Ink system for cure under low-energy conditions
UV-curable ink formulations are provided that are capable of being cured under low-energy conditions, such as with a conventional mercury vapor lamp operating at half or less of the lamp's nominal wattage or using an LED lamp. Methods for forming a printed ink image on a substrate using the ink are also provided, which permit maintenance of relatively high line speeds while consuming less energy due to the use of lower-wattage lamp settings.
1. A UV-curable ink composition comprising:
a monomer system comprising at least one monomer;
an oligomer system comprising at least one acrylate oligomer;
an acrylate polymer resin;
a pigment; and
an initiator system comprising at least one phosphine oxide photoinitiator, at least one ketone photoinitiator, at least one titanocene photoinitator and at least one amine co-initiator,
wherein said UV-curable ink composition is capable of being cured by exposure to UV light emitted from a lamp operating at 100 W or less at a line speed of at least 50 ft/min.
2. The UV-curable ink composition of claim 1 , said composition further comprising fumed silica.
3. The UV-curable ink composition of claim 1 , said composition further comprising methyl diethanolamine (MDEA).
4. The UV-curable ink composition of claim 1 , wherein said monomer system is comprised of mono-, di-, and trifunctional acrylate monomers.
5. The UV-curable ink composition of claim 1 , wherein said acrylate polymer resin is a methyl methacrylate/n-butyl methacrylate copolymer resin.
6. The UV-curable ink composition of claim 1 , wherein said oligomer system comprises at least two acrylate oligomers.
7. The UV-curable ink composition of claim 1 , wherein said monomer system comprises from about 20% to about 60% by weight of said composition.
8. The UV-curable ink composition of claim 1 , wherein said oligomer system comprises from about 10% to about 40% by weight of said composition.
9. The UV-curable ink composition of claim 1 , wherein said initiator system comprises from about 2% to about 12% by weight of said composition.
10. The UV-curable ink composition of claim 1 , said composition comprising an amide wax.
11. A method for creating an article having a printed ink image thereon comprising the steps of:
printing an ink image onto a substrate using a UV-curable ink composition to form a printed substrate, said UV-curable ink composition comprising—
a monomer system comprising at least one monomer;
an oligomer system comprising at least one acrylate oligomer;
and an initiator system comprising one or more members selected from the group consisting of phosphine oxide photoinitiators, ketone photoinitiators, and titanocene photoinitators;
passing said printed substrate through a curing station at a rate of at least 50 linear feet per minute to form said article, said curing station comprising at least one lamp operating at a wattage of less than 100 W while said printed substrate is being passed through said curing station.
12. The method of claim 11 , wherein said monomer system is comprised of mono-, di-, and trifunctional acrylate monomers.
13. The method of claim 11 , wherein said monomer system comprises from about 20% to about 60% by weight of said composition.
14. The method of claim 11 , wherein said oligomer system further comprises at least one urethane acrylate oligomer.
15. The method of claim 11 , wherein oligomer system comprises between about 10% to about 40% by weight of said composition.
16. The method of claim 11 , wherein said initiator system comprises between about 2% to about 12% by weight of said composition.
17. The method of claim 11 , wherein said lamp comprises a mercury-vapor lamp.
18. The method of claim 11 , wherein said lamp comprises an LED lamp.
19. The method of claim 11 , wherein said step of passing said printed substrate through a curing station exposes said ink composition to an energy level of from about 5 to about 125 mJ.
20. The method of claim 11 , wherein said step of passing said printed substrate through a curing station exposes said ink composition to a power level of from about 200 to about 800 mW.