Patent GB-547060-A (GB)
Title: Improvements in or relating to the production and use of light-sensitive silver halide photographic emulsions
IPC: G03C1/10
Filed: 1940-05-13
Abstract: 547,060. Photographic light-sensitive material. POTTER, R. S., and HAGAMAN, R. S. May 13, 1940, No. 8601. [Class 98 (ii)] A multi-contrast silver halide emulsion is produced by the incorporation in a silver halide emulsion, in a quantity substantially less than that necessary to produce maximum colour sensitivity in the spectral region to which the dye imparts sensitivity, of a sensitizing dye which is such that the resulting emulsion, when coated on a support and used as a printing material, gives widely different contrasts according to the colour of the printing light, the ratio of the maximum gamma value to the minimum gamma value of the prints obtainable from the emulsion is 5:4 or greater. The amount of dye employed may be not more than half the quantity necessary to effect maximum colour sensitization, and the dye may be added to the emulsion at a temperature equal to or below the usual coating temperature, in the form of a very dilute solution in a good solvent. The emulsion should preferably contain grains of widely differing composition or character or both. Where the emulsion is washed, the dye may be added before or after the washing operation, or the washed emulsion shreds may be bathed in a very dilute aqueous alcoholic solution of the dye. Non-wandering dyes are preferably used. Dyes specified are (2-methyldihydrobenzthiazolylidene) -1 : 31- ethylidene- (1<SP>1</SP> - ethyloxindole) ; 2 : 21- diethyl- 7 : 71- o phenylenethiacarbocyanine-ptoluenesulphonate ; 2 :3<SP>1</SP>-diethyl-5 :bthia-1 : 4 z-6e<SP>1</SP>-n quinazocyanine iodide ; 2:11-diethyl-3:4-benzoxapseudocyanine iodide ; 2:11-diethyl-thiapseudocyanine iodide ; 1:1<SP>1</SP>-diethyl-9:9<SP>1</SP>-ethylene-2:2<SP>1</SP>-carbocyanine bromide ; 2:2<SP>1</SP>-dimethyl-3:4:3<SP>1</SP>:4<SP>1</SP>-dibenz- 7:7<SP>1</SP>-ethylene-thiacarbocyanine-p-toluenesulphonate; 2:2<SP>1</SP>-diethyl-5:6:5<SP>1</SP>:6<SP>1</SP>-dibenz-7:7<SP>1</SP>-ethylenethiacarbocyanine-p-toluenesulphonate,; 1:1<SP>1</SP>-diethyl-3:3:3<SP>1</SP>:3<SP>1</SP>- tetramethylindocarbocyanine iodide ; 2:21-diethyl- 4:5:4<SP>1</SP>:5<SP>1</SP>-tetramethyloxacarbocyanine iodide; 2:1<SP>1</SP>- diethyl-4-methylselenopseudocyanine iodide ; 2:2<SP>1</SP>- diethyl-8-methylthiacarbocyanine bromide; 2:2<SP>1</SP>:8- triethyl-4:4<SP>1</SP>-dichlorothiacarbocyanine chloride ; and 1-p-dimethylaminostyrylbenzthiazole. In examples (1) to 270 ccs. of a gelatino-silver iodobromide highcontrast emulsion containing 6 grams of silver per 100 ccs., about 3 per cent of the total silver being present as silver iodide, cooled to 80‹ F., is added 0.6 ccs. of a 0.1 per cent ethyl alcoholic solution of 1:1<SP>1</SP>-diethylpseudocyanine iodide, and the emulsion is set, washed, digested, and coated. On exposure with blue light (3700-5100 A) and standard development an image with a gamma value of 6.7 is obtained. On exposure with yellow light (5100 A and all wavelengths above) and similarly developing, the image has a gamma value of 1.9. By using varying proportions of blue and yellow light, intermediate gamma values are obtained. Optimum sensitization would in this case require an addition of about 3 ccs. of dye solution. (2) To portions of a similar emulsion cooled to 80‹ F., various