Tilt angle generation for nematic liquid crystal on blended homeotropic polyimide layer containing trifluoromethyl moieties

A decrease in tilt angle generation for a nematic liquid crystal (NLC) with negative dielectric anisotropy on a blended homeotropic polyimide (PI) surface containing trifluoromethyl moieties was investigated. The decrease in tilt angle (below 90°C) of NLC on the blended PI surface containing a homogeneous PI structure having a high tilt angle was measured, and the tilt angle of the polymer was found to decrease as the rubbing strength increased. However, the decreases in tilt angle (about 90°) of NLC on the blended PI homeotropic surface containing two kinds of homogeneous PI structure having a low tilt angle were not observed. The tilt angle of NLC generated was about 73° and the drop of tilt angle is attributable to the trifluoromethyl moiety attached to the lateral benzene ring in the backbone structure on the blended homeotropic PI surface. Therefore, the drop of the tilt angle of NLC to below 90° of NLC can be achieved using the blended homeotropic PI surface.