Patent GB-566832-A (GB)
Title: Improvements in or relating to photographic materials
IPC: G03C1/74
Filed: 1943-06-18
Abstract: 566,832. Photographic dry-stripping material. HART, J. A. H., and LEE, E. W. June 18, 1943, No. 9825. [Class 98 (ii)] Photographic material comprises in superposition a temporary support layer (e.g. paper or film), a dry-stripping hydrophobic adhesive layer, a photographic emulsion layer, a bonding layer consisting of an organic colloid insoluble in aqueous solutions, and a layer of thermo. plastic synthetic resin having a softening point lower than the softening points of the adhesive and bonding layers. The temporary support may be given a thin coating of gelatin or other colloid prior to application of the stripping layer. The bonding layer is preferably a cellulose derivative or alkyd resin layer. The resin layer preferably softens at about 100‹ C. The material is applied before or after exposure to a permanent support of metal, wood, or other material, the resin is softened by heating the combination under pressure, the assembly is allowed to cool and the temporary support with its adherent colloid and stripping layers is stripped off. The gelatino emulsion layer should, in order to facilitate adherence to a cellulose nitrate bonding layer, be acid in reaction and/or should contain an anionic wetting agent. The emulsion may contain hydrochloric or salicylic acid or sodium methyltridecylsulphate, triethanolamine dodecylsulphate, or sodium dodecylsulphate. The cellulose nitrate is applied from solution in ethyl or methyl alcohol, which solvents may contain up to 50 per cent of ethyl ether or acetone. The synthetic resin may be of the polyacrylic, polymethacrylic, polyvinyl, or alkyd series of resins, e.g. polyvinyl acetate. In an example, paper is successively coated with layers of gelatin, gum dammar (from a solution in trichlorethylene and benzene), a gelatino silver halide emulsion containing a long-chain wetting agent, cellulose nitrate (from a solution in ethyl ether and methyl alcohol), and "GELVA 1¢" (Registered Trade Mark) (from a solution in ethyl alcohol); Before or after formation of a latent image, the resin surface is contacted with sheet aluminium, the assembly heated to about 100‹ C. in a hot press and allowed to cool, and the paper support and adherent gelatin and gum dammar layers stripped off. The emulsion layer is exposed (if necessary), developed and processed. The stripping layer may alternatively be formed from a solution of " BEDESOL 72 " in acetone or from a solution of " DIAKON D " (Registered Trade Marks and cellulose nitrate in dioxane and acetone. The bonding layer may be replaced by a solution of " PARALAC 20 " (Registered Trade Mark) in triethanolamine, acetone, methylated spirit and water, or by a solution comprising gelatin, salicylic acid, water, cellulose nitrate, methyl alcohol, and acetone. The resin layer may alternatively be formed from a solution of the polymerized methacrylic ester of ethylene glycol monomethyl ether in toluene and benzene. The emulsion layer may be matted, and the bonding and/or resin layers may contain a white or coloured pigment to facilitate viewing the image. A coloured pigment reduces halation. The opposite side of the temporary support may be coated with a layer to which the resin poorly adheres, e.g. gelatin or casein. The temporary support may be opaque.