# US 12,169,390 B2 · Electrostatic charge image developer, process cartridge, image forming apparatus, and image forming method > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 12,169,390 B2 - Document ID: US12169390B2 - Status: Granted - Kind: B2 - Application number: 17/404,623 - Filed: 2021-08-17 - Published: 2022-11-24 - Granted: 2024-12-17 - Earliest claimed: 2021-05-20 - Assignees: FUJIFILM Business Innovation Corp. - Applicants: FUJIFILM Business Innovation Corp. - Inventors: Yasuo Kadokura; Takuro Watanabe; Karin Sakai; Kazutsuna Sasaki; Yosuke Tsurumi - Web page: https://patentgrep.com/patent/US12169390B2 ## CPC - G03G 9/108: {Ferrite carrier, e.g. magnetite} - G03G 9/1139: {Inorganic components of coatings} - G03G 9/0819: {characterised by the dimensions of the particles} - G03G 9/0821: {characterised by physical parameters (magnetic parameters G03G9/083)} - G03G 9/0827: {characterised by their shape, e.g. degree of sphericity} - G03G 9/08795: {characterised by their chemical properties, e.g. acidity, molecular weight, sensitivity to reactants} - G03G 9/08797: {characterised by their physical properties, e.g. viscosity, solubility, melting temperature, softening temperature, glass transition temperature} - G03G 9/09725: {Silicon-oxides; Silicates} - G03G 9/1131: {Coating methods; Structure of coatings} - G03G 9/1133: {obtained by reactions only involving carbon-to-carbon unsaturated bonds} - G03G 9/1134: {containing fluorine atoms} - G03G 15/08: using a solid developer, e.g. powder developer - G03G 21/1814: {Details of parts of process cartridge, e.g. for charging, transfer, cleaning, developing (G03G21/1835 takes precedence)} - G03G: ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY ## Abstract An electrostatic charge image developer containing: a toner containing a toner particle and an external additive; and a carrier containing a magnetic particle and a resin layer covering the magnetic particle, in which the toner particle has a surface property index value of 2.0 or more and 2.8 or less; and the carrier has a surface having a ratio B/A of a surface area B to a planar view area A of 1.020 or more and 1.100 or less, the planar view area A and the surface area B being obtained by three-dimensional analysis of the surface of the carrier. ## Claims ### Claim 1 An electrostatic charge image developer comprising: a toner containing a toner particle and an external additive; and a carrier containing a magnetic particle and a resin layer covering the magnetic particle, wherein the toner particle has a surface property index value of 2.0 or more and 2.8 or less, the carrier has a surface having a ratio B/A of a surface area B to a planar view area A of 1.020 or more and 1.100 or less, the planar view area A and the surface area B being obtained by three-dimensional analysis of the surface of the carrier, the resin layer contains inorganic particles having an average particle diameter of 4 nm or more and 93 nm or less, a content of the inorganic particles contained in the resin layer is 10 mass % or more and 60 mass % or less, and average thickness of the resin layer is 0.5 μm or more and 1.5 μm or less. ### Claim 2 (depends on 1) The electrostatic charge image developer according to claim 1, wherein the surface property index value is 2.1 or more and 2.6 or less. ### Claim 3 (depends on 1) The electrostatic charge image developer according to claim 1, wherein the ratio B/A is 1.040 or more and 1.080 or less. ### Claim 4 (depends on 2) The electrostatic charge image developer according to claim 2, wherein the ratio B/A is 1.040 or more and 1.080 or less. ### Claim 5 (depends on 1) The electrostatic charge image developer according to claim 1, wherein the resin layer contains inorganic particles having an average particle diameter of 5 nm or more and 90 nm or less. ### Claim 6 (depends on 2) The electrostatic charge image developer according to claim 2, wherein the resin layer contains inorganic particles having an average particle diameter of 5 nm or more and 90 nm or less. ### Claim 7 (depends on 3) The electrostatic charge image developer according to claim 3, wherein the resin layer contains inorganic particles having an average particle diameter of 5 nm or more and 90 nm or less. ### Claim 8 (depends on 4) The electrostatic charge image developer according to claim 4, wherein the resin layer contains inorganic particles having an average particle diameter of 5 nm or more and 90 nm or less. ### Claim 9 (depends on 5) The electrostatic charge image developer according to claim 5, wherein the average particle diameter of the inorganic particles is 5 nm or more and 70 nm or less. ### Claim 10 (depends on 6) The electrostatic charge image developer according to claim 6, wherein the average particle diameter of the inorganic particles is 5 nm or more and 70 nm or less. ### Claim 11 (depends on 7) The electrostatic charge image developer according to claim 7, wherein the average particle diameter of the inorganic particles is 5 nm or more and 70 nm or less. ### Claim 12 (depends on 1) The electrostatic charge image developer according to claim 1, wherein the resin layer has an average thickness of 0.6 μm or more and 1.4 μm or less. ### Claim 13 (depends on 12) The electrostatic charge image developer according to claim 12, wherein the average thickness of the resin layer is 0.8 μm or more and 1.2 μm or less. ### Claim 14 (depends on 1) The electrostatic charge image developer according to claim 1, wherein the toner has a storage elastic modulus G′ of 6.0×108 Pa or more and 1.5×109 Pa or less at a temperature of 30° C. in dynamic viscoelasticity measurement. ### Claim 15 (depends on 14) The electrostatic charge image developer according to claim 14, wherein the storage elastic modulus G′ is 8.0×108 Pa or more and 1.2×109 Pa or less. ### Claim 16 (depends on 1) The electrostatic charge image developer according to claim 1, wherein the resin layer contains silica particles, and has a silicon element concentration of more than 2 atomic % and less than 20 atomic % at the surface of the carrier, the silicon element concentration being determined by X-ray photoelectron spectroscopy. ### Claim 17 (depends on 1) The electrostatic charge image developer according to claim 1, wherein the resin layer comprises a resin having a weight average molecular weight of less than 300,000. ### Claim 18 (depends on 1) A process cartridge configured to be attached to and detached from an image forming apparatus, the process cartridge comprising: a developing unit that accommodates the electrostatic charge image developer according to claim 1, and is configured to develop an electrostatic charge image as a toner image by the electrostatic charge image developer, the electrostatic charge image being formed on a surface of an image carrier. ### Claim 19 (depends on 1) An image forming apparatus comprising: an image carrier; a charging unit configured to charge a surface of the image carrier; an electrostatic charge image forming unit configured to form an electrostatic charge image on the surface of the image carrier charged; a developing unit that accommodates the electrostatic charge image developer according to claim 1, and is configured to develop the electrostatic charge image as a toner image by the electrostatic charge image developer; a transfer unit configured to transfer the toner image formed on the surface of the image carrier to a surface of a recording medium; and a fixing unit configured to fix the toner image transferred to the surface of the recording medium. ### Claim 20 (depends on 1) An image forming method comprising: charging a surface of an image carrier; forming an electrostatic charge image on the surface of the image carrier charged; developing the electrostatic charge image as a toner image by the electrostatic charge image developer according to claim 1; transferring the toner image formed on the surface of the image carrier to a surface of a recording medium; and fixing the toner image transferred to the surface of the recording medium.