Mechanically and light induced anchoring of liquid crystal on polyimide film

The interplay between the effects of mechanical rubbing and UV light induced deimidization on polyimide films has been studied. Exposure to depolarized UV light of rubbing PI film was found to suppress effective anchoring energy. Polarized light led to the alteration of the orientational distribution of PI molecules obtained by rubbing i.e to the change of both anchoring energy and easy axis direction. A simple model based on the selective UV light absorption with consequent deimidization of PI molecules describes the UV-initiated processes on the rubbed polyimide layers but contradicts the experimental data obtained for non-rubbed layers. The results obtained show that UV exposure can be effectively used to control anchoring parameters.