JP7646376B2 - Magnetic carrier, two-component developer, and replenishment developer - Google Patents

Description

The present invention relates to a magnetic carrier, a two-component developer, and a replenishment developer used in an image forming method for visualizing an electrostatic image using electrophotography.

Conventionally, electrophotographic image formation methods generally involve forming an electrostatic latent image on an electrostatic latent image carrier using various means, and then attaching toner to the electrostatic latent image to develop it. In this development, a two-component development method is widely used in which carrier particles called magnetic carrier particles are mixed with the toner, which are then triboelectrically charged to give the toner an appropriate amount of positive or negative charge, and the charge is used as the driving force for development.

The two-component development method allows the magnetic carrier to be given functions such as stirring, transporting, and charging the developer, so the division of functions between the carrier and the toner is clear, and this has the advantage of good controllability of developer performance. Here, magnetic carrier particles often have a core that is magnetized to achieve transportability, and a resin coating on the core that provides the ability to impart charge to the toner.

In recent years, technological advances in the field of electrophotography have created a demand for greater longevity for the main body, and magnetic carriers are required to maintain their charge-imparting ability even after long-term use. However, it is generally known that magnetic carriers, when used for a long period of time, experience a decrease in charge sites due to the adhesion of toner components, and moisture adsorption in cracks that occur in the coating resin on the surface of the magnetic carrier particles, resulting in a decrease in charge-imparting ability and a change in concentration.

To solve the above problems, examples of techniques for improving the contamination resistance and charge retention of the surface of magnetic carrier particles include the use of silicone resins, which are materials with low surface free energy, as coating resins (Patent Documents 1 and 2). In addition, Patent Document 3 discloses a technique for improving charge retention by adding hydrophilic fine particles as an intermediate layer to the interface between the core of the magnetic carrier particle and the coating resin, thereby absorbing moisture adhering to the surface of the magnetic carrier particle into the intermediate layer.

JP 2002-91093 A JP 2015-138230 A JP 2016-194692 A

However, generally, materials with low surface free energy such as silicone resins can suppress adhesion of toner components, but they have weak interactions between molecules and are easily destroyed by external forces. For this reason, when silicone resins are used as the coating resin for magnetic carrier particles, the coating resin can be worn down by mechanical loads that occur during stirring and transport within the developing machine, reducing the surface resistance of the magnetic carrier particles and thus reducing the charge-imparting ability of the magnetic carrier.

The present invention provides a magnetic carrier which solves the above problems.
Specifically, the present invention provides a magnetic carrier containing a silicone modified resin and hydrophilic fine particles in a coating resin layer, which can withstand long-term use in a high-temperature and high-humidity environment.

（式（１）および式（２）中、Ｒ１は水素原子またはメチル基である。）
微粒子の官能基濃度＝（Ｘ線光電子分光測定によるフッ素値／ｇ）÷（微粒子の比表面積／ｇ） （計算式１）
磁性キャリア粒子の官能基濃度＝（Ｘ線光電子分光測定によるフッ素値／ｇ）÷（磁性キャリア粒子の比表面積／ｇ） （計算式２） The magnetic carrier of the present invention is
A magnetic carrier comprising magnetic carrier particles having a magnetic core and a resin coating layer coating the surface of the magnetic core,
the coating resin layer contains a silicone modified resin and fine particles,
the fine particles have on their surfaces a functional group represented by formula (1) or a functional group represented by formula (2) at a functional group concentration of 20% or more of the fine particles;
the magnetic carrier particles have on their surfaces a functional group represented by the formula (1) or a functional group represented by the formula (2) at a functional group concentration of 0.05% or less on the magnetic carrier particles;
The functional group concentration of the fine particles and the functional group concentration of the magnetic carrier particles are characterized by being calculated by Formula 1 and Formula 2, respectively.

(In formula (1) and formula (2), R1 is a hydrogen atom or a methyl group.)
Concentration of functional groups in fine particles=(fluorine value measured by X-ray photoelectron spectroscopy/g)÷(specific surface area of fine particles/g) (Formula 1)
Concentration of functional group of magnetic carrier particle=(fluorine value measured by X-ray photoelectron spectroscopy/g)÷(specific surface area of magnetic carrier particle/g) (Formula 2)

The developer of the present invention contains the magnetic carrier and a toner.
The replenishing developer of the present invention contains the above-mentioned magnetic carrier and toner.

According to the present invention, it is possible to achieve both excellent contamination resistance and abrasion resistance even when used for a long period of time in a high temperature and humidity environment, and to further improve the charge retention.

1 is a schematic diagram illustrating an example of an image forming method. FIG. 1 is a schematic diagram showing an example of an image forming method using a full-color image forming apparatus. FIG. 1 is a schematic diagram showing an example of an image forming method using a replenishment developer. FIG. 2 is a schematic diagram illustrating an example of a surface treatment device for toner particles.

In the present invention, the notation "XX to XX" indicating a numerical range means a numerical range including the endpoints, that is, the lower limit and the upper limit, unless otherwise specified.

（式（１）および式（２）中、Ｒ１は水素原子またはメチル基である。） The magnetic carrier of the present invention includes magnetic carrier particles having a magnetic core and a coating resin layer coating the surface of the magnetic core. The coating resin layer contains a silicone modified resin and fine particles, and the fine particles have a functional group represented by formula (1) or a functional group represented by formula (2) on the surface of the fine particles at a functional group concentration of 20% or more, and the functional group concentration of the fine particles is calculated by formula 1.
Concentration of functional groups in fine particles=(fluorine value measured by X-ray photoelectron spectroscopy/g)÷(specific surface area of fine particles/g) (Formula 1)
Further, the magnetic carrier particles have on their surfaces the functional group represented by the formula (1) or the functional group represented by the formula (2) at a functional group concentration of 0.05% or less, and the functional group concentration of the magnetic carrier particles is calculated by the following formula 2.
Concentration of functional group of magnetic carrier particle=(Fluorine value measured by X-ray photoelectron spectroscopy/g)÷(Specific surface area of magnetic carrier particle/g) (Formula 2)

(In formula (1) and formula (2), R1 is a hydrogen atom or a methyl group.)

By controlling the functional group concentration of the microparticles and the functional group concentration of the magnetic carrier particles within the above range, it is possible to provide a magnetic carrier that has excellent contamination resistance and abrasion resistance even when used for a long period of time in a high temperature and high humidity environment, and further improves the charge retention.

The present inventors consider the following regarding the effects of using a magnetic carrier having such a structure.
When the coating resin layer that coats the surface of the magnetic carrier particles contains a silicone modified resin and hydrophilic fine particles having a functional group represented by formula (1) or formula (2) on the surface at a functional group concentration of 20% or more, the siloxane moiety of the silicone modified resin having a hydrophobic structure is oriented on the surface of the magnetic carrier particles, improving the contamination resistance of the magnetic carrier. As a result of the orientation of the siloxane moiety of the silicone modified resin on the surface of the magnetic carrier particles, the hydrophilic fine particles are present inside the coating resin layer, so that a filler effect is exhibited inside the magnetic carrier particles, improving the wear resistance of the magnetic carrier. In addition, even if the magnetic carrier is used for a long period of time in a high humidity environment, the hydrophilic fine particles present inside the magnetic carrier particles absorb the moisture attached to the surface of the magnetic carrier particles, so that the charging of the surface of the magnetic carrier particles is not alleviated, and it is considered that the charging property of the magnetic carrier is maintained.

If the functional group concentration of the functional group represented by formula (1) or formula (2) on the surface of the fine particles is less than 20%, the fine particles will not be hydrophilic, and the charge retention of the magnetic carrier in a high humidity environment will deteriorate. In addition, it is preferable that the functional group concentration of the functional group represented by formula (1) or formula (2) on the surface of the magnetic carrier particle is 0.05% or less. When the functional group concentration is 0.05% or less, the charge retention can be sufficiently maintained.

It is preferable that the concentration of Si atoms on the surface of the magnetic carrier particles is 1.0 atomic % or more and 8.0 atomic % or less according to X-ray photoelectron spectroscopy (XPS) analysis. By having a concentration of Si atoms of 1.0 atomic % or more, the surface free energy of the magnetic carrier particles can be lowered, further improving the contamination resistance. By having a concentration of Si atoms of 8.0 atomic % or less, the intermolecular interaction near the surface of the magnetic carrier particles is increased, further improving the wear resistance.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of the present invention will be described in detail.
The magnetic carrier of the present invention comprises magnetic carrier particles having a magnetic core and a resin coating layer coating the surface of the magnetic core.

[Coating resin layer]
The coating resin layer contains a silicone modified resin and fine particles.

<Silicone modified resin>
The silicone-modified resin contains (i) one or more units selected from the units represented by the following formulas (3) to (6), and (ii) one unit selected from the units represented by the following formulas (3') to (5'), and has a terminal unit represented by formula (6). In addition, (iii) the units represented by formulas (3') to (5') are connected to the units represented by formulas (3) to (6) so as to share one oxygen atom. From the viewpoint of contamination resistance and abrasion resistance, it is preferable that the total content of the units represented by formulas (3) to (6) and the units represented by formulas (3') to (5') in the silicone-modified resin is 3% by mass or more and 50% by mass or less.

In formulas (3) to (6) and formulas (3') to (5'), R2 to R7 are each independently a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, a phenyl group, or an alkenyl group having 2 to 4 carbon atoms, and -O _1/2 indicates that an O is shared with the adjacent Si atom. In addition, in formulas (3') to (5'), ** represents a site bonding to an alkylene group or a site bonding to an oxygen atom bonded to a carbon atom.

In R2 to R7, examples of alkyl groups having 1 to 4 carbon atoms include methyl, ethyl, propyl, isopropyl, n-butyl, s-butyl, t-butyl, and isobutyl groups. Examples of alkenyl groups having 2 to 4 carbon atoms include vinyl, propenyl, butenyl, and butadienyl groups.

The silicone modified resin is not particularly limited, but examples include silicone modified (meth)acrylic resin, silicone modified urethane resin, silicone modified polyester resin, silicone modified epoxy resin, silicone modified polyolefin resin, silicone modified phenolic resin, silicone modified melamine resin, etc. Among these, silicone modified (meth)acrylic resin is preferable from the viewpoint of abrasion resistance.

The silicone modified resin is mainly composed of a unit represented by the following formula (7) and a unit represented by the following formula (8), and when the mass of the unit represented by formula (7) is a and the mass of the unit represented by formula (8) is b, it is preferable that the ratio a/b of the mass a of the unit represented by formula (7) to the mass b of the unit represented by formula (8) is 1.00 or more and 30.0 or less.

式（７）中、Ｒ８は、水素原子またはメチル基であり、Ｒ９は、炭素数１～６の炭化水素基、水酸基を置換基として有する炭素数２～４のアルキル基、または、カルボキシ基を置換基として有する炭素数１～４のアルキル基であり、ｌは、１以上の整数である。

In formula (7), R8 is a hydrogen atom or a methyl group, R9 is a hydrocarbon group having 1 to 6 carbon atoms, an alkyl group having 2 to 4 carbon atoms and having a hydroxyl group as a substituent, or an alkyl group having 1 to 4 carbon atoms and having a carboxy group as a substituent, and l is an integer of 1 or greater.

式（８）中、Ｒ１０は、水素原子またはメチル基であり、Ｒ１１は、水素原子または炭素数１～６の炭化水素基であり、Ｒ１２は、単結合、または、炭素数１～５のアルキレンであり、ｍは、１以上の整数である。＊は、シロキサン部位が結合する結合部位であって、下記式（３’）～（５’）で表されるいずれかのユニットの＊＊につながる。

式（３’）～式（５’）で表されるユニットには、下記式（３）～（６）で表されるいずれかのユニットが、１つの酸素原子を共有するように、１つ或いは繰り返してつながっている。

シロキサン部位の末端は、上記式（６）で表されるユニットであり、式（３’）～（５’）及び式（３）～（６）におけるＲ２～Ｒ７は、それぞれ独立して、水素原子、炭素数１～４のアルキル基またはフェニル基であり、－Ｏ_１／２は隣り合うＳｉ原子とＯを共有していることを表し、シロキサン部位中のケイ素元素の数は２～１５０である。

In formula (8), R10 is a hydrogen atom or a methyl group, R11 is a hydrogen atom or a hydrocarbon group having 1 to 6 carbon atoms, R12 is a single bond or an alkylene group having 1 to 5 carbon atoms, and m is an integer of 1 or more. * is a bonding site where a siloxane moiety is bonded, and leads to ** of any of the units represented by the following formulas (3') to (5').

