Photopolymerizable composition containing heterocyclic additives

A photopolymerizable composition comprising (1) a thermoplastic polymeric binder, (2) 10 to 500 parts by weight per 100 parts of the thermoplastic polymer binder of a non-gaseous ethylenically unsaturated compound which has at least two ethylenically unsaturated terminal groups and is capable of forming a polymer, (3) 0.1 to 20 parts by weight per 100 parts by weight of the non-gaseous ethylenically unsaturated compound of a photopolymerization initiator which is activated by actinic radiation, and (4) 0.001 to 10% by weight based on the total weight of the photopolymerizable composition of at least one heterocyclic compound represented by the Formulae (I) and (II) ##STR5## wherein R.sub.1 and R.sub.2 each represents a hydrogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, an aralkyl group, or a substituted or unsubstituted amino group;

• R.sub.3 and R.sub.4 each represents a hydrogen atom, an alkyl group, or an aryl group;
• R.sub.5 and R.sub.6 each represents a hydrogen atom, a substituted or unsubstituted alkyl group, an aryl group, or an aralkyl group, or R.sub.5 and R.sub.6 may be taken together with the adjacent nitrogen atom to form a pyrrolidone, piperidine, morpholine, or N-substituted piperazine ring;
• X represents an oxygen atom, a sulfur atom, a group ##STR6## wherein R.sub.3, R.sub.4, R.sub.5 and R.sub.6 are as defined above, or a group .dbd.N-R.sub.7, wherein R.sub.7 represents a hydrogen atom, an alkyl group, or an aryl group;
• and Y represents an oxygen atom or a sulfur atom.