The coloration of a benzospiran compound due to the successive exposures to electrons and ultraviolet rays

When a photochromic benzospriran compound (1,3,3-trimethylindolino-6'-nitrobenzopyrylspiran : [A] in poly(vinyl chloride) (PVC) matrix was bombarded with an electron beam of medium energy (15kV), only yellow species was formed. This is probably a product from a reaction between a metastable colored species [B] and a chlorinated component liberated from PVC. Formation of [C] increased by the exposure to UV ray after the electron bombardment. This may be due to a reaction between the residual chlorinated component and [B] formed by the post-irradiation. When the specimen was bombarded with an intesity of 10-6 C/cm2, the coloring reaction of [C] due to the post-irradiation followed a pseudo-first order kinetics in the initial stage, indicating that sufficient ammount of the residual component existed during the post-irradiation. This additional coloration of [C] was observed also in the air. This fact indicates that the formation of [C] is not affected by oxygen and that the liberated component is hydrogen chloride. Since the post-irradiation intensifies recorded image, this process may be applied to an electron-beam recording system. (auth.)