Radiation curable inks
Radiation curable ink compositions for impulse printheads are described. The compositions include a photoinitiator system, containing both a photocation polymerization initiator and a free-radical photoinitiator, an acrylate ester of a carboxylic acid ester, and at least one radiation curable material.
1. A radiation curable ink composition for impulse printheads, comprising:
a) a photoinitiator system which comprises both a photocation polymerization initiator and a free-radical photoinitiator, each in the amount of about 1 to about 12 wt. %;
b) from about 0.5 to about 30 wt. % of an acrylate ester of a carboxylic acid ester represented by the formula:
having a carboxylate ester moiety containing groups R 1 , R 2 and R 3 , which are each independently alkyl, aryl, alkylaryl, alkoxyaryl or cycloaliphatic groups, where the total number of carbon atoms included in groups R 1 , R 2 and R 3 range from 1 to 10, and wherein R 4 is a group selected from hydrogen, methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, phenyl and alkoxy phenyl; and
c) from about 3 to about 60 wt. % of at least one radiation curable material containing a radiation curable functional group;
wherein the ink composition has a viscosity of less than about 70 cPs at 25° C.
2. The radiation curable ink composition of claim 1 wherein the carboxylate ester moiety is derived from alpha,alpha-dimethyl-Caproic acid, alpha-ethyl-alpha-methyl-Caproic acid, alpha,alpha-diethyl-Caproic acid, alpha,alpha-diethyl-Valeric acid, alpha,alpha-dimethyl-Capric acid, alpha-butyl-alpha-ethyl-Capric acid, alpha,alpha-dimethyl-Enanthic acid, alpha, alpha-diethyl-Pelargonic acid, alpha-butyl-alpha-methyl-Caproic acid, alpha,alpha-dimethyl-Caprylic acid, alpha-methyl-alpha-propyl-Caproic acid, alpha-ethyl-alpha-methyl-Enanthic acid, alpha-methyl-alpha-propyl-Valeric acid, alpha-ethyl-alpha-methyl-Caprylic acid, alpha-butyl-alpha-methyl-Caprylic acid, alpha-ethyl-alpha-propyl-Caproic acid, alpha-ethyl-alpha-propyl-Valeric acid, alpha-butyl-alpha-ethyl-Pelargonic acid, alpha,alpha-dimethyl Propionic acid (pivalic acid), neodecanoic acid and combinations thereof.
3. The radiation curable ink composition of claim 1 wherein the radiation curable material comprises a mono-functional monomer, a poly-functional monomer and a di-functional monomer.
4. The radiation curable ink composition of claim 1 wherein the radiation curable material comprises a mono-functional monomer and a poly-functional monomer, and is substantially free of di-functional monomer.
5. The radiation curable ink composition of claim 1 wherein the radiation curable material comprises a mono-functional monomer and a di-functional monomer, and is substantially free of a poly-functional monomer.
6. The radiation curable ink composition of claim 1 wherein the radiation curable material comprises a mono-functional oxetane.
7. The radiation curable ink composition of claim 1 wherein the photocation polymerization initiator and the free-radical photoinitiator are each independently utilized in an amount of about 0.5 to about 15 wt. %, based on the total weight of the ink.
8. The radiation curable ink composition of claim 1 wherein the acrylate ester of carboxylate acid ester is utilized in an amount of about 0.5 to about 30 wt. %, based on the total weight of the ink.
9. The radiation curable ink composition of claim 1 wherein the at least one radiation curable material comprises a mono-functional component in an amount of about 1 to about 70 wt. %, a poly-functional component in an amount of about 0 to about 95 wt. %, and a di-functional component in an amount of about 0 to about 95 wt. %, based on the total weight of the ink.
10. The radiation curable ink composition of claim 1 wherein the at least one radiation curable material comprises a mono-functional component in an amount of about 3 to about 60 wt. %, a poly-functional component in an amount of about 5 to about 80 wt. %, and a di-functional component in an amount of about 5 to about 80 wt. %, based on the total weight of the ink.
11. The radiation curable ink composition of claim 1 further comprising a silane adhesion promoter.
12. The radiation curable ink composition of claim 1 wherein the composition has a jet operating window at a jetting frequency of at least about 1 Hz to about 32 kHz, and wherein the composition exhibits stable jetting after residing in the printhead for a period of at least 1 day.
13. The radiation curable ink composition of claim 1 wherein the composition has a jet operating window at a jetting frequency of at least about 1 Hz to about 16 kHz, and wherein the composition exhibits stable jetting, after residing in the printhead for a period of at least 1 day.
14. The radiation curable ink composition of claim 11 wherein the composition has a jet operating window at a jetting frequency of at least about 1 Hz to about 32 kHz, and wherein the composition exhibits stable jetting, after residing in the printhead for a period of at least 1 day.
15. A radiation curable ink composition for impulse printheads, comprising:
a) a photoinitiator system which comprises both , based on the total weight of the ink, from about 2 to about 10 wt. % of a photocation polymerization initiator and, based on the total weight of the ink, from about 1 to about 12 wt. % of a free-radical photoinitiator;
b) from about 1 to about 25 wt. % of an acrylate ester of a carboxylic acid ester represented by the formula:
having a carboxylate ester moiety containing groups R 1 , R 2 and R 3 , which are each independently alkyl, aryl, alkylaryl, alkoxyaryl or cycloaliphatic groups, where the total number of carbon atoms included in groups R 1 , R 2 and R 3 range from 1 to 10, and wherein R 4 is a group selected from hydrogen, methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, phenyl and alkoxy phenyl; and
c) from about 5 to about 50 wt. % of at least one radiation curable material containing a radiation curable functional group selected from the group consisting of an acrylate ester monomer having hydroxyl functionality, a mono-functional oxetane, a mono-functional epoxy, a mono-functional vinyl ether or vinyl ether alcohol, a mono-functional ethylenically unsaturated compound, a mono-functional oligomer, and a mixture thereof;
wherein the ink composition has a viscosity of less than about 70 cPs at 25° C.
16. The radiation curable ink composition of claim 15 , wherein the radiation curable functional group comprises a mono-functional oxetane and a di-functional oxetane.
17. The radiation curable ink composition of claim 15 , having an elongation of at least 40%.
18. The radiation curable ink composition of claim 1 wherein the acrylate ester monomer of the carboxylic acid ester is utilized in an amount of about 1 to about 25 wt. %.
19. The radiation curable ink composition of claim 1 wherein the ink composition has a viscosity of about 5 to about 70 cPs at 25° C.
20. The radiation curable ink composition of claim 15 wherein the ink composition has a viscosity of about 5 to about 70 cPs at 25° C.