Magnetic carrier, two-component developer and replenishing developer

Abstract

The present invention relates to a magnetic carrier, a two-component developer, and a replenishing developer. A magnetic carrier includes: a magnetic core; and a coating resin coating the surface of the magnetic core, wherein the coating resin includes a resin A and a resin B; the content of resin A is 1 to 50% by mass, and the content of resin B is 50 to 99% by mass relative to the coating resin; resin A has a specific unit Y1 and a specific unit Y2, and resin B contains 0.1% by mass or less of the specific unit Y2; and when the mass of resin A is represented by X, the mass of unit Y1 is represented by a, and the mass of unit Y2 is represented by b, 0.90 ≤ (a + b) / X ≤ 1.00 and 1.00 ≤ a / b ≤ 30.0 are satisfied, and 0 ≤ |SPa-SPb| ≤ 2.0 is also satisfied.

Description

Technical Field

[0001] The present disclosure relates to a magnetic carrier, a two-component developer, and a replenishing developer used in an image forming method for visualizing an electrostatic charge image using electrophotography. Background Art

[0002] Generally, electrophotographic image forming methods generally employ a method that involves forming an electrostatic latent image on an electrostatic image carrier using various means, attaching a toner to the electrostatic latent image, and developing the electrostatic latent image. For this development, a two-component development method is widely used, which involves mixing carrier particles, known as magnetic carriers, with the toner, triboelectrically charging the toner to impart an appropriate amount of positive or negative charge, and developing the toner using the charge as a driving force.

[0003] Two-component development methods can impart functions such as stirring, transporting, and charging the developer to the magnetic carrier, thereby clarifying the sharing of functions between the magnetic carrier and the toner, and thus offering the advantage of satisfactory controllability of developer performance. In many cases, the magnetic carrier has a structure comprising a core for imparting transportability by virtue of its magnetic properties, and a coating resin that coats the core and imparts the ability to charge the toner.

[0004] In recent years, due to technological advances in the field of electronic photography, the longevity of the main body has been required to be higher, and the carrier has been required to maintain the charge-imparting ability even when used for a long time, but it is generally known that the charge-imparting ability of the carrier is reduced due to the reduction of the charged sites caused by the adhesion of the colorant components, and harmful effects such as changes in color tone occur in the image.

[0005] As a means for obtaining durability against adhesion of the above-mentioned toner components (hereinafter referred to as “staining resistance”), an example of using silicone resin or the like, which is a material with low surface free energy, as a coating resin has been adopted (Japanese Patent Application Laid-Open No. 2002-91093). Summary of the Invention

[0006] However, generally, materials with low surface free energy, such as silicone resins, can reduce the adhesion of toner components, but they have weak molecular interactions and tend to be easily destroyed by external forces. Therefore, when silicone resins are used as the coating resin for a carrier, the coating resin wears due to mechanical loads generated during stirring or transportation within a developing device (hereinafter referred to as "wear resistance"). As a result of the carrier's surface resistance being reduced by the wear of the coating resin, the carrier's charge-imparting ability may be reduced in some cases (Japanese Patent Application Laid-Open Nos. 2002-91093, 2015-138230, and 2013-3428).

[0007] In order to achieve the above wear resistance, it is possible to consider using an example of a silicone-modified resin in which trifunctional silicon is bonded to its terminal; however, it is known that this structure cannot sufficiently reduce the surface free energy of the support surface, and therefore cannot improve the stain resistance (Japanese Patent Application Laid-Open No. 2015-138230). On the other hand, when a resin having a silicone structure in a side chain is used as a structure for further reducing the surface free energy, it has been determined that the surface free energy between molecules becomes small, and wear resistance becomes insufficient, as in the case of using the above-mentioned silicone resin (Japanese Patent Application Laid-Open No. 2013-3428).

[0008] In other words, in order to realize a highly stable carrier, it is necessary to simultaneously obtain both contamination resistance for reducing adhesion of toner components and wear resistance for reducing wear of the coating layer due to mechanical load or the like.

[0009] In summary, the present disclosure aims to provide a stable carrier having stain resistance and abrasion resistance, which achieves reduced fogging, reduced toner scattering, stable image density, and developability even when used for a long period of time in an image forming method using a two-component development system.

[0010] As a result of intensive studies, the present inventors have found that a carrier can obtain both contamination resistance and abrasion resistance by employing resin A and resin B shown in the following structure.

[0011] Resin A has a structure in which a silicone structure similar to that of a silicone resin is grafted onto the main chain; this silicone structure reduces surface free energy and improves stain resistance. Furthermore, Resin B has a structure highly compatible with the main chain of Resin A, so Resins A and B are mixed with each other, thereby improving wear resistance. As mentioned above, using only a resin such as Resin A, which has a grafted silicone structure, does not provide sufficient wear resistance. However, by combining Resin A with Resin B, which has high compatibility with the main chain of Resin A, the carrier can also achieve wear resistance.

[0012] Specifically, one embodiment of the present disclosure provides a magnetic carrier comprising: a magnetic core; and a coating resin coating the surface of the magnetic core, wherein

[0013] The coating resin includes resin A and resin B;

[0014] The content of the resin A is 1 to 50% by mass, and the content of the resin B is 50 to 99% by mass relative to the total mass of the coating resin;

[0015] Resin A has a unit Y1 represented by the following formula (1) and a unit Y2 represented by the following formula (2), and

[0016] In the resin B, the content of the unit Y2 represented by the following formula (2) is 0.1% by mass or less; and

[0017] When the mass of resin A, the mass of unit Y1 in resin A, and the mass of unit Y2 in resin A are represented by X, a, and b, respectively, X, a, and b satisfy the following expressions (a) and (b):

[0018] 0.90≤(a+b) / X≤1.00 (a), and

[0019] 1.00≤a / b≤30.0 (b), and

[0020] When the SP value of the unit Y1 and the SP value of the resin B are represented by Spa and SPb, respectively, Spa and SPb satisfy the following expression (c):

[0021] 0≤|SPa-SPb|≤2.0 (c),

[0022] In formula (1),

[0023] R1 represents H or CH3, and

[0024] R2 represents a hydrocarbon group having 1 to 8 carbon atoms and optionally having a substituent, wherein the substituent is a hydroxyl group or a carboxyl group; and

[0025] In formula (2),

[0026] R3 represents H or CH3,

[0027] R4 represents H or CH3,

[0028] R5 represents a single bond or a hydrocarbon group having 1 to 10 carbon atoms,

[0029] R6 represents a hydrocarbon group having 1 to 10 carbon atoms,

[0030] R7 represents H, CH3 or Si(CH3)3, and

[0031] n represents an integer from 2 to 150

[0032]

[0033] In addition, another embodiment of the present disclosure provides a two-component developer including the above-mentioned magnetic carrier and a toner.

[0034] In addition, yet another embodiment of the present disclosure provides a replenishing developer including the above-mentioned magnetic carrier and a toner.

[0035] According to the present disclosure, a stable carrier having contamination resistance and abrasion resistance is provided, which achieves reduced fogging, reduced toner scattering, stable image density, and developability even in long-term use.

[0036] Further features of the present disclosure will become apparent from the following description of exemplary embodiments with reference to the attached drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 An example of a schematic diagram of a surface treatment device.

[0038] Figure 2 is an example of a schematic diagram of an image forming apparatus.

[0039] Figure 3 An example of a schematic diagram of a full-color image forming apparatus to which the image forming method is applied.

[0040] Figure 4A Schematic diagram of an apparatus for measuring the specific resistance of a magnetic carrier and a porous magnetic core.

[0041] Figure 4B Schematic diagram of an apparatus for measuring the specific resistance of a magnetic carrier and a porous magnetic core. DETAILED DESCRIPTION

[0042] Preferred embodiments of the present disclosure will now be described in detail according to the accompanying drawings.

[0043] In the present disclosure, unless otherwise stated, the description “above XX and below YY” or “XX to YY” expressing a numerical range means a numerical range including the lower limit and the upper limit as endpoints.

[0044] The magnetic carrier of the present disclosure is a magnetic carrier comprising: a magnetic core; and a coating resin coating the surface of the magnetic core, wherein

[0045] The coating resin includes resin A and resin B;

[0046] The content of the resin A is 1 to 50% by mass, and the content of the resin B is 50 to 99% by mass relative to the total mass of the coating resin;

[0047] Resin A has a unit Y1 represented by the following formula (1) and a unit Y2 represented by the following formula (2), and

[0048] In the resin B, the content of the unit Y2 represented by the following formula (2) is 0.1% by mass or less; and

[0049] When the mass of resin A, the mass of unit Y1 in resin A, and the mass of unit Y2 in resin A are represented by X, a, and b, respectively, X, a, and b satisfy the following expressions (a) and (b):

[0050] 0.90≤(a+b) / X≤1.00 (a), and

[0051] 1.00≤a / b≤30.0 (b), and

[0052] When the SP value of the unit Y1 and the SP value of the resin B are represented by Spa and SPb, respectively, Spa and SPb satisfy the following expression (c):

[0053] 0≤|SPa-SPb|≤2.0 (c),

[0054] In formula (1),

[0055] R1 represents H or CH3, and

[0056] R2 represents a hydrocarbon group having 1 to 8 carbon atoms and optionally having a substituent, wherein the substituent is a hydroxyl group or a carboxyl group; and

[0057] In formula (2),

[0058] R3 represents H or CH3,

[0059] R4 represents H or CH3,

[0060] R5 represents a single bond or a hydrocarbon group having 1 to 10 carbon atoms,

[0061] R6 represents a hydrocarbon group having 1 to 10 carbon atoms,

[0062] R7 represents H, CH3 or Si(CH3)3, and

[0063] n represents an integer from 2 to 150,

[0064]

[0065] As mentioned above, when only resins with low surface free energy, such as silicone resins, are used as coating resins, wear resistance deteriorates. The carrier disclosed herein comprises resin A and resin B, wherein resin A has a structure similar to that of silicone resin and is grafted onto the main chain. This silicone structure reduces surface free energy and improves stain resistance. Furthermore, as will be described later, resin B has a structure highly compatible with the main chain of resin A. Therefore, resins A and B are less likely to separate due to mechanical loads such as shearing by a developing device, resulting in improved wear resistance.

[0066] Resin A has unit Y1 represented by the above formula (1) and unit Y2 represented by the above formula (2). Unit Y2 has an organic silicon structure, and this structure reduces surface free energy, thereby improving anti-fouling properties.

[0067] In the unit Y1 in formula (1), R1 represents H or CH3, and R2 represents a hydrocarbon group having 1 to 8 carbon atoms and optionally having a substituent, and is preferably an alkyl group having 1 to 6 carbon atoms and optionally having a substituent. The substituent in R2 is a hydroxyl group or a carboxyl group. As a specific method for introducing R1 and R2, for example, when the resin A is polymerized, R1 and R2 can be introduced by copolymerizing the following monomers: methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, hexyl acrylate, cyclobutyl acrylate, cyclohexyl acrylate, cyclopentyl acrylate, cyclooctyl acrylate, methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate, hexyl methacrylate, cyclobutyl methacrylate, cyclohexyl methacrylate, cyclopentyl methacrylate, cyclooctyl methacrylate, 2-hydroxyethyl acrylate, 2-carboxyethyl acrylate, 2-hydroxyethyl methacrylate, and 2-carboxyethyl methacrylate.

[0068] In the unit Y2, R3 represents H or CH3, R4 represents H or CH3, and R5 represents a single bond or a hydrocarbon group having 1 to 10 carbon atoms and preferably an alkylene group having 1 to 6 carbon atoms; R6 represents a hydrocarbon group having 1 to 10 carbon atoms and preferably an alkyl group having 1 to 6 carbon atoms or a phenyl group; and R7 represents H, CH3 or Si(CH3)3, and n represents an integer from 2 to 150. As for a specific method of introducing these substituents, the substituents can be introduced by, for example, copolymerizing any acrylate, methacrylate or 2-butenoic acid ester in which the organosilicon structure is esterified when the resin A is polymerized.

[0069] In the resin A, when the mass of the resin A, the mass of the unit Y1, and the mass of the unit Y2 are represented by X, a, and b, respectively, X, a, and b satisfy the following expressions (a) and (b).

