Holographic Image Storage and Display Based on Photoinduced Change in Refractive Index of Polymer Liquid Crystals with photochromic Moieties

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Photochemical phase transition of liquid crystals (LCs) can be induced by a photochemical reaction of photochromic molecules. For example, when an azobenzene structure is introduced to LC molecules as the photosensitive moiety, the photochemical LC-to-isotropic phase transition takes place isothermally by the transcis photoisomerization of the azobenzene. We have developed holographic materials by means of polymer azobenzene LCs. On irradiation of a couple of coherent light beams, the real-time hologram was created by periodic induction of photochemical phase transition in polymer azobenzene LCs. Observation of the grating structure with a polarizing microscope confirmed that the isotropic phase was arranged with a spatial resolution of < 1μm which corresponds to a storage capability of > 400 Mbits/cmィイD22ィエD2. Under the optimal experimental condition, 28% of diffraction efficiency and 60 ms of writing time were achieved. When 2-dimensional or 3-dimensional images were stored in the polymer azobenzene LC films, clear reconstructed images were observed with high contrast and high resolution. We thus can expect that a high-density 3-dimensional image storage is possible with the polymer azobenzene LCs.