GB912258A - Improvements in photographic diffusion transfer processes - Google Patents

Abstract

912,258. Photographic silver salt diffusion transfer processes. KODAK Ltd. March 26, 1959 [March 31, 1958], No. 10503/59. Class 98 (2). The transfer is effected in the presence of a silver halide solvent and an onium compound consisting of either a quaternary ammonium salt or a ternary sulphonium salt, the onium radical thereof having an attached chain of at least seven atoms. Such compound may initially be used in the emulsion, the developer, or the transfer material. Improvements therewith include increase in density of the positive image, increase in emulsion speed, rate of development and solvent action of the silver halide solvent as well as image production in neutral black. Two main classes of the sulphonium salts and four of the ammonium salts are quoted with numerous individual compounds falling therein, and an extensive list of tone-modifying substances such as heterocyclic nitrogen and sulphur containing compounds of the type used in rubber chemistry, for use together with such salts, is provided. Numerous amines effective in darkening the tone of the transferred images, especially when used in conjunction with such tone-modifying substances, are listed also ; and a further modification for the same purpose is the use of solvents such as the lower alcohols, ketones, amides and ethers to the extent of 7 to 20% by volume in the developing solutions. Gold salts and other sensitizing materials, and antifoggants such as azaindene compounds may be used in the negative layers from which transfer is made. Twenty-two examples, many of which describe the procedure with several of the onium compounds and quote the relative densities of the transferred images, are provided; thus in Example 1 high-speed bromoiodide emulsions sensitized with methyl-3: 3<SP>1</SP>- diethyl seleno carbocyanine iodide and with gold and sulphur compounds and containing also 4- hydroxy - 6 - methyl - 1: 3: 3a: 7 - tetrazaindene as well as various specified amounts of 7 : 18 - diaza - 6: 19 - dioxotetracosane - 1: 24- bis (pyridinium perchlorate) and 3 : 6 : 9 : 12: 15 : 18 : 21: 24 - octoxahexacosane : 1: 26 - bis (pyridinium bromide) as the quaternary ammonium salts are exposed on an intensity-scale sensitometer, treated with a specified transfer developer and rolled in contact with receiving sheets coated with a gelatine solution containing a dispersion prepared from aqueous lead acetate, zinc nitrate and silver nitrate precipitated with aqueous sodium sulphide and sodium metasilicate with a proportion of nitric acid to obtain positive images on such sheets. Specifications 556,457, 558,710, 649,545, 748,745, 752,030, 755,369, 757,653, 777,181, 778,792, 814,823, 815,075, 868,241, 874;077 and 911,501 are referred to.