Thermally developable diazotype copying materials

Claim 1

A thermally developable diazotype copying material having on one surface of a supporting sheet a two-layer light-sensitive coating comprising a diazonium compound, an azo coupling compound, a base generating agent, an acidic stabilizer and a compound for lowering the melting point of said azo coupling compound, in which a. the first layer consists of a binder resin containing a water-insoluble azo coupling compound uniformly dispersed in said binder resin in the form of fine particles and a compound for lowering the melting point of said azo coupling compound, said azo coupling compound being selected from the group consisting of 2,3-dihydroxy-naphthalene, 2,3-dihydroxy-naphthalene-6-sulfonamide-naphthalene, 2,3-dihydroxy-6-dihydroxyethyl-sulfonamide-naphthalene, 1-carboxy-2,3-dihydroxy-naphthalene, 1,4-dichloro-2,3-dihydroxy-naphthalene and 3,3-dihydroxy-2-naphthanilide; and said compound for lowering the melting point of said azo coupling compound being selected from the group consisting of guanidine-tartaric acid salt, amino-guanidine-hydrochloric acid salt, cyanoguanidine, ethylbiguanide-hydrochloric acid salt, dimethyl-biguanide-hydrochloric acid salt, 3-methoxy benzoguanidine, 1-butyl-3-nitroguanidine, 2-guanyl phthalic acid amide, acetamide, acrylamide, propionamide, butylamide and malonamide, the amount of said compound for lowering the melting point being in the range of 0.14 to 0.25 part by weight per one part by weight of said azo coupling compound and forming a eutectic with the azo coupling compound; b. a second layer containing a water-soluble, light-sensitive diazonium compound, a water-soluble, heat-fugitive, acidic salt as the base generating agent and an acidic stabilizer, said second layer overlying said first layer, said diazonium compound being selected from the group consisting of zinc chloride and cadmium chloride double salts of p-dimethyl-aminobEnzene diazonium chloride, p-diethyl-aminobenzene diazonium chloride, p-methyl-hydroxyethyl-aminobenzene diazonium chloride and p-ethylhydroxyethyl-aminobenzene diazonium chloride, and said heat-fugitive acidic salt being selected from the group consisting of alkali metal salts, ammonium salts, ethanolamine salts and isopropylamine salts of halogenoacetic acids, cyanoacetic acid and halogenomalonic acids.