Verfahren zur Herstellung photographischer Bilder

1,256,393. Increasing the sensitivity of photographic silver bromide emulsions. AGFA-GEVAERT A.G. April 30, 1969 [May 6, 1968], No.21930/69. Heading G2C. A process for the production of photographic images by exposure and development of photographic materials which contain at least one silver bromide emulsion layer comprises developing the exposed material in effective contact with a 1,4-thiazane of the general formula:- in which R is a hydrogen atom or an alkyl group containing up to 5 carbon atoms and R1 represents (1) a hydrogen atom, (2) a linear or branched alkyl group containing up to 12 carbonatoms which may be substituted with phenyl, OH, cyano, carboxyl, esterified carboxyl or alkoxy, (3) an aryl group, (4) an acyl group, (5) a carbamoyl group which may be substituted on the amide group with alkyl, aralkyl or aryl or (6) an amino group, which may be substituted with alkyl, aryl, acyl or carbamoyl, the carbamoyl group being optionally alkylated or phenylated. The acyl group (4) is preferably derived from an aliphatic carboxylic acid having up to 5 carbons. The aryl group (3) is preferably a substituted or unsubstituted phenyl group. The silver bromide emulsion may contain up to 10 mole % of silver iodide. R is preferably H or methyl. Many examples of these compounds are listed. The compound may be present in the developing solution or in the material. 3 mg to 20 g of the compound per mole of silver bromide are preferably present in the emulsion. These silver halide emulsions have increased general sensitivity without concomitant increase in fog level.