Patent GB-660088-A (GB)
Title: Improved diazotype photoprinting materials
IPC: G03C1/60
Filed: 1949-12-28
Abstract: 660,088. Photographic diazotype material. GENERAL ANILINE & FILM CORPORATION. - Dec. 28, 1949 [Dec. 31, 1948], No. 33131/49. Class 98 (ii). Photographic diazotype material has a light sensitive layer containing a light sensitive diazo compound and a water-soluble condensation product of formaldehyde with dicyandiamide and a salt of ammonia or a primary or secondary aromatic amine having at least one unoccupied position ortho or para to the amino group. The condensation product improves fastness of the image to water and also, where it is formed from an ammonium salt, improves the stability of the background to discoloration by light and air. Material having a support of paper, film, regenerated cellulose foil, organic cellulose derivatives, resins, metal, or glass and containing the azo coupling component in the light sensitive layer and developed after exposure by treatment with ammonia or with the vapour of a volatile basic organic nitrogen compound, or with an aqueous alkaline solution such as aqueous ammonium hydroxide, sodium carbonate, or trisodium phosphate is referred to. The incorporation of the azo coupling component in the developing solution, the use of diazosulphonates as the light sensitive compounds and the formation of images either by the self-coupling of residual undecomposed diazo compounds with their light decomposition products or by the oxidation of the phenolic compounds formed as light decomposition products of diazo compounds are also referred to. Condensation products may be formed by mixing dicyandiamide, alone or with thiourea, thiobiuret, thiocarbamylguanidine, or thiocarbamylurea, with aqueous formaldehyde and ammonium chloride, and heating, or by reacting an aromatic amine hydrochloride with aqueous formaldehyde at room temperature, and adding dicyandiamide, with or without thiourea, &c., as above and refluxing. The support may be precoated with an aqueous solution of the condensation product, and the diazotype sensitizing solution then applied, or the condensation product may be added to the sensitizing solution. In example 1, paper is coated with an aqueous solution of a condensation product from dicyandiamide, ammonium chloride, and formaldehyde, and, after drying, is coated with an aqueous solution of the zinc chloride double salt of p-(N-methyl : N-#-hydroxyethylamino)- benzenediazonium chloride, resorcinol, isopropanol, ethylene glycol, zinc chloride, thiourea, and citric acid. After exposure, the material is developed with ammonia vapour. In example 2, the procedure is similar, using ammonium resorcinol-4-sulphonate as coupler. In example 3, the procedure is similar, using as sensitizing solution an aqueous solution of the zinc chloride double salt of p-diethylaminobenzenediazonium chloride, ammonium resorcinol-4-sulphonate, isopropanol, thiourea, zinc chloride, ethylene glycol, and citric acid. In example 4, the procedure is similar to example 3, using as coupler disodium 2-hydroxynaphthalene - 3 : 6 - disulphonate, 1 - (3<SP>1</SP> - sulphophenyl) - 3 - methyl - 5 - pyrazolone, m - sulphoacetoacetanilide, 2 : 3 - dihydroxynaphthalene- 6 - sulphonic acid, or 4 : 6 - disulphoresorcinol. In example 5, paper is coated, at 50 C., with an aqueous solution of the zinc chloride double salt of p-diethylaminobenzenediazonium chloride (or the zinc chloride double salt of p-(N- methyl : N - # - hydroxyethylamino) - benzenediazonium chloride or of p-dimethylamino-ocarboxybenzenediazonium chloride), α-resorcylamide (or resorcinol), the condensation product of example 1, isopropanol, ethyleneglycol, citric acid, thiourea, zinc chloride, and saponin. In example 6, paper, precoated as in example 1, is coated with an aqueous solution of ammonium resorcinol-4-sulphonate, the zinc chloride double salt of 4-monoethylamino-3-methylbenzenediazonium chloride (or of 4-(N-ethyl : N- # - hydroxyethylamino) - 3 - methylbenzenediazonium chloride), ethanol, ethylene glycol, citric acid, thiourea, zinc chloride, and saponin, or with a similar solution in which the diazo compound is the zinc chloride double salt of 4-benzoylamino - 2:5 - diethoxybenzenediazonium chloride, the zinc chloride is omitted, and boric acid is added. In example 7, paper is precoated with a condensation product formed from aniline hydrochloride, dicyandiamide, and formaldehyde, and after drying, is coated with the sensitizing solution of example 3 containing the zinc chloride double salt of p-diethylaminobenzenediazonium chloride and ammonium resorcinol-4-sulphonate as the diazo compound and coupler. Alternatively, the zinc chloride double salt of N-methyl : N-#- hydroxyethylaminobenzenediazonium chloride and resorcinol may be used. The coupler may be omitted from the sensitizng solution and incorporated in a developing solution comprising an aqueous solution of sodium carbonate, trisodium phosphate, ammonium hydroxide, or triethanolamine. The effect of phenyl biguanide and decoxyphenyl biguanide is compared with that of the condensation products. Phloroglucinol or 2 3-dihydroxynaphthalene-6 :8-disulphonic acid may be used as the coupler.