To the units represented by formulae (3') to (5'), any of the units represented by the following formulae (3) to (6) is connected once or repeatedly so as to share one oxygen atom.

The terminal of the siloxane moiety is a unit represented by the above formula (6), R2 to R7 in formulas (3') to (5') and formulas (3) to (6) are each independently a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, or a phenyl group, -O _1/2 represents that an O is shared with an adjacent Si atom, and the number of silicon atoms in the siloxane moiety is 2 to 150.

In R9 and R11, examples of the hydrocarbon group having 1 to 6 carbon atoms include a methyl group, an ethyl group, a propyl group, an isopropyl group, a cyclopropyl group, an n-butyl group, an s-butyl group, a t-butyl group, an isobutyl group, a cyclobutyl group, a pentyl group, a neopentyl group, a cyclopentyl group, a hexyl group, a cyclohexyl group, etc. In R9, examples of the alkyl group having 2 to 4 carbon atoms substituted with a hydroxyl group include a 2-hydroxyethyl group, a 3-hydroxypropyl group, a 2-hydroxyisopropyl group, a hydroxycyclopropyl group, a 4-hydroxybutyl group, a hydroxycyclobutyl group, etc., and examples of the alkyl group having 1 to 4 carbon atoms substituted with a carboxy group (not including the number of carbon atoms of the carboxy group) include a carboxymethyl group, a 2-carboxyethyl group, a 3-carboxypropyl group, a 4-carboxybutyl group, etc. In R12, examples of the alkylene having 1 to 5 carbon atoms include a methylene group, an ethylene group, a propylene group, a butylene group, a pentylene group, a cyclopropylene group, a cyclobutylene group, a cyclopentylene group, etc. In R2 to R7, examples of the alkyl group having 1 to 4 carbon atoms include a methyl group, an ethyl group, a propyl group, an isopropyl group, an n-butyl group, an s-butyl group, a t-butyl group, and an isobutyl group.
The units represented by formulae (3) to (5) each have a plurality of -O _1/2 groups, and therefore are repeatedly bonded to other units. When the unit represented by formula (6) is bonded, the repetition stops and the unit becomes a terminal unit.

If a/b is less than 1.00, the proportion of units represented by formula (8) is too high, resulting in a structure with too little adhesion to the magnetic core, and thus poor wear resistance. Conversely, if a/b is greater than 30.0, the surface free energy becomes too high, and thus contamination resistance deteriorates. It is preferable that the number of silicon atoms in the siloxane moiety is 2 to 150, since this makes it easy to adjust the range of a/b to 1.00 or more and 30.0 or less.

The coating resin layer may further contain a non-silicone-modified (meth)acrylic resin. When the coating resin layer further contains a non-silicone-modified (meth)acrylic resin, the non-silicone-modified (meth)acrylic resin chains and the molecular chains other than the siloxane moiety of the silicone-modified resin become entangled, thereby further improving the abrasion resistance.

<Microparticles>
The fine particles contained in the resin coating layer of the magnetic carrier particles are not particularly limited to organic particles or inorganic particles, but are preferably inorganic particles from the viewpoint of improving abrasion resistance due to the filler effect.
Examples of inorganic particles include particles of _carbon black, _SrTiO3 , _TiO2 , _Al2O3 , MgO, _SiO2 , and the like.

The volume average particle size of the primary particles of the fine particles used in the present invention is preferably 10 nm or more and 100 nm or less. If it is smaller than 10 nm, the particles tend to aggregate and are dispersed in the coating resin layer in the form of agglomerates. These agglomerates cause protrusions, and the frictional stress on the protrusions increases during long-term use, reducing the wear resistance. If it exceeds 100 nm, the fine particles themselves form protrusions, and the frictional stress on the protrusions increases during long-term use, reducing the wear resistance.

The concentration of the functional group represented by formula (1) or formula (2 ₎ on the surface of _the fine particles is 20% or more, preferably 30% or more. The fine particles may have a structure in which the functional group represented by formula (1) or formula (2) is attached to the terminal of the surface of a particle such as carbon black, _SrTiO3 , _TiO2 , Al2O3, MgO, or _SiO2 via an organic group.
The functional group concentration of the fine particles indicates the ratio of the functional group to the specific surface area of the fine particles in XPS measurement.

It is preferable that the magnetic carrier particles contain 1.0 parts by mass or more and 20.0 parts by mass or less of fine particles per 100 parts by mass of the resin in the coating resin layer, since the magnetic carrier particles have a functional group represented by formula (1) or a functional group represented by formula (2) at a functional group concentration of 0.05% or less.

<Surface treatment method for fine particles>
One method for surface treatment of fine particles is, for example, a method in which commercially available inorganic particles or carbon black are subjected to an oxidation treatment to introduce hydrophilic groups.
Specific examples of the oxidation treatment method include gas phase oxidation and liquid phase oxidation. The gas phase oxidation method is an oxidation method by contact with air, and the surface of the fine particles is oxidized by reaction with nitrogen oxides or ozone. The liquid phase oxidation method oxidizes the surface of the fine particles using an oxidizing agent such as nitric acid, potassium permanganate, potassium dichromate, chlorous acid, perchloric acid, hypohalogen hydrochloric acid, hydrogen peroxide, aqueous bromine solution, or aqueous ozone solution. In addition, the surface of carbon black can be oxidized by plasma treatment or the like.

Specific examples of methods for introducing hydrophilic groups by oxidizing the surface of fine particles as described above include the following methods. When treating the surface of carbon black by liquid-phase oxidation, hydrophilically treated fine particles can be obtained by placing the carbon black in a suitable container, adding an aqueous nitric acid solution and refluxing it, followed by washing and drying. When treating the surface of fine particles by gas-phase oxidation, hydrophilically treated fine particles can be obtained by placing the fine particles in an ozone treatment device and exposing the fine particles to an ozone atmosphere generated by an ozone generator.

As one of the hydrophilic treatment methods, for example, a method of introducing carboxyl groups to hydroxyl groups on the particle surface using a carboxylating agent of a lower fatty acid can be mentioned. Furthermore, methyl groups can be introduced to the introduced hydroxyl groups by using a methylating agent such as methyl iodide or dimethyl sulfate.

Specific examples of carboxylating agents for lower fatty acids include dicarboxylic acids such as succinic acid, maleic acid, phthalic acid, succinic anhydride, maleic anhydride, and phthalic anhydride, and their acid anhydrides. Two or more of these carboxylating agents for lower fatty acids may be mixed and used. In addition, a methyl group can be introduced by using a methylating agent or by carrying out methyl esterification on the introduced carboxyl group.

As a method for introducing methyl groups into the introduced carboxyl groups, for example, the following method is preferably used. Each particle type is placed in a suitable container, and the system is placed under a nitrogen atmosphere. Then, anhydrous toluene, triethylamine, dimethylaminopyridine, and an acid anhydride of a dicarboxylic acid are added and reacted at room temperature to obtain chemically modified particles. The obtained chemically modified particles are then placed in a suitable container, and methanol and calcium carbonate are added and reacted at room temperature. After that, the reaction is stopped, and the particles are washed and dried to obtain fine particles having dicarboxylic acids at the ends that have been methyl esterified.

<Magnetic Carrier Particles>
As the magnetic core of the magnetic carrier particle, known magnetic particles such as magnetite particles, ferrite particles, magnetic material-dispersed resin particles, etc. can be used. Among them, magnetic particles obtained by filling the pores of porous magnetic particles with a resin or magnetic material-dispersed resin particles, i.e., magnetic particles containing a magnetic oxide and a resin composition, can reduce the specific gravity of the magnetic carrier particle and are preferred from the viewpoint of extending the life of the magnetic carrier particle.

Lowering the specific gravity of magnetic carrier particles, for example, reduces the load on the toner in the developer state inside the developing device, prevents the adhesion of toner components to the surface of the magnetic carrier particles, and reduces the load between magnetic carrier particles, leading to further suppression of peeling, chipping, and abrasion of the resin coating layer. It also improves dot reproducibility, making it possible to obtain high-definition images.

Examples of materials for the porous magnetic particles include magnetite, ferrite, etc. Among these, ferrite is preferred from the viewpoint of ease of control of the porous structure of the porous magnetic particles and ease of adjustment of the resistance of the porous magnetic particles.
Ferrite is a sintered body represented by the following general formula:
(M1 ₂ O) _x (M2O) _y (Fe ₂ O ₃ ) _z
(In the above general formula, M1 is a monovalent metal, M2 is a divalent metal, and when x+y+z=1.0, 0≦x≦0.8, 0≦y≦0.8, and 0.2<z<1.0.)

In the above general formula, examples of M1 and M2 include Li, Fe, Mn, Mg, Sr, Cu, Zn, Ca, Ni, Co, Ba, Y, V, Bi, In, Ta, Zr, B, Mo, Na, Sn, Ti, Cr, Al, Si, and rare earth elements.

In the case of porous magnetic particles, it is preferable to appropriately control the surface irregularities of the porous magnetic particles in order to maintain an appropriate amount of magnetization and to keep the pore size within an appropriate range. It is also preferable that the speed of the ferritization reaction is easily controlled, and that the resistivity and magnetic force of the porous magnetic particles are easily controlled. From these viewpoints, among ferrites, Mn-based ferrites, Mn-Mg-based ferrites, Mn-Mg-Sr-based ferrites, and Li-Mn-based ferrites that contain Mn are more preferable.

The resin to be contained in the pores of the porous magnetic particles may be the copolymer resin used in the coating resin layer, but is not limited to this and any known resin may be used. As the thermoplastic resin, the copolymer used as the coating resin is preferable, but other examples include the following: polystyrene, polymethyl methacrylate, acrylic resin, methacrylic resin, styrene-acrylic acid ester copolymer, styrene-methacrylic acid ester copolymer, styrene-butadiene copolymer, ethylene-vinyl acetate copolymer, polyvinyl chloride, polyvinyl acetate, polyvinylidene fluoride, fluorocarbon resin, perfluorocarbon resin, solvent-soluble perfluorocarbon resin, polyvinylpyrrolidone, petroleum resin, novolac resin, saturated alkyl polyester, polyethylene terephthalate, polybutylene terephthalate, aromatic polyester such as polyarylate, polyamide, polyacetal, polycarbonate, polyethersulfone, polysulfone, polyphenylene sulfide, polyether ketone.

Examples of thermosetting resins include the following: phenolic resins, modified phenolic resins, maleic resins, alkyd resins, epoxy resins, acrylic resins, methacrylic resins, unsaturated polyesters obtained by polycondensation of maleic anhydride, terephthalic acid, and polyhydric alcohols, urea resins, melamine resins, urea-melamine resins, xylene resins, toluene resins, guanamine resins, melamine-guanamine resins, acetoguanamine resins, glyptal resins, furan resins, silicone resins, polyimides, polyamide-imides, polyether-imides, and polyurethanes.

When the magnetic core has a volumetric 50% (D50) of 20 μm or more and 80 μm or less, it is uniformly coated with the resin coating layer, which is preferable in terms of preventing carrier adhesion and achieving an appropriate density of the developer magnetic brush to obtain a high-quality image.
It is preferable that the specific resistance of the magnetic core is 1.0×10 ⁵ (Ω·cm) or more and 1.0×10 ¹⁴ (Ω·cm) or less at an electric field strength of 1000 (V/cm) since good developability can be obtained.

Next, the physical properties of the magnetic carrier and the magnetic carrier particles will be described.
The magnetic carrier preferably has a magnetization strength of 40 ( ^Am2 /kg) or more and 70 ( ^Am2 /kg) or less under a magnetic field of 5000/4π (kA/m). When the magnetization strength of the magnetic carrier is within the above range, the magnetic binding force to the developing sleeve is appropriate, so that the occurrence of carrier adhesion can be more effectively suppressed. In addition, the stress applied to the toner in the magnetic brush can be reduced, so that the deterioration of the toner and adhesion to other members can be effectively suppressed.

The strength of magnetization of the magnetic carrier can be appropriately adjusted by the amount of resin contained in the magnetic carrier particles. The residual magnetization of the magnetic carrier is preferably 20.0 ( ^Am2 /kg) or less, and more preferably 10.0 ( ^Am2 /kg) or less. When the residual magnetization of the magnetic carrier is within the above range, the developer has particularly good fluidity and good dot reproducibility.

