Development of a Multimode Liquid-Crystal Light Value.

Three major issues in the development of a multimode liquid-crystal light valve were addressed in this phase of the continuing research; Liquid-crystal electro-optical effect, Light valve stability and lifetime, and Photoconductor performance. We concluded that the lifetime and stability of the tilted perpendicular alignment cannot be sufficiently improved to produce a practical and useful device for a high-brightness, large screen display system. The problem is that the molecular pre-tilt angle is unstable in the presence of a high-brightness projection light. The tilted perpendicular alignment therefore was abandoned in favor of the 45 deg. twisted nematic alignment using the hybrid field effect mode (HFE mode), by HRL. With respect to color symbology and multimode operation; however, the HFE mode was less suitable, and considerable experimentation with the goal of optimization was performed and is reported here. A phenomenological study was made on liquid-crystal cells operated in the HFE mode. The objectives were to optimize and to determine the range and intensity of colors that can be obtained with an HFE light valve and to acquire a working knowledge of the effect of certain cell parameters (e.g., twist angle, thickness, and the match or mismatch of the polarization plane with front surface alignment).