[0070] 0.90≤(a+b) / X≤1.00 (a)

[0071] 1.00≤a / b≤30.0 (b)

[0072] This relationship indicates that resin A contains unit Y1 and unit Y2 in an amount of 90% by mass or more of all units, and the mass of unit Y1 is between the same mass as the mass of unit Y2 and the mass of unit Y2 30 times heavier. When (a+b) / X is less than 0.90, compatibility with resin B decreases and wear resistance deteriorates, or surface free energy decreases and contamination resistance deteriorates. As a result, neither case is preferred. In addition, when a / b is less than 1.00, the structure of resin A becomes a structure in which the ratio of unit Y2 to unit Y1 is too high, the surface free energy becomes too small, and therefore, wear resistance deteriorates. In contrast, when a / b becomes greater than 30, the surface free energy becomes too high, and therefore, contamination resistance deteriorates.

[0073] The proportion of Resin A in the coating resin is 1 to 50% by mass. When the proportion of Resin A in the coating resin is less than 1% by mass, the surface free energy is not reduced, resulting in insufficient stain resistance. When the proportion of Resin A in the coating resin exceeds 50% by mass, the intermolecular forces derived from the low surface free energy decrease, becoming stronger than the wear resistance achieved through interaction with Resin B; thus, wear resistance becomes insufficient. The proportion of Resin A in the coating resin is preferably in the range of 1 to 20% by mass, and more preferably in the range of 3 to 20% by mass.

[0074] The proportion of Resin B in the coating resin is 50 to 99% by mass. If the proportion of Resin B in the coating resin is less than 50% by mass, the resin strength becomes insufficient, resulting in poor wear resistance. If the proportion of Resin B in the coating resin exceeds 99% by mass, the effect of the low surface free energy component becomes insufficient, resulting in poor stain resistance. This proportion is preferably 80 to 99% by mass.

[0075] When the SP value of the unit Y1 and the SP value of the resin B are represented by SPa and SPb, respectively, Spa and SPb satisfy the following expression (c).

[0076] 0≤|SPa-SPb|≤2.0 (c)

[0077] The above SP values ​​are calculated by the following method.

[0078] Formula: SP value = √(Ev / v) = √(ΣΔei / ΣΔvi)

[0079] Where, Ev: evaporation energy (J / mol),

[0080] v: molar volume (cm 3 / mol),

[0081] Δei: the evaporation energy of each atom or atomic group, and

[0082] Δvi: molar volume of each atom or atomic group.

[0083] When the above relational expression (c) is satisfied, the compatibility between resin A and resin B increases, and wear resistance improves. When |SPa-SPb| becomes greater than 2.0, the compatibility between resin A and resin B decreases, and the interaction between the molecules decreases, thereby deteriorating wear resistance. The smaller |SPa-SPb|, the higher the compatibility, and when |SPa-SPb| is 1.0 or less, wear resistance is further improved, so this is preferred.

[0084] When m is represented by the sum of the number of units Y1 and the number of units Y2, the resin A preferably satisfies the following expression (d).

[0085] 50≤m≤250 (d)

[0086] When m is 50 or more, the molecular weight becomes sufficiently high, and thus the wear resistance is further improved; and when m is 250 or less, the interaction between resin A and resin B is further enhanced, and thus the wear resistance and stain resistance are further improved.

[0087] In the magnetic carrier of the present disclosure, it is preferred that the Si content on the surface of the magnetic carrier, as measured by electron spectroscopy for chemical analysis (ESCA), is 1.0 to 15.0 atomic %. When Si is 1.0 atomic % or more, the surface free energy of the carrier can be reduced, thereby further improving contamination resistance. When Si is 15.0 atomic % or less, the intermolecular interaction near the carrier surface is enhanced, thereby further improving wear resistance.

[0088] The atomic concentration of Si was measured in the following manner.

[0089] <Method for Measuring Si Atomic Concentration by XPS>

[0090] The magnetic carrier was adhered to the indium foil. The particles were evenly adhered to the indium foil so that no part of the indium foil was exposed.

[0091] The measurement conditions are as follows.

[0092] Equipment: PHI5000 VERSAPROBE II (Ulvac-Phi, Inc.)

[0093] Irradiation radiation: Al Kα radiation

[0094] Output: 25W 15kV

[0095] Pass energy: 58.7eV

[0096] Step size: 0.125eV

[0097] XPS peaks: C 1s, O 1s, Si 2p, Ti 2p, and Sr 3d

[0098] In resin A, n in formula (2) represents the length of the side chain formed by the organosilicon structure of the organosilicon-graft structure. When n is 2 to 150, the surface free energy of the resin coating on the support can be reduced. When n is 1 or less, the surface free energy cannot be reduced, and thus, the stain resistance deteriorates. When n is greater than 150, the interaction between resin A and resin B becomes weak, and thus, the wear resistance deteriorates. When n is 5 or more and 60 or less, the wear resistance and stain resistance are improved, and therefore, this is preferred.

[0099] Resin A may have functional groups such as nitrogen-containing groups, carboxyl groups, and hydroxyl groups. By having these functional groups, Resin A can suppress electrostatic charging of the developer, particularly in low-humidity environments. Furthermore, when Resin A has hydroxyl groups, hydrogen bonding effects are also exerted, further improving wear resistance, which is therefore preferred.

[0100] When the resin A has a carboxyl group, its acid value preferably ranges from 5 to 100 mgKOH / mg. When the acid value of the resin A is 5 or more, electrostatic overcharging is improved, and when the acid value of the resin A is 100 or less, the charge retention of the developer is improved.

[0101] When the resin A has a hydroxyl group, its hydroxyl value preferably ranges from 5 to 50 mgKOH / mg. When the hydroxyl value of the resin A is 5 or more, electrostatic overcharging is improved, and when the hydroxyl value of the resin A is 50 or less, the charge retention of the developer is improved.

[0102] As the resin B, it is preferable to use such a resin that when the SP value of the unit Y1 and the SP value of the resin B are represented by SPa and SPb, respectively, Spa and SPb satisfy the following expression (c):

[0103] 0≤|SPa-SPb|≤2.0(c).

[0104] However, there is no particular limitation on the structure, and for example, such resins as acrylic resins, urethane resins, and polyethylene, polyethylene terephthalate, polystyrene, and phenol resins can be used.

[0105] From the viewpoint that the SP value of the resin B approaches the SP value of the resin A and the compatibility with the resin A is improved, the resin B is preferably an acrylic resin.

[0106] Regarding the structure of the resin B, it is preferred that the resin B has the unit Y1 because the difference in SP value between the resin B and the resin A becomes smaller and thus the compatibility improves, and it is more preferred that the resin B contains 75% by mass or more of the unit Y1.

[0107] It is preferred that the resin B contains the unit Y3 shown in the following formula (3), and preferably contains 1 to 75% by mass of the unit Y3.

[0108]

[0109] In formula (3), R8 represents a cyclohexyl group, a cycloheptyl group, a cyclooctyl group, a cyclopentyl group, a cyclobutyl group or a cyclopropyl group.

[0110] It is preferable that the resin B contain an alicyclic hydrocarbon group as contained in the unit Y3, because the surface of the resin coating layer (coating film surface) covering the surface of the magnetic core becomes smooth, the adhesion of toner and components derived from the toner, such as external additives that impart fluidity to the toner, is suppressed, and the contamination resistance is further improved. The unit Y3 may contain only one structure, or may contain two or more structures.

[0111] In the synthesis of the resin B, it is preferred to use a (meth)acrylate monomer having an alicyclic hydrocarbon group in an amount ranging from 50 to 90 parts by mass when all monomers used for the synthesis of the resin B are set to 100 parts by mass.

[0112] From the viewpoint of coating stability, it is preferred that the weight average molecular weight (Mw) of the resin B is 20,000 to 120,000, and more preferably 30,000 to 100,000.

[0113] Preferably, the acid value of resin B is 0 to 3.0mgKOH / g, more preferably 0 to 2.8mgKOH / g, and particularly preferably 0 to 2.5mgKOH / g. When the acid value of resin B is below 3.0mgKOH / g, it is difficult to occur the self-cohesion of the resin caused by the influence of the acid value, and the smoothness of the surface (film surface) of the resin coating layer is difficult to reduce. The acid value of resin B can be controlled by using a monomer with a polar group such as a carboxyl or sulfonic group (sulfonic acid group) when the coating resin A is synthesized, and adjusting the amount of the monomer added. However, preferably, the acid value of resin A is low, and preferably does not use a monomer with a polar group. Even when only using a monomer forming an ester bond to synthesize resin, in some cases, a faint acid value is also produced in the synthesized resin. It is believed that this is because when the resin is synthesized (polymerized), a part of the ester bond decomposes to generate a carboxyl group.

[0114] Resin B is preferably a polymer (copolymer) obtained by copolymerizing a (meth)acrylate monomer having an alicyclic hydrocarbon group with a macromonomer. When a macromonomer is used in the synthesis of Resin B, the adhesion between the resin coating layer and the magnetic core is improved, and the charge-imparting ability of the magnetic carrier to the toner is improved.

[0115] The above macromonomer is preferably a macromonomer obtained by polymerizing at least one selected from the group consisting of methyl acrylate, methyl methacrylate, butyl acrylate, butyl methacrylate, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, styrene, acrylonitrile, and methacrylonitrile.

[0116] It is preferred that the weight average molecular weight (Mw) of the macromonomer is from 2,000 to 10,000, and more preferably from 3,000 to 8,000.

[0117] In the synthesis of the resin B, it is preferred to use a macromonomer in an amount ranging from 5.0 to 40.0 parts by mass when all monomers used for the synthesis of the covering resin A are set to 100 parts by mass.

[0118] During the synthesis of Resin B, a methacrylate monomer, in particular, is added. This leads to strong molecular entanglement and improved adhesion between the coating resin and the magnetic core. As a result, the coating layer does not peel off even under loads such as from the stirring member in the developing device, maintaining stable charge-imparting capabilities over long periods of time and enabling high-quality image output.

[0119] Preferably, the resin coating layer of the present disclosure contains conductive particles. The conductive particles can appropriately control the specific resistance of the carrier for electrophotography. As a result, the counter charge after toner development can be released, and white spots can be reduced. Preferably, the content of the conductive particles added to the coating resin is 0.1 to 20 parts by mass relative to 100 parts by mass of the coating resin. When the content of the conductive particles is less than 0.1 parts by mass, it is difficult to obtain the effect of adding the conductive particles, and when the content of the conductive particles exceeds 20 parts by mass, there is a concern that the color tone will deteriorate due to the detachment of the conductive particles. Examples of conductive particles include carbon black, titanium oxide, and silver.

[0120] In addition, to enhance the ability to impart charge to the toner and improve releasability, microparticles may be included in the coating resin. The microparticles included in the resin coating layer may be microparticles of any organic or inorganic material, but are preferably crosslinked resin microparticles or inorganic microparticles, either of which has sufficient strength to maintain its shape during coating. Examples of crosslinked resins forming the crosslinked resin microparticles include crosslinked polymethyl methacrylate resins, crosslinked polystyrene resins, melamine resins, guanamine resins, urea-formaldehyde resins, phenol-formaldehyde resins, and nylon resins. Examples of inorganic microparticles include silica, alumina, and titanium dioxide.

[0121] The content of the fine particles in the coating resin is preferably 0.1 to 20 parts by mass relative to 100 parts by mass of the coating resin.

[0122] The magnetic core particles of the present disclosure may be known magnetic particles such as magnetite particles, ferrite particles, and magnetic material-dispersed resin particles. In particular, from the perspective of achieving a long life, magnetic particles obtained by filling the pores of porous magnetic particles with a resin, or magnetic material-dispersed resin particles, in other words, magnetic particles comprising a magnetic oxide and a resin composition, are preferred because they can reduce the specific gravity of the magnetic carrier.

[0123] For example, a magnetic carrier with a reduced specific gravity reduces the load of toner in a developer state in a developing device, prevents toner components from adhering to the surface of the magnetic carrier, and reduces the load between carriers, further reducing peeling, chipping, and scratching of the resin coating layer. Furthermore, it improves dot reproducibility and enables the production of high-definition images.

[0124] For reference, as the resin contained in the pores of the magnetic particles having a porous shape, a copolymer resin to be used as a coating resin can be used, but the resin is not limited thereto, and known resins such as thermoplastic resins and thermosetting resins can be used.

