Patent GB-718232-A (GB)
Title: Photographic emulsions and elements
IPC: G03C1/053
Filed: 1952-10-09
Abstract: 718,232. Photographic emulsions. DU PONT DE NEMOURS & CO., E. I. Oct. 9, 1952 [Oct. 20. 1951], No. 25343/52. Class 98(2) Photographic elements of reduced lustre are produced by the use of a water-permeable colloid layer having dispersed therein an ethylenic addition polymer at least 65 per cent by weight of which consists of fluorinated ethylene units containing 3 or 4 fluorine atoms. The polymer may be dispersed in a colloid silver halide emulsion or in a non- light-sensitive water-permeable colloid layer supercoated on the silver halide emulsion layer. The polymers are derived from trifluoroethylene, chlorotrifluoroethylene, tetrafluoroethylene or mixtures thereof, or they may be copolymers of these substances with ethylene, propylene, butene-1, butene-2, vinyl fluoride or 1: 1-difluozoethylene. The particle size of these polymers may vary from 0.05 to 25 microns but is usually from 0.05 to 0.5 microns. An aqueous dispersion of the polymer containing, for example, from 10 to 60 per cent solids, and having a pH of 2-10, may be added to the water-permeable colloid emulsion, and in the case of silver halide emulsions, the polymer may be present in an amount of from 0.5 to 100 g per litre of emulsion and preferably from 50 to 500 g per 1.5 mols of silver halide. The aqueous dispersions of polymer may contain a dispersing agent, e.g. non-ionic wetting agents such. as octyl phenol polyglycol ether and polyoxyethylene sorbitan monolaurate, and anionic wetting agents such as sodium decyl, tetradecyl, hexadecyl, octadecyl sulphates. The colloid binding agent may be gelatin, hydrolysed ethylene/vinyl acetate copolymer, agar-agar, a polyglycuionic acid, zein, collodion, hydrolysed cellulose acetate, a cellulose ester of a hydroxy monocarboxylic 'acid, e:g: lactic or glycolic acid, or alkali metal salt of a cellulose ester of a dicarboxylic acid, e.g. phthalic acid, polyvinyl alcohol, partially hydrolysed polyvinyl acetate or a copolymer thereof with styrene or maleic acid, or a water-soluble polyvinyl acetate. The colloid layers may be supported on bases of cellulose nitrate, triacetate. propionate, acetate propionate, or acetate butyrate; polyvinyl chloride or a copolymer thereof with a monoethylenically unsaturated monomer, polystyrene, polyacrylonitrile, polyvinyl fluoride, nylon; a polyester of a glycols and a dicarboxylic acid, e.g. polyethylene terephthalate, glass or transparentized paper. Sensitizers such as allylthioureas, thiocyanates, or allylthiocyanates can be added to the emulsions. In an example. an aqueous dispersion containing 50 per cent of a tetrafluoroethylene polymer and 6 per cent by weight of the solids of an octyl phenyl polyglycol ether is mixed with a gelatin silver chlorobromide emulsion containing a sensitizing dye, glycerine, benztriazole and chrome alum, and the resulting emulsion coated on a baryta-coated paper and dried. In another example the pH of such an emulsion is adjusted to 9-10 with ammonium hydroxide, before coating. Other examples are given. Specifications 376,746, 513,471, 519,895, 527,283. 537,961, 542,704, 574,688, 585,625, [both in Group IV], 598,477 and 600,023 are referred to.