US5262267A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Magnetic developer, image forming method and image forming apparatus
Assignee: Canon Inc
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Filing: 1992-03-09
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Granted: 1993-11-16
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Expires: 2012-03-09
Abstract
Abstract A magnetic developer for developing an electrostatic latent image, including hydrophobic silica fine powder and an insulating magnetic toner comprising at least a binder resin and a magnetic material comprising spherical magnetic particles; wherein 0.16 to 1.6 wt. parts of the hydrophobic silica fine powder is mixed with 100 wt. parts of the insulating magnetic toner; the developer contains 17-60% by number of magnetic toner particles having a particle size of 5 microns or smaller, 5-50% by number of magnetic toner particles having a particle size of 6.35-10.08 microns, and 2.0% by volume or less of magnetic toner particles having a particle size of 12.7 microns or larger.
Inventors
- 👤 Tsuyoshi Takiguchi
- 👤 Tetsuya Kuribayashi
- 👤 Koichi Tomiyama
- 👤 Tsutomu Kukimoto
- 👤 Hiroshi Yusa
- 👤 Eiichi Imai
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-09 06:13
CPC Classifications
G; G03; G03G; G03G13/00; G03G13/06; G03G13/08; G03G13/09; G03G9/00; G03G9/08; G03G9/0819; G03G9/0821; G03G9/0823; G03G9/083; G03G9/0837; G03G9/0838; G03G9/097
Claims Analysis
Total Claims: 19
Claim 1
Independent Claim
307 words
An image forming method comprising: (a) disposing an electrostatic image-bearing member carrying thereon an electrostatic image, and a toner-carrying member carrying a magnetic toner on the surface thereof with a predetermined clearance therebetween, wherein the toner-carrying member has a surface covered with a film of phenolic resin containing electroconductive carbon and graphite; and the magnetic toner comprises an insulating one-component magnetic toner comprising at least a binder resin and a magnetic material; and the magnetic toner has a triboelectric chargeability of -20 to -35 μC/g and a volume-average particle size of 6-8 microns; said magnetic material comprising at least 50% by number of spherical magnetic particles having surface which substantially comprise curved surfaces; said toner containing 17-60% by number of magnetic toner particles having a particle size of no greater than 5 microns, containing 5-50% by number of magnetic toner particles having a particle size of 6.35-10.08 microns, and containing no greater than 2.0% by volume of magnetic toner particles having a particle size of at least 12.7 microns; wherein the magnetic toner particles having a particle size of no greater than 5 microns have a particle size distribution satisfying the following formula: N/V=-0.05N+K, wherein N is the percentage by number of magnetic toner particles having a particle size of no greater than 5 microns, V is the percentage by volume of magnetic toner particles having a particle size of no greater than 5 microns, k is a positive number of 4.6-6.7, and N is a positive number of 17-60; (b) conveying the magnetic toner to a developing position while regulating the toner so as to provide a thickness smaller than said clearance; and (c) developing the electrostatic image formed on the image-bearing member in the developing position in the presence of an alternating electric field, thereby to form a toner image on the latent image-bearing member.
Claim 2
Dependent Claim
307 words
An image forming method comprising: (a) disposing an electrostatic image-bearing member carrying thereon an electrostatic image, and a toner-carrying member carrying a magnetic toner on the surface thereof with a predetermined clearance therebetween, wherein the toner-carrying member has a surface covered with a film of phenolic resin containing electroconductive carbon and graphite; and the magnetic toner comprises an insulating one-component magnetic toner comprising at least a binder resin and a magnetic material; and the magnetic toner has a triboelectric chargeability of -20 to -35 μC/g and a volume-average particle size of 6-8 microns; said magnetic material comprising at least 50% by number of spherical magnetic particles having surface which substantially comprise curved surfaces; said toner containing 17-60% by number of magnetic toner particles having a particle size of no greater than 5 microns, containing 5-50% by number of magnetic toner particles having a particle size of 6.35-10.08 microns, and containing no greater than 2.0% by volume of magnetic toner particles having a particle size of at least 12.7 microns; wherein the magnetic toner particles having a particle size of no greater than 5 microns have a particle size distribution satisfying the following formula: N/V=-0.05N+K, wherein N is the percentage by number of magnetic toner particles having a particle size of no greater than 5 microns, V is the percentage by volume of magnetic toner particles having a particle size of no greater than 5 microns, k is a positive number of 4.6-6.7, and N is a positive number of 17-60; (b) conveying the magnetic toner to a developing position while regulating the toner so as to provide a thickness smaller than said clearance; and (c) developing the electrostatic image formed on the image-bearing member in the developing position in the presence of an alternating electric field, thereby to form a toner image on the latent image-bearing member.
