Photographische Halogensilberemulsionen mit erhoehter Empfindlichkeit

1,172,679. Development of photographic silver halide materials. AGFA-GEVAERT A.G. Dec.22, 1967 [Dec.27, 1966], No.58336/67. Heading G2C. A photographic light-sensitive silver halide material is exposed and then developed in the presence of a chemical sensitizer of the formula: in which R and R1 are each alkyl of up to 18 carbons, aralkyl or R and R1 together with the nitrogen atom form a 5, 6 or 7 membered ring, X is oxygen or sulphur, Y is a direct bond or methylene, R11 is hydrogen, hydroxy, esterified hydroxy or the group -CH 2 -S-Z where Z is acyl, aminomethyl, alkyl, cycloalkyl, aralkyl or aryl, and A is an anion. The sensitizer may be present in the emulsion, which may be a black-and-white or a colour emulsion and may also contain polyalkylene oxide sensitizers of various types including condensation products of spirocyclic pentaerythritol -di-phosphoric acid halides and polyethylene glycols, gold rhodanide and 4-hydroxy-6-methyl-1:3:3α; 7- tetrazaindene. The sensitizer may be present in the developer which may be a colour developer. When such a colour developer is used to develop a multi-layer colour material having an upper bluesensitive yellow-forming layer, a middle greensensitive magenta-forming layer and a lower redsensitive cyan-forming layer, the sensitivity of the red-sensitive layer is increased most, that of the green-sensitive layer less and that of the blue-sensitive layer least of all.