Patent GB-618352-A (GB)
Title: Improvements in or relating to colour photography
IPC: G03C7/327
Filed: 1946-10-24
Abstract: 618,352. Colour photography. DU PONT DE NEMOURS & CO., E. I. Oct. 24, 1946, No. 31618. Convention date, Oct. 25, 1945. [Class 98 (ii)] A photographic element comprises a support carrying at least one layer of a hydrophilic colour-former-substituted carboxylic acid ester of a vinyl alcohol polymer which has light sensitive silver halide dispersed therein. The polymers are compounds having a number of colour forming nuclei each of which is joined through a carboxylic ester linkage to a separate carbon atom of the vinyl alcohol polymer chain; thus they have groups replacing a portion of the vinyl hydroxyl groups, A being a single co-valent bond or a bi-valent organic radicle and Q a colourformer nucleus capable of condensing or coupling with oxidised primary aromatic amino colour developing agents to form quinone-imine or azomethine dyes or with diazotised aromatic amines to form azo dyes. Aqueous emulsions of the polymers are sensitised, coated, and treated generally by the methods used for gelatin emulsions ; they may incorporate sensitising dyes, preservatives and other usual emulsion constituents which can be added at various stages prior to coating. Four general methods of preparation of the polymers are incidated : (1) esterification of a vinyl alcohol polymer with a colour former containing a carboxylic acid group using an acid catalyst ; (2) esterification of a vinyl alcohol polymer with a colour former containing a carboxylic acid halide in presence of a base ; (3) ester interchange between a vinyl alcohol polymer and a colour former containing a lower aliphatic ester group ; (4) esterification of a vinyl alcohol polymer with an acid or derivative thereof which has a reactive group that may be changed to a colour former group. Numerous colour formers for use by these methods are specified. In example 1 polyvinyl alcohol obtained by complete hydrolysis of polyvinyl acetate is treated with 1-hydroxy-2-naphthoyl chloride in presence of pyridine to give a colour former polymer, this is dissolved in aqueous alcohol at 70‹ C., silver chloride-bromide is introduced into the solution by precipitation, the sensitised colour former polymer is precipitated by addition of sodium sulphate and this precipitate is washed, re-dissolved and coated on paper and on a cellulose acetate film base. The paper and film are exposed, treated with a developer containing p. aminodiethylaniline hydrochloride, washed, bleached with potassium ferricyanide, fixed in hypo and again washed to give blue-green negative quinene-imine dye images. In example 2 polyvinyl alcohol is combined with chloracetic acid to give a partial chloracetate, and this is reacted with m-aminophenol to give a colourformer polymer which, when used in the manner described in example 1 yields blue negative quinone-imine dye images. Examples 3, 4 and 5 are similar to example 2, but use sodium-1-hydroxy-2-naphthaline sulphinate, N- (# - aminoethyl - 1 - naphthol - 2 - sulphonamide and 1-(m-aminophenyl)-3-methyl-5-pyrazolone respectively instead of m-aminophenol ; example 5 yields negative magenta images. In example 6 the naphthoyl chloride of example 1 is replaced by p-acetoacetamidobenzoyl chloride which yields yellow images. Examples 7 and 8 follow the procedure of example 2, but use p-acetoacetamidobenzene sulphonamide and p-acetoacetaminothiophenol, respectively as colour formers. Example 9 describes separation of silver iodobromide from a gelatin emulsion in which it was prepared, and the addition of this washed silver iodobromide to the colour former polymer of example 1. Example 10 describes processing of the layers of prior examples by reversal development. Example 11 describes a threelayer material consisting of, in order, (a) a cellulose acetate film base ; (b) the lightsensitive composition of example 1 which has been sensitised to red but not to green as with N.N<1>-diethylnaphthiocarbocyanine iodide ; (c) the light-sensitive composition of example 5, sensitised to green with erythrosin (d) a hydrolysed polyvinyl acetate layer containing a removable blue absorbing dye such as tartrazine ; (e) the blue-sensitive dye intermediate polymer composition of example 6 ; this film is exposed to a colour scene and then processed as in example 1 to give a colour negative ; reversal development to yield a colour positive is described, and, also production of the latter by printing the negative on to the same (unexposed) film by successive use of blue, green and red lights. Example 12 is similar, but uses a paper base. Example 13 describes the production of a positive azo dye image in the developed film of example 7 by a reversal elimination process. Specifications 545,443, 545,444, and 11153/43, as open to inspection under Sect. 91, are referred to.