Diffusion-Transfer Imaging Systems

Coordination chemistry can play a central role in diffusion transfer imaging chemistries, and reactions of coordination compounds control the diffusion of image-providing compounds in several image transfer systems. Of course, silver halide diffusion transfer has already been discussed in which a silver halide solvent enables the diffusion of undeveloped silver halide to a receiver, where it is developed into an image. 

Several other imaging systems based on Com/developer amplification are known, including systems with various diffusion transfer imaging chemistries. The principles are the same as those outlined here. Basically, most imaging chemistries useful with silver halide systems can be transformed into a low-silver or (sometimes) non-silver system with a suitable developer/Com complex redox combination for amplification on imagewise catalytic nuclei. 

Na[AuClJ, per mole of silver haHde. Coordination compounds are used as emulsion stabilizers, developers, and are formed with the weU-known thiosulfate fixers. Silver haHde diffusion transfer processes and silver image stabilization also make use of coordination phenomena. A number of copper and chromium azo dyes have found use in diffusion transfer systems developed by Polaroid (see Color photography, instant). Coordination compounds are also important in a number of commercial photothermography and electrophotography (qv) appHcations as weU as in the classic iron cyano blueprint images, a number of chromium systems, etc (32). 

Instant images, formation of, 19 278-279 Instant imaging processes, black-and-white, 19 279-282 Instant photography, 19 273-329 applications for, 19 322 black-and-white diffusion transfer reversal processes, 19 283 digital/instant film imaging systems, 19 321... 

In another system, a non-diffusible compound reacts with undeveloped silver ions to liberate a diffusible dye, producing a positive transferred image.141 Again, thiosulfate-containing developers are used. In this system, the silver ions catalyze the ring-opening hydrolysis of a thiazolidine (73), shown in equation (1). 

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