Patent GB-544134-A (GB)
Title: Improvements relating to photographic materials
IPC: G03C1/10
Filed: 1940-07-23
Abstract: 544,134. Photographic light-sensitive material. KODAK, Ltd., and KNOTT, E. B. July 23, 1940, No. 12054. [Class 98 (ii)] The tendency for a sensitizing or other dye present in a sensitive photographic emulsion to wander to a neighbouring emulsion is reduced by dispersing a water-soluble salt of a resin or a water-insoluble metal salt of a resin through the first emulsion. The emulsions may be mixed or applied successively to a support after dispersing the salt through the first emulsion. The salt may be added to the liquid emulsion, and may be a water-soluble salt such as the sodium, potassium, or ammonium salt, or may be a water-insoluble salt such as the magnesium, calcium, strontium, barium, aluminium, cadmium, manganese, zinc, cerium, nickel cobalt, copper, or thorium salt. A water-soluble salt may be added, followed by the addition of a water-soluble metal compound which will precipitate the resin as an insoluble salt. The metal compound may be a salt, hydrooxide, or other compound of one of the second group of metals referred to above. The resin may be whole, hard, soft, or hydrolyzed soft shellac; colophony; gum mastic; dammar; sandarach; copal; kauri; or one of the resins known under the Registered Trade Mark " Glyptal." The salt may be added to the emulsion in alcohol solution. A suitable solution of sodium resinate may be prepared by neutralizing an alcoholic solution of de-waxed and bleached' soft lac resin with aqueous caustic soda, and adding distilled water and then a 14 per cent aqueous gelatine solution. The resin salt may be dispersed through an emulsion not containing a sensitizing dye in order to prevent wandering of such dye thereto. In example (1) a mixture of alcoholic solutions of 2:4-dihydroxyazobenzene and calcium resinate is added to a gelatine solution. In example (2), a mixture of an acetone solution of Methyl Red and an alcoholic solution of sodium resinate (or of the sodium salt of soft lac resin) is added to a gelatine solution. In example (3), the pH value of an emulsion is adjusted to about 7 and a 1 per cent solution of water-soluble metal salt or hydroxide is added, followed by a 5 per cent aqueous solution of a resin salt. In example (4), a mixture of an alcoholic solution of 2:4-dihydroxyazobenzene and an alcoholic solution of sodium resinate is added to a gelatine solution to which has previously been added a 5 per cent aqueous solution of nickel or zinc chloride. In example (5), a silver bromide, chloride, or chlorobromide emulsion sensitized with the dye of Fig. 43 of Specification 450,958, is adjusted to a pH of 7 by the addition of citric acid or caustic soda, and a 1 per cent aqueous solution of cadmium nitrate added. After thorough mixing, an aqueous solution of the sodium salt of colophony is slowly run in a stream into the emulsion. After standing for 15 minutes, a second non- colour sensitized emulsion, which may also contain a resin salt, is added. A multi-contrast material is obtained. The cadmium nitrate may be replaced by zinc chloride or cobalt ammonium sulphate, and the sodium salt of colophony by the sodium salt of soft lac resin. Multi-contrast material may have two layers or a mixture of two differently sensitized emulsions of different gradations. Only one of the emulsions may be colour sensitized (e.g. to yellow) or both may be colour sensitized to different spectral ranges. An acid resin salt may be employed. Colour photographic material may be prepared by the successive application to a support of three emulsions adapted to record the blue, green, and red components of a coloured image, the red- and green-recording emulsions each containing a sensitizing dye and also a resin salt. Specifications 540,451, 540,464, 541,558 and 542,507 also are referred to.