Coumarin glyoxylates for LED photocuring

1. A photocurable composition comprising:

(a) from 50 to 99.9% by weight, based on the total content of the composition, excluding possible water and solvents, of at least one ethylenically unsaturated compound;

(b) from 0.1 to 35% by weight, based on the total content of the composition, excluding possible water and solvents, of at least one compound of formula (I)

wherein:

R 1 is a substituted or unsubstituted C1-C20 alkyl group or a substituted or unsubstituted C1-C50 alkyl group which is interrupted by one or more oxygens and may terminate with a hydroxy group or with an alkyl residue;

Cou is a coumarin group of formula:

wherein:

R 2 , R 3 , R 4 and R 5 are, independently of one another, hydrogen, substituted or

unsubstituted C1-C20 alkyl, -N(C1-C6 alkyl) 2 , piperidino, morpholino, piperazino, —O—R 7 or —S—

R 7 , where R 7 is hydrogen, substituted or unsubstituted C1-C20 alkyl, C2-C12 alkenyl, substituted

or unsubstituted aryl, heteroaryl or C5-C6 cycloalkyl;

R 6 is hydrogen, a hydroxy group or a C1-C4 alkyl group;

or Cou is a substituted or unsubstituted naphtho-coumarin group of formula:

wherein the star indicates the carbon atom which is bound to the keto group of formula (I).

2. The photocurable composition of claim 1 , wherein formula (I) R 1 is a substituted or unsubstituted C1-C20 alkyl group.

3. The photocurable composition of claim 1 wherein in formula (I) Cou is a coumarin group of formula (A) in which at least one of R 2 , R 3 , R 4 and R 5 is different from hydrogen.

4. The photocurable composition of claim 1 , wherein formula (I) Cou is (A) and R 6 is hydrogen or Cou is (C).

5. The photocurable composition of claim 1 , wherein in formula (I) Cou is a coumarin group of formula (A) in which R 6 is hydrogen,

at least two of R 2 , R 3 , R 4 and R 5 are —O—R 7 group and R 7 and R 1 are a C1-C20 alkyl group.

6. The photocurable composition of claim 1 , further comprising:

c) from 0.01 to 15% by weight of the total content of the composition, excluding possible water and solvents, of one or more photosensitizer; and/or

d) from 0.2 to 15% by weight of the total content of the composition, excluding possible water and solvents, of accelerators/coinitiators; and/or

e) from 0.5 to 15% by weight the total content of the composition, excluding possible water and solvents, one or more further photoinitiators; and/or

f) conventional additives.

7. A process for photocuring photopolymerizable compositions and inks, which process comprises the following steps:

(i) providing a photopolymerizable composition comprising:

compounds (a) and (b); as defined in claim 1 or

compounds (a), (b) as defined in claim 1 , and one or more components selected from

c) from 0.01 to 15% by weight of the total content of the composition, excluding possible water and solvents, of one or more photosensitizer; and/or

d) from 0.2 to 15% by weight of the total content of the composition, excluding possible water and solvents, of accelerators/coinitiators; and/or

e) from 0.5 to 15% by weight the total content of the composition, excluding possible water and solvents, one or more further photoinitiators; and/or

f) conventional additives;

(ii) photopolymerizing the composition of step (i) with an light source.

8. The process of claim 7 , wherein light source comprises UV light in at least one of the UVA, UVB and UVC ranges.

9. The process of claim 7 , wherein light source is a LED source emitting in the range from 350 to 420 nm.

10. The process of claim 7 , further comprising the step of applying said photopolymerizable composition to a substrate prior to photopolymerizing it.

11. The photocurable composition according to claim 1 , comprising from 70 to 98.9% by weight, based on the total content of the composition, excluding water and solvents of at least one ethylenically unsaturated compound.

12. The photocurable composition according to claim 1 , comprising from 0.1 to 20% by weight, based on the total content of the composition, excluding water and solvents of at least one compound of formula (I)

13. The photocurable composition according to claim 1 , comprising from 0.2 to 15% by weight, based on the total content of the composition, excluding water and solvents of at least one compound of formula (I)

14. A compound of formula (Ia):

wherein:

R 1 is a substituted or unsubstituted C1-C20 alkyl group or a substituted or unsubstituted C1-C50 alkyl group which is interrupted by one or more oxygens and may terminate with a hydroxy group or with an alkyl residue;

Cou is a coumarin group of formula:

wherein:

R 2 , R 3 , R 4 and R 5 are, independently of one another, hydrogen, substituted or unsubstituted C1-C20 alkyl, -N(C1-C6 alkyl) 2 , piperidino, morpholino, piperazino, —O—R 7 or —S—R 7 , where R 7 is hydrogen, substituted or unsubstituted C1-C20 alkyl, C2-C12 alkenyl, substituted or unsubstituted aryl, heteroaryl or C5-C6 cycloalkyl;

R 6 is hydrogen, a hydroxy group or a C1-C4 alkyl group;

or Cou is a substituted or unsubstituted naphtho-coumarin group of formula:

wherein the star indicates the carbon atom which is bound to the keto group of formula (Ia);

provided that:

when R 1 is methyl, than at least one of R 2 , R 3 , R 4 , R 5 and R 6 is different from hydrogen;

when R 1 is methyl or ethyl, than R 4 is different from methyl;

when R 1 is methyl, than R 6 is not hydroxy;

when R 1 is methyl or ethyl, than R 2 is not methoxy; and

when R 1 is methyl or ethyl, than R 2 and R 4 are not both tert-butyl.

15. The compound of claim 14 , wherein in formula (Ia) R 1 is a substituted or unsubstituted C1-C20 alkyl group.

16. The compound of claim 14 , wherein in formula (Ia) Cou is a coumarin group of formula (A) in which R 3 is substituted or unsubstituted C1-C20 alkyl, —O—R 7 or —S—R 7 , where C1-C20 alkyl.

17. The compound of claim 14 , wherein in formula (Ia) Cou is (A) and R 6 is hydrogen or Cou is (C).

18. The compound of claim 14 ,

wherein in formula (Ia) Cou is a coumarin group of formula (A) in which R 6 is hydrogen, at least two of R 2 , R 3 , R 4 and R 5 are —O—R 7 group and R 7 and R 1 are a C1-C20 alkyl group.