[0125] As the thermoplastic resin, a copolymer to be used as the coating resin is preferred, but other examples include the following: polystyrene, polymethyl methacrylate, styrene-acrylate copolymer, styrene-methacrylate copolymer, styrene-butadiene copolymer, ethylene-vinyl acetate copolymer, polyvinyl chloride, polyvinyl acetate, polyvinylidene fluoride resin, fluorocarbon resin, perfluorocarbon resin, solvent-soluble perfluorocarbon resin, polyvinyl pyrrolidone, petroleum resin, novolac resin, saturated alkyl polyester resin, aromatic polyester resins such as polyethylene terephthalate, polybutylene terephthalate and polyarylate, polyamide resin, polyacetal resin, polycarbonate resin, polyethersulfone resin, polysulfone resin, polyphenylene sulfide resin and polyetherketone resin.

[0126] Examples of thermosetting resins include the following compounds: phenolic resins, modified phenolic resins, maleic resins, alkyd resins, epoxy resins, acrylic resins, unsaturated polyesters obtained by polycondensation of maleic anhydride, terephthalic acid and polyols, urea resins, melamine resins, urea-melamine resins, xylene resins, toluene resins, guanamine resins, melamine-guanamine resins, acetoguanamine resins, glyphthalate resins, furan resins, silicone resins, polyimide and polyamide-imide resins, polyetherimide resins, and polyurethane resins.

[0127] The example of the method for filling the voids of the ferrite particles with a porous shape with a resin component includes diluting the resin component with a solvent, and adding the porous magnetic core particles to the method in the diluent. The solvent used here can be any solvent that can dissolve each resin component. When the resin is soluble in an organic solvent, such organic solvents can use toluene, xylene, cellosolve butyl acetate, methyl ethyl ketone, methyl isobutyl ketone and methanol. In addition, when the resin component is water-soluble or the resin component is an emulsified type, water can be used. The example of the method for adding the resin component diluted by a solvent to the inside of the porous magnetic core particles includes impregnating the resin component with a coating method such as an impregnation method, a spraying method, a brushing method, a fluidized bed and a mixing method, and then, volatilizing the solvent. When filled with a thermosetting resin, the solvent is volatilized, and the temperature is raised to the temperature at which the resin used is solidified, and a curing reaction is caused.

[0128] On the other hand, specific examples of methods for producing magnetic material dispersed resin particles include the following methods. Magnetic material dispersed resin particles can be obtained by mixing a submicron magnetic material, such as iron powder, magnetite particles, or ferrite particles, so as to disperse it in a thermoplastic resin, pulverizing the mixture to a desired carrier particle size, and subjecting the resulting material to a thermal or mechanical spheroidization treatment as needed. Alternatively, magnetic material dispersed resin particles can also be produced by dispersing the above magnetic material in a monomer and polymerizing the monomer to form a resin.

[0129] Examples of resins in this case include vinyl resins, polyester resins, epoxy resins, phenolic resins, urea-formaldehyde resins, polyurethane resins, polyimide resins, cellulose resins, silicone resins, acrylic resins, and polyether resins. The resin may be a single resin or a mixture of two or more resins. In particular, phenolic resins are preferred in terms of improving the strength of the magnetic core. True density and specific resistivity can be adjusted by adjusting the amount of magnetic material. Specifically, in the case of magnetic particles, it is preferred to add magnetic particles in an amount of 70 to 95% by mass relative to the carrier.

[0130] It is preferable that the volume-based 50% diameter (D50) of the magnetic core is 20 μm or more and 80 μm or less, because the coating resin is uniformly coated thereon, and the density of the magnetic brush of the developer is moderated to prevent adhesion of the carrier and provide high-quality images.

[0131] The specific resistance of the magnetic core is preferably 1.0×10 5 (Ω·cm) or more and 1.0×10 14 (Ω·cm) or less, since this enables satisfactory developability to be obtained.

[0132] There is no particular limitation on the method for coating the surface of the magnetic core with a coating resin, and a known method can be used. For example, there is a so-called impregnation method in which the solvent is evaporated while stirring the magnetic core and the coating resin solution, and the surface of the magnetic core is coated with the coating resin. Specific examples include a universal mixing agitator (manufactured by Fuji Paudal Co., Ltd.) and a Nauta mixer (manufactured by Hosokawa Micron Corporation). In addition, there is a method in which a coating resin solution is sprayed from a spray nozzle while forming a fluidized layer, and the surface of the magnetic core is coated with the coating resin. Specific examples of the apparatus include SPIRACOATER (manufactured by Okada Seiko Co., Ltd.) and SPIRAFLOW (manufactured by Freund Corporation). In addition, there is a method for dry-coating the magnetic core with a coating resin having a granular form. Specific examples of the method include treatment methods using devices such as Hybridizer (manufactured by Nara Machinery Co., Ltd.), Mechanofusion (manufactured by Hosokawa Micron Corporation), Hiflex Gral (manufactured by Fukae Powtech), and Theta Composer (manufactured by Tokuju Corporation).

[0133] Next, the magnetic carrier will be described.

[0134] Preferably, the magnetic carrier has a magnetization intensity of 40 (Am 2 / kg) and above 70(Am 2 When the magnetization intensity of the magnetic carrier is within the above range, the magnetic restraining force on the developing sleeve is appropriate, and thus the occurrence of carrier adhesion can be more satisfactorily reduced. In addition, the magnetic carrier can reduce the stress applied to the toner by the magnetic brush, and can satisfactorily suppress the deterioration of the toner and the adhesion of the toner to other components.

[0135] In addition, the magnetization intensity of the magnetic carrier can be appropriately adjusted by the amount of the resin contained.

[0136] Preferably, the residual magnetization of the magnetic carrier is 20.0 (Am 2 / kg) or less, and more preferably 10.0 (Am 2 When the residual magnetization of the magnetic carrier is within the above range, the developer obtains particularly satisfactory fluidity and provides satisfactory dot reproducibility.

[0137] Preferably, the true density of the magnetic carrier is 2.5 (g / cm 3 ) and above 5.5(g / cm 3 ) or less, and more preferably 3.0 (g / cm 3 ) and above 5.0(g / cm 3 ) or less. A two-component developer containing a magnetic carrier having a true density within this range reduces the load on the toner and reduces the adhesion of toner components to the magnetic carrier. In addition, in order to achieve both satisfactory developability under low electric field strength and prevent carrier adhesion, a true density within this range is preferred for the magnetic carrier.

[0138] From the viewpoints of improving the charging capability of the toner, reducing carrier adhesion to the image area, and improving image quality, the 50% volume diameter (D50) of the magnetic carrier is preferably 21 μm or more and 81 μm or less. More preferably, the 50% volume diameter (D50) of the magnetic carrier is 25 μm or more and 60 μm or less.

[0139] Next, the structure of a toner that is preferable for achieving the objects of the present disclosure will be described in detail below.

[0140] <Binder Resin>

[0141] The toner particles disclosed herein may use the following polymers as binder resins. Examples include: single polymers of styrene and its substituents, such as polystyrene, polyparachlorostyrene, and polyvinyltoluene; styrene-based copolymers, such as styrene-parachlorostyrene copolymers, styrene-vinyltoluene copolymers, styrene-vinylnaphthalene copolymers, styrene-acrylate copolymers, and styrene-methacrylate copolymers; styrene-based copolymer resins, polyester resins, and mixed resins obtained by mixing or partially reacting polyester resins with vinyl resins; and polyvinyl chloride, phenolic resins, naturally modified phenolic resins, naturally modified maleic acid resins, acrylic resins, methacrylic resins, polyvinyl acetate, silicone resins, polyester resins, polyurethanes, polyamide resins, furan resins, epoxy resins, xylene resins, polyethylene resins, and polypropylene resins. Among these, polyester resins are preferably used as the main component from the perspective of low-temperature fixability.

[0142] The monomers used for the polyester unit of the polyester resin include: polyols (divalent, trivalent, or higher-valent alcohols); and polycarboxylic acids (divalent, trivalent, or higher-valent carboxylic acids), their anhydrides, or their lower alkyl esters. To produce a branched polymer that exhibits strain hardening properties, it is effective to partially crosslink the molecules of the amorphous resin. For this purpose, a trivalent or higher-valent polyfunctional compound is preferably used. Therefore, it is preferred that the raw material monomers for the polyester unit include trivalent or higher-valent carboxylic acids, their anhydrides or their lower alkyl esters, and / or trivalent or higher-valent alcohols.

[0143] The following polyol monomers can be used as the polyol monomer for the polyester unit of the polyester resin.

[0144] Examples of the diol 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, and hydrogenated bisphenol A; bisphenol represented by formula (A) and derivatives thereof;

[0145]

[0146] wherein R is an ethylene group or a propylene group, x and y are each an integer of 0 or greater, and the average value of x+y is 0 or greater and 10 or less; and

[0147] a diol represented by formula (B);

[0148]

[0149] wherein R' is -CH2CH2-, -CH2-CH(CH3)-, or -CH2-C(CH3)2-, x' and y' are each an integer greater than or equal to 0, and the average value of x'+y' is greater than or equal to 0 and less than or equal to 10.

[0150] Examples of trivalent or higher alcohol components include sorbitol, 1,2,3,6-hexanetetraol, 1,4-sorbitol, pentaerythritol, dipentaerythritol, tripentaerythritol, 1,2,4-butanetriol, 1,2,5-pentanetriol, glycerol, 2-methylglycerol, 2-methyl-1,2,4-butanetriol, trimethylolethane, trimethylolpropane, and 1,3,5-trimethylolbenzene. Among the trivalent or higher alcohols, glycerol, trimethylolpropane, and pentaerythritol are preferably used. These divalent and trivalent alcohols may be used alone or in combination of two or more.

[0151] The following polycarboxylic acid monomers can be used as the polycarboxylic acid monomer for the polyester unit of the polyester resin.

[0152] Examples of the dicarboxylic acid component 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, isooctenylsuccinic acid and isooctylsuccinic acid; and anhydrides of these acids and lower alkyl esters thereof. Among the dicarboxylic acids, maleic acid, fumaric acid, terephthalic acid and n-dodecenylsuccinic acid are preferably used.

[0153] Examples of tribasic or higher carboxylic acids, their 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-methylenecarboxyl propane, 1,2,4-cyclohexanetricarboxylic acid, tetra(methylenecarboxyl)methane, 1,2,7,8-octanetetracarboxylic acid, pyromellitic acid and enpol trimer acid; and their anhydrides or their lower alkyl esters. Among tribasic or higher carboxylic acids and their derivatives, 1,2,4-benzenetricarboxylic acid, i.e., trimellitic acid or its derivatives are particularly preferably used because they are cheap and the reaction control is easy. These dicarboxylic acids and tribasic or higher carboxylic acids can be used alone or in combination of two or more.

[0154] There is no particular limitation on the production method of the polyester unit of the present invention, and a known method can be used. The polyester resin is produced, for example, by simultaneously adding the above-mentioned alcohol monomer and carboxylic acid monomer and polymerizing the mixture through an esterification reaction or an ester exchange reaction and a condensation reaction. In addition, there is no particular limitation on the polymerization temperature, but it is preferably within the range of 180° C. to 290° C. When polymerizing the polyester unit, such polymerization catalysts as titanium-based catalysts, tin-based catalysts, zinc acetate, antimony trioxide, and germanium dioxide can be used. In particular, the binder resin of the present invention is more preferably a polyester unit polymerized using a tin-based catalyst.

[0155] In addition, from the viewpoint of fogging properties, the acid value of the polyester resin is 5 mgKOH / g or more and 20 mgKOH / g or less, and the hydroxyl value is preferably 20 mgKOH / g or more and 70 mgKOH / g or less, because the polyester resin can reduce the amount of moisture adsorption under high temperature and high humidity environments and can reduce non-electrostatic adhesion to a low level.

[0156] In addition, a mixture of a low molecular weight resin and a high molecular weight resin may be used as the binder resin. From the viewpoint of low temperature hardness and hot offset resistance, the content ratio of the high molecular weight resin to the low molecular weight resin is preferably 40 / 60 to 85 / 15 on a mass basis.

