# US 7,608,646 B1 · Polymer-encapsulated pigment with bridging layer > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 7,608,646 B1 - Document ID: US7608646B1 - Status: Granted - Kind: B1 - Application number: 11/414,099 - Filed: 2006-04-28 - Granted: 2009-10-27 - Earliest claimed: 2006-04-28 - Assignees: Hewlett-Packard Development Company, L.P. - Inventors: Sivapackia Ganapathiappan; Kent D. Vincent - Web page: https://patentgrep.com/patent/US7608646B1 ## CPC - C09D 11/322: Pigment inks - C09D 11/326: characterised by the pigment dispersant - Y10T 428/2998: including synthetic resin or polymer - 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) - Y10T: TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION ## Abstract The present invention is drawn to pigment suspensions, methods of forming pigment suspensions, and ink sets. The pigment suspension can comprise an aqueous liquid vehicle and a polymer-encapsulated pigment suspended in the liquid vehicle. The polymer-encapsulated pigment can include a pigment core, a bridging layer deposited on a surface of the pigment core, and a polymer encapsulation layer attached to or deposited on the bridging layer. ## Claims ### Claim 1 A pigment suspension, comprising: a) an aqueous liquid vehicle; and b) a polymer-encapsulated pigment suspended in the liquid vehicle, said polymer-encapsulated pigment including a pigment core, a bridging layer deposited on a surface of the pigment core, and a polymer encapsulation layer attached to or deposited on the bridging layer; wherein the bridging layer is formed from a bridging component that is soluble in solution, and comes out of solution and becomes deposited on the pigment core upon raising the pH or raising the temperature; or wherein the bridging layer is formed from a bridging component that is soluble in solution and comes out of solution and becomes deposited on the pigment core upon lowering the pH or lowering the temperature. ### Claim 2 (depends on 1) A pigment suspension as in claim 1, wherein the pigment core is a pigment colorant, and the pigment suspension is an inkjet ink. ### Claim 3 (depends on 1) A pigment suspension as in claim 1, wherein the bridging layer is formed from a bridging component that is water soluble at a temperature from 10° C. to 60° C., and is water insoluble at a temperature from 20° C. to 90° C. ### Claim 4 (depends on 1) A pigment suspension as in claim 1, wherein the bridging layer is formed of one or more polyalkylacrylamide. ### Claim 5 (depends on 1) A pigment suspension as in claim 1, wherein the bridging layer is formed from a bridging component that is water soluble at a pH from 1 to 7, and is water insoluble at a pH from 5 to 10. ### Claim 6 (depends on 1) A pigment suspension as in claim 1, wherein the bridging layer is formed of a member selected from the group consisting of poly((2-methacryloyloxy)ethyl phosphorylcholine-block-2-(diisopropylamino)ethyl methacrylate); poly((2-methacrylyoyloxy)ethyl phosphorylcholine-co-2-(diisopropylamino)ethyl acrylate); poly((2-acrylyoyloxy)ethyl phosphorylcholine-co-2-(diisopropylamino)ethyl acrylate); poly((2-acrylyoyloxy)ethyl phosphorylcholine-co-2-(diisopropylamino)ethyl methacrylate); poly(vinylimidazole-co-methacrylic acid); poly(vinylimidazole-co-acrylic acid); poly(methoxypolyethyleneglycol methacrylate of mol. wt. from 200 to 5000-co-methacrylic acid; poly(methoxypolyethyleneglycol of mol. wt. from 200 to 5000 methacrylate-co-acrylic acid); poly((2-diisopropylamino)ethyl methacrylate-co-methacrylic acid); poly((2-diisopropylamino)ethyl methacrylate-co-acrylic acid); poly(vinylpyrrolidone-co-acrylic acid); and poly(vinylpyrrolidone-co-methacrylic acid); and combinations thereof. ### Claim 7 (depends on 1) A pigment suspension as in claim 1, wherein the polymer-encapsulated pigment has bulk density from 0.90 g/cm3 to 1.10 g/cm3 and a surface dielectric constant from 2.0 to 3.0 at room temperature, wherein the polymer encapsulation layer comprises randomly assembled copolymers including from 0.5 wt % to 20 wt % of an acidic monomer, and wherein the acidic monomer present at the surface of the polymer-encapsulated pigment is neutralized after polymerization. ### Claim 8 (depends on 1) A pigment suspension as in claim 1, wherein the polymer encapsulation layer is crosslinked by a crosslinking agent present at from 0.5 wt % to 5 wt %. ### Claim 9 (depends on 1) A pigment suspension as in claim 1, wherein the polymer encapsulation layer has a glass transition temperature from 0° C. to 50° C. ### Claim 10 (depends on 1) A pigment suspension as in claim 1, wherein the polymer layer includes copolymerized monomers formed in situ at the bridging layer such that the polymer layer is