Claims
- 1. A magnetic brush developing method comprising: providing a developing means comprising a non-magnetic sleeve and a permanent magnet member stationary inside said non-magnetic sleeve at a position opposing an image-bearing member having an electrostatic latent image on the surface and forming a development gap therewith, thereby forming a developing region, said permanent magnet member having a developing magnetic pole in said developing region, and said developing magnetic pole providing a magnetic flux density of 700-1200 Gauss on the surface of said non-magnetic sleeve;
- selecting a developer comprising magnetic toner consisting of a binder resin and magnetic powder and capable of being charged at a particular polarity, and a magnetic carrier having a conductivity corresponding to an electric resistivity of 10.sup.5 -10.sup.10 .OMEGA.-cm and a particle size distribution within the range of 20-105 .mu.m, said magnetic toner containing 10-50 wt % of said magnetic powder, and said developer containing 10-90 wt % of said magnetic toner;
- causing the developer to be magnetically attracted onto a surface of said non-magnetic sleeve to form a magnetic brush; and
- rotating said non-magnetic sleeve to convey said magnetic brush to said developing region for bringing a tip portion of said magnetic brush into sliding contact with said image bearing member in said developing region, thereby developing said electrostatic latent image with said magnetic toner, wherein
- (a) said non-magnetic sleeve is rotated in the same direction as said image-bearing member in said developing region at a ratio of a surface moving velocity (V.sub.1) of said non-magnetic sleeve to a surface moving velocity (V.sub.2) of said image-bearing member (V.sub.1 /V.sub.2)=1.5-5.0,
- (b) the center of the developing magnetic pole of said permanent magnet member is deviated by 2.degree.-12.degree. toward the downstream side from a line connecting the closest points of said non-magnetic sleeve and said image-bearing member,
- (c) the development gap between said non-magnetic sleeve and said image-bearing member is set to be 0.2-0.6 mm, and
- (d) said image-bearing member has a negatively charged organic photosensitive surface layer having a surface potential of -400 to -700 V.
- 2. The magnetic brush developing method according to claim 1, wherein a bias voltage 0.6-0.9 times as large as said surface potential is applied to said non-magnetic sleeve when said electrostatic latent image is reverse-developed.
- 3. The magnetic brush developing method according to claim 1, wherein said magnetic carrier is a ferrite carrier, and the amounts of said magnetic carrier is 0.05-1 g/cm.sup.2 per a unit area of said non-magnetic sleeve.
- 4. The magnetic brush developing method as in claim 1, wherein the ratio V.sub.1 /V.sub.2 is set to be 3.0-4.0.
Priority Claims (2)
Number |
Date |
Country |
Kind |
2-48823 |
Feb 1990 |
JPX |
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2-251015 |
Sep 1990 |
JPX |
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Parent Case Info
This application is a continuation of application Ser. No. 08/079,453 filed Jun. 21, 1993, now abandoned, which is a continuation of application Ser. No. 07/662,190 filed Feb. 28, 1991, abandoned.
US Referenced Citations (5)
Number |
Name |
Date |
Kind |
4517274 |
Honda et al. |
May 1985 |
|
4640880 |
Kawanishi et al. |
Feb 1987 |
|
4841332 |
Haneda et al. |
Jun 1989 |
|
5049471 |
Higashiguchi et al. |
Sep 1991 |
|
5060023 |
Higashiguchi et al. |
Oct 1991 |
|
Continuations (2)
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Number |
Date |
Country |
Parent |
79453 |
Jun 1993 |
|
Parent |
662190 |
Feb 1991 |
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