PRINTING INK

Abstract

The present invention provides an inkjet ink comprising: 6-35% by weight of NVC; 5-60% by weight of PEA; 15-35% by weight of a C8.12 alkane diol di(meth)acrylate; a radical photoinitiator; and a colorant, wherein the percentages by weight are based on the total weight of the ink. The present invention further provides an inkjet ink set wherein at least one of the inks in the set, preferably all of the inks in the set, is an inkjet ink as defined above. Furthermore, the present invention provides a method of inkjet printing comprising inkjet printing the inkjet ink or inkjet ink set as defined above onto a substrate and curing the ink.

Claims

1. An inkjet ink comprising: an N-vinyl amide and/or N-acryloyl amine monomer; at least two cyclic monofunctional (meth)acrylate monomers; a difunctional (meth)acrylate monomer; a radical photoinitiator; and a colorant, wherein one of the cyclic monofunctional (meth)acrylate monomers is PEA, and wherein the difunctional (meth)acrylate monomer is a C8-12alkane diol di(meth)acrylate.

2. An inkjet ink as claimed in claim 1, wherein the C8-12 alkane diol di(meth)acrylate is the sole difunctional monomer present in the ink.

3. An inkjet ink as claimed in claim 1, wherein the ink is substantially free of multifunctional monomers.

4. An inkjet ink as claimed in claim 1 wherein the C8-12alkane diol di(meth)acrylate is 1,10-decanediol diacrylate (DDDA).

5. An inkjet ink as claimed in claim 1, wherein the ink contains 8-25% by weight of C8-12alkane diol di(meth)acrylate, based on the total weight of the ink.

6. An inkjet ink as claimed in claim 1, wherein the N-vinyl amide and/or N-acryloyl amine monomer is NVC.

7. An inkjet ink as claimed in claim 1, wherein one of the cyclic monofunctional (meth)acrylate monomer is IBOA.

8. An inkjet ink as claimed in claim 1, wherein the only cyclic monofunctional (meth)acrylate monomers present in the ink are PEA and IBOA.

9. An inkjet ink as claimed in claim 1, wherein the colorant is a dispersed pigment.

10. An inkjet ink as claimed in claim 1, wherein the ink is substantially free of water and volatile organic solvents.

11. An inkjet ink set wherein at least one of the inks in the set, preferably all of the inks in the set, is an inkjet ink as claimed in claim 1.

12. A cartridge containing the inkjet ink or the inkjet ink set as claimed in claim 1.

13. A printed substrate having the ink or the inkjet ink set as claimed in claim 1 printed thereon.

14. A method of inkjet printing comprising inkjet printing the inkjet ink or inkjet ink set as claimed in claim 1 onto a substrate and curing the ink.

15. A method as claimed in claim 14, wherein the substrate has a surface energy of 25-50 mN/m.

Description

EXAMPLES

Example 1

[0070] Inkjet inks were prepared according to the formulations set out in Table 1. The inkjet ink formulations were prepared by mixing the components in the given amounts. Amounts are given as weight percentages based on the total weight of the ink.

TABLE-US-00001 TABLE 1 Ink 1 Ink 3 (com- Ink 2 (com- Component parative) (invention) parative) NVC (monofunctional monomer) 16.5 16.5 — PEA (monofunctional monomer) 32.05 24.68 — CTFA (monofunctional monomer) 17.63 — — IBOA (monofunctional monomer) 11.9 11.9 — DDDA (difunctional monomer) — 20 — DPGDA (difunctional monomer) — — 30.7 HDDA (difunctional monomer) — — 30.23 DVE-3 (difunctional monomer) — — 9.41 Ebecryl 230 (oligomer) — — 2.5 Craynor CN964A85 (oligomer) 5.0 9 UV12 (stabiliser) 0.5 0.5 0.8 SM834 (pigment dispersion) 6 6 4.53 Photoinitiator package 14.42 14.42 12.71 BYK307 (surfactant) 1 1 0.1 Total 100 100 100

[0071] Craynor CN964A85 is an aliphatic polyester-based urethane diacrylate oligomer. SM834 is a cyan pigment dispersion containing 10%. Solsperse 32000, 1% Florstab, 59% Sartomer 339Y (PEA) and 30% heliogen blue D 7110 F (total 100%).

[0072] The photoinitiator package contains 0.85% EDB, 0.8% ITX, 2.88% BP, 1.88% Irgacure 184 and 8.01% TPO (total 14.42%).

[0073] Inks were printed and cured onto 220 micron PVC using an Acuity 350 Inkjet printer. They were tested for adhesion, blocking and embrittlement. Cross hatch tape adhesion was tested according to BS EN ISO 2409. Embrittlement was tested by rolling an A5 block print (print side out) and striking on a hard surface (bench top) and assessing the damage to the print/substrate (number of cracks propagating from tip of print). Blocking was tested by placing a stack of the prints, both face-to-face and face-to-back under a 20 Kg weight for 24 hours and then checking the prints for ink offset.

[0074] Ink 1 showed excellent adhesion but poor blocking and poor embrittlement. Ink 2 showed excellent adhesion, blocking and embrittlement properties. Ink 3 showed excellent block resistance, poor embrittlement and moderate adhesion.