covalently attached to or deposited on the bridging layer. ### Claim 11 (depends on 1) A pigment suspension as in claim 1, wherein the polymer layer includes copolymerized monomers formed outside of the aqueous vehicle and is subsequently covalently attached to or deposited on the bridging layer. ### Claim 12 (depends on 1) A pigment suspension as in claim 1, wherein the polymer-encapsulated pigment is from 200 nm to 300 nm in diameter. ### Claim 13 A method of making a polymer-encapsulated pigment, comprising: a) dispersing a pigment in a liquid; b) dissolving a bridging component in the liquid to form a solubilized bridging component; c) changing a property of the liquid to thereby cause at least a portion of the solubilized bridging component to become a desolubilized bridging component deposited on a surface of the pigment in the form of a bridging layer; and d) attaching or depositing a polymer to the bridging layer. ### Claim 14 (depends on 13) A method as in claim 13, wherein steps a) to d) are sequential. ### Claim 15 (depends on 13) A method as in claim 13, wherein the property of the liquid that is changed is temperature, the bridging component is thermally sensitive with respect to solubility, and the bridging layer is formed upon raising or lowering the temperature of the liquid. ### Claim 16 (depends on 13) A method as in claim 13, wherein the property of the liquid that is changed is pH, the bridging component is pH sensitive with respect to solubility, and the bridging layer is formed upon raising or lowering the pH of the liquid. ### Claim 17 (depends on 13) A method as in claim 13, wherein the step of attaching or depositing the polymer to the desolubilized bridging component includes polymerizing monomers at the surface of the desolubilized bridging component. ### Claim 18 (depends on 13) A method as in claim 13, wherein the step of attaching or depositing the polymer to the desolubilized bridging component includes forming a polymer followed by attaching or depositing the polymer to the surface of the desolubilized bridging component. ### Claim 19 (depends on 13) A method as in claim 13, wherein the desolubilized bridging component is a passivation layer, which modifies properties at the surface of the pigment colorant, thereby allowing for improved polymer attachment or deposition compared to attachment or deposition without the passivation layer. ### Claim 20 (depends on 13) A method as in claim 13, wherein the bridging layer is applied when its surface tension is greater than that of the pigment, and wherein step of attaching or depositing the polymer to the bridging layer occurs after the surface tension of the bridging layer is brought below or drops below the surface tension of the pigment. ### Claim 21 An ink set, comprising: a) a first ink-jet ink, comprising: i) a first aqueous liquid vehicle, and ii) a first polymer-encapsulated pigment colorant suspended in the first liquid vehicle, said first polymer-encapsulated pigment colorant including a first pigment core, a first bridging layer deposited on a surface of the pigment core, and a first polymer encapsulation layer attached or deposited on the first bridging layer; and b) a second ink-jet ink, comprising: i) a second aqueous liquid vehicle, and ii) a second polymer-encapsulated pigment colorant suspended in the second liquid vehicle, said second polymer-encapsulated pigment colorant including a second pigment core, a second bridging layer deposited on a surface of the second pigment core, and a second polymer encapsulation layer attached or deposited on the bridging layer, wherein the first pigment core and the second pigment core are different pigment colorants, the first bridging layer and the second bridging layer are formed of the same material, and the first polymer encapsulation layer and the second polymer encapsulation layer are formed of the same material, and wherein i) the first and second bridging layers are formed from a respective first and second bridging component that are soluble in solution, and come out of solution and become deposited on the first and second pigment cores, respectively, upon raising the pH or raising the temperature; or wherein ii) the first and second bridging layers are formed from a respective first and second bridging component that are soluble in solution, and come out of solution and become deposited on the first and second pigment cores, respectively, upon lowering the pH or lowering the temperature. ### Claim 22 (depends on 21) An ink set as in claim 21, wherein at least each of a cyan, a magenta, and a yellow pigment in the ink set have bridging layers formed of the same material and polymer encapsulation layers formed of the same materials.