Patent ID: 7781148

Claim:
A positive-working imageable element comprising in order: (a) a substrate with a hydrophilic surface; (b) a first layer comprising a first polymer soluble or swellable in aqueous alkaline developer and insoluble in organic solvents of low polarity; and (c) a second layer comprising a second polymer soluble or swellable in aqueous alkaline developers, wherein the first polymer is different from the second polymer, wherein the second polymer comprises vinyl acetal repeating units and pendant acidic groups selected from the group consisting of —COOH, —SO 3 H, —PO 3 H 2 , —PO 4 H 2 , aromatic OH, and groups having acidic amide or imide groups, wherein the element optionally comprises at least one photothermal conversion material, and wherein the second layer accepts ink and is insoluble/impenetrable in/by an aqueous alkaline developer but is rendered soluble in or penetrable by the developer by IR radiation, and the second layer contains no crosslinkable enol ether or phenolic resin.