The magnetic carrier preferably has a true density of 2.5 (g/ ^cm3 ) or more and 5.5 (g/ ^cm3 ) or less, and more preferably 3.0 (g/ ^cm3 ) or more and 5.0 (g/ ^cm3 ) or less. A two-component developer containing a magnetic carrier having a true density in this range places a small load on the toner, and adhesion of the toner components to the magnetic carrier is suppressed. In order to achieve both good developability at low electric field strength and prevention of carrier adhesion, a true density in this range is also preferable for the magnetic carrier.

From the viewpoints of the ability to charge the toner, suppression of carrier adhesion to the image area, and high image quality, it is preferable that the magnetic carrier has a volume-based 50% diameter (D50) of 21 μm or more and 81 μm or less. More preferably, it is 25 μm or more and 60 μm or less.

Next, the preferred toner constitution for achieving the object of the present invention will be described in detail below.
<Binder resin>
The toner particles may use, for example, the following polymers as the binder resin. Polymers of styrene and its substitutes, such as polystyrene, poly-p-chlorostyrene, and polyvinyltoluene; styrene-based copolymers, such as styrene-p-chlorostyrene copolymer, styrene-vinyltoluene copolymer, styrene-vinylnaphthalene copolymer, styrene-acrylic acid ester copolymer, and styrene-methacrylic acid ester copolymer; styrene-based copolymer resin, polyester, a mixture of polyester and a vinyl-based resin, or a hybrid resin in which both are partially reacted; polyvinyl chloride, phenolic resin, naturally modified phenolic resin, naturally modified maleic acid resin, acrylic resin, methacrylic resin, polyvinyl acetate, silicone resin, polyester, polyurethane, polyamide, furan resin, epoxy resin, xylene resin, polyethylene, and polypropylene. Among these, those containing polyester as the main component are preferred from the viewpoint of low-temperature fixability.

The monomers used for polyester include polyhydric alcohols (divalent or trivalent or higher alcohols), polycarboxylic acids (divalent or trivalent or higher carboxylic acids), their acid anhydrides or lower alkyl esters. Here, in order to create a branched polymer that exhibits "strain hardening," it is effective to partially crosslink the amorphous resin molecules, and for this purpose, it is preferable to use a polyfunctional compound with a valence of three or more. Therefore, it is preferable to include trivalent or higher carboxylic acids, their acid anhydrides or lower alkyl esters, and/or trivalent or higher alcohols as raw material monomers for polyester.

The following polyhydric alcohol monomers can be used for polyester:

（式中、Ｒはエチレンまたはプロピレン基であり、ｘおよびｙはそれぞれ０以上の整数であり、かつ、ｘ＋ｙの平均値は０以上１０以下である。）
式（Ｂ）で示されるジオール類；

（式（Ｂ）中、Ｒ’は－ＣＨ_２ＣＨ_２－、－ＣＨ_２－ＣＨ（ＣＨ_３）－、または－ＣＨ_２－Ｃ（ＣＨ_３）_２－であり、ｘ’およびｙ’はそれぞれ０以上の整数であり、ｘ’＋ｙ’の平均値は０以上１０以下である。） Examples of the dihydric alcohol component include ethylene glycol, propylene glycol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, diethylene glycol, triethylene glycol, 1,5-pentanediol, 1,6-hexanediol, neopentyl glycol, 2-ethyl-1,3-hexanediol, hydrogenated bisphenol A, and bisphenol represented by formula (A) and its derivatives.

(In the formula, R is an ethylene or propylene group, x and y are each an integer of 0 or more, and the average value of x+y is 0 or more and 10 or less.)
Diols represented by formula (B);

(In formula (B), R' is -CH ₂ CH ₂ -, -CH ₂ -CH(CH ₃ )-, or -CH ₂ -C(CH ₃ ) ₂ -, x' and y' are each an integer of 0 or more, and the average value of x' + y' is 0 or more and 10 or less.)

Examples of trihydric or higher alcohol components include sorbitol, 1,2,3,6-hexanetetrol, 1,4-sorbitan, pentaerythritol, dipentaerythritol, tripentaerythritol, 1,2,4-butanetriol, 1,2,5-pentanetriol, glycerol, 2-methylpropanetriol, 2-methyl-1,2,4-butanetriol, trimethylolethane, trimethylolpropane, and 1,3,5-trihydroxymethylbenzene. Of these, glycerol, trimethylolpropane, and pentaerythritol are preferably used. These dihydric alcohols and trihydric or higher alcohols can be used alone or in combination.

The following polycarboxylic acid monomers can be used for the polyester resin:

Examples of divalent carboxylic acid components include maleic acid, fumaric acid, citraconic acid, itaconic acid, glutaconic acid, phthalic acid, isophthalic acid, terephthalic acid, succinic acid, adipic acid, sebacic acid, azelaic acid, malonic acid, n-dodecenylsuccinic acid, isododecenylsuccinic acid, n-dodecylsuccinic acid, isododecylsuccinic acid, n-octenylsuccinic acid, n-octylsuccinic acid, isooctylsuccinic acid, isooctylsuccinic acid, anhydrides of these acids, and lower alkyl esters of these acids. Of these, maleic acid, fumaric acid, terephthalic acid, and n-dodecenylsuccinic acid are preferably used.

Examples of trivalent or higher carboxylic acids, their acid anhydrides or their lower alkyl esters include 1,2,4-benzenetricarboxylic acid, 2,5,7-naphthalenetricarboxylic acid, 1,2,4-naphthalenetricarboxylic acid, 1,2,4-butanetricarboxylic acid, 1,2,5-hexanetricarboxylic acid, 1,3-dicarboxyl-2-methyl-2-methylenecarboxypropane, 1,2,4-cyclohexanetricarboxylic acid, tetra(methylenecarboxyl)methane, 1,2,7,8-octanetetracarboxylic acid, pyromellitic acid, empol trimer acid, their acid anhydrides or their lower alkyl esters. Of these, 1,2,4-benzenetricarboxylic acid, i.e., trimellitic acid or its derivatives, is particularly preferred because it is inexpensive and the reaction is easy to control. These divalent carboxylic acids and trivalent or higher carboxylic acids can be used alone or in combination.

There is no particular restriction on the method for producing polyester, and known methods can be used. For example, the above-mentioned alcohol monomer and carboxylic acid monomer are charged at the same time, and polymerized through an esterification reaction or ester exchange reaction and a condensation reaction to produce polyester. The polymerization temperature is not particularly restricted, but is preferably in the range of 180°C to 290°C. For example, polymerization catalysts such as titanium-based catalysts, tin-based catalysts, zinc acetate, antimony trioxide, and germanium dioxide can be used when producing polyester. In particular, polyester polymerized using a tin-based catalyst is more preferred.

In addition, it is preferable from the viewpoint of fogging that the acid value of the polyester resin is 5 mgKOH/g or more and 20 mgKOH/g or less, and the hydroxyl value is 20 mgKOH/g or more and 70 mgKOH/g or less, since this reduces the amount of moisture adsorbed in a high-temperature, high-humidity environment and keeps the anti-electrostatic adhesion low.

The binder resin may be a mixture of low molecular weight resin and high molecular weight resin. From the viewpoint of low temperature fixability and hot offset resistance, it is preferable that the content ratio of high molecular weight resin to low molecular weight resin is 40/60 or more and 85/15 or less by mass.

<Release Agent>
Examples of waxes used in toner particles include the following: hydrocarbon waxes such as low molecular weight polyethylene, low molecular weight polypropylene, alkylene copolymers, microcrystalline wax, paraffin wax, and Fischer-Tropsch wax; oxides of hydrocarbon waxes such as oxidized polyethylene wax or block copolymers thereof; waxes containing fatty acid esters as the main component such as carnauba wax; and partially or completely deoxidized fatty acid esters such as deoxidized carnauba wax. Further examples include the following. Saturated straight-chain fatty acids such as palmitic acid, stearic acid, and montanic acid; unsaturated fatty acids such as brassidic acid, eleostearic acid, and valinaric acid; saturated alcohols such as stearyl alcohol, aralkyl alcohol, behenyl alcohol, carnaubyl alcohol, ceryl alcohol, and melissyl alcohol; polyhydric alcohols such as sorbitol; esters of fatty acids such as palmitic acid, stearic acid, behenic acid, and montanic acid and alcohols such as stearyl alcohol, aralkyl alcohol, behenyl alcohol, carnaubyl alcohol, ceryl alcohol, and melissyl alcohol; fatty acid amides such as linoleic acid amide, oleic acid amide, and lauric acid amide; methylene bisstearic acid amide, ethylene biscapric acid amide, ethylene bislauric acid amide, hexamethylene saturated fatty acid bisamides such as bisstearamide; unsaturated fatty acid amides such as ethylene bisoleamide, hexamethylene bisoleamide, N,N'-dioleyl adipamide, and N,N'-dioleyl sebacamide; aromatic bisamides such as m-xylene bisstearamide and N,N'-distearyl isophthalamide; aliphatic metal salts (commonly known as metal soaps) such as calcium stearate, calcium laurate, zinc stearate, and magnesium stearate; waxes obtained by grafting aliphatic hydrocarbon waxes with vinyl monomers such as styrene and acrylic acid; partial esters of fatty acids and polyhydric alcohols such as behenic acid monoglyceride; and methyl ester compounds having a hydroxyl group obtained by hydrogenating vegetable oils and fats.

Among these waxes, from the viewpoint of improving low-temperature fixing property and fixing separation property, preferred are hydrocarbon waxes such as paraffin wax and Fischer-Tropsch wax, and fatty acid ester waxes such as carnauba wax. In the present invention, hydrocarbon waxes are more preferred in terms of further improving hot offset resistance.

The content of the wax in the toner particles is preferably 3 parts by mass or more and 8 parts by mass or less per 100 parts by mass of the binder resin.
In addition, in an endothermic curve during temperature rise measured by a differential scanning calorimetry (DSC) device, the peak temperature of the maximum endothermic peak of the wax is preferably 45° C. or more and 140° C. or less. If the peak temperature of the maximum endothermic peak of the wax is within the above range, it is preferable because it is possible to achieve both storage stability and hot offset resistance of the toner.

<Coloring Agent>
The toner particles may contain a colorant. Examples of the colorant include the following:

Black colorants include carbon black, and those toned to black using yellow, magenta, and cyan colorants. As a colorant, a pigment may be used alone, but it is more preferable to use a dye and a pigment in combination to improve the clarity of the image in terms of the image quality of a full-color image.

Pigments for magenta toner include the following: C.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, 146, 147, 150, 163, 184, 202, 206, 207, 209, 238, 269, 282; C.I. Pigment Violet 19; C.I. Bat Red 1, 2, 10, 13, 15, 23, 29, 35.
Dyes for magenta toner 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. Disperse Red 9; C.I. Solvent Violet 8, 13, 14, 21, 27; C.I. Disperse Violet 1, and basic dyes such as C.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. Basic Violet 1, 3, 7, 10, 14, 15, 21, 25, 26, 27, 28.

Examples of pigments for cyan toner include C.I. Pigment Blue 2, 3, 15:2, 15:3, 15:4, 16, and 17; C.I. Bat Blue 6; C.I. Acid Blue 45; and copper phthalocyanine pigments having 1 to 5 phthalimidomethyl groups substituted on the phthalocyanine skeleton.
Dyes for cyan toner include C.I. Solvent Blue 70.

Yellow toner pigments include: C.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, 94, 95, 97, 109, 110, 111, 120, 127, 128, 129, 147, 151, 154, 155, 168, 174, 175, 176, 180, 181, 185; C.I. Vat Yellow 1, 3, 20.
Yellow toner dyes include C.I. Solvent Yellow 162.

These colorants can be used alone or in combination, or in the form of a solid solution. The colorant is selected in consideration of hue angle, chroma, brightness, light resistance, transparency on an OHP sheet, and dispersibility in a toner.
The content of the colorant is preferably 0.1 parts by mass or more and 30.0 parts by mass or less based on the total amount of the resin components.

<Inorganic fine particles>
The toner preferably contains inorganic fine particles for the main purpose of improving fluidity and chargeability, and the inorganic fine particles are preferably attached to the toner surface.
As inorganic fine particles serving as spacer particles for improving the releasability between the toner and the magnetic carrier, silica particles having a maximum peak particle size based on the number distribution of 80 nm to 200 nm are preferred, and in order to function as spacer particles while better suppressing detachment from the toner, a particle size of 100 nm to 150 nm is more preferred.
In order to improve the fluidity of the toner, it is preferable to contain inorganic fine particles having a maximum peak particle size based on the number distribution of 20 nm to 50 nm, and it is also preferable to use them in combination with silica particles.

