Ink compositions for ink jet printing

Abstract

radiation curable ink compositions for ink jet contain radiation curable monomers containing vinylether and acrylate functions.

Description

This application 2% 5% wt of NMDA, 2% wt of ethanol and 10% wt of Quantacure ITX. Finally, the Radcure DPGDA or monomer of the invention was added to the CN501. The resulting mixture was stirred for a couple of minutes until the added diluent was completely dissolved. As a third respectively a fourth ink component the liquid NMDA respectively the ethanol was added while stirring for about five minutes to complete the solution step. As the last compound the solid photoinitiator Quantacure ITX was added. The resulting mixture was stirred for about 1 hour in order to completely dissolve the ITX.

TABLE 2
ink composition of non-colored inks of the invention for
free radical polymerization
	Monomer of the
	invention		wt %
Ink	(chem.		wt	wt %	wt %	Quantacure
number	nature)	wt %	% CN501	NMDA	ethanol	ITX
1-0	**(compar	33.2	49.8	5.0	2.0	10.0
	ative):
	DPGDA
1-1	1.1	33.2	49.8	5.0	2.0	10.0
1-2	1.1	41.5	41.5	5.0	2.0	10.0
1-3	1.2	33.2	49.8	5.0	2.0	10.0
1-4	1.2	41.5	41.5	5.0	2.0	10.0
1-5	1.4	33.2	49.8	5.0	2.0	10.0
1-6	1.4	41.5	41.5	5.0	2.0	10.0
1-7	1.5	33.2	49.8	5.0	2.0	10.0
1-8	1.5	41.5	41.5	5.0	2.0	10.0

After measuring viscosities, each ink composition was coated repeatedly on a clear unsubbed 100 μm thick polyester film, using a bar coater and a 10 μm wired bar. The coated films were placed on a conveyer belt and transported underneath a UV lamp. A Fusion DRSE-120 conveyer, equipped with a Fusion VPS/I600 lamp (H bulb), powered at 60% and 100% of the nominal maximum input power, was used to cure the coated inks. Different transportation speeds are used for the same coated ink composition in order to determine the maximum speed at which curing was possible. The lowest belt speed that could be used with the conveyer was 9 m/min, the highest was 70 m/min. By means of a scratch test with a cotton bud, the curing was visually evaluated: when the coating did not remain visually unchanged after scratching, the curing was not complete. The highest curing speed was the highest transportation speed at which the coating remained unchanged after scratching. This maximum speed is indicated in table 3, together with the viscosities of the corresponding ink.

TABLE 3
free radical polymerization of ink compositions with the monomers
of the invention
	Maximum curing speed (m/min) when
	Power is:
	Viscosity		100%
Ink number	(mPasec)	60% of maximum P	(= maximum P)
1-0 **(compara.)	24	50	70
1-1	10	9	12
1-2	7	5	12
1-3	12	9	15
1-4	10	9	15
1-5	13	12	20
1-6	8	9	15
1-7	12	12	20
1-8	11	9	12

As one can see from table 3, all inks wherein the comparative DPGDA was replaced by a monomer of the invention showed a much lower viscosity of the radiation curable ink, and curing of these inks was still possible using conventional UV curing systems. The lower viscosity is of utmost importance if one wants to use these inks in ink jet printheads.

Example 2

Free Radical Polymerization of Black Inks

The general composition of the black colored radiation curable inks of the invention was:

• Ultraviolet polymerizing oligomer CN 501 (amine modified polyether acrylate, Cray Valley)
• Monomer of the invention (see table 4),
• N-methyl diethanol amine (NMDA as co-initiator or synergist Ethanol
• 2-isopropylthioxanthone (Quantacure ITX, Rahn AG)
• Special black 250 (Degussa)
• Solpserse 24000SC (Zeneca)

Substituting the monomer of the invention by the difunctional monomer dipropylene glycol diacrylate (Radcure DPGDA, UCB) as comparative diluent gave rise to a comparative ink composition. All inks were prepared on a basis of a total final weight of 20 g. All ink compositions are indicated in table 3 in weight percentage: they all contained 2% 5% wt of NMDA, 2% wt of ethanol and 10% wt of Quantacure ITX.

