Investigation of tilt angle dependence of gradient photosensitive polymeric material on exposure dose

Abstract

The optimum composition of material and its treatment conditions for tilt angle gradient formation required for creation of liquid crystal (LC) lens is determined. The distinctive feature of the material is the two-step process of alignment layer surface for variable tilt angle: standard rubbing step that defines the azimuthal direction of LC alignment, and the exposure step that forms pretilt angle profile of the alignment layer. The subject is a copolymer, characterized by the percentage of its components. We used antiparallel LC cells to determine optimum сopolymer composition. The cells have alignment layers from polymer under investigation rubbed and exposed to different doses. It is established that before exposure materials have the property of vertical LC alignment, and after exposure planar LC alignment. Material without defects of both planar and vertical alignment suitable for LC lens application - VA-30 comprises 10% photosensitive styrene-based monomer; 30% methacrylate monomer, causing vertical LC alignment and 60% methacrylate monomer, causing planar LC alignment.