UV-LED curable compositions and inks

A free radical radiation curable composition for UV LED curing comprising:

• at least one co-initiator selected from the group consisting of an aliphatic tertiary amine and a dialkyl aniline derivative;
• and
• at least one photoinitiator according to Formula (I):
• wherein,
• R1 and R2 are independently selected from the group consisting of an aromatic or heteroaromatic group and a substituent according to Formula (II):
• R3 is selected from the group consisting of hydrogen, an alkyl group, an alkenyl group, an alkynyl group, an aralkyl group, an alkaryl group, and an aryl or heteroaryl group;
• S1 and S2 are independently selected from the group consisting of hydrogen, an alkyl group, an alkenyl group, an alkynyl group, an aralkyl group, an alkaryl group, an aryl group, a heteroaryl group, a halogen, OH, an alkoxy group, a thiol group, a thioalkoxy group, an ester group, an amide group, an amine group, and a carboxylic acid group;
• Y represents O or NR5;
• R4 and R5 are selected from the group consisting of hydrogen, an alkyl group, an alkenyl group, an alkynyl group, an aralkyl group, an alkaryl group, and an aryl or heteroaryl group;
• n and m independently represent an integer from 1 to 3;
• and
• X and Z represent O;
• and
• at least one of R1 and R2 is represented by a substituent according to Formula (II).