Patent GB-774534-A (GB)
Title: Process for the production of colour photographic pictures
IPC: G03C7/26
Filed: 1954-03-31
Abstract: 774,534. Colour photography. CIBA Ltd. March 31, 1954 [April 1, 1953], No. 9496/54. Drawings to Specification. Class 98(2) A process suitable for making a 2-colour picture, 2-colour part of a 3-colour picture, or a 2 or 3 colour technical drawing using a stratified single layer material, and adaptable for masking using a 3-layer material, comprises treating a photographic material containing at least two metallic silver images at different depths in a single layer, at least one of which is in close proximity to a reducible dye or dye component while at least another is not in such close proximity, to destroy the silver image in close proximity to the dye or dye component and form a dye image or images thereby, and then converting the remaining silver into a dye image in the same or another way. In Example 1, a film sensitive to blue and green light is surface-treated with tartrazine, exposed to a step-wedge with. blue and with yellow light, developed, fixed, washed to remove the tartrazine, hardened in formaldehyde, treated rapidly with the blue-green azo dye of Example 2 of Specification 352,368 [Group IV] and then with 2-naphthyl biguanide to precipitate the dye, treated in a specified dye-bleach bath to remove the silver image from the blue light exposure and form a reversed dye image thereof, after which the silver image from the yellow exposure is converted to a colour image by rehalogenation and colour development procedure. In Example 2 the film of Example 1 is exposed similarly through the support to result in colour images in reversed order. Variations of the procedures of Examples 1 and 2 by which improved differentiation of the images may be obtained are indicated. Example 3 describes almost complete separation of two images by exposure of a film as of Example 1 through blue filters from opposite sides, dye-destruction treatment to eliminate the silver image formed on the emulsion side with production of a blue positive image thereon, immersion in hypo, rehalogenation and pyrazolone colour development to purple of the other image followed by a conventional bleaching sequence to remove the reformed silver. In Example 4 a blue sensitive film is surface sensitized to green, immersed in tartrazine, exposed through a step wedge from the rear using ,blue and yellow filters, developed in metol-hydroquinone, fixed, dyed as in Example 1, subjected to dye destruction, and later colour developed with acetoacetanilide to result in yellow negative and blue positive images respectively from the filter exposures. Examples 5 and 6 describe with the aid of diagrammatic drawings (not shown), the copying of an original picture in colours of grey. yellow and blue to result in a two-colour copy and masked separation records respectively. Example 7 is directed to the production of a twocolour picture in blue-green and yellowred in a single layer. Example 8 describes a three-layer negative comprising a red-sensitive blue-green coupler layer containing a red azo dyestuff, a green sensitive purple coupler layer containing a yellow azo dyestuff, yellow filter layer and blue sensitive yellow coupler layer, exposure development in metol-hydroquinone to produce more silver than is necessary for colour development, fixing, dye destruction to leave flat positive azo dye masking images in the two lower layers and remove silver solubilized thereby, rehalogenization and colour development of the remaining silver, and removal of the reformed silver in the usual manner, to result in a masked multicolour negative. Example 9 states that a technical drawing made with black, white and blue inks on a yellow ground is photographed on 35 mm. film, which has been pretreated as described in Example 4, with the support facing the objective; and that processing is carried out as in that example to give a picture which when projected reproduces the elements of the original in blue, yellow and green respectively on a colourless ground. Contact copies of the technical drawing are stated to exhibit the same advantages. Specifications 516,816, 522,691 [Group III], 539,190, 553,352 and 738,233 also are referred to.