Patent GB-1286831-A (GB)
Title: A method of producing coloured radiographs
Inventor: LISHOUT JAN AUGUST VAN
IPC: G03C5/16
Filed: 1968-08-22
Abstract: 1286831 Producing coloured radiographs with silver halide materials AGFA GEVAERT 8 Aug 1969 [22 Aug 1968] 37355/69 Heading G2C [Also in Divisions C2 and H5] A coloured radiograph of an object is produced by irradiating the object with X-rays or other penetrating radiation, the emergent object-uize modulated beam of radiation or a beam of secondary radiation emitted in dependence on such emergent (primary) radiation irradiating a recording material which comprises a silver halide emulsion layer sensitive to the radiation incident on the recording material and which incorporates (a) at least one colourless colour coupler capable of forming an azomethine or quinonimine dyestuff by coupling with an oxidized aromatic amino developing agent, and (b) at least one colourless compound which is capable of oxidative coupling with said colourless colour coupler to form a dye; and wherein the thus exposed seconding material is subjected to development processing to form therein developed radiographic images of the object which are of contrasting colour and of opposite gradation, the maximum density of one of such developed images being at least 50% of the maximum density of the other of such images; such development processing comprising colour developing the exposed silver halide with an aromatic amino developing agent to produce in the exposed areas of said emulsion layer an axomethine or quinoniunine dyestuff image of a colour contrasting with the colour of the dye which forms on oxidative coupling of said ingredients (a) and (b), and removing the silver metal produced during said development with an alkaline oxidizing bleaching solution thereby effecting the oxidative coupling of said ingredient (h) with residual quanta of ingredient (a) which were not used in forming said dyestuff. In a modification of this process ingredient (a) and/or (b) may be introduced into the material during the development processing of the exposed material. The developing agent is preferably a pphenylene-diamine developing agent. Ingredient (a) may have the formula:- wherein R is a carboxylic acid acyl group or a sulphonic acid acyl group (substituted or insubstituted). Ingreadient (b) may be a hydrazone containing the group:- wherein R 2  is -CONH 2  or -SO 2  X wherein X is OH, amino, substituted amino, a heterocyclic group, alkyl, substituted alkyl, aryl or substituted aryl; R 3  is H, alkyl, allyl, aralkyl, aryl or substituted aryl; L 2  is a methine group or N; and n is 1 or 2, or may have the formula:- wherein R 1  is H or acetyl; R 2  is alkyl or aryl; Z completes a heterocyclic nucleus containing 5-6 members; and X is OH, amino, alkyl, aryl or a heterocyclic group, or may have the formula: - wherein R 1  is H or acyl; Y completes an N- containing heterocyclic nucleus; R 2  is H, amino, alkyl, aryl or a heterocyclic group; and X is OH, amino, analiphatic hydrocarbon group, aryl or a heterocyclic group. One of the developed radiographic images may absorb in the red and green regions of the visible spectrum, its absorption capacity in the green region being at least 30% of its absorption capacity in the red region. Colour radiographs having excellent contrast and a higher discemability of the details of the image produced than black and white radiographs are obtained.