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Abstract

The present invention relates to chemical compositions of synthetic dyes and a fabrication process for the photo-induced alignment of liquid crystals. The compositions and methods of the invention are applicable to lateral field driven LCDs such as the In-plane Switching mode. A method of alignment using a multiple wavelengths light source is disclosed. This is a non-contact technique to align liquid crystals so that the particulates and static charges generated by the rubbing process can be eliminated. A synthetic dye film is exposed to a linearly polarized or non-polarized light. Due to photoisomerization, conformational molecular change occurs, and the isomer orientation is no longer random but becomes anisotropic. This in turn gives rise to a homogeneous anisotropic orientation of the liquid crystal molecules. This liquid crystal orientation is in general not parallel to the isomer major molecular axis, and yet the relation can be deduced from the polarization vector and incidence angle of the illumination. The oblique incidence of the light exposure will favour a non-zero pretilt angle. The order parameter as a measure of this alignment effect is large for most of the synthetic dyes disclosed in this invention. The azimuthal anchoring energy associated with the synthetic dye can be many-fold lower than its polyimide counterpart, and therefore a sizeable reduction in the LCD drive-voltage is possible.

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First Claim