# US 12,181,836 B2 · Electrostatic charge image developing carrier, 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 12,181,836 B2 - Document ID: US12181836B2 - Status: Granted - Kind: B2 - Application number: 17/386,211 - Filed: 2021-07-27 - Published: 2022-09-29 - Granted: 2024-12-31 - Earliest claimed: 2021-03-23 - Assignees: FUJIFILM Business Innovation Corp. - Applicants: FUJIFILM Business Innovation Corp. - Inventors: Yasuo Kadokura; Yosuke Tsurumi; Takuro Watanabe; Kazutsuna Sasaki; Karin Sakai - Web page: https://patentgrep.com/patent/US12181836B2 ## 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 9/107: having magnetic components - G03G 9/1085: {with non-ferrous metal oxide, e.g. MgO-Fe2O3} - G03G 9/1131: {Coating methods; Structure of coatings} - G03G 9/1132: {Macromolecular components of coatings} - G03G 9/1133: {obtained by reactions only involving carbon-to-carbon unsaturated bonds} - G03G 9/1134: {containing fluorine atoms} - G03G: ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY ## Abstract An electrostatic charge image developing carrier, contains: a magnetic particle; and a coating resin layer coating the magnetic particle and containing inorganic particles, in which an area ratio of the inorganic particles that is a ratio of a total area of the inorganic particles to an area of the coating resin layer in a cut surface of the coating resin layer along a thickness direction of the coating resin layer is 10% or more and 50% or less. ## Claims ### Claim 1 An electrostatic charge image developing carrier, comprising: a magnetic particle; and a coating resin layer coating the magnetic particle and containing inorganic particles, wherein an area ratio of the inorganic particles that is a ratio of a total area of the inorganic particles to an area of the coating resin layer in a cut surface of the coating resin layer along a thickness direction of the coating resin layer is 10% or more and 50% or less; a content of the inorganic particles is 18 mass % or more and 40 mass % or less with respect to a resin contained in the coating resin layer; and an average particle diameter of the inorganic particles is 5 nm or more and 40 nm or less. ### Claim 2 (depends on 1) The electrostatic charge image developing carrier according to claim 1, wherein in the cut surface, an average of distances between centers of gravity of the inorganic particles is 200 nm or less, each of the distances between centers of gravity of the inorganic particles being a distance between centers of gravity of a pair of two particles of the inorganic particles, one particle of the pair being farthest from the other particle of the pair without interposing any particle of the inorganic particles other than the pair of the two particles. ### Claim 3 (depends on 1) The electrostatic charge image developing carrier according to claim 1, wherein an average particle diameter of the inorganic particles is smaller than an average thickness of the coating resin layer. ### Claim 4 (depends on 2) The electrostatic charge image developing carrier according to claim 2, wherein an average particle diameter of the inorganic particles is smaller than an average thickness of the coating resin layer. ### Claim 5 (depends on 3) The electrostatic charge image developing carrier according to claim 3, wherein a ratio of the average particle diameter of the inorganic particles to the average thickness of the coating resin layer is 0.005 or more and 0.15 or less. ### Claim 6 (depends on 4) The electrostatic charge image developing carrier according to claim 4, wherein a ratio of the average particle diameter of the inorganic particles to the average thickness of the coating resin layer is 0.005 or more and 0.15 or less. ### Claim 7 (depends on 3) The electrostatic charge image developing carrier according to claim 3, wherein the average thickness of the coating resin layer is 0.6 μm or more and 1.4 μm or less. ### Claim 8 (depends on 1) The electrostatic charge image developing carrier according to claim 1, wherein the inorganic particles are inorganic oxide particles. ### Claim 9 (depends on 1) The electrostatic charge image developing carrier according to claim 1, wherein the content of the inorganic particles is 20 mass % or more and 30 mass % or less with respect to the resin contained in the coating resin layer. ### Claim 10 (depends on 1) The electrostatic charge image developing carrier according to claim 1, wherein a weight average molecular weight of the resin contained in the coating resin layer is less than 300,000. ### Claim 11 (depends on 10) The electrostatic charge image developing carrier according to claim 10, wherein the weight average molecular weight of the resin contained in the coating resin layer is less than 250,000. ### Claim 12 (depends on 1) An electrostatic charge image developer, comprising: an electrostatic charge image developing toner; and the electrostatic charge image developing carrier according to claim 1. ### Claim 13 (depends on 12) The electrostatic charge image developer according to claim 12, wherein the electrostatic charge image developing toner includes an external additive having the same charge polarity as the inorganic particles of the electrostatic charge image developing carrier. ### Claim 14 (depends on 12) 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 12, 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 15 (depends on 12) 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 12, 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 16 (depends on 12) 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 12; 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. ### Claim 17 (depends on 1) The electrostatic charge image developing carrier according to claim 1, wherein the resin layer contains an acrylic resin having an alicyclic structure. ### Claim 18 (depends on 1) The electrostatic charge image developing carrier according to claim 1, wherein the resin layer contains cyclohexyl (meth)acrylate as a polymerization component.