Furthermore, other external additives may be added to the toner particles in order to improve fluidity and transferability. The external additives added to the surface of the toner particles preferably contain inorganic fine particles such as titanium oxide, alumina oxide, and silica, and multiple types may be used in combination.

The total content of the external additives is preferably 0.3 parts by mass or more and 5.0 parts by mass or less, and more preferably 0.8 parts by mass or more and 4.0 parts by mass or less, relative to 100 parts by mass of the toner particles. Among these, the content of silica particles having a maximum peak particle size of 80 nm to 200 nm based on the number distribution standard is 0.1 parts by mass or more and 2.5 parts by mass or less, and more preferably 0.5 parts by mass or more and 2.0 parts by mass or less. If it is within this range, the effect as a spacer particle will be more pronounced.

In addition, the surfaces of silica particles and inorganic fine particles used as external additives are preferably subjected to a hydrophobic treatment. The hydrophobic treatment is preferably performed using coupling agents such as various titanium coupling agents and silane coupling agents; fatty acids and their metal salts; silicone oil; or a combination thereof.

Examples of titanium coupling agents include the following: tetrabutyl titanate, tetraoctyl titanate, isopropyl triisostearoyl titanate, isopropyl tridecylbenzenesulfonyl titanate, and bis(dioctyl pyrophosphate)oxyacetate titanate.

Examples of silane coupling agents include the following: γ-(2-aminoethyl)aminopropyltrimethoxysilane, γ-(2-aminoethyl)aminopropylmethyldimethoxysilane, γ-methacryloxypropyltrimethoxysilane, N-β-(N-vinylbenzylaminoethyl)γ-aminopropyltrimethoxysilane hydrochloride, hexamethyldisilazane, methyltrimethoxysilane, butyltrimethoxysilane, isobutyltrimethoxysilane, hexyltrimethoxysilane, octyltrimethoxysilane, decyltrimethoxysilane, dodecyltrimethoxysilane, phenyltrimethoxysilane, o-methylphenyltrimethoxysilane, and p-methylphenyltrimethoxysilane.

Examples of fatty acids include the following: long-chain fatty acids such as undecylic acid, lauric acid, tridecylic acid, dodecylic acid, myristic acid, palmitic acid, pentadecylic acid, stearic acid, heptadecylic acid, arachidic acid, montanic acid, oleic acid, linoleic acid, and arachidonic acid. Examples of metals in the metal salts of these fatty acids include zinc, iron, magnesium, aluminum, calcium, sodium, and lithium.

Examples of silicone oils include dimethyl silicone oil, methylphenyl silicone oil, and amino-modified silicone oil.

The hydrophobic treatment is preferably carried out by adding a hydrophobic treatment agent to the treated particles in an amount of 1% by mass or more and 30% by mass or less (more preferably 3% by mass or more and 7% by mass or less) relative to the treated particles to coat the treated particles.
The degree of hydrophobization of the external additive that has been subjected to the hydrophobization treatment is not particularly limited, but for example, the degree of hydrophobization after the treatment is preferably from 40 to 98. The degree of hydrophobization indicates the wettability of a sample with respect to methanol, and is an index of hydrophobicity.

<Two-component developer>
When the magnetic carrier of the present invention is mixed with a toner to be used as a two-component developer, the toner concentration in the two-component developer is preferably 2% by mass or more and 15% by mass or less, more preferably 4% by mass or more and 13% by mass or less. When the toner concentration is within the above range, a good image can be obtained. When the toner concentration is less than 2% by mass, the image density is likely to decrease, and when it exceeds 15% by mass, fogging and scattering in the machine are likely to occur.

<Replenishing Developer>
The replenishment developer is a developer that is replenished when the toner concentration in the developing device decreases due to the consumption of toner during image formation. A predetermined amount of two-component developer containing a predetermined ratio of toner and carrier is contained in the developing container at the time of shipment, but the toner is consumed during image formation and the toner concentration in the developing container decreases. Therefore, replenishment developer containing toner is supplied to the developing container according to the toner concentration in the developing container. The replenishment developer contains 2 parts by mass or more and 50 parts by mass or less of toner per 1 part by mass of magnetic carrier.

Next, we will explain an example of an image forming apparatus equipped with a developing device that uses a two-component developer and a replenishment developer, but the developing device used in the development method of the present invention is not limited to this.

<Image forming method>
As shown in FIG. 1, the electrostatic latent image carrier 1 rotates in the direction of the arrow. The electrostatic latent image carrier 1 is charged by a charger 2, which is a charging means, and the surface of the charged electrostatic latent image carrier 1 is exposed by an exposure device 3, which is an electrostatic latent image forming means, to form an electrostatic latent image. In the developing device 4, a developing container 5 containing a two-component developer and a developer carrier 6 are arranged in a rotatable state, and the developer carrier 6 contains a magnet 7 as a magnetic field generating means inside. 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, and the amount of the two-component developer is regulated by a regulating member 8, and the developer is transported to a developing section facing the electrostatic latent image carrier 1. In the developing section, the magnetic field generated by the magnet 7 forms a magnetic brush. Thereafter, a developing bias consisting of an alternating electric field superimposed on a direct current electric field is applied, and the electrostatic latent image is visualized as a toner image. The toner image formed on the electrostatic latent image carrier 1 is electrostatically transferred to a recording medium (transfer material) 12 by a transfer charger 11. Here, as shown in FIG. 2, the toner image may be once transferred from the electrostatic latent image carrier 1 to an intermediate transfer body 9, and then electrostatically transferred to the recording medium 12.

The recording medium 12 is then transported to the fixing device 13, where it is heated and pressurized to fix the toner onto the recording medium 12. The recording medium 12 is then discharged outside the device as an output image. After the transfer process, any toner remaining on the electrostatic latent image carrier 1 is removed by the cleaner 15. The electrostatic latent image carrier 1, which has been cleaned by the cleaner 15, is then electrically initialized by light irradiation from the pre-exposure device 16, and the above image formation operation is repeated.

FIG. 2 is a schematic diagram showing an example of an image forming method using a full-color image forming apparatus.
The arrangement of the image forming units such as K, Y, C, and M in FIG. 2 and the arrows indicating the rotation direction are not limited to those shown. 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, and 1M rotate in the direction of the arrow. Each electrostatic latent image carrier is charged by the chargers 2K, 2Y, 2C, and 2M, which are charging means, and the surface of each charged electrostatic latent image carrier is exposed by the exposure devices 3K, 3Y, 3C, and 3M, which are electrostatic latent image forming means, to form an electrostatic latent image. Thereafter, the electrostatic latent image is visualized as a toner image by the two-component developer carried on the developer carriers 6K, 6Y, 6C, and 6M provided in the developing devices 4K, 4Y, 4C, and 4M, which are developing means. Furthermore, the toner image is transferred to the intermediate transfer body 9 by the intermediate transfer chargers 10K, 10Y, 10C, and 10M, which are transfer means. Furthermore, the toner image is transferred to a recording medium 12 by a transfer charger 11, which is a transfer means, and the recording medium 12 is heated and pressure fixed by a fixing device 13, which is a fixing means, and the toner image is output as an image. An intermediate transfer body cleaner 14, which is a cleaning member for the intermediate transfer body 9, collects the transfer residual toner and the like. As a development method, it is preferable to apply an AC voltage to the developer carrier 6 to form an alternating electric field in the development area, and perform development in a state where the magnetic brush is in contact with the electrostatic latent image carrier 1. The distance (SD distance) between the developer carrier (developing sleeve) 6 and the electrostatic latent image carrier 1 is preferably 100 μm or more and 1000 μm or less in order to prevent magnetic carrier adhesion and improve dot reproducibility. If it is narrower than 100 μm, the supply of developer is likely to be insufficient, resulting in a low image density. If it exceeds 1000 μm, the magnetic field lines from the magnetic pole S1 will spread, the density of the magnetic brush will decrease, dot reproducibility will deteriorate, and the force binding the magnetic coated carrier will weaken, making carrier adhesion more likely to occur.

The peak-to-peak voltage (Vpp) of the alternating electric field is 300V or more and 3000V or less, preferably 500V or more and 1800V or less. The frequency of the alternating electric field is 500Hz or more and 10000Hz or less, preferably 1000Hz or more and 7000Hz or less. The peak-to-peak voltage and frequency of the alternating electric field can be appropriately selected and used depending on the process. Examples of the waveform of the AC bias for forming the alternating electric field include a triangular wave, a rectangular wave, a sine wave, or a waveform with a changed duty ratio. In order to respond to changes in the toner image formation speed, it is preferable to apply a development bias voltage (intermittent AC superimposed voltage) having a discontinuous AC bias voltage to the developer carrier for development. If the applied voltage of the development bias voltage is lower than 300V, it is difficult to obtain a sufficient image density, and the fog toner in the non-image area may not be collected well. If it exceeds 3000V, the electrostatic latent image may be disturbed through the magnetic brush, resulting in a decrease in image quality.

By using a two-component developer with a well-charged toner, the fog removal voltage (Vback) can be lowered, and the primary charge of the electrostatic latent image carrier can be lowered, thereby extending the life of the electrostatic latent image carrier. Vback depends on the development system, but is preferably 200V or less, more preferably 150V or less. A contrast potential of 100V or more and 400V or less is preferably used to produce sufficient image density.

Furthermore, if the frequency is lower than 500 Hz, the process speed is also affected, but the configuration of the electrostatic latent image bearing photoconductor may be the same as that of a photoconductor used in an image forming apparatus, for example, an electrostatic latent image bearing member having a conductive layer, an undercoat layer, a charge generating layer, a charge transport layer, and optionally a charge injection layer, provided in this order on a conductive substrate such as aluminum or SUS.
The conductive layer, undercoat layer, charge generating layer and charge transport layer may be the same as those used in the photoreceptor for the image forming apparatus. As the outermost layer of the electrostatic latent image bearing member, for example, a charge injection layer or a protective layer may be used.

The flow of developer in an image forming apparatus using replenishment developer will be described with reference to FIG. 3. The toner (shown by a black circle in FIG. 3) in the developing device 102 is consumed when the electrostatic latent image on the photoconductor is developed with toner. When the toner concentration detection sensor 105 detects that the toner in the developing device 102 is low, replenishment developer is supplied to the developing device 102 from the replenishment developer storage container 101. Excess magnetic carrier (shown by a white circle in FIG. 3) in the developing device 102 is moved to the developer recovery container 104 via the discharge device 106. The developer recovery container 104 may also recover toner recovered by the cleaning device 103.

<Method of measuring volume-based 50% diameter (D50) of magnetic carrier and magnetic core>
The particle size distribution is measured, for example, using a laser diffraction/scattering type particle size distribution measuring device (product name: Microtrac MT3300EX, manufactured by Nikkiso Co., Ltd.).
The 50% diameter (D50) based on volume of the magnetic carrier and magnetic core was measured using a sample feeder for dry measurement (product name: One-shot dry type sample conditioner Turbotrac, manufactured by Nikkiso Co., Ltd.). The supply conditions for the Turbotrac were a dust collector used as a vacuum source, with an air volume of about 33 l/sec and a pressure of about 17 kPa. Control was performed automatically on the software. The particle size was calculated as the 50% particle size (D50), which is the cumulative value of the volume average. Control and analysis were performed using the attached software (version 10.3.3-202D). The measurement conditions were as follows:
SetZero time: 10 seconds Measurement time: 10 seconds Number of measurements: 1 Particle refractive index: 1.81%
Particle shape: non-spherical Upper measurement limit: 1408μm
Measurement lower limit: 0.243μm
Measurement environment: 23°C, 50% RH

<Measurement of pore diameter and pore volume of porous magnetic core>
The pore size distribution of the porous magnetic core is measured by mercury intrusion porosimetry.
The measurement principle is as follows.
In this measurement, the pressure applied to the mercury is changed, and the amount of mercury that penetrates into the pores at that time is measured. The conditions under which mercury can penetrate into the pores can be expressed from the balance of forces as PD = -4σ cos θ, where P is the pressure, D is the pore diameter, and θ and σ are the contact angle and surface tension of the mercury, respectively. If the contact angle and surface tension are constants, then the pressure P and the pore diameter D into which mercury can penetrate at that time are inversely proportional. For this reason, the horizontal axis P of the P-V curve, which is obtained by measuring the pressure P and the amount of infiltrated liquid V at that time while changing the pressure, is directly substituted into the pore diameter from this formula to obtain the pore distribution.
As a measuring device, for example, a fully automatic multi-function mercury porosimeter PoreMaster series or PoreMaster-GT series manufactured by Yuasa Ionics Co., Ltd., or an automatic porosimeter Autopore IV 9500 series manufactured by Shimadzu Corporation can be used for the measurement.

