JP2017122878A - Magnetic carrier, two-component developer, developer for replenishment, and image forming method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnetic carrier usable in long life developer which can output a high quality image for a long period of time even to a severe environmental variation.SOLUTION: There is provided a magnetic carrier having a resin coating layer formed on the surface of a magnetic carrier core that contains a resin A for coating which is obtained by polymerization of a monomer containing (meth)acrylic acid ester having an alicyclic hydrocarbon group and has an acid value of 0.0 mgKOH/g or more and 3.0 mgKOH/g or less, a resin B for coating which is obtained by polymerization of a monomer containing (meth)acrylic acid and has an acid value of 4.0 mgKOH/g or more and 50.0 mgKOH/g or less, and one or more or two or more inorganic particles selected from metal oxide particles containing a metal element selected from Mg, Al, Zn, Ca, Sr and Ti and/or carbonate salt particles, where when the total resin component contained in the resin coating layer is 100 pts.mass, a content of the resin A for coating is 10 pts.mass or more and 90 pts.mass or less, a content of the resin B for coating is 10 pts.mass or more and 90 pts.mass or less, and a content of the inorganic particles is 1.0 pts.mass or more 50.0 pts.mass or less.SELECTED DRAWING: None

Description

  The present invention relates to a magnetic carrier used in an image forming method for visualizing an electrostatic charge image using electrophotography.

In recent years, electrophotographic methods have been widely used such as copying machines and printers, and are required to be able to deal with various objects such as fine lines, lowercase letters, photographs or color originals. In addition, high image quality, high quality, high speed, and continuity are also demanded, and these demands are expected to increase in the future.
As carrier particles that satisfy these various requirements, composite particles having a specific gravity of about 2.0 to 5.0 that do not break the toner even when the speed is increased or continuous are widely used.
The demand for improving the characteristics of carrier particles is not limited, and in particular, in order to achieve high image quality of full-color images, it is required that the toner having a small particle diameter is excellent in chargeability as a magnetic carrier. .
In other words, it is important that a uniform charge amount is given to the toner, the charge amount does not change even after long-term use, and further, the charge amount does not change due to environmental changes. There is a strong demand for the magnetic carrier to be excellent in durability.
Conventionally, in order to improve the durability of a magnetic carrier, there is (1) a magnetic carrier in which a silicone resin coating layer containing a silane coupling agent or the like is provided on the surface of magnetic core particles (see Patent Document 1). In addition, there is (2) a magnetic carrier (see Patent Document 2) in which a coupling agent is treated on the surface of the magnetic core particles and further coated with a silicone resin. Furthermore, (3) a magnetic carrier having a coating layer made of a resin having a functional group capable of reacting with an aminosilane coupling agent on the particle surface of the magnetic core material particles (see Patent Document 3) is known.
However, the magnetic carrier having excellent durability is desired to be further improved at the most demanded point.
Furthermore, in order to improve the durability, there are examples in which a coating resin, a coating state is improved, or an additive is added (see Patent Documents 4, 5, and 6). Although these examples improve durability in various environments, further improvements are required in terms of durability when the environment changes.

Japanese Patent Laid-Open No. 7-104522 JP-A-62-212463 Japanese Patent Laid-Open No. 4-198946 JP 2007-333886 A JP2013-127487A JP 2011-247777 A

  An object of the present invention is to provide a magnetic carrier that solves the above-described problems. Specifically, it is a long-life developer that can output a high-quality image over a long period of time even under severe environmental fluctuations. Another object of the present invention is to provide a magnetic carrier, a two-component developer, a replenishment developer, and an image forming method that can be used.

The present invention is a magnetic carrier having a resin coating layer formed on the surface of a magnetic carrier core,
The resin coating layer is
i) a coating resin A having an acid value of 0.0 mgKOH / g or more and 3.0 mgKOH / g or less, obtained by polymerizing a monomer containing an acrylate or methacrylate having an alicyclic hydrocarbon group;
ii) Coating resin B having an acid value of 4.0 mgKOH / g or more and 50.0 mgKOH / g or less obtained by polymerizing a monomer containing acrylic acid or methacrylic acid;
iii) metal oxide particles containing a metal element selected from Mg, Al, Zn, Ca, Sr, and Ti, and / or one or more inorganic particles selected from carbonate particles,
When the total resin component contained in the resin coating layer is 100 parts by mass,
i) The content of the coating resin A is 10 parts by mass or more and 90 parts by mass or less,
ii) The content of the coating resin B is 10 parts by mass or more and 90 parts by mass or less,
iii) The content of the inorganic particles is 1.0 part by mass or more and 50.0 parts by mass or less.
Further, the present invention is a two-component developer containing a toner having toner particles containing a binder resin and a colorant, and a magnetic carrier,
The present invention relates to a two-component developer, wherein the magnetic carrier is a magnetic carrier having the above structure.
The present invention also includes a charging step for charging the electrostatic latent image carrier, an electrostatic latent image forming step for forming an electrostatic latent image on the surface of the electrostatic latent image carrier, and the electrostatic latent image as two components. Development using a developer to form a toner image, a transfer step of transferring the toner image to a transfer material with or without an intermediate transfer member, and the transfer of the transferred toner image to the transfer material A fixing process for fixing to the material, and in accordance with a decrease in the toner concentration of the two-component developer in the developing device, the replenishment developer is replenished to the developing device, and the excess magnetic carrier in the developing device A replenishment developer for use in an image forming method discharged from a developing device as necessary,
The replenishment developer contains a replenishment magnetic carrier and a toner having toner particles containing a binder resin, a colorant, and a release agent,
The replenishment developer contains the toner in a blending ratio of 2 parts by mass or more and 50 parts by mass or less with respect to 1 part by mass of the magnetic carrier for replenishment.
The replenishing magnetic carrier is a magnetic carrier having the above-described configuration.
The present invention also provides a charging step for charging the electrostatic latent image carrier, an electrostatic latent image forming step for forming an electrostatic latent image on the surface of the electrostatic latent image carrier, and the electrostatic latent image in the developing device. Development using a two-component developer to form a toner image, a transfer step of transferring the toner image to a transfer material with or without an intermediate transfer member, and transferring the transferred toner image to a transfer material With a fixing process to fix the toner to the developer in accordance with the decrease in the toner concentration of the two-component developer in the developer unit, and an excess magnetic carrier is required in the developer unit. An image forming method for discharging from a developing device according to
The replenishment developer contains a replenishment magnetic carrier and a toner having toner particles containing a binder resin, a colorant, and a release agent,
The replenishment developer contains the toner in a blending ratio of 2 parts by mass or more and 50 parts by mass or less with respect to 1 part by mass of the magnetic carrier for replenishment.
The replenishing magnetic carrier is a magnetic carrier having the above-described configuration.
Furthermore, the present invention provides a charging step for charging the electrostatic latent image carrier, an electrostatic latent image forming step for forming an electrostatic latent image on the surface of the electrostatic latent image carrier, and the electrostatic latent image as two components. Development using a developer to form a toner image, a transfer step of transferring the toner image to a transfer material with or without an intermediate transfer member, and the transfer of the transferred toner image to the transfer material An image forming method having a fixing step of fixing to a material,
The present invention relates to an image forming method using the two-component developer having the above-described configuration as the two-component developer.

  Even under severe usage conditions of environmental fluctuations, there is little change in density over a long period of time, and a high-quality image can be output.

It is the schematic of the image forming apparatus which can use the magnetic carrier of this invention. It is the schematic of the image forming apparatus which can use the magnetic carrier of this invention. It is the schematic of the coating resin content prescription | regulation method in a GPC molecular weight distribution curve. It is the schematic of the coating resin content prescription | regulation method in a GPC molecular weight distribution curve.

  The magnetic carrier coating resin of the present invention is a polymer (coating resin A) obtained by polymerizing a monomer containing an acrylate or methacrylate having an alicyclic hydrocarbon group, an acrylic monomer or a methacrylic monomer. A polymer obtained by polymerizing monomers, having a polar group and an acid value of 4.0 mgKOH / g or more and 50.0 mgKOH / g or less (coating resin B), and Mg, Al It contains one or more inorganic particles selected from metal oxide particles containing a metal element selected from Zn, Ca, Sr, and Ti, and / or carbonate particles. It is preferable that these resins A and B and inorganic particles are mixed and sufficiently compatible. In the following description, (meth) acrylic acid represents acrylic acid or methacrylic acid, and (meth) acrylic acid ester represents acrylic acid ester or methacrylic acid ester.

  The role of the resin coating layer is to provide a stable charge to the toner in the long term. Therefore, the most important thing is that the coating resin has a high coating strength and the surface of the coating resin does not change due to stress such as friction. In order to obtain such effects, fluorine-containing acrylic resins and silicone resins have been used as conventional techniques. However, if the copying machine is continuously used under severe usage conditions such as environmental fluctuations and continuous output, the resin may be scraped or peeled off, resulting in trouble with images. This is because the fluorine-containing acrylic resin and the silicone resin are hard and brittle.

  Therefore, the present inventors have tried to overcome the above-mentioned problems by using a magnetic carrier having a resin coating layer to which inorganic particles are added in a resin composition having a certain acid value. Thereby, it turned out that the adhesiveness of the resin composition of a resin coating layer and a magnetic carrier core improves, and coating-film intensity | strength also improves. The present inventors consider that the improvement in adhesion is an influence of the interaction between the magnetic carrier core or the resin used for the magnetic carrier core and the polar group of the coating resin.

  However, further improvement is necessary to improve the property of becoming hard and brittle by improving the coating strength of the resin coating layer.

  On the other hand, by using a (meth) acrylic ester-based resin composition having an alicyclic hydrocarbon group, the coating surface of the magnetic carrier surface can be made uniform, and contamination due to toner-derived deposits It is known to form a resin coating layer with a small amount. However, when used in a harsh environment for a long period of time, the coating film is likely to be thinned, and it may be difficult to impart a stable charge to the toner.

  Then, although the examination which adds microparticles | fine-particles to the resin composition which uses the (meth) acrylic acid ester-type resin which has an alicyclic hydrocarbon group in a resin coating layer was also performed, It did not come.

  Moreover, examination which gives a fixed acid value to the resin composition which uses the (meth) acrylic acid ester-type resin which has an alicyclic hydrocarbon group was performed. As a result, the adhesion with the magnetic carrier core was improved, but the charging stability effect for a long time could not be obtained as the present inventors imagined. As a result of intensive studies, the present inventors have found that the smoothness of the resin coating layer becomes lower as the storage period is longer after the resin is produced. Probably due to the electron donating property of the alicyclic hydrocarbon group of the coating resin A and the electron withdrawing property of the polar group of the coating resin B, the resin may self-aggregate and the coated surface may not be uniform. The present inventors consider that there is a possibility.

  From these results, the present inventors blended a (meth) acrylic acid ester resin composition having an alicyclic hydrocarbon group, a resin composition having a certain acid value, and fine particles to obtain a magnetic carrier core. The coating was performed. As a result, it was found that not only the coating film strength of the resin was improved, but also the toughness of the coating film was improved, thereby solving the above problems.

  Resin composition using (meth) acrylic ester resin having an alicyclic hydrocarbon group in a gap between molecules in a resin composition in which fine particles are added to a resin composition having a certain acid value It is considered that the molecular chains are entangled in a complex manner due to the penetration of and the toughness of the coating film is improved.

  Furthermore, as a result of intensive studies, it has been found that the use of a specific metal oxide or carbonate as fine particles produces a great effect, leading to the present invention.

  The resin coating layer used in the magnetic carrier of the present invention is obtained by polymerizing a monomer containing a (meth) acrylic acid ester having an alicyclic hydrocarbon group, and has an acid value of 0.0 mgKOH / g or more and 3.0 mgKOH. / G or less coating resin A, and a coating resin B obtained by polymerizing a monomer containing (meth) acrylic acid and having an acid value of 4.0 mgKOH / g or more and 50.0 mgKOH / g or less, Mg, Al It is characterized by containing one or more inorganic particles selected from metal oxide particles containing a metal element selected from Zn, Ca, Sr, and Ti, and / or carbonate particles.

  The (meth) acrylic acid ester-based resin composition having an alicyclic hydrocarbon group used for the coating resin A makes the coating surface of the resin coated on the surface of the magnetic carrier core smooth and adheres toner-derived components. It suppresses the charging and suppresses the decrease in charging ability. However, the present invention also has an effect of reducing the viscosity of the resin composition and improving the toughness of the coating film when blended with a resin having an acid value.

  When there is no (meth) acrylic acid ester monomer having an alicyclic hydrocarbon group, the resin coating layer of the magnetic carrier deteriorates during long-term use, and the image density change and image quality deteriorate.

  The (meth) acrylic acid ester monomer having a preferred alicyclic hydrocarbon group used in the present invention is, for example, cyclobutyl acrylate, cyclopentyl acrylate, cyclohexyl acrylate, cycloheptyl acrylate, dicyclopentenyl acrylate, Examples include dicyclopentanyl acrylate, cyclobutyl methacrylate, cyclopentyl methacrylate, cyclohexyl methacrylate, cycloheptyl methacrylate, dicyclopentenyl methacrylate, and dicyclopentanyl methacrylate. One or more of these monomers may be selected and used.

