GB795186A - Improvements in and relating to colour photographic processes - Google Patents

Abstract

795,186. Colour photography. FRAUNHOFER, H., VON, and COOTE, H. E. May 28, 1954 [March 2, 1953; April 2, 1953], Nos. 5748/53 and 9215/53. Class 98(2) Negatives are produced by developing and fixing a colour photographic primary material including at least two silver halide emulsion . layers sensitized to different colours, bleaching the image in the outermost layer, applying a take-off material including a metallic sulphide thereto to produce an image in silver sulphide of such outermost image and thereby obliterate the latter, and printing the remaining image or images of the primary material. Couplers are usually included in the layers, particularly in the lower layer or layers. Three examples are each concerned with three layer materials, thus in Example 1 as material of layers (a) blue sensitive with or without yellow coupler (b) yellow filter, (c) green sensitive with magenta coupler, (d) red sensitive with cyan coupler followed by anti-halo and transparent base is exposed, colour developed, acid stopped, fixed, bleached, and contacted with take-off material having a layer prepared from gelatine, cadmium nitrate and sodium sulphide, and which layer has been treated with hypo, to produce the silver sulphide image. The magenta and cyan images of the original material are then printed on to a material of layers (e) green sensitive with magenta coupler, (f) red sensitive with cyan coupler, colloidal silver filter, (g) blue sensitive with yellow coupler and then transparent base through which, finally, the silver sulphide image is printed. This latter material is then reverse developed. Solutions and times of use of such for the operations except for the last, the reverse development procedure, are quoted. If a coupler is present in layer (a) the material may, finally, be printed in the normal manner whilst still permitting use of the process detailed. Other substances than cadmium nitrate for use in making the takeoff layer are quoted. Example 2 describes a negative film of layers (h) blue sensitive, no coupler; yellow filter, (i) red sensitive with coupler; transparent base, and then (j) green sensitive, no coupler; and describes, briefly, procedure therewith involving silver sulphide take-off images from both outermost layers. Example 3 indicates the production of tricolour positive film and three silver sulphide positive records from any commercially available colour negative film by a process which includes use of bleaches of successive penetrating power, each followed by the take-off procedure, for the three emulsion layers. Specification 684,248 is referred to.