Specifically, the measurement was performed using an Autopore IV9520 manufactured by Shimadzu Corporation under the following conditions and procedures.
Measurement conditions Measurement environment 20℃
Measurement cell: sample volume 5 cm ³ , indentation volume 1.1 cm ³ , application: powder Measurement range: 2.0 psia (13.8 kPa) to 59989.6 psia (413.7 kPa) Measurement steps: 80 steps
(The steps are spaced equally apart when the pore diameter is taken logarithmically.)
Pressurization parameters: Exhaust pressure 50 μmHg
Exhaust time: 5.0 min
Mercury injection pressure: 2.0 psia (13.8 kPa)
Equilibration time: 5 sec
High pressure parameters Equilibration time 5sec
Mercury parameters Advancing contact angle 130.0 degrees
Receding contact angle 130.0 degrees
Surface tension 485.0mN/m (485.0dynes/cm)
Mercury density 13.5335g/mL

Measurement Procedure (1) Approximately 1.0 g of the porous magnetic core is weighed and placed in the sample cell.
Enter the weighing value.
(2) In the low pressure section, the pressure range is measured from 2.0 psia (13.8 kPa) to 45.8 psia (315.6 kPa).
(3) In the high pressure section, the range of 45.9 psia (316.3 kPa) or more and 59,989.6 psia (413.6 MPa) or less was measured.
(4) The pore size distribution is calculated from the mercury injection pressure and the amount of mercury injected.
(2), (3), and (4) were carried out automatically using the software provided with the device.
From the pore size distribution measured as described above, the pore size at which the differential pore volume is maximum in the pore size range of 0.1 μm or more and 3.0 μm or less is read, and this is taken as the pore size at which the differential pore volume is maximum.
In addition, the pore volume obtained by integrating the differential pore volume in the pore diameter range of 0.1 μm to 3.0 μm was calculated using the attached software.

<Method of measuring weight average particle size (D4)>
The weight average particle diameter (D4) of the toner was measured using a precision particle size distribution measuring device using a pore electrical resistance method equipped with a 100 μm aperture tube (product name: Coulter Counter Multisizer 3 (registered trademark), manufactured by Beckman Coulter, Inc.) and accompanying dedicated software for setting measurement conditions and analyzing measurement data (product name: Beckman Coulter Multisizer 3 Version 3.51, manufactured by Beckman Coulter, Inc.). Measurement was performed with an effective measurement channel count of 25,000 channels, and the measurement data was analyzed and calculated.
The aqueous electrolyte solution used for the measurement is prepared by dissolving special grade sodium chloride in ion-exchanged water to a concentration of about 1 mass %, for example, "ISOTON II" (manufactured by Beckman Coulter, Inc.).

Before performing the measurements and analysis, the dedicated software was set up as follows.
In the "Change Standard Measurement Method (SOM) Screen" of the dedicated software, set the total count number in the control mode to 50,000 particles, the number of measurements to 1, and the Kd value to the value obtained using "Standard Particle 10.0 μm" (manufactured by Beckman Coulter). Press the threshold/noise level measurement button to automatically set the threshold and noise level. Also, set the current to 1600 μA, the gain to 2, the electrolyte to ISOTON II, and check the aperture tube flush after measurement.
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 bins, and the particle size range is set to 2 μm to 60 μm.

The specific measurement method is as follows.
(1) Pour about 200 ml of the electrolyte solution into a 250 ml round-bottom glass beaker for use with the Multisizer 3, set it on the sample stand, and stir the stirrer rod counterclockwise at 24 revolutions per second. Then, remove dirt and air bubbles from inside the aperture tube using the "aperture flush" function of the analysis software.
(2) About 30 ml of the aqueous electrolyte solution is placed in a 100 ml flat-bottom glass beaker, and about 0.3 ml of a dilution of "Contaminon N" (a 10% aqueous solution of a neutral detergent for cleaning precision measuring instruments, pH 7, made of a nonionic surfactant, an anionic surfactant, and an organic builder, manufactured by Wako Pure Chemical Industries, Ltd.) diluted 3 times by mass with ion-exchanged water is added thereto as a dispersant.
(3) A predetermined amount of ion-exchanged water is placed in the water tank of an ultrasonic disperser "Ultrasonic Dispersion System Tetorara 150" (manufactured by Nikkaki Bios Co., Ltd.) that has two built-in oscillators with an oscillation frequency of 50 kHz and a phase shift of 180 degrees and an electric output of 120 W. About 2 ml of the above-mentioned Contaminon N is added to this water tank.
(4) The beaker of (2) is set in the beaker fixing hole of the ultrasonic disperser, and the ultrasonic disperser is operated. Then, the height position of the beaker is adjusted so that the resonance state of the liquid surface of the electrolytic solution in the beaker is maximized.
(5) In a state where the electrolyte solution in the beaker in (4) is irradiated with ultrasonic waves, about 10 mg of toner is added little by little to the electrolyte solution and dispersed. Then, ultrasonic dispersion treatment is continued for another 60 seconds. During ultrasonic dispersion, the water temperature in the water tank is appropriately adjusted so as to be 10°C or higher and 40°C or lower.
(6) Using a pipette, the electrolyte aqueous solution (5) in which the toner is dispersed is dropped into the round-bottom beaker (1) placed in the sample stand, and the measurement concentration is adjusted to about 5%. Then, the measurement is continued until the number of particles measured reaches 50,000.
(7) The measurement data is analyzed using the dedicated software that comes with the device, and the weight-average particle size (D4) is calculated. Note that when the dedicated software is set to Graph/Volume %, the "Average diameter" on the Analysis/Volume Statistics (Arithmetic Mean) screen is the weight-average particle size (D4).

<Powder X-ray diffraction analysis>
The XRD pattern was measured using an X-ray diffraction analyzer (X'pert PRO-MPD: manufactured by PANalytical).
X-rays were generated at an acceleration voltage of 45 kV and a current of 40 mA.
The powder X-ray measurement conditions are:
Divergence slit: 1/4 rad (fixed)
Anti-scattering slit: 1/2 rad
Solar slit: 0.04 rad
Mask: 15mm
Anti-scatter slit: 7.5 mm
Spinner: Yes Measurement method Scan axis: Continuous 2θ/θ
Measurement range: 5.0≦2θ≦80°
Step interval: 0.026 deg/s
Scan speed: 0.525 deg/s
Measurements were performed.
The sample used for measuring P70 is made using the same formulation as the porous ferrite core material, but by changing the oxygen concentration in the sintering process during production, the magnetization strength when an external magnetic field of 5000/4π (kA/m) is applied is adjusted to 70 ^Am2 /kg.

<Method for measuring the magnetization strength of a magnetic core>
The magnetization strength of the magnetic core can be measured by a vibrating sample magnetometer or a direct current magnetization characteristic recorder (BH tracer). In the examples described below, the magnetization strength is measured by a vibrating sample magnetometer BHV-30 (manufactured by Riken Denshi Co., Ltd.) according to the following procedure.
A cylindrical plastic container is filled with magnetic cores sufficiently densely to prepare a sample. The actual mass of the sample packed in the container is measured. After that, the sample is attached in the plastic container with instant adhesive so that it does not move.
Using a standard sample, the external magnetic field axis and the magnetization moment axis are calibrated at 5000/4π (kA/m).
The magnetization intensity was measured from the loop of the magnetization moment when an external magnetic field of 5000/4π (kA/m) was applied at a sweep speed of 5 (min/loop). The magnetization intensity ( ^Am2 /kg) of the magnetic core was calculated by dividing the measured value by the weight of the sample.

<Method for measuring surface functional group concentration>
- Method for calculating fluorine value by XPS measurement 10 mg of fine particles or carrier particles (hereinafter simply referred to as "particles" in "Method for calculating fluorine value by XPS measurement" and "Method for measuring the specific surface area of fine particles and carrier particles") are attached onto an indium foil. The particles are attached evenly so that the indium foil is not exposed. 1.0 ml of 2,2,2-trifluoroethanol is dropped into a 30 ml screw tube bottle to saturate the system with steam. The particles together with the indium foil are placed into the system and left exposed to the 2,2,2-trifluoroethanol atmosphere for 12 hours. At this time, care is taken to ensure that the particles do not directly adhere to the 2,2,2-trifluoroethanol liquid.
Next, 1.0 ml of trifluoroacetic anhydride is dropped into a 30 ml screw tube to saturate the system with vapor, and the particles together with the indium foil are placed in the system, and the particles are left exposed to the trifluoroacetic anhydride atmosphere for 12 hours.
The particles together with the indium foil were removed from the system and left for 6 hours in a dryer under reduced pressure at a set temperature of 25° C. When the obtained particles were subjected to XPS analysis, an XPS peak of fluorine derived from 2,2,2-trifluoroethyl ester was detected.

Regarding the measurement device and measurement conditions, the surface functional group concentration can be determined, for example, using the following measurement device and measurement conditions.
Equipment: PHI5000VERSAPROBEII (ULVAC-PHI, Inc.)
Irradiation line: Al Kd line Output: 25W 15kV
Pass Energy: 29.35eV
Step size: 0.125eV
XPS peak (P2): C _1S (CB), Ti _2P (TiO ₂ , SrTiO ₂ ), Al _2P (Al ₂ O ₃ ), Mg _2P (MgO), Zn _2P3/2 (ZnO), Si _2P (SiO ₂ )

-Method of Measuring Specific Surface Area of Fine Particles and Carrier Particles The BET specific surface area is measured using a specific surface area measuring device (product name: Tristar 3000, manufactured by Shimadzu Corporation).
The specific surface area of the particles is calculated by adsorbing nitrogen gas onto the surface of the sample according to the BET method and using the BET multipoint method. Before measuring the specific surface area, about 2 g of the sample is weighed out in a sample tube and evacuated at room temperature for 24 hours. After evacuating, the mass of the entire sample cell is measured and the exact mass of the sample is calculated from the difference with the mass of an empty sample cell.
An empty sample cell is set in the balance port and analysis port of the BET measurement device. Next, a Dewar bottle containing liquid nitrogen is set in a specified position, and saturated vapor pressure (P0) is measured using the P0 measurement command. After the P0 measurement is completed, the prepared sample cell is set in the analysis port, and after inputting the sample mass and P0, measurement is started using the BET measurement command. The BET specific surface area is then calculated automatically.
(Surface functional group concentration of particle)=(fluorine value measured by X-ray photoelectron spectroscopy/g)÷(specific surface area of particle/g)

<Method of Measuring Si Atomic Concentration by XPS Measurement>
As in the above "Method for calculating fluorine value by XPS measurement," carrier particles are attached evenly onto an indium foil so that the indium foil portion is not exposed.
The Si atomic concentration can be determined, for example, using the following measuring device and conditions:
Equipment: PHI5000VERSAPROBEII (ULVAC-PHI, Inc.)
Irradiation line: Al Kd line Output: 25W 15kV
Pass Energy: 58.7eV
Step size: 0.125eV
XPS peaks: C1s, O1s, Si2p, Ti2p, Sr3d

<Method of Manufacturing Magnetic Carrier>
Any magnetic core may be used as the magnetic core of the magnetic carrier particle, but a method for producing porous magnetic particles and magnetic material-dispersed resin particles as the magnetic core will be described below.

(Method of manufacturing magnetic material-dispersed resin particles)
The following methods are exemplary manufacturing methods for magnetic material-dispersed resin particles. For example, submicron magnetic materials such as iron powder, magnetite particles, and ferrite particles are kneaded so as to disperse them in a thermoplastic resin, pulverized to the particle size of the desired magnetic core, and thermally or mechanically spheroidized as necessary to obtain the magnetic material. It is also possible to manufacture the magnetic material by dispersing the submicron magnetic material in a monomer of a resin and polymerizing the monomer to form a resin. In this case, examples of the thermoplastic resin include resins such as vinyl resin, polyester, epoxy resin, phenol resin, urea resin, polyurethane, polyimide, cellulose resin, silicone resin, acrylic resin, and polyether. The resin may be one type or a mixed resin containing two or more types of resin. In particular, phenol resin is preferable in terms of increasing the strength of the magnetic core. The true density and resistivity can be adjusted by adjusting the amount of the magnetic material. Specifically, in the case of magnetic particles, it is preferable to add 70% by mass or more to 95% by mass or less to the carrier.

