PURPOSE: To obtain a photochromic cemented glass capable of being used for a long period by adding a heat stabilizer when a polyvinyl butyral is formed into a sheet with a specified polyglycol as the plasticizer.
CONSTITUTION: A photochromic intermediate film is interposed between at least two sheets of glass to constitute a photochromic cemented glass. The laminate of a layer contg. a spiro-oxazine compd. and a polyvinyl butyral resin sheet layer using a glycolic plasticizer shown by formulas I,...V is used as the intermediate film. In the formulas, the sum of n per one molecule is controlled to 2-30, and R and R' are hydrogen atom or alkyl groups. When the polyvinyl butyral resin is formed into a sheet, an antioxidant or a heat stabilizer such as a hindered-amine compd. is used. Consequently, an unfavorable reaction product is nol, generated in the coloration reaction, and hence the cemented glass is not deteriorated by the photoirradiation for many hours.
MAEDA SHUICHI
MITSUHASHI KAZUO
MITSUBISHI CHEM IND