JP2009244788A - Carrier core material for electrophotographic developer and method of manufacturing the same, carrier for electrophotographic developer, and electrophotographic developer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a carrier core material for an electrophotographic developer that improves the volume resistivity value, without causing decrease in the magnetic characteristics nor decrease in powder characteristics, and to provide a method of manufacturing the same. <P>SOLUTION: The carrier core material for the electrophotographic developer contains a magnetite or soft ferrite, and has an oxide layer of 0.1 m<SP>2</SP>/g to 0.2 m<SP>2</SP>/g in specific surface area formed on its surface, by carrying out a heat treatment under an inert atmosphere of 300 to 400°C after mechanical agitation for 30 to 180 minutes at a rotating speed of 2,000 to 4,000 rpm, the volume resistivity value being not less than 1.0E+07(Ω cm), when a voltage of 100V is applied. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a carrier core material for an electrophotographic developer used in an electrophotographic dry development method, a method for producing the same, a carrier for an electrophotographic developer, and an electrophotographic developer.

  The electrophotographic dry development method is a method in which a powder toner as a developer is attached to an electrostatic latent image on a photosensitive member, and the attached toner is transferred to a predetermined paper or the like for development. Here, the developer includes a two-component developing method using a two-component developer including toner and carrier powder for electrophotographic developer (hereinafter sometimes referred to as carrier powder) and toner only 1 There is a one-component development method using a component developer. Recently, in most cases, a two-component development method has been used because charge control of the toner is easy, a stable high image quality is obtained, and high-speed development is possible.

  In the two-component development method, the toner is charged using carrier powder, and the toner is conveyed along with the carrier powder. For this reason, carrier powders used in two-component developer for electronic copying machines require various properties such as magnetic properties, electrostatic properties (volume resistance, etc.), powder properties (fluidity, etc.), and durability. Is done. An important factor affecting the image quality of electrophotography is the amount of triboelectric charge between carrier powder and toner. When the triboelectric charge amount is lower than a predetermined value, so-called fogging in which toner is scattered on the blank paper portion of the image is generated, and the copy image quality is lowered. Conversely, when the triboelectric charge amount is higher than the predetermined value, the image quality is low. For this reason, the triboelectric charge amount needs to be adjusted to an appropriate value.

  The carrier powder used in the two-component system has a resin on the surface of a carrier core material (hereinafter sometimes referred to as carrier core material) containing magnetite or soft ferrite (hereinafter sometimes simply referred to as ferrite). It is coated. By taking this configuration, the charge amount of the carrier powder itself and the mechanical durability can be ensured. On the other hand, the electrostatic characteristics of the carrier powder are governed by the characteristics of the ferrite constituting the carrier core material as well as the resin to be coated. In conventional carrier powders, the electrostatic charge of the carrier core material has a low volume resistance value, and the charge of the electrostatic charge image leaks through the carrier core material, disturbing the electrostatic charge image and causing image defects. The problem of causing was seen.

  As a countermeasure against image defects caused by the low volume resistance value of the carrier core material, Patent Document 1 describes a static oxidation treatment at 300 ° C. to 600 ° C. in an atmosphere furnace such as an RH (tubular furnace) furnace or a belt furnace. The method of doing is described. The specific surface area of the oxide film obtained by this oxidation treatment method is 0.1000 to 0.3000 in BET value, and as shown in the SEM photograph of the carrier core material according to the prior art described later shown in FIG. It is a rough coating that exists unevenly on the surface of the material.

  Japanese Patent Application Laid-Open No. 2004-228561 describes an attempt to achieve high image quality by reducing the particle size of the toner, and a technique for reducing the particle size of the carrier accordingly.

JP 2003-34533 A JP-A-2005-300734

However, according to the study by the present inventors, the static oxidation treatment at a high temperature according to the prior art causes a decrease in the magnetic properties and fluidity of the carrier powder. Furthermore, the oxide film formed on the carrier core particle is formed nonuniformly along the grain boundary, as shown in the SEM photograph of FIG. When carrier powder is produced using such carrier core particles, there is a possibility of inconvenience between particles due to surface irregularities and toner transportation, resulting in deterioration of carrier powder characteristics and short life. Problems such as become.

