The invention relates to novel photoinitators of formulae (I), (II), (III), (IV), (V) and (VI) wherein R.sub.1 and R.sub.2 are each independently of the other C.sub.1-C.sub.8alkyl; C.sub.1-C.sub.4alkyl substituted by OH, C.sub.1-C.sub.4alkoxy, --COO(C.sub.1-C.sub.8alkyl), (C.sub.1-C.sub.4alkyl)-COO--, --CN, benzyl, phenyl or by --N(R.sub.15)(R.sub.16); C.sub.3-C.sub.6alkerlyl, benzyl, --CH.sub.2--C.sub.6H.sub.4--(C.sub.1-C.sub.4alkyl) or phenyl; or R.sub.1 and R.sub.2 together are unbranched or branched C.sub.2-C.sub.9alkylene or C.sub.3-C.sub.6-oxa- or -azaalkylene; R.sub.3, R.sub.4, R.sub.5 and R.sub.6 are each independently of the others hydrogen, C.sub.1-C.sub.8alkyl, C.sub.3-C.sub.6alkenyl, benzyl, --CH.sub.2--C.sub.6H.sub.4--(C.sub.1-C.sub.4alkyl) or phenyl; R.sub.3 and R.sub.4 together and/or R.sub.5 and R.sub.6 together are unbranched or branched C.sub.2-C.sub.9alkylene; A is CI, Br, --O--R.sub.9, --N(R.sub.11)(R.sub.12) or --S--R.sub.18, A' is --O--, --NH-- or --NR.sub.11--; A'' is CI, Br, --O--R.sub.9, --N(R.sub.11)(R.sub.12) or --S--R.sub.18 or hydrogen, X is --O--R.sub.10 or --N(R.sub.13)(R.sub.14), n is an integer from 1 to 10, preferably an integer from 1 to 4, especially 1, 2 or 3; R.sub.7 is a linker; R.sub.8 is a bivalent C.sub.2-C.sub.3alkylele radical. ##STR00001##