High pretilt four-domain twisted nematic liquid crystal display by microrubbing: Process, characterization, and optical simulation

A microrubbing (μ-rubbing) technique was utilized to create four-domain alignment in a liquid crystal display sample. A small metallic sphere under sufficient load was used to directly rub a homeotropic polyimide alignment layer to create a large surface pretilt angle. We demonstrate a 47-μm linewidth and a variable pretilt angle with respect to the substrate plane for different loads. The homeotropic polyimide surface was μ rubbed in such a way that neighboring alignment regions are rubbed in opposite directions. liquid crystal cells were constructed with two μ-rubbed substrates where the rubbing directions are orthogonal to each other. With this cell configuration we obtained four domains consisting of two left-handed and two right-handed twisted nematic subpixels. We report on the electro-optic performance properties, viewing angle characteristics, the relationship between pretilt angle versus load, and thermal aging study of the four-domain liquid crystal cell. The optical simulations of the liquid crystal director orientation, viewing angle characteristics, and the contrast ratio of the four domains are also presented. The experimental results are in agreement with the simulation results.