  The (meth) acrylic acid ester monomer having an alicyclic hydrocarbon group is preferably contained in an amount of 50 parts by mass or more and 90 parts by mass or less when the total monomer of the coating resin A is 100 parts by mass.

  The acid value of the coating resin A is 0 mgKOH / g or more and 3.0 mgKOH / g or less. Preferably they are 0 mgKOH / g or more and 2.8 mgKOH / g or less, More preferably, they are 0 mgKOH / g or more and 2.5 mgKOH / g or less. When the acid value exceeds 3.0 mgKOH / g, the resin tends to self-aggregate due to the influence of the acid value, and the toughness of the resin coating layer is lowered. In addition, the smoothness of the surface layer of the resin coating layer tends to decrease.

  The acid value can be controlled by using a monomer having a polar group such as a carboxy group or a sulfonic acid group and adjusting the monomer addition amount. However, since it is preferable to reduce the acid value of the resin A as much as possible, it is preferable not to use a monomer having a polar group. Even when only the ester monomer is used, a slight acid value may be generated, but it is considered that a part of the ester is decomposed to generate a carboxy group during polymerization.

  Further, the coating resin A is preferably a resin obtained by copolymerizing a (meth) acrylic acid ester monomer having an alicyclic hydrocarbon group and a macromonomer. Compared with the case where the macromonomer is not used for the coating resin A, the entanglement of the molecular chains is more complicated and strong, so that the toughness of the coating film is further improved.

  The macromonomer is at least one selected from methyl acrylate, methyl methacrylate, butyl acrylate, butyl methacrylate, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, styrene, acrylonitrile, and methacrylonitrile. A monomer obtained by polymerizing the above monomers is preferred.

  The weight average molecular weight (Mw) of the macromonomer is preferably 2,000 or more and 10,000 or less, more preferably 3,000 or more and 8,000 or less.

  The content of the macromonomer is preferably 5.0 parts by mass or more and 40.0 parts by mass or less when the total monomer of the coating resin A is 100 parts by mass.

  The acid value of the coating resin B is 4.0 mgKOH / g or more and 50.0 mgKOH / g or less. Preferably, it is 4.5 mgKOH / g or more and 40.0 mgKOH / g or less. When the coating resin B has an acid value in the above range, the adhesion between the magnetic carrier core and the trunk fine particles is improved, and the coating film strength is also improved. If the acid value is less than 4.0 mgKOH / g, the effect of adhesion between the magnetic carrier core and the trunk fine particles and the improvement of the coating strength cannot be obtained. In addition, the charging ability becomes unstable, and the environmental difference increases. On the other hand, if it exceeds 50.0 mgKOH / g, the resin coating layer tends to absorb moisture, and the charging ability becomes unstable during long-term use, particularly in a high-temperature and high-humidity environment, and the image density and the like become unstable.

  The (meth) acrylic monomer in the coating resin B is not particularly limited as long as it has a polar group that imparts an acid value to the coating resin B. Preferable polar groups that give an acid value to the coating resin B include carboxy groups and sulfonic acid groups. Specific examples of the (meth) acrylic monomer include acrylic acid, methacrylic acid, and vinyl sulfonic acid. By increasing the ratio of monomers having polar groups such as acrylic acid and methacrylic acid, the acid value is improved. Therefore, the acid value can be controlled by adjusting these monomer ratios.

The inorganic particles used in the present invention are selected from metal oxide particles and / or carbonate particles containing a metal element selected from Mg, Al, Zn, Ca, Sr, and Ti. Preferably, it is a metal oxide selected from MgO, Al ₂ O ₃ , ZnO, TiO ₂ , SrTiO ₃ , CaTiO ₃ , and MgTiO ₃ . Alternatively, it is an inorganic carbonate selected from CaCO ₃ , MgCO ₃ , and SrCO ₃ . As a result of intensive studies, it has been found that the metal oxide particles and / or carbonate particles containing the metal element can be preferably used from the viewpoint of moisture adsorption and adjusting the resistance of the magnetic carrier. When the metal oxide particles and carbonate particles are not used, the charging stability is lowered and the image density stability may be affected.

  By blending and using the inorganic particles, the coating resin A, and the coating resin B, the coating strength and toughness of the resin coating layer are improved, and the image density is stabilized over a long period of time. The surface layer of the inorganic particles generally has a hydroxy group, but the coating strength is improved by chemical interaction with the carboxy group or sulfonic acid group of the coating resin B. The present inventors consider that. Furthermore, the toughness of the resin coating layer may be improved by entanglement of the molecular chain of the (meth) acrylic acid ester having an alicyclic hydrocarbon group of the coating resin A is more complicated and strong. They think.

  The number average particle diameter of primary particles of the inorganic particles is preferably 50 nm or more and 2000 nm or less, and more preferably 60 nm or more and 1800 nm or less. When the thickness is less than 50 nm or exceeds 2000 nm, there is a concern that compatibility between the coating film strength and toughness may be affected, which may affect the stability of the image density.

  Moreover, it is preferable that the hydroxyl group density | concentration of the surface of the said inorganic particle is 10.0% or more, More preferably, it is 20.0% or more and 70.0% or less. The higher the hydroxy group concentration, the better the chemical interaction with the coating resin B and the coating film strength. As a result, the image density is stabilized over a longer period.

  The hydroxy group concentration indicates the ratio of hydroxy group to the particle-derived element in X-ray photoelectron spectroscopy (hereinafter referred to as XPS) measurement.

  The method for adjusting the hydroxy group concentration can be adjusted by chemically treating the surface of the inorganic particle substrate. Preferable compounds used for the surface treatment include silane coupling agents, silane compounds, titanate coupling agents, and aluminate coupling agents. By increasing the treatment amount of these compounds, the hydroxy group concentration can be reduced.

  The resin coating layer of the present invention is preferably in a state where the coating resin A, the coating resin B, and the inorganic particles are mixed. When based on the mass of the resin component of the resin coating layer, i) the coating resin A is 10 to 90 parts by mass, and ii) the coating resin B is 10 to 90 parts by mass. When the content of the coating resin A or the coating resin B is less than 10 parts by mass, not only the coating strength and toughness of the resin coating layer, but also the smoothness of the resin coating layer surface and the magnetic carrier core Adhesion cannot be obtained sufficiently. Preferably, the coating resin A is 30 to 70 parts by mass, and ii) the coating resin B is 30 to 70 parts by mass.

  The content of the inorganic particles is 1.0 part by mass or more and 50.0 parts by mass or less, preferably 5.0 parts by mass when the total resin component contained in the resin coating layer is 100 parts by mass. Part to 40.0 parts by mass. When the amount is less than 1.0 part by mass or exceeds 50.0 parts by mass, the coating film strength and the toughness cannot be compatible, and the image density stability during long-term use decreases.

  In the present invention, the coating resin A, the coating resin B, and the inorganic particles are mixed when the magnetic carrier core surface is coated (for example, when a resin solution for coating is prepared). This is preferable. Particularly preferred is mixing immediately before coating. This makes it possible to reduce agglomeration due to chemical interaction between the resin for coating and inorganic particles, and to continue outputting high-quality images even under long-term use conditions during environmental changes. Is possible. Probably due to the chemical interaction between the electron donating properties of the alicyclic hydrocarbon groups of the coating resin A and the hydroxy groups of the inorganic particles and the electron withdrawing properties of the carboxy groups and sulfonic acid groups of the coating resin B, It is inferred that the coating strength is improved.

  The acid value of all resin components in the resin coating layer is preferably 1.0 mgKOH / g or more and 20.0 mgKOH / g or less. More preferably, it is 2.0 mgKOH / g or more and 15.0 mgKOH / g or less. When the acid value is in the above range, it becomes easy to simultaneously improve the adhesion to the magnetic carrier core, the coating film strength, and the charge imparting ability.

  When the acid value is less than 1.0 mgKOH / g, it is difficult to obtain the effect of adhesion to the magnetic carrier core. In addition, the charging ability becomes unstable, and the environmental difference increases. If it exceeds 10.0 mgKOH / g, the resin coating layer tends to absorb moisture, and the charging ability becomes unstable and the image density and the like become unstable during long-term use, particularly in a high-temperature and high-humidity environment. The acid value of the resin component of the resin coating layer can be controlled by adjusting the mixing ratio of the resins A and B.

Furthermore, the minimum value of the storage elastic modulus (G ′) of 70 ° C. or more and 100 ° C. or less of the resin coating layer is 9.0 × 10 ⁷ Pa or more and 1.0 × 10 ¹⁰ Pa or less, and the minimum loss elastic modulus (G ″). The value is preferably 9.0 × 10 ⁶ Pa or more and 1.0 × 10 ⁹ Pa or less from the viewpoint of the stability of the coating film surface, more preferably the minimum value of the storage elastic modulus (G ′) is 1. 0.0 × 10 ⁸ Pa or more and 8.0 × 10 ⁹ Pa or less, and the minimum value of the loss elastic modulus (G ″) is 2.0 × 10 ⁷ Pa or more and 8.4 × 10 ⁸ Pa or less.

When the minimum value of the storage elastic modulus (G ′) of 70 ° C. or more and 100 ° C. or less is less than 9.0 × 10 ⁷ Pa, or the minimum value of the loss elastic modulus (G ″) is less than 9.0 × 10 ⁶ Pa. The coating surface tends to soften, and the chargeability tends to decrease due to toner-derived deposits.The minimum value of the storage elastic modulus (G ′) at 70 ° C. to 100 ° C. is 1.0 × 10 ^10. When the minimum value of Pa or loss elastic modulus (G ″) exceeds 1.0 × 10 ⁹ Pa, it tends to be difficult to cover the magnetic carrier core in the coating step. As a result, the smoothness of the coating surface tends to decrease, and the output image may be affected.

  When the glass transition temperatures (Tg) of the resin A and the resin B are increased, the storage elastic modulus (G ′) tends to increase. Tg can be controlled by the type of monomer and the molecular weight of the resin. The minimum value of the storage elastic modulus (G ′) of 70 ° C. or more and 100 ° C. or less can be controlled by the Tg control of the resins A and B and the mixing ratio. In addition, the loss elastic modulus (G ″) tends to increase when the polarity, molecular weight, and Tg of the acid value of the resin is large. For this reason, the minimum value of the loss elastic modulus (G ″) is the property of these resins. It can be controlled by adjusting. Further, by mixing the resins A and B, the storage elastic modulus (G ′) and the loss elastic modulus (G ″) may be increased due to the interaction such as hydrogen bonding between the molecules. Therefore, it is necessary to control the storage elastic modulus (G ′) and the loss elastic modulus (G ″).

  In the coating resin A and the coating resin B, monomers that can be preferably used in addition to the specific monomer are, for example, methyl acrylate, ethyl acrylate, propyl acrylate, isopropyl acrylate, normal butyl acrylate, and acrylic acid. Isobutyl, tert-butyl acrylate, 2-ethylhexyl acrylate, lauryl acrylate, dodecyl acrylate, tridecyl acrylate, tetradecyl acrylate, pentadecyl acrylate, hexadecyl acrylate, heptadecyl acrylate, octadecyl acrylate, methyl methacrylate, Ethyl methacrylate, propyl methacrylate, isopropyl methacrylate, normal butyl methacrylate, isobutyl methacrylate, tert-butyl methacrylate, 2-ethyl methacrylate Hexyl, lauryl methacrylate, dodecyl methacrylate, tridecyl methacrylate, tetradecyl methacrylate, pentadecyl methacrylate, hexadecyl methacrylate acid and methacrylic acid heptadecyl and octadecyl methacrylate.

  The magnetic carrier core particles before treatment used in the present invention will be described.

  As the magnetic carrier core used in the magnetic carrier of the present invention, it is preferable to use magnetic material-dispersed resin particles in which a magnetic material is dispersed in a resin component, or porous magnetic core particles containing a resin in the pores. . Since these can reduce the true density of the magnetic carrier, the load on the toner can be reduced. Thus, even when used for a long period of time, the image quality is hardly deteriorated, and the replacement frequency of the developer composed of the toner and the carrier can be reduced. However, the effect of the present invention can be sufficiently exerted even when a commercially available magnetic carrier core is used instead of using magnetic material dispersed resin particles or porous magnetic core particles.

  The magnetic substance component used in the magnetic substance-dispersed resin particles is selected from magnetite particle powder, maghemite particle powder, or silicon oxide, silicon hydroxide, aluminum oxide and aluminum hydroxide. 1 type selected from magnetic iron oxide particle powder, barium, strontium or magnetoplumbite type ferrite particle powder containing barium-strontium, manganese, nickel, zinc, lithium and magnesium Various magnetic iron compound particle powders such as spinel type ferrite particle powders containing two or more types can be used. Among these, magnetic iron oxide particle powder can be preferably used.

  In addition to the above magnetic substance components, non-magnetic iron oxide particles such as hematite particles, non-magnetic hydrous ferric particles such as goethite particles, titanium oxide particles, silica particles, talc particles Specific magnetic inorganic compound particle powder such as powder, alumina particle powder, barium sulfate particle powder, barium carbonate particle powder, cadmium yellow particle powder, calcium carbonate particle powder and zinc white particle powder are used in combination with magnetic iron compound particle powder it can.