(Method of manufacturing porous magnetic particles)
The manufacturing process when ferrite is used as the porous magnetic carrier particles will be described in detail below.

<Step 1 (weighing and mixing step)>
The raw materials for the ferrite are weighed and mixed.
Examples of raw materials for ferrite include metal particles of the above-mentioned metal elements, or oxides, hydroxides, oxalates, carbonates, and the like thereof.
Examples of mixing devices include a ball mill, a planetary mill, a Giotto mill, a vibration mill, etc. Among these, a ball mill is preferred from the viewpoint of mixability.
For example, weighed ferrite raw material and balls are placed in a ball mill, and the mixture is pulverized and mixed for a period of 0.1 to 20.0 hours.

<Step 2 (Pre-firing step)>
The crushed and mixed ferrite raw material is calcined in air or nitrogen atmosphere at a calcination temperature in the range of 700° C. to 1200° C. for 0.5 to 5.0 hours to obtain the calcined ferrite. For the calcination, a calcination furnace such as a burner type calcination furnace, a rotary type calcination furnace, or an electric furnace can be used.

<Step 3 (pulverization step)>
The calcined ferrite obtained in step 2 is pulverized in a pulverizer.
Examples of the pulverizer include a crusher, a hammer mill, a ball mill, a bead mill, a planetary mill, and a Giotto mill.
In order to obtain a pulverized ferrite product with a desired particle size, for example, when using a ball mill or a bead mill, it is preferable to control the material of the balls and beads used, the particle size, and the pulverization time. Specifically, in order to reduce the particle size of the calcined ferrite slurry, balls with a heavy specific gravity can be used and the pulverization time can be extended. In addition, in order to widen the particle size distribution of the calcined ferrite, balls or beads with a heavy specific gravity can be used and the pulverization time can be shortened. In addition, calcined ferrite with a wide particle size distribution can be obtained by mixing multiple calcined ferrites with different particle sizes.
Furthermore, when using a ball mill or a bead mill, a wet type is more preferable than a dry type, since the pulverized product does not fly up in the mill and pulverization efficiency is increased.

<Step 4 (granulation step)>
To the pulverized calcined ferrite, water, a binder resin, and, if necessary, a pore adjusting agent, such as a foaming agent or resin particles, are added.
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 fine particles of polyester, polystyrene, styrene-vinyltoluene copolymer, styrene-vinylnaphthalene copolymer, styrene-acrylic acid ester copolymer, styrene-methacrylic acid ester copolymer, styrene-α-methyl chloromethacrylate copolymer, styrene-acrylonitrile copolymer, styrene-vinyl methyl ketone copolymer, styrene-butadiene copolymer, styrene-isoprene copolymer, and styrene-acrylonitrile-indene copolymer; polyvinyl chloride, phenol resin, modified phenol resin, maleic resin, acrylic resin, methacrylic resin, polyvinyl acetate, and silicone resin; polyester resin having a monomer selected from aliphatic polyhydric alcohols, aliphatic dicarboxylic acids, aromatic dicarboxylic acids, aromatic dialcohols, and diphenols as a structural unit; polyurethane, polyamide, polyvinyl butyral, terpene resin, coumarone-indene resin, petroleum resin, and hybrid resin having a polyester portion and a vinyl polymer portion.
An example of the binder resin is polyvinyl alcohol.
In step 3, when wet pulverization is performed, it is preferable to add a binder resin and, if necessary, a pore adjuster, taking into consideration the water contained in the ferrite slurry.
The obtained ferrite slurry is dried and granulated in a heated atmosphere of 100° C. to 200° C. using a spray dryer to obtain a granulated product. Examples of the spray dryer include a spray drier.

<Step 5 (Main Firing Step)>
The granulated product is fired at a temperature in the range of 800° C. to 1400° C. for 1 hour to 24 hours.
By increasing the sintering temperature and lengthening the sintering time, the sintering of the porous magnetic particles progresses, resulting in a smaller pore size and a reduced number of pores.

<Step 6 (sorting step)>
After the particles obtained by firing as described above are crushed, they may be classified or sieved to remove coarse particles and fine particles, if necessary.
The volume distribution based 50% particle size (D50) of the porous magnetic particles is preferably 20 μm or more and 80 μm or less from the viewpoint of suppressing adhesion of the carrier to the image and suppressing roughness of the image.

<Process 7 (filling process)>
The physical strength of the porous magnetic particles may be reduced depending on the internal pore volume. From the viewpoint of increasing the physical strength as a magnetic carrier, it is preferable to fill at least a part of the pores of the porous magnetic particles with resin. The amount of resin filled in the porous magnetic particles is preferably 2 parts by mass or more and 15 parts by mass or less per 100 parts by mass of the porous magnetic particles. Only a part of the pores may be filled with resin, or only the pores near the surface of the porous magnetic particles may be filled with resin, leaving voids inside, or the pores may be completely filled with resin. However, it is preferable that the variation in the resin content of each magnetic core filled with resin is small.

Methods for filling the pores of porous magnetic particles with resin include, for example, impregnating the porous magnetic particles with a resin solution by a coating method such as dipping, spraying, brushing, or fluidized bed, and then volatilizing the solvent, etc. When filling with a thermosetting resin, after volatilizing the solvent, the temperature is raised to the curing temperature of the resin used to cause a curing reaction.
Another method for filling the pores of the porous magnetic particles with a resin is to dilute the resin in a solvent and add the diluted resin to the pores of the porous magnetic particles. The solvent used here may be any solvent that can dissolve the resin.
When a resin soluble in an organic solvent is used, examples of the organic solvent include toluene, xylene, cellosolve butyl acetate, methyl ethyl ketone, methyl isobutyl ketone, methanol, etc. When a water-soluble resin or an emulsion-type resin is used, water can be used as the solvent.

The amount of resin solids 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. If the amount of resin solids is 50% by mass or less, the viscosity of the resin solution does not become too high, and it becomes easier to uniformly penetrate the resin solution into the pores of the porous magnetic particles. In addition, if the amount of resin solids is 1% by mass or more, the decrease in the adhesive strength of the resin to the porous magnetic particles due to a small amount of resin is suppressed.

Examples of the resin to be filled into the pores of the porous magnetic particles include thermoplastic resins, thermosetting resins, etc. The resin to be filled into the pores is preferably one that has a high affinity for the porous magnetic particles, and when a resin with high affinity is used, the surfaces of the porous magnetic particles can also be covered with the resin at the same time as the resin is filled into the pores of the porous magnetic particles.
As the resin to be filled into the porous magnetic particles, the resins exemplified above as the resin to be contained in the pores of the porous magnetic particles can be used.

(Method of Manufacturing Magnetic Carrier Particles)
The magnetic carrier used in the present invention is obtained by coating the surface of a magnetic core with a resin to form a resin coating layer. The method of coating the surface of the magnetic core is not particularly limited, and can be performed by a known method. For example, there is a so-called immersion method in which the magnetic core and the coating resin solution are stirred while volatilizing the solvent, and the coating resin is coated on the magnetic core surface. Specific examples include a universal mixer (manufactured by Fuji Paudal Co., Ltd.) and a Nauta Mixer (manufactured by Hosokawa Micron Co., Ltd.). There is also a method in which the coating resin solution is sprayed from a spray nozzle while forming a fluidized bed, and the coating resin is coated on the magnetic core surface. Specific examples include a Spiracoater (manufactured by Okada Seiko Co., Ltd.) and a Spiraflow (manufactured by Freund Corporation). There is also a method in which the coating resin is applied to the magnetic core in the form of particles in a dry coating method. Specifically, examples of the processing methods include those using devices such as Hybridizer (manufactured by Nara Machinery Works), Mechanofusion (manufactured by Hosokawa Micron Corporation), Hyflex Gral (manufactured by Fukae Powtec), and Theta Composer (manufactured by Tokuju Machinery Works).

<Toner Manufacturing Method>
The method for producing the toner particles is not particularly limited, but a pulverization method is preferred.

The procedure for producing the toner by the pulverization method will be described below.
In the raw material mixing process, materials constituting the toner particles, such as a binder resin, a release agent, a colorant, a crystalline polyester, and other components such as a charge control agent as required, are weighed out in predetermined amounts, blended, and mixed. Examples of mixing devices include a double con mixer, a V-type mixer, a drum type mixer, a super mixer, a Henschel mixer, a Nauta mixer, and a Mechano Hybrid (manufactured by Nippon Coke and Engineering Co., Ltd.).
Next, the mixed materials are melt-kneaded to disperse the wax in the binder resin. In the melt-kneading process, a batch kneader such as a pressure kneader or a Banbury mixer, or a continuous kneader can be used, and single-screw or twin-screw extruders are mainstream due to their advantage of continuous production. For example, a KTK twin-screw extruder (manufactured by Kobe Steel, Ltd.), a TEM twin-screw extruder (manufactured by Toshiba Machine Co., Ltd.), a PCM kneader (manufactured by Ikegai Iron Works Co., Ltd.), a twin-screw extruder (manufactured by KCK Corporation), a Co-Kneader (manufactured by Buss Co., Ltd.), and Kneadex (manufactured by Nippon Coke and Engineering Co., Ltd.) can be mentioned. Furthermore, the resin composition obtained by melt-kneading may be rolled with a two-roller or the like, and cooled with water or the like in a cooling process.
The cooled resin composition is then pulverized to a desired particle size in a pulverization step, which involves coarse pulverization using a pulverizer such as a crusher, a hammer mill, or a feather mill, followed by further pulverization using a pulverizer such as a Cryptron System (manufactured by Kawasaki Heavy Industries, Ltd.), a Super Rotor (manufactured by Nisshin Engineering Co., Ltd.), a Turbo Mill (manufactured by Turbo Kogyo Co., Ltd.), or an air jet type pulverizer.
Thereafter, as necessary, the mixture is classified using a classifier or sieve such as an inertial classification type Elbow Jet (manufactured by Nittetsu Mining Co., Ltd.) or a centrifugal classification type Turboplex (manufactured by Hosokawa Micron Corporation), TSP Separator (manufactured by Hosokawa Micron Corporation), or Faculty (manufactured by Hosokawa Micron Corporation).

Thereafter, the toner particles are surface-treated by heating to increase the circularity of the toner particles. For example, the surface treatment can be performed by hot air using a surface treatment device shown in FIG.
The toner particles supplied in a fixed amount by the raw material fixed amount supply means 21 are introduced into an introduction pipe 23 installed on the central axis of a processing chamber 26 by compressed gas adjusted by a compressed gas adjustment means 22. The toner particles passing through the introduction pipe 23 are uniformly dispersed by a conical protruding member 24 provided in the center of the introduction pipe 23, and are introduced into eight supply pipes 25 that radiate out in eight directions, and are introduced from a powder particle supply port 34 into the processing chamber 26 where heat treatment is performed.
At this time, the flow of the toner particles supplied to the treatment chamber 26 is regulated by a regulating means 29 for regulating the flow of the toner particles provided in the treatment chamber 26. Therefore, the toner particles supplied to the treatment chamber 26 are heat-treated while swirling within the treatment chamber 26.
The hot air for heat-treating the supplied toner particles is supplied from the hot air inlet 31 of the hot air supplying means 27, and is introduced into the processing chamber 26 by spirally swirling the hot air with the swirling member 33. The configuration is such that the swirling member 33 for swirling the hot air has a plurality of blades, and the swirling of the hot air can be controlled by the number and angle of the blades. At this time, the approximately conical distributor 32 can reduce the bias of the swirling hot air. The hot air supplied into the processing chamber 26 preferably has a temperature of 100°C to 300°C at the outlet of the hot air supplying means 27. If the temperature at the outlet of the hot air supplying means 27 is within the above range, it is possible to uniformly spheronize the toner particles while preventing the toner particles from fusing or coalescing due to excessive heating.
The heat-treated toner particles are further cooled by cold air supplied from cold air supply means 28 (cold air supply means 28-1, cold air supply means 28-2 and cold air supply means 28-3), and the temperature supplied from cold air supply means 28 is preferably -20°C to 30°C. If the temperature of the cold air is within the above range, the heat-treated toner particles can be efficiently cooled, and the fusion and coalescence of the heat-treated toner particles can be prevented without impeding the uniform spheroidization treatment of the mixture. The absolute moisture content of the cold air is preferably 0.5 g/ ^m3 or more and 15.0 g/ ^m3 or less.

