Light-sensitive thermal developable diazotype sheets with imidazoles

Claim 1

A heat reactive diazotype sheet having a supporting substrate having at least two layers thereon, one of said layers comprising a heat-softenable binder material and an acid-stabilized light sensitive diazonium salt capable of reacting with an azo-coupler compound to form a dye, and the other of said layers comprising a heat-softenable binder material and an acid-neutralizer component capable of providing basic equivalents in an amount at least sufficient to neutralize said acid stabilization of said diazonium salt so as to provide a weakly basic environment for the diazonium salt in the sheet and to render said acid-stabilized diazonium salt reactive with said azo-coupler compound, and at least one of said layers containing an azo-coupler, said diazotype sheet being characterized by said acid-neutralizer component being comprised of at least 25% by weight imidazole acid-neutralizer compound is selected from the group consisting of 2-isopropyl imidazole, 2-phenyl imidazole, 2-benzyl imidazole, 4-phenyl imidazole, 4-methyl imidazole, 2,4-dimethyl imidazole, 2-phenyl-4-methyl imidazole, and 2,4,5-trimethyl imidazole.