1,218,933. Photographic diazotype materials. RICOH K.K. March 21, 1968, No. 13773/68. Heading G2C. A heat-developable diazotype material comprises a support coated on one surface with a mixture containing a diazonium compound, a coupler, an acid stabilizer, a heat-sensitive salt which generates alkali on heating which is selected from the sodium, potassium, ammonium, alkylamine (with 1-4 C atoms), guanidine or guanidine derivative salt of a halogenated acetic acid, a metal sulphate and thiourea or a derivative thereof of formula: wherein R and RSP1/SP are hydrogen, alkyl or alkenyl with 1 to 3 carbon atoms, hydroxyalkyl, acyl, phenyl, or benzoyl. The heat-sensitive salt is preferably sodium chloro-acetate and the metal sulphate is preferably magnesium, nickel or zinc sulphate. In the examples, an aqueous solution of the components is applied to a paper support, imagewise exposed and developed by heating to give a dye image.
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