US4311779A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Developer for developing electrostatic latent images
Assignee: Kyocera Mita Industrial Co Ltd
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Filing: 1979-11-28
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Granted: 1982-01-19
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Expires: 1999-11-28
Abstract
Abstract Disclosed is a one-component type magnetic developer which comprises a binder medium and 45 to 65% by weight, based on the total developer, of fine particles of a magnetic material dispersed in the binder medium, the binder medium comprising a homopolymer of an aromatic vinyl monomer or a copolymer of (a) at least one aromatic vinyl monomer with (b) at least one mono- or di-ethylenically unsaturated monomer other than the aromatic vinyl monomer and having a weight average molecular weight of 75,000 to 150,000, wherein the electrostatic capacity as determined under conditions of an electrode spacing of 0.65 mm, an electrode sectional area of 1.43 cm 2 and an electrode load of 105 g/cm 2 is 7.8 to 11.7 PF (picofarad), the dielectric constant is 4 to 6 as determined under the above conditions and the electric resistance is at least 5×10 13 Ω-cm as determined under the above conditions.
Inventors
- 👤 Nobuhiro Miyakawa
- 👤 Takashi Teshima
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-29 15:42
CPC Classifications
G; G03; G03G; G03G9/00; G03G9/08; G03G9/087; G03G9/08702; G03G9/08706; G03G9/08708; G03G9/08711; G03G9/0821; G03G9/0823; G03G9/083; G03G9/08737; Y; Y10; Y10S; Y10S430/00; Y10S430/001; Y10S430/104; Y10S430/105
Claims Analysis
Total Claims: 12
Claim 1
Independent Claim
227 words
A carrierless magnetic developer which comprises a binder medium and 45 to 65% by weight, based on the total developer, of fine particles of a magnetic material dispersed in the binder medium, said binder medium consisting essentially of a copolymer of (a) at least one aromatic vinyl monomer with (b) at least one acrylic monomer or a terpolymer of (a) at least one aromatic vinyl monomer, (b) at least one acrylic monomer and (c) a conjugated diolefin and having a weight average molecular weight of 75,000 to 150,000, the amount of the aromatic vinyl monomer being 20 to 95% by weight based on the binder medium, wherein the electrostatic capacity as determined under conditions of an electrode spacing of 0.65 mm, an electrode sectional area of 1.43 cm 2 and an electrode load of 105 g/cm 2 is 7.8 to 11.7 PF (picofarad), the dielectric constant is 4 to 5 as determined under the above conditions and the electric resistance is at least 5×10 13 Ω-cm as determined under the above conditions; whereby the developer can develop a latent electrostatic image on a substrate without forcibly charging the developer particles by corona discharge and without frictionally charging the developer particles by causing strong sliding contact between the developer and the substrate resulting from rotating the developer in a direction opposite to the moving direction of the substrate.
Claim 2
Dependent Claim
227 words
A carrierless magnetic developer which comprises a binder medium and 45 to 65% by weight, based on the total developer, of fine particles of a magnetic material dispersed in the binder medium, said binder medium consisting essentially of a copolymer of (a) at least one aromatic vinyl monomer with (b) at least one acrylic monomer or a terpolymer of (a) at least one aromatic vinyl monomer, (b) at least one acrylic monomer and (c) a conjugated diolefin and having a weight average molecular weight of 75,000 to 150,000, the amount of the aromatic vinyl monomer being 20 to 95% by weight based on the binder medium, wherein the electrostatic capacity as determined under conditions of an electrode spacing of 0.65 mm, an electrode sectional area of 1.43 cm 2 and an electrode load of 105 g/cm 2 is 7.8 to 11.7 PF (picofarad), the dielectric constant is 4 to 5 as determined under the above conditions and the electric resistance is at least 5×10 13 Ω-cm as determined under the above conditions; whereby the developer can develop a latent electrostatic image on a substrate without forcibly charging the developer particles by corona discharge and without frictionally charging the developer particles by causing strong sliding contact between the developer and the substrate resulting from rotating the developer in a direction opposite to the moving direction of the substrate.
