Patent GB-543290-A (GB)
Title: Improvements in or relating to the preparation of dyestuffs and to their use in colour photography
IPC: G03C7/327
Filed: 1940-03-13
Abstract: 543,290. Artificial filaments; films ; dyes ; synthetic resins; dyeing artificial fibres. DU PONT FILM MANUFACTURING CORPORATION. March 13, 1940, No. 4755. Convention date, March 14, 1939. [Classes 2 (ii), 2 (iii) and 15 (ii)] [Also in Group XX] In the production of coloured photographic images, dyes are produced by reaction, (a) between an aromatic amino compound which is oxidized under the conditions of the reaction and a colour-former consisting of an alkali-soluble condensation product of formaldehyde and an aromatic carboxylic acid, or a salt thereof, having a hydroxyl group in the para-position to the acidic or salt group, and containing two reactive positions, or (b) between a solution of an aromatic nitroso compound or a solution of a diazo compound and the colour former. The aromatic carboxylic acid may be substituted by halogen atoms or by groups such as amino, amido, alkyl, aryl, aralkyl, alkoxy, aryloxy, nitro, and hydroxy. Acids specified are 4-hydroxybenzoic, 2 : 4-dihydroxybenzoic, 2-chloro-4-hydroxybenzoic, and 2-methoxy-4-hydroxybenzoic. If the condensation reaction is effected under mild conditions with a short period of heating and in the presence of a weakly acid or alkaline catalyst, a low molecular weight product suitable for incorporation in a colour developer solution is obtained. If the reaction is carried further, the higher molecular weight product, may be incorporated in a photographic emulsion. Catalysts such as hydrochloric, p-toluene sulphonic, or sulphuric acid; sodium, ammonium or potassium hydroxide; or ammonium chloride or sodium acetate may be employed. The developing agents may be p-phenylenediamine, p-methylaminoaniline, p-ethylaminoaniline, p-aminodimethylaniline, p-aminodiethylaniline, p-aminodibutylaniline, chloro-p-phenylenediamine, N-methyl-N-hydroxyethyl-p-phenylenediamine, N-butyl-N- hydroxyethyl-p-phenylene-diamine, N-# : ydihydroxypropyl-p-phenylenediamine, N : N- diethyl-o-phenylenediamine, 1: 2 : 5-toluylenediamine, 2-amino-5-diethylaminotoluene, N-paminophenylpiperidine, and p-aminophenol. Salts such as the hydrochlorides, sulphates and acetates may be used. In adding the colourformers to an emulsion or to a developing solution, they are dissolved in aqueous alkali or alkali. carbonate. Small amounts of organic solvents such as ethyl alcohol or acetone may be added. In an example, p-hydroxybenzoic acid, aqueous formaldehyde, ammonium chloride, and water are refluxed together for 21 hours, and the white solid separated out on chilling is freed from excess water and heated for 2 hours at 150 C. The product is dissolved in dilute sodium carbonate solution containing a little ethyl alcohol and incorporated in a panchromatic emulsion. On exposure and development with p-aminodiethylaniline, a blue-green picture is formed. In a second example, the white solid is dissolved, without further heating, in dilute sodium carbonate solution and then incorporated in a colour developer, which is used to develop a silver image bleached with potassium ferricyanide to blue-green. In a third example, p-hydroxybenzoic acid, aqueous formaldehyde, and hydrochloric acid are refluxed together for 4 hours. and after chilling and filtering, the product is washed with water and incorporated in sodium carbonate solution in an emulsion. After exposure, development, and washing, the emulsion is treated with diazotized p-nitraniline to produce a diffuse orange red dye. In a fourth example, the catalyst used is sodium hydroxide . and the refluxing period is 77 hours. The resin produced is incorporated in a panchromatic emulsion which is then coated on a cellulose acetate support. The exposed film is developed and the silver removed with a potassium dichromate and sulphuric acid bath. The film is reexposed, developed with p-aminodiethylaniline, bleached with potassium ferricyanide, and fixed to give a blue-green image. In a fifth example, 2 : 4-dihydroxybenzoic acid, aqueous formaldehyde, and ammonium chloride are refluxed together for 8 hours and the resin, freed from water, is heated for 6 hours at 150-170 C. The resin may be incorporated in an emulsion, a deep blue image being produced on colour development. Salicylic acidformaldehyde resins are unsatisfactory. Specifications 133,034, [Class 98 (ii)], and 489,161 are referred to. The Specification as open to inspection under Sect. 91 comprises also the use of colour formers consisting of an alkali-soluble condensation product of a resin-forming reagent, such as glyoxal, benzaldehyde, hexamethylenetetramine, 2: 6-dimethylol-4-methylphenol, dimethylolurea, dimethylguanidine, chloroform, sulphur dichloride, and phosphorus oxychloride. and an aromatic carboxylic or sulphonic acid, or a salt thereof, having a hydroxyl group in the para-position to the acidic or salt group. and containing two re-active positions. Sulphonic acids specified are 4-hydroxybenzenesulphonic acid, 2 : 4-dihydroxybenzenesulphonic acid, 2-ethoxy-4-hydroxybenzene sulphonic 'acid, 1-naphthol-4-sulphonic acid, and 1 : 8-dihydroxynaphthalene-4-sulphonic acid. Examples are given using (a) sodium phenol-p-sulphonate and formaldehyde, and (b) sodium 1-naphthol-4-sulphonate and formaldehyde. The resins may be incorporated in viscose (or methyl cellulose, ethyl cellulose. glycol cellulose, or cellulose glycollate) dope and, after coagulation into fibres or films, colour may be produced by treatment with diazo compounds, such as diazotized p-nitraniline. This subject-matter does not appear in the Specification as accepted.