[0157] <Release Agent>

[0158] Examples of waxes used in the toner of the present disclosure include the following: hydrocarbon waxes such as low molecular weight polyethylene, low molecular weight polypropylene, alkylene copolymers, microcrystalline waxes, paraffin waxes and Fischer-Tropsch waxes; oxides of hydrocarbon waxes such as oxidized polyethylene waxes, or block copolymers thereof; waxes mainly containing fatty acid esters such as carnauba wax; and waxes in which some or all of the fatty acid esters are deoxidized such as deoxidized carnauba waxes. Examples further include the following: saturated straight-chain fatty acids such as palmitic acid, stearic acid, and montanic acid; unsaturated fatty acids such as brassenoic acid, eleostearic acid, and cinnamic acid; saturated alcohols such as stearyl alcohol, aralkyl alcohols, behenyl alcohol, carnauba alcohol, wax alcohol, and beeswax alcohol; polyols such as sorbitol; esters of fatty acids such as palmitic acid, stearic acid, behenyl alcohol, and montanic acid with alcohols such as stearyl alcohol, aralkyl alcohols, behenyl alcohol, carnauba alcohol, wax alcohol, and beeswax alcohol; fatty acid amides such as linoleamide, oleamide, and lauric acid amide; saturated fatty acids such as methylene bisstearamide, ethylene biscapric acid amide, ethylene bislauric acid amide, and hexamethylene bisstearamide. and fatty acid bisamides; unsaturated fatty acid amides such as ethylenebisoleamide, hexamethylenebisoleamide, N,N'-dioleyladipamide, and N,N'-dioleylsebacamide; aromatic bisamides such as m-xylene bisstearamide and N,N'-distearylisophthalamide; fatty metal salts (commonly known as metal soaps) such as calcium stearate, calcium laurate, zinc stearate and magnesium stearate; waxes in which aliphatic hydrocarbon waxes are grafted with vinyl monomers such as styrene or acrylic acid; partial esterification products of fatty acids and polyols such as monoglyceride of behenic acid; and methyl ester compounds having hydroxyl groups obtained by hydrogenation of vegetable oils and fats.

[0159] Among these waxes, hydrocarbon waxes such as paraffin wax and Fischer-Tropsch wax, or fatty acid ester waxes such as carnauba wax are preferred from the viewpoint of improving low-temperature fixability and fixation separation properties. In the present disclosure, hydrocarbon waxes having further improved hot offset resistance are more preferred.

[0160] In the present disclosure, the wax is preferably used in an amount of 3 to 8 parts by mass relative to 100 parts by mass of the binder resin.

[0161] Furthermore, in the endothermic curve at the time of temperature increase measured by a differential scanning calorimeter (DSC), it is preferred that the peak temperature of the maximum endothermic peak of the wax is 45° C. or higher and 140° C. or lower. It is preferred that the peak temperature of the maximum endothermic peak of the wax is within the above range because both storage stability and hot offset resistance of the toner can be achieved.

[0162] <Colorant>

[0163] The toner particles in the present disclosure may contain a colorant. Examples of the colorant include the following agents.

[0164] Examples of black colorants include carbon black and black toners obtained by mixing a yellow colorant, a magenta colorant, and a cyan colorant. Pigments can be used alone as colorants, but from the perspective of full-color image quality, it is more preferable to use a dye and a pigment in combination to improve vividness.

[0165] Examples of pigments for magenta toners include the following: CI 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, and 282; CI Pigment Violet 19; and CI Vat Red 1, 2, 10, 13, 15, 23, 29, and 35.

[0166] Examples of the dye for magenta toner include oil-soluble dyes such as CI Solvent Red 1, 3, 8, 23, 24, 25, 27, 30, 49, 81, 82, 83, 84, 100, 109 and 121, CI Disperse Red 9, CI Solvent Violet 8, 13, 14, 21 and 27, and CI Disperse Violet 1; and basic dyes such as CI Basic Red 1, 2, 9, 12, 13, 14, 15, 17, 18, 22, 23, 24, 27, 29, 32, 34, 35, 36, 37, 38, 39 and 40, and CI Basic Violet 1, 3, 7, 10, 14, 15, 21, 25, 26, 27 and 28.

[0167] Examples of the pigment for cyan toner include the following: CI Pigment Blue 2, 3, 15:2, 15:3, 15:4, 16, and 17; CI Vat Blue 6; CI Acid Blue 45; and copper phthalocyanine pigments in which a part of the phthalocyanine skeleton is substituted with 1 to 5 phthalimidomethyl groups.

[0168] Examples of the dye for cyan toner include CI Solvent Blue 70.

[0169] Examples of the pigment for yellow toner include the following: CI 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, and 185; and CI Vat Yellow 1, 3, and 20.

[0170] Examples of the dye for yellow toner include CI Solvent Yellow 162.

[0171] These colorants may be used alone or as a mixture, or may be used in the state of a solid solution. The colorant is selected based on hue angle, hue saturation, brightness, light resistance, OHP transparency, and dispersibility in the toner.

[0172] It is preferred that the content of the colorant is 0.1 to 30.0 parts by mass relative to the total amount of the resin components.

[0173] <Inorganic fine particles>

[0174] Mainly for the purpose of improving fluidity and chargeability, the toner preferably contains inorganic fine particles, and the inorganic fine particles are preferably attached to the surface of the toner.

[0175] As inorganic fine particles used as spacer particles for improving the releasability between the toner and the carrier, silica particles are preferred, and their maximum peak particle size based on number distribution is 80 nm to 200 nm. In order for the silica particles to function as spacer particles while more satisfactorily suppressing separation from the toner, the maximum peak particle size based on number distribution is more preferably 100 nm to 150 nm.

[0176] In order to improve the fluidity of the toner, the toner preferably contains inorganic fine particles having a maximum peak particle size based on number distribution of 20 nm or more and 50 nm or less, and the inorganic particles are preferably used in combination with silica particles.

[0177] In addition, other external additives may be added to the toner particles for the purpose of improving fluidity and transferability. Preferably, the external additives externally added to the surface of the toner particles contain inorganic fine particles such as titanium oxide, aluminum oxide, and silicon dioxide, and a combination of multiple external additives is also acceptable.

[0178] The total content of external additives is preferably 0.3 to 5.0 parts by mass, and more preferably 0.8 to 4.0 parts by mass, per 100 parts by mass of the toner particles. Among the external additives, the content of silica particles having a maximum peak particle size of 80 nm or more and 200 nm or less based on the number distribution is preferably 0.1 to 2.5 parts by mass, and more preferably 0.5 to 2.0 parts by mass. When the content of silica particles having a maximum peak particle size of 80 nm or more and 200 nm or less based on the number distribution is within this range, the effect of the silica particles as spacer particles becomes more significant.

[0179] In addition, it is preferred that the surfaces of the silica particles and inorganic fine particles used as external additives be hydrophobized. Preferably, the hydrophobization treatment is performed using a coupling agent, which includes: various titanium coupling agents and silane coupling agents; fatty acids and metal salts thereof; silicone oil; or a combination thereof.

[0180] Examples of the titanium coupling agent include the following agents: tetrabutyl titanate, tetraoctyl titanate, isopropyl triisostearoyl titanate, isopropyl tridecylbenzenesulfonyl titanate, and bis(dioctyl pyrophosphate)oxyacetate titanate.

[0181] In addition, examples of the silane coupling agent include the following compounds: 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.

[0182] Examples of fatty acids include long-chain fatty acids such as undecanoic acid, lauric acid, tridecanoic acid, dodecanoic acid, myristic acid, palmitic acid, pentadecanoic acid, stearic acid, heptadecanoic acid, arachidic acid, montanic acid, oleic acid, linoleic acid, and arachidonic acid. Examples of metals of these fatty acid metal salts include zinc, iron, magnesium, aluminum, calcium, sodium, and lithium.

[0183] Examples of the silicone oil include dimethyl silicone oil, methylphenyl silicone oil, and amino-modified silicone oil.

[0184] Preferably, the hydrophobizing treatment is performed by adding a hydrophobizing agent to the particles to be treated in an amount of 1 to 30 mass % (more preferably 3 to 7 mass %) relative to the particles to be treated and coating the particles to be treated with the hydrophobizing agent.

[0185] The hydrophobization degree of the hydrophobized external additive is not particularly limited, but the hydrophobization degree after treatment is preferably, for example, 40 or more and 98 or less. The hydrophobization degree indicates the wettability of a sample to methanol and is an indicator of hydrophobicity.

[0186] When the toner of the present disclosure is mixed with a magnetic carrier and used as a two-component developer, satisfactory results are generally obtained when the mixing ratio with the carrier is 2 to 15% by mass, and preferably 4 to 13% by mass, as the toner concentration in the developer. When the toner concentration is less than 2% by mass, the image density tends to be easily reduced, and when the toner concentration exceeds 15% by mass, fogging and scattering in the device tend to occur easily.

[0187] In addition, when the replenishing developer is used to replenish the developing device in response to a decrease in the toner concentration of the two-component developer in the developing device, the amount of toner is 2 parts by mass or more and 50 parts by mass or less per 1 part by mass of the replenishing magnetic carrier.

[0188] Next, an image forming apparatus equipped with a developing apparatus using the magnetic carrier, two-component developer, and replenishing developer according to the present disclosure will be described with reference to an embodiment, but the developing apparatus used in the developing method of the present disclosure is not limited thereto.

[0189] <Measurement of Specific Resistance of Magnetic Carrier>

[0190] use Figure 4A and Figure 4B The specific resistance of the magnetic carrier and the porous magnetic core was measured using the measuring apparatus shown in For reference, the specific resistance of the magnetic carrier was measured at an electric field intensity of 2000 (V / cm).

[0191] The resistance measuring element A has a cross-sectional area of ​​2.4 cm 2 A cylindrical container (made of PTFE resin) 17 with a hole, a lower electrode (made of stainless steel) 18, a support base (made of PTFE resin) 19, and an upper electrode (made of stainless steel) 20 are provided. The cylindrical container 17 is placed on the support base 19, and a sample (magnetic carrier or porous magnetic core) 21 is loaded therein so that the thickness becomes about 1 mm; and the upper electrode 20 is placed on the loaded sample 21, and the thickness of the sample is measured. Figure 4A As shown in , d1 represents the gap when there is no sample, and as Figure 4B As shown in , d2 represents the gap when the sample is loaded so that the thickness becomes approximately 1 mm; then, the thickness d of the sample is calculated by the following expression:

[0192] d=d2-d1(mm).

[0193] At this time, the mass of the sample is appropriately changed so that the thickness d of the sample becomes 0.95 mm or more and 1.04 mm or less.

[0194] The specific resistance of the sample can be determined by applying a DC voltage between electrodes and measuring the current flowing at that time. For the measurement, an electrometer 22 (Keithley 6517A, manufactured by Keithley Instruments & Products) and a processing computer 23 for control are used.

[0195] As a processing computer for control, a control system manufactured by National Instruments and control software (LabVEIW manufactured by National Instruments Corp.) were used.

[0196] As the measurement condition, the contact area S between the sample and the electrode was input, which was 2.4 cm 2 , and the value d that has been measured, so that the thickness of the sample becomes 0.95 mm or more and 1.04 mm or less. In addition, the load of the upper electrode is determined to be 270 g, and the maximum applied voltage is determined to be 1000 V.

[0197] Specific resistance (Ω·cm) = (applied voltage (V) / measured current (A)) × S (cm 2 ) / d(cm)

[0198] Electric field strength (V / cm) = applied voltage (V) / d (cm)

[0199] The specific resistance of the magnetic carrier and the porous magnetic core under the electric field strength can be read from the graph by reading the specific resistance under the electric field strength on the graph.

[0200] <Method for measuring volume-based 50% diameter (D50) of magnetic carrier and porous magnetic core>

[0201] The particle size distribution is measured with a laser diffraction / scattering type particle size distribution measuring apparatus "Microtrac MT3300EX" (manufactured by Nikkiso Co., Ltd.).

[0202] The 50% diameter (D50) based on volume of the magnetic carrier and the porous magnetic core was measured using a particle size distribution measuring device equipped with a sample feeder "disposable dry sample conditioner Turbotrac" (manufactured by Nikkiso Co., Ltd.) for dry measurement. Regarding the supply conditions in the Turbotrac, a dust collector was used as a vacuum source, wherein the air volume was set to about 33 l / sec and the pressure was set to about 17 kPa. Control was automatically performed on the software. As the particle size, the 50% particle size (D50) as the cumulative value of the volume distribution was determined. Control and analysis were performed using the attached software (version 10.3.3-202D). The measurement conditions were as follows.