Claim 3
Dependent Claim
20 words
A method according to claim 1, wherein the electroconductive carbon has an electric resistance of no greater than 0.5 ohm/cm.
Claim 4
Dependent Claim
26 words
A method according to claim 1, wherein the electroconductive carbon and graphite are present so as to provide a mixing weight ratio of 1/10 to 100/1.
Claim 5
Dependent Claim
26 words
A method according to claim 1, wherein the electroconductive carbon and graphite are present so as to provide a mixing weight ratio of 1/1 to 100/1.
Claim 6
Dependent Claim
34 words
A method according to claim 1, wherein the mixture of the electroconductive carbon and graphite is contained in the phenolic resin so as to provide a mixing weight ratio of 1/3 to 2/1 therebetween.
Claim 7
Dependent Claim
17 words
A method according to claim 1, wherein the magnetic toner is admixed with hydrophobic silica fine powder.
Claim 8
Dependent Claim
23 words
A method according to claim 6, wherein the hydrophobic silica fine powder has been treated with a silicone oil or a silicone varnish.
Claim 9
Dependent Claim
20 words
A method according to claim 6, wherein the hydrophobic silica fine powder has been treated with a silane coupling agent.
Claim 10
Dependent Claim
24 words
A method according to claim 6, wherein the hydrophobic silica fine powder has been treated with a silane coupling agent and a silicone oil.
Claim 11
Dependent Claim
28 words
A method according to claim 6, wherein the hydrophobic silica fine powder has been treated with a silicone oil having a viscosity of 50-1000 centistokes at 25° C.
Claim 12
Dependent Claim
44 words
A method according to claim 1, wherein the insulating magnetic toner has an electric resistance of at least 10 14 ohm.cm, a residual magnetization σ r of 1σ5 emu/g, a saturation magnetization σ s of 15-50 emu/g, and a coercive force of 20-100 Oe.
Claim 13
Dependent Claim
20 words
A method according to claim 1, wherein the insulating magnetic toner contains a crosslinked styrenic-type copolymer as a binder resin.
Claim 14
Dependent Claim
19 words
A method according to claim 1, wherein the insulating magnetic toner contains a crosslinked polyester as a binder resin.
Claim 15
Dependent Claim
32 words
A method according to claim 6, wherein the hydrophobic silica fine powder is used in an amount of 0.6-1.7 wt. parts with respect to 100 wt. parts of the insulating magnetic toner.
Claim 16
Dependent Claim
45 words
A method according to claim 6, wherein the hydrophobic silica fine powder has a BET specific surface area of 70-300 m 2 /g, a triboelectric chargeability of -100 to -300 μC/g, and a hydrophobicity of at least 90% or higher with respect to ion-exchanged water.
Claim 17
Dependent Claim
58 words
A method according to claim 1, wherein the magnetic toner is triboelectrically charged by the contact with the surface of the toner-carrying member, and the magnetic toner having the triboelectric charge develops the electrostatic image while being applied with an alternating bias having an AC component having a frequency of 200-40,000 Hz and a Vpp of 500-3,000 V.
Claim 18
Dependent Claim
21 words
A method according to claim 1, wherein said magnetic toner has a BET specific surface area of 1.9-3.0 m 2 /g.
Claim 19
Dependent Claim
34 words
A method according to claim 1, wherein the magnetic toner has a residual magnetization σ r of 2-4.5 emu/g, a saturation magnetization σ s of 20-40 emu/g, and a coercive force of 40-100 Oe.
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