GB728205A - Photo-sensitive diazotype coated paper plate for photo-lithography - Google Patents

Abstract

728,205. Photo-lithographic diazotype paper plates. WARREN CO., S. D. Sept. 22, 1953 [May 22, 1953], No. 26099/53. Class 98 (2). Paper is provided with a hydrophilic calendered coating layer comprising insolubilized carboxyalkylhydroxyalkyl cellulose and a greater quantity of blanc fixe or titanium dioxide as pigment, and then an aryl amino phenylene diazonium sensitizing layer, which may be of the aldehyde condensate or diazo sulphonate type, and which is transformable by actinic light into an ink-receptive condition. A wood pulp paper containing clay filler, rosin size, alum and acidified melamine-formaldehyde condensate surface-sized with ammoniacal casein treated with formaldehyde may be used and for long printing runs should be waterproofed as with asphalt; but it is preferred to provide several coatings comprising (a) an anti-curling water-resistant backing coating for the non- printing side of the paper containing clay, ammonia solvated casein and dimethylol urea, (b) a first, water-impervious coating for the front of the paper containing clay, emulsion polymerized styrene-butadiene copolymer and also polystyrene, (c) a second, somewhat hydrophilic coating as of pigmented and insolubilized casein, soy or glue, but preferably one containing barium sulphate, casein and dimethylol urea on top of coating (b) and serving to avoid possible ink-acceptance by the latter; and (d) the particular coating of the invention of which a single example specifies titanium dioxide, sodium carboxymethylhydroxyethyl cellulose, melamine-formaldehyde condensate as insolubilizing ingredient, triethanolammonium chloride plasticizer, the sodium sulphate derivative of 7 - ethyl - 2 - methyl - undecanol - 4 as wetting agent, tributyl phosphate and Hcl to make pH 5.7. All of these coatings may be applied in aqueous dispersion by an air-knife coater and dried and calendered. The preferred sensitizer is made by action of sodium sulphite on the condensation product of the zinc chloride double salt of diazotized para-amino-diphenylamine with formaldehyde and is applied in aqueous solution over coating (d) and dried, and sensitive plates so made remain in condition after 12 months' storage. The plates may be exposed under a negative, wiped with oleic acid to intensify the ink-receptiveness of the exposed image, swabbed with water to remove unexposed areas and oleic acid lying thereon, wet out with aqueous glycerin and ammonium acid phosphate and then run in a rotary offset duplicator to give 15,000 or more prints. The carboxyalkylhydroxyalkyl celluloses may be made by the method of Specification 670,672, [Group IV (a)]. Other diazo sensitizers as exemplified in Specification 697,521 may be used.