[0203] SetZero time: 10 seconds

[0204] Measuring time: 10 seconds

[0205] Number of measurements: once

[0206] Particle refractive index: 1.81%

[0207] Particle shape: non-spherical

[0208] Measuring upper limit: 1408μm

[0209] Measurement lower limit: 0.243μm

[0210] Measurement environment: 23°C, 50% RH

[0211] <Measurement of Pore Diameter and Pore Volume of Porous Magnetic Core>

[0212] The pore size distribution of the porous magnetic core is measured by mercury intrusion porosimetry.

[0213] The measurement principle is as follows.

[0214] In this measurement, the pressure applied to mercury is varied, and the amount of mercury intruding into the pores is measured. The condition under which mercury can intrude into the pores can be expressed by the equilibrium power as PD = -4σCOSθ, assuming that pressure, pore diameter, mercury contact angle, and surface tension are represented by P, D, θ, and σ, respectively. When the contact angle and surface tension are constant, the pressure P is inversely proportional to the pore diameter D through which mercury can intrude. Therefore, the pore distribution is determined by measuring the pressure P and the amount of intruding liquid V at that time, while varying the pressure to obtain a PV curve. In this expression, the horizontal axis P of the curve is directly replaced by the pore diameter.

[0215] The pore size distribution can be measured by using, as a measuring apparatus, a fully automatic multifunctional mercury porosimeter PoreMaster series or PoreMaster-GT series manufactured by Yuasa IONICS, or an automatic porosimeter AutoPore IV9500 series manufactured by Shimadzu Corporation.

[0216] Specifically, the pore size distribution is measured using AutoPore IV 9520 manufactured by Shimadzu Corporation Co., Ltd. under the following conditions and procedures.

[0217] Measurement conditions

[0218]

[0219] (The number of steps is formed so that the intervals are equal when the aperture is taken logarithmically.)

[0220]

[0221] Measurement steps

[0222] (1) Weigh approximately 1.0 g of the porous magnetic core and place it in the sample chamber.

[0223] Enter the weighed value.

[0224] (2) The range of 2.0 psia (13.8 kPa) or more and 45.8 psia (315.6 kPa) or less is measured in the low-pressure portion.

[0225] (3) The range of 45.9 psia (316.3 kPa) or more and 59989.6 psia (413.6 MPa) is measured in the high pressure section.

[0226] (4) Calculate the pore size distribution from the mercury injection pressure and mercury injection volume.

[0227] Steps (2), (3) and (4) are automatically performed by the software attached to the device.

[0228] The pore diameter at which the differential pore volume becomes locally maximum is determined by reading the pore diameter at which the differential pore volume becomes maximum within the pore diameter range of 0.1 μm or more and 3.0 μm or less from the pore diameter distribution measured as above and employing the pore diameter.

[0229] In addition, the pore volume obtained by integrating the differential pore volume within the range of pore diameters of 0.1 μm or more and 3.0 μm or less was calculated using attached software.

[0230] <Method for measuring weight average particle size (D4) and number average particle size (D1)>

[0231] The weight-average particle diameter (D4) and number-average particle diameter (D1) of the toner are measured according to the pore resistance method using a precision particle size distribution measuring apparatus "Coulter Counter Multisizer 3" (registered trademark, manufactured by Beckman Coulter, Inc.) equipped with a 100 μm aperture, and attached dedicated software "Beckman Coulter Multisizer 3 Version 3.51" (manufactured by Beckman Coulter, Inc.) for setting measurement conditions and analyzing measurement data. The particle diameter is measured with an effective measurement channel number of 25,000 channels and is calculated after analyzing the measurement data.

[0232] As the aqueous electrolyte solution for measurement, a solution prepared by dissolving special grade sodium chloride in ion exchange water so as to have a concentration of about 1% by mass, for example, "ISOTON II" (manufactured by Beckman Coulter, Inc.) can be used.

[0233] For reference, before performing measurement and analysis, the dedicated software is set in the following manner.

[0234] In the "Change Standard Operating Method (SOM) Screen" of the dedicated software, set the total count in control mode to 50,000 particles, the number of measurements to 1, and the Kd value to the value obtained using "Standard Particles 10.0 μm" (produced by Beckman Coulter, Inc.). The threshold and noise level were automatically set by pressing the Threshold / Noise Level Measurement button. Additionally, set the current to 1600 μA, the gain to 2, the electrolyte solution to ISOTON II, and check the "Post-measurement Orifice Tube Flush" checkbox.

[0235] In the "Set Pulse to Size Conversion" screen of the dedicated software, set the element spacing to logarithmic size, the size elements to 256 size elements, and the size range to a value from 2 μm to 60 μm.

[0236] The specific measurement method is as follows.

[0237] (1) Place approximately 200 ml of the above electrolyte aqueous solution into a 250 mL glass round-bottom beaker for the Multisizer 3. Place the beaker on the sample stage and stir the solution by rotating the stirring rod counterclockwise at 24 rpm. Then, use the "Tip Flush" function in the analysis software to remove dirt and bubbles from the tip.

[0238] (2) An electrolyte aqueous solution in an amount of approximately 30 ml was placed in a 100 mL glass flat-bottom beaker. Approximately 0.3 ml of a dilution solution of "Contaminon N" (a 10% by mass aqueous solution of a neutral detergent for cleaning precision measuring instruments composed of a nonionic surfactant, an anionic surfactant, and an organic builder having a pH of 7 and manufactured by Wako Pure Chemical Industries, Ltd.) was added to the aqueous solution as a dispersant. The solution was diluted to three times its mass with ion-exchanged water.

[0239] (3) A predetermined amount of ion-exchanged water was placed in a water tank of an ultrasonic dispersing device "Ultrasonic Dispersion System Tetora 150" (manufactured by Nikkaki Bios Co., Ltd.), which has two oscillators with an oscillation frequency of 50 kHz, a phase shift of 180°, and a power output of 120 W. Approximately 2 ml of Contaminon N was added to the water tank.

[0240] (4) Place the beaker in (2) in the beaker fixing hole of the ultrasonic dispersing device and start the ultrasonic dispersing device. Then, adjust the height of the beaker so that the liquid surface resonance state of the electrolyte aqueous solution in the beaker becomes the maximum.

[0241] (5) While the electrolyte aqueous solution in the beaker (4) is being irradiated with ultrasonic waves, approximately 10 mg of the toner is added little by little to the electrolyte aqueous solution and dispersed therein. The ultrasonic dispersion treatment is then continued for another 60 seconds. For reference, during the ultrasonic dispersion, the water temperature in the water tank is appropriately adjusted to 10°C or higher and 40°C or lower.

[0242] (6) Using a pipette, add the aqueous electrolyte solution containing the toner dispersed therein in (5) dropwise to the round-bottom beaker placed on the sample stand in (1), and adjust the measurement concentration to approximately 5%. Then, continue measuring until the number of particles measured reaches 50,000.

[0243] (7) The measurement data is analyzed using the dedicated software included with the device, and the weight-average particle size (D4) and number-average particle size (D1) are calculated. For reference, when the dedicated software is set to Graph / Volume %, the "Average Diameter" on the Analysis / Volume Statistics (Arithmetic Average) screen is the weight-average particle size (D4), and when the dedicated software is set to Graph / Number %, the "Average Diameter" on the Analysis / Number Statistics (Arithmetic Average) screen is the number-average particle size (D1).

[0244] <Calculation Method of Fine Powder Amount>

[0245] The amount of the fine powder in the toner on a number basis (number %) is calculated in the following manner.

[0246] For example, after measurement with the Multisizer 3, the number % of particles with a size of 4.0 μm or less in the toner is determined by the following steps: (1) setting the screen to Graph / Number % in the dedicated software and making the graph of the measurement results displayed as Number %; (2) checking "<" in the Particle Size Setting section on the Format / Particle Size / Particle Size Statistics screen, and entering "4" in the Particle Size Input section below the Particle Size Setting section; and (3) reading the value of "<4 μm" in the display section when the Analysis / Number Statistics (Arithmetic Mean) screen is displayed, and adopting this value as the number % of particles with a size of 4.0 μm or less in the toner.

[0247] <Calculation Method of Coarse Powder Amount>

[0248] The amount of the coarse powder in the toner on a volume basis (volume %) is calculated in the following manner.

[0249] For example, after measurement with the Multisizer 3, the volume % of particles with a size of 10.0 μm or larger in the toner is determined by the following steps: (1) setting the screen to Graph / Volume % in the dedicated software and making the graph of the measurement results displayed as volume %; (2) checking ">" in the particle size setting section on the Format / Particle Size / Particle Size Statistics screen, and entering "10" in the particle size input section below the particle size setting section; and (3) displaying the Analysis / Volume Statistics (Arithmetic Mean) screen, reading out the value of ">10 μm" in the displayed section at this time, and adopting this value as the volume % of particles with a size of 10.0 μm or larger in the toner.

[0250] <X-ray Diffraction Analysis of Powder>

[0251] The XRD pattern was measured using an X-ray diffraction analysis apparatus (X'pert PRO-MPD: manufactured by PANalytical).

[0252] X-rays were generated at an accelerating voltage of 45 kV and a current of 40 mA.

[0253] The X-rays of the powder were measured under the following measurement conditions.

[0254] Divergence slit: 1 / 4rad (fixed)

[0255] Anti-scattering slit: 1 / 2rad

[0256] Soller slit: 0.04 rad

[0257] Shield: 15mm

[0258] Anti-scatter slit: 7.5mm

[0259] Rotator: exists

[0260] Measurement method Scanning axis: Continuous 2θ / θ

[0261] Measuring range: 5.0°≤2θ≤80°

[0262] Step distance: 0.026 degrees / s

[0263] Scanning speed: 0.525 degrees / s

[0264] For reference, as a sample for measurement of P70, by using the same recipe as the porous ferrite core material and changing the oxygen concentration during the firing process at the time of production, a sample in which the magnetization intensity when an external magnetic field of 5000 / 4π (kA / m) is adjusted to 70 Am 2 / kg of particles.

[0265] <Method for Measuring Magnetization Intensity of Magnetic Core>

[0266] The magnetization of the magnetic core can be determined by a vibrating magnetic field type magnetic property measuring apparatus (vibrating sample magnetometer) or a DC magnetic property recording apparatus (BH tracer). In the examples described later, the magnetization was measured according to the following procedure using a vibrating magnetic field type magnetic property measuring apparatus BHV-30 (manufactured by Riken Denshi Co., Ltd.).

[0267] The sample should be a cylindrical plastic container that has been tightly packed with magnetic cores. The actual mass of the sample in the container should be measured. The sample in the plastic container should then be bonded with a temporary adhesive to prevent it from moving.

[0268] The external magnetic field axis and magnetic moment axis were calibrated using a standard sample at 5000 / 4π (kA / m).

[0269] The magnetization intensity was measured from the magnetic moment loop obtained when an external magnetic field of 5000 / 4π (kA / m) was applied to the sample at a scanning speed of 5 (min / revolution). 2 / kg) was obtained by dividing the value obtained by these steps by the sample weight.

[0270] <Toner Production Method>

[0271] The method for producing toner particles is not particularly limited, but a pulverization method is preferred from the perspective of dispersion of the release agent or the polymer in which a styrene-acrylic acid polymer is graft-polymerized onto a polyolefin. This is because when toner particles are produced in an aqueous medium, the release agent or the polymer in which a styrene-acrylic acid polymer is graft-polymerized onto a polyolefin, which has high hydrophobicity, tends to be easily localized inside the toner particles; as a result, it is difficult for the toner particles to form a core-shell structure by the above-mentioned heat treatment equipment.

[0272] The steps of producing the toner by the pulverization method will be described below.

[0273] In the raw material mixing step, predetermined amounts of constituent materials of the toner particles, such as a binder resin, a release agent, a colorant, a crystalline polyester, and, as needed, other components such as a charge control agent, are weighed, blended, and mixed. Examples of mixing equipment include a double cone mixer, a V-type mixer, a drum mixer, a super mixer, a Henschel mixer, a Nauta mixer, and a Mechano-Hybrid (manufactured by Nippon Coke & Engineering Co., Ltd.).