  Further, if the particle diameter of the carrier particles constituting the carrier powder is reduced, the magnetic force per particle is lowered, and there is a problem that the amount of scattering of the carrier powder is increased (so-called fog phenomenon).

The present invention solves the above problems and realizes high image quality of electrophotographic images.
That is, the present invention relates to a carrier core material for an electrophotographic developer capable of improving a volume resistance value without causing a decrease in magnetic characteristics and powder characteristics, a method for producing the same, and an electrophotographic developer produced from the carrier core material. An object of the present invention is to provide a carrier for electrophotography and an electrophotographic developer including the carrier for electrophotographic developer and a predetermined toner.

  In order to solve the above-mentioned problems, the present inventors have conducted intensive studies, and as a result, ferrite is used as a carrier core material in order to improve image quality. The inventors came up with the idea of forming an oxide film on the surface of the core material. And it discovered that the carrier core material in which the oxide film was formed in the surface by the said mechanical high-speed stirring has the outstanding electrostatic characteristic that a sufficient volume resistance value is exhibited. However, it has also been found that the magnetic characteristics such as magnetization under 1 KOe, residual magnetization, and increase in coercive force are reduced by the mechanical high-speed stirring. Therefore, the present inventors have come up with a configuration in which heat treatment for the purpose of magnetization recovery is performed after the mechanical high-speed stirring. As a result, it was found that the obtained electrophotographic carrier core material has a high volume resistance value and a high magnetic force characteristic, and the present invention has been completed.

That is, the first invention for solving the above-described problem is
Including magnetite or soft ferrite,
A specific surface area of 0.1 m ² / g or more and 0.2 m ² / g or less formed by performing heat treatment in an inert atmosphere after stirring on the surface at a rotational speed of 2000 rpm or more and 4000 rpm or less. Having an oxide film,
A carrier core material for an electrophotographic developer, having a volume resistance value of 1.0E + 07 Ω · cm or more when a voltage of 100 V is applied.

The second invention is
The magnetite or soft ferrite has a general formula (M _x Fe _3-x ) O ₄ (where M is at least one selected from the group consisting of Mg, Mn, Ca, Ti, Cu, Zn, Sr, Ni). The carrier core material for an electrophotographic developer according to the first invention, characterized in that the metal is represented by 0 <x <3).

The third invention is
Magnetic force in a magnetic field of 1 KOe is 40 to 75 emu / g
The carrier core material for an electrophotographic developer according to the first or second invention, wherein the residual magnetization is 0.5 to 1.1 emu / g.

The fourth invention is:
After stirring the powder containing magnetite particles or the powder containing soft ferrite particles in the range of rotation speed 2000rpm or more and 4000rpm or less,
A method for producing a carrier core material for an electrophotographic developer, wherein the heat treatment is performed in an inert atmosphere.

The fifth invention is:
An electrophotographic developer carrier characterized in that the carrier core material for an electrophotographic developer according to any one of the first to fourth inventions is coated with a resin.

The sixth invention is:
The carrier core material for an electrophotographic developer according to any one of the first to third inventions, or the carrier for an electrophotographic developer according to the fifth invention,
An electrophotographic developer comprising a predetermined toner.

  According to the present invention, a carrier core material excellent in electrical characteristics and magnetization characteristics is provided. Furthermore, if the carrier powder and the electrophotographic developer produced using the carrier core material are used, a high-quality electrophotographic image can be provided in which carrier adhesion scattering is suppressed and no leakage phenomenon is observed.

  Hereinafter, a carrier core material and a manufacturing method thereof according to the present invention, a carrier for an electrophotographic developer manufactured from the carrier core material, and an electrophotographic developer including the carrier for an electrophotographic developer and a predetermined toner. This will be described in detail.

As described above, the carrier core material according to the present invention contains magnetite or soft ferrite, and after mechanical stirring for 30 minutes or more and 180 minutes or less at a rotational speed of 2000 rpm or more and 4000 rpm or less on the surface, A volume when a voltage of 100 V is applied, having an oxide film with a specific surface area of 0.1 to 0.2 m ² / g, formed by performing heat treatment in an inert atmosphere of at least 400 ° C. and at most 400 ° C. It is a carrier core material that exhibits excellent electrical characteristics that its resistance value is 1.0E + 07 Ω · cm or more.

