Patent GB-442522-A (GB)
Title: Improved process for the production of multi-colour photographic pictures, and photographic material therefor
IPC: G03C7/20
Filed: 1934-08-02
Abstract: 442,522. Colour photography. I. G. FARBENINDUSTRIE AKT.-GES., Frankfort-on-Main, Germany. Aug. 2, 1934, No. 22562. Convention date, Aug. 4, 1933. [Class 98 (ii)] A multicolour picture to be viewed by reflected or transmitted light is produced by direct photography, or by reproduction from a coloured transparency or projected picture (including multicolour screen and lenticular screen pictures) by forming the component colour images by simultaneous exposure in the separate layers of a pack comprising thin, colour-sensitive silver halide layers each on a separate thin support of thickness not more than 50-80Á and each coloured with a finelydispersed photographically-indifferent pigment consisting mainly of particles of a diameter less than 1Á, and colour-sensitized in a manner complementary to its pigment colouring, developing the colour component images as gelatin reliefs after exposure, and using them directly or indirectly for building up the multicolour picture. For tricolour, the layers may be coloured yellow, blue-red, and greenish-blue in that order, or with the blue-red and greenishblue reversed. For bicolour, orange-red and blue-green layers may be used. The supports may be of celluloid, cellulose acetate, varnished cellophane, polyvinyl chloride, or polyacrylic acid ester. If the pack is exposed to an original object or a colour positive, the layers are developed to positive reliefs in the known way with a bath containing hydrogen peroxide acidified with sulphuric acid and containing copper sulphate and potassium bromide, which bath removes the parts of the gelatin containing the developed silver image ; while if an unreversed multicolour screen picture is copied on the pack, the layers are developed to positive reliefs by tanning development, or ordinary development followed by chromic acid hardening of the gelatin image-containing parts, with subsequent removal of the non-hardened gelatin. The pack may also be used to copy negative or positive colour component images. To form the finished picture, the developed reliefs may be stuck together in register or superimposed by transfer as upon gelatin-coated paper, or they may be dyed up to produce dye-impression prints in superimposition in a single layer as of gelatin on paper. Registration is effected by the help of pinholes formed in the pack, and pins in the printing frame, &c. The pigments used for colouring the emulsion layers must be waterinsoluble, and indifferent to the photographic baths whether acid or alkaline, and they must not materially affect the sensitivity of the emulsions. There may be used stable colour lakes, complex salts of basic triphenylmethane dyestuffs or xanthene dyestuffs with phosphoric, molybdic, or tungstic acids (Fanal-lakes) ; or vat dyestuffs such as indigo or Indanthrene blue 8G. The pigments may be dispersed by comminution, or colloido-chemically as by the use of wetting and dispersing agents, or by both methods in succession. As wetting or dispersing agents there may be used for example sulphonic acids of lignin, or compounds of the lignin type such as Dekol for the Fanal-lake of Rhodamine ; and condensation products formed by the action of ethyleneoxide on octadecyl-alcohol, cetyl-alcohol or the monoethyl ether of diethylene glycol for indigo. These agents may be left in the emulsion or removed wholly or in part before finishing the emulsion, e.g. before the halide is formed in the gelatin. A tripack is described comprising thin films sensitized for blue, green, and red and coloured respectively with Hansa yellow 10G, Indanthrene Red BN, and Indigo BASF /G, and matched in sensitivity and gradation.