A Model of the Unidirectional Alignment Accompanying the Pretilt Angle of a Nematic Liquid Crystal (NLC), 5CB, Oriented on Rubbed Organic-Solvent-Soluble Polyimide Film

Abstract

We report a model of the unidirectional alignment accompanying the pretilt angle of a nematic liquid crystal (NLC), 5CB, oriented on rubbed organic-solvent-soluble polyimide (PI) film, which is useful for color active matrix liquid crystal displays. According to our computer calculation, the main chain of the PI molecule, which contains special moieties, forms a helicoidal structure. The model suggested in this paper for the NLC alignment claims that rubbing gives rise to the permanent stretching and deformation of the helicoidal structure that results in the NLC unidirectional alignment and pretilt angle, where the latter is attributed to the formation of asymmetric microscopic triangles.