Photochromic material, photochromic thin film, clay thin film, and their

Abstract

In a first form, photochromic material has anionic photochromic molecules and anionic polar molecules adsorbed between layers of anion-adsorptive inorganic layer-structured crystals. In a second form, photochromic material has neutral photochromic molecules and non-polar molecules adsorbed between layers of anion-adsorptive inorganic layer-structured crystals. The photochromic molecules are of anionic or neutral spiropyran compounds and the inorganic crystals are of hydrotalcite compounds. These photochromic materials in which anionic or neutral photochromic molecules remain thermally stable find application as optical recording material. In a third form, a photochromic thin film is available comprising a pyrolyrically decomposed thin film of anion-adsorptive inorganic layer-structured crystals having anionic photochromic molecules and non-polar molecules adsorbed thereto. In a fourth form, a clay thin film is prepared by forming a thin film from an aqueous dispersion containing 0.1-5% by weight of a hydrotalcite group intercalation compound, drying the film, optionally heat treating the film for excluding a guest if any, and causing functional molecules such as photochromic molecules to be adsorbed between layers of the film.