Firstly, the Radcure DPGDA or monomer of the invention was added to the CN501. The resulting mixture was stirred for a couple of minutes until the added diluent was completely dissolved. As a third ink component—10 wt % admixture of Solsperse 24000SC in CN501 —was added while stirring for about five minutes to complete the solution step. After further adding the Special Black, the resulting ink was milled for 24 hour in a ball mill. Furtheron the NMDA and the ethanol were added, and the resulting mixture was stirred for about 5 minutes. As the last compound the solid photoinitiator Quantacure ITX was added. The resulting mixture was stirred for about 1 hour in order to completely dissolve the ITX. The ink compositions that have been tested are given in table 4.

TABLE 4
ink composition of black colored inks of the invention for
free radical polymerization
	Monomer of the			wt %
	invention		wt %	Special	wt %
Ink	(chem.		wt	wt %	wt %	solsperse	Black	Quantacure
number	nature)	wt %	% CN501	NMDA	ethanol	24000CS	250	ITX
2-0	**(compar	28.2	49.05	5.0	2.0	0.75	5.0	10.0
	ative):
	DPGDA
2-1	1.1	28.2	49.05	5.0	2.0	0.75	5.0	10.0
2-2	1.2	28.2	49.05	5.0	2.0	0.75	5.0	10.0
2-3	1.4	28.2	49.05	5.0	2.0	0.75	5.0	10.0
2-4	1.5	28.2	49.05	5.0	2.0	0.75	5.0	10.0

After the viscosities had been measured, each ink composition was treated similarly as the inks described in example 1: barcoating, curing at different belt speed and determining the maximum curing speed. Results of the experiments are given in table 5.

TABLE 5
free radical polymerization of black ink compositions with the
monomers of the invention
			Maximum curing
		Viscosity	speed (m/min) at
	Ink number	(mPasec)	100% power
	2-0 **(compar.)	58	40
	2-1	28	20
	2-2	32	20
	2-3	32	20
	2-4	35	20

As can be seen from table 5, all black inks wherein the comparative DPGDA was replaced by a monomer of the invention showed up a much lower viscosity of the radiation curable ink, and curing of these inks was still possible using conventional UV curing systems. The lower viscosity is of utmost importance if one wants to use these inks in ink jet printheads.

Example 3

Cationic Polymerization of Non-Colored Inks

The general composition of the non-colored radiation curable inks of the invention was:

• Ultra-violet: polymerizing base epoxidle resin UTVR6105 (3,4 epoxycyclohexylmethyl 3, 4 epoxycyclohexane carboxylate; Union Carbide Corporation);
• Monomer of the invention (see table 6);
• ethanol;
• UV 9380 C: according to the MSDS of GE Silicones: a mixture of 1-5 wt % of 2-isopropylthioxanthone, 30-60 wt % C12 & C14 alkylglycidylethers, 30-60 wt % bis (4-dodecylphenyl) iodoniumhexafluoroantimonate, 5-10 wt % linear alkylate dodecylbenzene.

Substituting the monomer of the invention by the monofunctional epoxide UV 6216 (1,2 epoxyhexadecane) as comparative diluent gave rise to a comparative ink composition.

All inks were prepared on a basis of a total final weight of 20 g. All ink compositions are indicated in table 6 in weight percentage: they all had 2% wt of ethanol and 10% wt of UV 9380C. Firstly, the UVR6216 or monomer of the invention was added to the W VR6105. The resulting mixture was stirred for a couple of minutes until the added diluent was completely dissolved. As a second ink component the ethanol was added while stirring for about five minutes to complete the solution step. As the last compound the photoinitiator UV9380C was added. The resulting mixture was stirred for about 1 hour in order to completely dissolve the photoinitiator.

TABLE 6
ink composition of non-colored inks of the invention for
cationic polymerization
Ink	Monomer of the invention	wt %	wt %	wt % UV
number	chem. nature	wt %	UVR6105	ethanol	9380C
2-0	**comp. UVR6216	35.2	52.8	2.0	10.0
2-1	1.1	35.2	52.8	2.0	10.0
2-2	1.2	35.2	52.8	2.0	10.0
2-3	1.4	35.2	52.8	2.0	10.0
2-4	1.4	44.0	44.0	2.0	10.0
2-5	1.5	35.2	52.8	2.0	10.0
2-6	1.5	44.0	44.0	2.0	10.0

After the viscosities were measured each ink composition was treated similarly as the inks described in example 1: barcoating, curing at different belt speed and determining the maximum curing speed. Results of the experiments are given in table 7.