  When the magnetic iron compound particle powder and the non-magnetic inorganic compound particle powder are mixed and used, the mixing ratio thereof preferably includes at least 30% by mass of the magnetic iron compound particle powder.

  In the present invention, the magnetic iron compound particle powder is preferably all or partly treated with a lipophilic agent.

  The lipophilic agent used in that case is one or more selected from epoxy group, amino group, mercapto group, organic acid group, ester group, ketone group, halogenated alkyl group and aldehyde group. An organic compound having a functional group or a mixture thereof can be used.

  The organic compound having a functional group is preferably a coupling agent, more preferably a silane coupling agent, a titanium coupling agent and an aluminum coupling agent, and a silane coupling agent is particularly preferred.

  As the binder resin constituting the magnetic material-dispersed resin particles, a thermosetting resin is preferable.

  For example, there are a phenol resin, an epoxy resin, an unsaturated polyester resin, etc., but it is preferable that the phenol resin is contained because it is inexpensive and easy to manufacture. An example is phenol-formaldehyde resin.

  The content ratio of the binder resin and the magnetic iron compound particle powder constituting the composite particle in the present invention is preferably 1 to 20% by mass of the binder resin and 80 to 99% by mass of the magnetic iron compound particle powder.

  Next, a method for producing the magnetic material dispersed resin particles according to the present invention will be described.

  For example, as described in Examples below, the composite particles are stirred in an aqueous medium with phenols and aldehydes in the presence of magnetic and nonmagnetic inorganic compound particle powders and a basic catalyst. . Thereafter, there is a method in which phenols and aldehydes are reacted and cured to produce composite particles containing inorganic compound particles such as magnetic iron oxide particle powder and a phenol resin.

  It can also be produced by a so-called kneading and pulverizing method in which a binder resin containing inorganic compound particles such as magnetic iron oxide particles is pulverized. The former method is preferred in order to easily control the particle size of the magnetic carrier and achieve a sharp particle size distribution.

  The porous magnetic core particles used in the present invention will be described.

  As a material of the porous magnetic core particle, magnetite or ferrite is preferable. Furthermore, the material of the porous magnetic core particles is more preferably ferrite, since the porous structure of the porous magnetic core particles can be controlled and the resistance can be adjusted.

Ferrite is a sintered body represented by the following general formula.
(M1 ₂ O) _x (M2O) _y (Fe ₂ O ₃ ) _z
(In the formula, M1 is a monovalent metal, M2 is a divalent metal, and when x + y + z = 1.0, x and y are 0 ≦ (x, y) ≦ 0.8, respectively, and z is 0.2 <z <1.0)

  In the formula, it is preferable to use one or more metal atoms selected from the group consisting of Li, Fe, Mn, Mg, Sr, Cu, Zn, and Ca as M1 and M2. In addition, Ni, Co, Ba, Y, V, Bi, In, Ta, Zr, B, Mo, Na, Sn, Ti, Cr, Al, Si, rare earth, and the like can be used.

  The magnetic carrier is required to maintain a moderate amount of magnetization, to make the pore diameter within a desired range, and to make the uneven state on the surface of the porous magnetic core particle suitable. Moreover, it is required that the rate of the ferritization reaction can be easily controlled and the specific resistance and magnetic force of the porous magnetic core can be suitably controlled. From the above viewpoint, Mn-based ferrite, Mn-Mg-based ferrite, Mn-Mg-Sr-based ferrite and Li-Mn-based ferrite containing Mn element are more preferable.

  Below, the manufacturing process in the case of using a ferrite particle as a porous magnetic carrier particle is demonstrated in detail.

<Process 1 (weighing / mixing process)>
The ferrite raw materials are weighed and mixed.

  Examples of the ferrite raw material include metal particles of the above metal elements, or oxides, hydroxides, oxalates and carbonates thereof. Examples of the mixing apparatus include the following. Ball mill, planetary mill, Giotto mill, vibration mill. A ball mill is particularly preferable from the viewpoint of mixing properties. Specifically, a weighed ferrite raw material and balls are placed in a ball mill, and pulverized and mixed for 0.1 to 20.0 hours.

<Step 2 (temporary firing step)>
The ferrite raw material thus pulverized and mixed is preliminarily calcined in the range of 700 ° C. or more and 1200 ° C. or less in the air or in a nitrogen atmosphere for 0.5 hours or more and 5.0 hours or less to form ferrite. For firing, for example, the following furnace is used. Examples include a burner type incinerator, a rotary type baking furnace, and an electric furnace.

<Step 3 (grinding step)>
The calcined ferrite produced in step 2 is pulverized with a pulverizer.

  The pulverizer is not particularly limited as long as a desired particle size can be obtained. Examples include the following. Examples include crushers, hammer mills, ball mills, bead mills, planetary mills, and Giotto mills.

  In order to make the ferrite pulverized product have a desired particle size, for example, it is preferable to control the material, particle size, and operation time of the balls and beads used in the ball mill and bead mill. Specifically, in order to reduce the particle size of the calcined ferrite slurry, a ball having a high specific gravity may be used or the pulverization time may be increased. Further, in order to widen the particle size distribution of the calcined ferrite, it can be obtained by using balls and beads having a high specific gravity and shortening the grinding time. In addition, by mixing a plurality of calcined ferrites having different particle diameters, a calcined ferrite having a wide distribution can be obtained.

  In addition, ball mills and bead mills have a high grinding efficiency when a wet method is used rather than a dry method, and a pulverized product does not rise in the mill. For this reason, the wet type is more preferable than the dry type.

<Process 4 (granulation process)>
Water, a binder and, if necessary, a pore adjuster are added to the pulverized product of calcined ferrite. Examples of the pore adjuster include a foaming agent and resin fine particles. Examples of the foaming agent include sodium hydrogen carbonate, potassium hydrogen carbonate, lithium hydrogen carbonate, ammonium hydrogen carbonate, sodium carbonate, potassium carbonate, lithium carbonate, and ammonium carbonate. Examples of resin fine particles include polyester, polystyrene, styrene-vinyltoluene copolymer, styrene-vinylnaphthalene copolymer, styrene-acrylic acid ester copolymer, styrene-methacrylic acid ester copolymer, and styrene-α-chloromethacrylic acid. Styrene copolymer such as acid methyl copolymer, styrene-acrylonitrile copolymer, styrene-vinyl methyl ketone copolymer, styrene-butadiene copolymer, styrene-isoprene copolymer, styrene-acrylonitrile-indene copolymer Polyvinyl chloride, phenolic resin, modified phenolic resin, maleic resin, acrylic resin, methacrylic resin, polyvinyl acetate, silicone resin; aliphatic polyhydric alcohol, aliphatic dicarboxylic acid, aromatic dicarboxylic acid, aromatic dialcohol And Polyester resin having a monomer selected from diphenols as a structural unit; polyurethane resin, polyamide resin, polyvinyl butyral, terpene resin, coumarone indene resin, petroleum resin, hybrid having polyester unit and vinyl polymer unit Examples include resin fine particles.

  For example, polyvinyl alcohol is used as the binder.

  In Step 3, when wet pulverization is performed, it is preferable to add a binder and, if necessary, a pore adjuster in consideration of water contained in the ferrite slurry.

  The obtained ferrite slurry is dried and granulated using a spray dryer in a heated atmosphere of 100 ° C. or higher and 200 ° C. or lower. The spray dryer is not particularly limited as long as a desired porous magnetic core particle size can be obtained. For example, a spray dryer can be used.

<Step 5 (main firing step)>
Next, the granulated product is fired at 800 ° C. to 1400 ° C. for 1 hour to 24 hours. By raising the firing temperature and lengthening the firing time, the firing of the porous magnetic core particles proceeds, and as a result, the pore diameter is small and the number of pores is also reduced.

<Process 6 (sorting process)>
After pulverizing the particles fired as described above, coarse particles and fine particles may be removed by classification or sieving as necessary.

  The volume distribution reference 50% particle diameter (D50) of the magnetic core particles is more preferably 18.0 μm or more and 68.0 μm or less in order to prevent carrier adhesion to the image and suppression of roughness.

<Step 7 (filling step)>
The magnetic carrier of the present invention is preferably a magnetic carrier in which at least a part of the pores of the porous magnetic core particle is filled with a resin.

  The porous magnetic core particle may have a low physical strength depending on the internal pore volume. In order to increase the physical strength as a magnetic carrier, a resin is provided in at least a part of the pores of the porous magnetic core particle. It is preferable to perform filling. The amount of the resin filled in the porous magnetic core particles is preferably 2% by mass or more and 15% by mass or less with respect to the porous magnetic core particles. If there is little variation in the resin content for each magnetic carrier, the resin is filled only in the voids near the surface of the porous magnetic core particles and the voids remain inside even if the resin is filled only in a part of the inner voids. Or the internal voids may be completely filled with resin.

  The method of filling the pores of the porous magnetic core particles with the resin is not particularly limited, but the porous magnetic core particles are applied to the resin solution by a coating method such as dipping, spraying, brushing, and fluidized bed. And a method of volatilizing the solvent thereafter. As a method for filling the voids in the porous magnetic core particles with the resin, a method in which the resin is diluted with a solvent and added to the voids in the porous magnetic core particles can be employed. The solvent used here should just be what can melt | dissolve resin. When the resin is soluble in an organic solvent, examples of the organic solvent include toluene, xylene, cellosolve butyl acetate, methyl ethyl ketone, methyl isobutyl ketone, and methanol. In the case of a water-soluble resin or an emulsion type resin, water may be used as a solvent.

  The amount of the resin solid content in the resin solution is preferably 1% by mass or more and 50% by mass or less, and more preferably 1% by mass or more and 30% by mass or less. When a resin solution having a resin amount larger than 50% by mass is used, the resin solution is difficult to uniformly penetrate into the voids of the porous magnetic core particles because of its high viscosity. In addition, if the amount is less than 1% by mass, the amount of the resin is small, and the adhesive force of the resin to the porous magnetic core particles may be low.

  Either a thermoplastic resin or a thermosetting resin may be used as the resin filling the voids of the porous magnetic core particles. It is preferable that the resin has a high affinity for the porous magnetic core particles. When a resin having a high affinity is used, the surface of the porous magnetic core particles is simultaneously filled with the resin in the voids of the porous magnetic core particles. Can also be covered with resin.

  As the resin to be filled, examples of the thermoplastic resin include the following. Examples thereof include novolak resin, saturated alkyl polyester resin, polyarylate, polyamide resin, and acrylic resin.

  Moreover, the following are mentioned as said thermosetting resin. Examples include phenolic resins, epoxy resins, unsaturated polyester resins, and silicone resins.

  The magnetic carrier of the present invention is coated with a resin to form a resin coating layer. The method of coating the surface of the magnetic carrier core particle of the present invention with a resin is not particularly limited, and examples thereof include a coating method such as a dipping method, a spray method, a brush coating method, a dry method, and a fluidized bed. It is done. Among these, a dipping method capable of appropriately exposing the magnetic core particles to the surface is more preferable. The amount of the resin to be coated is preferably 0.1 parts by mass or more and 5.0 parts by mass or less with respect to 100 parts by mass of the magnetic core particles because the metal oxide portion can be appropriately exposed on the surface. .

  Next, a preferable toner configuration for achieving the object in the present invention will be described in detail below.

  Examples of the binder resin used for the toner include vinyl resins, polyester resins, and epoxy resins. Of these, vinyl resins and polyester resins are more preferable in terms of chargeability and fixability. Polyester resins are particularly preferable.

  In the present invention, a vinyl monomer monopolymer or copolymer, polyester, polyurethane, epoxy resin, polyvinyl butyral, rosin, modified rosin, terpene resin, phenol resin, aliphatic or alicyclic hydrocarbon resin, aromatic Petroleum resin or the like can be used by mixing with the above-described binder resin as necessary.

  When two or more kinds of resins are mixed and used as a binder resin, it is preferable to mix those having different molecular weights at an appropriate ratio.

  The glass transition temperature of the binder resin is preferably 45 to 80 ° C., more preferably 55 to 70 ° C., the number average molecular weight (Mn) is 2,500 to 50,000, and the weight average molecular weight (Mw) is 10, It is preferable that it is 000-1,000,000.

  As the binder resin, the following polyester resins are also preferable.

  In the polyester resin, 45 to 55 mol% of all components is preferably an alcohol component, and 55 to 45 mol% is preferably an acid component.

  The acid value of the polyester resin is preferably 90 mgKOH / g or less, more preferably 50 mgKOH / g or less, and the OH value is preferably 50 mgKOH / g or less, more preferably 30 mgKOH / g or less. This is because as the number of terminal groups of the molecular chain increases, the dependency of the toner on the environment increases in the environment.

  The glass transition temperature of the polyester resin is preferably 50 to 75 ° C, more preferably 55 to 65 ° C. The number average molecular weight (Mn) is preferably 1,500 to 50,000, more preferably 2,000 to 20,000. The weight average molecular weight (Mw) is preferably 6,000 to 100,000, more preferably 10,000 to 90,000.

