JP2005099489A - Carrier for electrophotographic development and method for manufacturing the same, and electrophotographic developer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a carrier for electrophotographic development which coats the surface of magnetic powder being a core with a fluorine-contained resin and prevents the resin from being peeled off from the core surface to improve durability and electrostatic charge holding property. <P>SOLUTION: The carrier for electrophotographic development is prepared by coating the surface of the magnetic powder composed of ferrite and/or magnetite as principal components with the coating resin prepared by mixing at least one resin selected from a resin containing fluorine in the molecule, a polyimide resin, a polyamide resin, an epoxy resin, etc. The amount of coating of the coating resin is preferably 0.1 to 5wt%. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an electrophotographic developing carrier whose surface is coated with a resin and a method for producing the same.

  2. Description of the Related Art Two-component developers composed of toner and carrier are widely used as developers for electrostatic images such as electrophotography. Carriers (electrophotographic development carriers) used in the developer for the two-component electrophotographic copying machine are required to have characteristics such as wear resistance and chargeability. There is a resin-coated carrier (hereinafter referred to as a carrier) in which iron particles or the like are used as a magnetic material core (hereinafter referred to as a core) and a resin is coated on the core. As an excellent coating resin that imparts wear resistance and chargeability to this carrier, there is a resin containing fluorine in the molecule (hereinafter referred to as a fluorine-containing resin) (for example, see Patent Documents 1 to 4). ).

  Fluorine-containing resin has the advantage that it is easy to obtain negative chargeability due to the high electronegativity of the fluorine component, and has good charge retention, and because the resin has low surface energy, when used as a carrier coating resin, This is also advantageous for durability such as toner adhesion.

  However, with the advancement of electronic copying machines and the advancement of image quality required for electrophotography, the mechanical durability required for carriers has become stricter, and the required physical properties such as saturation magnetic properties have also diversified.

  As a result of the strict mechanical durability required, there has been a problem in the carrier according to the prior art that the resin peels off from the core surface and the initial characteristics cannot be maintained. This is presumably because the coat peels off from the core surface because the binding force between the fluorine-containing resin and the magnetic material core, which is an inorganic substance, is weak.

  To solve this problem, porous amorphous iron powder is used as the core, and the surface concave portion of the porous amorphous iron powder is filled with a fluorine-containing resin together with a binder such as polyamide-imide resin or epoxy resin. A carrier in which a silicon resin is coated thereon has been proposed (see, for example, Patent Document 5).

JP 47-17434 A JP 47-17435 A JP-A-48-90238 JP 51-117638 A JP-A-7-64344

  According to Patent Document 5, a porous amorphous iron powder is used as a core, and a fluorine-containing resin together with a binder such as a polyamide-imide resin or an epoxy resin is formed on the surface recess of the porous amorphous iron powder. It is described that the carrier filled and coated with the silicon resin has mechanical durability. However, since the carrier according to Patent Document 5 uses iron powder as a core, the saturation magnetic force as a magnetic property is as high as 200 [emu / g]. Therefore, when applied to a developing machine for electrophotography, There are problems such as an increase in required rotational torque, high density as powder, and poor developer transportability.

Here, in order to lower the saturation magnetic force of the carrier and further improve the developer transportability, it is conceivable to use ferrite or magnetite as the core.
For example, ferrite is made of oxides of copper, zinc, nickel, cobalt, manganese, magnesium, etc. and their mixtures, and the magnetic properties and mechanical properties can be adjusted by controlling the composition and manufacturing conditions, and is chemically stable. It has the excellent property of being. Therefore, if a carrier is manufactured using ferrite as a core, a carrier having a low saturation magnetic force can be manufactured as compared with a case where iron powder is used as a core. Therefore, when the carrier is applied to an electrophotographic developing machine or the like, It is possible to expect effects such as soft rise, small required rotational torque of the developing machine, good carrier transportability in the developing machine, and clear electrophotographic image obtained.
Similarly, even if a carrier is manufactured using magnetite as a core, a carrier having a low saturation magnetic force can be manufactured as compared with the case where iron powder is used as a core. Therefore, when the carrier is applied to an electrophotographic developing machine, etc. Effects such as soft brushing, small required rotational torque of the developing machine, good carrier transportability in the developing machine, and clear electrophotographic images obtained can be expected.
However, ferrite and magnetite, unlike iron powder, have a high sphericity, and a porous amorphous shape cannot be obtained. Therefore, the method described in Patent Document 5 cannot be adopted.

