Additive for high optical density inkjet ink

• US 20050274281A1
• Filed: 05/31/2005
• Published: 12/15/2005
• Est. Priority Date: 06/09/2004
• Status: Active Grant

• Current Assignee: DuPont Electronics, Inc. (DuPont de Nemours, Inc.)
• Original Assignee: E. I. du Pont de Nemours and Company (Corteva, Inc.)
• Inventors: Jackson, Christian
• Granted Patent: US 7,351,278 B2
• Time in Patent Office: Days
• US Class Current: 106/31.430
• CPC Class Codes: C09D 11/30 Inkjet printing inks
• CPC Class Codes: C09D 11/40 Ink-sets specially adapted for multi-colour inkjet printing
• CPC Class Codes: C09D 11/54 Inks based on two liquids, one liquid being the ink, the other liquid being a reaction solution, a fixer or a treatment solution for the ink

Abstract

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.

Claims

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.

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, further comprising a 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, wherein the colorant is a self-dispersing pigment.

10. 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.

11. The inkjet ink of claim 7, further comprising a multivalent cationic metal species.

12. 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.

13. 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.

14. The inkjet ink set of claim 13, 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.

15. The inkjet ink set of claim 13, 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.

16. 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.

17. The inkjet ink set of claim 16, 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.

18. The inkjet ink set of claim 16, wherein the colorant in the at least one of the three differently colored inkjet inks is a self-dispersing pigment.

19. The inkjet ink set of claim 16, 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.

20. The inkjet ink set of claim 16, wherein the at least one of the three differently colored inkjet inks further comprises a multivalent cationic metal species.

21. The inkjet ink set of claim 16, 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.

22. 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.

23. The method of claim 22, 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.

24. The method of claim 23, wherein the second inkjet ink is underprinted with the first inkjet ink.