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It is found that liquid crystal materials such as 4−n‐octyl‐4′‐cyanobiphenyl (8CB) exhibit a reversible color change induced by an applied electric current when a small amount of electrolyte is dissolved into them. Such a coloration occurs in the liquid crystalline phase as well as in the isotropic phase. Their optical transmission spectra, and dependences of electrolyte concentration and applied voltage on the coloration, are measured in the isotropic phase. The changes in optical transmission and liquid crystal texture during a coloration and bleaching sequence are measured in the nematic, smectic, and cholesteric phases. A mechanism of coloration is discussed and an application of such an electrochromic liquid crystal cell to a laser beam writing is proposed.It is found that liquid crystal materials such as 4−n‐octyl‐4′‐cyanobiphenyl (8CB) exhibit a reversible color change induced by an applied electric current when a small amount of electrolyte is dissolved into them. Such a coloration occurs in the liquid crystalline phase as well as in the isotropic phase. Their optical transmission spectra, and dependences of electrolyte concentration and applied voltage on the coloration, are measured in the isotropic phase. The changes in optical transmission and liquid crystal texture during a coloration and bleaching sequence are measured in the nematic, smectic, and cholesteric phases. A mechanism of coloration is discussed and an application of such an electrochromic liquid crystal cell to a laser beam writing is proposed.

Irradiation by ultraviolet or visible light is found to induce a reversible change in the phase transition temperatures of smectic liquid crystals doped with an isomeric compound such as azobenzene. Such irradiation is also found to bring about a reversible change in the threshold voltage for electrohydrodynamic instability and in the electro-optical and thermo-optical characteristics by a photochemical trans (cis)-cis(trans) isomerization. Some experimental results are described for two types of cell; one includes a small amount of electrolyte and the other includes a cholesteric liquid crystal, in addition to the isomeric compound. Some novel imaging devices based on the effects are also proposed, in which an ultraviolet image is converted to a visual image with high contrast and a long-term memory.