Canon Kabushiki Kaisha

Tomoko Endo

Yoshinobu Baba

Koh Ishigami

Hiroyuki Fujikawa

Takayuki Itakura

Kunihiko Nakamura

Nozomu Komatsu

Chika Inoue

Naoki Okamoto

Provided is a two-component developer containing: a magnetic carrier obtained by coating a magnetic core with a resin; and toner, in which: the magnetic core contains at least a ferrite component and at least one kind of an oxide selected from the group consisting of SiOand AlO; the content of the oxide is 4.0 mass % or more and 40.0 mass % or less with respect to the magnetic core; the magnetic core has a specific resistance of 5.0&#xd7;10&#x3a9;&#xb7;cm or more and 5.0&#xd7;10&#x3a9;&#xb7;cm or less at the time of the application of 1,000 V/cm; the magnetic carrier has an intensity of magnetization in 79.6 kA/m of 40.0 Am/kg or more and 65.0 Am/kg or less, and a residual magnetization after the application of an external magnetic field of 79.6 kA/m of 3.0 Am/kg or less; and the toner has a weight-average particle diameter (D4) of 3.0 &#x3bc;m or more and 10.0 &#x3bc;m or less and an average circularity of 0.940 or more and 0.990 or less.

Two-component developer

The present invention provides an image of high image quality by using a magnetic carrier coated with a novel coating resin composition. Further, the present invention stably provides a good image which is hardly influenced by environmental fluctuation and long-term use and has a superior stability of a charging amount when left to stand especially under high temperature and high humidity environments. The present invention also provides a magnetic carrier characterized in that a carrier core surface is coated with a copolymer containing at least, as copolymerization components, an acrylic monomer having a specific structure and an acrylic macromonomer having a specific structure.

Magnetic carrier and two-components developer

In a method for coating electrophotographic carrier core surfaces with a resin composition by rotating a rotator having a plurality of agitating blades on its surface in a casing; a coating treatment material that is introduced to a space defined between the rotator and the casing is in a packing of from 50% to 98% by volume; at the time of coating treatment, the electrophotographic carrier core surfaces are coat-treated with the resin composition while being put forward and put backward; and the electrophotographic carrier cores and the resin composition are, at the time of coating treatment, temperature-controlled at a specific temperature T (&#xb0; C.) or below. This method enables the electrophotographic carrier core surfaces to be more uniformly coated with a coating resin.

Method for producing electrophotographic carrier and electrophotographic carrier produced by using the method

A magnetic carrier is provided which uses a toner having high coloring power and enables development to be performed at low electric field intensity and can form high quality images while keeping gradation characteristics. The magnetic carrier includes magnetic carrier particles including at least porous magnetic core particles and a resin. The electric field intensity just before the break-down of the magnetic carrier is 1,300 V/cm or more and 5,000 V/cm or less.

Magnetic carrier, two-component developer and image forming method

A magnetic carrier and a two-component developer are provided which have remedied blank areas, fog after leaving, carrier sticking during running, and image density variations before and after running. The magnetic carrier has magnetic carrier particles having at least porous magnetic core particles and a resin. The magnetic carrier particles satisfying the specific conditions (a), (b) and (c) where, in a reflected electron image of cross sections of the magnetic carrier particles as photographed with a scanning electron microscope, straight lines that divide a cross section of a magnetic carrier particle into 72 at intervals of 5&#xb0; are drawn from a reference point of the cross section thereof toward the surface of the magnetic carrier particle; the magnetic carrier particles being contained in an amount of 60% by number or more.

Magnetic carrier and two-component developer

Provided is a magnetic carrier giving a high quality image free of density variation without the occurrence of fogging or carrier adhesion and having excellent dot reproducibility even during long-term use. The magnetic carrier has magnetic carrier particles produced by filling pores of porous magnetic core particles with a resin. The magnetic carrier contains 80% by number or more of the magnetic carrier particles satisfying the specific conditions (a) and (b) when 18 straight lines passing through a reference point of a cross section of the magnetic carrier particle are drawn at intervals of 10&#xb0; in a reflected electron image of the cross section of the magnetic carrier particle photographed by a scanning electron microscope.

Magnetic carrier and two component developer

A magnetic carrier which has magnetic carrier particles each having at least porous magnetic core particles and a resin, in which, in a backscattered electron image of the magnetic carrier particles, photographed with a scanning electron microscope as taken at an accelerating voltage of 2.0 kV, magnetic carrier particles having area proportion Sfound from a specific expression (1) of from 0.5 area % or more to 8.0 area % or less are in a proportion of 8.0% by number or more in the magnetic carrier, an average proportion Avof the total area of portions having a high luminance which come from a metal oxide on the magnetic carrier particles to the total projected area of the magnetic carrier particles is from 0.5 area % or more to 8.0 area % or less, and an average proportion Avfound from a specific expression (2) is 10.0 area % or less.

Growing community of inventors

Odawara, Japan

Tomoko Endo