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

Photochromism and photoinduced optical anisotropy have been studied for a chiral comb-like liquid crystalline copolymer containing azobenzene chromophores in its side chains. In a smectic glass phase of the polymer, upon irradiation by UV light, long living cis-isomers are observed. Spin coated films, irradiated by linearly polarized light manifest a photo-induced anisotropy, related to a strong stable dichroism, which is due to an enrichment and depletion of the chosen angular direction, correspondingly, with trans- and cis-isomers of azobenzene chromophores. These films are shown to be a novel medium for image recording, sensitive to UV light. In particular, a holographic 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.