Reaction mechanisms in thermally developed photographic systems based on silver carboxylate

The chemistry of a thermally developed photographic system based on silver carboxylate is investigated both in the model system and in the film sample . The reaction path is found to consist of the disintegration of the silver carboxylate crystal structure under thermal development (step 1), the form ation of silver ion carriers which can diffuse in the molten media (step 2) , and the reduction reactions of silver ion to metallic silver by the reduc ing agent (step 3). In the first reaction step, XRD patterns and FT-IR spec tra show that phthalic acid receives silver ion from crystalline silver beh enate and becomes di-silver-phthalate. In the second reaction step, the com plexes of phthalazine and silver ion are identified as the silver ion carri ers in molten media by C-13-NMR, density functional calculations of C-13-NM R chemical shift, and TOF-SIMS. The diffusion coefficients of silver ion ca rriers are measured by pulsed field gradient H-1-NMR at the development tem perature. In the final step, the reduction of silver ion by the bisphenol-t ype reducing agent is analyzed by the identification of the reaction produc ts. It is found that this reducing agent has eight equivalent reducing powe r. An overall reaction mechanism for thermally developed photographic syste ms based on silver carboxylate is proposed.