Patent GB-1230637-A (GB)
IPC: G03C1/76
Filed: 1968-06-07
Abstract: 1,230,637. Coated film. EASTMAN KODAK CO. 7 June, 1968 [9 June, 1967], No. 27251/68. Heading B2E. [Also in Divisions G2C and H5R] A polymeric film base has a coating comprising (a) a first barrier layer comprising at least one polymer which has a molecular weight of at least 50,000, is soluble in water to the extent of at least 5 weight percent, exhibits a 1% aqueous solution viscosity of not more than 10 poises, and is compatible with gelatin, and (b) an opaque layer comprising at least one water insoluble organic polymer and finely divided carbon, said at least one organic polymer having a Young's Modulus (in tension) of 400 to 5,000 lbs. per square inch and being present in an amount of at least 50 weight % of the opaque layer, the first barrier layer being capable of providing in the dry state only a tight bond between film base and the opaque layer, and the opaque layer being substantially impervious to visible light, insoluble in water, and permeable to liquid water when contacted therewith. A radiation sensitive layer may be coated on the other surface forming a photographic or radiographic film. A photographic element may comprise a radiation sensitive layer, a sub-layer, a polymeric film base, a pelloid layer, a first barrier layer and the opaque layer in that order. At any convenient time after the development of the negative, the opaque layer can be removed by immersing the developed negative for a very short time into either a water bath or a diode aqueous solution. The polymers in the barrier layer may be hydroxy propyl celluloses, alkali metal salts of ethyl cellulose sulphate, copolymers of acrylic acid and ethylacrylate, carboxymethyl celluloses, alkali metal salts of copolymers of methylacrylate and acrylic acid. A preferred alkali metal ethyl cellulose sulphate contains 34 to 40% ethoxyl and 4 to 7% combined sulphur. Combinations of polymers may be used and examples of suitable combinations are given. Combinations of hydroxypropyl cellulose and soda methyl cellulose sulphate are preferred. The polymer in the opaque coating may be initially soluble in water and convertible into a water-soluble polymeric coating, e.g. by curing or cross-linking after it is applied in the form of an aqueous solution. Preferred opaque layer polymers are alkali metal salts of copolymers of ethyl acrylate and acrylic acid. In the examples cellulose acetate (3) and polymethacrylate with cellulose nitrate (5) are used in the opaque coating. The frictional properties of film units made from the resulting coated films can be improved by utilising a thin additional coating over the opaque coating of an anti-friction material consisting of, e.g. 0.5 to 10% of spherical polymeric beads, 0.3 to 8% cellulose nitrate and 0.3 to 8% finely divided carbon. Film units made from a coated film perform satisfactorily in a conventional "film pack" type camera. The coated films can also serve to protect X-ray or other radiographic film from visible light, to protect motion picture film from incident light when extra protection may be needed temporarily until the film is developed. In the case of X-Ray films, the permeability of the opaque coating will permit developers to pass through the coating to carry out the development of the exposed film to a significant extent before the opaque coating is removed.