  Furthermore, since the surface of the carrier described in Patent Document 5 is coated with a silicon resin and the fluorine-containing resin is present inside the carrier, it is difficult to fully utilize the advantages of the fluorine-containing resin. In addition, with the use of the carrier, there has been a problem that the electrostatic characteristics of the carrier greatly fluctuate when the silicon resin wears and the internal fluorine-containing resin is exposed.

  In consideration of the above circumstances, the present invention is a carrier for electrophotographic development. The core uses ferrite or magnetite and is coated with a resin containing fluorine from the carrier surface to the core surface. The purpose is to provide a highly functional carrier.

Researchers of the present invention have made numerous trials and errors, and as a result of intensive studies, the resin containing fluorine in the molecule is selected from fluorinated ethylene propylene resin, perfluoroalkoxy resin, trichlorofluoroethylene resin, etc. At least one resin, and
As a resin having an amide bond in the molecule and / or a resin having two or more oxirane rings in one molecule, at least one resin selected from polyimide resin, polyamideimide resin, epoxy resin and the like; ,
By coating the entire surface of the core mainly composed of ferrite and / or magnetite with the coating resin prepared by mixing the carrier, a carrier having sufficient mechanical durability and desirable electrostatic and magnetic properties can be obtained. We found that it can be manufactured.

That is, the first configuration according to the present invention includes a resin containing fluorine in a molecule, a resin having an amide bond in the molecule and / or a resin having two or more oxirane rings in one molecule. The mixed coating resin
A carrier for electrophotographic development, wherein the entire surface of a magnetic powder mainly composed of ferrite and / or magnetite is coated.

  In the second configuration, the resin containing fluorine in the molecule includes at least one resin selected from a fluorinated ethylene propylene resin, a perfluoroalkoxy resin, and a trichlorofluoroethylene resin. The electrophotographic developer carrier according to the first configuration, which is characterized.

  In the third configuration, the resin having an amide bond in the molecule and / or the resin having two or more oxirane rings in one molecule is selected from a polyimide resin, a polyamideimide resin, and an epoxy resin, The carrier for electrophotographic development according to the first or second configuration, wherein the carrier contains one or more resins.

  A fourth configuration is the electrophotographic developer carrier according to any one of the first to third configurations, wherein the coating amount of the coating resin is 0.1 to 5% by weight.

  A fifth configuration is the electrophotographic developer carrier according to any one of the first to third configurations, wherein a coating amount of the coating resin is 0.5 to 3% by weight.

  A sixth configuration is the electrophotographic method according to any one of the first to fifth configurations, wherein the coating resin contains 10 to 90% by weight of a fluorine-containing resin in the molecule. It is a carrier for development.

  A seventh configuration is the electrophotographic developer carrier according to any one of the first to sixth configurations, wherein the magnetic powder has a center particle size of 20 to 120 μm.

The eighth configuration is a mixing step of mixing a resin containing fluorine in the molecule with a resin having an amide bond in the molecule and / or a resin having two or more oxirane rings in one molecule;
A coating step of coating the coating resin produced in the mixing step on the entire surface of the magnetic powder mainly composed of ferrite and / or magnetite;
It is a manufacturing method of the carrier for electrophotographic development characterized by having.

  A ninth configuration is an electrophotographic developer comprising the carrier for electrophotographic development according to any one of the first to seventh configurations.

  In the first configuration, a coating resin in which a resin containing fluorine in a molecule and a resin having an amide bond in the molecule and / or a resin having two or more oxirane rings in one molecule is mixed with ferrite A carrier having sufficient mechanical durability and desirable magnetic and electrostatic properties as a carrier for electrophotographic development by being coated on the entire surface of magnetic powder containing magnetite as a main component.

  The second configuration preferably includes at least one resin selected from a fluoroethylenepropylene resin, a perfluoroalkoxy resin, and a trichlorofluoroethylene resin as the resin containing fluorine in the molecule. By using such a carrier, it is a carrier having sufficient mechanical durability and desirable magnetic and electrostatic properties as a carrier for electrophotographic development.

