MECHANISMS OF DEVELOPMENT OF PHOTOTHERMOGRAPHIC MEDIA

We have carried out an arrested development study on model thermally d eveloped photographic materials (TDPM) based on silver carboxylates. F rom both TEM and x-ray diffraction analysis of the media at various st ages of development, we infer that (1) during initiation of developmen t small, spheroidal silver(0) particles form; (2) over the course of t he development reaction, the number of silver(0) spheroids increases, but not their average size; (3) this process requires secondary nuclea tion of the silver(0) phase-forming reaction by an as-yet unestablishe d mechanism; and (4) above some threshold concentration, whose establi shment corresponds to the onset of the continuation stage of developme nt, these spheroids aggregate to form the light-absorbing particles co mprising the TDPM image. Development kinetics of full-soap and half-so ap systems were studied experimentally and by computer simulation to c onfirm the intermediacy of coordination complexes of silver ion and th e role of carboxylic acid as the reaction product responsible for posi tive feedback in the development reaction. Our inferences are consiste nt with the Klosterboer-Rutledge model of development, but also imply that features of the recently proposed Usanov model are relevant as we ll.