TABLE 7
cationic polymerization of ink compositions with the
monomers of the invention
	Maximum curing speed (m/min) when
	Power is:
	Viscosity		100%
Ink number	(mPasec)	60% of maximum P	(= maximum P)
2-0 **(compara.)	22	70	70
2-1	12	30	70
2-2	13	50	70
2-3	16	30	70
2-4	12	30	70
2-5	17	50	70
2-6	13	30	70

As one can see from table 7, all inks wherein the comparative UVR6216 was replaced by a monomer of the invention showed a much lower viscosity of the radiation curable ink, and excellent curing of these inks was still possible using conventional UV curing systems. The lower viscosity is of utmost importance if one wants to use these inks in ink jet printheads.

Example 4

Cationic Polymerization of Black Colored Inks

The general composition of the black colored radiation curable inks of the invention was:

• Ultraviolet polymerizing base epoxide resin UVR6105(3,4 epoxycyclohexylmethyl 3,4 epoxycyclohexane carboxylate; Union Carbide Corporation)
• Monomer of the invention (see table 8)
• Ethanol
• UV 9380 C: according to the MSDS of GE Silicones: a mixture of 1-5 wt % of ²-isopropylthioxanthone, 30-60 wt % C12 & C14 alkylglycidylethers, 30-60 wt % bis (4-dodecylphenyl) iodoniumhexafluoroantimonate, 5-10 wt % linear alkylate dodecylbenzene
• Special black 250 (Degussa)
• Admixture of 10 wt % Solpserse 24000SC (Zeneca) in UVR6216

Substituting the monomer of the invention by the monofunctional epoxide UVR 6216 (1,2 epoxyhexadecane) as comparative diluent gave rise to a comparative ink composition.

All inks were prepared on a basis of a total final weight of 20 g. All ink compositions are indicated in table 8 in weight percentage: they all contained 2% wt of ethanol and 10% wt of UV 9380C.

Firstly, the UVR6216 or monomer of the invention was added to the UVR6105. The resulting mixture was stirred for a couple of minutes until the added diluent was completely dissolved. As a third ink component, an admixture of 10 wt % SOLSPERSE 24000SC in UVR 6216, was added while stirring for about five minutes. After further adding the Special Black, the resulting ink was milled for 24 hour in a ball mill. As the last compound the photoinitiator UV9380C was added. The resulting mixture was stirred for about 1 hour in order to completely dissolve the photoinitiator.

TABLE 8
ink composition of black colored inks of the invention for
cationic polymerization
	Monomer of the		wt %
	invention	wt %	Special		wt %
Ink	(chemical)		wt %	Solsperse	Black	wt %	UV
number	nature	wt %	UVR6105	24000SC	250	ethanol	9380C
4-0	**(comparative)	30.2	45.3	0.75	5.0	2.0	10.0
	UVR6216
4-1	1.1	30.2	45.3	0.75	5.0	2.0	10.0
4-2	1.2	30.2	45.3	0.75	5.0	2.0	10.0
4-3	1.4	30.2	45.3	0.75	5.0	2.0	10.0
4-5	1.5	30.2	45.3	0.75	5.0	2.0	10.0

Again, as in example 2 for the black colored inks for free radical polymerization, the viscosities were measured, and each ink composition was treated similarly as the inks already described in the foregoing examples. Results of the experiments are given in table 9.

TABLE 9
Cationic free radical polymerization of black ink compositions
with the monomers of the invention
		Viscosity	Maximum curing speed
	Ink number	(mPasec)	(m/min) at 100% power
	4-0 **(compar.)	24	40
	4-1	18	40
	4-2	21	40
	4-3	23	30
	4-4	22	30

Although the differences in viscosity are not as big as in the clear inks—mainly as a result of the addition of a black colored pigment, leading to an overall higher viscosity—it can be seen from table 9 that introduction of the monomers of the present invention resulted in a lower viscosity. Curing of the inks was still possible using conventional UV curing systems.

Claims

1. An ultraviolet curable ink composition for ink jet printing comprising an ultraviolet curable monomer represented by the following general formula I: ##STR00029##

wherein,

R¹ represents hydrogen, or a substituted or unsubstituted alkyl group,

L represents a linking group, wherein the linking group is an aliphatic chain of at least three carbon atoms,

X represents O, S or NR² wherein R² has the same meaning as R¹; when X=NR², L and R² may form together a ring system,

m and n independently represent a value from 1 to 5.

