Carrier core particle for electrophotographic developer, method for manufacturing the same, carrier for electrophotographic developer and electrophotographic developer

Abstract

A carrier core particle for an electrophotographic developer includes a composition expressed by a general formula: Mn x Fe 3−x O 4+y (0<x≦1, 0<y), a full width at half maximum z of the most intense peak (311) plane in a powder X-ray diffraction pattern satisfying 0.16 (degree)≦z, and a magnetization of 50 emu/g or higher in an external magnetic field of 1000 Oe.

1 . A carrier core particle for an electrophotographic developer, comprising:
 a composition expressed by a general formula: Mn x Fe 3−x O 4+y  (0<x≦1, 0<y);   a full width at half maximum z of the most intense peak (311) plane in a powder X-ray diffraction pattern satisfying 0.16 (degree)≦z; and   a magnetization of 50 emu/g or higher in an external magnetic field of 1000 Oe.   
     
     
         2 . The carrier core particle for the electrophotographic developer according to  claim 1 , wherein
 y≦−0.41x+0.41 is established (where 0<x≦1 and 0<y).   
     
     
         3 . A method for manufacturing a carrier core particle for an electrophotographic developer, the carrier core particle containing manganese, iron and oxygen as core composition, the method comprising the steps of:
 granulating a mixture of a raw material containing manganese and a raw material containing iron;   raising temperature of the powdery material granulated in the granulation step to a predetermined firing temperature;   performing reaction sintering on the powdery material, after the temperature-rising step, by maintaining the powdery material at a predetermined sintering temperature for a predetermined period of time; and   cooling the powdery material, after the reaction sintering step, under an atmosphere with an oxygen concentration from 0.3% to 3.0%.   
     
     
         4 . The method for manufacturing the carrier core particle for the electrophotographic developer according to  claim 3 , wherein
 the reaction sintering step is performed under the same atmosphere as in the cooling step.   
     
     
         5 . The method for manufacturing the carrier core particle for the electrophotographic developer according to  claim 3 , further comprising a step of:
 oxidizing the fired powdery material after the firing step.   
     
     
         6 . A carrier core particle for an electrophotographic developer, the carrier core particle containing manganese, iron and oxygen as core composition, wherein
 the carrier core particle is manufactured by granulating a mixture of a raw material containing manganese and a raw material containing iron, raising temperature of the granulated powdery material to a predetermined firing temperature, performing reaction sintering on the powdery material by maintaining the powdery material at a predetermined sintering temperature for a predetermined period of time, and cooling the powdery material under an atmosphere with an oxygen concentration from 0.3% to 3.0%.   
     
     
         7 . A carrier for an electrophotographic developer comprising:
 a carrier core particle including a composition expressed by a general formula: Mn x Fe 3−x O 4+y  (0<x≦1, 0<y), a full width at half maximum z of the most intense peak (311) plane in a powder X-ray diffraction pattern satisfying 0.16 (degree)≦z, and a magnetization of 50 emu/g or higher in an external magnetic field of 1000 Oe; and   a resin that coats the surface of the carrier core particle.   
     
     
         8 . An electrophotographic developer used to develop electrophotographic images, comprising:
 a carrier including a carrier core particle having a composition expressed by a general formula: Mn x Fe 3−x O 4+y  (0<x≦1, 0<y), a full width at half maximum z of the most intense peak (311) plane in a powder X-ray diffraction pattern satisfying 0.16 (degree)≦z, and a magnetization of 50 emu/g or higher in an external magnetic field of 1000 Oe, and a resin that coats the surface of the carrier core particle; and   a toner that can be triboelectrically charged by frictional contact with the carrier for development of electrophotographic images.