[0274] Next, the mixed materials are melt-kneaded, and the wax and the like are dispersed in the binder resin. In the melt-kneading step, intermittent kneading machines such as a pressure kneading machine and a Banbury mixer, and continuous kneading machines can be used; and single-screw or twin-screw extruders are mainly used because of their superior continuous production capacity. Examples of equipment include: KTK type twin-screw extruder (manufactured by Kobe Steel, Ltd.); TEM type twin-screw extruder (manufactured by Toshiba Machine Co., Ltd.); PCM kneader (manufactured by Ikegai Corp.); twin-screw extruder (manufactured by KGK Co., Ltd.); co-kneader (manufactured by Buss Inc.); and Kneadex (manufactured by Nippon Coke & Engineering Co., Ltd.). In addition, the resin composition obtained by melt-kneading can be rolled with a double-roll mill or the like, and cooled with water or the like in the cooling step.

[0275] Next, the cooled product of the resin composition is pulverized to a desired particle size in a pulverizing step. In the pulverizing step, for example, the cooled product is coarsely pulverized by a pulverizer such as a crusher, a hammer mill, or a feather mill, and thereafter, the resulting product is further finely pulverized by, for example, a Kryptron system (manufactured by Kawasaki Heavy Industries, Ltd.), a super rotor (manufactured by Nisshin Engineering Inc.), a turbo mill (manufactured by Turbo Kogyo Co., Ltd.), or a jet-type fine pulverizer.

[0276] Thereafter, the obtained product is classified as needed using a classifier or sifter such as an inertial classification type elbow ejector (manufactured by Nittetsu Mining Co., Ltd.), a centrifugal classification type Turboplex (manufactured by Hosokawa Micron Corporation), a TSP separator (manufactured by Hosokawa Micron Corporation), or a Faculty (manufactured by Hosokawa Micron Corporation).

[0277] Thereafter, the toner particles are surface treated by heating and the circularity of the toner is increased. For example, Figure 1 The surface treatment apparatus shown in performs surface treatment on toner particles by hot air.

[0278] The mixture quantitatively supplied by the raw material quantitative supply unit 101 is guided into an introduction pipe 103 installed on a vertical line of the raw material supply unit by compressed gas regulated by a compressed gas regulating unit 102. The mixture that has passed through the introduction pipe is uniformly dispersed by a conical protrusion-shaped member 104 provided in the central portion of the raw material supply unit and guided into a processing chamber 106, where the mixture is heat-treated by guiding it through supply pipes 105 that radially expand in eight directions.

[0279] At this time, the flow of the mixture supplied to the processing chamber is regulated by the regulating unit 109 provided in the processing chamber for regulating the flow of the mixture. Therefore, the mixture supplied to the processing chamber is heat-treated while swirling in the processing chamber and then cooled.

[0280] Hot air for heat-treating the supplied mixture is supplied from the hot air supply unit 107, and the hot air is spirally swirled by the vortex member 113 for swirling the hot air, and is introduced into the processing chamber. Regarding its structure, the vortex member 113 for swirling the hot air has a plurality of blades, and the swirl of the hot air can be controlled by the number and angle of the blades. Preferably, the temperature of the hot air supplied to the processing chamber at the outlet portion of the hot air supply unit 107 is 100°C to 300°C. When the temperature at the outlet portion of the hot air supply unit is within the above range, the hot air can uniformly spheroidize the toner particles while preventing the toner particles from fusing and agglomerating due to excessive heating of the mixture.

[0281] Furthermore, the heat-treated toner particles are cooled by the cold air supplied from the cold air supply units 108-1, 108-2, and 108-3; and preferably, the temperature of the cold air supplied from the cold air supply units 108-1, 108-2, and 108-3 is respectively -20°C to 30°C. When the temperature of the cold air is within the above range, the cold air can effectively cool the heat-treated toner particles and can prevent fusion and agglomeration of the heat-treated toner particles without hindering uniform sphericalization of the mixture. Preferably, the absolute moisture content of the cold air is 0.5 g / m 3 Above and 15.0g / m 3 the following.

[0282] Next, the cooled heat-treated toner particles are collected by the collecting unit 110 present at the lower end of the process chamber. For reference, at the front end of the collecting unit, a blower (not shown) configured to suck and transport the toner particles is provided.

[0283] In addition, the powder particle supply port 114 is provided so that the vortex direction of the supplied mixture and the vortex direction of the hot air become the same direction, and the collection unit 110 of the surface treatment device is provided on the periphery of the treatment chamber so as to maintain the vortex direction of the vortex powder particles. In addition, the cold air supply unit 8 is configured so that the cold air supplied therefrom is supplied from the periphery of the device to the inner peripheral surface of the treatment chamber in the horizontal and tangential directions. The vortex direction of the toner supplied from the powder supply port, the vortex direction of the cold air supplied from the cold air supply port, and the vortex direction of the hot air supplied from the hot air supply unit are all in the same direction. Therefore, no turbulence occurs in the treatment chamber, the vortex flow in the device is strengthened, a strong centrifugal force is applied to the toner, and the dispersibility of the toner is further improved, so that a toner with almost no agglomerated particles and uniform shape can be obtained.

[0284] From the viewpoint of fogging properties, it is preferable that the average circularity of the toner is 0.960 or more and 0.980 or less, because the toner can reduce the non-electrostatic adhesive force to a low level.

[0285] Thereafter, the toner particles are divided into two parts, a fine powder side and a coarse powder side. For example, an inertial classification type elbow ejector (manufactured by Nittetsu Mining Co., Ltd.) is used to divide the toner particles into two parts. A desired amount of silica particles A is externally added to each surface of the heat-treated toner particles that have been divided into two. Examples of methods for external addition treatment include methods for stirring and mixing the toner particles by using, for example, a double cone mixer, a V-type mixer, a drum mixer, a super mixer, a Henschel mixer, a Nauta mixer, a Mechano-Hybrid (Nippon Coke & Engineering Co., Ltd.), and a Nobilta (Hosokawa Micron Corporation) mixing device as an external addition machine. At this time, as needed, it is acceptable to use external additives other than silica particles, such as a fluidizing agent, for external addition treatment.

[0286] Methods of measuring various physical properties of the toner and raw materials will be described below.

[0287] Example

[0288] <Production Example of Porous Magnetic Core Particles>

[0289] Step 1 (weighing and mixing step)

[0290]

[0291] The ferrite raw material is weighed so as to satisfy the above mass.

[0292] Thereafter, the mixture was pulverized and mixed for 2 hours by a dry ball mill using zirconia balls (φ10 mm).

[0293] Step 2 (pre-baking step)

[0294] After pulverization and mixing, the mixture was baked at 950° C. for 2 hours under atmosphere using a burner type baking furnace, and pre-baked ferrite was produced. The composition of the ferrite was as follows.

[0295] (MnO) a (MgO) b (SrO) c (Fe2O3) d

[0296] In the above formula, the subscripts are a = 0.40, b = 0.07, c = 0.01, and d = 0.52.

[0297] Step 3 (crushing step)

[0298] The produced pre-baked ferrite was crushed to about 0.5 mm with a crusher, and then 30 parts by mass of water was added to 100 parts by mass of the pre-baked ferrite, and the mixture was pulverized for 2 hours in a wet ball mill using zirconia balls (φ1.0 mm). After separating the balls, the resulting mixture was pulverized for 3 hours in a wet ball mill using zirconia beads (φ1.0 mm) to obtain a ferrite slurry.

[0299] Step 4 (granulation step)

[0300] To the ferrite slurry, 2.0 parts by mass of polyvinyl alcohol was added as a binder relative to 100 parts by mass of the pre-baked ferrite, and the mixture was granulated into spherical particles of 40 μm using a spray dryer (manufacturer: Ohkawara Kakohki Co., Ltd.).

[0301] Step 5 (Main Firing Step)

[0302] In order to control the firing atmosphere, the spherical particles were fired at 1150° C. for 4 hours in a nitrogen atmosphere (oxygen concentration: 1.0 volume %) in an electric furnace.

[0303] Step 6 (Screening Step)

[0304] The aggregated particles were pulverized, and the resulting particles were sieved with a mesh having an opening of 250 μm to remove coarse particles and obtain porous magnetic core particles, which are referred to as magnetic core 1. The physical properties of the obtained magnetic core 1 are shown in Table 1.

[0305] Step 7 (resin filling step)

[0306] 100.0 parts by mass of the magnetic core 1 was placed in a stirring container of a mixing stirrer (general-purpose stirrer NDMV type manufactured by Dalton Corporation), while maintaining the temperature at 60°C and simultaneously reducing the pressure to 2.3 kPa, nitrogen was introduced, and the silicone resin solution was added dropwise to the magnetic core 1 under reduced pressure so that the resin component became 7.5 parts by mass, and after the dropwise addition was completed, stirring was continued in this state for 2 hours. Thereafter, the temperature was raised to 70°C, thereby removing the solvent under reduced pressure, and the particles of the magnetic core 1 were filled with the silicone resin composition obtained from the silicone resin solution. After cooling, the obtained filled magnetic core particles were transferred to a mixer having a spiral blade in a rotatable mixing container (drum mixer UD-AT type manufactured by Sugiyama Heavy Industrial Co., Ltd.), and heated to 220°C at a rate of 2 (°C / min) under a nitrogen atmosphere and atmospheric pressure. The resulting magnetic core particles were heated and stirred at this temperature for 60 minutes, and the resin was cured. After the heat treatment, low magnetic core particles were separated by magnetic separation, the obtained core particles were classified with a mesh having an opening of 150 μm, and Magnetic Core 2 was obtained. The physical properties of the obtained Magnetic Core 2 are shown in Table 1.

[0307] <Production Example of Ferrite Core Particles>

[0308] Step 1 (weighing and mixing step)

[0309]

[0310] The above ferrite raw materials are weighed so as to satisfy the above-mentioned mass.

[0311] Thereafter, the mixture was pulverized and mixed for 2 hours by a dry ball mill using zirconia balls (φ10 mm).

[0312] Step 2 (pre-baking step)

[0313] After pulverization and mixing, the mixture was baked at 1000° C. for 2 hours under atmosphere using a burner type baking furnace, and pre-baked ferrite was produced. The composition of the ferrite was as follows.

[0314] (MnO) a (MgO) b (SrO) c (Fe2O3) d

[0315] In the above formula, the subscripts are a = 0.40, b = 0.07, c = 0.01, and d = 0.52.

[0316] Step 3 (crushing step)

[0317] The produced pre-baked ferrite was crushed to about 0.5 mm with a crusher, and then 30 parts by mass of water was added to 100 parts by mass of the pre-baked ferrite, and the mixture was pulverized for 2 hours in a wet ball mill using stainless steel balls (φ1.0 mm). After separating the balls, the resulting mixture was pulverized for 3 hours in a wet bead mill using stainless steel balls (φ1.0 mm), and a ferrite slurry was obtained.

[0318] Step 4 (granulation step)

[0319] To the ferrite slurry, 2.0 parts by mass of polyvinyl alcohol was added as a binder relative to 100 parts by mass of the pre-baked ferrite, and the mixture was granulated into spherical particles of 45 μm using a spray dryer (manufacturer: Ohkawara Kakohki Co., Ltd.).

[0320] Step 5 (Main Firing Step)

[0321] In order to control the firing atmosphere, the spherical particles were fired at 1200° C. for 6 hours in a nitrogen atmosphere (oxygen concentration: 0.6% by volume) in an electric furnace.

[0322] Step 6 (Screening Step)

[0323] The aggregated particles were crushed, and then the obtained particles were sieved with a mesh having an opening of 250 μm to remove coarse particles, thereby obtaining ferrite core particles, which are referred to as magnetic core 3. The physical properties of the obtained magnetic core 3 are shown in Table 1.

[0324] <Production Example of Magnetic Material Dispersed Resin Core Particles>

[0325] Magnetite particles and a silane coupling agent (3-(2-aminoethylaminopropyltrimethoxysilane) (in an amount of 3.0% by mass relative to the mass of the magnetite particles) were introduced into a container, wherein the magnetite particles had a spherical shape, a number average particle size of 250 nm, and a saturation magnetization of 50 (Am 2 / kg), the residual magnetization is 4.2(Am 2 / kg), a coercive force of 4.4 (kA / m), and a specific resistance of 3.3×10 at 1000 (V / cm). 6 (Ω·cm) Then, the mixture is mixed and stirred at a high speed at a temperature of 100° C. or higher in a container, thereby surface-treating the magnetite fine particles.