  In the present invention, when the toner is used as a magnetic toner, the magnetic material contained in the magnetic toner includes iron oxides such as magnetite, maghemite and ferrite, and iron oxides including other metal oxides; Fe, Co, Ni Or metals such as Al, Co, Cu, Pb, Mg, Ni, Sn, Zn, Sb, Be, Bi, Cd, Ca, Mn, Se, Ti, W, V Examples thereof include alloys and mixtures thereof.

Specifically, examples of magnetic materials include triiron tetroxide (Fe ₃ O ₄ ), iron sesquioxide (γ-Fe ₂ O ₃ ), iron oxide zinc (ZnFe ₂ O ₄ ), and iron yttrium oxide (Y ₃ Fe). ₅ O ₁₂ ), iron cadmium oxide (CdFe ₂ O ₄ ), iron gadolinium oxide (Gd ₃ Fe ₅ O ₁₂ ), copper iron oxide (CuFe ₂ O ₄ ), lead iron oxide (PbFe ₁₂ O ₁₉ ), nickel iron oxide (NiFe ₂ O ₄ ), neodymium iron oxide (NdFe ₂ O ₃ ), barium iron oxide (BaFe ₁₂ O ₁₉ ), magnesium iron oxide (MgFe ₂ O ₄ ), manganese iron oxide (MnFe ₂ O ₄ ), iron lanthanum oxide (LaFeO ₃ ), iron powder (Fe), cobalt powder (Co), nickel powder (Ni) and the like.

  These magnetic materials are preferably 20 parts by weight or more and 150 parts by weight or less, more preferably 50 parts by weight or more and 130 parts by weight or less, still more preferably 60 parts by weight or more and 120 parts by weight or less with respect to 100 parts by weight of the binder resin. use.

  The following are mentioned as a nonmagnetic coloring agent used by this invention.

  Examples of the black colorant include carbon black; those adjusted to black using a yellow colorant, a magenta colorant, and a cyan colorant.

  Examples of the color pigment for magenta toner include the following. Examples include condensed azo compounds, diketopyrrolopyrrole compounds, anthraquinones, quinacridone compounds, basic dye lake compounds, naphthol compounds, benzimidazolone compounds, thioindigo compounds, and perylene compounds. Specifically, C.I. I. Pigment Red 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 21, 22, 23, 30, 31, 32, 37, 38, 39, 40, 41, 48: 2, 48: 3, 48: 4, 49, 50, 51, 52, 53, 54, 55, 57: 1, 58, 60, 63, 64, 68, 81: 1, 83, 87, 88, 89, 90, 112, 114, 122, 123, 144, 146, 150, 163, 166, 169, 177, 184, 185, 202, 206, 207, 209, 220, 221, 238, 254, 269; I. Pigment violet 19, C.I. I. Bat red 1, 2, 10, 13, 15, 23, 29, 35 are mentioned.

  The colorant may be used alone as a pigment, but it is preferable from the viewpoint of the image quality of a full-color image to improve the sharpness by using a dye and a pigment together.

  Examples of the magenta toner dye include the following. C. I solvent red 1, 3, 8, 23, 24, 25, 27, 30, 49, 81, 82, 83, 84, 100, 109, 121, C.I. I. Disper thread 9, C.I. I. Solvent Violet 8, 13, 14, 21, 27, C.I. I. Oil-soluble dyes such as Disper Violet 1, C.I. I. Basic Red 1, 2, 9, 12, 13, 14, 15, 17, 18, 22, 23, 24, 27, 29, 32, 34, 35, 36, 37, 38, 39, 40, C.I. I. Basic dyes such as basic violet 1, 3, 7, 10, 14, 15, 21, 25, 26, 27, 28.

  Examples of the color pigment for cyan toner include the following. C. I. Pigment Blue 1, 2, 3, 7, 15: 2, 15: 3, 15: 4, 16, 17, 60, 62, 66; I. Bat Blue 6, C.I. I. Acid Blue 45, a copper phthalocyanine pigment in which 1 to 5 phthalimidomethyls are substituted on the phthalocyanine skeleton.

  Examples of the color pigment for yellow include the following. Condensed azo compounds, isoindolinone compounds, anthraquinone compounds, azo metal compounds, methine compounds, allylamide compounds. Specifically, C.I. I. Pigment Yellow 1, 2, 3, 4, 5, 6, 7, 10, 11, 12, 13, 14, 15, 16, 17, 23, 62, 65, 73, 74, 83, 93, 95, 97, 109, 110, 111, 120, 127, 128, 129, 147, 155, 168, 174, 180, 181, 185, 191; I. Bat yellow 1, 3, and 20 are mentioned. In addition, C.I. I. Direct Green 6, C.I. I. Basic Green 4, C.I. I. Dyes such as Basic Green 6 and Solvent Yellow 162 can also be used.

  The amount of the colorant used is preferably 0.1 parts by mass or more and 30 parts by mass or less, more preferably 0.5 parts by mass or more and 20 parts by mass or less, and further preferably 100 parts by mass of the binder resin. Is 3 parts by mass or more and 15 parts by mass or less.

  Further, in the toner, it is preferable to use a toner obtained by mixing a colorant with a binder resin in advance to form a master batch. Then, the colorant can be favorably dispersed in the toner by melt-kneading this colorant masterbatch and other raw materials (binder resin, wax, etc.).

  In the toner, a charge control agent can be used as necessary in order to further stabilize the chargeability. The charge control agent is preferably used in an amount of 0.5 to 10 parts by mass per 100 parts by mass of the binder resin. When the amount is less than 0.5 parts by mass, sufficient charging characteristics tend not to be obtained. When the amount exceeds 10 parts by mass, the compatibility with other materials is deteriorated or excessive charging is caused under low humidity. There is a tendency to become.

  Examples of the charge control agent include the following.

  As a negative charge control agent for controlling the toner to be negative charge, for example, an organometallic complex or a chelate compound is effective. Examples include monoazo metal complexes, aromatic hydroxycarboxylic acid metal complexes, and aromatic dicarboxylic acid metal complexes. Other examples include aromatic hydroxycarboxylic acids, aromatic mono and polycarboxylic acids and metal salts thereof, anhydrides or esters thereof, or phenol derivatives of bisphenol.

  Examples of positive charge control agents for controlling the toner to be positively charged include modified products such as nigrosine and fatty acid metal salts, tributylbenzylammonium-1-hydroxy-4-naphthosulfonate, tetrabutylammonium tetrafluoroborate and the like. As onium salts such as quaternary ammonium salts and their analogs such as phosphonium salts and their chelating pigments, triphenylmethane dyes and their lake pigments (as rake agents, phosphotungstic acid, phosphomolybdic acid, phosphotungsten) Molybdic acid, tannic acid, lauric acid, gallic acid, ferricyanic acid, ferrocyanic compound, etc.), metal salts of higher fatty acids, diorganotin oxides such as dibutyltin oxide, dioctyltin oxide, dicyclohexyltin oxide and di Chirusuzuboreto, dioctyl tin borate include diorgano tin borate such as dicyclohexyl tin borate.

  If necessary, one or two or more release agents may be contained in the toner particles. Examples of the release agent include the following.

  Aliphatic hydrocarbon waxes such as low molecular weight polyethylene, low molecular weight polypropylene, microcrystalline wax, and paraffin wax can be preferably used. In addition, oxides of aliphatic hydrocarbon waxes such as oxidized polyethylene wax, or block copolymers thereof; waxes mainly composed of fatty acid esters such as carnauba wax, sazol wax, and montanic ester wax; and Examples include those obtained by partially or entirely deoxidizing fatty acid esters such as deoxidized carnauba wax.

  The amount of the release agent is preferably 0.1 parts by mass or more and 20 parts by mass or less, more preferably 0.5 parts by mass or more and 10 parts by mass or less per 100 parts by mass of the binder resin.

  Moreover, it is preferable that melting | fusing point prescribed | regulated by the maximum endothermic peak temperature at the time of the temperature rising measured with the differential scanning calorimeter (DSC) of the said mold release agent is 65-130 degreeC. More preferably, it is 80-125 degreeC. When the melting point is less than 65 ° C., the viscosity of the toner tends to decrease and toner adhesion to the photoreceptor tends to occur, and when the melting point exceeds 130 ° C., the low-temperature fixability tends to deteriorate.

  As the fluidity improver, a fine powder may be used as the fluidity improver by externally adding to the toner particles so that the fluidity can be increased compared to before and after the addition. For example, fluorine resin powder such as vinylidene fluoride fine powder and polytetrafluoroethylene fine powder; fine powder silica such as wet process silica and dry process silica, fine powder titanium oxide, fine powder alumina and the like are silane coupling agents. It is particularly preferable that the surface treatment is performed with a titanium coupling agent or silicone oil, and the surface is hydrophobized, and the hydrophobization degree measured by a methanol titration test is in a range of 30 to 80. .

  The fluidity improver is preferably used in an amount of 0.1 to 10 parts by mass, more preferably 0.2 to 8 parts by mass with respect to 100 parts by mass of the toner particles.

  When the toner is mixed with the magnetic carrier of the present invention and used as a two-component developer, the carrier mixing ratio at that time is preferably 2% by mass or more and 15% by mass or less, more preferably as the toner concentration in the developer. Is 4 mass% or more and 13 mass% or less. This gives good results. If the toner concentration is less than 2% by mass, the image density tends to decrease, and if it exceeds 15% by mass, fog and in-machine scattering tend to occur.

  Further, in the replenishment developer for replenishing the developing device in accordance with the decrease in the toner concentration of the two-component developer in the developing unit, the amount of toner is preferably 2 parts by mass with respect to 1 part by mass of the magnetic carrier for replenishment. The amount is 50 parts by mass or less.

  Next, an image forming apparatus including a developing device using a magnetic carrier, a two-component developer, and a replenishing developer will be described by way of example. However, the image forming apparatus using the magnetic carrier of the present invention is limited to this. It is not a thing.

<Image forming method>
In FIG. 1, the electrostatic latent image carrier 1 rotates in the direction of the arrow in the figure. The electrostatic latent image carrier 1 is charged by a charger 2 that is a charging unit, and the surface of the charged electrostatic latent image carrier 1 is exposed by an exposure unit 3 that is an electrostatic latent image forming unit. Form an image. The developing device 4 has a developing container 5 for storing a two-component developer, the developer carrying member 6 is disposed in a rotatable state, and a magnetic field generating means is provided inside the developer carrying member 6 to provide a magnet. 7 is included. At least one of the magnets 7 is installed so as to face the latent image carrier.

  The two-component developer is held on the developer carrier 6 by the magnetic field of the magnet 7, the amount of the two-component developer is regulated by the regulating member 8, and the developer component is opposed to the electrostatic latent image carrier 1. Be transported. In the developing unit, a magnetic brush is formed by a magnetic field generated by the magnet 7. Thereafter, the electrostatic latent image is visualized as a toner image by applying a developing bias in which an alternating electric field is superimposed on a DC electric field. The toner image formed on the electrostatic latent image carrier 1 is electrostatically transferred to the recording medium 12 by the transfer charger 11.

  Here, as shown in FIG. 2, the image may be temporarily transferred from the electrostatic latent image carrier 1 to the intermediate transfer member 9 and then electrostatically transferred to a transfer material (recording medium) 12. Thereafter, the recording medium 12 is conveyed to a fixing device 13 where the toner is fixed on the recording medium 12 by being heated and pressurized. Thereafter, the recording medium 12 is discharged out of the apparatus as an output image. Note that the toner remaining on the electrostatic latent image carrier 1 after the transfer process is removed by the cleaner 15. Thereafter, the electrostatic latent image carrier 1 cleaned by the cleaner 15 is electrically initialized by the light irradiation from the pre-exposure 16, and the image forming operation is repeated.

  FIG. 2 shows an example of a full-color image forming apparatus to which the magnetic carrier of the present invention can be applied.

  The arrows indicating the arrangement and rotation direction of image forming units such as K, Y, C, and M in the figure are not limited to these. Incidentally, K means black, Y means yellow, C means cyan, and M means magenta. In FIG. 2, the electrostatic latent image carriers 1K, 1Y, 1C, 1M rotate in the direction of the arrow in the figure. Each electrostatic latent image carrier is charged by charging units 2K, 2Y, 2C, and 2M that are charging means, and an exposure unit 3K that is an electrostatic latent image forming unit is provided on the surface of each charged electrostatic latent image carrier. Exposure is performed with 3Y, 3C, and 3M to form an electrostatic latent image.

  Thereafter, the electrostatic latent image can be converted into a toner image by the two-component developer carried on the developer carrying members 6K, 6Y, 6C, and 6M provided in the developing devices 4K, 4Y, 4C, and 4M as developing means. Visualized. Further, the image is transferred to the intermediate transfer body 9 by the intermediate transfer chargers 10K, 10Y, 10C, and 10M which are transfer means. Further, the image is transferred to a recording medium 12 by a transfer charger 11 serving as a transfer unit, and the recording medium 12 is heated and pressure-fixed by a fixing unit 13 serving as a fixing unit and output as an image. Then, the intermediate transfer body cleaner 14 which is a cleaning member for the intermediate transfer body 9 collects transfer residual toner and the like.

