Dowa Electronics Materials Co., Ltd.

Dowa IP Creation Co., Ltd.

Takeshi Kawauchi

Sho Ogawa

Tomohide Iida

Yukihiro Matsuda

Shou Ogawa

Yohei Ishikawa

Toshiya Kitamura

Ryusuke Nakao

Yuto Kamai

Haruka Seki

Masahiro Nakamura

Hiroyuki Miyano

According to the present invention, there is provided a carrier core material that is formed of ferrite particles in which 48 to 52 mass % of Fe, 16 to 22 mass % of Mn, 1.0 to 3.5 mass % of Mg and 0.05 to 0.5 mass % of Ca are included, and when an electrical resistance value with an applied voltage of 500 V in an environment (in an L/L environment) in which the temperature is 10&#xb0; C. and the relative humidity is 35% is R(&#x3a9;&#xb7;cm), and an electrical resistance value with an applied voltage of 500 V in an environment (in an H/H environment) in which the temperature is 30&#xb0; C. and the relative humidity is 70% is R(&#x3a9;&#xb7;cm), formula (1) below is satisfied.0.1&#x2264;(log&#x2212;log)&#x2264;0.3&#x2003;&#x2003;(1)

Carrier core material and electrophotographic development carrier using same and electrophotographic developer

A carrier core material includes, a main component, a material represented by a composition formula MnMFeO(where M is selected from Mg, Ti, Cu, Zn and Ni, 0&#x3c;X, 0&#x2264;Y, 0&#x3c;X+Y&#x3c;1), in which 0.1 to 1.0 mol % of at least one of Sr element and Ca element is contained as the total amount by conversion to SrO or CaO and in which the frequency of a grain whose length RSm is equal or more than 8.0 &#x3bc;m among grains appearing on the surface of particles of the carrier core material is equal to or less than 2.0 number percent. In this way, the degradation of a carrier caused by long-term use such as the separation of a coating resin is significantly reduced, stable charging performance is maintained and the cracking or chipping of the particles is reduced.

This invention is directed to a method for manufacturing carrier core particles for electrophotographic developer containing iron, manganese, and calcium as a core composition. The method includes (A) a mixing step of mixing an iron-containing raw material, a manganese-containing raw material, and a calcium-containing raw material to prepare a mixture thereof, (C) a granulation step of granulating the mixture after the mixing step, and (D) a firing step of firing a powdery material, which is obtained by granulating the mixture in the granulation step, at a predetermined temperature to form a magnetic phase. The calcium-containing raw material is provided in a granular form, and primary particles of the calcium-containing raw material have a volume mean diameter of 1 &#x3bc;m or less.

Carrier core particles for electrophotographic developer, carrier for electrophotographic developer, and electrophotographic developer

There are provided ferrite particles in which Mn ferrite is used as the main phase and which contain Sr ferrite, where the degree of projections and recesses in the surface of the particles falls within a range of 2.5 to 4.5 &#x3bc;m, and the standard deviation of the size of grains appearing on the surface of the particles falls within a range of 1.5 to 3.5 &#x3bc;m. In this way, a coating resin is left on the surface of the particles even after long-term use and thus a decrease in the charging property is reduced.

Ferrite particles and electrophotographic development carrier using same, electrophotographic developer and method of manufacturing ferrite particles

A method for manufacturing carrier core particles for electrophotographic developer that include manganese, magnesium, and iron as a core composition. The method includes a granulation step (A) of granulating a mixture of raw materials containing manganese, magnesium, and iron with a reducing agent added at a ratio of 0.10% to 1.00% by mass to a total mass of the raw materials containing manganese, magnesium, and iron, and a firing step of firing the granular material granulated in the granulation step. The firing step includes a first heating step (C) of applying heat at a constant temperature ranging from 500&#xb0; C. to 800&#xb0; C. in an atmosphere with an oxygen concentration of 1000 ppm to 15000 ppm for a predetermined period of time and a second heating step (D) of applying heat at a temperature higher than 800&#xb0; C. for a predetermined period of time after the first heating step.

Carrier for electrophotographic developer and electrophotographic developer

A carrier core particle for an electrophotographic developer includes a composition expressed by a general formula: MnFeO(0&#x3c;x&#x2266;1, 0&#x3c;y), a full width at half maximum z of the most intense peak () plane in a powder X-ray diffraction pattern satisfying 0.16 (degree)&#x2266;z, and a magnetization of 50 emu/g or higher in an external magnetic field of 1000 Oe.

