Light sensitive composition, presensitized lithographic printing plate and image forming method employing the printing plate

A light sensitive composition comprising

• (a) a vinyl polymer having a unit represented by the following Formula (1) and a carboxyl group, (b) a monomer, oligomer or polymer containing at least one polymerizable double bond in its molecule, (c) a photopolymerization initiator and (d) a polymerization inhibitor, which is a hindered phenol having an acroyl, methacroyl, vinyl or allyl group, ##STR11## wherein R.sup.1 and R.sup.2 independently represent a hydrogen atom or a methyl group;
• R.sup.3 represents a hydrogen atom, an alkyl group or an aryl group, provided that when R.sup.2 is a methyl group, R.sup.3 is a hydrogen atom;
• and L represents a divalent linkage group selected from the group consisting of --CH.sub.2 --CH(OH)CH.sub.2 --O--, --OCH.sub.2 --CH(OH)CH.sub.2 --OCO--, --OCH.sub.2 CH.sub.2 --OCONH--R.sup.4 --NHCOOCH.sub.2 -- in which R.sup.4 represents p-phenylene, --OCH.sub.2 CH.sub.2 OCOCH.sub.2 CH.sub.2 COOCH.sub.2 -- or --OCH.sub.2 CH.sub.2 OCO--R.sup.5 --COOCH.sub.2 -- in which R.sup.5 represents o-phenylene.