The invention relates to novel photoinitators of formulae (I), (II), (III), (IV), (V) and (VI) wherein R1 and R2 are each independently of the other C1-C8alkyl; C1-C4alkyl substituted by OH, C1-C4alkoxy, —COO(C1-C8alkyl), (C1-C4alkyl)-COO—, —CN, benzyl, phenyl or by —N(R15)(R16); C3-C6alkerlyl, benzyl, —CH2—C6H4—(C1-C4alkyl) or phenyl; or R1 and R2 together are unbranched or branched C2-C9alkylene or C3-C6-oxa- or -azaalkylene; R3, R4, R5 and R6 are each independently of the others hydrogen, C1-C8alkyl, C3-C6alkenyl, benzyl, —CH2—C6H4—(C1-C4alkyl) or phenyl; R3 and R4 together and/or R5 and R6 together are unbranched or branched C2-C9alkylene; A is CI, Br, —O—R9, —N(R11)(R12) or —S—R18, A′ is —O—, —NH— or —NR11—; A″ is CI, Br, —O—R9, —N(R11)(R12) or —S—R18 or hydrogen, X is —O—R10 or —N(R13)(R14), n is an integer from 1 to 10, preferably an integer from 1 to 4, especially 1, 2 or 3; R7 is a linker; R8 is a bivalent C2-C3alkylele radical.