This invention pertains to an ink for inkjet printing, in particular to an aqueous ink comprising a self-dispersing pigment colorant and certain soluble polymers which enhance print quality without compromising jetting performance.
1. An aqueous inkjet ink composition comprising:
(a) a self-dispersing pigment;
(b) an aqueous vehicle; and
(c) a structured polymer that is soluble in the aqueous vehicle, wherein said structured polymer is either
i) a soluble AB or ABC block copolymer with an A block of benzyl methacrylate; or
ii) a soluble graft copolymer, wherein said graft copolymer comprises 50-90% by weight, of a polymeric backbone and 10-50% by weight, of macromonomer side chains attached to the backbone at a single terminal point, and said graft copolymer has a weight average molecular weight of 5,000-100,000, wherein
(i′) the polymeric backbone is hydrophobic in comparison to the side chains and consists essentially of polymerized phenoxyethylacrylate and ethoxytriethyleneglycol methacrylate, and up to 20% by weight, based on the weight of the graft copolymer, of polymerized methacrylic acid; and
(ii′) the macromonomer sidechains have a weight average molecular weight of about 1,000-30,000 and consist of polymerized ethoxytriethyleneglycol methacrylate and 2-100% by weight, based on the weight of the macromonomer side chains, of polymerized methacrylic acid.
2. The ink of claim 1 , wherein the soluble structured polymer is present at a weight ratio of pigment to soluble structured polymer of between about 0.5 to about 20.
3. The ink of claim 1 , wherein the soluble structured polymer is an anionic polymer having a number average molecular weight in the range of about 1,000 to about 20,000.
4. The ink of claim 1 , wherein the soluble structured polymer is a soluble AB or ABC block copolymer with an A block of benzyl methacrylate.
5. The ink of claim 1 , further comprising a dispersed polymer binder.
6. The ink of claim 5 , wherein the dispersed polymer binder is a polyurethane.
7. The ink of claim 1 , wherein the self-dispersing pigment is a self-dispersing carbon black pigment comprising anionic hydrophilic moieties.
8. The ink of claim 7 , wherein the anionic hydrophillic moieties on the self-dispersing carbon black pigment are primarily carboxyl groups directly attached to the pigment surface.
9. A method of inkjet printing comprising printing an inkjet ink from a thermal inkjet printhead where said inkjet ink is an ink according to any of claims 1 , 3 - 4 , and 7 - 8 .
10. The ink of claim 1 , wherein the ink is a thermal inkjet ink.
11. The ink of claim 4 , wherein the soluble AB or ABC block copolymer is comprised of an A block of benzyl methacrylate and a B block selected from the group consisting of methacrylic acid, dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate, dipropylaminoethyl methacrylate, and dibutylaminoethyl methacrylate.
12. The ink of claim 4 , wherein the soluble structured polymer is a soluble AB block copolymer with an A block of benzyl methacrylate and a B block of methacrylic acid/ethylene glycol methacrylate copolymer.
13. The ink of claim 4 , wherein the soluble structured polymer is a soluble ABC block copolymer with an A block of benzyl methacrylate, a B block of methacrylic acid, and a C block of ethoxyltriethyleneglycol methacrylate.