  The third configuration is preferably selected from a polyimide resin, a polyamideimide resin, and an epoxy resin as the resin having an amide bond in the molecule and / or the resin having two or more oxirane rings in one molecule. As a carrier for electrophotographic development containing at least one resin, the carrier has sufficient mechanical durability and desirable magnetic and electrostatic properties.

  The fourth configuration is a carrier having sufficient mechanical durability and desirable magnetic and electrostatic properties, in which the coating amount of the coating resin is preferably 0.1 to 5% by weight.

  The fifth configuration is a carrier having sufficient mechanical durability and desirable magnetic and electrostatic properties, in which the coating amount of the coating resin is more preferably 0.5 to 3% by weight.

  A sixth structure is a carrier having sufficient mechanical durability and desirable magnetic and electrostatic properties in which the coating resin preferably contains 10 to 90% by weight of a fluorine-containing resin in the molecule. It is.

  The seventh configuration is a carrier having a center particle diameter of 20 to 120 μm and sufficient mechanical durability and desirable magnetic and electrostatic properties.

  According to the eighth configuration, a coating resin obtained by mixing a resin containing fluorine in a molecule and a resin having an amide bond in the molecule and / or a resin having two or more oxirane rings in one molecule As a carrier for electrophotographic development, a carrier having sufficient mechanical durability and desirable magnetic and electrostatic properties is manufactured by coating the entire surface of magnetic powder mainly composed of ferrite and / or magnetite. can do.

  The ninth configuration is an electrophotographic developer having desirable mechanical, magnetic, and electrostatic properties.

The core used in the carrier for electrophotographic development of the present invention has a ferrite having a saturation magnetic force of about 30 to 85 [emu / g] and / or a saturation magnetic force of about 80 to 95 [emu / g]. It is a magnetic powder whose main component is magnetite. By using the above-mentioned magnetic powder as the core of the carrier, a carrier having a saturation magnetic force of about 30 to 95 [emu / g] can be produced.
The center particle size of the magnetic powder used as the core is preferably in the range of 20 to 120 μm in consideration of the required carrier size.

  Preferable examples of the fluorine-containing resin used for the electrophotographic development carrier of the present invention include fluorinated ethylene propylene resin, perfluoroalkoxy resin, trichlorofluoroethylene resin and the like.

  In order to obtain the coating resin used in the carrier for electrophotographic development of the present invention, the resin mixed with the fluorine-containing resin is a resin having an amide bond in the molecule and / or two or more oxiranes in one molecule. A resin having a ring is used. Preferred examples of the resin having an amide bond in the molecule include a polyimide resin and a polyamideimide resin, and examples of the resin having two or more oxirane rings in a molecule include an epoxy resin.

  Among the above-mentioned resins containing at least one resin selected from fluorine-containing resins, resins having an amide bond in the molecule, and / or resins having two or more oxirane rings in one molecule A coating resin is prepared by a mixing step in which at least one resin containing at least one resin is mixed. At this time, it is preferable that 10 to 90 weight% of fluorine-containing resin is contained with respect to the total amount of the coating resin. When the fluorine-containing resin with respect to the total amount of the coating resin is within the above range, the prepared carrier for electrophotographic development satisfies sufficient mechanical durability while exhibiting preferable electrostatic characteristics of the fluorine-containing resin. be able to.

Then, in the coating step of heating while mixing and stirring the coating resin, the magnetic powder, and an appropriate solvent, the solvent is volatilized to obtain coated particles in which the entire surface of the magnetic powder is coated with the coating resin and is in a dry state. Thereafter, the coated particles were heated above the curing temperature of the coating resin to cure the coating resin to obtain a carrier. At this time, the coating amount of the coating resin to the coated particles is 0.1 to 5% by weight, more preferably 0.5 to 3% by weight. When the coating amount of the coating resin with respect to the coated particles is within the above range, in the prepared carrier, the preferable magnetic characteristics of the magnetic powder, the preferable electrostatic characteristics of the fluorine-containing resin, and sufficient mechanical durability are obtained. It can be demonstrated.
An example of a preferable solvent is methyl ethyl ketone.

So far, in the description of the carrier manufacturing process, the mixing process and the covering process have been described separately. However, from the viewpoint of process and productivity, the two processes can be performed simultaneously. Furthermore, an electrophotographic developer having desirable mechanical, magnetic, and electrostatic properties could be obtained by blending an appropriate toner with the carrier according to the present invention obtained in the above-described process.
Hereinafter, based on an Example, this invention is demonstrated concretely.

