Preferred Pre-tilt Direction of Liquid Crystal Molecules on Rubbed Polyimide Surfaces

Abstract

We systematically investigated the relationship between the preferred pretilt direction (PD) of the liquid crystal (LC) directors and the physical parameters of the rubbing-treated polyimide (PI) surfaces via contact angle measurements and scanning probe microscopy (SPM) techniques. Rubbing treatment could induce anisotropy and asymmetry in the contact angle and the surface roughness of the PI surfaces, which played important roles in determining the preferred PD of the LC molecules. According to our results, the preferred PD of the LC directors aligns along a direction with low contact angle and low surface roughness.