First, the ferrite used as the carrier core material of the present invention is magnetite represented by Fe ₃ O ₄ or soft ferrite represented by the general formula (M _x Fe _3-x ) O ₄ . In the general formula, the composition M is a solid solution of a spinel oxide that is one kind of Mn, Co, Ni, Cu, Zn, or a mixture of plural kinds of these metal elements. For example, Zn ferrite with X being Zn is an antiferromagnetic material and does not exhibit ferromagnetism, but when zinc is added to other spinel ferrite, it has a function of enhancing magnetism. Ferrite composed of Mn and Zn exhibits extremely high magnetic permeability. Therefore, the ferrite may be selected according to the target characteristics. The carrier core material of the present invention preferably has high magnetization characteristics, low residual magnetization and low coercive force in order to improve image quality.

  The volume resistance value of the carrier core material according to the present invention is 1.0E + 07 Ω · cm or more when a voltage of 100 V is applied. If there is a volume resistance value of this level, it is possible to maintain sufficient triboelectric chargeability with the toner as a carrier core material or even a carrier, and no charge leakage of the electrostatic charge image occurs, The image quality does not deteriorate.

  Furthermore, the carrier core material according to the present invention can maintain a desired magnetic force in a high magnetic field, and the magnetic force in a magnetic field of 1 KOe is 40 to 75 emu / g, and the residual magnetization is 0.5 to 1.1 emu / g. Thus, sufficient carrier characteristics can be obtained. If the coercive force is 10 Oe or less, problems such as scattering of carrier particles and carrier adhesion do not occur.

Furthermore, since the carrier core material according to the present invention has a high apparent density, it has good powder properties such as good filling properties and fluidity, and has good contact chargeability with the toner.

The carrier core material and the carrier according to the present invention can be manufactured by the following steps.
[Weighing and mixing]
When using magnetite represented by Fe ₃ O ₄ , ore-based Fe ₂ O ₃ or iron chloride-based Fe ₂ O is prepared.
When soft ferrite having a composition represented by the general formula (M _x Fe _3-x ) O ₄ is used, Fe ₂ O ₃ can be suitably used as the Fe raw material. As the M component raw material other than Fe, MnCO ₃ and Mn ₃ O ₄ can be suitably used in the case of Mn, and MgCO ₃ and Mg (OH) ₂ can be suitably used in the case of Mg. The M component Fe, M, and Mg can be contained alone, respectively, but if they are contained in combination, there is an advantage that the control range of magnetic properties can be expanded. These raw materials are weighed so that the blending ratio of each metal element becomes a target value, and these are mixed to obtain a metal raw material mixture.

[Crushing and granulation]
The weighed and mixed metal raw material mixture is pulverized by a pulverizer such as a vibration mill. In the pulverization, it is desirable to pulverize to an average particle diameter of 5 μm or less, more preferably 1 μm or less. These pulverized materials are slurried by mixing and stirring in a medium solution. In addition, you may add a grinding | pulverization process further to a mixed pulverized material by dry type before slurrying as needed. The mixing ratio of the raw material powder and the medium liquid is preferably such that the slurry has a solid content concentration of 50 to 90% by mass. The medium liquid is prepared by adding a binder, a dispersant and the like to water. As the binder, for example, polyvinyl alcohol can be suitably used, and the concentration in the medium liquid may be about 0.5 to 2% by mass. As the dispersant, for example, an ammonium polycarboxylate-based one can be preferably used, and the concentration in the medium liquid may be about 0.5 to 2% by mass. In addition, phosphorus, boric acid, or the like can be added as a lubricant or a sintering accelerator. It is preferable to further wet-grind the slurry obtained by mixing and stirring. After this step, a granulated powder having a particle size of 1 to 150 μm is obtained by the granulation step. The obtained granulated powder may be adjusted in particle size in consideration of the final particle size of the product by removing coarse particles and fine particles with a vibration sieve. In order to set the final product particle size (volume average particle size) to 20 to 120 μm, it is preferable to prepare such that the particle size of the individual particles of the granulated powder falls within the range of 30 to 130 μm.

