According to this model, the film forms an angular distribution of light intensity that is almost constant in a certain scattering-angle (cutoff angle) range and drastically decreases outside that range; that is, the profile is similar to a trapezoid. Although the trapezoid intensity distribution (TID) is a fundamental distribution of the film, the mechanism to form the TID has not previously been clarified. A key mechanism is that the refractive-index distribution of the layer structure is expressed as stacked phase gratings, some of which should diffract zeroth-order light to higher orders strongly, and the repetition of this multiple diffraction spreads light over the whole cutoff angle range, thereby generating the TID. To verify the proposed mechanism, intensity distributions were calculated by using the proposed model. The calculation results indicate that the proposed model reproduces the TID.

Simple ray-tracing model for a rough surface of an ink layer including internal scattering particles printed on a light guide plate.

For simulating light guide lighting systems, we have developed a ray-tracing model for an ink layer extracting light from a light guide. The model consists of the volume and the rough surface scattering calculated on the basis of Mie theory and the facet model, respectively. The model of an ink layer was required to conserve energy for analyzing how much light loss occurs in each component in the lighting system. Though a single-scattering rough surface model with a shadowing/masking function successfully describes the scattering distribution, shadowing light violates the energy conservation law because of a lack of multiple scattering. We developed the rough surface ray-tracing model (RSRT model), which includes the multiple scattering instead of the shadowing/masking effect. We investigated the applicability of the RSRT model for an ink layer by comparing the RSRT model with recent physical and facet models. Finally, we compared the calculated and measured scattering distributions of an ink layer, applied the developed ink layer model to the lighting system, and confirmed the developed model to be valid.

Simple ray-tracing model for a rough surface including multiple scattering effects

To simulate lighting systems, we developed a rough surface ray-tracing (RSRT) model on the basis of the facet model. The model needs to conserve energy to analyze how much light is lost in each component in the lighting system. Though a single scattering rough surface model with a shadowing/masking function successfully describes the scattering distribution, masking output light violates the energy conservation law because it lacks multiple scattering. We thus developed an advanced RSRT (A-RSRT) model satisfying the energy conservation law that includes a shadowing/masking effect as a consequence of multiple scattering. To determine the accuracy, we set up a real shape (RS) model that outputs rigorous simulation results, although this RS model was impractical. The comparisons between the calculated results of the A-RSRT and RS models revealed that the A-RSRT model satisfied the energy conservation law and reproduced the scattering distribution precisely.

P-9: Flicker Reduction Driving Method for 8-Color Partial Mode TFT-LCDs Used in Cellular Phones

We have developed driving technology to reduce the power consumption of TFT-LCDs which display information using 8 colors on a partial screen area in the standby mode of cellular phones. We propose that the LCD be driven at low frame frequency and that more unnecessary circuits be stopped intermittently when driving the LCD. We reduce flicker by making the optical response waveform for a frame like a simple pulse and by having the same waveform in the positive and negative frames.