GB974303A - Improvements in or relating to photographic silver halide emulsions - Google Patents

Abstract

974, 303. Stabilizing photographic silver halide emulsions. KODAK Ltd. Jan. 20, 1961 [Jan. 25, 1960], No. 2365/61. Heading G2C. A light sensitive silver halide emulsion which is chemically sensitized with a labile sulphur compound, a gold sensitizer, and a reduction sensitizer is stabilized by incorporating in the emulsion before, during or after the chemical sensitization, preferablye before the reduction sensitization, an aryl aldehyde having a substituent in the 3- and/or 4- position with respect to the position of the aldehyde group, or mucochloric or mucobromic acid or a water-soluble salt thereof. Suitable substituents in the aryl aldehyde compound are hydroxyl, halogen, alkyl or alkoxyl. Examples of suitable compounds are p-hydroxybenzaldehyde, m-hydroxybenzaldehyde and vanillin. Examples of water-soluble salts of mucochloric and mucobromic acid are the sodium, potassium,pyridinium,triethanolammonium and morpholinium salts thereof. Reduction sensitizer, which are defined as compounds having a sufficiently strong reduction action to reduce silver halide to metallic silver or to nucleate silver halide, preferably comprise stannous chloride, spermine, sodium formaldehyde sulphoxylate or a compound according to any of the following general formulae:- where R, R1 and R2 each represents a hydrogen atom, an alkyl group or an aryl group and M represents a water-solubilizing cation such as hydrogen, sodium, potassium, ammonium and triethanolammonium. where R3 represents an alkylene group containing from 2 to 4 carbon atoms and n represents a positive integer from 1 to 5. Also suitable are their water-soluble salts of non-desensitizing acids. III (R4)d SiH4-d or their hydrolysis products:- IIIa (R4)d SiOH4-d where R4 represents a hydrogen atom, a halogen atom, an alkyl group containing from 1 to 30 carbon atoms, an aryl group containing from 6 to 10 carbon atoms, an aryloxy group containing from 6 to 10 carbon atoms, a siloxy group or combinations thereof and d represents a positive integer from 1 to 3. The sulphur and gold sensitizers are defined and exemplified in the Specification. Specifications 649,545, 753,489, 789,823 and U.S.A. Specification 2,694,637 are referred to.