Positive-working light sensitive diazo materials with azo dye

摘要

A positive working light-sensitive composition comprises in admixture (a) a first component which is an azo dye formed by reacting a p-amino-benzene diazonium salt and a compound including the grouping <IMAGE> and (b) a second component which includes a o-quinone diazide and/or a diazonium compound and which, on exposure to light produces an acidic light decomposition product which is capable of reacting with the azo dye to produce a material having a color different to that of the azo dye. The composition exhibits a color change on exposure to light and is useful for the manufacture of light sensitive plates for use in lithographic printing plate production.