Polymerizable type II photoinitiators and curable compositions

1. A polymerizable Type II photoinitiator according to Formula (I):

wherein:

A represents a Norrish Type II initiating group;

L represents a divalent linking group positioning the Norrish Type II initiating group A and the CR2R3-group in a 1-5 to a 1-8 position wherein position 1 is defined as the first atom in the aromatic or alicyclic ring of A to which L is covalently bonded and the position 5 to 8 is defined as the carbon atom of the CR2R3-group to which L is covalently bonded, with the proviso that L does not contain an amine;

R1 represents an optionally substituted group selected from the group consisting of an alkyl group, an alkenyl group, an alkynyl group, an aralkyl group, an alkaryl group, an aryl group, and a heteroaryl group;

R2 to R6 each independently represent a hydrogen or an optionally substituted group selected from the group consisting of an alkyl group, an alkenyl group, an alkynyl group, an aralkyl group, an alkaryl group, an aryl group, and a heteroaryl group, with the proviso that at least one of R2 to R6 represents a hydrogen;

any two or three groups of the group selected from R1 to R6 and L may represent the necessary atoms to form a five to eight membered ring; and

with the proviso that at least one of L, R1 to R6, and A is substituted with at least one ethylenically unsaturated polymerizable group selected from the group consisting of an acrylate group, a methacrylate group, an acrylamide group, a methacrylamide group, a styrene group, a vinyl ether group, an allyl ether group, an allyl ester group, a vinyl ester group, a succinate group, a maleate group, and a maleimide group.

2. A polymerizable Type II photoinitiator according to Formula (I):

wherein:

A represents a Norrish Type II initiating group;

L represents a divalent linking group positioning the Norrish Type II initiating group A and the CR2R3-group in a 1-5 to a 1-8 position wherein position 1 is defined as the first atom in the aromatic or alicyclic ring of A to which L is covalently bonded and the position 5 to 8 is defined as the carbon atom of the CR2R3-group to which L is covalently bonded, with the proviso that L does not contain an amine;

R1 represents an optionally substituted group selected from the group consisting of an alkyl group, an alkenyl group, an alkynyl group, an aralkyl group, an alkaryl group, an aryl group, and a heteroaryl group;

R2 to R6 each independently represent a hydrogen or an optionally substituted group selected from the group consisting of an alkyl group, an alkenyl group, an alkynyl group, an aralkyl group, an alkaryl group, an aryl group, and a heteroaryl group, with the proviso that at least one of R2 to R6 represents a hydrogen;

any two or three groups of the group selected from R1 to R6 and L may represent the necessary atoms to form a five to eight membered ring; and

with the proviso that at least one of L, R1 to R6, and A is substituted with at least one ethylenically unsaturated polymerizable group according to Formula (II):

wherein

X represents a functional group selected from the group consisting of OR7, S(O) n R8, and NR9R10;

Y represents a functional group selected from the group consisting of OR11 and NR12R13;

R8 to R10 represent an optionally substituted group selected from the group consisting of an alkyl group, an alkenyl group, an alkynyl group, an aralkyl group, an alkaryl group, an aryl group, and a heteroaryl group;

R7 and R11 to R13 represent a hydrogen or an optionally substituted group selected from the group consisting of an alkyl group, an alkenyl group, an alkynyl group, an aralkyl group, an alkaryl group, an aryl group, and a heteroaryl group; and

R9 and R10 and R12 and R13 may represent the necessary atoms to form a five to eight membered ring.

3. The polymerizable Type II photoinitiator according to claim 1 , wherein the Norrish Type II initiating group A is selected from the group consisting of a substituted or unsubstituted benzophenone and a substituted or unsubstituted thioxanthone.

4. The polymerizable Type II photoinitiator according to claim 1 , wherein R1 is selected from the group consisting of a substituted or unsubstituted alkyl group and a substituted or unsubstituted aryl group.

5. The polymerizable Type II photoinitiator according to claim 4 , wherein R1 represents an aryl group according to Formula (III):

wherein the dotted line represents a chemical bond to the nitrogen atom in Formula (I) and E represents a group selected from the group consisting of an ester, an aldehyde, a ketone, and an amide.

6. The polymerizable Type II photoinitiator according to claim 5 , wherein the group E represents an ester group.

7. A polymerizable Type II photoinitiator according to Formula (I):

wherein:

A represents a Norrish Type II initiating group;

L represents a divalent linking group represented by the group —O—(CH2)n— with n representing an integer having a value of 3;

R1 represents an optionally substituted group selected from the group consisting of an alkyl group, an alkenyl group, an alkynyl group, an aralkyl group, an alkaryl group, an aryl group, and a heteroaryl group;

R2 to R6 each independently represent a hydrogen or an optionally substituted group selected from the group consisting of an alkyl group, an alkenyl group, an alkynyl group, an aralkyl group, an alkaryl group, an aryl group, and a heteroaryl group, with the proviso that at least one of R2 to R6 represents a hydrogen;

any two or three groups of the group selected from R1 to R6 and L may represent the necessary atoms to form a five to eight membered ring; and

with the proviso that at least one of L, R1 to R6, and A is substituted with at least one ethylenically unsaturated polymerizable group selected from the group consisting of an acrylate group, a methacrylate group, an acrylamide group, a methacrylamide group, a styrene group, a vinyl ether group, an allyl ether group, an allyl ester group, a vinyl ester group, a succinate group, a maleate group, and a maleimide group.

8. A radiation curable composition comprising:

the polymerizable Type II photoinitiator according to claim 1 .

9. The radiation curable composition according to claim 8 , wherein the composition includes a colorant.

10. The radiation curable composition according to claim 8 , wherein the radiation curable composition is a radiation curable inkjet ink.

11. A radiation curable ink set comprising:

at least two of the radiation curable compositions according to claim 8 .

12. An inkjet printing method comprising the steps of:

providing the radiation curable composition according to claim 8 ; and

at least partially curing the radiation curable composition.

13. The inkjet printing method according to claim 12 , further comprising the steps of:

applying the radiation curable composition to a substrate by flexographic printing; and

printing an inkjet ink upon the at least partially cured radiation curable composition.

14. The inkjet printing method according to claim 12 , further comprising the step of:

jetting the radiation curable composition upon a substrate.

15. The polymerizable Type II photoinitiator according to claim 1 , wherein the at least one ethylenically unsaturated polymerizable group is an acrylate group.

16. The polymerizable Type II photoinitiator according to claim 3 , wherein the at least one ethylenically unsaturated polymerizable group is an acrylate group.

17. The polymerizable Type II photoinitiator according to claim 5 , wherein the at least one ethylenically unsaturated polymerizable group is an acrylate group.

18. The polymerizable Type II photoinitiator according to claim 7 , wherein the at least one ethylenically unsaturated polymerizable group is an acrylate group.