Magnetic carrier and two component developer

• US 7,927,775 B2
• Filed: 01/21/2010
• Issued: 04/19/2011
• Est. Priority Date: 08/04/2008
• Status: Active Grant

• Current Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Original Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Inventors: Ishigami, Koh, Baba, Yoshinobu, Nakamura, Kunihiko, Inoue, Chika, Endo, Tomoko, Itakura, Takayuki, Fujikawa, Hiroyuki, Komatsu, Nozomu
• Primary Examiner(s): Chapman; Mark A
• Application Number:
  US12/691,057
• Publication Number:
  US 20100119968A1
• Time in Patent Office: 453 Days
• Field of Search: 430/111.3, 430/111.35, 430/111.4
• US Class Current: 430/111.3
• CPC Class Codes: G03G 9/0819 characterised by the dimensions of the particles
• CPC Class Codes: G03G 9/0821 characterised by physical parameters magnetic parameters G03G9/083
• CPC Class Codes: G03G 9/1075 Structural characteristics of the carrier particles, e.g. shape or crystallographic structure
• CPC Class Codes: G03G 9/1085 with non-ferrous metal oxide, e.g. MgO-Fe2O3
• CPC Class Codes: G03G 9/113 having coatings applied thereto
• CPC Class Codes: G03G 9/1132 Macromolecular components of coatings
• CPC Class Codes: G03G 9/1136 containing silicon atoms

Abstract

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° in a reflected electron image of the cross section of the magnetic carrier particle photographed by a scanning electron microscope.

Claims

1. A magnetic carrier having magnetic carrier particles produced by filling pores of porous magnetic core particles with a resin,

wherein the magnetic carrier contains 80% by number or more of the magnetic carrier particles satisfying the following (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°

in a reflected electron image of the cross section of the magnetic carrier particle photographed by a scanning electron microscope;

(a) the number of magnetic core regions having a length of 6.0 μ

m or longer on the straight lines is from 5.0% by number or more to 35.0% by number or less relative to the number of magnetic core regions having a length of 0.1 μ

m or longer on the straight lines, and

(b) the number of regions other than the magnetic core part having a length of 4.0 μ

m or longer on the straight lines is from 1.0% by number or more to 15.0% by number or less relative to the number of regions other than the magnetic core part having a length of 0.1 μ

m or longer on the straight lines.

2. The magnetic carrier according to claim 1, wherein the ratio of the area of the magnetic core region to the area of the cross section of the magnetic carrier particle is from 50% by area or more to 90% by area or less in the reflected electron image of the cross section of the magnetic carrier particle photographed by the scanning electron microscope.

3. The magnetic carrier according to claim 1, wherein the magnetic carrier particles are particles where a surface of the particles produced by filling pores of porous magnetic core particles with a resin is further coated with a resin.

4. A two component developer comprising at least a magnetic carrier and a toner, wherein the magnetic carrier is a magnetic carrier according to claim 1.

5. The two component developer according to claim 4, wherein in the toner, the content of the particle having a diameter of 4.0 μ

m or less on a number basis is 35.0% by number or less and the content of the particle having a diameter of 12.7 μ

m or more on a volume basis is 3.0% by volume or less.