The liquid crystal orientation on a poly͑vinyl cinnamate͒ or poly͑vinyl 4-methoxy-cinnamate͒ coated solid substrate exposed to linearly polarized UV light has been studied. The angular distribution of the polymer side chains and the photoreaction products was derived as a function of exposure time using a simple assumption about the probability for crosslinking of two side chains. The liquid crystal was assumed to be weakly anchored to the surface but have a degree of order and orientation determined from those of the polymer side chains. The polar and the azimuthal surface coefficients were estimated as a function of exposure time using the Landau-de Gennes theory and the behavior of a twist cell with polymer plates was studied for the values of the calculated surface coefficients. ͓S1063-651X͑97͒06802-5͔
The mechanism of liquid crystal pretilt angle generation on photoreactive polymer films doubly exposed to linearly polarized ultraviolet ͑uv͒ light has been investigated. The first exposure for time 1 is normal to the surface, and the film is subsequently irradiated for time 2 with obliquely incident uv light with a plane of polarization rotated by 90°with respect to that of the first uv light. The state of the polymer film after two exposures was characterized with a tensor order parameter, which then served as a boundary condition for the surface state of the nematic liquid crystal. The bulk liquid crystal behavior was investigated using Landau-de Gennes theory extended to include the possibility for weak surface interactions linear in the tensor order parameter. The pretilt angle was calculated as a function of both 1 and 2 , and as a function of the second uv light angle of incidence. The calculated behavior of the pretilt angle was found to be in qualitative agreement with experimental observations. Conclusions about the strength of the anchoring have also been made.
The electro-optic properties of a liquid-crystal display associated with a homeotropic to multidomainlike transition for a liquid crystal with a positive dielectric anisotropy have been investigated. The cell plates are prepared in such a way that, in the absence of an electric field, the liquid-crystal alignment is homeotropic. an electric field created by interdigitated electrodes on both substrates causes a director deformation of a multidomain type. The display shows wide viewing angle, excellent color characteristics, and a fast response time. The molecular director configuration, together with the electro-optic characteristics of the device, are discussed in this letter.
The angular polarization behavior, polarization efficiency, and brightness enhancement capabilities of reflective CLC‐based broadband polarizers have been studied. New methods for compensating the angular dependence of spectral characteristics for incident angles of up to 70 degrees are reported.
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