Improvements in or relating to the production of photographic materials


585,759. Photographic materials. HART, J. A. H., PANKHURST, K. G. A., and SMITH, R. C. M. Oct. 30, 1944, Nos. 21092 and 24779. [Class 98 (ii)] A method for coating a layer in photographic material comprises coating on a supporting surface forming an element of such material, a dispersion in a predominantly organic solvent medium of a complex of gelatin with the anion of an anion soap containing a sulphur acid grouping, or with the anion of or a sulphonic acid containing a highly hydrophobic anion. The aqueous dispersion from which the complex is formed may be at a pH value below the isoelectric point of the gelatin, or at a higher pH value and containing an electrolyte. The precipitated complex may contain a. small amount of water, which may be included in the organic solvent dispersion. Another colloid, soluble in the solvent medium already present or in a solvent medium miscible with that already present, may be incorporated in the dispersion. The complexes may be formed by the addition of the anion soap solution to a gelatin solution, or by allowing the gelatin to stand in a solution of the anion soap. They may be dispersed in the organic solvent medium with or without previous washing. The free acid may be used instead of the anion soap. A method is described for determining the optimum ratio of soap to gelatin to obtain complexes of the highest solubility in organic solvents. For complexes of the greatest solubility in organic solvents, the anion of the soap should be as strongly hydrophobic as possible, the pH should be below the isoelectric pointof the gelatin, and the electrolyte concentration should be as low as possible. The pH value may be from 2.5 to 3.0, or as low as 2.0. Anion soaps specified are soluble salts of: (a) long-chain alkyl sulphonic acids; (b) sulphated higher fatty alcohols, e.g. in which the alkyl group contains at least 8 carbon atoms such as lauryl and oleyl hydrogen sulphates; (c) sulphated secondary alcohols containing at least 8 carbon atoms in the chain ; (d) alkylated aromatic sulphonic acids, e.g. alkyl benzene, alkyl naphthalene, and alkylated hydroxydiphenyl sulphonic acids ; and (e) long-chain chain alkyl esters of sulphated succinic acid. Alkali metal (sodium or potassium), ammonium, or amine (triethanolamine or cyclohexylamine) salts may be used. The anion may contain an amino residue as in sodium oleoylaminoethanesulphonate. Numerous commercial anion soaps are specified. Sulphonic acids specified are 2-naphthol-1-sulphonic acid, 1- naphthol-4-sulphonic acid, anthraquinone-2- sulphonic acid, Kiton Fast Yellow 3G, and Naphthalene Orange GS. The organic solvent may contain hydroxy groups, e.g. methyl or ethyl alcohol, ethylene glycol monomethyl ether, ethyl lactate, or diacetone alcohol, or may be acetone, methyl ethyl ketone, dioxane, methylene chloride, chloroform, or mesityl oxide, with or without water or methyl alcohol. Esters such as methyl or butyl acetate, ethers such as diethyl ether, or hydrocarbons such as benzene or toluene may be added. The complex may be swollen in the organic solvent medium and dispersion facilitated by gentle warming. The additional colloid may be cellulose ester such as cellulose nitrate or acetate or a far-hydrolysed cellulose acetate, a polyvinyl acetate or acetal, a methyl methacrylate polymer or a partially hydrolysed derivative thereof, an alkyd resin, or a interpolymer of maleic acid or anhydride with styrene or methyl methacrylate. The layers may be substratum, antihalation, filter, antiabrasion supercoat, and antistatic layers, and colour former layers to be coated adjacent the emulsion layer. Dyes, pigments (including colloidal silver), or colour formers may be present in the original aqueous gelatin dispersion from which the complex is formed, or may be added at any later stage in the preparation of the coating solution. In example 1, a complex is formed by the successive addition to an aqueous gelatin solution of an aqueous solution of " Agral N " (Registered Trade Mark), which is a sodium alkylnaphthalenesulphonate, and of hydrochloric acid. The washed complex is dissolved in hot methyl alcohol, reprecipitated by the addition of water, redissolved in methyl, alcohol, and cellulose nitrate added. A cellulose nitrate lacquered metal support is coated with the solution and then with sensitive emulsion. In example 2 cellulose acetate film is subbed with a solution prepared by diluting with methyl alcohol and acetone a solution obtained by adding to a solution comprising gelatin, water, methyl alcohol, and salicylic acid a solution of Perminal N (Registered Trade Mark), dissolving the washed precipitate in hot methyl alcohol, reprecipitating -with water, and redissolving in methyl alcohol. Cellulose acetate film may also be subbed with a solution prepared by adding to an aqueous solution of gelatin purified as in Specification 558,262 an aqueous solution of the free acid obtained by extracting with ether an acidified solution of Perminal N (Registered Trade Mark), dissolving the complex in warm methyl alcohol, reprecipitating with water, washing, redissolving in warm methyl alcohol, and diluting with acetone ; with a solution prepared by adding hydrochloric acid and Teepol X to an aqueous gelatin solution, dissolving the complex in methyl alcohol, reprecipitating, redissolving in methyl alcohol, and diluting with acetone; and with a solution prepared by adding aqueous naphthalene-2-sulphonic acid to an aqueous gelatin solution, dissolving the complex in hot methyl alcohol, diluting with methyl alcohol and acetone, and adding 40 per cent formaldehyde solution. In example 3, an aqueous solution of Kiton Fast Yellow 3G is added to an aqueous solution of gelatins purified as in Specification 558,262, and the complex is dissolved in methyl alcohol and coated as a filter layer over a dried photographic gelatin emulsion layer. The dye can be removed with water before or after processing. A filter layer or coating over an emulsion layer may also be prepared by adding to an aqueous gelatin solution ammonium nitrate and Teepol X, stirring the complex with xylene and boiling to remove water, adding further xylene, and diluting with toluene containing Cellaquer Red 75079. In example 4, an antistatic layer is prepared by diluting the xylene solution of example 3 with benzene and coating on cellulose nitrate film. In example 5, Agral N (Registered Trade Mark) and hydrochloric acid are successively added to an aqueous gelatin solution, and the washed complex is dissolved in hot methyl alcohol, reprecipitated with water, redissolved in hot methyl alcohol, again reprecipitated, dissolved in hot methyl alcohol, and diluted with methyl alcohol and acetone. Cellulose acetate film may be subbed with the solution and then coated with a gelatino silver halide emulsion. Acid Green G may be added to the solution, which is then coated as an antihalation layer on the opposite side of a cellulose acetate film to a panchromatic emulsion: The solution may be used as an antiabrasion supercoat over an emulsion layer. Baryta may be added, and the solution coated on paper, followed by an emulsion layer. The solution may be diluted with ethyl alcohol and coated on cellulose nitrate to form an antistatic layer. The solutions may be spray-coated. Emulsioncoated paper for use in printing from wet negatives may be supercoated with the solution, which may contain other colloids such as cellulose nitrate or methyl methacrylate-methacrylic acid co-polymer. The emulsion layer may be formed from a dispersion of gelatinsilver halide-anion soap complex in organic solvent as described in Specification 585,758. Specifications 537,256 and 585,504 also are referred to.




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