(Example 1)
100 parts by weight of ferrite with a center particle size of 50 μm as a core, 3 parts by weight of a coating resin that is a mixture of epoxy resin and fluorinated ethylene propylene resin in a weight ratio of 60:40, and 100 parts by weight of methyl ethyl ketone as a solvent are used in a universal stirrer The mixture was stirred at 120 ° C. to remove the solvent, and further stirred while heating to 240 ° C. to obtain coated particles. The coated particles were further heated at 270 ° C. for 3 hours in a hot air circulating oven dryer to cure the resin, thereby obtaining a target carrier for electrophotographic development.

The static resistance of this electrophotographic development carrier is 3.7 × 10 ¹² Ω · cm when 500 V is applied, and the carbon content of the resin covering the carrier is measured by combustion / infrared absorption analysis. As a result, it was 1.32 wt%. Further, a positive charge toner was added to the carrier so that the weight ratio was 5%, and a charge amount measurement sample was prepared. As a result of measuring the toner charge amount of this sample with a blow-off charge amount measurement device, +15.4 μC / g Met.

Further, as a forced deterioration test, 20 g of the carrier was placed in a 100 ml polyethylene container and forcedly stirred for 5 hours with a paint shaker. When the static resistance of the carrier after this forced deterioration test was measured, it was 2.7 × 10 ¹¹ Ω · cm when 500 V was applied, and the carbon content of the resin covering the core was 1.21 wt%. . Further, a positive charge toner was added to the carrier after this forced deterioration test so that the weight ratio was 5% to prepare a charge amount measurement sample, and the toner charge amount of this sample was measured with a blow-off charge amount measurement device. It was +14.7 μC / g. As a result, it has been found that the carrier has sufficient durability for the forced deterioration test.

(Example 2)
A universal stirrer comprising 100 parts by weight of ferrite having a center particle diameter of 50 μm as a core, 3 parts by weight of a coating resin which is a mixture of polyamideimide resin and fluorinated ethylene propylene resin in a weight ratio of 50:50, and 100 parts by weight of methyl ethyl ketone as a solvent The mixture was stirred at 120 ° C. to remove the solvent, and further stirred while heating to 240 ° C. to obtain coated particles. The coated particles were further heated at 300 ° C. for 3 hours in a hot air circulating oven dryer to cure the resin, thereby obtaining a target carrier for electrophotographic development.

The static resistance of this electrophotographic development carrier is 4.5 × 10 ¹² Ω · cm when 500 V is applied, and the carbon content of the resin coating the carrier is measured by combustion / infrared absorption analysis. As a result, it was 1.36 wt%. Further, a positively charged toner was added to the carrier so as to have a weight ratio of 5% to prepare a charge amount measurement sample. As a result of measuring the toner charge amount of this sample with a blow-off charge amount measurement device, +17.3 μC / g Met.

Further, as a forced deterioration test, 20 g of the carrier was placed in a 100 ml polyethylene container and forcedly stirred for 5 hours with a paint shaker. When the static resistance of the carrier after this forced deterioration test was measured, it was 6.7 × 10 ¹¹ Ω · cm when 500 V was applied, and the carbon content of the resin covering the core was 1.28 wt%. . Further, a positive charge toner was added to the carrier after this forced deterioration test so that the weight ratio was 5% to prepare a charge amount measurement sample, and the toner charge amount of this sample was measured with a blow-off charge amount measurement device. It was +15.7 μC / g. As a result, it has been found that the carrier has sufficient durability for the forced deterioration test.

(Comparative Example 1)
100 parts by weight of ferrite with a center particle size of 50 μm as a core, 3 parts by weight of a coating resin that is a mixture of silicon resin and fluorinated ethylene propylene resin in a weight ratio of 50:50, and 100 parts by weight of methyl ethyl ketone as a solvent The mixture was stirred at 120 ° C. to remove the solvent, and further stirred while heating to 240 ° C. to obtain coated particles. The coated particles were further heated at 270 ° C. for 3 hours in a hot air circulating oven dryer to cure the resin, thereby obtaining a target carrier for electrophotographic development.

