GB970236A - Planographic printing plate and processes - Google Patents

Abstract

970,236. Printing processes. COLUMBIA RIBBON & CARBON MANUFACTURING CO. Inc. June 6, 1963 [June 13, 1962], No. 22492/63. Heading B6C. [Also in Division G2] A heat-imageable planographic printing plate having a flexible foundation sheet is produced by applying to the sheet an emulsified wax composition, evaporating the composition to form a heat-meltable oleophilic layer of discrete wax particles, and applying over the layer an hydrophilic coating which is capable of being penetrated and rendered oleophilic by the wax layer when the latter is melted under the effect of heat. The wax particles provide holding power for the hydrophilic coating. To provide on the plate the design which is to be printed, a heated stylus or heated type bars may be employed which melt the wax layer at the required places causing it to penetrate through the hydrophilic layer at those places and form an oleophilic design on the surface. Alternatively, an original sheet containing the design in an infra-red radiation-absorbing material is laid on the plate and is subjected to infra-red radiation. The foundation sheet is wet-strength paper; the oleophilic layer may be based upon hard wax such as carnauba wax, curicury wax, Be square wax, montan wax &c. or mixtures thereof, and is emulsified in a major amount of water. A specific example comprises in parts by weight Ouricury wax 4 parts, Be square wax 4 parts, Oleic acid 6 parts, potassium hydroxide 8 parts and water 100 parts. The layer thickness varies with the thickness of the hydrophilic coating and may be 0.0003-0.0005 inch, and the layer has a melting point of 120-200‹ F. Hydrophilic colloid and like binder materials such as polyvinyl alcohol, carboxymethyl cellulose, casein, gelatin and sodium alginate together with a filler such as clay, attapulgite, talc blanc fixed or titanium oxide may be used for the hydrophilic layer, the proportion of filler to binder ranging from 3 to 1 to 7 to 1 for thickness of coatings of 0.00005- 0.0002 inch. The coating may be insolubilized by the use of a salt,' aldehyde or like curing agent. A specific example given comprises sodium carboxymethyl cellulose 2 gms., 5% ammoniacal copper sulphate 40 c.c., chromium trioxide 0.5 gms., ferric ammonium citrate 1.0 gm., water 90 c.c. and clay 8 gms.