Ultraviolet-light induced liquid-crystal alignment on polyimide films

Bond-breaking and oxidation occur during broadband ultraviolet light (UV li ght) illumination of the polyimide film in the air according to spectroscop ic analysis. Surface tension and polarity are increased based on the measur ements of contact angles. The liquid-crystal (LC) pretilt angles of the rub bed polyimide films are reduced by both unpolarized and polarized UV light illumination. Both the LC alignment and pretilt angle are generated on unru bbed polyimide films through the photoalignment process. The mechanism of p hotoalignment of LC is discussed.