The static resistance value of the carrier for electrophotographic development is 9.7 × 10 ¹¹ Ω · cm when 500 V is applied, and the carbon content of the resin covering the carrier is measured by combustion / infrared absorption analysis. As a result, it was 1.07 wt%. Further, a positive charge toner was added to this carrier so that the weight ratio was 5%, and a charge amount measurement sample was prepared. As a result of measuring the toner charge amount of this sample with a blow-off charge amount measurement device, +12.7 μC / g Met.

Further, as a forced deterioration test, 20 g of the carrier was placed in a 100 ml polyethylene container and forcedly stirred for 5 hours with a paint shaker. When the static resistance of the carrier after this forced deterioration test was measured, it was 7.3 × 10 ⁸ Ω · cm when 500 V was applied, and the carbon content of the resin covering the core was 0.67 wt%. . Further, a positive charge toner was added to the carrier after this forced deterioration test so that the weight ratio was 5% to prepare a charge amount measurement sample, and the toner charge amount of this sample was measured with a blow-off charge amount measurement device. It was +4.6 μC / g. As a result, it was found that the carrier did not have sufficient durability for the forced deterioration test.

(Example 3)
100 parts by weight of magnetite having a central particle diameter of 100 μm as a core, 1 part by weight of a coating resin that is a mixture of an epoxy resin and a perfluoroalkoxy resin in a weight ratio of 60:40, and 100 parts by weight of methyl ethyl ketone as a solvent are placed in a universal stirrer. After stirring at 120 ° C. to remove the solvent, the mixture was further stirred while heating to 240 ° C. to obtain coated particles. The coated particles were further heated at 270 ° C. for 3 hours in a hot air circulating oven dryer to cure the resin, thereby obtaining a target carrier for electrophotographic development.

The static resistance of this electrophotographic development carrier is 2.4 × 10 ¹² Ω · cm when 500 V is applied, and the carbon content of the resin coating the carrier is measured by combustion / infrared absorption analysis. As a result, it was 0.47 wt%. Further, a positively charged toner was added to this carrier so that the weight ratio would be 5%, and a charge amount measurement sample was prepared. As a result of measuring the toner charge amount of this sample with a blow-off charge amount measurement device, +16.7 μC / g Met.

Further, as a forced deterioration test, 20 g of the carrier was put into a 100 ml polyethylene container and forcedly stirred for 5 hours with a paint shaker. When the static resistance of the carrier after this forced deterioration test was measured, it was 1.6 × 10 ¹¹ Ω · cm when 500 V was applied, and the carbon content of the resin covering the core was 0.41 wt%. . Further, a positive charge toner was added to the carrier after this forced deterioration test so that the weight ratio was 5% to prepare a charge amount measurement sample, and the toner charge amount of this sample was measured with a blow-off charge amount measurement device. It was +14.3 μC / g. As a result, it has been found that the carrier has sufficient durability for the forced deterioration test.

Example 4
In a universal stirrer, 100 parts by weight of magnetite having a central particle size of 100 μm as a core, 1 part by weight of a coating resin that is a mixture of a polyamideimide resin and a perfluoroalkoxy resin in a weight ratio of 50:50, and 100 parts by weight of methyl ethyl ketone as a solvent The mixture was stirred at 120 ° C. to remove the solvent, and further stirred while heating to 240 ° C. to obtain coated particles. The coated particles were further heated at 300 ° C. for 3 hours in a hot air circulating oven dryer to cure the resin, thereby obtaining a target carrier for electrophotographic development.

The static resistance of this electrophotographic development carrier is 6.2 × 10 ¹² Ω · cm when 500 V is applied, and the carbon content of the resin covering the carrier is measured by combustion / infrared absorption analysis. As a result, it was 0.44 wt%. Further, a positive charge toner was added to the carrier so that the weight ratio was 5%, and a charge amount measurement sample was prepared. As a result of measuring the toner charge amount of this sample with a blow-off charge amount measurement device, +15.6 μC / g Met.

Further, as a forced deterioration test, 20 g of the carrier was put into a 100 ml polyethylene container and forcedly stirred for 5 hours with a paint shaker. When the static resistance of the carrier after this forced deterioration test was measured, it was 5.2 × 10 ¹¹ Ω · cm when 500 V was applied, and the carbon content of the resin covering the core was 0.42 wt%. . Further, a positive charge toner was added to the carrier after this forced deterioration test so that the weight ratio was 5% to prepare a charge amount measurement sample, and the toner charge amount of this sample was measured with a blow-off charge amount measurement device. It was +13.8 μC / g. As a result, it has been found that the carrier has sufficient durability for the forced deterioration test.

