Feasibility study on twisted nematic liquid-crystal cell with two cross-embedded wire-grid polarizers as alignment and electrode for projection displays.
For this study, twisted nematic liquid crystals (TN-LCs) are sandwiched between two cross-embedded wire-grid polarizers (WGPs) as alignment and electrodes for projection displays. In the proposed device, the WGPs replace not only the sheet polarizers in a conventional TN-LC cell, but also the front and rear alignment layers and transparent electrodes. It is found that the structure of a WGP microgroove is suitable for alignment; however, the proposed TN-LC cell exhibits a multidomain phenomenon because there is no apparent pretilt angle on the two WGPs. The multidomain phenomenon can be solved by the annealing method and by blending chiral material with the TN-LC for twisting the LC in the same direction. In addition, the surface resistance of the aluminum WGP is two orders lower than the indium-tin-oxide glass substrates, so that it is suitable for electric conductivity and for use as a transparent electrode. Also, metallic WGPs exhibit a higher heat resistance characteristic than plastic sheet polarizers, making them robust. As a result, the threshold voltages, the saturation voltages, and the response time of the proposed TN-LC cell are almost identical to the conventional TN-LC cell. The contrast ratio of the LCD projector with the proposed TN-LC cell and the quarter-wave plate exhibit the best characteristics in comparisons with the other LCD projectors. Thus, the proposed TN-LC cell represents a simple and feasible solution for the next generation of high-brightness projection display devices.
Chen
Chin-Yu
CY
Department of Mechanical Engineering, National Cheng Kung University, Tainan, Taiwan.
Lo
Yu-Lung
YL