GB1305773A - - Google Patents

Abstract

1305773 Sensitized photographic silver halide emulsions EASTMAN KODAK CO 21 April 1970 [22 April 1969] 19043/70 Heading G2C A sulphur and selenium sensitized photographic silver halide emulsion of which the silver halide contains at least 10 mole per cent silver chloride and not more than 10 mole percent silver iodide, the remainder being silver bromide, contains a colour coupler. The sulphur and selenium sensitization may be effected simultaneously. The silver halide grains may be chemically sensitized after having reached their final size and shape. The colour coupler may be incorporated in the emulsion after chemical sensitization of the grains. Chemical sensitization may be effected with a mixture of sodium thiosulphate and dimethylselenourea. The selenium sensitizer may be generated in situ from a non-labile selenium compound (i.e. one which does not yield a silver selenide that is insoluble in water at 20‹C upon addition of aqueous silver nitrate solution). The sulphur sensitizer and the labile or non-labile selenium compound may be added to the emulsion as a solution in a water-immisable solvent. The combination of sulphur and selenium sensitization and the presence of the coupler provides a synergistic increase in speed without adversely affecting the colour development characteristics of the coupler.