# US 5,467,176 A · Image forming method and apparatus with magnetic brush > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 5,467,176 A - Document ID: US5467176A - Status: Granted - Kind: A - Application number: 08/220,601 - Filed: 1994-03-30 - Granted: 1995-11-14 - Earliest claimed: 1993-06-24 - Assignees: Fujitsu Limited - Inventors: Tsuneo Watanuki; Yasushige Nakamura; Satoshi Takezawa; Norio Sawatari; Akira Nagahara; Sachio Sasaki; Mitsuru Sato; Shigenobu Utaka; Takefumi Takahashi; Masahiro Wanou; Masao Konishi - Web page: https://patentgrep.com/patent/US5467176A ## CPC - G03G 13/09: using magnetic brush - G03G 9/0806: {whereby chemical synthesis of at least one of the toner components takes place} - G03G 9/0825: {characterised by their structure; characterised by non-homogenuous distribution of components (microcapsular toners G03G9/093)} - G03G 9/0827: {characterised by their shape, e.g. degree of sphericity} - G03G 21/0064: {using the developing unit, e.g. cleanerless or multi-cycle apparatus} - G03G 2215/00012: Upright positioning as well as horizontal positioning for image forming - G03G 2215/0609: magnetic brush - G03G 2221/0005: Cleaning of residual toner - G03G: ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY ## Abstract An electrostatic latent image is developed on a latent image carrier and residual toners are collected at the same time. An electrostatic latent image is formed on a rotary endless latent image carrier; developer, including magnetic toners and magnetic carriers, is supplied to a developing area for developing the latent image carrier, and a magnetic brush is formed with the developer in the developing area to thereby collect residual toners on the latent image carrier and develop the electrostatic latent image on the latent image carrier; and the developed image on the latent image carrier is transferred to a sheet. An electrostatic latent image may be developed with a rotary endless latent image carrier; an image forming unit for forming an electrostatic latent image on the latent image carrier; a developing unit having a developer, including magnetic toners and magnetic carriers, and a developer supplying unit for supplying the developer to a developing area for developing the latent image carrier and forming a magnetic brush with the developer in the developing area in order to develop the electrostatic latent image on the latent image carrier with a powdery developer and collect residual toners on the latent image carrier; and a transfer unit for transferring the developed image on the latent image carrier to a sheet. ## Claims ### Claim 1 An image forming method for forming an image on a sheet, comprising the steps of: forming an electrostatic latent image on a rotary endless latent image carrier; forming a magnetic brush with a developer, comprising magnetic toners and magnetic carriers, in a developing area, for developing the electrostatic latent image on said latent image carrier, and thereby for collecting residual toners on said latent image carrier, a toner density of the developer in the formed magnetic brush being set to near a limiting toner density; and transferring said developed image on said latent image carrier to a sheet. ### Claim 2 (depends on 1) The image forming method according to claim 1, wherein said magnetic toners includes magnetic polymerization toners. ### Claim 3 (depends on 2) The image forming method according to claim 2, wherein said magnetic polymerization toners are associated particles containing resin particles, prepared as an essential substance by emulsion polymerization, and magnetic powder. ### Claim 4 (depends on 3) The image forming method according to claim 3, wherein said magnetic polymerization toners are prepared by aging a part of at least said resin particles in said associated particles. ### Claim 5 (depends on 2) The image forming method according to claim 2, wherein said magnetic polymerization toners have a volume average particle size d, a density .rho. and a specific surface area S in such a relation that 6/.rho..multidot.d.multidot.S lies in a range of 0.3 to 0.8 and d is between 5 to 12 .mu.m. ### Claim 6 An image forming method for forming an image on a sheet, comprising the steps of: forming an electrostatic latent image on a rotary endless latent image carrier; forming a magnetic brush with a developer, comprising magnetic toners and magnetic carriers, in a developing area, for developing the electrostatic latent image on said latent image carrier, and thereby for collecting residual toners on said latent image carrier, a toner density of the developer in the formed magnetic brush being set lower than a limiting toner density; and transferring said developed image on said latent image carrier to a sheet. ### Claim 7 (depends on 6) The image forming method according to claim 6, wherein said magnetic toners includes magnetic polymerization toners. ### Claim 8 (depends on 7) The image forming method according to claim 7, wherein said magnetic polymerization toners are associated particles containing resin particles, prepared as an essential substance by emulsion polymerization, and magnetic powder. ### Claim 9 (depends on 8) The image forming method according to claim 8, wherein said magnetic polymerization toners are prepared by aging a part of at least said resin particles in said associated particles. ### Claim 10 (depends on 7) The image forming method according to claim 7, wherein said magnetic polymerization toners have a volume average particle size d, a density .rho. and a specific surface area S in such a relation that 6/.rho..multidot.d.multidot.S lies in a range of 0.3 to 0.8 and d is between 5 to 12 .mu.m. ### Claim 11 An image forming method for forming an image on a sheet, comprising the steps of: forming an electrostatic latent image on a rotary endless latent image carrier; forming a magnetic brush with a