Image forming layer

An image forming layer which comprises a polymer capable of being decarboxylated by exposure to light, said polymer being a copolymer of at least one carboxyl group-containing monomer represented by the following general formula (VI):

• CH.sub.2 .dbd.C(E)--Z--(Y).sub.1 --X--(CH.sub.2).sub.k --COOT(VI)
• wherein E represents CH.sub.3 or hydrogen atom, Z represents a bridging group consisting of at least one bond selected from an alkylene bond, an arylene bond, an ether bond, an amide bond, an ester bond or an urethane bond, X represents sulfur atom, oxygen atom or N--R where R represents a hydrogen atom, phenyl or C.sub.1 to C.sub.10 alkyl group, Y represents an alkylene group, an arylene group, an aralkylene group or a divalent heterocyclic ring, and T represents a hydrogen atom, an alkali metal, an alkaline earth metal or HN(R.sup.1)(R.sup.2)(R.sup.3) where R.sup.1, R.sup.2 and R.sup.3 independently represent a hydrogen atom, an alkyl group or an aryl group or R.sup.1, R.sup.2 and R.sup.3 can join together to form a ring, k represents 0 or 1 and 1 represents 0 or 1;
• with at least one sensitizer moiety-containing monomer represented by the following general formula:
• CH.sub.2 .dbd.C(E)--Z--S
• wherein E and Z have the same meanings defined in the general formula (VI) and S represents a sensitizer moiety which absorbs an ultraviolet ray of 320 nm or higher.