Anisotropic reflectivity of rubbed polyimide liquid crystal alignment layer

The surface optical anisotropy of rubbed polyimide films has been detected using reflection anisotropy spectroscopy. The amplitude of the reflection anisotropy signals increases with the rubbing strength. Rubbing also causes changes in pretilt angle of liquid crystal molecules which are in contact with the rubbed polyimide. An increase in rubbing strength results in an increase in the pretilt angel. The pretilt of the liquid crystal molecules was found to linearly correlate with the amplitude of the RA signals.