GB714561A - Improvements in sensitized photographic emulsions - Google Patents

Abstract

714,561. Supersensitized photographic emulsions. KODAK, Ltd. Nov. 17,1952 [Nov. 17, 1951], No. 28894/52. Class 98(2) Photographic silver halide emulsions are supersensitized with a combination of (a) a hemicarbocyanine base having the formula wherein R 2 represents an alkyl group, R 3 represents an aryl group, L represents a methine group (any of which may be substituted or unsubstituted) and Z 2 completes a nucleus of the beta-naphthathiazole series, and (b) a 2:2'-carbocyanine dye or a 9-alkylthia 2-carbocyanine dye or a meso substituted carbocyanine dye which latter has the formula wherein R and R 1 represent alkyl groups, D represents an alkyl or aryl group (any of which may be substituted or unsubstituted), Z and Z, each completes a nucleus of the benzthiazole, benzselenazole or beta-naphthathiazole series and X represents an anion. In the above formulae. R, R 1 , R 2 and D may each be an alkyl group of the formula wherein n is an integer from 1 to 4 and D may also be phenyl, o- or p-chlorophenyl or o-, m- or p-tolyl. L may have the formula =CR 4 wherein R 4 is methyl or ethyl, R 3 may be phenyl, o- or pchlorophenyl or an alkoxy-phenyl group and X may be bromide, iodide, chloride, methyl sulphate, ethyl sulphate, benzene sulphonate, p-toluenesulphonate, perchlorate or thiocyanate. Many examples of both dyes and bases, and of suitable combinations, are given, but only those combinations which produce a supersensitizing effect as determined by the tests given in Specifications 498,031, 498,289, 498,290 and 498,291 are of use in the invention. Both dye and base may be used in concentrations of 0.05 to 0,25g per mole of silver halide in the emulsion and the ratio of dye to base may vary from 5:1 to 1:5 by weight. The emulsions may be coated onto a support of glass, cellulose nitrate, cellulose acetate, polyvinyl acetal resin, paper or metal. The invention is particularly useful for gelatino-silver-halide developing-out emulsions. Specifications 344,409, 394,692, [both in Group IV]; 525,365, 533,425, 561,172, 585,666, [Group IV], 599,636, 635,841 and 676,164 also are referred to.