Free-radical photoinitiators and uses of same in silicone compositions

A silicone composition C1 crosslinkable by exposure to radiation with a wavelength between 300 and 450 nm, comprising:

• at least one polyorganosiloxane A comprising at least one (meth)acrylate group bound to a silicon atom,
• at least one organohydrogenopolysiloxane H comprising at least two, and optionally at least three hydrogen atoms each bound to different silicon atoms, and
• at least one free-radical photoinitiator P of the following formula (I):
• in which:
• the symbol X is selected from the group consisting of:
• an oxygen atom, a sulfur atom, a CH2 group and a carbonyl radical,
• the symbols R2 and R4 are hydrogen atoms,
• the symbols R1 and R3, which may be identical or different, are selected from the group consisting of:
• a hydrogen atom, a hydroxyl and a group of formula —OZ with the symbol O being an oxygen atom and the symbol Z being selected from the group consisting of:
• a C1-C20, optionally C3-C20, alkyl group or C2-C20 alkenyl group,
• a group —(C═O)—R5, with the radical R5 being selected from the C1-C20 alkyl, C2-C20 alkenyl, C3-C20 cycloalkyl and C6-C12 aryl groups, and
• a group —Si(R6)3, where the groups R6, which may be identical or different, are selected from the C1-C20 alkyl, C2-C20 alkenyl, C3-C20 cycloalkyl, C6-C12 aryl, C1-C20 alkoxyl groups and the hydrogen atom,
• and with the condition that at least one of the substituents R1 or R3 is a hydroxyl or a group of formula —OZ.