US Patent 7612122 Piperazino based photoinitiators

Compounds of formula (I): [where: the substituents R1 are individually selected from C1-C10 alkyl groups and optionally substituted benzyl groups; the substituents R2 are individually selected from alkyl groups or, together with the nitrogen atom to which they are attached, represent a nitrogen-containing heterocyclic group; Z is selected from C6-C10 arylene groups and groups of formula —(CHR3)n—, where R3 is hydrogen, hydroxy or a C1-C4 alkyl group, and n is 0 to 6; Y is carbonyl or —CH2—; Q is a residue of a mono- or poly-hydroxy compound; and x is 1 to 6; and esters thereof] are useful as multi-functional photoinitiators for use in coating compositions to be cured by radiant energy.