The Anchoring Mechanism,Measurement And Application Of Nematic Liquid Crystal On Substrate

The anchoring of nematic liquid crystal (NLC) on substrate has an important effect on the display performance of liquid crystal displays. In this thesis, the anchoring mechanisms of both plane substrate and grating substrate were researched through the elastic theory of liquid crystal, the application of the optical waveguided technique in determining the distribution of director of liquid crystal and the anchoring energy of grating substrate was introduced, and the display characteristics of liquid crystal cell with grating substrate were investigated using the anchoring energy formula of grating substrate.The anchoring energy of plane substrate was theoretically studied applying the variation theory in which the flexoelectric polarization and the surface polarization were considered. The effective anchoring energy formula under an applied voltage was obtained. Dependences of the effective anchrong energy strength and the anchoring easy direction of two substrates in hybrid alignment nematic (HAN) cell on the applied voltage were given by numerical calculation from which the influence of two polarizations on the anchoring of two substrates was determined.Based on the interaction potential between NLC molecules and the molecules on the grating substrate and the increased elastic strain energy induced by liquid crystal, the anchoring properties of grating substrate were investigated. The effective anchoring energy formula was obtained and the variations of the effective anchrong energy strength and the anchoring easy direction with the geometry parameter of grating substrate were calculated numerically. Through the formula a grating substrate can be equivalent to a plane substrate. The rigorous solution of the anchoring on grating substrate was researched by means of two-dimentional finite-difference iterative method and the effective anchoring energy formula of grating substrate, meanwhile, the effect of the geometry of grating substrate on the director of liquid crystal was analyzed.The anchoring of NLC on grating substrate was measured by the experimental method. The optical waveguided technique, the theoretical analysis on the waveguided modes and the experimental process of the full leaky waveguided mode were introduced in detail. From the comparison between the theoretical curves and the experimental curves, the director profile in liquid crystal cell was determined, and then the effective anchoring energy formula might be validated. The liquid crystal cell with grating substrate was theoretically anayzed applying the anchoring energy formula of grating substrate. The distribution of director, the electro-optical characteristic curve, the variation curve of threshold voltage and the viewing angle-contrast ratio curve were obtained by numerical simulation. Through analyzing the influence of the geometry of grating substrate on these curves, the design configuration of grating substrate to realize the optimum display performance of liquid crystal cell with grating substrate was put forward.