Photopolymerizable element having initiator in adhesive layer

A photopolymerisable element which comprises a self-supporting plastics film or sheet having an adhesive layer superimposed upon at least one surface thereof and a photopolymerisable layer superimposed upon the adhesive layer, said adhesive layer having a thickness of from 0.05 to 20 .mu.m and being free of photopolymerisable component and comprising a non-photopolymerisable plastics binder and a photopolymerisation initiator comprising an admixture of:

• (i) a compound having the formula:
• ##STR8## wherein R.sub.1 and R.sub.2 are the same or different and are selected from hydrogen, or a lower alkyl group having up to 6 carbon atoms and R.sub.3 is the same as or different from R.sub.1 or R.sub.2 and is selected from hydrogen, a lower alkyl group having up to 6 carbon atoms, a partially or completely halogenated alkyl group having up to 6 carbon atoms or a group of the formula:
• ##STR9## in which R.sub.5 and R.sub.4 are the same or different and are selected from the same substituents as R.sub.1 and R.sub.2, said compound being present in an amount 0.01 to 2.0% by weight based upon the weight of the plastics binder;
• and
• (ii) another photopolymerisation initiator present in an amount 0.1 to 7% by weight based upon the weight of the plastics binder.