[Baking]
Next, the granulated product is subjected to main baking at a temperature of 1000 ° C. to 1300 ° C. for 1 to 24 hours. The firing atmosphere at this time is preferably carried out in an inert gas atmosphere having an oxygen concentration of less than 0.1% by volume, preferably 0.01% or less. If the oxygen concentration in this firing atmosphere is 0.1% or less, the formation of a hematite phase can be prevented and the desired magnetization can be obtained. Depending on the composition of the ferrite, a temporary firing step may be added as appropriate. The atmosphere of the calcination step may be the same conditions as in the main firing, or in air as long as it is 500 ° C. or lower.

(Mechanical stirring)
The obtained fired product is pulverized and classified to prepare a target particle size. Next, mechanical high-speed stirring treatment is performed on the particles of the fired product at room temperature in the air or in an atmosphere in which the oxygen concentration is controlled to 20 to 100% by volume. The stirring rotation speed is preferably 2000 rpm to 4000 rpm, more preferably 2500 rpm to 3500 rpm. The stirring time is 30 minutes to 180 minutes, and the temperature during the treatment is 50 to 150 ° C.

As a machine used for stirring, for example, a general high-speed stirrer such as a super mixer can be used. By the stirring, frictional heat or mechanochemical reaction occurs due to collision between the particles or between the blades and particles of the stirrer or between the side surface of the stirrer and the particles, and also with shearing force. As a result, a dense and strong oxide film having a high volume resistance value is formed on the entire surface of the fired product by the frictional heat or mechanochemical reaction. If the rotational speed is 2000 rpm or more, sufficient mechanical energy is supplied to cause frictional heat and mechanochemical reaction. Moreover, if the rotational speed is 4000 rpm or less, cracking of particles due to excessive mechanical energy can be avoided. Moreover, the stirring time in stirring is 30 minutes-180 minutes, More preferably, it is 60 minutes-120 minutes. If the stirring time is 30 minutes or more, a sufficient oxide film is formed. On the other hand, if the stirring time is 180 minutes or less, it is possible to avoid a decrease in magnetic properties due to particle breakage.

  The carrier core material according to the present invention has a smooth, uniform and dense oxide film formed on the particle surface by the mechanical high-speed stirring. And since a favorable oxide film is formed and problems, such as peeling, do not arise because a stirring rotation speed and stirring time are the said range, satisfactory electrostatic characteristics are acquired. Specifically, it has a volume resistance value of 1.0E + 07 Ω · cm or more when a voltage of 100 V is applied.

〔Heat treatment〕
Next, the fired product is heat-treated in an atmosphere furnace. The purpose of this treatment is to recover the decrease in magnetization caused by the load that the fired product has received by the mechanical treatment in the previous step.
As the atmosphere furnace, a closed batch furnace having a low influence of external oxygen or the like is preferable. The atmosphere is preferably an inert atmosphere such as nitrogen or argon. As temperature, 250 to 500 degreeC is preferable. More preferably, 300-400 degreeC is preferable, and as processing time, 3 minutes-60 minutes are preferable. If the temperature is 300 ° C. or higher, the thermal energy is sufficient to recover the magnetization drop. If the temperature is 400 ° C. or lower, sintering of the particles during the heat treatment can be avoided, and impurities such as impurities in the inert atmosphere can be avoided. It becomes difficult to be affected.

[Disintegration, classification]
The obtained fired product is coarsely pulverized by, for example, hammer mill pulverization, etc., and then subjected to primary classification using, for example, an airflow classifier to remove non-shaped particles and fine particles, and further, the particle size is determined using a vibration sieve or an ultrasonic sieve. It is desirable to have Thereafter, a non-magnetic component is removed by applying a magnetic separator, and a carrier core material having a volume average particle size of 20 to 120 μm can be obtained.

  The carrier core material thus obtained can be used as a carrier by itself. Furthermore, it is also preferable to carry out resin coating on the carrier core material to make a carrier.

