Photocurable compositions with acylphosphine oxide photoinitiator

A process for the preparation of photopolymerizable surface-coatings, finishes and printing inks wherein an acylphosphine oxide compound of the general formula ##STR9## where R.sup.1 is straight-chain or branched alkyl of 1 to 6 carbon atoms, cyclohexyl, cyclopentyl, phenyl or naphthyl which is unsubstituted or substituted by halogen, alkyl of 1 to 6 carbon atoms, or an S-containing or N-containing five-membered or six-membered heterocyclic radical selected from pyridyl or thienyl, R.sup.2 has one of the meanings of R.sup.1 with the proviso that R.sup.1 and R.sup.2 may be identical or different, or R.sup.2 is alkoxy of 1 to 6 carbon atoms, phenoxy, methylphenoxy or benzyloxy, or R.sup.1 and R.sup.2 may be joined together to form a five- or six-membered P-containing ring, and R.sup.3 is an at least disubstituted phenyl, pyridyl, furyl or thienyl radical which carries, at least at the two carbon atoms adjacent to the linkage point of the carbonyl group, the substituents A and B, which may be identical or different, and each of which is alkyl, alkoxy or alkylthio of 1 to 6 carbon atoms, cycloalkyl of 5 to 7 carbon atoms, phenyl or halogen, or R.sup.3 is .alpha.-naphthyl subsituted by A and B at least in the 2- and 8-positions or is .alpha.-naphthyl substituted by A and B at least in the 1 and 3 positions, is mixed as a photoinitiator in a concentration of from 0.001% to 20% by weight of the total amount of the photopolymerizable mixture with at least one photopolymerizable material containing at least one carbon-carbon polymerizable double bond and at least one aryl, carbonyl, amino, amido, ester, carboxyl or cyanide group or halogen atom or additional carbon-carbon double bond or carbon to carbon triple bond in photopolymerization activating relationship to the said carbon-carbon polymerizable double bond.