Photographic silver halide emulsion prodn. - using rhodium salt and hydroquinone or amino phenol cpd. gives high contrast and stability

摘要

In the prodn. of the emulsions a Rh salt (I) is added to give the reqd. high contrast before the end of the first sensitisation stage in the prodn. of an AgBrCl or AgIBrCl emulsion with min. 30 mole % AgCl and max. 5-mole % AgI. A cpd. of the formula HO-A-OH (II) or HO-A-B (III) (in which A is a divalent aromatic gp. B is an amino gp.) or a cpd. which forms an oxidn.-redn. system with a cpd. of this type and can form the cpd. corresp. to the formula (II) or (III) is also added in an amt. of 10-7 to 10-1, pref. 1 x 10-5 to 3 x 10-2 mole/mole AgX, after freeing from salt. The emulsions are developed with a developer soln., which can be a black-and-white or colour developer, including a lith-type developer.