[Resin coating]
Resin coating is applied to the obtained carrier core material to produce carrier powder. A silicone resin is preferable as the coating resin. In order to perform resin coating, the resin is generally diluted with a solvent and coated on the surface of the carrier core material. Any solvent may be used as long as the resin is soluble. If a resin soluble in an organic solvent is used, toluene, xylene, methyl ethyl ketone, methyl isobutyl ketone, methanol or the like can be used as the solvent. If the predetermined resin is a water-soluble resin or an emulsion type resin, water can be used.

  In order to coat the surface of the carrier core material with the predetermined resin diluted with a solvent, a dipping method, a spray method, a brush coating method, or the like can be applied. When the carrier core material coated with the predetermined resin is dried, carrier powder can be obtained. In addition to resin coating by such a wet method, the carrier powder can also be obtained by a dry method in which a predetermined resin powder is adhered to the surface of the carrier core material.

Regardless of the wet method or the dry method, it is preferable to bake the predetermined resin coated on the surface of the carrier core material. For example, it is preferable to bake the predetermined resin coated on the surface of the carrier core material by an external heating method or an internal heating method using a fixed or fluid electric furnace, a rotary electric furnace, a burner furnace, or the like. Baking with microwaves is also possible. The baking temperature varies depending on the predetermined resin, but a temperature higher than the melting point or higher than the glass transition point is required. When the predetermined resin is a thermosetting resin or a condensation type resin, it is necessary to raise the temperature to a temperature at which the curing proceeds sufficiently.

[Electrophotographic developer]
A two-component electrophotographic developer can be obtained by mixing the obtained carrier powder and a predetermined toner.

  Hereinafter, the present invention will be described in detail based on examples. In addition, this invention is not limited to this Example. The measurement was performed as follows.

[Volume resistance measurement]
A method for measuring a volume resistance value (electric resistance) at applied voltages of 10 V and 100 V will be described.
On a horizontally placed insulating plate (for example, an acrylic plate coated with Teflon (registered trademark)), two brass plates having a thickness of 2 mm whose surfaces are electropolished as electrode plates have a distance between the electrodes of 2 mm. Arrange so that. The two electrode plates are installed such that the normal direction is the horizontal direction. After inserting 200 ± 1 mg of the powder to be measured into the gap between the two electrode plates, a magnet having a cross-sectional area of 240 mm ² is arranged behind each electrode plate, and the powder to be measured is placed between the electrode plates. Form a bridge. In this state, a DC voltage of 1000 V is applied between the electrode plates, and the value of the current flowing through the powder to be measured is measured by the four-terminal method. From the current value, the distance between the electrode plates of 2 mm, and the cross-sectional area of 240 mm ² , the electric resistance of the powder to be measured (the dimension corresponding to the volume resistance) is calculated. Various magnets can be used as long as the powder can form a bridge. In the examples described later, a permanent magnet (ferrite magnet) having a surface magnetic flux density of 1000 gauss or more is used.

[Saturation magnetization measurement]
Saturation magnetization (σs) was measured by VSM (manufactured by Toei Kogyo Co., Ltd., VSM-P7).

[Measurement of magnetization under 1 KOe]
The magnetization (σ ₁₀₀₀ ) measurement under 1 KOe was performed by VSM (manufactured by Toei Kogyo Co., Ltd., VSM-P7).

[Residual magnetization measurement]
The residual magnetization (σr) was measured by VSM (manufactured by Toei Kogyo Co., Ltd., VSM-P7).

[Coercivity measurement]
The coercive force (Hc) was measured by VSM (manufactured by Toei Industry Co., Ltd., VSM-P7).

[Specific surface area]
The specific surface area was measured by the BET method.

[Average particle size measurement]
The average particle size was measured with a Microtrac particle size analyzer (Nikkiso Co., Ltd., Microtrac Model 9320-X100).

[Apparent density of powder]
The apparent density of the powder was measured according to JISZ-2504.

[Fluidity]
The fluidity was measured according to JISZ-2052.

