Patent GB-540451-A (GB)
Title: Improvements relating to photographic materials
IPC: G01F15/00
Filed: 1940-04-15
Abstract: 540,451. Photographic light-sensitive material ; colour photography. KODAK, Ltd, and DAVEY, E. P. April 15, 1940, No. 6780. [Class 98 (ii)] The tendency for a sensitizing dye present in a photographic emulsion of silver salt in a watersoluble binder such as gelatine to wander to a neighbouring light-sensitive photographic emulsion is reduced by dispersing a substantally waterinsoluble organic binder through the first emulsion preferably prior to bringing the emulsions into such a relative position that wandering of the dye is liable to occur. The emulsions may be mixed or applied successively to a support. The binder may be a natural or synthetic resin (such as whole, hard, soft, or hydrolysed soft shellac; colophony; " Glyptal (Registered Trade Mark) resins; gum mastic; and dammar, sandarach, copal, kauri, and coumarone resins; or a cellulose ester or ether (such as cellulose acetate). A solution of a resin in an organic solvent may be added to a liquid photographic emulsion, and the dye is incorporated in the emulsion, before, simultaneously with, or after addition of the resin. The dye and the resin may be dissolved in a common solvent. The resin may be dispersed in an aqueous gelatine solution, in which the dye may also be incorporated, and the dispersion added to the emulsion. 10 to 35 grams of the binder may be added for each gram molecule of silver halide present. The binder may also be incorporated in a non-dye sensitized emulsion when it is required to prevent wandering of dye from a sensitized emulsion thereto. In incorporating sensitizing dyes in emulsions, the quantity of solvent for the dye should be kept low. If the solvent for the water-insoluble organic binder dissolves the dye, the quantity of this should also be kept low. A solution of a resin in an organic solvent may be added to an aqueous solution, and the solvent distilled from the resulting dispersion before addition to the emulsion. A similar procedure may be adopted with the dye solution. Where the emulsions are mixed, coating and drying should be effected as quickly as possible. With printing papers, the resin tends to give a matte appearance to the print, which may be removed by hotglazing after processing. In an example, to 7¢ litres of a high-contrast silver chloride emulsion is added with stirring a solution obtained by mixing ethyl alcoholic solutions of 5-[(2-ethyl- 1(2) - benzoxazolylidene) - ethylidene] - 3 - ethyl- 1-phenyl-2-thiohydantoin and of soft lac resin. The resultant emulsion is mixed with a soft silver bromide emulsion (by weight) 70:30, and the mixture coated on a paper support. A high-contrast image is obtained with a yellow printing light, and a low-contrast image with a blue light. In a second example, the quantities of alcohol used as solvent for the resin and the dye are reduced, and an ethyl alcohol solution of soft lac resin is added to the bromide emulsion before mixing. diethyloxacarbocyanine iodide and 2:31-diethyl- 3:4-benzoxathiazolinocarbocyanine iodide (greensensitizers) ; 3-ethyl-5-(2-ethyl-1(2)-benzselenazylidene)-butylidene-1-phenyl-2-thiohydantoin (redsensitizer) and 1-methyl-1<SP>1</SP>-ethyl-2:2<SP>1</SP>-azacyanine iodide (blue-sensitizer). A colour photographic paper, film, or plate may be prepared by applying successively to a support and drying three photographic emulsions adapted to record the blue, green, and red portions of the image respectively, each emulsion having had a substantially water-insoluble organic binder dispersed through it prior to applying it to the support. Specifications 450,958, 494,088, 505,834, 524,154, 524,554, 524,555 and 540,525 are referred to.