Mobile ion induced electric field effect in polymer-stabilized vertical alignment liquid crystal display

Abstract

Mechanisms of radical polymerization on the surface of the alignment layer in polymer stabilized vertical alignment (PS-VA) liquid crystal display (LCD)are suggested. When DC voltage is applied between top and bottom electrode, it is observed that the liquid crystal molecules distort alignment directions, which deteriorate luminance uniformity during UV irradiation process. It is revealed that the liquid crystal movement is attributed to mobile ions, (K+, OH-), smearing out from the interface at the lower layer of the pixel electrode. The mobile ions are generated from the developer remains after color filter formation process. To minimize the influence of the mobile ions, the thickness of the insulating SiNx layer under the pixel electrode and the color filter is increased, which contribute to luminance reduction rate from 20% to less than 1%.