Directional behaviour of liquid crystals on homogeneous polyimide surfaces induced by polarised ultraviolet exposure and rubbing

We studied liquid crystal (LCs) alignment effects on homogeneous polyimide (PI) surfaces induced by polarised UV (PUV) exposure and rubbing in different directions. We found that the LC orientation is not affected by PUV exposure times of less than 90 min after rubbing, and that PUV exposure times over 90 min after rubbing resulted in LC orientations that were more closely aligned with the direction of PUV exposure than the direction of rubbing. Short-term PUV exposure affects the variation of the pretilt angle of the PI and LC. In addition, as PUV exposure time increases, it can convert the LC alignment direction from the rubbing direction to the PUV direction.