GB1469941A - Diazotype reproduction layer - Google Patents

Abstract

1469941 Diazotype process ANDREWS PAPER & CHEMICAL CO Inc 29 March 1974 [10 April 1973] 14037/74 Heading G2C A diazotype reproduction process comprises imagewise exposure of a diazotype reproduction sheet which has, on a base sheet 10, a surface coating 14 of diazotype components formed in a matrix of spherical particles 12 of polystyrene of diameter of from 0.1 to 1 micron and development of the image thus formed. The surface coating may include a development aid, e.g. urea, that releases ammonia on heating. The surface can be rendered water fast and water repellent by treatment with a solvent or solvent mixture which swells or partially dissolves the spherical particles without dissolving any of the diazotype components. A similar effect can be achieved by partial fusion of the spherical particles. The particles may be applied as an undercoat, the diazotype solution being applied in a second operation or a mixture of particles and diazotype solution can be applied in a single coating operation. The particles can be held together and affixed to the support by a bonding aid such as polyvinyl acetate or copolymer lattices and/or hydrophilic colloids, or by heating the particles or by applying solvent. Other resin dispersions e.g. vinyl acetate, vinyl chloride, vinylidene chloride, styrene, acrylic, styrenebutadiene or ethylene polymers or copolymers, hydrophilic colloids, starch particles, mineral pigments and organic plasticizers may be admixed. Base paper coated with the diazotype composition admixed with the polystyrene particles may be coated on the back with the particles with or without an additional binder. After drying a treatment with a solvent gives a water resistant material. Transfer to a non-treated receiver sheet, e.g. of bond paper, can be effected of the developed image layer. The non-developed layer can also be transferred to a transfer sheet which can be treated before or after transfer to produce image development. The process can also be applied to multicolour diazo reproduction. A solvent treatment is applied to render the surface of the material non- water receptive. After the first printing and development in one colour the developed layer is resensitized with the diazo components for another colour, the solvent treatment is repeated and a second printing and development are carried out, the process being repeated to achieve the required number of colours.