<Preparation of fired product (ferrite)>
As the Fe raw material powder, Fe ₂ O ₃ powder finely pulverized to an average particle diameter D50 of about 1 μm was prepared.
On the other hand, 1.0% by mass of an ammonium polycarboxylate dispersant as a dispersant, 0.05% by mass of “SN Wet 980” manufactured by San Nopco Co., Ltd., and 0.02% of polyvinyl alcohol as a binder in water. A liquid (medium liquid) added by mass% was prepared.
The weighed Fe raw material powder was put into a medium solution and stirred to obtain a slurry having a concentration of 76% by mass of the added substance. The slurry was wet pulverized with a wet ball mill and stirred for a while. Then, the said slurry was sprayed in the hot air of about 180 degreeC with the spray dryer, and the dry granulated material with a particle size of 10-200 micrometers was obtained.

  From this granulated material, coarse particles were separated using a sieve mesh having a mesh size of 61 μm, fine particles were separated using a sieve mesh having a mesh size of 25 μm, and then fired at 1000 ° C. for 5 hours in a nitrogen atmosphere to be ferritized. The ferritized fired product was pulverized with a hammer mill, fine powder was removed using an air classifier, and the particle size was adjusted with a vibrating screen having a mesh size of 54 μm to obtain a fired product.

[Example 1]
5 kg of the obtained fired product was subjected to a mechanical treatment using a super mixer (FS-GS-10JD type, manufactured by Fukae Pautech Co., Ltd.) with a stirring speed of 3000 rpm and a stirring time of 120 minutes. In addition, the temperature at the time of stirring was 80 degreeC. And the carrier core material which concerns on Example 1 was obtained by performing the heat processing for 5 minutes in process temperature 300 degreeC and nitrogen to the baked material which performed the said mechanical process. Table 1 shows the magnetic properties, electrostatic properties, and powder properties of this carrier core material. Further, an SEM photographic image of 3000 times the carrier core material is shown in FIG.

[Example 2]
Using a super mixer (FS-GS-10JD type, manufactured by Fukae Pautech Co., Ltd.), 5 kg of a calcined product prepared in the same manner as in Example 1 was mechanically treated with a stirring speed of 3500 rpm and a stirring time of 60 minutes. Was given. In addition, the temperature at the time of stirring was 90 degreeC. And the carrier core material which concerns on Example 2 was obtained by performing the heat processing for 5 minutes in process temperature 300 degreeC nitrogen with the RH furnace to the baked material which performed the said mechanical process. Table 1 shows the magnetic properties, electrostatic properties, and powder properties of this carrier core material.

Example 3
Using a super mixer (FS-GS-10JD type, manufactured by Fukae Pautech Co., Ltd.), 5 kg of the calcined product prepared in the same manner as in Example 1 was mechanically treated with a stirring speed of 2500 rpm and a stirring time of 180 minutes. Was given. In addition, the temperature at the time of stirring was 90 degreeC. And the carrier core material which concerns on Example 3 was obtained by performing the heat processing for 5 minutes in 300 degreeC nitrogen treatment temperature in the RH furnace to the baked material which performed the said mechanical process. Table 1 shows the magnetic properties, electrostatic properties, and powder properties of this carrier core material.

Example 4
Using a super mixer (FS-GS-10JD type, manufactured by Fukae Pautech Co., Ltd.), 5 kg of the calcined product whose particle size was adjusted in the same manner as in Example 1, mechanical treatment at a stirring speed of 3000 rpm and a stirring time of 120 minutes. Was given. In addition, the temperature at the time of stirring was 80 degreeC. And the carrier core material which concerns on Example 4 was obtained by performing the heat processing for 5 minutes in process temperature 400 degreeC nitrogen with the RH furnace to the baked material which performed the said mechanical process. Table 1 shows the magnetic properties, electrostatic properties, and powder properties of this carrier core material.

Example 5
Using a super mixer (FS-GS-10JD type, manufactured by Fukae Pautech Co., Ltd.), 5 kg of the calcined product whose particle size was adjusted in the same manner as in Example 1, mechanical treatment at a stirring speed of 3000 rpm and a stirring time of 120 minutes. Was given. In addition, the temperature at the time of stirring was 80 degreeC. And the carrier core material which concerns on Example 5 was obtained by performing the heat processing for 3 minutes in process temperature 300 degreeC nitrogen by the RH furnace to the baked material which performed the said mechanical process. Table 1 shows the magnetic properties, electrostatic properties, and powder properties of this carrier core material.

