Method of printing pigment-based inks including ink sets, inks and printers therefor

Patent metadata

Field	Value
Publication number	US-9834694-B2
Application number	US-201414532768-A
Country	US
Kind code	B2
Filing date	Nov 4, 2014
Priority date	Nov 19, 2013
Publication date	Dec 5, 2017
Grant date	Dec 5, 2017

Abstract

A method of inkjet printing includes the steps of: printing a first ink onto a print medium, the first ink including a first self-dispersible pigment, the first ink having a first pigment content A; and subsequently printing a second ink onto the print medium at least partially over the first ink, the second ink including a second pigment and a polymeric dispersant encapsulating the second pigment, the second ink having a second pigment content B. The first self-dispersible pigment and the second pigment have a same color; the pigment content A of the first ink and the pigment content B of the overprinted second ink have a relationship 0.8≦A/B≦1.2; and a polymer acid value of the polymeric dispersant is in the range of 100 to 170.

First claim

The invention claimed is:

1. A method of inkjet printing comprising the steps of:
printing a first ink onto a print medium, the first ink comprising a first self-dispersible pigment in an amount A in terms of a wt. % of the first ink; and
subsequently printing a second ink onto the print medium at least partially over the first ink, the second ink comprising a second pigment in an amount B, in terms of a wt. % of the second ink, and a polymeric dispersant encapsulating the second pigment;

wherein:
the first self-dispersible pigment and the second pigment have a same color;
the amount A of the first pigment and the amount B of the second pigment have a relationship 0.8≦A/B≦1.2;
a polymer acid value of the polymeric dispersant is in the range of 100 to 170 KOH mg/g; and
a weight-average molecular weight of the polymeric dispersant is in the range of 20,000 to 200,000.

2. The method of claim 1 , wherein ejected droplet weights of the first ink and the second ink are in the range of 1 ng to 5 ng per droplet, and a difference in droplet weights between the first ink and the second ink is less than 0.3 ng per droplet.

3. The method of claim 1 , wherein the second ink is printed over the first ink within a period of less than 10 milliseconds.

4. The method of claim 1 , wherein the first self-dispersible pigment and the polymeric dispersant encapsulating the second pigment have a same surface polarity.

5. The method of claim 1 , wherein the first self-dispersible pigment is a surface-modified derivative of the second pigment.

6. The method of claim 1 , wherein the first self-dispersible pigment comprises hydrophilic groups directly bonded to a pigment surface.

7. The method of claim 6 , wherein the first self-dispersible pigment comprises carboxylate groups directly bonded to the pigment surface, the first self-dispersible pigment being obtainable via oxidation of the second pigment.

8. The method of claim 1 , wherein at least the first ink comprises trimethylolpropane.

9. The method of claim 8 , wherein at least the first ink further comprises triethylene glycol.

10. The method of claim 1 , wherein the first and second inks comprise the same co-solvents.

11. The method of claim 1 , wherein the viscosities at 35° C. of the first ink and the second ink are in the range of 1.5 mPa·s to 4.0 mPa·s, and wherein a difference in viscosities at 35° C. between the first ink and the second ink is less than 0.5 mPa·s.

12. The method of claim 1 , wherein the surface tensions at 20° C. of the first ink and the second ink are in the range of 28 mN/m to 40 mN/m, and a difference in surface tensions at20 ° C. between the first ink and the second ink is less than 3 mN/m.

13. The method of claim 1 , wherein the amount A and the amount B are each in the range of 2 wt % to 7 wt %.

14. An ink set for an inkjet printer comprising:
a first ink comprising a first self-dispersible pigment in an amount A in terms of a wt. % of the first ink; and
a second ink comprising a second pigment in an amount B, in terms of a wt. % of the second ink, and a polymeric dispersant encapsulating the second pigment,

wherein:
the first self-dispersible pigment and the second pigment have a same color;
the amount A of the first pigment and the amount B of the second pigment have a relationship 0.8≦A/B≦1.2;
a polymer acid value of the polymeric dispersant is in the range of 100 to 170 KOH mg/g; and
a weight-average molecular weight of the polymeric dispersant is in the range of 20,000 to 200,000.

15. The ink set of claim 14 , wherein the first and second inks have one or more of the following physical properties:
the viscosities at 35° C. of the first ink and the second ink are in the range of 1.5 mPa·s to 4.0 mPa·s;
a difference in viscosities at 35° C. between the first ink and the second ink is less than 0.5 mPa·s;
the surface tensions at 20° C. of the first ink and the second ink are in the range of 28 mN/m to 40 mN/m; and
a difference in surface tensions at 20° C. between the first ink and the second ink is less than 3 mN/m.

16. The ink set of claim 14 , wherein at least the first ink comprises one or more co-solvents selected from the group consisting of: triethylene glycol and trimethylolpropane.

Assignees

• Memjet Technology Ltd
• Memjet Technology Ltd

Inventors

• Fukuda Teruyuki
• Tanaka Satoshi
• Bisson Adrian
• Davey Roger
• Myors Richard
• Bernard Stephen
• Read Philippa
• Blake Iain
• Carter Steven

Classifications

• C09D11/40

  Ink-sets specially adapted for multi-colour inkjet printing · CPC title

• C08K5/47

  Thiazoles · CPC title

• C09D11/322

  Pigment inks · CPC title

• C09D125/14

  with unsaturated esters · CPC title

• C09D11/38 Primary

  characterised by non-macromolecular additives other than solvents, pigments or dyes · CPC title