Patent ID: 7029824

Claim:
A positive working thermal imaging assembly comprising A—a substrate; and B—a thermally sensitive imaging element of a composite layer structure comprising a first layer on the substrate of a novolac resin soluble in an aqueous alkali solution, optionally containing a compound that absorbs and converts light to heat and/or a colored dye or pigment; said first layer being converted on a surface thereof by treatment with a solution at an elevated temperature that contains an active compound capable of rendering said novolac resin less soluble in an aqueous alkali developer at the point of contact; the first layer being oleophilic, wherein the first layer is treated by contact with said solution for 1 to 120 seconds at a temperature of from 50 to 120° C., and wherein said active compound is a polymeric amine; optionally, a first intermediate layer between the substrate and the first layer of a polymeric material which is soluble or dispersible in an aqueous solution and that optionally contains a compound that absorbs and converts light or radiation to heat and/or a colored dye or pigment coated from a solvent that does not substantially dissolve the first layer; and optionally, a third or top layer over the converted first layer and composed of a polymeric material which is soluble or dispersible in an aqueous solution and that optionally contains a compound that absorbs and converts light or radiation to heat and/or a colored dye or pigment; the first intermediate layer and the third layer being applied with a solvent that does not substantially dissolve the converted first layer.