Electrically aligned photo-polymer films for liquid crystal alignment

Abstract

The photo and electric field alignment of thin film of polyvinylcinnamate (PVCN) is shown to be considerably enhanced by using a combination of both methods. ITO-coated glass substrates were covered with a PVCN film using spin or dip coating and then heated above the glass transition temperature of PVCN. The alignment was induced by applying an electric field and stabilized by [2+2] cycloaddition of the polymer using a linearly polarized UV light. The anisotropy of the aligned polymer films was checked by measuring linear birefringence. Without crosslinking, the anisotropy of the electrically aligned films is vary weak. Crosslinked PVCN films using polarized UV light in the absence of any external fields lead to a better anisotropy than the aligned film by an electric field. The anisotropy is however increased substantially when the aligned PVCN films were crosslinked in the presence of a field.