INVESTIGATIONS OF THE REACTIONS INVOLVED IN FORMATION OF THE LIGHT-SENSITIVE PHASES IN THERMALLY DEVELOPED PHOTOMATERIALS

We have carried out electrochemical, sensitometric, and electron micro scope investigations of the reactions of the photosensitive phase of a thermally developable photomaterial. We have found that formation of microcrystals of silver bromide by metathetical reaction of silver ste arate with bromide in aqueous solution leads to precipitation of silve r bromide as a separate phase, accompanied by dissolution of silver st earate microcrystals. The size of the AgBr microcrystals increases wit h increasing concentration of the brominating agent, but does not exce ed 0.07 mu m. Latent image centers formed by the AgBr microcrystals ar e capable of catalyzing thermal development if the microcrystals have been formed in the presence of the carboxylate. The process of thermal amplification of the latent image centers may, however, be achieved o n AgBr crystals having no physical contact with silver stearate. We pr opose that thermal development of latent image centers on AgBr crystal s proceeds by diffusion of silver stearate-derived ''droplets'' to the development centers. Fog formation, on the other hand, nucleates inde pendently of the AgBr microcrystals.