Radiation imagery chemistry: process – composition – or product th – Electric or magnetic imagery – e.g. – xerography,... – Post imaging process – finishing – or perfecting composition...
Reexamination Certificate
2000-07-24
2001-10-23
Goodrow, John (Department: 1753)
Radiation imagery chemistry: process, composition, or product th
Electric or magnetic imagery, e.g., xerography,...
Post imaging process, finishing, or perfecting composition...
C430S137200
Reexamination Certificate
active
06306552
ABSTRACT:
This application is based on application(s) No. 213550/1999 filed in Japan, the contents of which are hereby incorporated by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a carrier and a two-component developer containing such a carrier.
2. Description of the Related Art
Conventionally, various carriers, which include a coat-type carrier made by coating magnetic particles with a resin, a binder-type carrier made by dispersing magnetic particles in a binder resin and a carrier using magnetic particles as they are, have been known. However, the application of any of these types of carriers causes the toner component to adhere to the carrier surface (to be spent), when used for a long time, resulting in a reduction in the chargeable points and the subsequent failure in maintaining the initial charge-applying capability of the carrier. The reduction in the initial charge-applying capability causes a failure in obtaining a predetermined quantity of charge, resulting in fog on a copied image.
Moreover, in the case when the coat-type carrier and the binder-type carrier having a resin on the surface thereof are used to copy an image having continuous areas with a comparatively high density and a comparatively low density for a long time, a problem (referred to as a lead-off phenomenon) arises, in which an image-less portion occurs in the border between the high-density area and the low-density area on the copied image.
Furthermore, the application of the carrier of the type using magnetic particles as they are causes a problem in which the carrier is developed together with the toner and spent at the time of continuous copying processes.
Here, in order to improve the binding properties of the coating material, with respect to the coat-type carrier, a carrier has been proposed in which a porous spherical carrier base material, made by sintering magnetic particles, is coated with a resin (Japanese Patent Laid-Open No. Hei. 8-160673). Such sintered spherical magnetic particles used as the carrier base material are obtained by highly filling the resin with magnetic particles, forming this into a spherical shape, and sintering the resulting particle. However, in the carrier of this type also, the problems of fog (due to separation of the coating material) and lead-off have still arisen during endurance copying processes.
SUMMARY OF THE INVENTION
The objective of the invention is to provide a carrier and a two-component developer which can prevent the occurrence of fog and lead-off for a long time, and reduce the carrier consumption.
The present invention relates to a carrier that has a BET specific surface area of 0.50 to 2.00 m
2
/g and a dynamic current value of 15 to 170 nA, and a two-component developer comprising a toner and such a carrier.
REFERENCES:
patent: 4126454 (1978-11-01), Jones
patent: 5688623 (1997-11-01), Nakamura et al.
patent: 5834152 (1998-11-01), Yasunaga et al.
patent: 6007956 (1999-12-01), Yasunaga et al.
patent: 6054243 (2000-04-01), Yamane et al.
patent: 6146801 (2000-11-01), Ichikawa et al.
patent: 8-160673 (1996-06-01), None
patent: 8-190225 (1996-07-01), None
Kobayashi Makoto
Maeda Osamu
Nishikawa Tomoharu
Takenaka Koichi
Yasunaga Hideaki
Burns Doane , Swecker, Mathis LLP
Goodrow John
Minolta Co. , Ltd.
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