Patent GB-1157984-A (GB)
Title: Improvements relating to Producing Colour Separation Records
IPC: G03D11/00
Filed: 1966-07-06
Abstract: 1,157,984. Photographic materials and processes. INTERNATIONAL POLAROID CORP. July 6, 1966 [July 16, 1965], No. 30380/66. Heading G2C. A photographic material for use in an additive colour process comprises, a light transmitting support, a light-sensitive layer or layers and an image-receiving layer, the light-sensitive layer or layers including an overall distribution of at least two silver halides sensitive to visible light in spectral ranges which are not co-extensive with one another, the silver halides having been selectively fogged by exposure of different areas of the layer or layers to different colours, each of which is complementary to the colour sensitivity of a different one of the silver halides, so that different ones of the silver halides are left unfogged in different areas of the material. The invention also relates to a method of producing a silver image comprising different areas representing additive colour separation records of a coloured original; comprising imagewise exposing a photographic material having an overall distribution of at least two silver halides sensitive to light of different colours; developing the exposed material to form positive images by a reversal process; and prior to the development subjecting different areas of the material to a fogging exposure using light of different colours, each colour being complementary to a colour to which one of the halides responds whereby after the fogging and imagewise exposure steps each of the areas has a latent silver record of a colour component complementary to the colour of the fogging light to which it was exposed. Generally the material used in the process is the material described above so that the reversal process used is the silver salt diffusion transfer process and the image-receiving sheet is stripped from the light-sensitive emulsion to leave the silver image. The fogging exposure is normally performed using a line screen of cyan, magenta and yellow and the silver image produced is viewed through a screen of red, green and blue lines of the same width to give the additive colour record. As shown, a light-sensitive material comprising a transparent support 20 coated with an imagereceiving layer 18, a red and green sensitive silver halide layer 12, a yellow filter 14 and a blue sensitive silver halide emulsion 16 is exposed to an original having red, green, blue and white areas. The exposed material is now fog exposed through a line screen of yellow, magenta and cyan lines (Fig. 1b) and the material is now treated with a processing liquid containing a developer and silver halide solvent so that the unexposed silver halide particles (indicated by the circles not containing dots in Fig. 1b) are transferred to layer 18 containing reduction nuclei and thus forming a silver image. The silver halide emulsion layers are now removed and the silver image is projected either through a line screen of red, blue and green lines (of Fig. 1d) of the same width as Fig. lb in contact with the silver image or the silver image is projected on to a screen of red, blue and green lines or a line screen is applied to a light-reflective support before the image-receiving layer so that a coloured reflection print is obtained. An alternative light-sensitive material is one which contains in one layer a mixture of a highly blue sensitive silver halide and less-sensitive red and green silver halide and this material is exposed to the coloured original through a yellow filter.