GB967768A - Improvements relating to the production of images - Google Patents

Abstract

967, 768. Photographic processes. E.I. DU PONT DE NEMOURS & CO. Sept. 6, 1962 [Sept. 12, 1961], No. 34220/62. Heading G2C. A process for the formation of an image comprises (a) exposing to image-forming radiation, containing radiation in a region of normal sensitivity of a silver. halide photographic emulsion or of extended sensitivity conferred by the presence of an optical sensitizing dye, a washed, light-sensitive colloid-silver halide emulsion layer having an average grain size of 0.1 to 10 microns and containing (i) 0.5 to 120 mole per cent per mole of silver halide of a water-soluble stannous salt, (ii) a sensitizing amount of an optical sensitizing cyanine, pseudocyanine, carbocyanine or merocyanine dye capable of extending the sensitivity of a silver bromide emulsion from the normal blue region to the green, red or infra-red region of the spectrum, and having added thereto (iii) at least one chloride, bromide or iodide of lithium, sodium, potassium, calcium, magnesium or ammonium in an amount sufficient to provide an excess of halide ions over that necessary initially to precipitate all the silver as silver-halide; (b) latensifying the exposed element by irradiating it for to 60 seconds with light radiation which comprises the region of greatest response in the region of extra sensitivity conferred on the silver halide emulsion by the dye; and (c) photodeveloping the latensified element by exposing it to actinic radiation of wavelengths between 3000 and 5000 A having an intensity less than the exposing radiation (a) for at least one second. The emulsion may also contain 0.1 to 4 mole per cent of plum bous nitrate. Apart from the dyes the emulsions are similar to those of Specification 877, 841. In examples the emulsions contain the following dyes: - 5, 5<SP>1</SP>-dimethyl-3, 31, 9-triethyl benzselenazole carbocyanine iodide; 3, 3<SP>1</SP>-diethyl-9-methyl benzothiazole carbocyanine p-toluene sulphonate and its corresponding 5, 5<SP>1</SP>-dibromo-compound; 5, 5<SP>1</SP>, 9- trimethyl-3, 3<SP>1</SP>-diethyl benzothiazole carbocyanine iodide; 5, 5<SP>1</SP>-diphenyl-9-methyl-3, 3<SP>1</SP>-diethyl benzoxazole carbocyanine iodide; 5-methyl-3, 1<SP>1</SP>-diethyl- 2, 2<SP>1</SP>-selenopseudocyanine iodide; 5, 5<SP>1</SP>-dimethyl-3, 3<SP>1</SP>-diethyl-9 ethyl or phenyl benzothiazole carbocyanine iodide; 3-ethyl-5-[1-ethyl-2(1)-benzoxazolidene-isopropylidene]-2-thio-2, 4-oxazoledione; and 3-n-butyl-5-(3-ethyl-3-thiazolidene ethylidene)- rhodanine. Specification 931,636 also is referred to.