Photopolymerizable composition with acylphosphine sulfide photoinitiator and method

A process for the preparation of a photopolymerizable composition which comprises:

• incorporating a photoinitiator into a photopolymerizable composition containing monomers having polymerizable C--C double bonds, said photoinitiator being an acylphosphine sulfide of the formula ##STR12## where R.sup.1 is straight-chain or branched alkyl of 1 to 6 carbon atoms, cyclohexyl or cyclopentyl, or a phenyl, naphthyl or O--, S-- or N--containing 5- or 6-membered heterocyclic radical which is unsubstituted or substituted by fluorine, chlorine, bromine, C.sub.1 -C.sub.4 --alkyl or C.sub.1 -C.sub.4 --alkoxy;
• R.sup.2 has the meanings of R.sup.1 and can be identical to or different from R.sup.1, or is alkoxy of 1 to 6 carbon atoms, phenoxy which is unsubstituted or substituted by chlorine, C.sub.1 -C.sub.6 --alkyl or C.sub.1 -C.sub.6 --alkoxy, or phenoxyalkyl, where alkyl is of 1 to 4 carbon atoms, or R.sup.1 and R.sup.2 are linked together to form a ring of 4 to 10 carbon atoms which is unsubstituted or can contain 1 to 6 further alkyl substituents, each of 1 to 4 carbon atoms, as well as 1 or 2 fused-on benzene rings;
• R.sup.3 is straight-chain or branched alkyl of 2 to 18 carbon atoms, a cycloaliphatic radical of 3 to 12 carbon atoms, mono-, di-, tri- or tetra-substituted phenyl or an unsubstituted or mono-, di-, tri- or tetra-substituted naphthyl, where the substituents can be identical or different and can be alkyl, alkylthio or alkoxy of 1 to 6 carbon atoms or chlorine, bromine or fluorine, or the group ##STR13## where R.sup.1 and R.sup.2 have the above meanings and X is unsubstituted or mono-, di-, tri- or tetra-substituted phenylene, where the substituents can be identical or different and can be alkyl, alkylthio or alkoxy of 1 to 6 carbon atoms or halogen of atomic weight of not more than 80, or X is an aliphatic or cycloaliphatic divalent radical of 2 to 6 carbon atoms;
• and where one or more of R.sup.1, R.sup.2 and R.sup.3 may be olefinically unsaturated, where R.sup.3 can also be methyl or phenyl.