Abstract: An alkali soluble resin is disclosed comprising a first monomeric unit including at least one sulfonamide group and a second monomeric unit derived from the monomer according to the following structure (I) wherein R1 represents a structural moiety comprising an ethylenically unsaturated polymerisable group; R2, R3 and R4 independently represent hydrogen, an optionally substituted alkyl, alkenyl, alkynyl, alkaryl, aralkyl, aryl or heteroaryl group or, the necessary atoms to form a five to eight membered ring.

Abstract: A lithographic printing plate precursor is disclosed which comprises a support having a hydrophilic surface or which is provided with a hydrophilic layer, and a coating thereon, said coating comprising an IR absorbing agent and a contrast enhancing compound, characterized in that said contrast enhancing compound has the structure of formula (I). The printing plate comprising the contrast enhancing compound improves the thermoresponsivity of the coating and is capable of improving the resistance of the coating in the non-exposed areas against the alkaline developer.