# US 8,787,804 B2 · Developing device including a developer container with toner particles and magnetic carrier particles (Rz=0.5−3.0 gm) and a developer bearing member (Rz=10−30 gm), and an image forming apparatus and process cartridge containing the same > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 8,787,804 B2 - Document ID: US8787804B2 - Status: Granted - Kind: B2 - Application number: 13/526,095 - Filed: 2012-06-18 - Published: 2013-01-03 - Granted: 2014-07-22 - Earliest claimed: 2011-06-29 - Assignees: Ricoh Company, Ltd. - Applicants: Hiroyuki Kishida; Shigenori Yaguchi; Toyoshi Sawada; Toyoaki Tano; Koichi Sakata - Inventors: Hiroyuki Kishida; Shigenori Yaguchi; Toyoshi Sawada; Toyoaki Tano; Koichi Sakata - Web page: https://patentgrep.com/patent/US8787804B2 ## CPC - G03G 15/0921: {Details concerning the magnetic brush roller structure, e.g. magnet configuration} - G03G 9/1075: {Structural characteristics of the carrier particles, e.g. shape or crystallographic structure} - G03G 9/1136: {containing silicon atoms} - G03G 9/1139: {Inorganic components of coatings} - G03G 9/00: Developers - G03G 2215/0609: magnetic brush - G03G: ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY ## Abstract A developing device including a developer container and a developer bearing member is provided. The developer container contains a two-component developer comprising toner particles and magnetic carrier particles having a ten-point average surface roughness Rz of 0.5 to 3.0 μm. The developer bearing member is a cylindrical member containing a magnetic field generator having multiple magnetic poles. The developer bearing member is adapted to bear the two-component developer on a surface thereof and to convey the two-component developer as the surface rotates. The developer bearing member has a ten-point average surface roughness Rz of 10 to 30 μm. The multiple magnetic poles include three developer bearing poles each adapted to generate a magnetic field having a strength enough for retaining the two-component developer on a surface of the developer bearing member. The three developer bearing poles consist of a developing pole, a pre-developing pole, and a post-developing pole. ## Claims ### Claim 1 A developing device, comprising: a developer container, the developer container containing a two-component developer, the two-component developer comprising toner particles and magnetic carrier particles, the magnetic carrier particles having a ten-point average surface roughness Rz of 0.5 to 3.0 μm; and a developer bearing member, the developer bearing member being a cylindrical member containing a magnetic field generator having multiple magnetic poles, the developer bearing member being adapted to bear the two-component developer on a surface thereof and to convey the two-component developer as the surface rotates, the developer bearing member having a ten-point average surface roughness Rz of 10 to 30 μm, wherein the multiple magnetic poles include three developer bearing poles each adapted to generate a magnetic field having a strength enough for retaining the two-component developer on a surface of the developer bearing member, and the three developer bearing poles consist of a developing pole, a pre-developing pole, and a post-developing pole, wherein the developing pole is adapted to generate a first magnetic field in a developing area in which the developer bearing member faces an electrostatic latent image bearing member, wherein the pre-developing pole is adapted to generate a second magnetic field, the second magnetic field supplying the two-component developer from the developer container to a surface of the developer bearing member and conveying the two-component developer to the developing area, the second and first magnetic fields retaining the two-component developer on a surface of the developer bearing member between a position where the two-component developer is supplied thereto and the developing area, and wherein the post-developing pole is adapted to generate a third magnetic field, the third magnetic field separating the two-component developer from the developer bearing member at a downstream side from the developing area and an upstream side from the developing pole relative to a direction of rotation of the developer bearing member, the first and third magnetic fields retaining the two-component developer on a surface of the developer bearing member between the developing area and a position where the two-component developer is separated therefrom. ### Claim 2 (depends on 1) The developing device according to claim 1, wherein each of the magnetic carrier particles includes: a core material; and a covering layer covering the core material, the covering layer including conductive fine particles, wherein the following formula is satisfied: 0.5≦(D/h)≦1.1 wherein D represents a volume average particle diameter of the conducive fine particles and h represents an average thickness of the covering layer. ### Claim 3 (depends on 2) The developing device according to claim 2, wherein the average thickness of the covering layer is 0.05 to 4 μm. ### Claim 4 An image forming apparatus, comprising: an electrostatic latent image bearing member; an electrostatic latent image forming device adapted to form an electrostatic latent image on the electrostatic latent image bearing member; a developing device adapted to develop the electrostatic latent image into a toner image with a two-component developer, the developing device including: a developer container, the developer container containing a two-component developer, the two-component developer comprising toner particles and magnetic carrier particles, the magnetic carrier particles having a ten-point average surface roughness Rz of 0.5 to 3.0 μm; and a developer bearing member, the developer bearing member being a cylindrical member containing a magnetic field generator having multiple magnetic poles, the developer bearing member being adapted to bear the two-component