Hidefumi Yoshida

3.1: MVA LCD for Notebook or Mobile PCs with High Transmittance, High Contrast Ratio, and Wide Angle Viewing

We have developed a new MVA-LCD with high transmittance comparable to a TN-LCD. We stacked a pair of quarter wave plates and stabilized the molecular alignment by dividing each pixel and arranging fine slits and nipple-shaped protrusions. The quality affordable for desk-top monitor is realized for mobile display.

23.1: Fast-Switching LCD with Multi-Domain Vertical Alignment Driven by an Oblique Electric Field

We have developed a novel fast-switching LCD with multidomain vertical alignment driven by an oblique electric field. The oblique electric field is applied between comb-shaped source electrodes and comb-shaped common electrodes on a TFT substrate and an ITO electrode on a CF substrate covering the entire display area. The ITO electrode is covered by a dielectric layer. The LCD has a wide viewing range (>160°), a high contrast ratio (>250:1) and fast response times even in black-and-white (13 ms (rise), 4 ms (decay)), and gray-scale (<17 ms) switching. The LCD has no problems with electrostatic charge, disclination, or slow gray-scale switching.

Inclined Homeotropic Alignment by Irradiation of Unpolarized UV Light

Inclined homeotropic alignment was realized by irradiation of unpolarized ultraviolet light on a polyimide film that originally exhibited homeotropic alignment. Unpolarized UV light was irradiated from an oblique direction (45-degree inclined angle) once. The liquid crystal cell with a pair of inclined homeotropic aligned substrates and nematic liquid crystal with negative dielectric anisotropy exhibits a high contrast ratio (over 1000) with a crossed Nicols configuration and a bright transmittance (same as a TN cell, around 35%).

Reflective display with photoconductive layer and bistable reflective cholesteric mixture

Abstract— A reflective display was developed using a bistable reflective cholesteric formulation. It was addressed by using a photoconductive layer. An image was written on the liquid-crystal layer by transmitting white light through a TFT-LCD or slide film. Because the cholesteric materials are bistable, the displayed image remains after the applied voltage is removed and even when irradiated with intense light.

Four-Domain Divided Inclined Vertical Alignment by Irradiation of Unpolarized Ultra Violet Light

A four-domain divided vertically-aligned liquid crystal panel (LCP) has been realized by irradiating unpolarized UV light on a vertical alignment layer through an optical mask. The liquid crystal (LC) with a negative dielectric anisotropy is filled. As the alignment has no disclination for the black state, the transmittance in the black state is the same as that with mono-domain vertically aligned LCPs, realizing a high contrast ratio of over 300. With a negative birefringence film, the fabricated LCP exhibits a wide viewing range. It has a contrast ratio of over 10 at any inclination angle of within 60° at any viewing azimuth and has almost no gray scale inversion.

Wide‐viewing‐angle full‐color TFT‐LCDs

— Conventional TFT TN-LCDs display full-color images only within a narrow vertical viewing angle. Viewed obliquely, the display reverses or brightens. We studied these problems by calculating the light propagation through TN cells and concluded that these reversal phenomena are unavoidable in TN-LCDs. To widen the viewing angle, we propose a film-laid double-twisted-nematic display (FDTN), consisting of a conventional TN panel, a light-compensation panel, and two retardation films stacked together. The problem of black images appearing purple is solved using a clockwise-twisted nematic panel as an optical compensator. The viewing angle of the FDTN-LCD is about 1.5 times that of the conventional positive TN-LCD. The contrast ratio normal to the panel exceeds 100.

Light Behavior Analysis of Twisted Nematic Liquid Crystal Display

We investigated the light behavior in a twisted nematic (TN) cell by plotting the polarization and liquid crystal director on a Poincare sphere. We calculated the polarization using Berremans 4×4 matrix method. We have clarified (1) the polarization of light propagating in a liquid crystal layer for oblique viewing in upper, lower, right, and left azimuth, (2) the reason for each oscillation and peak of transmittance–voltage characteristics at oblique viewing angles, (3) the reason for the difference between the viewing angle characteristics of e-mode and o-mode TN-LCDs, and the reason why e-mode and o-mode TN-LCDs have the same characteristic in some azimuth, (4) the reason why normally black mode does not have symmetrical viewing angle characteristic.

Vertically Aligned TFT-LCDs

Fujitsu has developed several types of vertically aligned TFT-LCD: with protrusion; with photo-alignment; and with comb-shaped electrodes. The protrusion-type TFT-LCD has the best balance of specifications and is in mass- production. It has a transmittance of 5% for a 15-inch XGA LCD, a response of 25 ms (τon + τoff), and a contrast ratio of over 400. The photo-aligned type gives highest transmittance (7.5%) with dual domains. The lamp for UV irradiation can be a tube type and non-polarized UV is possible. We think it is a good candidate for notebook-type applications. The comb-shaped electrode type has the fastest response of better than 17 ms for any gray-scale switching. We think it is a good candidate for video applications.

20.1: Dual‐domain Vertically Aligned TFT‐LCD Developed by Irradiation with Unpolarized UV Light from a Tube‐type Light Source

We have developed a dual-domain vertically aligned TFT-LCD by irradiation with unpolarized UV light from tube-type light source. We reduced disclination by fabricating protrusions and by optimizing the alignment material. The transmittance of a 15-inch diagonal TFT-LCD is twice that of IPS LCD, 1.5 times that of conventional MVA-LCD and 1.1 times that of TN-LCDs with Wide-View film.

Direct-view polymer-dispersed LCD with crossed Nicols and uniaxial film

— By adding a uniaxial retardation film and using a chlorinated LC mixture, the performance of polymer-dispersed LCDs with crossed Nicols (PDN-LCDs) was improved. A wide viewing angle of more than 60° (contrast ratio >5) for all azimuth directions was obtained. In the horizontal and vertical viewing azimuth, the contrast ratio was over 30 even at an inclination viewing angle of 60°.