US4614698A
Expired / Lapsed
US
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Two-component electrophotographic developer with magnetic carrier
Assignee: Kyocera Mita Industrial Co Ltd
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Filing: 1985-11-27
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Granted: 1986-09-30
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Expires: 2005-11-27
Abstract
Abstract A two-component electrophotographic developer for use in developing a latent electrostatic image of a low potential. The developer is composed of a mixture of a magnetic carrier of spherical sintered ferrite particles having raised and depressed portions attributed to the primary particles on their surface, a median size of from 30 to 50 micrometers, an apparent density of less than 2.6 g/cc and an electric resistance, measured in the form of a magnetic brush, of from 6×10 4 to 2.5×10 6 ohms and chargeable toner particles having a volume inherent resistivity of at least 1×10 13 ohms-cm and a specific inductive capacity of from 4 to 6. In a preferred embodiment, the chargeable toner particles have a median size of from 10 to 14 micrometers and are substantially free from particles having a particle diameter of not more than 5 micrometers. The developer can give an image of a high density, a high resolution and excellent gradation without brush marks.
Inventors
- 👤 Nobuhiro Miyakawa
- 👤 Koji Yano
- 👤 Kazuo Yamamoto
- 👤 Teruaki Higashiguchi
- 👤 Yoshinobu Kawakami
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-26 03:04
CPC Classifications
G; G03; G03G; G03G9/00; G03G9/08; G03G9/0819; G03G9/0821; G03G9/0823; G03G9/10; G03G9/107; G03G9/1075; G03G9/108; G03G9/1085
Claims Analysis
Total Claims: 16
Claim 1
Independent Claim
112 words
A two-component electrophotographic developer composed of a mixture of (a) a magnetic carrier of spherical sintered ferrite particles having raised and depressed portions attributed to the primary particles on their surface, a median size of from 30 to 50 micrometers, an apparent density of less than 2.6 g/cc and an electric resistance, measured in the form of a magnetic brush, of from 6×10 4 to 2.5×10 6 ohms, and (b) chargeable toner particles having a volume inherent resistivity of at least 1×10 13 ohms-cm and a specific inductive capacity of from 4 to 6 said toner particles being substantially free from particles having a particle diameter of not more than 5 micrometers.
Claim 2
Dependent Claim
112 words
A two-component electrophotographic developer composed of a mixture of (a) a magnetic carrier of spherical sintered ferrite particles having raised and depressed portions attributed to the primary particles on their surface, a median size of from 30 to 50 micrometers, an apparent density of less than 2.6 g/cc and an electric resistance, measured in the form of a magnetic brush, of from 6×10 4 to 2.5×10 6 ohms, and (b) chargeable toner particles having a volume inherent resistivity of at least 1×10 13 ohms-cm and a specific inductive capacity of from 4 to 6 said toner particles being substantially free from particles having a particle diameter of not more than 5 micrometers.
Claim 3
Dependent Claim
123 words
A two-component electrophotographic developer composed of a mixture of (a) a magnetic carrier of spherical sintered ferrite particles having raised and depressed portions attributed to the primary particles on their surface, a median size of from 30 to 50 micrometers, an apparent density of less than 2.6 g/cc and an electric resistance, measured in the form of a magnetic brush, of from 6×10 4 to 2.5×10 6 ohms, and (b) chargeable toner particles having a volume inherent resistivity of at least 1×10 13 ohms-cm and a specific inductive capacity of from 4 to 6, said toner particles having a median size of from 10 to 14 micrometers and being substantially free from particles having a particle diameter of not more than 5 micrometers.
Claim 4
Dependent Claim
123 words
A two-component electrophotographic developer composed of a mixture of (a) a magnetic carrier of spherical sintered ferrite particles having raised and depressed portions attributed to the primary particles on their surface, a median size of from 30 to 50 micrometers, an apparent density of less than 2.6 g/cc and an electric resistance, measured in the form of a magnetic brush, of from 6×10 4 to 2.5×10 6 ohms, and (b) chargeable toner particles having a volume inherent resistivity of at least 1×10 13 ohms-cm and a specific inductive capacity of from 4 to 6, said toner particles having a median size of from 10 to 14 micrometers and being substantially free from particles having a particle diameter of not more than 5 micrometers.
Claim 5
Dependent Claim
24 words
The developer of claim 1 wherein the weight ratio of the ferrite carrier (a) to the chargeable toner (b) is from 100:3.6 to 100:11.
Claim 6
Dependent Claim
63 words
The developer of claim 1 wherein the concentration, Ct%, of the toner particles (b) in the mixture is represented by the following equation ##EQU2## wherein Sc is the specific surface area (cm 2 /g) of the ferrite carrier (a), St is the specific surface area (cm 2 /g) of the toner particles (b), and k is a number of from 0.80 to 1.07.
Claim 7
Dependent Claim
30 words
The developer of claim 1 wherein the ferrite carrier (a) has an electric resistance, measured in the form of a magnetic brush, of from 1.0×10 5 to 7.2×10 5 ohms.
Claim 8
Dependent Claim
20 words
The developer of claim 1 wherein the ferrite carrier (a) has a median size of from 40 to 45 micrometers.
Claim 9
Dependent Claim
20 words
The developer of claim 1 wherein the ferrite carrier (a) has an apparent density of from 2.30 to 2.50 g/cc.
Claim 10
Dependent Claim
59 words
The developer of claim 1 wherein the ferrite particles (a) are particles of a Cu-Zn type or Cu-Zn-Mn type ferrite composed of 35 to 65 atomic % by weight of Fe, 5 to 15 atomic % by weight of Cu, 5 to 15 atomic % by weight of Zn and 0 to 0.5 atomic % by weight of Mn.
Claim 11
Dependent Claim
23 words
The developer of claim 8 wherein the ferrite particles are obtained by sintering said ferrite at a temperature of 900° to 1100° C.
Claim 12
Dependent Claim
21 words
The developer of claim 1 wherein the toner particles (b) have a volume inherent resistivity of at least 5×10 13 ohms-cm.
Claim 13
Dependent Claim
19 words
The developer of claim 1 wherein the toner particles (b) have a particle diameter of 5 to 20 micrometers.
Claim 14
Dependent Claim
28 words
The developer of claim 1 wherein the toner particles (b) contain 1 to 20% by weight of a high dielectric material in the form of a fine powder.
Claim 15
Dependent Claim
14 words
The developer of claim 12 wherein the high dielectric material is black titanium oxide.
Claim 16
Dependent Claim
35 words
The developer of claim 2 wherein the toner particles (b) are substantially free from particles having a median size of from 12 to 13 micrometers and a particle diameter of not more than 5 micrometers.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1989-09-29 | 1990-03-31 | 1990-09-30 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1993-09-29 | 1994-03-31 | 1994-09-30 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1997-09-29 | 1998-03-31 | 1998-09-30 | $7700.00 | Window Closed / Lapsed |