  As a developing method, specifically, it is preferable to perform development in a state where the magnetic brush is in contact with the photosensitive member while applying an alternating voltage to the developer carrying member to form an alternating electric field in the developing region. . The distance (S-D distance) between the developer carrying member (developing sleeve) 6 and the photosensitive drum is preferably 100 μm or more and 1000 μm or less in terms of preventing carrier adhesion and improving dot reproducibility. If it is smaller than 100 μm, the supply of the developer tends to be insufficient, and the image density tends to be low. If it exceeds 1000 μm, the magnetic lines of force from the magnetic pole S1 spread and the density of the magnetic brush is lowered, so that the dot reproducibility is inferior, or the force that restrains the magnetic coat carrier is weakened and carrier adhesion tends to occur.

  The voltage (Vpp) between peaks of the alternating electric field is 300 V or more and 3000 V or less, preferably 500 V or more and 1800 V or less. The frequency is 500 Hz to 10000 Hz, preferably 1000 to 7000 Hz, and can be appropriately selected depending on the process. In this case, the waveform of the AC bias for forming the alternating electric field includes a triangular wave, a rectangular wave, a sine wave, or a waveform with a changed duty ratio. In order to cope with the change in the formation speed of the toner image sometimes, it is preferable to perform development by applying a developing bias voltage (intermittent alternating voltage) having a discontinuous AC bias voltage to the developer carrier. . When the applied voltage is lower than 300 V, it is difficult to obtain a sufficient image density, and the fog toner in the non-image area tends not to be collected well. When the voltage exceeds 3000 V, the latent image is disturbed via the magnetic brush, and the image quality tends to deteriorate.

  By using a two-component developer with well-charged toner, the anti-fogging voltage (Vback) can be lowered and the primary charge of the photoreceptor can be lowered, thus extending the life of the photoreceptor. it can. Vback is 200 V or less, more preferably 150 V or less, although it depends on the development system. The contrast potential is preferably 100 V or more and 400 V or less so that a sufficient image density is obtained.

  When the frequency is lower than 500 Hz, although related to the process speed, the configuration of the photoconductor may be the same as that of a photoconductor used in an image forming apparatus. For example, a photoreceptor having a structure in which a conductive layer, an undercoat layer, a charge generation layer, a charge transport layer, and a charge injection layer as necessary are provided on a conductive substrate such as aluminum or SUS in this order.

  The conductive layer, undercoat layer, charge generation layer, and charge transport layer may be those usually used for a photoreceptor. As the outermost surface layer of the photoreceptor, for example, a charge injection layer or a protective layer may be used.

<Method for measuring acid value>
The acid value is the number of mg of potassium hydroxide necessary for neutralizing the acid contained in 1 g of the sample. That is, the number of mg of potassium hydroxide required to neutralize free fatty acids and resin acids contained in 1 g of a sample is referred to as an acid value.

  In the present invention, the acid value is measured according to JIS K 0070-1992. Specifically, the measurement is performed according to the following procedure.

(1) Preparation of Reagent 1.0 g of phenolphthalein is dissolved in 90 mL of ethyl alcohol (95 vol%), and ion exchanged water is added to make 100 mL to obtain a phenolphthalein solution.

  7 g of special grade potassium hydroxide is dissolved in 5 mL of water, and ethyl alcohol (95 vol%) is added to make 1 L. In order to avoid contact with carbon dioxide, etc., it is placed in an alkali-resistant container and allowed to stand for 3 days, followed by filtration to obtain a potassium hydroxide solution. The obtained potassium hydroxide solution is stored in an alkali-resistant container. As the factor of the potassium hydroxide solution, take 25 mL of 0.1 mol / L hydrochloric acid in an Erlenmeyer flask, add a few drops of the phenolphthalein solution, titrate with the potassium hydroxide solution, and the hydroxylation required for neutralization. Determined from the amount of potassium solution. As the 0.1 mol / L hydrochloric acid, one prepared according to JIS K 8001-1998 is used.

(2) Operation (A) Main test 2.0 g of a sample is precisely weighed into a 200 mL Erlenmeyer flask, and 100 mL of a mixed solution of toluene / ethanol (2: 1) is added and dissolved over 5 hours. Subsequently, several drops of the phenolphthalein solution is added as an indicator, and titration is performed using the potassium hydroxide solution. The end point of titration is when the light red color of the indicator lasts for about 30 seconds.
(B) Blank test Titration is performed in the same manner as above except that no sample is added (that is, only a mixed solution of toluene / ethanol (2: 1) is used).

(3) Calculation of acid value The obtained result is substituted into the following formula to calculate the acid value.
AV = [(B−A) × f × 5.61] / S

  Here, AV: acid value (mgKOH / g), A: addition amount (mL) of potassium hydroxide solution in blank test, B: addition amount (mL) of potassium hydroxide solution in this test, f: potassium hydroxide Solution factor, S: sample (g).

<Measuring method of volume average particle diameter (D50) of magnetic carrier and porous magnetic core>
The particle size distribution was measured with a laser diffraction / scattering particle size distribution measuring apparatus “Microtrack MT3300EX” (manufactured by Nikkiso Co., Ltd.).

The volume average particle diameter (D50) of the magnetic carrier and the porous magnetic core was measured by mounting a sample feeder “One Shot Dry Sample Conditioner Turbotrac” (manufactured by Nikkiso Co., Ltd.) for dry measurement. As the supply conditions of Turbotrac, a dust collector was used as the vacuum source, the air volume was about 33 L / sec, and the pressure was about 17 kPa. Control is automatically performed on software. For the particle size, a 50% particle size (D50), which is a cumulative value of volume average, is obtained. Control and analysis are performed using attached software (version 10.3.3-202D). The measurement conditions are as follows.
SetZero time: 10 seconds Measurement time: 10 seconds Number of measurements: 1 time Particle refractive index: 1.81%
Particle shape: Non-spherical measurement upper limit: 1408 μm
Measurement lower limit: 0.243 μm
Measurement environment: 23 ° C., 50% RH

<Measuring method of weight average particle diameter (D4) and number average particle diameter (D1) of toner>
The weight average particle diameter (D4) and number average particle diameter (D1) of the toner are measured with a fine particle size distribution measuring apparatus “Coulter Counter Multisizer 3” (registered trademark, Beckman And a dedicated software “Beckman Coulter Multisizer 3 Version 3.51” (manufactured by Beckman Coulter, Inc.) for setting measurement conditions and analyzing measurement data were used. Measurement was performed with 25,000 effective measurement channels, and measurement data was analyzed and calculated.

  As the electrolytic aqueous solution used for the measurement, special grade sodium chloride is dissolved in ion-exchanged water so as to have a concentration of about 1% by mass, for example, “ISOTON II” (manufactured by Beckman Coulter, Inc.) can be used.

  Prior to measurement and analysis, the dedicated software was set as follows.

  In the “Standard Measurement Method (SOM) Change Screen” of the dedicated software, set the total count in the control mode to 50000 particles, set the number of measurements once, and set the Kd value to “standard particles 10.0 μm” (Beckman Coulter, Inc.) Set the value obtained using The threshold and noise level are automatically set by pressing the threshold / noise level measurement button. Also, the current is set to 1600 μA, the gain is set to 2, the electrolyte is set to ISOTON II, and the aperture tube flash after measurement is checked.

  In the “pulse to particle size conversion setting screen” of the dedicated software, the bin interval is set to logarithmic particle size, the particle size bin is set to 256 particle size bin, and the particle size range is set to 2 μm to 60 μm.

The specific measurement method is as follows.
(1) About 200 mL of the electrolytic solution is placed in a glass 250 mL round-bottom beaker dedicated to Multisizer 3, set on a sample stand, and the stirrer rod is stirred counterclockwise at 24 rpm. Then, dirt and bubbles in the aperture tube are removed by the “aperture flush” function of the analysis software.
(2) About 30 mL of the electrolytic solution is placed in a glass 100 mL flat bottom beaker. In this, "Contaminone N" (nonionic surfactant, anionic surfactant, 10% by weight aqueous solution of neutral detergent for pH7 precision measuring instrument cleaning, made by organic builder, manufactured by Wako Pure Chemical Industries, Ltd. About 0.3 mL of a diluted solution obtained by diluting 3) with ion-exchanged water is added.
(3) Two oscillators with an oscillation frequency of 50 kHz are incorporated in a state where the phase is shifted by 180 degrees, and placed in a water tank of an ultrasonic disperser “Ultrasonic Dispersion System Tetora 150” (manufactured by Nikkiki Bios) with an electrical output of 120 W. Add a fixed amount of ion-exchanged water. About 2 mL of the contamination N is added to the water tank.
(4) The beaker of (2) is set in the beaker fixing hole of the ultrasonic disperser, and the ultrasonic disperser is operated. And the height position of a beaker is adjusted so that the resonance state of the liquid level of the electrolyte solution in a beaker may become the maximum.
(5) In a state where the electrolytic aqueous solution in the beaker of (4) is irradiated with ultrasonic waves, about 10 mg of toner is added to the electrolytic aqueous solution little by little and dispersed. Then, the ultrasonic dispersion process is continued for another 60 seconds. In ultrasonic dispersion, the temperature of the water tank is appropriately adjusted so as to be 10 ° C. or higher and 40 ° C. or lower.
(6) To the round bottom beaker of (1) installed in the sample stand, the electrolyte solution of (5) in which the toner is dispersed is dropped using a pipette, and the measurement concentration is adjusted to about 5%. . Measurement is performed until the number of measured particles reaches 50,000.
(7) The measurement data is analyzed with the dedicated software attached to the apparatus, and the weight average particle diameter (D4) and the number average particle diameter (D1) are calculated. The “average diameter” on the analysis / volume statistics (arithmetic average) screen when the graph / volume% is set with the dedicated software is the weight average particle diameter (D4). The “average diameter” on the analysis / number statistics (arithmetic average) screen when the graph / number% is set in the dedicated software is the number average particle diameter (D1).

<Measurement of minimum value of storage elastic modulus (G ′) and loss elastic modulus (G ″) of resin coating layer of 70 ° C. or higher and 100 ° C. or lower>
A rotating plate rheometer “ARES” (manufactured by TA INSTRUMENTS) is used as a measuring apparatus. As the measurement sample below, a coating resin obtained by dissolving and mixing the coating resins A and B in toluene and removing the solvent, or a coating resin eluted with toluene from a magnetic carrier is used.

  As a measurement sample, a sample press-molded into a disk shape having a diameter of 7.9 mm and a thickness of 2.0 ± 0.3 (mm) using a tablet molding machine in an environment of 25 ° C. is used. The sample was mounted on a parallel plate, heated from room temperature (25 ° C.) to 180 ° C. over 20 minutes to adjust the shape of the sample, then cooled to 25 ° C., the viscoelasticity measurement start temperature, and measured. Start. At this time, it is important to set the sample so that the initial normal force becomes zero. Further, as described below, in the subsequent measurement, the effect of normal force can be canceled by performing automatic tension adjustment (Auto Tension Adjustment ON).

The measurement is performed under the following conditions.
(1) A parallel plate having a diameter of 7.9 mm is used.
(2) Frequency 1.0 Hz
(3) The applied strain initial value (Strain) is set to 0.1%.
(4) Measure between 25 and 120 ° C at a ramp rate of 2.0 (° C / min). In the measurement, the following automatic adjustment mode setting conditions are used. Measurement is performed in an automatic strain adjustment mode (Auto Strain).
(5) The maximum applied strain (Max Applied Strain) is set to 20.0%.
(6) The maximum torque (Max Allowed Torque) is set to 200.0 (g · cm), and the minimum torque (Min Allowed Torque) is set to 0.2 (g · cm).
(7) Set the distortion adjustment (Strain Adjustment) to 20.0% of Current Strain. In the measurement, an automatic tension adjustment mode (Auto Tension) is adopted.
(8) Set automatic tension direction (Auto Tension Direction) as compression (Compression).
(9) The initial static force (Initial Static Force) is set to 100 g, and the automatic tension sensitivity (Auto Tension Sensitivity) is set to 40.0 g.
(10) The operating condition of the automatic tension (Auto Tension) is that the sample modulus is 1.0 × 10 ³ (Pa) or more.

  Read the results of storage elastic modulus (G ′) and loss elastic modulus (G ″) in the range of 70 ° C. or higher and 100 ° C. or lower, and confirm the minimum value and its temperature.

<Separation of resin coating layer from magnetic carrier and fractionation of coating resins A and B in the resin coating layer>
As a method of separating the coating layer from the magnetic carrier, the magnetic carrier is taken in a cup and the coating resin is eluted using toluene.

  The eluted resin is collected using the following apparatus.

[Device configuration]
LC-908 (manufactured by Nippon Analysis Industry Co., Ltd.)
JRS-86 (Company; repeat injector)
JAR-2 (Company; Autosampler)
FC-201 (Gilson, Hula cushion collector)
[Column structure]
JAIGEL-1H to 5H (20φ × 600 mm: preparative column) (manufactured by Nippon Analytical Industries, Ltd.)
[Measurement condition]
Temperature: 40 ° C
Solvent: THF
Flow rate: 5 ml / min.
Detector: RI

  For the fractionation method, the molecular weight distribution of the coating resin is measured by the following method, the elution time at which the peak molecular weight (Mp) of the coating resin A and the coating resin B is measured in advance, and the respective resin components are separated before and after that. To do. Thereafter, the solvent was removed and dried to obtain a coating resin A and a coating resin B. In addition, the resin structure identified the atomic group from the light absorption wave number using the Fourier-transform infrared spectroscopy analyzer (Spectrum One: made by PerkinElmer), and identified the coating resin A and the coating resin B.

