GB364852A - Improvements in or relating to photographic films - Google Patents

Abstract

364,852. Photographic films. KODAK, Ltd., Kodak House, Kingsway, London, and CROWTHER, R. E., 32, Park Lane, Wembley, Middlesex. Jan. 13, 1931, No. 1188. [Class 98 (ii).] Relates to anti-halation films of the kind having the sensitive emulsion on one face of a support and a dyestuff layer on the other face, and consists in applying to the outer face of the dyestuff layer an adherent, isolating layer or coating to prevent adverse action of the dyestuff on the emulsion, e.g. in roll spools or film packs. The isolating layer is preferably formed of a colloid which is soluble in, pervious to, or swollen by water or other liquids with which the film is treated after exposure. Where the colloid is substantially insoluble in water the layer must be sufficiently thin to permit water to penetrate to the dyestuff layer. Suitable colloids include albuminoids such as casein and gelatine, gums such as gum arabic and gum tragacanth, starch, regenerated cellulose, solutions of cellulose esters and ethers, natural and synthetic resins either soluble or non- soluble in alkali, &c. For dry climates, a water-soluble cellulose derivative, e.g. cellulose aceto-lactate, is suitable ; but for humid climates a water-insoluble but alkali-soluble material is preferred, e.g. a coating of eggalbumen in water rendered insoluble by heat, cellulose nitrate, water-insoluble proteins such as alkali-soluble casein, or a spirit-soluble gum or resin such as sandarac with a small amount of wax such as stearic acid. Examples of suitable coating solutions are (1) cellulose acetolactate 4 parts, water 90 parts, glycerine 1/10 part, and saponine 1/10 part ; (2) egg albumen 3 parts, water 100 parts ; (3) cellulose nitrate 10 parts, butyl acetate 200 parts, ethyl acetate 800 parts.