(Comparative Example 2)
100 parts by weight of magnetite having a central particle diameter of 100 μm as a core, 1 part by weight of a coating resin that is a mixture of silicon resin and perfluoroalkoxy resin in a weight ratio of 50:50, and 100 parts by weight of methyl ethyl ketone as a solvent are put in a universal stirrer. After stirring at 120 ° C. to remove the solvent, the mixture was further stirred while heating to 240 ° C. to obtain coated particles. The coated particles were further heated at 270 ° C. for 3 hours in a hot air circulating oven dryer to cure the resin, thereby obtaining a target carrier for electrophotographic development.

The static resistance value of this electrophotographic development carrier is 2.7 × 10 ¹¹ Ω · cm when 500 V is applied, and the carbon content of the resin coating the carrier is measured by combustion / infrared absorption analysis. As a result, it was 0.37 wt%. Further, a positive charge toner was added to the carrier so that the weight ratio was 5% to prepare a charge amount measurement sample, and the toner charge amount of this sample was measured with a blow-off charge amount measurement device. As a result, +12.6 μC / g Met.

Further, as a forced deterioration test, 20 g of the carrier was put into a 100 ml polyethylene container and forcedly stirred for 5 hours with a paint shaker. When the static resistance of the carrier after this forced deterioration test was measured, it was 1.1 × 10 ⁸ Ω · cm when 500 V was applied, and the carbon content of the resin covering the core was 0.21 wt%. . Further, a positive charge toner was added to the carrier after this forced deterioration test so that the weight ratio was 5% to prepare a charge amount measurement sample, and the toner charge amount of this sample was measured with a blow-off charge amount measurement device. It was +3.6 μC / g. As a result, it was found that the carrier did not have sufficient durability for the forced deterioration test.

The above results are summarized in Table 1.

  From the above results, the carriers for electrophotographic development in Examples 1, 2, 3, and 4 in which the core surface is coated with a coating resin obtained by mixing a fluorine-containing resin, a polyamide-imide resin, and an epoxy resin are fluorine-containing resin and silicon. Compared with the carrier for electrophotographic development in Comparative Examples 1 and 2 in which the coating resin mixed with the resin is coated on the core surface, it has sufficient mechanical durability and electrostatic durability after the durability test. It became clear that it was extremely superior in this point.

Claims (9)

A coating resin obtained by mixing a resin containing fluorine in a molecule with a resin having an amide bond in the molecule and / or a resin having two or more oxirane rings in one molecule,
A carrier for electrophotographic development, wherein the entire surface of a magnetic powder mainly composed of ferrite and / or magnetite is coated.   2. The resin containing fluorine in the molecule includes at least one resin selected from a fluorinated ethylene propylene resin, a perfluoroalkoxy resin, and a trichlorofluoroethylene resin. The carrier for electrophotographic development described in 1.   The resin having an amide bond in the molecule and / or the resin having two or more oxirane rings in one molecule is at least one resin selected from polyimide resin, polyamideimide resin, and epoxy resin. The carrier for electrophotographic development according to claim 1, wherein the carrier for electrophotographic development is contained.   The carrier for electrophotographic development according to any one of claims 1 to 3, wherein the coating amount of the coating resin is 0.1 to 5% by weight.   The carrier for electrophotographic development according to any one of claims 1 to 3, wherein the coating amount of the coating resin is 0.5 to 3% by weight.   The carrier for electrophotographic development according to any one of claims 1 to 5, wherein the coating resin contains 10 to 90% by weight of a resin containing fluorine in the molecule.   The carrier for electrophotographic development according to any one of claims 1 to 6, wherein the magnetic powder has a center particle size of 20 to 120 µm. A mixing step of mixing a resin containing fluorine in the molecule with a resin having an amide bond in the molecule and / or a resin having two or more oxirane rings in one molecule;
A coating step of coating the coating resin produced in the mixing step on the entire surface of the magnetic powder mainly composed of ferrite and / or magnetite;
A method for producing a carrier for electrophotographic development, comprising:   An electrophotographic developer comprising the carrier for electrophotographic development according to claim 1.