quantities of the dye (1:3:3:5- tetramethylindolylidene)-2:4<SP>1</SP>-ethylidene-(1<SP>1</SP>-phenyl- 3<SP>1</SP>-methylpyrazole-5<SP>1</SP>-one) are added immediately before setting, and after washing, digesting, and coating, the resulting emulsion layers are exposed with blue and yellow lights and developed. A table of results is given, and it is shown that as the quantity of sensitizing dye added is made greater, the range of gamma values obtainable from the emulsion is made smaller. (3) To 300 ccs. of a medium-contrast gelatino-silver iodobromide emulsion containing 5.4 grams of silver per 100 ccs., 2.5 per cent of the total silver being present as silver iodide, cooled to 80‹ F., is added before setting 5 ccs. of a 0.05 per cent ethyl alcoholic solution of (1:3:3-trimethylindolylidene)-2:4<SP>1</SP>-ethylidene-(1<SP>1</SP>-m-tolyl-3<SP>1</SP>-methylpyrazole-5<SP>1</SP>-one). After washing, digesting, and coating, the emulsion is exposed to blue and yellow lights and developed under standard conditions. The image obtained by exposure with blue light had a gamma value of 2:2 and with yellow light of 1:1. By increasing the quantity of dye to 7 ccs., the image obtained by exposure with blue light had a gamma value of 2.45 and with yellow light of 1.7. Optimum sensitization requires 14 ccs. of dye. (4) To 300 cc. lots of the emulsion of (3) cooled to 80‹ F. are added before setting various quantities of a 0.1 per cent ethyl alcoholic solution of (1:3:3-trimethylindolylidene)-2:4<SP>1</SP>-ethylidene-(1<SP>1</SP>-phenyl-3<SP>1</SP>-methylpyrazole-5<SP>1</SP> - one), and after washing, digesting, and coating, the emulsion layers produced are tested as in (1). A table of results is given. Optimum sensitization requires 10 ccs. of dye. (5) The procedure of (4) is repeated, using (1:3:3-trimethylindolylidene)-2:41-ethylidene- (1<SP>1</SP>-p-ethoxyphenyl-3<SP>1</SP>-methylpyrazole-5<SP>1</SP>-one). A table of results is given. Optimum sensitization requires 10 ccs. of dye. (6) A shredded emulsion of the type used in (3) is bathed for 80 minutes in a 0.05 per cent ethyl alcoholic solution of the dye of (2). The dye solution is drained off, extra gelatine added, the shreds melted and digested, and the emulsion coated on a support. On testing as in (1), the gamma value of the image produced by exposure with blue light is 1.9 and with yellow light 1.0. Similar results are obtained with the dye 1:3:3-trimethylindole-2:2<SP>1</SP>-trimethine-6<SP>1</SP>-methylquinoline. (7) To 450 gram lots (containing about 8.1 grams of silver) of an acid gelatino-silver chlorobromide emulsion, in which the molecular ratio of silver bromide to silver chloride is 3:1, at 130‹ F. soon after emulsification, are added various quantities of a 0.025 per cent ethyl alcoholic solution of 2:2<SP>1</SP>-diethyl-5:5<SP>1</SP>-dimethyloxacarbocyanine iodide. After ripening at 130‹ F., setting, washing, remelting, digesting, and coating on paper supports, the emulsion layers are tested as in (1). A table of results is given. The emulsions give images of higher gamma value on exposure with yellow light. Optimum sensitization requires 24 ccs. of dye. (8) The procedure of (7) is repeated using 2:2<SP>1</SP>-diethyl-5:5<SP>1</SP>-dimethoxyoxacarbocyanine iodide. A table of results is given. The emulsions give images of higher gamma value on exposure with yellow light. Specifications 494,088 and 529,041 are referred to.