developer, comprising magnetic polymerization toners and magnetic carriers, in a developing area, for developing the electrostatic latent image on said latent image carrier, and thereby for collecting residual toners on said latent image carrier; and transferring said developed image on said latent image carrier to a sheet. ### Claim 12 (depends on 11) The image forming method according to claim 11, wherein said magnetic polymerization toners used in said magnetic brush forming step are associated particles containing resin particles, prepared as an essential substance by emulsion polymerization, and magnetic power. ### Claim 13 (depends on 12) The image forming method according to claim 12, wherein said magnetic polymerization toners are prepared by aging a part of at least said resin particles in said associated particles. ### Claim 14 (depends on 12) The image forming method according to claim 12, wherein said magnetic polymerization toners have a volume average particle size d, a density .rho. and a specific surface area S in such a relation that 6/.rho..multidot.d.multidot.S lies in a range of 0.3 to 0.8 and d is between 5 to 12 .mu.m. ### Claim 15 An image forming method for forming an image on a sheet, comprising the steps of: forming an electrostatic latent image on a rotary endless latent image carrier; forming a magnetic brush with a developer, comprising magnetic toners and magnetic carriers, by developer supplying means including a magnetic field generating member having a plurality of magnetic poles, provided in a rotatable sleeve, in a developing area, for developing the electrostatic latent image on said latent image carrier, and thereby for collecting residual toners on said latent image carrier, a toner density of the developer in the formed magnetic brush being set to near a limiting toner density; and transferring said developed image on said latent image carrier to a sheet. ### Claim 16 An image forming method for forming an image on a sheet, comprising the steps of: forming an electrostatic latent image on rotary endless latent image carrier; forming a magnetic brush with a developer, comprising magnetic toners and magnetic carriers, by developer supplying means including a magnetic field generating member having a plurality of magnetic poles, provided in a rotatable sleeve, in a developing area, for developing the electrostatic latent image on said latent image carrier, and thereby for collecting residual toners on said latent image carrier, a toner density of the developer in the formed magnetic brush being set lower than a limiting toner density; and transferring said developed image on said latent image carrier to a sheet. ### Claim 17 An image forming method for forming an image on a sheet, comprising the steps of: forming an electrostatic latent image on a rotary endless latent image carrier; forming a magnetic brush with a developer, comprising magnetic polymerization toners and magnetic carriers, by developer supplying means including a magnetic field generating member having a plurality of magnetic poles, provided in a rotatable sleeve, in a developing area, for developing the electrostatic latent image on said latent image carrier, and thereby for collecting residual toners on said latent image carrier; and transferring said developed image on said latent image carrier to a sheet. ### Claim 18 (depends on 17) The image forming method according to claim 17, wherein said magnetic polymerization toners used in said magnetic brush forming step are associated particles containing resin particles, prepared as an essential substance by emulsion polymerization, and magnetic powder. ### Claim 19 (depends on 18) The image forming method according to claim 18, wherein said magnetic polymerization toners are prepared by aging a part of at least said resin particles in said associated particles. ### Claim 20 (depends on 17) The image forming method according to claim 17, wherein said magnetic polymerization toners have a volume average particle size d, a density .rho. and a specific surface area S in such a relation that 6/.rho..multidot.d.multidot.S lies in a range of 0.3 to 0.8 and d is between 5 to 12 .mu.m. ### Claim 21 An image forming apparatus for forming an image on a sheet, comprising: a rotary endless latent image carrier; image forming means for forming an electrostatic latent image on said latent image carrier; developing means including a developing room, and a rotatable sleeve and a fixed magnetic roller provided in the sleeve and having a plurality of magnetic poles in a circumferential direction of the fixed magnetic roller in the developing room, said developing means forming a magnetic brush with a developer comprising magnetic toners and magnetic carriers in the developing room, for developing the electrostatic latent image on said latent image carrier, and for collecting residual toners on said latent image carrier, a toner density of the developer in the developing room being set to near a limiting toner density; and transfer means for transferring said developed image on said latent image carrier to a sheet. ### Claim 22 (depends on 21) The image forming apparatus according to claim 21, wherein said developing room retains magnetic carriers by which said toner density becomes near said limiting toner density with respect to a developer retaining volume of said developing room. ### Claim 23 (depends on 21) The image forming apparatus according to claim 21, further comprising distribution means, provided between said transfer means and said image forming means, for distributing residual toners on said latent image carrier. ### Claim 24 An image forming apparatus for forming an image on a sheet, comprising: a rotary endless latent image carrier; image forming means for forming an electrostatic latent image on said latent image carrier; developing means including a developing room, and