A method of controlling anchoring energy of surface interaction of liquid crystal photoaligning substances is considered to enhance the liquid crystal display performances. An important parameter of the dye's molecular structure that determines the ratio of polar and azimuthal anchoring energy is the ability to form dimers. The values of dimerization thermodynamic potentials have been found. The probability of the formation of dye molecules dimers is evaluated. The bonds conjugation transfer via intermolecular hydrogen bond is revealed, and anisotropy of polarizability of the hydrogen bond is evaluated. The effect of dimerization on polar and azimuthal anchoring energy of liquid crystalazo dye systemis shown.
To date, azo dyes are widely used for liquid crystal photoalignment in flat panel displays. The relation of dichroism of azo dyes with their orientation under intensive light wave field is considered. Values of a
truecos2φ¯ parameter, which characterizes orientation order of both molecules and dimers, were obtained as well as energy of their orientation process. Number of cooperatively oriented dye molecules was estimated. The angles distribution functions for different dimers were derived. Dipole electrical transition moments directed on angles close to 90° to the direction of maximal polarizability of dimers were revealed.
Theoretical description of the photoalignment process details is an urgent task to make the LC alignment more perfect and develop displays with new functions. In this paper we describe formation of photoaligning dye dimers and influence of their molecular structure on both polar W h and azimuthal W u anchoring energy.
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