Example 6
Using a super mixer (FS-GS-10JD type, manufactured by Fukae Pautech Co., Ltd.), 5 kg of the calcined product whose particle size was adjusted in the same manner as in Example 1, mechanical treatment at a stirring speed of 3000 rpm and a stirring time of 120 minutes. Was given. In addition, the temperature at the time of stirring was 80 degreeC. And the carrier core material which concerns on Example 6 was obtained by performing the heat processing for 30 minutes in process temperature 300 degreeC nitrogen with the RH furnace to the baked material which performed the said mechanical process. Table 1 shows the magnetic properties, electrostatic properties, and powder properties of this carrier core material.

Example 7
Using a super mixer (FS-GS-10JD type, manufactured by Fukae Pautech Co., Ltd.), 5 kg of the calcined product whose particle size was adjusted in the same manner as in Example 1, mechanical treatment at a stirring speed of 3000 rpm and a stirring time of 120 minutes. Was given. In addition, the temperature at the time of stirring was 80 degreeC. And the carrier core material which concerns on Example 7 was obtained by performing the heat processing for 60 minutes in process temperature 300 degreeC nitrogen with the RH furnace to the baked material which performed the said mechanical process. Table 1 shows the magnetic properties, electrostatic properties, and powder properties of this carrier core material.

[Comparative Example 1]
Using a super mixer (FS-GS-10JD type, manufactured by Fukae Pautech Co., Ltd.), 5 kg of a calcined product prepared in the same manner as in Example 1 was mechanically treated with a stirring speed of 3000 rpm and a stirring time of 120 minutes. Was given. In addition, the temperature at the time of stirring was 80 degreeC. And the carrier core material which concerns on the comparative example 1 was obtained by performing the heat processing for 5 minutes in process temperature 200 degreeC nitrogen with the RH furnace to the baked material which performed the said mechanical process. Table 1 shows the magnetic properties, electrostatic properties, and powder properties of this carrier core material.

[Comparative Example 2]
5 kg of the calcined product whose particle size was prepared in the same manner as in Example 1 was subjected to mechanical treatment with a super mixer (FS-GS-10JD, manufactured by Fukae Pautech Co., Ltd.) at a stirring speed of 3000 rpm and a stirring time of 120 minutes. . In addition, the temperature at the time of stirring was 80 degreeC. And the carrier core material which concerns on the comparative example 2 was obtained by performing the heat processing for 5 minutes in process temperature 600 degreeC nitrogen with the RH furnace to the baked material which performed the said mechanical process. Table 1 shows the magnetic properties, electrostatic properties, and powder properties of this carrier core material.

[Comparative Example 3]
5 kg of the calcined product whose particle size was prepared in the same manner as in Example 1 was subjected to mechanical treatment with a super mixer (FS-GS-10JD, manufactured by Fukae Pautech Co., Ltd.) at a stirring speed of 3000 rpm and a stirring time of 120 minutes. . In addition, the temperature at the time of stirring was 80 degreeC. And the carrier core material which concerns on the comparative example 3 was obtained by giving to the baked material which performed the said mechanical process for 5 minutes in process temperature 300 degreeC nitrogen by RH furnace. Table 1 shows the magnetic properties, electrostatic properties, and powder properties of this carrier core material.

[Comparative Example 4]
5 kg of the calcined product whose particle size was prepared in the same manner as in Example 1 was subjected to mechanical treatment with a super mixer (FS-GS-10JD type, manufactured by Fukae Pautech Co., Ltd.) at a stirring rotation speed of 3000 rpm and a stirring treatment time of 240 minutes. . In addition, the temperature at the time of stirring was 100 degreeC. And the carrier core material which concerns on the comparative example 4 was obtained by giving to the baked material which performed the said mechanical process for 5 minutes in process temperature 300 degreeC nitrogen by RH furnace. Table 1 shows the magnetic properties, electrostatic properties, and powder properties of this carrier core material.

