Studies Of Liquid Crystal Molecules Alignment And Polarized Texture Of LCD

The tropism control technology of liquid crystal molecules is very important in the production of LCD. It not only affects the response velocity of liquid crystal molecules, but also affects the display quality of LCD. At present, rubbing is still the main tropism control technology in LCD industry, but its surface topograph is not controllable. Grating tropism control technology can exactly control the surface topograph, such as depth and width of gratings by adjusting some parameters, such as light intensity and incidence angle. This is a method which induces liquid crystal molecules align uniformly by grating in tropism layer of LCD, and has good future.Surface relief grating is made on glass substrate as the tropism layer of LCD, and the tropism alignment of nematic liquid crystal molecules layer in different thickness is studied. The grating period is 700 nm, which includes groove line width with 400 nm and groove height with 160 nm. In addition, the surface topograph of this grating is different with normal grating. The groove line width is great than its peak width, and its shape is like a converted π . The influence of liquid crystal layer thickness to alignment of liquid crystal molecules is analyzed. When the thickness of the liquid crystal layer is about 8 μm, uniform texture is formed and the liquid crystal molecules align along the grooves of the gratings, the transmitted light intensity changes periodically as the gratings rotate 90°. Period grating is the main reason of liquid crystal uniform alignment.The influence of light radiation to the alignment of liquid crystal molecules is analyzed, and it directly results in the display performance descending of LCD. After light radiation, ultraviolet photos destroy molecule structure of liquid crystal and polyimide in tropism layer and this induce the uniformity of liquid crystal molecules becomes bad. With the accumulation of light radiation time, the transmission rate gradually descends. In response, its stripe polarized texture becomes black holes and the black holes become bigger and bigger. The existence of black stripes and black holes lost extinction is just the main reason of LCD display performance decline.