<Measurement of peak molecular weight (Mp) and content ratio of coating resin A, coating resin B, and coating resin in the resin coating layer>
The peak molecular weight (Mp) of the coating resin A, the coating resin B, and the coating resin was measured using gel permeation chromatography (GPC) according to the following procedure.

  First, the measurement sample was produced as follows.

  A sample (a coating tree separated from a magnetic carrier, a coating resin A and a coating resin B separated by a preparative device) and tetrahydrofuran (THF) were mixed at a concentration of 5 mg / ml, and the mixture was stirred at room temperature for 24 hours. On standing, the sample was dissolved in THF. Then, what passed the sample processing filter (Maishori disk H-25-2 Tosoh company make, Excro disk 25CR Gelman Science Japan company make) was made into the sample of GPC.

Next, it measured on the following measurement conditions according to the operation manual of the said apparatus using the GPC measuring apparatus (HLC-8120GPC Tosoh company make).

(Measurement condition)
Equipment: High-speed GPC “HLC8120 GPC” (manufactured by Tosoh Corporation)
Column: Seven series of Shodex KF-801, 802, 803, 804, 805, 806, 807 (manufactured by Showa Denko KK)
Eluent: THF
Flow rate: 1.0 ml / min
Oven temperature: 40.0 ° C
Sample injection volume: 0.10 ml

  Moreover, in calculating the peak molecular weight (Mp) of the sample, a calibration curve was obtained using standard polystyrene resin (TSK Standard Polystyrene F-850, F-450, F-288, F-128, F-80, F-40 manufactured by Tosoh Corporation). F-20, F-10, F-4, F-2, F-1, A-5000, A-2500, A-1000, A-500) were used.

  Further, the content ratio was determined from the peak area ratio of the molecular weight distribution measurement. As shown in FIG. 3, in the case where the region 1 and the region 2 are completely separated, the resin content ratio was obtained from the area ratio of each region. As shown in FIG. 4, when each region overlaps, it is divided by a line drawn vertically from the inflection point of the GPC molecular weight distribution curve to the horizontal axis, and the content ratio is calculated from the area ratio of region 1 and region 2 shown in FIG. Asked.

<Measurement method of surface functional group concentration of particles>
-Measuring method of hydroxy group concentration 10 mg of particles are pasted on indium foil. At that time, the particles are uniformly pasted so that the indium foil portion is not exposed. 1.0 ml of trifluoroacetic anhydride is dropped into a 30 ml screw tube and the system is saturated with steam. The particles together with the indium foil are put into the system, and the particles are left in the trifluoroacetic anhydride atmosphere for 12 hours. At this time, care is taken so that the particles do not adhere directly to the trifluoroacetic anhydride. The particles were taken out from the system together with the indium foil, and left in a drier at a preset temperature of 25 ° C. for 6 hours. When XPS analysis is performed on the obtained particles, C1SXPS peak (P1) derived from trifluoroacetic anhydride and XPS peak (P2) of the particle-derived element are detected. The surface functional group concentration of was calculated. The measurement conditions are as follows.
Device: PHI5000 VERSAPROBE II (ULVAC-PHI Co., Ltd.)
Irradiation line: Al Kd line output: 25W 15kV
PassEnergy: 29.35 eV
Stepsize: 0.125 eV
XPS peak (P2): Ti _2P (TiO ₂ , MgTiO ₂ , CaTiO ₂ , SrTiO ₂ ) Zn _{2P 3/2} (ZnO)
Al _2P (Al ₂ O ₃ ), Ca _2P (CaCO ₃ , CaO),
Mg _2P (MgO, MgCO ₃ ), Sr _3D (SrCO ₃ ),
K _2P (K ₂ CO ₃ )
Particle surface functional group concentration [%] = P1 / P2 × 100 (Formula 2)

<Method for measuring number average particle diameter of primary particles of inorganic particles>
Regarding the number average particle size of the primary particles of the inorganic particles in the present invention, the number average particle size of the primary particles of the inorganic particles is observed with a scanning electron microscope, and the major axis and the minor axis of the particles are observed. The average value was taken as the particle size. Further, the particle size of 100 particles was measured, and the average value was defined as the number average particle size of the primary particles.

  EXAMPLES Hereinafter, although this invention is demonstrated more concretely with reference to an Example, this invention is not limited only to these Examples.

<Example of manufacturing magnetic carrier core 1>
Process 1 (weighing / mixing process)
Fe ₂ O ₃ 68.3 mass%
MnCO ₃ 28.5 mass%
Mg (OH) ₂ 2.0 mass%
SrCO ₃ 1.2% by mass
The ferrite raw material was weighed, and 20 parts by mass of water was added to 80 parts by mass of the ferrite raw material and pulverized to prepare a slurry. The solid content concentration of the slurry was 80% by mass.

Process 2 (temporary firing process)
The mixed slurry is dried with a spray dryer (Okawara Kako Co., Ltd.) and then calcined in a batch-type electric furnace under a nitrogen atmosphere (oxygen concentration: 1.0% by volume) at a temperature of 1050 ° C. for 3.0 hours. Ferrite was produced.

Process 3 (Crushing process)
After the calcined ferrite was pulverized to about 0.5 mm with a crusher, water was added to prepare a slurry. The solid content concentration of the slurry was 70% by mass. The slurry was pulverized for 3 hours with a wet ball mill using 1/8 inch stainless beads. Further, this slurry was pulverized by a wet bead mill using zirconia having a diameter of 1 mm for 4 hours to obtain a calcined ferrite slurry having a volume-based 50% particle diameter (D50) of 1.3 μm.

Process 4 (granulation process)
After adding 100 parts by weight of the calcined ferrite slurry at a ratio of 1.0 part by weight of ammonium polycarboxylate as a dispersing agent and 1.5 parts by weight of polyvinyl alcohol as a binder, a spray dryer (manufactured by Okawara Chemical Co., Ltd.) Granulated into spherical particles and dried. After adjusting the particle size of the obtained granulated product, it was heated at 700 ° C. for 2 hours using a rotary electric furnace to remove organic substances such as a dispersant and a binder.

Process 5 (firing process)
Under a nitrogen atmosphere (oxygen concentration: 1.0% by volume), the time from room temperature to the firing temperature (1100 ° C.) was 2 hours, and the temperature was maintained at 1100 ° C. for 4 hours for firing. Thereafter, the temperature was lowered to 60 ° C. over 8 hours, returned to the atmosphere from the nitrogen atmosphere, and taken out at a temperature of 40 ° C. or lower.

Process 6 (screening process)
After pulverizing the agglomerated particles, the coarse particles are removed by sieving with a sieve having a mesh opening of 150 μm, fine powder is removed by air classification, and the low magnetic force is removed by magnetic separation to obtain a porous magnetic core. It was. The obtained porous magnetic core particles were porous and had pores.

Process 7 (filling process)
100 parts by mass of the obtained porous magnetic core particles are placed in a stirring vessel of a mixing stirrer (universal stirrer NDMV type manufactured by Dalton), and nitrogen is introduced while maintaining the temperature at 60 ° C. and reducing the pressure to 2.3 kPa. did. There is a porous material in which 49.5 parts by mass of toluene and 0.5% by mass of γ-aminopropyltriethoxysilane are stirred for 10 minutes with a multi-blender mixer with respect to 50% by mass of SR2410 (a silicone resin manufactured by Toray Dow Corning). It was dripped on the magnetic core particles. The dropping amount was adjusted to 4.0 parts by mass as the solid content of the resin component with respect to 100 parts by mass of the porous magnetic core particles.

  Stirring is continued as it is for 2.5 hours after the completion of dropping, then the temperature is raised to 70 ° C., the solvent is removed under reduced pressure, and the resin composition obtained from the resin solution 1 is filled in the porous magnetic core particles. did.

  After cooling, the obtained resin-filled magnetic core particles are transferred into a rotatable mixing vessel and transferred to a mixer having a spiral blade (Drum mixer UD-AT type manufactured by Sugiyama Heavy Industries Co., Ltd.) and 2 ° C. under a nitrogen atmosphere. The temperature was increased to a set temperature of the stirrer of 220 ° C. at a rate of temperature increase per minute. Stirring was performed at this temperature for 1.0 hour to cure the resin, and stirring was continued for an additional 1.0 hour while maintaining 200 ° C.

  Thereafter, it was cooled to room temperature, the ferrite particles filled and cured with resin were taken out, and the nonmagnetic material was removed using a magnetic separator. Furthermore, the coarse particle was removed with the vibration sieve and the magnetic carrier core 1 with which resin was filled was obtained. The 50% particle size (D50) based on volume distribution of the magnetic carrier core 1 was 38.5 μm.

<Example of manufacturing magnetic carrier core 2>
4.0% by mass of a silane coupling agent (3- (2-aminoethylamino) propyltrimethoxysilane) is added to magnetite powder having a number average particle size of 0.30 μm, and 100 ° C. or higher in the container. The mixture was stirred at high speed to process each fine particle.
・ Phenol 10 parts by mass ・ Formaldehyde solution 6 parts by mass (formaldehyde 40%, methanol 10%, water 50%)
-Treated magnetite 84 parts by mass The above material, 5 parts by mass of 28% ammonia water, and 20 parts by mass of water are placed in a flask, and the temperature is raised and maintained at 85 ° C for 30 minutes while stirring and mixing, and polymerized for 3 hours. The resulting phenolic resin was cured. Thereafter, the cured phenol resin was cooled to 30 ° C., water was further added, the supernatant was removed, the precipitate was washed with water, and then air-dried. Subsequently, this was dried under reduced pressure (5 mmHg or less) at a temperature of 60 ° C. to obtain a spherical magnetic carrier core 2 in which a magnetic material was dispersed. The 50% particle size (D50) based on volume distribution of the magnetic carrier core 2 was 38.5 μm.

<Example of production of magnetic carriers 1 to 32>
In a planetary motion type mixer (Nauta mixer VN type manufactured by Hosokawa Micron Corporation) maintained at a temperature of 60 ° C. under reduced pressure (1.5 kPa), a coating resin A and a coating resin B shown in Table 1 and Table 2, And the inorganic particle shown in Table 3 is thrown in. The ratio was as shown in Table 4, and 900 parts by mass of toluene was added to 100 parts by mass of the resin component and mixed until the resin component was sufficiently melted to prepare a coating resin solution. With respect to 100 parts by mass of the magnetic carrier core shown in Table 5, the resin solution was added to the coating resin so that the resin component had a solid content of 2.1 parts by mass.

  As a method of charging, first, a 1/3 amount of resin solution was charged, and solvent removal and coating operation were performed for 20 minutes. Next, a 1/3 amount of the resin solution was added, and the solvent was removed and applied for 20 minutes. Further, a 1/3 amount of the resin solution was added, and the solvent was removed and applied for 20 minutes.

  Thereafter, the magnetic carrier coated with the coating resin composition was transferred to a mixer (drum mixer UD-AT type manufactured by Sugiyama Heavy Industries Co., Ltd.) having spiral blades in a rotatable mixing container. The mixture container was heat-treated at a temperature of 120 ° C. for 2 hours under a nitrogen atmosphere while stirring at 10 rotations per minute. The obtained magnetic carrier was subjected to separation of low magnetic products by magnetic separation, passed through a sieve having an opening of 150 μm, and then classified by an air classifier. A magnetic carrier 1 having a volume distribution standard 50% particle size (D50) of 39.0 μm was obtained.

  Magnetic carriers 2 to 32 were obtained in the same manner except that the amount of the coating resin shown in Table 4 was changed depending on the type of the magnetic carrier core.

  Table 5 shows the physical properties of the obtained magnetic carriers 1 to 32.

<Production Example of Toner 1>
Binder resin (polyester resin acid value; 45 mg KOH / g OH value; 25 mg KOH / g Mn; 5,000 Mw; 70,000) 100 parts by mass I. Pigment Blue 15: 3 6.0 parts by mass, 1,4-di-t-butylsalicylic acid aluminum compound 0.5 part by mass, normal paraffin wax (melting point: 78 ° C.) 6.0 parts by mass After mixing well with a Henschel mixer (FM-75J type, manufactured by Mitsui Mining Co., Ltd.), 10 kg / h at a twin-screw kneader (PCM-30 type, manufactured by Ikekai Steel Co., Ltd.) set at a temperature of 130 ° C. It knead | mixed with the amount of Feed (the kneaded material temperature at the time of discharge is about 150 degreeC). The obtained kneaded product was cooled, coarsely crushed with a hammer mill, and then finely pulverized with a mechanical pulverizer (T-250: manufactured by Turbo Kogyo Co., Ltd.) at a Feed amount of 15 kg / hr. And the particle | grains whose weight average particle diameter is 5.5 micrometers were obtained.

