Yasuharu Tanaka

Pretilt-angle control of liquid-crystal alignment by using projections on substrate surfaces for dual-domain TN-LCD

— It was found that the value of the pretilt angle of liquid-crystal alignment achieved by a rubbing technique increases when small projections are present on the substrate surface. A dual-domain TN-LCD with very small dc offset voltage across the LC layer was realized by utilizing triangular-shaped projections.

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.

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.

Display performance improvement in a TFD‐LCD with reduced image‐sticking

image-sticking in a TFD (thin-film diode)-LCD (liquid crystal display) was examined. The DC offset voltage difference between ON-state and OFF-state is shown to cause image-sticking. It cannot be reduced by external DC offset compensation, which removes flicker. However, the DC offset voltage differences between ON-state and OFF-state are changed according to bias ratio. Therefore, the image-sticking can be reduced to less than 1%, both by bias ratio optimization and by its compensation according to temperature changes.<<ETX>>