Next, the cooled heat-treated toner particles are collected by the collecting means 30 at the bottom end of the processing chamber 26. A blower (not shown) is provided ahead of the collecting means 30, so that the toner particles are sucked and transported by the blower.
The powder particle supply port 34 is provided so that the swirling direction of the supplied toner particles and the swirling direction of the hot air are the same, and the recovery means 30 of the surface treatment device is provided on the outer periphery of the treatment chamber 26 so as to maintain the swirling direction of the swirled toner particles. Furthermore, the cold air supplied from the cold air supply means 28 is configured to be supplied from the outer periphery of the device to the inner periphery of the treatment chamber 26 in a horizontal and tangential direction. The swirling direction of the toner supplied from the powder particle supply port 34, the swirling direction of the cold air supplied from the cold air supply means 28, and the swirling direction of the hot air supplied from the hot air supply means 27 are all the same. Therefore, no turbulence occurs in the treatment chamber 26, the swirling flow in the device is strengthened, a strong centrifugal force is applied to the toner particles, and the dispersibility of the toner particles is further improved, so that toner particles with a uniform shape and few coalesced particles can be obtained.
When the average circularity of the toner is 0.960 or more and 0.980 or less, the non-electrostatic adhesion can be suppressed to a low level, which is preferable from the viewpoint of fogging.

Thereafter, the fine powder side is divided into two parts, one for fine powder and the other for coarse powder. For example, the two parts are divided into two parts using an inertial classification system, Elbow Jet (manufactured by Nittetsu Mining Co., Ltd.). A desired amount of silica fine particles A is externally added to the surface of each of the two heat-treated toner particles. Examples of the method of externally adding the toner particles include a method of stirring and mixing using a mixing device such as a Double Con mixer, a V-type mixer, a drum type mixer, a Super mixer, a Henschel mixer, a Nauta mixer, a Mechano Hybrid (manufactured by Nippon Coke & Engineering Co., Ltd.), or a Nobilta (manufactured by Hosokawa Micron Corporation) as an external adder. In this case, an external additive other than silica fine particles, such as a fluidizing agent, may be externally added, if necessary.
The methods for measuring various physical properties of the toner and materials are described below.

The present invention will be explained below with reference to examples. However, the description of the examples does not limit the technical scope of the present invention.

<Manufacturing example of magnetic core 1>
Process 1 (weighing and mixing process)
Fe ₂ O ₃ 68.3% by mass
MnCO ₃ 28.5% by mass
Mg(OH) ₂ 2.0% by mass
SrCO ₃ 1.2% by mass
The above materials were weighed, 80 parts by mass of the materials were mixed with 20 parts by mass of water, and then wet-mixed in a ball mill using zirconia having a diameter (φ) of 10 mm for 3 hours to prepare a slurry. The solid content of the slurry was 80% by mass.

Step 2 (pre-firing step)
The mixed slurry was dried using a spray dryer (manufactured by Okawara Kakoki Co., Ltd.) and then fired in a batch-type electric furnace in a nitrogen atmosphere (oxygen concentration: 1.0% by volume) at a temperature of 1,050° C. for 3.0 hours to produce calcined ferrite.

Step 3 (Crushing step)
The calcined ferrite was coarsely crushed to about 0.5 mm using a crusher, and water was added to prepare a coarsely crushed slurry. The solid content of the coarsely crushed slurry was set to 70 mass%. The mixture was finely crushed for 3 hours using a wet ball mill with 1/8 inch stainless steel beads to obtain a finely crushed slurry. The finely crushed slurry was further crushed for 4 hours using a wet bead mill with zirconia having a diameter of 1 mm to obtain a calcined ferrite slurry with a volume-based 50% particle size (D50) of 1.3 μm.

Step 4 (granulation step)
To 100 parts by mass of the calcined ferrite slurry, 1.0 part by mass of ammonium polycarboxylate as a dispersant and 1.5 parts by mass of polyvinyl alcohol as a binder were added, and then the mixture was granulated into spherical particles and dried using a spray dryer (manufactured by Okawara Kakoki Co., Ltd.) The resulting granulated material was subjected to particle size adjustment, and then heated at 700° C. for 2 hours using a rotary electric furnace to remove organic substances such as the dispersant and binder.

Step 5 (firing step)
In a nitrogen atmosphere (oxygen concentration 1.0% by volume), the time from room temperature to the firing temperature (1100° C.) was set to 2 hours, and the temperature was held at 1100° C. for 4 hours, followed by firing in a tunnel-type electric furnace. Thereafter, the temperature was lowered to 60° C. over 8 hours, and the nitrogen atmosphere was returned to the air, and the mixture was taken out at a temperature of 40° C. or less.

Step 6 (sorting step)
After the agglomerated particles were crushed, the coarse particles were removed by sieving through a sieve with 150 μm openings, fine powder was removed by air classification, and low magnetic force particles were removed by magnetic separation to obtain a porous magnetic core 1.

<Production Example of Microparticle 1>
100 parts by mass of carbon black (product name: #4400, manufactured by Tokai Carbon Co., Ltd.) was placed in a 500 ml round-bottomed flask, and 200 parts by mass of an aqueous nitric acid solution (50% by mass) was added. A ball condenser was connected to the flask, and the round-bottom flask was placed on a mantle heater, and oxidation treatment was carried out for 30 minutes after refluxing began. After refluxing was completed, the carbon black was separated by filtration and dried in a dryer at 125°C to obtain microparticles 1 having a volume average particle size of 33 nm. Table 1 shows the physical properties of the obtained microparticles 1. In Table 1, "CB" stands for carbon black.

<Production Examples of Microparticles 2 to 6 and 8 to 13>
Fine particles 2 to 6 and 8 to 13 were obtained in the same manner as in the production example of fine particle 1, except that the fine particles and the type and amount of the treating agent were changed from those of fine particle 1. The physical properties of the obtained fine particles 2 to 6 and 8 to 13 are shown in Table 1.

<Production Example of Microparticle 7>
100 parts by mass of carbon black (#4400, manufactured by Tokai Carbon Co., Ltd.) was placed in a 500 ml round-bottomed flask, and 200 parts by mass of an aqueous nitric acid solution (50% by mass) was added. A ball condenser was connected to the flask, and the round-bottomed flask was placed on a mantle heater to start reflux and perform oxidation treatment for 30 minutes. Next, 200 parts by mass of methanol was added. After cooling with ice, 30 parts by mass of calcium carbonate was added, and the mixture was heated to 25°C and stirred for 2 hours. 100 parts by mass of a saturated aqueous ammonium chloride solution was added to the mixture obtained by stirring to stop the reaction, washed with water, air-dried, and dried under reduced pressure to obtain microparticles 7.

<Production Example of Silicone Modified Resin Solution 1>
95.2% by mass of a monomer corresponding to a unit represented by formula (7) shown in Table 2 and 4.8% by mass of a monomer corresponding to a unit represented by formula (8) shown in Table 2 were added to a four-neck flask equipped with a reflux condenser, a thermometer, a nitrogen suction tube, and a rotary stirrer.
Further, 100 parts by mass of toluene, 100 parts by mass of methyl ethyl ketone, and 2.0 parts by mass of azobisisovaleronitrile were added. The obtained mixture was stirred and held at 70° C. for 10 hours under a nitrogen stream, and after the polymerization reaction was completed, washing was repeated to obtain a silicone modified resin solution 1 having a solid content of 35% by mass. The l+m value of this solution calculated by gel permeation chromatography (GPC) was 70.

<Production Examples of Silicone Modified Resin Solutions 2 to 7>
Silicone-modified resin solutions 2 to 7 were obtained in the same manner as in Production Example of Silicone-modified Resin Solution 1, except that the mass of the unit represented by Formula (7) and the type of functional group in the unit represented by Formula (8), and the mass a of the unit represented by Formula (7) relative to the mass b of the unit represented by Formula (8) (a/b) were changed to those shown in Table 2. Note that the unit represented by Formula (8) used was the unit represented by the following Formula (8-1).

<Example of Macromonomer Production>
Methacrylic acid chloride 1.7% by mass
- Polymethyl methacrylate with a hydroxyl group at one end (Mw: about 5000)
98.3% by mass
The above materials were added to a four-neck flask equipped with a reflux condenser, a thermometer, a nitrogen suction tube, and a grinding stirrer. Furthermore, 100 parts by mass of THF and 1.0 parts by mass of 4-tert-butylcatechol were added to the four-neck flask. The resulting mixture was heated under reflux for 5 hours under a nitrogen stream, and after the reaction was completed, it was washed with sodium bicarbonate to obtain a macromonomer solution.

<Method of producing unmodified (meth)acrylic resin>
Cyclohexyl methacrylate 74.5% by mass
Methyl methacrylate 0.5% by mass
Methacrylic acid macromonomer produced above: 25% by mass
The above materials were added to a four-neck flask equipped with a reflux condenser, a thermometer, a nitrogen suction tube, and a grinding stirrer. In addition, 100 parts by mass of toluene, 100 parts by mass of methyl ethyl ketone, and 2.0 parts by mass of azobisisovaleronitrile were added to the four-neck flask. The resulting mixture was kept at 70° C. for 10 hours under a nitrogen stream, and after the polymerization reaction was completed, washing was repeated to obtain a solution of unmodified (meth)acrylic resin with a solid content of 35% by mass.

<Production Example of Magnetic Carrier 1>
(Resin coating process)
Using the magnetic core 1, a resin solution obtained by mixing silicone modified resin solution 1, microparticles 1, and unmodified (meth)acrylic resin was added to a planetary mixer (trade name: Nauta Mixer VN type, manufactured by Hosokawa Micron Corporation) maintained at a reduced pressure (1.5 kPa) and a temperature of 60° C., so that the resin component solid content was 2.0 parts by mass per 100 parts by mass of magnetic core 1. The resin solution was added by first adding 1/3 of the resin solution, removing the solvent for 20 minutes, and performing an operation so that the resin was applied to the surface of the magnetic core 1. Next, another 1/3 of the resin solution was added, and the solvent was removed and applied for 20 minutes. Then, 1/3 of the resin solution was added, and the solvent was removed and applied for 20 minutes.
The magnetic core 1 coated with the resin composition was transferred to a mixer (product name: drum mixer UD-AT type, manufactured by Sugiyama Heavy Industries Co., Ltd.) having a spiral blade in a rotatable mixing container. The mixture was heat-treated at a temperature of 120°C for 2 hours in a nitrogen atmosphere while stirring at 10 revolutions per minute. The obtained magnetic carrier particles were separated into low magnetic particles by magnetic separation, passed through a sieve with an opening of 150 μm, and then classified by a wind classifier. Magnetic carrier particles 1 having a 50% particle size (D50) based on volume distribution of 39.1 μm were obtained. The surface analysis results of the obtained magnetic carrier particles 1 (functional group concentration of the magnetic carrier particles and Si atom concentration on the surface of the magnetic carrier particles) are shown in Table 3. The magnetic carrier particles 1 were designated as magnetic carrier 1.

<Method of producing magnetic carriers 2 to 18 >
Magnetic Carriers 2 to 18 were obtained in the same manner as in the preparation of Magnetic Carrier 1, except that the silicone modified resin solution and the fine particles were changed to those shown in Table 3. The physical properties are shown in Table 3.