[0326] 10 parts by mass of phenol

[0327] Formaldehyde solution (37% formaldehyde aqueous solution) 16 parts by mass

[0328] 84 parts by mass of the surface-treated magnetite particles

[0329] The above materials were introduced into a reaction vessel and mixed thoroughly at a temperature of 40°C.

[0330] The mixture was then heated to 85°C while stirring at an average heating rate of 3°C / minute, and 4 parts by mass of 28% by mass ammonia water and 25 parts by mass of water were added to the reaction vessel. The resulting mixture was maintained at 85°C and subjected to polymerization for 3 hours to cure. The peripheral speed of the stirring blade was 1.8 m / second.

[0331] After the polymerization reaction, the resulting mixture was cooled to a temperature of 30°C and water was added thereto. The supernatant was removed, and the obtained precipitate was washed with water and further air-dried. The obtained air-dried product was dried at a temperature of 60°C under reduced pressure (5 hPa or less) to obtain magnetic material dispersed resin core particles. This is referred to as magnetic core 4.

[0332] Table 1 shows the physical properties of the obtained magnetic core 4.

[0333] [Table 1]

[0334]

[0335] <Production Example of Resin A1>

[0336] A silicone-containing acrylic monomer corresponding to Unit Y1 (described below) at 95.2% by mass and a monomer corresponding to Unit Y2 at 4.8% by mass were added to a four-necked flask equipped with a reflux cooler, a thermometer, a nitrogen inlet tube, and a stirring device. The compositions of Unit Y1 and Unit Y2 are shown in Table 2.

[0337] Furthermore, 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 a mixed solution of 106 parts by mass of the above monomers. The resulting mixture was maintained at 70°C for 10 hours under a nitrogen stream. After the polymerization reaction was completed, the mixture was repeatedly washed to obtain a resin A1 solution (solid content: 35% by mass). The 1+m value of this solution, as calculated by gel permeation chromatography (GPC), was 70.

[0338] <Production Example of Resins A2 to A26>

[0339] Resins A2 to A26 were obtained in the same manner as in the production method of Resin A1, except that the compositions of Unit Y1 and Unit Y2 and the values ​​of a, b, n, and l+m were changed as shown in Table 2-1 and Table 2-2.

[0340] [Table 2-1]

[0341]

[0342]

[0343] [Table 2-2]

[0344]

[0345] <Macromeremonomer Production Method>

[0346] The macromonomer used in the resin B can be synthesized, for example, by the following method.

[0347] The raw materials shown below were added to a four-necked flask equipped with a reflux cooler, a thermometer, a nitrogen inhalation tube, and an equipped stirring device.

[0348] Methacryloyl chloride...1.7% by mass

[0349] Polymethyl methacrylate having a hydroxyl group at one end (Mw; about 5000) ... 98.3% by mass

[0350] Furthermore, 100 parts by mass of THF and 1.0 part by mass of 4-tert-butylcatechol were added to 100 parts by mass of the above-mentioned monomer mixed liquid, and the resulting mixture was heated and refluxed under a nitrogen stream for 5 hours; and after the reaction was completed, the resulting liquid was washed with sodium bicarbonate, and then, a solution of the macromonomer methacrylate was obtained.

[0351] <Production Method of Resin B1>

[0352] The monomers shown below were added to a four-necked flask equipped with a reflux cooler, a thermometer, a nitrogen inhalation tube, and an equipped stirring device.

[0353] Cyclohexyl methacrylate...74.5% by mass

[0354] Methyl methacrylate: 0.5% by mass

[0355] Macromonomer methacrylate...25% by mass

[0356] Furthermore, 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 a mixed solution of 106 parts by mass of the above monomers. The resulting mixture was maintained at 70°C for 10 hours under a nitrogen stream. After the polymerization reaction was completed, the mixture was repeatedly washed to obtain a Resin B1 solution (solid content: 35% by mass). The weight average molecular weight of this solution as determined by gel permeation chromatography (GPC) was 57,000. SPb was 10.2.

[0357] <Production Method of Resin B2>

[0358] The monomers shown below were added to a four-necked flask equipped with a reflux cooler, a thermometer, a nitrogen inhalation tube, and an equipped stirring device.

[0359] Cyclohexyl methacrylate...74.5% by mass

[0360] Methyl methacrylate...25.5% by mass

[0361] Furthermore, 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 a mixed solution of 106 parts by mass of the above monomers. The resulting mixture was maintained at 70°C for 10 hours under a nitrogen stream. After the polymerization reaction was completed, the mixture was repeatedly washed to obtain a resin B2 solution (solid content: 35% by mass). The weight average molecular weight of this solution as determined by gel permeation chromatography (GPC) was 68,000. SPb was 10.2.

[0362] <Production Method of Resin B3>

[0363] The monomers shown below were added to a four-necked flask equipped with a reflux cooler, a thermometer, a nitrogen inhalation tube, and an equipped stirring device.

[0364] ·Methyl methacrylate...75% by mass

[0365] Macromonomer methacrylate...25% by mass

[0366] Furthermore, 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 a mixed solution of 106 parts by mass of the above monomers. The resulting mixture was maintained at 70°C for 10 hours under a nitrogen stream. After the polymerization reaction was completed, the mixture was repeatedly washed to obtain a resin B3 solution (solid content: 35% by mass). The weight average molecular weight of this solution as determined by gel permeation chromatography (GPC) was 35,000. SPb was 9.9.

[0367] <Production Method of Resin B4>

[0368] The monomers shown below were added to a four-necked flask equipped with a reflux cooler, a thermometer, a nitrogen inhalation tube, and an equipped stirring device.

[0369] Cyclohexyl methacrylate...30% by mass

[0370] ·Methyl methacrylate...45% by mass

[0371] Macromonomer methacrylate...25% by mass

[0372] Furthermore, 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 a mixed solution of 106 parts by mass of the above monomers. The resulting mixture was maintained at 70°C for 10 hours under a nitrogen stream. After the polymerization reaction was completed, the mixture was repeatedly washed to obtain a resin B4 solution (solid content: 35% by mass). The weight average molecular weight of this solution as determined by gel permeation chromatography (GPC) was 36,000. SPb was 10.1.

[0373] <Production Method of Resin B5>

[0374] The monomers shown below were added to a four-necked flask equipped with a reflux cooler, a thermometer, a nitrogen inhalation tube, and an equipped stirring device.

[0375] · Hexyl methacrylate...100% by mass

[0376] Furthermore, 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 a mixed solution of 106 parts by mass of the above monomers. The resulting mixture was maintained at 70°C for 10 hours under a nitrogen stream. After the polymerization reaction was completed, the mixture was repeatedly washed to obtain a resin B5 solution (solid content: 35% by mass). The weight average molecular weight of this solution as determined by gel permeation chromatography (GPC) was 48,000. The SPb was 9.3.

[0377] <Production Method of Resin B6>

[0378] The monomers shown below were added to a four-necked flask equipped with a reflux cooler, a thermometer, a nitrogen inhalation tube, and an equipped stirring device.

[0379] ·2-Hydroxyethyl methacrylate...35.4% by mass

[0380] Methyl methacrylate...64.6% by mass

[0381] Furthermore, 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 a mixed solution of 106 parts by mass of the above monomers. The resulting mixture was maintained at 70°C for 10 hours under a nitrogen stream. After the polymerization reaction was completed, the mixture was repeatedly washed to obtain a resin B6 solution (solid content: 35% by mass). The weight average molecular weight of this solution as determined by gel permeation chromatography (GPC) was 37,000. The SPb was 11.4.

[0382] <Production Method of Resin B7>

[0383] The monomers shown below were added to a four-necked flask equipped with a reflux cooler, a thermometer, a nitrogen inhalation tube, and an equipped stirring device.

[0384] Polydimethylsiloxane (average degree of polymerization: 55) 5.0 parts by mass

[0385] 25.0 parts by mass of methyltrichlorosilane

[0386] 40.0 parts by mass of water

[0387] 30.0 parts by mass of methyl isobutyl ketone

[0388] Of the above materials, water and methyl isobutyl ketone were placed in a reaction vessel equipped with a reflux condenser, a dropping funnel, and a stirrer. The mixture was stirred thoroughly to prevent the formation of two layers. Polydimethylsiloxane was then added, the resulting mixture further stirred, and the reaction vessel placed in an ice bath. When the temperature of the mixture in the reaction vessel reached 10°C, methyltrichlorosilane was added dropwise. After the addition was complete, the mixture was washed, and the solvent was evaporated under reduced pressure to obtain Resin B7. Its SPb was 10.2.

[0389] <Production Method of Resin B8>

[0390] The monomers shown below were added to a four-necked flask equipped with a reflux cooler, a thermometer, a nitrogen inhalation tube, and an equipped stirring device.

[0391] Hexyl methacrylate...10.0 mass%

[0392] Norbornene...90.0% by mass

[0393] Furthermore, 100 parts by mass of toluene, 100 parts by mass of methyl ethyl ketone, and 2 parts by mass of bis(dibenzylideneacetone)palladium were added to a mixed solution of 106 parts by mass of the above monomers. The resulting mixture was maintained at 70°C for 10 hours under a nitrogen stream. After the polymerization reaction was completed, the mixture was repeatedly washed to obtain a resin B8 solution (solid content: 35% by mass). The weight average molecular weight of this solution as determined by gel permeation chromatography (GPC) was 37,000. SPb was 12.0.

[0394] <Resin coating step>

[0395] ·Production method of magnetic carrier 1

[0396] The magnetic core 1 shown in Table 1 was used; a planetary mixer (Nauta Mixer VN manufactured by Hosokawa Micron Corporation) was maintained at 60°C under reduced pressure (1.5 kPa); and the resin solution containing Resin A and Resin B shown in Table 3 was charged into the mixer so that the solid content of the resin components became 2.0 parts by mass relative to 100 parts by mass of the magnetic core. Regarding the charging method, 1 / 3 of the resin solution was charged, and the solvent removal and coating operation was carried out for 20 minutes. Next, another 1 / 3 of the resin solution was charged, and the solvent removal and coating operation was carried out for 20 minutes; and another 1 / 3 of the resin solution was charged, and the solvent removal and coating operation was carried out for 20 minutes.

[0397] Thereafter, the magnetic carrier coated with the coating resin composition was transferred to a mixer (Drum Mixer UD-AT Model manufactured by Sugiyama Heavy Industrial Co., Ltd.) having a spiral blade in a rotatable mixing container. The magnetic carrier was heated at a temperature of 120° C. for 2 hours under a nitrogen atmosphere while stirring the mixing container at 10 revolutions per minute. The low-magnetic product was separated from the obtained magnetic carrier 1 by magnetic separation, and the remainder was passed through a mesh sieve with an opening of 150 μm and then classified by a wind classifier. A magnetic carrier 1 having a 50% particle size (D50) based on volume distribution of 39.1 μm was obtained.

[0398] Table 3 shows the surface analysis results of the obtained magnetic carrier 1.

[0399] ·Production method of magnetic carriers 2 to 40

[0400] Magnetic Carriers 2 to 40 were obtained by changing the magnetic core, and the resin A and the resin B in the coating resin solution to those shown in Table 3 in the production method of the above Magnetic Carrier 1. The physical properties are shown in Table 3.

[0401] [Table 3]

[0402]

[0403] <Production Example of Toner 1>

[0404] 100 parts by mass of polyester resin

[0405] Fischer-Tropsch wax (maximum endothermic peak temperature: 90°C) 4 parts by mass

[0406] · 3,5-di-tert-butylsalicylic acid aluminum compound (Bontron E88, manufactured by Orient Chemical Industry Co., Ltd.) 0.3 parts by mass

[0407] 10 parts by mass of carbon black

[0408] The above materials were mixed using a Henschel mixer (Model FM-75, manufactured by Nippon Coke & Engineering Co., Ltd.) at a rotation speed of 1500 rpm and a rotation time of 5 minutes, and then the mixture was kneaded using a twin-screw kneader (Model PCM-30, manufactured by Ikegai Corporation) set at a temperature of 130°C. The kneaded product obtained was cooled and coarsely pulverized to less than 1 mm by a hammer mill, and a coarsely pulverized product was obtained. The coarsely pulverized product obtained was finely pulverized using a mechanical pulverizer (T-250, manufactured by Turbo Kogyo Co., Ltd.). In addition, the finely pulverized product was classified using Faculty (F-300, manufactured by Hosokawa Micron Corporation), and toner base particles 1 were obtained. The operating conditions were set so that the rotation speed of the classification rotor was 11000 rpm and the rotation speed of the dispersion rotor was 7200 rpm.

