# US 2008/0187338 A1 · Image forming apparatus > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2008/0187338 A1 - Document ID: US20080187338A1 - Status: Published application - Kind: A1 - Application number: 12/022,575 - Filed: 2008-01-30 - Published: 2008-08-07 - Earliest claimed: 2007-02-02 - Assignees: Canon Kabushiki Kaisha - Inventors: Takeshi Yamamoto; Manami Haraguchi; Kenta Kubo; Yoshinobu Baba; Koh Ishigami - Web page: https://patentgrep.com/patent/US20080187338A1 ## CPC - G03G 15/065: {Arrangements for controlling the potential of the developing electrode} - G03G 5/04: Photoconductive layers; Charge-generation layers or charge-transporting layers; Additives therefor; Binders therefor - G03G 15/0806: {on a donor element, e.g. belt, roller (complete developer unit G03G15/0896)} - G03G 15/5037: {the characteristics being an electrical parameter, e.g. voltage} - G03G 15/5062: {by measuring the characteristics of an image on the copy material} - G03G 2215/00037: Toner image detection - G03G 2215/0607: two-component - G03G: ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY ## Abstract An image forming apparatus, wherein the following formulae are satisfied: 0.22 ≤ ( M / S ) L ≤ 0.4 ,  ( Q M ) L = Vc ( Lt 2  ɛ 0  ɛ t + Ld ɛ 0  ɛ d ) × ( M S ) L ( Dt   max - Dt 0.1 ) { λ × ( M S ) L - 0.1 }  ( Lt 2  ɛ 0  ɛ t + Ld ɛ 0  ɛ d ) × ( M S ) L 500 ≤ αβ ≤ ( Dt   max - Dt 0.1 ) { λ × ( M S ) L - 0.1 }  ( Lt 2  ɛ 0  ɛ t + Ld ɛ 0  ɛ d ) × ( M S ) L 150 αβ ≥ ( Dt   max - Dt 0.1 ) { λ × ( M S ) L - 0.1 } 150 where (M/S)L: a toner bearing amount in a maximum density image portion of a photosensitive drum, (Q/M)L: an average charge amount of the toner in the maximum density portion, Vc: an absolute value of a potential difference between a DC-component of a developing bias and the maximum density portion, Lt: a toner layer thickness of the maximum density portion, Ld: a drum thickness, εt: a relative permittivity of the toner layer, εd: a relative permittivity of the drum, ε0: a vacuum permittivity, Dtmax: a transmission density in a maximum density image portion on the paper after fixation, Dt0.1: a transmission density in an image on the paper when the toner bearing amount on the paper after fixation is 0.1 mg/cm2, and λ: a transfer efficiency of the toner, α = ( Dt   max - Dt 0.1 ) { λ × ( M S ) L - 0.1 } ,  and   β = 1 / ( Q / M ) L . ## Claims ### Claim 1 An image forming apparatus, comprising: a photosensitive member; a developing device which develops an electrostatic image formed on the photosensitive member with a developer having a toner and a carrier, the developing device including a developer carrying member which carries and conveys the developer to a developing position; a transfer device which transfers a toner image formed on the photosensitive member to a transfer material; and a fixing device which fixes the toner image on the transfer material to the transfer material, wherein assuming that a toner bearing amount in a maximum density image portion of the photosensitive member is (M/S)L [mg/cm2], an average charge amount of the toner in the maximum density image portion of the photosensitive member is (Q/M)L [μC/g], an absolute value of a potential difference between a potential of a DC-component of a developing bias applied to the developer carrying member and a potential of the maximum density image portion on the photosensitive member is Vc [V], a toner layer thickness of the maximum density image portion on the photosensitive member is Lt [μm], a thickness of the photosensitive member is Ld [μm], a relative permittivity of the toner layer is εt, a relative permittivity of the photosensitive member is εd, a permittivity in vacuum is ε0, a transmission density in a maximum density image portion on the transfer material after being fixed by the fixing device is ⊃tmax, a transmission density in an image portion on the transfer material when the toner bearing amount on the transfer material after being fixed by the fixing device is 0.1 mg/cm2 is Dt0.1, and a transfer efficiency of the toner from the photosensitive member onto the transfer material is λ, the following formulae are satisfied: 0.22<(M/S)L≦0.4, ( Q M ) L = Vc ( Lt 2  ɛ 0  ɛ t + Ld ɛ 0  ɛ d ) × ( M S ) L , and assuming that α = ( Dt   max - Dt 0.1 ) { λ × ( M S ) L - 0.1 } , and β=1/(Q/M)L, the following formulae are satisfied: ( Dt   max - Dt 0.1 ) { λ × ( M S ) L - 0.1 }  ( Lt 2  ɛ 0  ɛ t + Ld ɛ 0  ɛ d ) × ( M S ) L 500 ≤ αβ ≤ ( Dt   max - Dt 0.1 ) { λ × ( M S ) L - 0.1 }  ( Lt 2  ɛ 0  ɛ t + Ld ɛ 0  ɛ d ) × ( M S ) L 150  αβ = ( Dt   max - Dt 0.1 ) { λ × ( M S ) L - 0.1 } 150 . ### Claim 2 (depends on 1) An image forming apparatus according to claim 1, wherein an average particle diameter of the toner is 5.0 μm or more. ### Claim 3 (depends on 1) An image forming apparatus according to claim 1, wherein a capacitance C of the photosensitive member satisfies the following formula: 0.7×10−6 [F/m2]