Nonsilver Photography

For convenience, the applications of tetrazolium salts to nonsilver photography will be divided into two sections: photochemical systems and photoconductive systems.

Photochemical systems are similar to the silver halide-based systems in that light causes a stoichiometric chemical change (a latent image) which can be amplified (developed) to an image either by heat or by activation by another chemical. Inorganic photosensitive compounds such as ferric, vanadic, or molybdic ions, palladium oxalate and various cobaltic complexes,608 — 610 and organic photosensitive compounds such as quinones,611-615 benzimidazoles,616 and aziridines6i7 are amenable to development using tetrazolium salts.

The principles of photoconductive systems are outlined in many texts, notably Mort and Pai’s text,618 and several chapters of Gregory’s text on organic colorants are also useful.619 Tetrazolium salts are used in electrophotography primarily as toners and charge control agents lead­ing to high-quality images both in black and white and color reproduc — tions.620 — 624

In addition, the photosensitivity of some tetrazolium salts can be used as the basis of an imaging system.625 They have been used with electro-

chromic electrodes in display devices,626 629 with electropolymerizable

resist systems, and with photoelectrolytic cells.630 — 633

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