# US 11,441,044 B2 · Pigment-based ink formulations having improved printhead lifetime > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 11,441,044 B2 - Document ID: US11441044B2 - Status: Granted - Kind: B2 - Application number: 16/549,570 - Filed: 2019-08-23 - Published: 2020-02-27 - Granted: 2022-09-13 - Earliest claimed: 2018-08-24 - Assignees: Memjet Technology Limited - Applicants: Memjet Technology Limited - Inventors: Simon Fielder; Alison Chong; David Tyvoll; Tim Hudson; Roger Davey; Ellaine Munton - Web page: https://patentgrep.com/patent/US11441044B2 ## CPC - C09D 11/38: characterised by non-macromolecular additives other than solvents, pigments or dyes - B41J 2/14: Structure thereof {only for on-demand ink jet heads} - C09D 11/322: Pigment inks - C09D 11/40: Ink-sets specially adapted for multi-colour inkjet printing - C09D: COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR (cosmetics A61K; processes for applying liquids or other fluent materials to surfaces, in general, B05D; staining wood B27K5/02; glazes or vitreous enamels C03C; natural resins, French polish, drying-oils, driers, turpentine, per se, C09F; polishing compositions other than French polish, ski waxes C09G; adhesives or use of materials as adhesives C09J; materials for sealing or packing joints or covers C09K3/10; materials for stopping leaks C09K3/12; processes for the electrolytic or electrophoretic production of coatings C25D) - B41J: TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS ## Abstract An aqueous-based inkjet ink for a thermal inkjet printhead includes: a pigment; 2 to 90 ppm ammonium ions; and an ink vehicle. The ink has a pH in the range of 8 to 9.5 and exhibits improved lifetime in thermal inkjet printheads with minimal loss of print quality. ## Claims ### Claim 1 An aqueous-based inkjet ink for a thermal inkjet printhead comprising: a pigment; 2 to 90 ppm ammonium ions; and an ink vehicle, wherein the ink has a pH in the range of 8 to 9.5. ### Claim 2 (depends on 1) The inkjet ink of claim 1, wherein the ammonium ions are present as one or more ammonium salts selected from the group consisting of: ammonium formate, ammonium acetate, ammonium nitrate, ammonium carbonate, ammonium hydrogen carbonate, ammonium hydroxide, ammonium hexafluorophosphate, ammonium carbamate, ammonium tetrafluoroborate, ammonium perchlorate, ammonium trifluoroacetate, ammonium trifluoromethanesulfonate, tri-ammonium phosphate, ammonium sulfide, di-ammonium citrate, tri-ammonium citrate, ammonium phthalate, ammonium lactate, ammonium benzoate, ammonium succinate, ammonium salicylate, ammonium tartrate, ammonium hydrogen tartrate, ammonium amidosulfate, ammonium oxalate, ammonium hydrogen oxalate, ammonium fluoride, ammonium chloride, ammonium bromide, ammonium iodide and ammonium sulfate. ### Claim 3 (depends on 1) The inkjet ink of claim 1, wherein the ammonium ions are present as ammonium formate or ammonium nitrate. ### Claim 4 (depends on 1) The inkjet ink of claim 1 further comprising from 0.1 to 10 ppm of a trivalent metal ion. ### Claim 5 (depends on 4) The inkjet ink of claim 4, wherein the trivalent metal ion is selected from the group consisting of: Al3+ and Ga3+. ### Claim 6 (depends on 1) The inkjet ink of claim 1, wherein the ink vehicle comprises at least one anti-kogation additive for minimizing kogation of the pigment. ### Claim 7 (depends on 6) The inkjet ink of claim 6, wherein the anti-kogation additive is selected from the group consisting of: 1 to 10 wt. % ethoxylated glycerol; 1 to 10 wt. % polyethylene glycol; 1 to 10 wt. % polyethylene glycol ethers; and 2 to 20 wt. % triethylene glycol. ### Claim 8 (depends on 1) The inkjet ink of claim 1, wherein the ink contains from 5 to 60 ppm ammonium ions. ### Claim 9 An inkjet printing system comprising: a printhead comprising a plurality of inkjet nozzle devices, each nozzle device comprising: a nozzle chamber and a heater element disposed on a subjacent silicon oxide pedestal; and an aqueous-based inkjet ink contained in the nozzle chamber, the inkjet ink comprising a pigment; 2 to 90 ppm ammonium ions; and an ink vehicle, wherein the ink has a pH in the range of 8 to 9.5. ### Claim 10 (depends on 9) The system of claim 9, wherein the heater element has a protective coating comprising at least one metal oxide layer. ### Claim 11 (depends on 10) The system of claim 10, wherein the protective coating has a thickness in the range of 5 to 50 nm. ### Claim 12 (depends on 11) The system of claim 11, wherein the protective coating comprises a layer of tantalum oxide. ### Claim 13 (depends on 9) The system of claim 9, wherein the heater element is comprised of an alumnide alloy. ### Claim 14 (depends on 9) The system of claim 9, wherein the nozzle chamber is comprised of silicon oxide. ### Claim 15 A method of printing from a thermal inkjet printhead, said printhead comprising a plurality of inkjet nozzle devices, each nozzle device comprising a nozzle chamber and a heater element disposed on a subjacent silicon oxide pedestal, said method comprising the steps of: supplying an aqueous-based inkjet ink from an ink reservoir to the nozzle chamber; and actuating the heater element so as to eject ink droplets from the nozzle chamber, wherein the ink comprises a pigment, 2 to 90 ppm ammonium ions and an ink vehicle, the ink having a pH in the range of 8 to 9.5. ### Claim 16 (depends on 15) The method of claim 15, wherein a pH of ink contained in the ink reservoir is higher than a pH of ink contained in the nozzle chamber during actuation of the heater element. ### Claim 17 An ink set for an inkjet printer having one or more printheads, each ink in the ink set having an associated printhead lifetime, wherein: a first ink contains a first pigment and 2 to 90 ppm ammonium ions; and a second ink contains a second pigment and a lower amount of ammonium ions than the first ink, and wherein: the first and second inks each have a pH in the range of 8 to 9.5; and the first and second inks each have an associated printhead lifetime of greater than a minimum threshold number of ejections. ### Claim 18 (depends on 17) The ink set of claim 17, wherein the second ink is absent any ammonium ions. ### Claim 19 (depends on 17) The ink set of claim 17, wherein the minimum threshold number of ejections is in the range of 2 to 8 billion. ### Claim 20 (depends on 17) The ink set of claim 17, wherein the first ink, when absent the ammonium ions, has an associated printhead lifetime of less than the minimum threshold number of ejections.