Powdertech Co., Ltd.

Mitsui Minings & Melting Co., Ltd.

Tomoyuki Suwa

Koji Aga

Tsuyoshi Itagoshi

Hiromichi Kobayashi

Toshio Honjo

Yasunori Tabira

Toru Iwata

It is an object of the present invention to provide a ferrite carrier core material and a ferrite carrier for an electrophotographic developer, which have an excellent charging property, hardly cause carrier scattering due to cracking and chipping of the core material, and have a prolonged life, and methods for manufacturing these, and an electrophotographic developer using the ferrite carrier. For this object, the ferrite carrier core material and a ferrite carrier for an electrophotographic developer, wherein (1) the ferrite composition contains 0.5 to 2.5% by weight of Sr, and the presence amount of Sr&#x2014;Fe oxides satisfies a specific conditional expression, (2) the distribution in the number of the shape factor SF-2 is in a specific range, (3) the BET specific surface area is 0.15 to 0.30 m/g, (4) the average particle diameter Dis 20 to 35 &#x3bc;m, and (5) the magnetization is 50 to 65 Am/kg.

Ferrite carrier core material and ferrite carrier for electrophotographic developer, methods for manufacturing these, and electrographic developer using the ferrite carrier

A ferrite core material for a resin-filled type carrier, and a resin-filled type carrier which is used as an electrophotographic developer by mixing a toner, sufficiently secure the image density, have no carrier adhesion and can maintain high-quality images over a long period, and an electrophotographic developer using the carrier, are provided. A ferrite core material for a resin-filled type carrier characterized in a void fraction of 10 to 60%, a resin-filled type carrier filled in the carrier core material with a resin, and an electrophotographic developer composed of the resin-filled type carrier and a toner, are provided.

Ferrite core material for resin-filled type carrier, resin-filled type carrier, and electrophotographic developer using the carrier

There is provided a ferrite core material for an electrophotographic developer, the ferrite core material having a ferrite particle composition represented by the formula (1) shown below, containing SrO replacing a part of (MnO) and/or (MgO) in the formula (1) shown below, and having a Cl concentration of 0.1 to 100 ppm, as measured by an elution method of the ferrite core material:(MnO)(MgO)(FeO)&#x2003;&#x2003;(1)wherein x=35 to 45 mol %, y=5 to 15 mol %, z=40 to 60 mol %, and x+y+z=100 mol %.

Ferrite core material and ferrite carrier for electrophotographic developer, and electrophotographic developer using the ferrite carrier

A carrier core material for an electrophotographic developer including Li ferrite, maghemite, and FeO, wherein a part thereof is substituted with Mn, Li content is 1 to 2.5% by weight, Mn content is 2 to 7.5% by weight, and silicon content is 25 to 10,000 ppm, the following equation (1) is satisfied when respective integrated strengths of spinel crystal structure (110), (210), (211), and (311) faces in X-ray diffraction are respectively I, I, I, and I, a resistivity Rof 50 V across a 6.5 mm gap is 5&#xd7;10to 7&#xd7;10&#x3a9;, and a resistivity Rof 1,000 V across a 6.5 mm gap is 1&#xd7;10to 8&#xd7;10&#x3a9;.2&#x3c;100&#xd7;()/&#x3c;14&#x2003;&#x2003;(1).

Carrier core material for electrophotographic developer, carrier, and electrophotographic developer using the carrier

A ferrite carrier for an electrophotographic developer having a compression breaking strength of 150 MPa or more, a rate of compressive change of 15.0% or more and a shape factor SF-1 of 100 to 125, a method for producing the same, and an electrophotographic developer containing the ferrite carrier.

Ferrite carrier for electrophotographic developer, method for producing the same, and electrophotographic developer

A carrier core material for an electrophotographic developer containing Li ferrite, maghemite, and FeO, wherein a part thereof is substituted with Mn, a Li content is 1 to 2.5% by weight, a Mn content is 2 to 7.5% by weight, and a silicon content is 25 to 10,000 ppm, a compression breaking strength is 130 MPa or more, an SF-1 is 125 to 145, respective cumulative strengths of respective spinel crystal structure faces in X-ray diffraction satisfy a certain equation, a vacuum resistivity Racross a 2 mm gap when a measurement voltage of 500 V is applied is 1&#xd7;10to 5&#xd7;10&#x3a9;, and a vacuum resistivity Racross a 6.5 mm gap when a measurement voltage of 1,000 V is applied is 5&#xd7;10to 1&#xd7;10&#x3a9;.

Carrier core material for an electrophotographic developer, carrier, and electrophotographic developer using the carrier

A carrier for an electrophotographic developer which is used as an electrophotographic developer in a mixture with a toner and which secures sufficiently the image density and can maintain high-quality images for a long period, and an electrophotographic developer using the carrier, are provided. A resin-filled ferrite carrier for electrophotographic developer obtained by filling, with a resin, avoid of a porous ferrite core whose void continues from the surface to reach the interior of the core, the carrier comprising a plurality of three-dimensional laminate structures in which resin layers and ferrite layers are alternately present, and an electrophotographic developer including the carrier and a toner, are employed.

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Kashiwa, Japan

Tomoyuki Suwa