IMAGE TONERS FOR SILVER HALIDE PHOTOGRAPHIC FILMS

摘要

A black-and-white, negative-acting, silver halide emulsion is described which gives improved image tone when used in a photographic element. The toning agents are based on dithio-substituted compounds having general structures (I) and (II) where R1 and R2, independently, are selected from the group consisting of alkyl, aryl and heterocyclic groups, or R1 and R2 together complete a ring; n and m are integers from 1 to 5; Y is a hydrogen; R3 is a hydrogen or alkyl group; and X is selected from the group consisting of O, S, N-OH and N-N(R)2, where R is a hydrogen or alkyl group.