Modeling of photoinduced optical anisotropy and anchoring energy of polyimide exposed to linearly polarized deep UV light

Abstract

A kinetic model of the mechanism for photodecomposition alignment of liquid crystal (LC) by polyimide exposed to linearly polarized deep UV (LPDUV) light is described. A three-dimensional model is applied to anisotropic bulk characteristics, such as retardation of the LPDUV-exposed polyimide, as a function of the UV dosage, and a two-dimensional model is applied to anisotropic surface characteristics, such as the anchoring energy of the interface between the liquid crystal and polyimide. The experimental data are well fitted by these models. The maximum values of the order parameter of the LC and anchoring energy are obtained at the same dosage of LPDUV, and show that the maximum surface anisotropy is obtained with polyimide exposed to 1 J/cm2 LPDUV.