[0409] Toner base particles 1 100 parts by mass

[0410] Silica fine particles A (number average particle size (D1) 120 nm) 2.0 parts by mass

[0411] The raw materials shown in the above formulation were mixed using a Henschel mixer (FM-10C, manufactured by Nippon Coke & Engineering Co., Ltd.) at a rotation number of 1900 rpm and a rotation time of 3 minutes, and then, Figure 1 The mixture was heat-treated using the surface treatment apparatus shown in , and heat-treated toner particles 1 were obtained. The operating conditions were set as follows: feed rate = 5 kg / hr, hot air temperature C = 160° C., hot air flow rate = 6 m 3 / minute, cold air temperature E = -5℃, cold air flow = 4m 3 / min, blower air volume = 20m 3 / min, and injection air flow rate = 1m 3 / minute.

[0412] The obtained heat-treated toner particles 1 are conditioned using an inertial classification type elbow ejector (manufactured by Nittetsu Mining Co., Ltd.) so that uniform heat-treated toner particles 1 can be obtained.

[0413] ·Heat-treated toner particles 1 100 parts by mass

[0414] Silica fine particles B (number average particle size (D1) 20 nm) 0.6 parts by mass

[0415] The above materials were mixed with a Henschel mixer (FM-75 model, manufactured by Mitsui Miike Chemical Engineering Machinery, Co., Ltd.) at a rotation number of 1900 rpm and a rotation time of 3 minutes, and Toner 1 was obtained.

[0416] <Example 1>

[0417] To 91 parts by mass of Magnetic Carrier 1, 9 parts by mass of Toner 1 was added, and the mixture was vibrated with a vibration machine (YS-8D model: manufactured by Yayoi Co., Ltd.), and 300 g of two-component developer 1 was prepared. The vibration amplitude condition of the vibration machine was 150 rpm for 2 minutes.

[0418] On the other hand, 90 parts by mass of Toner 1 is added to 10 parts by mass of Magnetic Carrier 1, and the mixture is mixed for 5 minutes with a V-type mixer under a room temperature and normal humidity environment of 23° C. and 50% RH, and Replenishing Developer 1 is obtained.

[0419] Two-component developer 1 and replenishing developer 1 were used to perform the following evaluations.

[0420] As the image forming apparatus, a modified version of the color copier imageRUNNER ADVANCE C5560 manufactured by Canon Marketing Japan Inc. was used.

[0421] The two-component developer was loaded into the developing device for each color, and a replenishing developer container in which the replenishing developer for each color was loaded was set; an image was formed, and various evaluations were performed before and after the durability test.

[0422] For the durability test, a chart with an image ratio of 1% and FFH output was used under a printing environment of 23°C and 5% relative humidity (hereinafter referred to as "N / L"). Furthermore, a chart with an image ratio of 40% and FFH output was used under a printing environment of 30°C and 80% relative humidity (hereinafter referred to as "H / H"). FFH is a value representing 256 grayscales in hexadecimal; 00h is the first grayscale (white background) of the 256 grayscales, and FFH is the 256th grayscale (solid area).

[0423] The number of output images is changed according to each evaluation item.

[0424] condition:

[0425] Paper: Laser beam printer paper CS-814 (81.4g / m 2 )

[0426] (Canon Marketing Japan Inc.)

[0427] The remodeled machine was remodeled so that it could output A4-size full-color images at an image forming speed of 80 (sheets / minute).

[0428] Development Conditions: The modified machine was modified to allow for arbitrary contrast adjustment, and automatic calibration was disabled. The modified machine was modified to maintain a peak-to-peak voltage (Vpp) of 2.0 kHz and to allow for adjustment from 0.7 kV to 1.8 kV in 0.1 kV increments. The modified machine was modified to output single-color images for each color.

[0429] Each evaluation item is shown below.

[0430] (1) Image density

[0431] Initial durability and durable image output evaluations were conducted in a high-temperature, high-humidity environment (30°C and 80% RH) (A4 landscape format, 40% print ratio, 50,000 sheets), after which a solid image (FFH) was output. Density was measured using a densitometer, X-Rite 404A (manufactured by X-Rite Incorporated), and the average of six points was taken as the image density. The difference in image density between initial durability and after durable image output was determined according to the following criteria. Evaluations of A to C were considered to indicate that the effects of the present disclosure had been achieved.

[0432] A: The concentration difference is less than 0.10.

[0433] B: The density difference is 0.10 or more and less than 0.15.

[0434] C: The density difference is 0.15 or more and less than 0.20.

[0435] D: The density difference is 0.20 or more and less than 0.25.

[0436] E: The density difference is 0.25 or more.

[0437] (2) Fogging

[0438] Initial durability and durable image output evaluations were conducted in a high-temperature, high-humidity environment (30°C and 80% RH) (A4 landscape orientation, 40% print ratio, 50,000 sheets). A completely solid white A4 image was then output. After calculating the whiteness of the white background portion using a reflectometer (manufactured by Tokyo Denshoku Co., Ltd.), fogging was evaluated according to the following criteria, and the fogging concentration (%) was calculated from the difference in whiteness before and after transfer. Evaluations of A to C determined that the effects of the present disclosure had been achieved.

[0439] A: less than 1.0%

[0440] B: 1.0% or more and less than 1.5%

[0441] C: 1.5% or more and less than 2.0%

[0442] D: 2.0% or more and less than 2.5%

[0443] E: 2.5% or more

[0444] (3) Halftone developability

[0445] Initial durability and durable image output evaluations were conducted in a high-temperature, high-humidity environment (30°C and 80% RH) (A4 landscape orientation, 40% print ratio, 50,000 sheets). 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-angle zoom lens VH-Z100, manufactured by Keyence Corporation). The number average (S) and standard deviation (σ) of the dot area were calculated, and the dot reproducibility index was calculated using the following expression. The roughness of the halftone image was then evaluated using the dot reproducibility index (I).

[0446] Point reproducibility index (I) = σ / S × 100

[0447] Regarding the evaluation criteria of the roughness, 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 disclosure had been obtained.

[0448] A: I is less than 4.0.

[0449] B: I is 4.0 or more and less than 5.0.

[0450] C: I is 5.0 or more and less than 6.0.

[0451] D:I is 7.0 or more and less than 8.0.

[0452] E:I is 8.0 or more.

[0453] (4) Scattering of toner

[0454] Initial durability and durable image output evaluations (A4 landscape, 40% print ratio, 50,000 sheets) were performed in a high-temperature, high-humidity environment (30°C and 80% RH). The developing device was then removed from the main body, and the toner scattering state inside and outside the developing device and the main body was visually observed. This state was evaluated according to the following criteria. When the evaluation was A to C, it was determined that the effects of the present disclosure had been achieved.

[0455] A: There is no toner scattering.

[0456] B: There is extremely slight toner scattering.

[0457] C: Slight toner scattering occurs.

[0458] D: Toner scattering occurs.

[0459] E: There is significant toner scattering.

[0460] The results obtained from the above evaluations (1) to (4) are shown in Table 5.

[0461] (Examples 2 to 33 and Comparative Examples 1 to 7)

[0462] Two-component developers 2 to 40 and replenishing developers 2 to 40 were prepared in the same manner as in Example 1, except that the magnetic carrier 1 in Example 1 was changed to magnetic carriers 2 to 40 as shown in Table 4, respectively; and similar evaluations (1) to (4) were performed.

[0463] The obtained results are shown in Table 5.

[0464] [Table 4]

[0465] Examples or Comparative Examples Two-component developer Replenishing developer Toner Magnetic carrier Example 1 1 1 1 1 Example 2 2 2 1 2 Example 3 3 3 1 3 Example 4 4 4 1 4 Example 5 5 5 1 5 Example 6 6 6 1 6 Example 7 7 7 1 7 Example 8 8 8 1 8 Example 9 9 9 1 9 Example 10 10 10 1 10 Example 11 11 11 1 11 Example 12 12 12 1 12 Example 13 13 13 1 13 Example 14 14 14 1 14 Example 15 15 15 1 15 Example 16 16 16 1 16 Example 17 17 17 1 17 Example 18 18 18 1 18 Example 19 19 19 1 19 Example 20 20 20 1 20 Example 21 21 21 1 21 Example 22 22 22 1 22 Example 23 23 23 1 23 Example 24 24 24 1 24 Example 25 25 25 1 25 Example 26 26 26 1 26 Example 27 27 27 1 27 Example 28 28 28 1 28 Example 29 29 29 1 29 Example 30 30 30 1 30 Example 31 31 31 1 31 Example 32 32 32 1 32 Example 33 33 33 1 33 Comparative Example 1 34 34 1 34 Comparative Example 2 35 35 1 35 Comparative Example 3 36 36 1 36 Comparative Example 4 37 37 1 37 Comparative Example 5 38 38 1 38 Comparative Example 6 39 39 1 39 Comparative Example 7 40 40 1 40

[0466] [Table 5]

[0467]

[0468] While the present disclosure has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments.The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.

Claims

1. A magnetic carrier comprising: A magnetic core; and a coating resin covering the surface of the magnetic core, characterized in that The coating resin includes resin A and resin B; The content of the resin A is 1 to 50% by mass, and the content of the resin B is 50 to 99% by mass relative to the total mass of the coating resin; The resin A has a unit Y1 represented by the following formula (1) and a unit Y2 represented by the following formula (2), and In the resin B, the content of the unit Y2 represented by the following formula (2) is 0.1% by mass or less; and When the mass of the resin A, the mass of the unit Y1 in the resin A, and the mass of the unit Y2 in the resin A are represented by X, a, and b, respectively, X, a, and b satisfy the following expressions (a) and (b): 0.90≤(a+b) / X≤1.00 (a), and 1.00≤a / b≤30.0 (b), and When the SP value of the unit Y1 and the SP value of the resin B are represented by SPa and SPb, respectively, the SPa and the SPb satisfy the following expression (c): 0≤|SPa-SPb|≤2.0 (c), In formula (1), R1 represents H or CH3, and R2 represents a hydrocarbon group having 1 to 8 carbon atoms and optionally has a substituent, wherein the substituent is a hydroxyl group or a carboxyl group; and In formula (2), R3 represents H or CH3, R4 represents H or CH3, R5 represents a single bond or a hydrocarbon group having 1 to 10 carbon atoms, R6 represents a hydrocarbon group having 1 to 10 carbon atoms, R7 represents H, CH3 or Si(CH3)3, and n represents an integer from 2 to 150, 2. The magnetic carrier according to claim 1, wherein The resin B includes 75% by mass or more of the unit Y1 represented by formula (1). 3 . The magnetic carrier according to claim 1 , wherein n in the formula (2) is 5 or more and 60 or less. 4 . The magnetic carrier according to claim 1 , wherein Si on the surface of the magnetic carrier is 1.0 to 15.0 atomic % as measured by electron spectroscopy for chemical analysis (ESCA).

5. The magnetic carrier according to claim 1, wherein when the sum of the numbers of units Y1 and Y2 represented by the formula (1) and the formula (2) is represented by m, the following expression is satisfied: 50≤m≤250。 6 . The magnetic carrier according to claim 1 , wherein the coating resin contains 1 to 20% by mass of the resin A and contains 80 to 99% by mass of the resin B.

7. The magnetic carrier according to claim 1, wherein the resin B includes a unit Y3 represented by the following formula (3), and the content of the unit Y3 is 1% by mass or more and 75% by mass or less based on the resin B: wherein R8 represents cyclohexyl, cycloheptyl, cyclooctyl, cyclopentyl, cyclobutyl or cyclopropyl. 8 . The magnetic carrier according to claim 1 , wherein the resin B comprises a polymer in which a styrene-acrylic resin is graft-polymerized to polypropylene.

9. A two-component developer, characterized in that: It comprises the magnetic carrier according to any one of claims 1 to 8, and a toner.

10. A replenishing developer, characterized in that: It comprises the magnetic carrier according to any one of claims 1 to 8.

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