Additive for high optical density inkjet ink
View Patent ↗This invention pertains to an aqueous inkjet ink with a certain chelator additive, inkjet ink sets based on this aqueous inkjet ink, and to a method of printing with these inks and ink sets, whereby optical density (OD) of a printed image is increased. The chelator additive is particularly advantageous for increasing the OD of inks with a self-dispersing pigment colorant, and particularly the combination of such colorant with a multivalent cation additive.
1. An inkjet ink comprising an aqueous vehicle and a chelator, wherein the chelator comprises a non-polymeric molecule having at least two coordinating nitrogen atoms and no carboxyl groups and wherein either a) the ink is substantially colorless or b) the ink further comprises a self-dispersing pigment colorant.
2. The inkjet ink of claim 1 , wherein the chelator is selected from the group consisting of phenanthroline, 2,2-dipyridyl, 2,2-dipyridylamine and ethylene diamine, and derivatives thereof.
3. The inkjet ink of claim 1 , having a surface tension in the range of about 20 dyne/cm to about 70 dyne/cm at 25° C., and a viscosity as high as 30 cP at 25° C.
4. The inkjet ink of claim 1 , wherein the ink is substantially colorless.
5. The inkjet ink of claim 4 , wherein the chelator is selected from the group consisting of phenanthroline, 2,2-dipyridyl, 2,2-dipyridylamine and ethylene diamine, and derivatives thereof.
6. The inkjet ink of claim 4 , having a surface tension in the range of about 20 dyne/cm to about 70 dyne/cm at 25° C., and a viscosity as high as 30 cP at 25° C.
7. The inkjet ink of claim 1 , wherein the ink comprises a self-dispersing pigment colorant.
8. The inkjet ink of claim 7 , wherein the chelator is present at a level effective to increase optical density over the same ink without chelator.
9. The inkjet ink of claim 7 , having a surface tension in the range of about 20 dyne/cm to about 70 dyne/cm at 25° C., and a viscosity as high as 30 cP at 25° C.
10. The inkjet ink of claim 7 , further comprising a multivalent cationic metal species.
11. The inkjet ink of claim 7 , wherein the chelator is selected from the group consisting of phenanthroline, 2,2-dipyridyl, 2,2-dipyridylamine and ethylene diamine, and derivatives thereof.
12. An inkjet ink set comprising a first inkjet ink and a second inkjet ink, wherein the first inkjet ink is a substantially colorless inkjet ink comprising an aqueous vehicle and a chelator, wherein the chelator comprises a non-polymeric molecule having at least two coordinating nitrogen atoms and no carboxyl groups, and the second inkjet ink is a colored ink comprising of an aqueous vehicle and pigment colorant.
13. The inkjet ink set of claim 12 , wherein the chelator in the first inkjet ink is selected from the group consisting of phenanthroline, 2,2-dipyridyl, 2,2-dipyridylamine and ethylene diamine, and derivatives thereof.
14. The inkjet ink set of claim 12 , wherein the first inkjet ink has a surface tension in the range of about 20 dyne/cm to about 70 dyne/cm at 25° C., and a viscosity as high as 30 cP at 25° C.
15. An inkjet ink set comprising a at least three differently colored inkjet inks comprising, individually, a colorant stably dispersed or dissolved in an aqueous vehicle, wherein at least one of the three differently colored inkjet inks further comprises a chelator, wherein the chelator comprises a non-polymeric molecule having at least two coordinating nitrogen atoms and no carboxyl groups.
16. The inkjet ink set of claim 15 , wherein the chelator in the at least one of the three differently colored inkjet inks is present at a level effective to increase optical density over the same ink without chelator.
17. The inkjet ink set of claim 15 , wherein the colorant in the at least one of the three differently colored inkjet inks is a self-dispersing pigment.
18. The inkjet ink set of claim 15 , wherein the at least one of the three differently colored inkjet inks has a surface tension in the range of about 20 dyne/cm to about 70 dyne/cm at 25° C., and a viscosity as high as 30 cP at 25° C.
19. The inkjet ink set of claim 15 , wherein the at least one of the three differently colored inkjet inks further comprises a multivalent cationic metal species.
20. The inkjet ink set of claim 15 , wherein the chelator in the at least one of the three differently colored inkjet inks is selected from the group consisting of phenanthroline, 2,2-dipyridyl, 2,2-dipyridylamine and ethylene diamine, and derivatives thereof.
21. A method for ink jet printing onto a substrate, comprising the steps of:
(a) providing an ink jet printer that is responsive to digital data signals;
(b) loading the printer with a substrate to be printed;
(c) loading the printer with an inkjet ink; and
(d) printing onto the substrate using the inkjet ink in response to the digital data signals,
wherein the inkjet ink comprises an aqueous vehicle and a chelator, wherein the chelator comprises a non-polymeric molecule having at least two coordinating nitrogen atoms and no carboxyl groups and wherein either a) the ink is substantially colorless or b) the ink further comprises a self-dispersing pigment colorant.
22. The method of claim 21 , wherein the printer is loaded with an inkjet ink set comprising a first inkjet ink and a second inkjet ink, wherein the first inkjet ink is a substantially colorless inkjet ink comprising an aqueous vehicle and a chelator, wherein the chelator comprises a non-polymeric molecule having at least two coordinating nitrogen atoms and no carboxyl groups, and the second inkjet ink is a colored ink comprising of an aqueous vehicle and pigment colorant.
23. The method of claim 22 , wherein the second inkjet ink is underprinted with the first inkjet ink.