The Coloration of a Benzospiran Compound due to the Successive Exposures to Electrons and Ultraviolet Rays

Abstract

When a photochromic benzospiran compound (1, 3, 3-trimethylindolino-6'-nitrobenzopyrylspiran: [ A ]) in poly (vinyl chloride) (PVC) matrix was bombarded with an electron beam of medium energy (15 kV), 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 I 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.