Powdertech Co., Ltd.

Toru Iwata

Koji Aga

Tomoyuki Suwa

Takashi Kojima

Hiromichi Kobayashi

Toshio Honjo

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

Employment of a carrier core material for an electrophotographic developer containing 0.8 to 5% by weight of Mg, 0.1 to 1.5% by weight of Ti, 60 to 70% by weight of Fe and 0.2 to 2.5% by weight of Sr and having an amount of Sr dissolved with a pH4 standard solution of 80 to 1000 ppm, a carrier using the core material and a process for producing them, and an electrophotographic developer using the carrier.

Carrier core material and carrier for electrophotographic developer and process for producing the same, and electrophotographic developer using the carrier

A porous ferrite core material for an electrophotographic developer, the porous ferrite core material including Mg in a content of 0.3 to 3% by weight, Ti in a content of 0.4 to 3% by weight and Fe in a content of 60 to 70% by weight, and the porous ferrite core material having a pore volume of 0.04 to 0.16 ml/g, a peak pore size of 0.4 to 1.6 &#x3bc;m, a saturation magnetization of 40 to 80 Am/kg, a remanent magnetization of less than 7 Am/kg and a coercive force of less than 43 A/m; a resin-filled ferrite carrier for an electrophotographic developer obtained by filling a resin in the voids of the porous ferrite core material; and an electrophotographic developer using the ferrite carrier.

Porous ferrite core material for electrophotographic developer, resin-filled ferrite carrier and electrophotographic developer using the ferrite 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

There are provided a ferrite carrier core material for an electrophotographic developer, which contain 10 to 30% by weight of Mn, 1.0 to 3.0% by weight of Mg, 0.3 to 1.5% by weight of Ti and 40 to 60% by weight of Fe, a ferrite carrier for an electrophotographic developer obtained by coating the ferrite core material, and an electrophotographic developer using the ferrite carrier.

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

It is contemplated to provide irregular shaped ferrite carrier which has a lower resistance, a high specific surface area, a low specific gravity and a longer operational life, and an electrophotographic developer comprising the ferrite carrier which prevents the toner scattering, has a high image density, and is responsive to high-speed and color imaging. The irregular shaped ferrite carrier is characterized in that the carrier particles are irregular shaped, and 40 percent by number or more of the particles have a rock candy sugar shape and/or an oyster shell shape, and that the shape factor (SF-1=R/S&#xd7;&#x3c0;/4&#xd7;100, wherein R is a maximum length and S is a projected area.) is 140 to 250, and the distribution width (&#x3b4;) is 60 or less.

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Kashiwa, Japan

Toru Iwata