GB552368A - Improvements in light sensitive photographic materials - Google Patents

Abstract

552,368. Photographic materials. KODAK, Ltd. (Eastman Kodak Co.). June 27, 1941, No. 8149. [Class 98 (ii)] A photographic sensitive silver salt film, plate, or paper capable of giving a gradation depending upon the colour of the light used for exposure is produced by applying to the support in admixture two portions of unequal size of the same similar photographic emulsion, both portions being dye-sensitized to spectral ranges outside their natural sensitivity such that either can be exposed without substantially exposing the other. The smaller portion may be red-sensitized and the larger green-sensitized or vice versa.. A silver chloride, chloriodide, chlorobromide, chlorobromiodide, bromide, or bromiodide emulsion may be used. The smaller portion may be from 1/7 to 1/3 of the larger portion. The two portions may be prepared separately provided that they are substantially identical in composition. Both portions are preferably sensitized with an amount of dye less than that required to produce optimum sensitization. Dye-wandering may be prevented by the means referred to in Specifications 540,451, 540,464, 541,510, or 541,511, or non-wandering dyes may be used as described in Specification 532,098. Dye-wandering may also be reduced by digesting the emulsion after adding the sensitizing dye but before bringing into contact with the other portion. A further substance may be added to the dye-sensitized emulsion to give a supersensitizing effect. Sensitizing dyes may be selected from the thia-21-cyanine, benzthia-21-cyanine, selena-21-cyanine, 2:21-cyanine, thiazolo-2<SP>1</SP>-cyanine, dibenzythiacarbocyanine, 5:5<SP>1</SP>- dichlorothiacarbocyanine, 5-chlorothiacarbocyanine, 5-chlorothiaselenacarbocyanine, 5-chlorothiabenzthiacarbocyanine, 5:5<SP>1</SP>-dichloroselenacarbocyanine, 5-chloroselenacarbocyanine, 5-chloroselenathiacarbocyanine, 5-chloroselenabenzthiacarbocyanine, merocyanine (which may contain a longchain organic group), merocarbocyanine, and merodicarbocyanine classes. The emulsion binder may be gelatin, a resin, or a cellulose derivative. In an example, a silver-bromiodide emulsion is divided into two portions A and B, and portion (A) is sensitized with 2:21:dimethyl-8-ethyl-3:4: 3<SP>1</SP>:4<SP>1</SP>- dibenzthiacarbocyanine bromide and portion (B) with 2:11-diethyl-3:4-dibenzthiacarbocyanine bromide. The portions are held at 50‹ C. for 10 minutes before mixing. The material may be exposed with green and with red light. Three or more portions of emulsion may be used similarly. Specifications 498,031, 498,289, 498,290, 498,291, 514,159, 514,198 and 515,372 also are referred to.