[Comparative Example 5]
The calcined product whose particle size was adjusted in the same manner as in Example 1 was subjected to a heat treatment for 100 minutes in an atmosphere at a processing temperature of 500 ° C. in an RH furnace to obtain a carrier core material according to Comparative Example 5. Table 1 shows the magnetic properties, electrostatic properties, and powder properties of this carrier core material. Further, an SEM photograph image of the carrier core material 3000 times is shown in FIG.

[Summary of Examples 1-7 and Comparative Examples 1-5]
Example 1 in which heat treatment was performed in an inert atmosphere of 300 ° C. or more and 400 ° C. or less after mechanical stirring for 30 minutes or more and 180 minutes or less in the range of 2000 rpm or more and 4000 rpm or less using a super mixer. 7 has a specific surface area of 0.1-0.
It had an oxide film of 2 m ² / g, and the volume resistance value when a voltage of 100 V was applied was 1.0E + 07 Ω · cm or more. Furthermore, the magnetic properties of the carrier cores according to Examples 1 to 7 were excellent because the magnetization value in a magnetic field of 1 KOe was high, and the residual magnetization and coercive force values were low. Moreover, the powder characteristics of the carrier core materials according to Examples 1 to 7 were excellent because of high apparent density and good fluidity.

On the other hand, the carrier core material according to Comparative Example 1 in which the heat treatment temperature was as low as 200 ° C. did not satisfy the magnetization recovery because the heat treatment temperature was low, and the magnetic characteristics were σ ₁₀₀₀ of 63.4 emu / g. It was low.

In addition, the carrier core material according to Comparative Example 2 in which the heat treatment temperature was as high as 600 ° C. has a high heat treatment temperature, so that the particles are sintered together, and the powder properties are as low as 2.18 g / cm ^{3 in} apparent density. The fluidity was as high as 24.5 s / 50 g and the fluidity was poor.

  Further, in the carrier core material according to Comparative Example 3 in which the stirring rotation speed was 500 rpm, an oxide film was not formed because the mechanical oxidation treatment was weak, and the volume resistance value was as low as 5.1E + 05 Ω · cm.

  Moreover, although the stirring rotation speed was 3000 rpm, the carrier core material according to Comparative Example 4 in which the stirring time was as long as 240 minutes was strong in mechanical oxidation treatment, and the formed oxide film was peeled off. It was as low as 5.6E + 06 Ω · cm.

In Comparative Example 5 according to the prior art, the oxide film was non-uniform and the volume resistance value was as low as 5.6E + 05 Ω · cm. The apparent density was as low as 2.16 g / cm ³ , the fluidity was as high as 24.4 s / 50 g, and the fluidity was poor.

It is a SEM photograph of the carrier core material concerning the present invention. It is a SEM photograph of the carrier core material concerning the conventional technology.

Claims (6)

Including magnetite or soft ferrite,
A specific surface area of 0.1 m ² / g or more and 0.2 m ² / g or less formed by performing heat treatment in an inert atmosphere after stirring on the surface at a rotational speed of 2000 rpm or more and 4000 rpm or less. Having an oxide film,
A carrier core material for an electrophotographic developer, having a volume resistance value of 1.0E + 07 Ω · cm or more when a voltage of 100 V is applied. The magnetite or soft ferrite has a general formula (M _x Fe _3-x ) O ₄ (where M is at least one selected from the group consisting of Mg, Mn, Ca, Ti, Cu, Zn, Sr, Ni). 2. The carrier core material for an electrophotographic developer according to claim 1, wherein the carrier core material is represented by metal, 0 <x <3). Magnetic force in a magnetic field of 1 KOe is 40 to 75 emu / g
The carrier core material for an electrophotographic developer according to claim 1 or 2, wherein the residual magnetization is 0.5 to 1.1 emu / g. After stirring the powder containing magnetite particles or the powder containing soft ferrite particles in the range of rotation speed 2000rpm or more and 4000rpm or less,
A method for producing a carrier core material for an electrophotographic developer, wherein the heat treatment is performed in an inert atmosphere.   The carrier for an electrophotographic developer according to any one of claims 1 to 4, wherein the carrier core material for an electrophotographic developer is coated with a resin. The carrier core material for an electrophotographic developer according to any one of claims 1 to 3, or the carrier for an electrophotographic developer according to claim 5,
An electrophotographic developer comprising a predetermined toner.