<Production Example of Toner 1>
Polyester resin 100 parts by mass Tg: 58°C
Acid value: 15mgKOH/g
Hydroxyl value: 15 mg KOH/g
Molecular weight: Mp5800, Mn3350, Mw94000
C.I. Pigment Blue 15:3 4.5 parts by mass 1,4-di-t-butylsalicylic acid aluminum compound 0.5 parts by mass Normal paraffin wax 6.0 parts by mass Melting point: 78°C
The above materials were thoroughly mixed in a Henschel mixer (product name: FM-75J type, manufactured by Nippon Coke & Engineering Co., Ltd.), and then mixed at a feed rate of 10 kg/h in a twin-axis mixer (product name: PCM-30 type, manufactured by Ikegai Co., Ltd. (formerly: Ikegai Steel Co., Ltd.)) set at a temperature of 130 ° C. (the temperature of the kneaded material at the time of discharge was about 150 ° C.). The resulting kneaded material was cooled, coarsely crushed with a hammer mill, and then finely crushed at a feed rate of 15 kg/h in a mechanical crusher (product name: T-250, manufactured by Freund Turbo Co., Ltd. (formerly: Turbo Kogyo Co., Ltd.)). Then, particles having a weight average particle size of 5.5 μm, containing 55.6% by number of particles having a particle size of 4.0 μm or less, and 0.8% by volume of particles having a particle size of 10.0 μm or more were obtained. In addition, "Tg" represents the glass transition temperature, "Mp" represents the peak molecular weight, "Mn" represents the number average molecular weight, and "Mw" represents the weight average molecular weight.
The obtained particles were classified by a rotary classifier (product name: TTSP100, manufactured by Hosokawa Micron Corp.) to remove fine powder and coarse powder, thereby obtaining toner particles 1 having a weight average particle size of 6.3 μm.
Strontium titanate particles (1.0 part) and hydrophobic silica fine particles (1.0 part) were added to the obtained toner particles 1 (100.0 parts). The obtained additives were mixed in a Henschel mixer (product name: FM75J type, manufactured by Mitsui Miike Chemical Engineering Co., Ltd.) at a rotation speed of 30 s ^-1 for a rotation time of 5 min, and passed through an ultrasonic vibration sieve with a mesh size of 54 μm to obtain toner 1. The weight average particle size (D4) of toner 1 was 6.5 μm, and the average circularity of the toner was 0.96.

<Production Examples of Two-Component Developers 1 to 18 >
Toner 1 and magnetic carriers 1 to 18 in the combinations shown in Table 4 were mixed in a V-type mixer (product name: V-10 type: manufactured by Tokuju Seisakusho Co., Ltd.) at 0.5 s ^-1 and a rotation time of 5 min so that the toner concentration became 8.0 mass %, to obtain two-component developers 1 to 18 .

<Production Examples of Replenishment Developers 1 to 18 >
Toner 1 was added in an amount of 90 parts by mass to magnetic carriers 1 to 18 in an amount of 10 parts by mass, and mixed for 5 minutes in a V-type mixer (product name: V-10 type, manufactured by Tokuju Seisakusho Co., Ltd.) in an environment of normal temperature and humidity of 23°C/50% RH to obtain replenishment developers 1 to 18 .

Example 1
Using the two-component developer 1 and the replenishment developer 1, the following evaluations were carried out.
As the image forming apparatus, a modified color copying machine (product name: imageRUNNER ADVANCE C5560, manufactured by Canon) was used.
Two-component developer 1 was placed in a cyan developing device, and a replenishment developer container containing replenishment developer 1 was set, and an image was formed, and various evaluations were performed before and after the durability test.
For durability testing, a chart with FFH output and an image ratio of 40% was used under a printing environment of 30°C temperature/80% RH (hereinafter referred to as "H/H"). FFH is a value that expresses 256 gradations in hexadecimal, with 00h being the first gradation (white background) of the 256 gradations and FFH being the 256th gradation (solid area) of the 256 gradations.

The number of images output was changed depending on each evaluation item.
conditions:
Paper: Laser beam printer paper CS-814 (81.4 g/m ² ) (Canon Marketing Japan Inc.)
The modifications to the color copier are as follows:
Image forming speed: Modified to be able to output 80 (sheets/min) in A4 size and full color.
In addition, color copiers,
The development contrast was made adjustable to any value, and the automatic correction by the main unit was not activated. The peak-to-peak voltage (Vpp) of the alternating electric field was modified to a frequency of 2.0 kHz, and Vpp was modified to be variable in 0.1 kV increments from 0.7 kV to 1.8 kV. The printer was modified to output images in a single color of cyan.
- The cyan developer was modified so that it could develop in a single color only.
- Idle rotation of the developer The sleeve speed of the developer in the main body can be freely changed and modified to allow it to spin freely.
The evaluation items are shown below.

[Evaluation 1. Fog evaluation]
After initial durability and durability image output evaluation (A4 landscape, 40% print ratio, 50,000 sheets) were performed under a high temperature and high humidity environment (30°C, 80% RH), an A4 full-page solid white image was output. Fog was measured by measuring the whiteness of the white background with a reflectometer (Tokyo Denshoku Co., Ltd.), and the fog density (%) was calculated from the difference in whiteness before and after transfer, and evaluated according to the following criteria. When the evaluation was A to C, it was determined that the effects of the present invention were obtained.
A: less than 1.0% B: 1.0% or more and less than 1.5% C: 1.5% or more and less than 2.0% D: 2.0% or more The evaluation results are shown in Table 4.

[Evaluation 2. Halftone developability evaluation]
After initial durability and durability image output evaluation (A4 landscape, 40% print ratio, 50,000 sheets) were performed in a high temperature and high humidity environment (30°C, 80% RH), a halftone image (30H) was printed on one A4 sheet, and the area of 1,000 dots was measured using a digital microscope VHX-500 (lens wide range zoom lens VH-Z100 manufactured by Keyence Corporation). The number average (S) of the dot area and the standard deviation (σ) of the dot area were calculated, and the dot reproducibility index was calculated using the following formula. Then, the roughness of the halftone image was evaluated using the dot reproducibility index (I).
Dot reproducibility index (I) = σ/S × 100

The roughness was evaluated according to the following criteria: When the evaluation was A to C, it was determined that the effect of the present invention was obtained.
A: I is less than 4.0 B: I is 4.0 or more and less than 5.0 C: I is 5.0 or more and less than 7.0 D: I is 7.0 or more The evaluation results are shown in Table 4.

[Evaluation 3. Evaluation of change in gradation before and after durability]
After performing a durability initial test and durability image output evaluation (A4 landscape, 40% print ratio, 50,000 sheets) under a high temperature and humidity environment (30°C, 80% RH), the difference in gradation between the initial test and the test immediately after 50,000 sheets was confirmed. The images were judged by measuring the image density of each test using an X-Rite color reflection densitometer (X-Rite 404A).
Pattern 1: 0.10 or more and 0.13 or less Pattern 2: 0.25 or more and 0.28 or less Pattern 3: 0.45 or more and 0.48 or less Pattern 4: 0.65 or more and 0.68 or less Pattern 5: 0.85 or more and 0.88 or less Pattern 6: 1.05 or more and 1.08 or less Pattern 7: 1.25 or more and 1.28 or less Pattern 8: 1.45 or more and 1.48 or less The evaluation criteria for the change in gradation before and after durability were as follows: When the evaluation was A to C, it was determined that the effects of the present invention were obtained.
A: All pattern images satisfy the above density range.
B: One or two pattern images are outside the above density range.
C: 3 to 4 Two pattern images are outside the above density range.
D: Five or more pattern images are outside the above density range.
The evaluation results are shown in Table 4.

<Examples 2 to 18 >
Examples 2 to 18 were evaluated in the same manner as in Example 1, except that the two-component developer used for evaluation was changed to the two-component developer shown in Table 4. The evaluation results are shown in Table 4.

1 Electrostatic latent image carrier 2 Charger 3 Exposure device 4 Development device 5 Development container 6 Developer carrier 7 Magnet 8 Regulating member 9 Intermediate transfer body 10 Intermediate transfer charger 11 Transfer charger 12 Recording medium (transfer material)
13 Fixing unit 14 Intermediate transfer body cleaner 15 Cleaner 16 Pre-exposure unit 21 Raw material fixed quantity supply means 22 Compressed gas adjustment means 23 Inlet pipe 24 Conical protruding member 25 Supply pipe 26 Processing chamber 27 Hot air supply means 28 Cold air supply means 29 Regulating means 30 Recovery means 31 Hot air inlet portion 32 Distribution member 33 Swirling member 34 Powder particle supply port 101 Replenishment developer storage container 102 Developing unit 103 Cleaning device 104 Developer recovery container 105 Toner concentration detection sensor 106 Discharge device

Claims (10)

A magnetic carrier comprising magnetic carrier particles having a magnetic core and a resin coating layer coating the surface of the magnetic core,
the coating resin layer contains a silicone modified resin and fine particles,
the fine particles have a functional group represented by formula (1) or a functional group represented by formula (2) on the surface of the fine particles at a functional group concentration of 20% or more;
the magnetic carrier particles have a functional group represented by the formula (1) or a functional group represented by the formula (2) on the surface of the magnetic carrier particles in a functional group concentration of 0.01% or more and 0.05% or less;
The magnetic carrier is characterized in that the functional group concentration of the fine particles and the functional group concentration of the magnetic carrier particles are calculated by calculation formula 1 and calculation formula 2, respectively.
(In formula (1) and formula (2), R1 is a hydrogen atom or a methyl group.)
Concentration of functional groups in fine particles=(fluorine value measured by X-ray photoelectron spectroscopy/g)÷(specific surface area of fine particles/g) (Formula 1)
Concentration of functional group of magnetic carrier particle=(fluorine value measured by X-ray photoelectron spectroscopy/g)÷(specific surface area of magnetic carrier particle/g) (Formula 2) The fine particles are SrTiO ₃ Particles, Al ₂ O ₃ Particles, SiO ₂ 2. The magnetic carrier according to claim 1, which is at least one particle selected from the group consisting of carbon particles and acrylic particles. The fine particles are SiO ₂ 3. The magnetic carrier according to claim 2, which is a particle. The silicone modified resin is
(i) one or more units selected from the group consisting of units represented by the following formulas (3) to (6),
(ii) one selected from units represented by the following formulas (3') to (5'):
Contains
(iii) In the units represented by the formulae (3') to (5'), the units represented by the formulae (3) to (6) are linked to each other so as to share one oxygen atom;
The magnetic carrier according to any one of claims 1 to 3, wherein the total content of the units represented by the formulas (3) to (6) and the units represented by the formulas (3') to (5') in the silicone modified resin is 3% by mass or more and 50% by mass or less .
(In formulas (3) to (6) and formulas (3') to (5'), R2 to R7 each independently represent a hydrogen atom, an alkyl group having 1 to 4 carbon atoms , a phenyl group, or an alkenyl group having 2 to 4 carbon atoms; -O _1/2 represents that an O is shared with an adjacent Si atom;
In formulas (3') to (5'), ** represents a site that bonds to an alkylene group or a site that bonds to an oxygen atom that is bonded to a carbon atom. 5. The magnetic carrier according to claim 4, wherein the silicone modified resin is mainly composed of a unit represented by the following formula (7) and a unit represented by the following formula (8), and when the mass of the unit represented by the formula (7) is a and the mass of the unit represented by the formula (8) is b, the ratio of the mass of the unit represented by the formula (5) to the mass of the unit represented by the formula (6), a/ b , is 1.00 or more and 30.0 or less.
(In formula (7),
R8 is a hydrogen atom or a methyl group;
R9 is a hydrocarbon group having 1 to 6 carbon atoms, an alkyl group having 2 to 4 carbon atoms and having a hydroxyl group as a substituent, or an alkyl group having 1 to 4 carbon atoms and having a carboxy group as a substituent,
l is an integer of 1 or more.
(In formula (8),
R10 is a hydrogen atom or a methyl group;
R11 is a hydrogen atom or a hydrocarbon group having 1 to 6 carbon atoms,
R12 is a single bond or an alkylene having 1 to 5 carbon atoms,
m is an integer of 1 or more,
* is a site where a siloxane moiety is bonded, and is connected to ** of any of the units represented by the following formulas (3') to (5'):
The unit represented by formula (3') to formula (5') is connected to any one of the units represented by the following formulas (3) to (6) once or repeatedly so as to share one oxygen atom:
The terminal of the siloxane moiety is a unit of the above formula (6),
R2 to R7 in formulas (3') to (5') and formulas (3) to (6) are each independently a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, or a phenyl group, -O _1/2 represents that O is shared with the adjacent Si atom,
The number of silicon atoms in the siloxane moiety is 2 to 150. 6. The magnetic carrier according to claim 1 , wherein the concentration of Si atoms on the surface of the magnetic carrier particles is 1.0 atomic % or more and 8.0 atomic % or less, as measured by X-ray photoelectron spectroscopy. 7. The magnetic carrier according to claim 1 , wherein the volume average particle size of the primary particles of the fine particles is 10 nm or more and 100 nm or less. 8. The magnetic carrier according to claim 1 , wherein the coating resin layer contains a silicone-modified (meth)acrylic resin and a (meth)acrylic resin. A two-component developer comprising the magnetic carrier according to any one of claims 1 to 8 and a toner. A replenishing developer comprising the magnetic carrier according to any one of claims 1 to 8 and a toner.

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