GB399151A - Improvements in or relating to photographic processes - Google Patents

Abstract

399,151. Photographic processes; colour photography. JOHNSON & CO. (PAPER), Ltd., A. H., 171, Queen Victoria Street, and MARTINEZ, M., 10, Adelphi Terrace, Adelphi, both in London. March 21, 1932, No. 8367. [Class 98 (ii).] In processes of colour photography wherein a coloured gelatin or like colloid layer is differentially hardened, in proportion to the silver content of an image in, under, over, or brought into contact with the layer, by treating the layer in the presence of the image with a bath of the kind used in the ozobrome process, the coloured layer is produced by colouring the colloid in aqueous solution with a dye which has been separated from an alcoholic solution in a fine state of subdivision and remains undissolved in the water in the colloid layer, and forming the layer therefrom. By this means the general hardening action of the dye on the colloid which occurs mainly when the dye is in aqueous solution is avoided. The layer may be produced by preparing a strong solution of a spirit-soluble dye in alcohol and adding to a gelatin solution. Alternatively a previously made suspension of a dye may be mixed with the gelatin solution. In an example an aqueous solution of indigo carmine is mixed with an aqueous alcoholic solution of auramine and the resulting suspension added to a gelatin solution. If a colloid layer coloured in this manner is coated on a photographic sensitive emulsion on a paper base, a print may be made from a black and white negative, the light affecting the emulsion being mainly that passing through the interspaces between the dyed particles ; development, fixing, and treatment with the ozobrome bath yields a positive print in coloured gelatin. If the paper is of the stripping variety, three such prints, produced from component colour-record negatives may be superimposed to yield a picture in colours. The Provisional Specification describes also the use of indigo-carmine for blue, carmine for red, and the product of mixing solutions of indigocarmine and auramine for green ; the use of acetone, oils, ether and the like as solvents for the dyes ; and the use of a mixture of coloured particles coated on a panchromatic emulsion so that after exposure, development, &c. and treatment with the ozobrome bath, a multicolour screen picture in coloured gelatin results.