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.1 The photoaligned polyimide induces the orientation of nematic liquid crystals perpendicular to the polarization axis.1,2 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.
Document Type: Research Article
Publication date: September 1, 2008
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