developer on a surface thereof and to convey the two-component developer as the surface rotates, the developer bearing member having a ten-point average surface roughness Rz of 10 to 30 μm, wherein the multiple magnetic poles include three developer bearing poles each adapted to generate a magnetic field having a strength enough for retaining the two-component developer on a surface of the developer bearing member, and the three developer bearing poles consist of a developing pole, a pre-developing pole, and a post-developing pole, wherein the developing pole is adapted to generate a first magnetic field in a developing area in which the developer bearing member faces the electrostatic latent image bearing member, wherein the pre-developing pole is adapted to generate a second magnetic field, the second magnetic field supplying the two-component developer from the developer container to a surface of the developer bearing member and conveying the two-component developer to the developing area, the second and first magnetic fields retaining the two-component developer on a surface of the developer bearing member between a position where the two-component developer is supplied thereto and the developing area, and wherein the post-developing pole is adapted to generate a third magnetic field, the third magnetic field separating the two-component developer from the developer bearing member at a downstream side from the developing area and an upstream side from the developing pole relative to a direction of rotation of the developer bearing member, the first and third magnetic fields retaining the two-component developer on a surface of the developer bearing member between the developing area and a position where the two-component developer is separated therefrom; and a transfer device adapted to transfer the toner image onto a recording medium; and a fixing device adapted to fix the toner image on the recording medium. ### Claim 5 (depends on 4) The image forming apparatus according to claim 4, wherein each of the magnetic carrier particles includes: a core material; and a covering layer covering the core material, the covering layer including conductive fine particles, wherein the following formula is satisfied: 0.5≦(D/h)≦1.1 wherein D represents a volume average particle diameter of the conducive fine particles and h represents an average thickness of the covering layer. ### Claim 6 (depends on 5) The image forming apparatus according to claim 5, wherein the average thickness of the covering layer is 0.05 to 4 μm. ### Claim 7 A process cartridge detachably attachable to image forming apparatus, comprising: an electrostatic latent image bearing member; and a developing device adapted to develop the electrostatic latent image into a toner image with a two-component developer, the developing device including: a developer container, the developer container containing a two-component developer, the two-component developer comprising toner particles and magnetic carrier particles, the magnetic carrier particles having a ten-point average surface roughness Rz of 0.5 to 3.0 μm; and a developer bearing member, the developer bearing member being a cylindrical member containing a magnetic field generator having multiple magnetic poles, the developer bearing member being adapted to bear the two-component developer on a surface thereof and to convey the two-component developer as the surface rotates, the developer bearing member having a ten-point average surface roughness Rz of 10 to 30 μm, wherein the multiple magnetic poles include three developer bearing poles each adapted to generate a magnetic field having a strength enough for retaining the two-component developer on a surface of the developer bearing member, and the three developer bearing poles consist of a developing pole, a pre-developing pole, and a post-developing pole, wherein the developing pole is adapted to generate a first magnetic field in a developing area in which the developer bearing member faces the electrostatic latent image bearing member, wherein the pre-developing pole is adapted to generate a second magnetic field, the second magnetic field supplying the two-component developer from the developer container to a surface of the developer bearing member and conveying the two-component developer to the developing area, the second and first magnetic fields retaining the two-component developer on a surface of the developer bearing member between a position where the two-component developer is supplied thereto and the developing area, and wherein the post-developing pole is adapted to generate a third magnetic field, the third magnetic field separating the two-component developer from the developer bearing member at a downstream side from the developing area and an upstream side from the developing pole relative to a direction of rotation of the developer bearing member, the first and third magnetic fields retaining the two-component developer on a surface of the developer bearing member between the developing area and a position where the two-component developer is separated therefrom. ### Claim 8 (depends on 7) The process cartridge according to claim 7, wherein each of the magnetic carrier particles includes: a core material; and a covering layer covering the core material, the covering layer including conductive fine particles, wherein the following formula is satisfied: 0.5≦(D/h)≦1.1 wherein D represents a volume average particle diameter of the conducive fine particles and h represents an average thickness of the covering layer. ### Claim 9 (depends on 8) The process cartridge according to claim 8, wherein the average thickness of the covering layer is 0.05 to 4 μm. ### Claim 10 (depends on 1) The developing device according to claim 1, wherein the developer bearing member having a ten-point average surface roughness Rz of 15 to 30 μm. ### Claim 11 (depends on 2) The developing device according to claim 2, wherein the following formula is satisfied: 0.5≦(D/h)≦0.9.