Multifunctional cationic photoinitiators, their preparation and use

Compounds of formula (I):

• where:
• R1 represents a sulphur atom;
• R3, R4, R5 and R6 are independently selected from hydrogen atoms and substituents α, defined below;
• R8, R9, R10 and R11 are independently selected from hydrogen atoms, hydroxy groups, C1-C4 alkyl groups, and phenyl groups which are unsubstituted or substituted by at least one substituent selected from the group consisting of C1-C4 alkyl groups and C1-C4 alkoxy groups;
• or R9 and R11 are joined to form a fused ring system with the benzene rings to which they are attached;
• R7 represents a direct bond, an oxygen atom or a —CH2— group;
• p is 0 or 1;
• said substituents α are:
• a C1-C20 alkyl group, a C1-C20 alkoxy group, a C2-C20 alkenyl group, a halogen atom, a nitrile group, a hydroxyl group, a C6-C10 aryl group, a C7-C13 aralkyl group, a C6-C10 aryloxy group, a C7-C13 aralkyloxy group, a C8-C12 arylalkenyl group, a C3-C8 cycloalkyl group, a carboxy group, a C2-C7 carboxyalkoxy group, a C2-C7 alkoxycarbonyl group, a C7-C13 aryloxycarbonyl group, a C2-C7 alkylcarbonyloxy group, a C1-C6 alkanesulphonyl group, a C6-C10 arenesulphonyl group, a C1-C6 alkanoxyl group or a C7-C11 arylcarbonyl group;
• n is a number from 1 to 12;
• R12 represents a hydrogen atom, a methyl group or an ethyl group, and, when n is greater than 1, the groups or atoms represented by R12 may be the same as or different from each other;
• A represents a group of formula —[O(CHR13CHR14)a]y—, —[O(CH2)bCO]y—, or —[O(CH2)bCO](y−1)—[O(CHR13CHR14)a]—, where:
• one of R13 and R14 represents a hydrogen atom and the other represents a hydrogen atom, a methyl group or an ethyl group;
• a is a number from 1 to 2;
• b is a number from 4 to 5;
• Q is a residue of a polyhydroxy compound having from 2 to 6 hydroxy groups wherein Q is ethylene glycol, propylene glycol, butylene glycol, glycerol, trimethylolpropane, di-trimethylolpropane, pentaerythritol or di-pentaerythritol;
• x is a number greater than 1 but no greater than the number of available hydroxyl groups in Q;
• y is a number from 1 to 10;
• and
• X− represents an anion;
• and esters thereof.