Director Orientation Measurement of Nematic Liquid Crystal Using Velocity Change of Shear Horizontal Wave

The nematic liquid crystal director orientation in the vicinity of a glass substrate is evaluated in relation to the acoustic phase delay change of the shear horizontal (SH) wave propagation in a cell structure. The evaluated director angle of a nematic liquid crystal 4-cyano-4'-pentylbiphenyl (5CB) as a function of applied voltage is independent of temperature in the nematic phase. The evaluated director angle is less than 75 deg under sufficient applied voltage and depends on the modes whose dependence is related to the penetration depth of the SH wave in the liquid crystal layer. The time response of the director motion is observable by the SH wave propagation. The present method using SH wave propagation in a liquid crystal cell is promising for evaluating the director angle in the vicinity of the substrate surface.