a rotatable sleeve and a fixed magnetic roller provided in the sleeve and having a plurality of magnetic poles in a circumferential direction of the fixed magnetic roller in the developing room, said developing means forming a magnetic brush with a developer comprising magnetic toners and magnetic carriers in the developing room, for developing the electrostatic latent image on said latent image carrier, and for collecting residual toners on said latent image carrier, a toner density of the developer in the developing room being set lower than a limiting toner density; and transfer means for transferring said developed image on said latent image carrier to a sheet. ### Claim 25 (depends on 24) The image forming apparatus according to claim 24, further comprising distribution means, provided between said transfer means and said image forming means, for distributing residual toners on said latent image carrier. ### Claim 26 An image forming apparatus for forming an image on a sheet, comprising: a rotary endless latent image carrier; image forming means for forming an electrostatic latent image on said latent image carrier; developing means for forming a magnetic brush with a developer comprising magnetic polymerization toners and magnetic carriers in a developing room, for developing the electrostatic latent image on said latent image carrier, and for collection of residual toners on said latent image carrier; and transfer means for transferring said developed image on said latent image carrier to a sheet. ### Claim 27 (depends on 26) The image forming apparatus according to claim 26, wherein said magnetic polymerization toners are associated particles containing resin particles, prepared as an essential substance by emulsion polymerization, and magnetic powder. ### Claim 28 (depends on 27) The image forming apparatus according to claim 27, wherein said magnetic polymerization toners are prepared by aging a part of at least said resin particles in said associated particles. ### Claim 29 (depends on 27) The image forming apparatus according to claim 27, wherein said magnetic polymerization toners have a volume average particle size d, a density .rho. and a specific surface area S in such a relation that 6/.rho..multidot.d.multidot.S lies in a range of 0.3 to 0.8 and d is between 5 to 12 .mu.m. ### Claim 30 (depends on 26) The image forming apparatus according to claim 26, further comprising distribution means, provided between said transfer means and said image forming means, for distributing residual toners on said latent image carrier. ### Claim 31 An image forming apparatus for forming an image on a sheet, comprising: a rotary endless latent image carrier; image forming means for forming an electrostatic latent image on said latent image carrier; developing means including a developing room for retaining a developer comprising magnetic toners and magnetic carriers, a toner supplying room for retaining magnetic toners to be supplied to the developing room, and magnetic brush forming means having a rotatable sleeve and a fixed magnetic roller provided in the sleeve and having a plurality of magnetic poles in a circumferential direction of the fixed magnetic roller in the developing room, said developing means forming a magnetic brush with a developer in the developing room, for developing the electrostatic latent image on said latent image carrier, and for collecting residual toners on said latent image carrier, a toner density of the developer in the developing room being set to near a limiting toner density; and transfer means for transferring said developed image on said latent image carrier to a sheet. ### Claim 32 (depends on 31) The image forming apparatus according to claim 31, wherein said developing room retains magnetic carriers by which said toner density becomes near said limiting toner density with respect to a developer retaining volume of said developing room. ### Claim 33 (depends on 31) The image forming apparatus according to claim 31, further comprising distribution means, provided between said transfer means and said image forming means, for distributing residual toners on said latent image carrier. ### Claim 34 (depends on 31) The image forming apparatus according to claim 31, further comprising partitioning means for partitioning said developing room and said toner supplying room to prevent moving the magnetic carriers from said developing room to said toner supplying room. ### Claim 35 An image forming apparatus for forming an image on a sheet, comprising: a rotary endless latent image carrier; image forming means for forming an electrostatic latent image on said latent image carrier; developing means including a developing room for retaining a developer comprising magnetic toners and magnetic carriers, a toner supplying room for retaining magnetic toners to be supplied to the developing room, and magnetic brush forming means having a rotatable sleeve and a fixed magnetic roller provided in the sleeve having a plurality of magnetic poles in a circumferential direction of the fixed magnetic roller in the developing room, said developing means forming a magnetic brush with a developer in the developing room, for developing the electrostatic latent image on said latent image carrier, and for collection of residual toners on said latent image carrier, a toner density of the developer in the developing room being set lower than a limiting toner density; and transfer means for transferring said developed image on said latent image carrier to a sheet. ### Claim 36 (depends on 35) The image forming apparatus according to claim 35, further comprising distribution means, provided between said transfer means and said image forming means, for distributing residual toners on said latent image carrier. ### Claim 37 (depends on 35) The image forming apparatus according to claim 35, further comprising partitioning