abstract |
Compounds of the formula I ##STR1## in which at least one of the radicals R 1 , R 2 and R 3 is a substituted alkyl radical or cycloalkyl radical, or R 1 and R 2 together with the phosphorus atom form a monocyclic or tricyclic ring, are effective photoinitiators for the photopolymerization of ethylenically unsaturated compounds. |