GB498290A - Improvements in sensitised photographic emulsions - Google Patents

Abstract

498,290. Sensitizing dyestuffs for photographic emulsions. KODAK, Ltd. (Eastman Kodak Co.) March 25, 1937, No. 25051/38. Divided. out of 498,031. Drawings to Specification. [Class 98 (ii)] A gelatino-silver halide emulsion contains a pseudocyanine and a carbocyanine containing oxygen, sulphur or selenium, the combination yielding a supersensitizing effect. Examples of pseudocyanines to be used include the 2 : 2<1>- cyanine dyes, the thia-2<1>-cyanine dyes, the selena-2<1>-cyanine dyes, the benzthia-2<1>-cyanine dyes, the oxazolo-2<1>-cyanine dyes, the thiazolo- 2<1>-cyanine dyes containing substituted alkyl or phenyl groups, the alkyl being preferably of one to four carbon atoms. The nuclei may contain simple substituents alkyl, chloro, alkoxy or amino groups. The examples of the carbocyanines include the 8-alkylthiacarbocyanines, the 8-alkylselenacarbocyanines, the 8-alkyldibenzthiacarbocyanines, the 8-alkylthiaselenacarbocyanines, the 8-alkylselenabenzthiacarbocyanines, the 8-alkylbenzthiacarbocyanines, the oxathiazolocarbocyanines, the 41- alkyloxathiazolocarbocyanines, the 41-phenyloxathiazolocarbocyanines, the 41 - alkyloxaselenazolocarbocyanines and the 4<1>-phenyloxaselenazolo-carbocyanines. Numerous results of experiments determining the speed figures of dyes and combinations thereof are included in the Specification. The specified test for indicating supersensitization comprises comparing the sensitivity of the individual dyes with that of a mixture of the dyes. The combination may comprise more than two of the dyes. The supersensitizing combination is either applied to the emulsion before coating or applied by bathing the coated emulsion. U.S.A. Specifications 1,969,446 and 2,005,411 are referred to. The Provisional Specification also contains subject-matter which is described in Specifications 408,273, [Group IV], 498,031, 498,289, and 498,291.