| abstract |
An object of the present invention is to provide a novel compound which is suitably usable as a photochromic material. n The compound of the present invention is a salt of a spiropyran compound and an acidic compound, the spiropyran compound being represented by the formula ##STR1## wherein R 1 means a C 1 to C 20 alkyl group, an aralkyl group, a hydroxyethyl group, an acryloxyethyl group or a methacryloxyethyl group, R 2 to R 7 each mean a hydrogen atom, a C 1 to C 6 alkyl group or the like, R 8 means a hydrogen atom, a vinyl group, a group --CH 2 OR 9 or a group --CH 2 OCOC(R 10 )═CH 2 (wherein R 9 means a hydrogen atom or a C 1 to C 4 alkyl group and R 10 means a hydrogen atom or a methyl group), and X means an oxygen atom or a sulfur atom. |