Patent GB-657106-A (GB)
Title: Colour photography
IPC: G03C7/18
Filed: 1948-03-22
Abstract: 657,106. Colour photography. GENERAL ANILINE & FILM CORPORATION. March 22, 1948, No. 8449. Convention date, May 7, 1947. Drawings to Specification. [Class 98 (ii)] A multi-layer film comprises a support bearing superimposed red, green and blue-sensitive silver halide emulsion layers each of which contains a mixture of either two or three dye image intermediates for production of cyan, magenta and yellow dyes, the dye image intermediates being colour formers, hydrophilic synthetic polymer colour formers, or dyes for the dye destruction process. Instead of using intermediates of minimum colour degradation, the degradation of the individual colour images is increased so that each colour image, formed after exposure and processing, is degraded to approximately the same extent; the resulting colour reproduction is highly degraded with black, and when a panchromatic record constituting a mask, opposite in negative-positive character to this and equal to the amount of degradation present is registered with the colour reproduction, copies made from the combination using the primaries for exposure comprise completely colour-corrected records of the original, the same mask serving for all three records. Such mask may be made as an integral part of the colour reproduction. The relative amounts of the several dye image intermediates to be used in each layer to produce the required matched colour degradation are found by a series of trials and generally it is desirable to degrade all the resultant mixed dyes or " secondaries " so that they match the worst degradation present in any one secondary; thus to degrade the secondaries to 50 per cent, which may be the blue degradation of the magenta dye; example (1) specifies, as a preliminary red-sensitive emulsion, a kilogram of a specified wet gelatino silver-bromoiodide emulsion sensitized with 5-[1-phenyl-2-(3-ethyl-6,7- tetrahydrobenzobenzothiazolylidene - 2) - ethylidene] - 2 - (3 - ethyl - 4,5 - -diphenylthiazolylidene-2- methylene) - 4 - keto - 4,5 - dihydrothiazole allyliodide containing 13.5 grams of 2-stearylaminocarboxy-4-sulpho-α-naphthol as cyan colour former, which emulsion is coated, exposed in a sensitometer and processed to colour in the usual manner and read in a densitometer, to show contrast of the blue and green densities considerably below half of that of the red density. An intermediate red-sensitive emulsion is made by adding, to this preliminary redsensitive emulsion containing cyan colour former, 3.5 grams of 1-(4<SP>1</SP>-phenoxy-3<SP>1</SP>-sulphophenyl) - 3 - stearyl - 5 - pyrazolone as magenta colour former, and on this showing a green contrast half of the red, but a blue contrast still somewhat low, 6 grams of p-stearylaminobenzoylacetamino-5-terephthalic acid as yellow colour former are added and this constitutes a final red-sensitive emulsion ready for coating on film base. Green-sensitive and blue-sensitive final emulsions, the former containing 3,31,9- triethyl-5,5<SP>1</SP>-diphenyloxacarbocyanine iodide as sensitizer with specified proportions of the above-mentioned cyan and magenta colour formers, and the latter no sensitizing dye but all three colour formers are arrived at by a comparative testing procedure and coated over the red-sensitive emulsion with a yellow filter layer between them, and this film may either be exposed, processed and used to make a colour correction mask leading to the production of colour corrected separation records as above described, or may be colour-developed, bleached with aqueous sodium ferricyanide and chloride, treated in 20 per cent sodium sulphite to remove the silver chloride formed during the bleaching treatment without affecting the remaining silver bromide, re-exposed, developed in a metol-quinol developer and fixed, to provide a colour negative with superimposed dye images of equal degradation, and silver positive images in each of the three layers to neutralize this degradation. Using the same final emulsions an analogous positive film suitable for making colour-corrected negative separations or for direct printing on another multi-layer colour film may be made by reversal development. Example II specifies the final red, green and blue-sensitive emulsions using the same sensitizing dyes but containing Direct Sky Blue (C.I. 520), Fast Acid Magenta B (C.I. 30) and Dianil Yellow (C.I. 650) and the procedure for making similar positive films with either separate or integral silver masks by the dye destruction process. Example IV specifies the final red, green and blue-sensitive emulsions and indicates the procedure of effecting the invention using silver halide-synthetic polymercolour former dispersions. Example III describes a modification in which the multi-layer film is free from colour-forming components but these, in balanced ratios, are present in developers used in reversal processing.