Diazotype material

Abstract

Diazotype material having enhanced water-wet properties and especially suitable when imaged for being drawn or written upon, and for use as an intermediate original, is made of a support such as a transparent polymeric film carrying on one of its sides a light sensitive diazo layer formed of a dispersion of a light sensitive diazonium compound and a large amount of amorphous hydrated silica particles having a bound water content of at least 50% by weight in a polymeric binder consisting essentially of a 20 to 45% hydrolyzed polyvinyl acetate which preferably is a product of partial hydrolysis of a PVAC having in ethyl acetate at 20.degree. C. a Heoppler viscosity of 100 to 800 mPa.s. The weight ratio of the hydrated silica to the partially hydrated PVAC in the layer typically is in the range of 2:3 to 3:2. The support advantageously carries on its other side a light-pervious drafting layer formed of a dispersion of a silica filler in a partially hydrolyzed PVAC the same as that required for the diazo layer. Adherence of the specified layers and drafting properties of the material can be enhanced by coating on each side of the film, before applying those layers, a subbing layer formed of polymeric material, e.g. a mixture of a vinylidene chloride-acrylonitrile copolymer and a methylated melamine-formaldehyde resin, that is adherent to the film surface and contains a silica pigment which preferably is the same as that of the drafting layer. An advantageous one component diazotype material is obtained by incorporating a suitable diazonium salt in the diazo layer in the absence of an azo coupling agent, while such a two component diazotype material is obtained by making that layer to contain an azo coupling agent with a suitable diazonium salt.