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477,153. Photographic films. KODAK, Ltd. June 17, 1936, No. 16911. Convention date, June 19, 1935. Drawings to Specification. [Class 98 (ii)] A photographic film comprises an organic cellulose derivative support and a photographic gelatino emulsion, good adherence of the emulsion and high flexibility being imparted by the application to the base of a very thin substratum comprising a mixture of a colloid and a hydrophobic synthetic resin capable of adhering to the support and by the application between this substratum and the emulsion of a further substratum consisting of gelatine or a mixture of gelatine and a synthetic resin. If the colloid is gelatine, the second substratum may be omitted. The thickness of the very thin substratum may be À00008". The support may be of cellulose acetate, propionate, butyrate, acetate-propionate, acetate-butyrate, or acetatestearate, or may comprise a cellulose ester, for example, cellulose acetate of 90 per cent precipitation value, coated with a thin layer of a cellulose ester of lower precipitation value, for example, cellulose acetate of 69 per cent precipitation value. The colloid may be gelatine or cellulose derivatives such as cellulose acetate. Suitable resins are alkyd resins obtained by reaction between one or more polybasic organic acids and one or more polyhydric alcohols. The resin formed from glycerol and phthalic acid or its anhydride or the resins formed by reaction between a polybasic organic acid, an alcohol having three or more hydroxyl groups in the molecule, a dihydric alcohol, and a dibasic aliphatic acid may be employed. The substrata may be applied by immersion or by a roller. The substrata may be applied to the support on one side or, for example, in the case of X-ray film, on both sides. A non-curling layer of gelatine or other material may be applied to the opposite side of the support. Examples are given of the application to a cellulose acetate support of a gelatine-synthetic resin substratum, of the coating of a cellulose acetate support of 90 per cent precipitation value with cellulose acetate of 69 per cent precipitation value and then with a gelatine-synthetic resin substratum, of the coating of a cellulose acetate support of 90 per cent precipitation value with a substratum comprising a mixture of cellulose acetate of 69 per cent precipitation value and synthetic resin and then with a gelatine substratum, and the successive application to a cellulose acetate support of cellulose acetatesynthetic resin and gelatine-synthetic resin substrata. Specifications 386,740, [Group IV], and 470,565 are referred to.
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