means for partitioning said developing room and said toner supplying room to prevent moving the magnetic carriers from said developing room to said toner supplying room. ### Claim 38 An image forming apparatus for forming an image on a sheet, comprising: a rotary endless latent image carrier; image forming means for forming an electrostatic latent image on said latent image carrier; developing means including a developing room for retaining a developer comprising magnetic polymerization toners and magnetic carriers, and a toner supplying room for retaining the magnetic polymerization toners to be supplied to the developing room, said developing means forming a magnetic brush with a developer in the developing room, for developing the electrostatic latent image on said latent image carrier, and for collecting residual toners on said latent image carrier; and transfer means for transferring said developed image on said latent image carrier to a sheet. ### Claim 39 (depends on 38) The image forming apparatus according to claim 38, wherein said magnetic polymerization toners are associated particles containing resin particles, prepared as an essential substance by emulsion polymerization, and magnetic powder. ### Claim 40 (depends on 39) The image forming apparatus according to claim 39, wherein said magnetic polymerization toners are prepared by aging a part of at least said resin particles in said associated particles. ### Claim 41 (depends on 39) The image forming apparatus according to claim 39, wherein said magnetic polymerization toners have a volume average particle size d, a density .rho. and a specific surface area S in such a relation that 6/.rho..multidot.d.multidot.S lies in a range of 0.3 to 0.8 and d is between 5 to 12 .mu.m. ### Claim 42 (depends on 38) The image forming apparatus according to claim 38, further comprising distribution means, provided between said transfer means and said image forming means, for distributing residual toners on said latent image carrier. ### Claim 43 (depends on 38) The image forming apparatus according to claim 38, further comprising partitioning means for partitioning said developing room and said toner supplying room to prevent moving the magnetic carriers from said developing room to said toner supplying room. ### Claim 44 An image forming apparatus for forming an image on a sheet, comprising: a rotary endless latent image carrier; image forming means for forming an electrostatic latent image on said latent image carrier; developing means including a developing room retaining a developer comprising magnetic polymerization toners and magnetic carriers, and a developer supplying means including a rotatable sleeve and a magnetic field generating member provided in the sleeve and having a plurality of magnetic poles in a circumferential direction of the rotatable sleeve, said developing means forming a magnetic brush with a developer in the developing room, for developing the electrostatic latent image on said latent image carrier, and for collecting residual toners on said latent image carrier; and transfer means for transferring said developed image on said latent image carrier to a sheet. ### Claim 45 (depends on 44) The image forming apparatus according to claim 44, wherein said magnetic polymerization toners are associated particles containing resin particles, prepared as an essential substance by emulsion polymerization, and magnetic powder. ### Claim 46 (depends on 45) The image forming apparatus according to claim 45, wherein said magnetic polymerization toners are prepared by aging a part of at least said resin particles in said associated particles. ### Claim 47 (depends on 45) The image forming apparatus according to claim 45, wherein said magnetic polymerization toners have a volume average particle size d, a density .rho. and a specific surface area S in such a relation that 6/.rho..multidot.d.multidot.S lies in a range of 0.3 to 0.8 and d is between 5 to 12 .mu.m. ### Claim 48 (depends on 44) The image forming apparatus according to claim 44, further comprising distribution means, provided between said transfer means and said image forming means, for distributing residual toners on said latent image carrier. ### Claim 49 An image forming apparatus for forming an image on a sheet, comprising: a rotary endless latent image carrier; image forming means for forming an electrostatic latent image on said latent image carrier; developing means for forming a magnetic brush with a developer comprising magnetic toners and magnetic carriers in a developing room, for developing the electrostatic latent image on said latent image carrier with the magnetic brush, and for collecting residual toners on said latent image carrier with the magnetic brush, a toner density of the developer in the developing room being set lower than a limiting toner density; and transfer means for transferring said developed image on said latent image carrier to a sheet. ### Claim 50 (depends on 49) The image forming apparatus according to claim 49, further comprising partitioning means for partitioning said developing room and a toner supplying room to prevent moving the magnetic carriers from said developing room to said toner supplying room. ### Claim 51 (depends on 49) The image forming apparatus according to claim 49, further comprising distribution means, provided between said transfer means and image forming means, for distributing residual toners on said latent image carrier. ### Claim 52 (depends on 51) The image forming apparatus according to claim 51, wherein said magnetic toners are magnetic polymerization toners. ### Claim 53 (depends on 52) The image forming apparatus according to claim 52, further comprising partitioning means for partitioning said developing room and a toner supplying room to prevent moving the magnetic carriers from said developing room to said toner supplying room.