Reversible UV image recording on a photochromic side chain liquid crystalline polymer

Photochromism and photoinduced optical anisotropy have been studied for a c hiral comb-like Liquid crystalline copolymer containing azobenzene chromoph ores in its side chains. In a smectic glass phase of the polymer, upon irra diation by UV light, long living cis- isomers are observed. Spin coated fil ms, irradiated by linearly polarized light manifest a photo-induced anisotr opy, related to a strong stable dichroism, which is due to an enrichment an d depletion of the chosen angular direction, correspondingly, with trans- a nd cis-isomers of azobenzene chromophores. These films are shown to be a no vel medium for image recording, sensitive to W light. In particular, a holo graphic grating may be recorded on top of a hidden UV image by interfering beams of visible Ar-laser light. Therefore, a stable holographic pattern of an image recorded by incoherent UV Light is produced. It can be erased and recorded again.