  The obtained particles were classified using a rotary classifier (TTSP100, manufactured by Hosokawa Micron Corporation) to cut fine powder and coarse powder. Cyan toner particles 1 having a weight average particle diameter of 6.4 μm were obtained.

Further, the following materials were put into a Henschel mixer (FM-75 type, manufactured by Nippon Coke Co., Ltd.), the peripheral speed of the rotary blade was set to 35.0 (m / sec), and mixing was performed for 3 minutes. Cyan toner 1 was obtained by attaching silica and titanium oxide to the surfaces of the particles 1.
-Cyan toner particles 1 100 parts by mass-Silica 3.5 parts by mass (Silica fine particles prepared by the sol-gel method were surface-treated with 1.5% by mass of hexamethyldisilazane and then adjusted to a desired particle size distribution by classification) )
・ 0.5 parts by mass of titanium oxide (surface-treated with an octylsilane compound of metatitanic acid having anatase type crystallinity)

[Example 1]
10 parts by mass of cyan toner 1 was added to 90 parts by mass of magnetic carrier 1, and shaken with a shaker (YS-8D type: manufactured by Yayoi Co., Ltd.) to prepare 300 g of a two-component developer. The amplitude condition of the shaker was 200 rpm for 2 minutes.

  On the other hand, 95 parts by mass of cyan toner 1 is added to 5 parts by mass of magnetic carrier 1 and mixed for 5 minutes with a V-type mixer in a room temperature and normal humidity 23 ° C./50% RH (hereinafter N / N) environment. A developer was obtained.

  The following evaluation was performed using the two-component developer and the replenishment developer.

  As an image forming apparatus, a Canon color copier imageRUNNER ADVANCE C9075 PRO remodeling machine was used.

  A two-component developer was put in each color developing device, a replenishment developer container containing each color replenishment developer was set, an image was formed, and various evaluations were performed in an endurance test.

The durability test was performed from Step; 1 to Step; 4, with a total durability of 1 million sheets, and the environment and image ratio were changed as follows.
Step; 1 (from 0 to 200,000)
Temperature 23 ° C / Humidity 5RH% (N / L environment below)
FFH output chart with 3% image ratio Step; 2 (from 200,000 to 400,000)
Temperature 30 ° C / Humidity 80RH% (H / H environment)
FFH output chart with an image ratio of 1% Step; 3 (from 400,000 to 600,000)
Temperature 23 ° C / Humidity 5RH% (N / L environment below)
FFH output chart with 1% image ratio Step; 4 (from 600,000 to 1 million)
Temperature 30 ° C / Humidity 80RH% (H / H environment)
FFH output chart with 1% image ratio

  Here, FFH is a value in which 256 gradations are displayed in hexadecimal, 00H is the first gradation (white background part) of 256 gradations, and FFH is the 256th gradation (solid part) of 256 gradations. ).

Other conditions:
Paper: Laser beam printer paper CS-814 (81.4 g / m ² ) (Canon Marketing Japan Inc.)
Image formation speed: A4 size, full color, modified to output at 80 (sheets / min).
Development conditions: The development contrast can be adjusted to an arbitrary value, and it has been modified so that automatic correction by the main unit does not work.

  The voltage (Vpp) between the peaks of the alternating electric field was modified so that the frequency was 2.0 kHz and Vpp was changed from 0.7 kV to 1.8 kV in increments of 0.1 kV.

  Each color was modified to output a single color image.

  Each evaluation item is shown below.

(1) Carrier adhesion evaluation (Evaluation T)
Step: After outputting 600,000 sheets at Step 3, turn off the power during the output of the 00H output chart (A4 full white image) with 100% image ratio, and transparent adhesive on the electrostatic latent image carrier before cleaning Sampling was performed with the tape in close contact. The number of magnetic carrier particles adhering to the electrostatic latent image bearing member in 1 cm × 20 cm was counted, the number of adhering carrier particles per 1 cm ² was calculated, and evaluated according to the following criteria. The evaluation was performed with cyan single color.
A: 0 or more and less than 0.5 B: 0.5 or more and less than 1.0 C: 1.0 or more and less than 1.5 D: 1.5 or more and less than 2.0 E: 2.0 More than 2.5 pieces F: 2.5 pieces or more

  The results are shown in Table 5.

(2) Image density unevenness (Evaluation U)
Step: After outputting 600,000 sheets in Step 3, one sheet of an FFH output chart (A4 full face image) with an image ratio of 100% was output.

  The reflection density was judged by measuring the image density with a spectral densitometer 500 series (manufactured by X-Rite).

The measurement site is
0.5 cm position from the leading edge of the image (the one that was printed first), three points 5.0 cm, 15.0 cm, 25.0 cm from the left edge of the image (the one that was printed first is the upper side),
7.0 cm position from the tip of the image, 3 points 5.0 cm, 15.0 cm, 25.0 cm from the left edge of the image,
14.0 cm from the top of the image, 3 points 5.0 cm, 15.0 cm, 25.0 cm from the left end of the image,
The difference between the highest image density and the lowest image density was determined by setting a total of 12 points, 20.0 cm from the front end of the image and 3 points of 5.0 cm, 15.0 cm, and 25.0 cm from the left end of the image. Also, the evaluation result was the one with the highest density difference among the 50 sheets.
A: Less than 0.05 B: 0.05 or more and less than 0.10 C: 0.10 or more and less than 0.15 D: 0.15 or more and less than 0.20 E: 0.20 or more and less than 0.25 F: 0. 25 or more

  The results are shown in Table 5.

(3) Image density difference between each step before and after endurance (evaluation V, X)
At Step; 3 and Step; 4, one FFH output chart (A4 full solid image) with an image ratio of 100% was output at the beginning and end of each Step. For the output image, the reflection density was measured by the above density unevenness, and the average value of 12 points was calculated.

In the evaluation, the difference between the first and last 12-point average values of each step was determined according to the following criteria: A: 0.00 or more and less than 0.04 B: 0.04 or more and less than 0.08 C: 0.08 or more and 0.0. Less than 12 D: 0.12 or more and less than 0.16 E: 0.16 or more and less than 0.20 F: 0.20 or more

  The results are shown in Table 5.

(4) Fog (Evaluation Y)
In Step 3, after outputting 600,000 sheets, 10 sheets of a 00H output chart (A4 full white image) with an image ratio of 100% were output, and the whiteness of the white background portion was measured with a reflectometer (manufactured by Tokyo Denshoku Co., Ltd.). The fog density (%) was calculated from the difference between the whiteness and the whiteness of the transfer paper, and the highest fog density among the 10 sheets was evaluated as Y. The evaluation criteria are as follows.
A: Less than 0.4% B: 0.4% or more and less than 0.8% C: 0.8% or more and less than 1.2% D: 1.2% or more and less than 1.6% E: 1.6% or more Less than 2.0% F: 2.0% or more

  The results are shown in Table 5.

(5) Image density difference after endurance between Step; 3 and Step; 4 (Evaluation W)
At the end of Step; 3 and Step; 4, one FFH output chart (A4 full surface solid image) with an image ratio of 100% was output. For the output image, the reflection density was measured by the above density unevenness, and the average value of 12 points was calculated.

Evaluation evaluated the difference of the 12-point average value of Step; 3 and Step; 4 on the following reference | standard.
A: 0.00 or more and less than 0.05 B: 0.05 or more and less than 0.10 C: 0.10 or more and less than 0.15 D: 0.15 or more and less than 0.20 E: 0.20 or more and less than 0.25 F: 0.25 or more

  The results are shown in Table 5.

(6) In-machine scattering evaluation (Evaluation Z)
Step: 4 After the end of the endurance of 1 million sheets, the inside of the copier was opened and the state of toner scattering inside was confirmed. Judgment criteria were as follows: A: Slightly scattered only around the replenishing port B: Spattered only around the replenishing port C: Scattered around the replenishing port and around a very narrow range D: Spattering around and around the replenishing port E: Slight scattering on a part of the intermediate transfer member F: Splashing on a part of the intermediate transfer member

  However, in this study, none of them is at a level where toner is scattered outside the copying machine. The results are shown in Table 5.

(7) Comprehensive determination With respect to the evaluation ranks in the evaluation T to the evaluation Z, the evaluations T, V, Y, Z are (A = 5, B = 4, C = 3, D = 2, E = 1, F = 0), evaluations U, W, and X were digitized as (A = 10, B = 8, C = 6, D = 4, E = 2, F = 0), and the total value was determined according to the following criteria: .
A: 48 to 50 B: 40 to 47 C: 30 to 39 D: 20 to 29 E: 10 to 19 F: 9

  The results are shown in Table 6.

  In Example 1, it was a very good result in any evaluation. The evaluation results are shown in Tables 6 and 7.

[Examples 2 to 4]
In the same manner as in Example 1, a two-component developer and a replenishment developer were prepared using the magnetic carriers 2 to 4 at the same ratio as in Example 1. Evaluation was performed in the same manner as in Example 1 except that the obtained developer was used.

  In Examples 2 to 4, as in Example 1, the results were very good in any evaluation. The evaluation results are shown in Tables 6 and 7.

[Examples 5 and 6]
In the same manner as in Example 1, a two-component developer and a replenishment developer were prepared using magnetic carriers 5 and 6 at the same ratio as in Example 1. Evaluation was performed in the same manner as in Example 1 except that the obtained developer was used.

  In Examples 5 and 6, the viscoelastic characteristics are changed. This may cause a slight influence on the compatibility between the coating film strength and toughness of the resin coating layer, or may have a slight influence on the evaluation result in Step; 4, but the other results are very good. The evaluation results are shown in Tables 6 and 7.

[Examples 7 and 8]
Similarly to Example 1, a two-component developer and a replenishment developer were prepared using magnetic carriers 7 and 8 at the same ratio as in Example 1. Evaluation was performed in the same manner as in Example 1 except that the obtained developer was used.

  In Examples 7 and 8, the amount ratio of the coating resin A and the coating resin B is slightly changed. As a result, there is a slight influence on the compatibility between the coating film strength and the toughness, but the evaluation result in Step: 4 has a slight influence. The evaluation results are shown in Tables 6 and 7.

Example 9
In the same manner as in Example 1, a two-component developer and a replenishment developer were prepared using the magnetic carrier 9 at the same ratio as in Example 1. Evaluation was performed in the same manner as in Example 1 except that the obtained developer was used.

  In Example 9, no macromonomer was used in the coating resin A. This is because the coating strength tends to decrease, and the difference in density between Step; 3 and Step; 4 is slightly affected, but the other results are good. The evaluation results are shown in Tables 6 and 7.

Example 10
In the same manner as in Example 1, a two-component developer and a replenishment developer were prepared using the magnetic carrier 10 at the same ratio as in Example 1. Evaluation was performed in the same manner as in Example 1 except that the obtained developer was used.

  In Example 10, the inorganic particles were treated with stearic acid. As a result, the evaluation in the H / H environment was slightly deteriorated, and the difference in density between Step; 3 and Step; 4 was slightly affected. The evaluation results are shown in Tables 6 and 7.

Example 11
In the same manner as in Example 1, a two-component developer and a replenishment developer were prepared using the magnetic carrier 11 at the same ratio as in Example 1. Evaluation was performed in the same manner as in Example 1 except that the obtained developer was used.

  In Example 11, the inorganic particles were not treated. As a result, the evaluation in the H / H environment was slightly deteriorated, and the difference in density between Step; 3 and Step; 4 was slightly affected. The evaluation results are shown in Tables 6 and 7.

Example 12
In the same manner as in Example 1, a two-component developer and a replenishment developer were prepared using the magnetic carrier 12 at the same ratio as in Example 1. Evaluation was performed in the same manner as in Example 1 except that the obtained developer was used.

  In Example 12, the hydroxy group concentration of the inorganic particles was low. Thereby, the coating film strength tends to decrease. As a result, the long-term durability decreased, and the evaluation of Step; 4 was affected. In addition, the density difference between Step; 3 and Step; 4 was slightly affected, but the other results were satisfactory. The evaluation results are shown in Tables 6 and 7.

Example 13
In the same manner as in Example 1, a two-component developer and a replenishment developer were prepared using the magnetic carrier 13 at the same ratio as in Example 1. Evaluation was performed in the same manner as in Example 1 except that the obtained developer was used.

  In Example 13, calcium oxide was used. As a result, there was an effect in both Step; 3 and Step; 4 because of the variation in chargeability, but there was no problem in other cases. The evaluation results are shown in Tables 6 and 7.

[Examples 14 and 15]
In the same manner as in Example 1, a two-component developer and a replenishment developer were prepared using the magnetic carriers 14 and 15 at the same ratio as in Example 1. Evaluation was performed in the same manner as in Example 1 except that the obtained developer was used.

  In Examples 14 and 15, the particle diameter of the inorganic particles was changed. As a result, the evaluation of Step; 4 was affected, possibly due to the effect of coexistence of coating film strength and toughness. But other than that, there was no problem. The evaluation results are shown in Tables 6 and 7.

[Examples 16 and 17]
In the same manner as in Example 1, a two-component developer and a replenishment developer were prepared using the magnetic carriers 16 and 17 at the same ratio as in Example 1. Evaluation was performed in the same manner as in Example 1 except that the obtained developer was used.

