Patent ID: 7914966

Claim:
A radiation-sensitive positive working element comprising (a) a substrate with a hydrophilic surface, (b) a first layer on the hydrophilic surface of the substrate and (c) a top layer, wherein the first layer comprises a modified polymer that is soluble in aqueous alkaline developer and the solubility is not changed by IR radiation and wherein the top layer is insoluble in or impenetrable by aqueous alkaline developer, but is rendered soluble in or penetrable by aqueous alkaline developer by IR radiation, wherein the modified polymer is a reaction product of (a) a polymer with —COOH, —SO 3 H, —PO 3 H 2 and/or —PO 4 H 2 in the side chains, wherein the polymer is soluble in aqueous alkaline solutions and the solubility is not changed by IR radiation, with (b) a salt with an inorganic or organic cation, to replace at least one hydrogen atom with said inorganic or organic cation, wherein the modified polymer is soluble in aqueous alkaline solutions and the solubility is not changed by IR radiation, said polymer (a) being selected from the group consisting of: acidic polyvinyl acetals, (meth)acrylic acid polymers and copolymers, derivatives of methylvinylether/maleic acid anhydride copolymers, derivatives of styrene/maleic acid anhydride copolymers comprising an N-substituted cyclic imide unit, copolymers comprising a monomer in polymerized form that contains a urea group in its side chain, and mixtures of any of these classes of polymers.