2. ultraviolet curable ink composition for ink jet printing according to claim 1 wherein said composition further contains a colorant.

3. ultraviolet curable ink composition for ink jet printing according to claim 2 wherein said colorant is a dispersed pigment.

4. ultraviolet curable ink composition for ink jet printing according to claim 3 wherein said pigment is chosen from the list consisting of Pigment Yellow 128, 93, 17, 74, 138, 139, 154, 180, 185; Pigment Red 122, 57:1, 184; Pigment Blue 15:3, Pigment Blue 15:4 and carbon black.

5. ultraviolet curable ink composition for ink jet printing according to claim 1 wherein said composition further contains a photoinitiator or a mixture of photoinitiators.

6. ultraviolet curable ink composition for ink jet printing according to claim 5 wherein said composition further contains an initiator synergist.

7. ultraviolet curable ink composition for ink jet printing according to claim 1 wherein said ink composition further contains a second photopolymerizable monomer, oligomer or prepolymer and the monomer represented by formula (I) serves as reactive diluent.

8. ultraviolet curable ink composition for ink jet printing according to claim 7 wherein said second monomer is selected from the group consisting of the following chemical classes: an amino modified polyether acrylate, a cycloaliphatic epoxy compound, an urethane acrylate, a polyester acrylate, a polyether acrylate, and an epoxy acrylate.

9. ultraviolet curable ink composition for ink jet printing according to claim 1 wherein the viscosity of said ink composition is comprised between 1 and 75 mPa.s at 25° C.

10. ultraviolet curable ink composition for ink jet printing according to claim 1 further comprising a dendrimer.

11. Process for obtaining a monochrome or multicolor ink jet image comprising jetting one or more streams of ink droplets having a composition according to any one of the previous claims to a receiver element, and subjecting the obtained image to ultraviolet curing.

12. Process according to claim 11 wherein said ultraviolet curing is performed by means of one or more ultra-violet sources.

13. An ultraviolet curable ink composition for ink jet printing comprising a free radical photoinitiator, an amine co-initiator and a radiation curable monomer represented by formula I: ##STR00030##

wherein,

R¹ represents hydrogen, or a substituted or unsubstituted alkyl group,

L represents a linking group,

X represents O, S or NR² wherein R² has the same meaning as R¹; when X=NR², L and R² may form together a ring system,

m and n independently represent a value from 1 to 5, characterized in that said radiation-curable monomer represented by said formula I is selected from the group consisting of: ##STR00031## ##STR00032## ##STR00033## ##STR00034##

 and

wherein the viscosity of said ink composition is between 1 and 75 mPa.s at 25° C.

14. ultraviolet curable ink composition according to claim 13, wherein said composition further contains a colorant.

15. ultraviolet curable ink composition according to claim 14, wherein said colorant is a dispersed pigment.

16. ultraviolet curable ink composition according to claim 15 wherein said pigment is chosen from the list consisting of Pigment Yellow 128, 93, 17, 74, 138, 139, 154, 180, 185; Pigment Red 122, 57:1, 184; Pigment Blue 15:3, Pigment Blue 15:4 and carbon black.

17. ultraviolet curable ink composition according to claim 13, wherein said composition contains a mixture of photoinitiators.

18. ultraviolet curable ink composition according to claim 13, wherein said ink composition further contains a second photopolymerizable monomer, oligomer or prepolymer and the monomer represented by formula (I) serves as reactive diluent.

19. ultraviolet curable ink composition according to claim 18, wherein said second monomer is chosen from the group consisting of following chemical classes: an amino modified polyether acrylate, a cycloaliphatic epoxy compound, an urethane acrylate, a polyester acrylate, a polyether acrylate, and an epoxy acrylate.

20. ultraviolet curable ink composition according to claim 13, wherein said radiation curable ink composition further comprising a dendrimer.

21. ultraviolet curable ink composition according to claim 13, wherein the co-initiator is aminobenzoate co-initiator.

22. ultraviolet curable ink composition according to claim 13 wherein the photoinitiator is copolymerizable.

23. Process for obtaining multicolour ink jet image comprising the steps of jetting one or more streams of ink droplets having a composition according to claim 13 to a receiver element, and subjecting the obtained image to radiation curing.