  In Examples 16 and 17, the particle size of the inorganic particles was changed. As a result, the evaluation of Step; 4 was affected, possibly due to the effect of coexistence of coating film strength and toughness. But other than that, there was no problem. The evaluation results are shown in Tables 6 and 7.

[Examples 18 and 19]
In the same manner as in Example 1, a two-component developer and a replenishment developer were prepared using the magnetic carriers 18 and 19 at the same ratio as in Example 1. Evaluation was performed in the same manner as in Example 1 except that the obtained developer was used.

  In Examples 18 and 19, the usage ratio of the coating resin A and the coating resin B was greatly changed. As a result, the influence on the coexistence of the coating film strength and the toughness was affected, and both Step; 3 and Step; 4 affected the evaluation. However, it was a usable level as a carrier for copying machines. The evaluation results are shown in Tables 6 and 7.

[Examples 20 and 21]
In the same manner as in Example 1, a two-component developer and a replenishment developer were prepared using the magnetic carriers 20 and 21 at the same ratio as in Example 1. Evaluation was performed in the same manner as in Example 1 except that the obtained developer was used.

  In Examples 20 and 21, the acid value of the coating resin B was greatly changed. As a result, the influence on the coexistence of the coating film strength and the toughness was affected, and both Step; 3 and Step; However, the result was a usable level as a carrier for a copying machine. The evaluation results are shown in Tables 6 and 7.

[Example 22]
In the same manner as in Example 1, a two-component developer and a replenishment developer were prepared using the magnetic carrier 22 at the same ratio as in Example 1. Evaluation was performed in the same manner as in Example 1 except that the obtained developer was used.

  In Example 22, the acid value of the coating resin A was increased. Thereby, the smoothness of the resin coating layer was affected, and both Step; 3 and Step; 4 affected the evaluation. However, the result was a usable level as a carrier for a copying machine. The evaluation results are shown in Tables 6 and 7.

[Comparative Examples 1 and 2]
In the same manner as in Example 1, a two-component developer and a replenishment developer were prepared using magnetic carriers 23 and 24 at the same ratio as in Example 1. Evaluation was performed in the same manner as in Example 1 except that the obtained developer was used.

  In Comparative Examples 1 and 2, the content of the coating resin A or B was greatly changed. As a result, the effect of both Step 3 and Step 4 was affected because of the great influence on the compatibility between the coating strength and the toughness. In particular, the density difference between Step; 3 and Step; 4 was also slightly affected. The evaluation results are shown in Tables 6 and 7.

[Comparative Example 3]
In the same manner as in Example 1, a two-component developer and a replenishment developer were prepared using the magnetic carrier 25 at the same ratio as in Example 1. Evaluation was performed in the same manner as in Example 1 except that the obtained developer was used.

  In Comparative Example 3, a very large amount of inorganic particles was added. As a result, the toughness of the coating resin layer was particularly deteriorated, and the result of Step; 4 was particularly deteriorated. The evaluation results are shown in Tables 6 and 7.

[Comparative Examples 4 and 5]
In the same manner as in Example 1, a two-component developer and a replenishment developer were prepared using magnetic carriers 26 and 27 in the same ratio as in Example 1. Evaluation was performed in the same manner as in Example 1 except that the obtained developer was used.

  In Comparative Examples 4 and 5, the acid value of the coating resin B was changed greatly.

  In Comparative Example 4, because the acid value of the coating resin B was too high, the toughness of the resin coating layer could not be obtained, and in particular, the result of Step; 4 was deteriorated.

  In Comparative Example 5, the coating layer strength of the resin coating layer was insufficient because the acid value of the coating B was too low, and in particular, the result of Step; 4 was deteriorated. The evaluation results are shown in Tables 6 and 7.

[Comparative Example 6]
In the same manner as in Example 1, a two-component developer and a replenishment developer were prepared using the magnetic carrier 28 at the same ratio as in Example 1. Evaluation was performed in the same manner as in Example 1 except that the obtained developer was used.

  In Comparative Example 6, the acid value of the coating resin A is too large. As a result, the smoothness of the surface of the resin coating layer, which is a characteristic of the coating resin A, was impaired, and the results were deteriorated for both Step; 3 and Step; The evaluation results are shown in Tables 6 and 7.

[Comparative Example 7]
In the same manner as in Example 1, a two-component developer and a replenishment developer were prepared using the magnetic carrier 29 at the same ratio as in Example 1. Evaluation was performed in the same manner as in Example 1 except that the obtained developer was used.

  In Comparative Example 7, no (meth) acrylic acid ester monomer having an alicyclic hydrocarbon group was used in the coating resin A. As a result, the smoothness of the surface of the resin coating layer, which is a characteristic of the coating resin A, was impaired, and the results were deteriorated for both Step; 3 and Step; The evaluation results are shown in Tables 6 and 7.

[Comparative Example 8]
Similarly to Example 1, a two-component developer and a replenishment developer were prepared using the magnetic carrier 30 at the same ratio as in Example 1. Evaluation was performed in the same manner as in Example 1 except that the obtained developer was used.

  In Comparative Example 8, an acrylic resin having an acid value having a (meth) acrylic acid ester monomer having an alicyclic hydrocarbon group is used in the coating resin A, and the coating resin B is used. There is no example. This is because of the influence of the resin self-aggregation or the desired effect on the smoothness of the remaining film surface and the coating film strength, and the results deteriorated for both Steps 3 and 4; The evaluation results are shown in Tables 6 and 7.

[Comparative Example 9]
In the same manner as in Example 1, a two-component developer and a replenishment developer were prepared using the magnetic carrier 31 at the same ratio as in Example 1. Evaluation was performed in the same manner as in Example 1 except that the obtained developer was used.

  In Comparative Example 9, the coating resin A does not use the (meth) acrylic acid ester monomer having an alicyclic hydrocarbon group, uses an acrylic resin having an acid value, and does not use the coating resin B. It is. As in Comparative Example 8, the effects of resin self-aggregation, the smoothness of the coating film surface and the coating film strength were not obtained, and the results deteriorated for both Step 3 and Step 4; The evaluation results are shown in Tables 6 and 7.

[Comparative Example 10]
In the same manner as in Example 1, a two-component developer and a replenishment developer were prepared using the magnetic carrier 32 at the same ratio as in Example 1. Evaluation was performed in the same manner as in Example 1 except that the obtained developer was used.

  In Comparative Example 10, the coating resin A is a (meth) acrylic acid ester monomer having an alicyclic hydrocarbon group, a macromonomer is used, an acrylic resin having an acid value is used, and carbon dioxide is used as inorganic particles. Potassium was used. As in Comparative Examples 8 and 9, the effect of the resin self-aggregation, the smoothness of the coating film surface and the coating film strength were not obtained, and the results deteriorated for both Step 3 and Step 4; The evaluation results are shown in Tables 6 and 7.

  1, 1K, 1Y, 1C, 1M: electrostatic latent image carrier, 2, 2K, 2Y, 2C, 2M: charger, 3, 3K, 3Y, 3C, 3M: exposure unit, 4, 4K, 4Y, 4C 4M: developing device, 5: developing container, 6, 6K, 6Y, 6C, 6M: developer carrier, 7: magnet, 8: regulating member, 9: intermediate transfer member, 10K, 10Y, 10C, 10M: intermediate Transfer charger, 11: Transfer charger, 12: Transfer material (recording medium), 13: Fixing device, 14: Intermediate transfer body cleaner, 15, 15K, 15Y, 15C, 15M: Cleaner, 16: Pre-exposure

Claims (13)

A magnetic carrier having a resin coating layer formed on the surface of a magnetic carrier core,
The resin coating layer is
i) a coating resin A having an acid value of 0.0 mgKOH / g or more and 3.0 mgKOH / g or less, obtained by polymerizing a monomer containing an acrylate or methacrylate having an alicyclic hydrocarbon group;
ii) Coating resin B having an acid value of 4.0 mgKOH / g or more and 50.0 mgKOH / g or less obtained by polymerizing a monomer containing acrylic acid or methacrylic acid;
iii) metal oxide particles containing a metal element selected from Mg, Al, Zn, Ca, Sr, and Ti, and / or one or more inorganic particles selected from carbonate particles,
When the total resin component contained in the resin coating layer is 100 parts by mass,
i) The content of the coating resin A is 10 parts by mass or more and 90 parts by mass or less,
ii) The content of the coating resin B is 10 parts by mass or more and 90 parts by mass or less,
iii) Content of the said inorganic particle is 1.0 mass part or more and 50.0 mass parts or less, The magnetic carrier characterized by the above-mentioned.   2. The magnetic carrier according to claim 1, wherein the number average particle diameter of primary particles of the inorganic particles is 50 nm or more and 2000 nm or less. _3. The magnetic carrier according to claim 1, wherein the metal oxide particles are one or more selected from MgO, Al ₂ O ₃ , ZnO, TiO ₂ , SrTiO ₃ , CaTiO ₃ , and MgTiO _3. . The magnetic carrier according to claim 1 or 2, wherein the carbonate particles are one or more selected from CaCO ₃ , MgCO ₃ , and SrCO ₃ .   The magnetic carrier according to any one of claims 1 to 3, wherein the surface of the inorganic particles has a hydroxy group concentration of 10.0% or more.   The said inorganic particle is a particle | grain surface-treated with the 1 type, or 2 or more types of compound selected from a silane coupling agent, a silane compound, a titanate coupling agent, and an aluminate coupling agent. The magnetic carrier according to any one of the above. The coating resin A is a polymer obtained by copolymerizing an acrylate ester or methacrylic acid having an alicyclic hydrocarbon group and a macromonomer,
The macromonomer is one or more selected from methyl acrylate, methyl methacrylate, butyl acrylate, butyl methacrylate, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, styrene, acrylonitrile, and methacrylonitrile. The magnetic carrier according to any one of claims 1 to 6, which is a macromonomer obtained by polymerizing monomers.   The coating resin B is a polymer obtained by copolymerizing acrylic acid and a monomer having a polar group, and the monomer having the polar group has a carboxy group and / or a sulfonic acid group. The magnetic carrier according to any one of claims 1 to 7. In the viscoelasticity measurement of the resin coating layer at 70 ° C. or more and 100 ° C. or less, the minimum value of the storage elastic modulus (G ′) is 9.0 × 10 ⁷ Pa or more and 1.0 × 10 ¹⁰ Pa or less, and the loss elastic modulus The magnetic carrier according to claim 1, wherein the minimum value of (G ″) is 9.0 × 10 ⁶ Pa or more and 1.0 × 10 ⁹ Pa or less. A two-component developer containing a toner having toner particles containing a binder resin and a colorant, and a magnetic carrier,
A two-component developer, wherein the magnetic carrier is the magnetic carrier according to any one of claims 1 to 9. A charging step for charging the electrostatic latent image carrier, an electrostatic latent image forming step for forming an electrostatic latent image on the surface of the electrostatic latent image carrier, and the electrostatic latent image using a two-component developer. A developing step of developing and forming a toner image, a transferring step of transferring the toner image to a transfer material with or without an intermediate transfer member, and a fixing step of fixing the transferred toner image to the transfer material The developer for replenishment is replenished to the developer in accordance with a decrease in the toner concentration of the two-component developer in the developer, and the excess magnetic carrier in the developer is supplied to the developer as needed. A developer for replenishment for use in an image forming method discharged from
The replenishment developer contains a replenishment magnetic carrier and a toner having toner particles containing a binder resin, a colorant, and a release agent,
The replenishment developer contains the toner in a blending ratio of 2 parts by mass or more and 50 parts by mass or less with respect to 1 part by mass of the magnetic carrier for replenishment.
The replenishment developer, wherein the replenishment magnetic carrier is the magnetic carrier according to any one of claims 1 to 9. A charging step for charging the electrostatic latent image carrier, an electrostatic latent image forming step for forming an electrostatic latent image on the surface of the electrostatic latent image carrier, and a two-component developer in the developing device. A developing process for forming a toner image using the toner, a transfer process for transferring the toner image to a transfer material with or without an intermediate transfer member, and a fixing process for fixing the transferred toner image to the transfer material. And the developer for replenishment is replenished to the developer as the toner concentration of the two-component developer in the developer decreases, and excess magnetic carrier in the developer is removed from the developer as needed. A discharged image forming method comprising:
The replenishment developer contains a replenishment magnetic carrier and a toner having toner particles containing a binder resin, a colorant, and a release agent,
The replenishment developer contains the toner in a blending ratio of 2 parts by mass or more and 50 parts by mass or less with respect to 1 part by mass of the magnetic carrier for replenishment.
The image forming method according to claim 1, wherein the replenishing magnetic carrier is the magnetic carrier according to claim 1. A charging step for charging the electrostatic latent image carrier, an electrostatic latent image forming step for forming an electrostatic latent image on the surface of the electrostatic latent image carrier, and the electrostatic latent image using a two-component developer. A developing step of developing and forming a toner image, a transferring step of transferring the toner image to a transfer material with or without an intermediate transfer member, and a fixing step of fixing the transferred toner image to the transfer material An image forming method comprising:
The image forming method according to claim 10, wherein the two-component developer according to claim 10 is used as the two-component developer.

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