UV-LED curable compositions and inks

1. 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;

S 1 and S 2 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).

2. The radiation curable composition according to claim 1 , wherein S 1 and S 2 represent hydrogen.

3. The radiation curable composition according to claim 1 , wherein R3 represents an alkyl group.

4. The radiation curable composition according to claim 2 , wherein R3 represents an alkyl group.

5. The radiation curable composition according to claim 3 , wherein R3 represents a branched alkyl group.

6. The radiation curable composition according to claim 1 , wherein the at least one photoinitiator is a diffusion hindered photoinitiator selected from the group consisting of a polymerizable photoinitiator, a multifunctional photoinitiator, a polymeric photoinitiator, and an oligomeric photoinitiator.

7. The radiation curable composition according to claim 6 , wherein the at least one photoinitiator according to Formula (I) comprises at least one polymerizable ethylenically unsaturated group.

8. The radiation curable composition according to claim 7 , wherein the at least one polymerizable ethylenically unsaturated group is selected from the group consisting of an acrylate, a methacrylate, an acrylamide a methacrylamide, a styrene, a maleimide, a vinyl ester, a vinyl ether, an allyl ether, and an allyl ester.

9. The radiation curable composition according to claim 8 , wherein the at least one polymerizable ethylenically unsaturated group is an acrylate.

10. The radiation curable composition according to claim 6 , wherein at least one of R1 to R3 is substituted with the at least one polymerizable ethylenically unsaturated group.

11. The radiation curable composition according to claim 6 , wherein one of the groups selected from R1 to R3, S 1 , and S 2 is linked to a polymer selected from the group consisting of a star polymer, a dendritic polymer, and a hyperbranched polymer.

12. The radiation curable composition according to claim 11 , wherein the hyperbranched polymer is a polyether or a polyester.

13. A radiation curable inkjet ink comprising:

the radiation curable composition according to claim 1 .

14. A radiation curable inkjet ink comprising:

the radiation curable composition according to claim 6 .

15. A method for preparing a radiation curable composition as defined by claim 1 comprising the steps of:

a) providing a composition containing monomers; and

b) adding to the composition the at least one photoinitiator according to Formula (I) and the at least one co-initiator selected from the group consisting of an aliphatic tertiary amine and a dialkyl aniline derivative.

16. A method for preparing a radiation curable composition as defined by claim 6 comprising the steps of:

a) providing a composition containing monomers; and

b) adding to the composition the at least one photoinitiator according to Formula (I) and the at least one co-initiator selected from the group consisting of an aliphatic tertiary amine and a dialkyl aniline derivative.