Photographische Halogensilberemulsion mit erhoehter Empfindlichkeit

1,244,878. Photographic chemically sensitized silver halide emulsions. AGFA-GEVAERT A.G. Dec.23, 1968 [Dec.22, 1967], No.61177/68. Heading G2C. A light-sensitive silver halide emulsion contains a chemical sensitizer of the following formula, which increases the sensitivity of the emulsion: wherein Z represents an oxygen atom or the group NRII ; RI represents a saturated or olefinically unsaturated aliphatic group containing up to 18 carbon atoms; X is a methylene group or a dialkylsilyl group; and RII represents an alkyl group containing up to 6 carbon atoms, which sensitizer contains at least one dialkylsilyl group. RI may also be substituted with one or more photographically acceptable substituents, e.g. with hydroxyl, amino, alkylamino, dialkylamino, cyano, alkylthio, alkoxy, trialkylsilyl or trialkylsilyloxy groups. Many examples of such sensitizers are given. The emulsion may also contain a polyalkylene oxide sensitizer of the formula RO-[CH 2 CH 2 O] n -R wherein R is H, alkyl, acyl or aryl and n is an integer of between 8 and 200 or of the formula:- wherein R 1 is H or an alkylene oxide chain with 3 to 100 alkylene oxide units; m is an integer of 3 to 100 and y is an integer of 1 to 10, or an 'onium compound of the formula: The silicon-containing chemical sensitizers cause little or no fogging. Certain synergistic combinations of sensitizers are illustrated in Table 2 of the Specification.