Claim 3
Dependent Claim
210 words
A magnetic developer which comprises a binder medium and fine particles of a magnetic material dispersed in the binder medium, said binder medium and said magnetic material being present in amounts of 35 to 55 parts by weight and 45 to 65 parts by weight, respectively, based on 100 parts by weight of the sum of the binder medium and the magnetic material, said binder medium being a copolymer of (a) at least one aromatic vinyl monomer with (b) at least one acrylic monomer or a terpolymer of (a) at least one aromatic vinyl monomer, (b) at least one acrylic monomer and (c) a conjugated diolefin and having a weight average molecular weight of 75,000 to 150,000, the amount of the aromatic vinyl monomer being 20 to 95% by weight based on the binder medium, wherein the electrostatic capacity of said developer as determined under conditions of an electrode spacing of 0.65 mm, an electrode sectional area of 1.43 cm 2 and an electrode load of 105 g/cm 2 is 8 to 11 PF (Picofarad), the dielectric constant of said developer is 4.1 to 5.1 as determined under the above conditions and the electric resistance of said developer is at least 5×10 13 Ω-cm as determined under the above conditions.
Claim 4
Dependent Claim
210 words
A magnetic developer which comprises a binder medium and fine particles of a magnetic material dispersed in the binder medium, said binder medium and said magnetic material being present in amounts of 35 to 55 parts by weight and 45 to 65 parts by weight, respectively, based on 100 parts by weight of the sum of the binder medium and the magnetic material, said binder medium being a copolymer of (a) at least one aromatic vinyl monomer with (b) at least one acrylic monomer or a terpolymer of (a) at least one aromatic vinyl monomer, (b) at least one acrylic monomer and (c) a conjugated diolefin and having a weight average molecular weight of 75,000 to 150,000, the amount of the aromatic vinyl monomer being 20 to 95% by weight based on the binder medium, wherein the electrostatic capacity of said developer as determined under conditions of an electrode spacing of 0.65 mm, an electrode sectional area of 1.43 cm 2 and an electrode load of 105 g/cm 2 is 8 to 11 PF (Picofarad), the dielectric constant of said developer is 4.1 to 5.1 as determined under the above conditions and the electric resistance of said developer is at least 5×10 13 Ω-cm as determined under the above conditions.
Claim 5
Dependent Claim
24 words
A magnetic developer as set forth in claim 1 or 2 wherein the weight average molecular weight of said polymer is 78,000 to 140,000.
Claim 6
Dependent Claim
38 words
A magnetic developer as set forth in claim 1 or 2 wherein the electrostatic capacity is 8 to 11 PF, the dielectric constant is 4.1 to 5.1 and the electric resistance is 1×10 14 to 1×10 16 Ω-cm.
Claim 7
Dependent Claim
35 words
A magnetic developer as set forth in claim 1 or 2 wherein the amount of the finely divided magnetic material is in the range of 50 to 60% by weight, based on the total developer.
Claim 8
Dependent Claim
53 words
A magnetic developer as set forth in claim 1 or 2 wherein the magnetic material has a particle size distribution such that particles having a size larger than 0.5μ occupy less than 20% of the total particles and particles having a size smaller than 0.3μ occupy less than 20% of the total particles.
Claim 9
Dependent Claim
30 words
A magnetic developer according to claim 1 or 2 wherein the amount of the aromatic vinyl monomer is from 45 to 93% by weight, based on the total binder medium.
Claim 10
Dependent Claim
49 words
A magnetic developer according to claim 1 or 2 wherein the fine particles of the magnetic material are coated with a fatty acid, a resin acid or a metal salt thereof or a surface-active agent in an amount of 0.1 to 30% by weight, based on the magnetic material.
Claim 11
Dependent Claim
24 words
A magnetic developer according to claim 1 or 2 wherein the size of the developer particles is in the range of 5 to 35μ.
Claim 12
Dependent Claim
39 words
A magnetic developer according to claim 1 or 2 wherein said binder medium is a copolymer of vinyl toluene and 2-ethylhexyl acrylate; a copolymer of styrene and 2-ethylhexyl acrylate; or a terpolymer of vinyl toluene, 2-ethylhexyl acrylate and butadiene.
References Cited (Backward Citations)
US3239465A
Cited
US3901695A
Cited
US3697268A
Cited
US3965022A
Cited
US4187330A
Cited
US4175962A
Cited
US4192902A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1985-01-18 | 1985-07-20 | 1986-01-19 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1989-01-18 | 1989-07-20 | 1990-01-19 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1993-01-18 | 1993-07-20 | 1994-01-19 | $7700.00 | Window Closed / Lapsed |