US 9,778,586 B2 · Core material of magnetic carrier for electrophotographic developer and process for producing the same, magnetic carrier for electrophotographic developer, and two-component system developer

Abstract

The present invention provides a magnetic carrier for an electrophotographic developer which has an excellent durability and a stable charging property and is free from occurrence of spent toner thereonto, and a two-component system developer comprising the magnetic carrier for an electrophotographic developer and a toner. The present invention relates to a core material of a magnetic carrier for an electrophotographic developer comprising spherical composite particles comprising at least ferromagnetic iron oxide fine particles and a cured phenol resin and having an average particle diameter of 1 to 100 μm, a resin index of the spherical composite particles being within the range of 35 to 80%, and a magnetic carrier obtained by coating a surface of respective particles of the magnetic carrier core material with a resin.

Claims11

Dependent claims

A core material of a magnetic carrier for an electrophotographic developer comprising spherical composite particles comprising

ferromagnetic iron oxide fine particles in a content of 80 to 99% by weight based upon a weight of a magnetic carrier core material, wherein the ferromagnetic iron oxide fine particles have a single average particle diameter, the single average particle diameter being in a range of 0.05 to 2.0 μm, and
a cured phenol resin, wherein
the core material has an average particle diameter of 1 to 100 μm,
the core material has a resin index within the range of 38 to 80%,
the core material has a specific gravity of 2.5 to 4.0, and
the core material has a shape factor SF-2 of 100 to 120, the shape factor SF-2 being determined by Formula (1):
SF-2=(peripheral length of particles)2/(projected area of particles)×(¼π)×100 (1).

4 more elements

Dependencies are inferred from the claim text.

Facts

Application

14/111,587Filed 12 Apr 2012

Priority

JP 2011-08973814 Apr 2011

Published

US 2014/0065535 A16 Mar 2014

Granted

3 Oct 2017

Term ends

Not estimatedThe source records don’t support an estimate.

Classification9 codes

G03G 9/1075
Having magnetic components: structural characteristics of the carrier particles, e.g. shape or crystallographic structure
G03G 9/0804
Preparation methods: whereby the components are brought together in a liquid dispersing medium
G03G 9/108
Having magnetic components: ferrite carrier, e.g. magnetite
G03G 9/10884
Binder-type carrier: binder is obtained other than by reactions only involving carbon-carbon unsaturated bonds

Core material of magnetic carrier for electrophotographic developer and process for producing the same, magnetic carrier for electrophotographic developer, and two-component system developer

Life of this patent

Core material of magnetic carrier for electrophotographic developer and process for producing the same, magnetic carrier for electrophotographic developer, and two-component system developer

Life of this patent

Abstract

Claims11