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

Method for manufacturing carrier core particles for electrophotographic developer

Provided is a method for manufacturing carrier core particles for electrophotographic developer capable of stably maintaining high chargeability over a long time. The method for manufacturing carrier core particles includes a granulation step of granulating a mixture of raw materials containing manganese, iron, strontium, and calcium and a firing step of firing the mixture granulated in the granulation step. The firing step includes a heating process of heating the granular mixture with an increase in temperature to a predetermined degree and a cooling process of cooling the granular mixture, after the heating process, in an atmosphere with an oxygen concentration ranging from 5000 ppm to 20000 ppm. The molar ratio of the sum of strontium and calcium to the sum of the manganese, iron, strontium, and calcium is 0.0026 to 0.013.

Method for manufacturing carrier core particles for electrophotographic developer, carrier core particles for electrophotographic developer, carrier for electrophotographic developer, and electrophotographic developer

A method for manufacturing carrier core particles for electrophotographic developer including a slurrying step (A) of making an iron-containing raw material and a strontium-containing raw material into slurry, a granulation step (B) of granulating the slurry mixture obtained in the slurrying step, and a firing step (C) of firing a powdery material, which is obtained by granulating the slurry mixture in the granulation step, at a predetermined temperature to form a magnetic phase. The slurrying step makes the iron-containing raw material into the slurry containing the iron-containing raw material having a volume diameter Dof 1.0 to 4.0 &#x3bc;m and a volume diameter Dof 2.5 to 7.0 &#x3bc;m, and makes the strontium-containing raw material into the slurry so that the carrier core particles for electrophotographic developer contain 0&#x3c;y&#x2266;5000 ppm, where y denotes the content of the strontium in the carrier core particles.

There is provided a carrier core material for electrophotographic developer containing a soft ferrite, expressed by (MgMn)FeO(wherein X is in a range of 0.1&#x2266;X&#x3c;1.), wherein an analysis value of P on the surface of the carrier core material is 0.1 mass % or more, an analysis value of Mg is 2 mass % or more, a content of Mg on the surface of the carrier core material is 2 mass % or more by EDS, and when the content of Mg in the carrier core material is expressed by M1, and the analysis value of Mg on the surface of the carrier core material by EDS is expressed by M2, a value of M2/M1 exceeds 1.0.

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

A carrier core particle for an electrophotographic developer including a core composition expressed by a general formula: (MnMgCa) FeO(x+y+z+w=3, &#x2212;0.003&#x3c;v) as a main ingredient, wherein 0.05&#x2266;y&#x2266;0.35 and 0.005&#x2266;z&#x2266;0.024.

Carrier core particle for electrophotographic developer, carrier for electrophotographic developer and electrophotographic developer

A carrier core particle for an electrophotographic developer includes a core composition expressed by a general formula: MnFeO(0&#x3c;x&#x2266;1, 0&#x3c;y) as a main ingredient, 0.1 wt % or more of Si, and 0.03 wt % or more of at least one metal element selected from the group consisting of Ca, Sr and Mg.

The present invention provides a carrier core material for use in the production of an electrophotographic developer which, even when applied, for example, to MFPs (multifunction printers), can realize stable, high-quality and high-speed development, and has a prolonged replacing life of magnetic carriers, and a method of manufacturing the same, a magnetic carrier including the carrier core material, and an electrophotographic developer manufactured from the magnetic carrier. An electrophotographic development carrier is prepared by adding resin particles, a binder, a dispersant, a wetting agent, and water to a raw material powder, wet pulverizing the mixture, drying the pulverized product to give granulated powder, calcinatng the granulated powder, and then sintering the granulated powder to prepare a carrier core material having an internally hollow structure, and coating the carrier core material with a resin. An electrophotographic developer is manufactured by mixing the electrophotographic development carrier with a toner.

Electrophotographic developer carrier core material, electrophotographic developer carrier, methods of manufacturing the same, and electrophotographic developer

The carrier core particlesfor electrophotographic developer contain lithium as a core composition. When the carrier core particlesare immersed in pure water at a weight ratio of 1 part core particlesto 10 parts pure water and shaken, the amount of lithium that leaches out to the pure water is 0.10 ppm or lower.

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

Growing community of inventors

Okayama, Japan

Takeshi Kawauchi