Recently, we clarified that a single-polarizer reflective TN-LCD with a two-sheet retardation film produces an achromatic image with high luminance and a high contrast ratio, even if the on-voltage of the TFT-LCD is reduced to 2V. The power consumption can thus be decreased to one-sixth to one-seventh of that of a conventional reflective TFT-LCD with a 5V on-state, while maintaining a high-quality image. In this paper, we numerically analyze the influence of the twist angle, the dispersion of Δn, and material parameters of an LC on the relationship between the electro-optical properties and the on-voltage to obtain the optimum twist angle and dispersion of Δn, and the lower limit of the on-voltage. We found that the optimum twist angle is about 50°, and that a small dispersion of Δn is preferable for obtaining a high-quality image. In addition, we clarified that the on-voltage can be lowered from 2V while maintaining a high-quality image when the LC material parameters are optimized.
We have proposed and fabricated a thin ferroelectric liquid crystal device with large cone angle (45°), and studied its molecular switching behaviors. In the device, the molecular alignment direction is stabilized in rubbing direction of two polyimide alignment layers coated on substrates, by enhancing the influence of the anchoring effect of the alignment layers, where the rubbing strength is heightened and the liquid crystal thickness (1 μm) is small. The molecular alignment change from the rubbing direction occurs according to applied voltage, resulting in producing a V-shape electrooptic effect with continuous light modulation. As the alignment defects could be reduced by decreasing liquid crystal thickness, the device obtained a high contrast ratio of 250. We also considered a model of molecular alignment structure through measurement and simulation results of viewing-angle properties of the device.
It is revealed that electroluminescence (EL) spectra of bluish-green luminescent Ce^<3+> centers can be stabilized by Rb doping for SrS:Ce thin film EL devices prepared by an electron-beam evaporation method. It is also foud that Rb doping results in reduction of current spike of EL devices indicating suppression of Ce^<3+>-V_<Sr> complex center formation. For the transparent SrS:Ce, Rb device even without a postdeposition annealing, the bluish-green EL corresponding the Commission Internationale de l'Eclairage (CIE) color coordinate of (0.18, 0.34) was obtained with a luminance of 193 cd/m^2 under 1 kHz pulse drive at 40 V above the threshold voltage. The luminance of the SrS:Ce, Rb EL device was improved to be 206 cd/m^2 by annealing at 650℃ while keeping almost the same CIE color coordinate.
In order to reduce the deflection power of horizontal coil, development of rectangular type deflection yoke is proceeded. On the other hand, the characteristics spreads of this type deflection yoke grow worse. We quantitatively analyzed the real cause of these spreads by several experiments. As the results, improved coil and ferrite core system is confirmed to be effective to keep power saving and minimize the spreads at the same time.