title: Annihilation of photochemical reactivity of photo-alignment layer.
abstract: The gas-polymer and liquid-polymer interfacial reactions of photosensitive polyimide can annihilate photo-reactive carbon-carbon double bonds, which remain after photo-alignment process. The annihilation processes dramatically affect voltage holding ratio and reorientation of photo-active functional groups. Photochemical dimerizations were identified using UV-visible and FT-IR spectroscopy. Polyimide films containing cinnamate groups were irradiated by linear polarized ultra violet (LPUV) light. Schadt et al. claims that the photo-alignment results from the anisotropy depletion of the cinnamate side chains as a consequence of the (2+2) cycloaddition reactions. The photo-aligned polyimide induces the orientation of nematic liquid crystals perpendicular to the polarization axis. However, the un-reacted photo-sensitive functional groups generate problems such as image sticking and reduced contrast ratio. Voltage holding ratio and photo-fading observed from photo-alignment layer can be dramatically improved by annihilation process of remnant photoreactive groups.
authors.affiliation: Department of Chemical Engineering, Hong-ik University, Seoul, 121-791, Korea.
authors.forename: S H
authors.initials: SH
authors.lastname: Hong
authors.forename: Y J
authors.initials: YJ
authors.lastname: Hwang
authors.forename: S G
authors.initials: SG
authors.lastname: Lee
authors.forename: D M
authors.initials: DM
authors.lastname: Shin