Patent ID: 6849668

Claim:
A multi-functional photoinitiator of formula (I) R 1 m —Q— ( A 1 —PI ) n (I) wherein Q is a heteroatom selected from Si, Ti, Zr and Sn or any two independently selected such heteroatoms linked by a covalent bond or by a C 1-16 (preferably C 1-9 ) alkylene group; n is at least 2 and n+m=the functionality of Q; each R 1 is the same or different and is a non-photoinitiator group; each group PI is the same or different and is a photoinitiator group; and each —A 1 — is the same or different and is selected from linking groups of formula —(A 2 ) p —Z— wherein p has an average of from 1 to 10, preferably from 3 to 5 and the groups —A 2 — are either (a) each independently selected from C 2-4 alkyleneoxy groups; or (b) each independently selected from groups of formula —O—(CH 2 ) q CO— wherein q is from 3 to 5, and Z is selected from —O—, —S— and —NR 6 — where R 6 is C 1-4 alkyl.