Masahito Ishikawa

Improvement of viewing angle characteristics in a twisted‐nematic liquid‐crystal display by using a cholesteric liquid‐crystal compensation layer

Viewing angle characteristics of a twisted nematic (TN) liquid‐crystal display (LCD) have been improved by inserting a planar aligned cholesteric liquid crystal compensating layer between the TN cell and a polarizer. Dependencies of the electro‐optical characteristics of the novel LCD on the retardation, ratio of thickness to the pitch (dc/p) and twist‐sense in the cholesteric layer are discussed. A thin‐film transistor addressed LCD with a wide viewing angle has been developed based on this novel cell construction and its display performance is reported.

Electro-optic behaviour of low molar mass felc's doped with liquid crystal polymers

Abstract In this paper we present data on the electro-optic switching tilt angle memorisation properties of polymer doped ferroelectric liquid crystalline mixtures. Side chain polysiloxane polymers at concentrations up to 11% w/w were added to the low molar mass mixtures ZLI-4237–000 and -100. The response times of the 11% w/w polymer/ZLI-4237–100 mixtures were identical to those of the neat ZLI-4237–000 mixture. The memory properties were studied using bipolar pulses before and after the samples were subjected to mechanical shock. The polymer containing mixtures retained their memory properties after mechanical deformation whereas the neat low molar mass mixtures did not.

Incorporation of input function into displays using LTPS TFT technology

— A new display in which an input function is incorporated has been developed by using LTPS TFT technology. A new circuit configuration that includes a lateral p-i-n diode with an in-pixel amplifier, an LTPS A/D converter on the periphery of the glass substrate and an external image-processing LSI is presented. The experimental results of two major applications of the image-capture function and touch-panel function are discussed.

Synthesis and Properties of Optically Active Phenoxypropionates Having Various Cores

Abstract Optically active phenoxypropionates having a variety of cores were synthesized and the effect of the different core structures on the spontaneous polarization (Ps) values was investigated. The results indicate that the core structure has a great influence on the Ps value and compound 3 in which a chiral group attached to the 5-phenyl side of the 2,5-diphenylpyrimidine core showed the largest Ps of 240 nC/cm2. The ability as a chiral dopant for ferroelectric liquid crystal (FLC) were also evaluated. It was found that compound 3 was the most interesting, because the doping of compound 3 induced large Ps and wide tilt angle and this FLC mixture showed short response time. Moreover, the Sc range of host liquid crystal mixture are slightly extended by doping of compound 3.

Psychophysical evaluation of viewing-angle characteristics of liquid-crystal displays

— The viewing-angle characteristics of liquid-crystal displays (LCDs) were evaluated using calculated psychophysical metrics related to luminance and color. The results were compared with the results obtained from subjective estimation. The results of psychophysical evaluations agreed better with subjective estimation in the bright state than in the dark state. In addition, it was found that subjective estimates of LCD quality are better correlated with changes in calculated psychophysical values with viewing angle than with the absolute values themselves. It was also found that the iso-curves for different hue angles are useful in evaluating the viewing-angle characteristics of LCDs.

Viewing-angle evaluation method for LCDs with gray-scale images

— A new evaluation method of viewing-angle characteristics for liquid-crystal displays (LCDs) with gray-scale images has been studied. In this method, reverse images, excessively dark images, and excessively bright images, which are a serious problem while displaying gray-scale images, are evaluated quantitatively along with the display contrast ratio. The viewing-angle characteristics of several types of LCDs are compared using this method.

Viewing-angle evaluation method of color shift for LCDs with gray-scale images

— The viewing-angle characteristics of LCDs with gray-scale images were evaluated using parameters related to color. The results were compared with the subjectively estimated results. It was found that iso-curves of the maximum value of the difference in hue angle are useful in evaluating the viewing-angle characteristics of LCDs.

Viewing-angle magnification in a TN-LCD with an ultra-super-twisted liquid-crystal compensator

— The viewing-angle characteristics of a TN-LCD were improved by inserting an ultra-super-twisted (UST) liquid-crystal compensating layer between the TN cell and one of the polarizers. The viewing-angle characteristics of the LCD could be controlled by changing the optical conditions of the UST layer, such as the retardation, the dUST/p value, and the twist sense. The improved viewing-angle characteristics were confirmed by a TFT-addressed LCD developed on the basis of this novel cell construction.

Reduction of reflectance in liquid-crystal displays

— Specular reflectances of TFT-LCDs with various polarizer conditions, black-matrix materials, and aperture ratios were measured. The measured results were compared with simulated results of reflectances from various parts of LCDs. In the case of LCDs having polarizers with flat surfaces, the simulated results agreed well with the experimental results, while in the case of LCDs having anti-glare polarizers, the results did not agree with the experimental results.

Quantitative comparison of LCD viewing-angle improvement brought about by various methods

— In this paper, we quantitatively compare the viewing-angle improvement of LCDs brought about by using various methods proposed by different researchers. We used the Iso-REC (iso-reverse image, excessively dark/bright image, and contrast ratio) method for this comparison. From this comparison, it was found that dual-domain LCDs and optically compensated birefringence (OCB) LCDs have preferable viewing-angle characteristics.