Study on Molecular Orientation Effects in Polymer-Liquid Crystal Composite Systems

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Polymer-liquid crystal composite materials abbreviated by PDLC (polymer dispersed liquid crystals) are prepared using various kinds of UV-curable methacrylate prepolymer and nematic liquid crystals with a positive or a negative dielectric anisotropy. The PDLC cells can be switched electrically from a light scattering off state to a highly transparent on state. Memory effects, in which a transparency is preserved for a long time after a voltage is removed, are observed in PDLC cells with a reversed morphology. The memory states can easily created by the phase transitions from an isotropic to a nematic phase with application of an electric or a magnetic field. Their electrooptical and thermo-optical properties are studied.Morphologies of PDLC films are studied by scanning electron microscope photographs of their sections, and the dependence of polymerization and phase separation conditions on the morphology and electrooptical properties are measured and discussed. PDLC cells are prepared … More with various terms of UV irradiation, and the transmittance, capacitance and resistance are measured while the phase separation is advanced. The relationship between the term of UV irradiation and the electrooptical property can be clarified and the optimum condition to prepare them can be attained by monitoring the change of the resistance.A new type of optical device which transmits the incident light only in directions oblique to the normal of the cell in an off-state is demonstrated using both the positive-type and negative-type PDLC cells.Ad highly transparent memory-state was obtained with relatively low driving voltage. Thermal addressing and local erasure in the positive and negative modes were performed using a laser beam on the PDLC cell. A thermal image was also succesfully written by a thermall printer head onto a flexibele PDLC film.The possibility of application of the polymer-liquid crystaal composites to the new type of thermally addressed display device is discussed and demonstraated. Less