Two-component developer

Abstract

To provide a two-component developer that can suppress the decrease in the amount of charge of the developer due to the deterioration of the developer's durability in a high-temperature, high-humidity environment. [Solution] A two-component developer containing toner particles, a magnetic carrier, and inorganic fine particles B, wherein the magnetic carrier has magnetic carrier particles having a coating resin layer covering the surface of magnetic core particles, the coating resin layer contains inorganic fine particles A, at least a portion of the inorganic fine particles A is exposed on the surface of the carrier particles, the amount of inorganic fine particles B recovered by the water washing method XB is 0.01 to 0.05 parts by mass, the compression energy of the inorganic fine particles B is 75 mJ or less, and the work function WA of inorganic fine particles A, the work function WB of inorganic fine particles B, the coverage rate by inorganic fine particles A XA, the height of the protrusions of inorganic fine particles A HA, and the number-average particle size HB of inorganic fine particles B recovered by the water washing method satisfy the following formula. 0.5 ≤ |WA - WB| ≤ 10.0 0.001 ≤ XB / XA ≤ 0.010 0.5 ≤ HB / HA ≤ 4.0

Description

[Technical Field]

[0001] This disclosure relates to a two-component developer used in an image formation method using electrophotography. [Background technology]

[0002] In recent years, the demand for electrophotography has been steadily increasing, with a growing need for higher speed, higher image quality, and greater stability. To achieve higher image quality and greater stability, it is essential to ensure high image reproducibility in all usage environments during processes such as development, transfer, and fixing.

[0003] Conventionally, electrophotographic image formation methods generally involve forming an electrostatic latent image on an electrostatic latent image carrier using various means, and then developing the electrostatic latent image by attaching toner to it. In this development process, a two-component development method is widely employed, in which carrier particles called magnetic carriers are mixed with the toner, triboelectrically charged to impart an appropriate amount of positive or negative charge to the toner, and this charge is used as a driving force for development.

[0004] The two-component development method has advantages such as good controllability of developer performance because it allows for the assignment of functions such as agitation, transport, and charging of the developer to the magnetic carrier, resulting in a clear division of functions between the toner and the carrier. In this case, the magnetic carrier often consists of a magnetic core that provides magnetism and transportability, and a coating resin that coats the magnetic core to provide the ability to impart charge to the toner.

[0005] Since the density of images produced by electrophotography fluctuates due to the charge amount of toner, electrophotographic image forming machines generally incorporate a mechanism to maintain a constant final image density by adjusting the development conditions. However, when printing large quantities, if the charge amount fluctuates beyond the adjustment range due to factors such as deterioration of the developer's durability caused by agitation within the developing machine, it is known that problems such as a decrease in image density due to excessive charge or, conversely, contamination of the machine due to toner scattering caused by insufficient charge can occur. In recent image forming machine configurations designed to meet the needs for higher image quality and higher speed, the occurrence of these problems tends to become more pronounced, and there is a need for the invention of a developer that improves the characteristics of both.

[0006] In the two-component development method, the charging characteristics of the toner can be changed by the configuration of the magnetic carriers mentioned above, and in particular, magnetic carriers with an improved configuration of the coating resin layer are known.

[0007] Patent Document 1 proposes a carrier for electrophotographic dry developer, characterized in that the surface of the core material has a coating layer containing silica particles in a cyclohexyl acrylate resin.

[0008] Patent Document 2 proposes a carrier for electrophotographic dry developer, characterized in that the surface of the core material has a coating layer containing polyimide resin and fluororesin particles, and a coating layer containing silicone resin and barium titanate particles. [Prior art documents] [Patent Documents]

[0009] [Patent Document 1] Japanese Patent Publication No. 2023-047232 [Patent Document 2] Japanese Patent Publication No. 2023-162570 [Overview of the Initiative] [Problems that the invention aims to solve]

[0010] In the carrier-based developers disclosed in Patent Documents 1 and 2, the amount of charge of the developer decreases due to the deterioration of the developer's durability under high temperature and high humidity conditions. This disclosure provides a two-component developer that can suppress the decrease in the amount of charge of the developer due to the deterioration of the developer's durability under high temperature and high humidity conditions. [Means for solving the problem]

[0011] This disclosure relates to a two-component developer containing toner particles, a magnetic carrier, and inorganic fine particles B, The magnetic carrier has magnetic carrier particles, The magnetic carrier particle comprises a magnetic core particle and a coating resin layer that covers the surface of the magnetic core particle. The coating resin layer contains inorganic fine particles A, At least a portion of the inorganic fine particles A is exposed on the surface of the magnetic carrier particles, Regarding the amount of inorganic fine particles B recovered from the two-component developer by a water washing method, when the amount recovered per 100 parts by mass of the magnetic carrier is XB (parts by mass), XB is between 0.01 parts by mass and 0.05 parts by mass. The inorganic fine particles B have a compression energy of 75 mJ or less, as measured in the state of a powder layer formed by compressing at 30 kPa. When the work functions of inorganic fine particles A and B are WA(eV) and WB(eV), respectively, WA and WB satisfy the following equation (1), 0.5 ≤ |WA - WB| ≤ 10.0 Equation (1) When the coverage rate of the inorganic fine particles A on the surface of the magnetic carrier particle is XA (area %), XA and XB satisfy the following equation (2), 0.001≦XB / XA≦0.010 Formula (2) The present invention relates to a two-component developer characterized in that, when HA (nm) is the average height of the protrusions of the inorganic fine particles A exposed on the surface of the magnetic carrier particles, and HB (nm) is the number-average particle size of the primary particles of the inorganic fine particles B recovered by the water washing method, HA and HB satisfy the following formula (3). 0.5≦HB / HA≦4.0 Formula (3)

Advantages of the Invention

[0012] According to the present disclosure, a two-component developer capable of suppressing a decrease in the charge amount of a developer due to durability deterioration of the developer in a high-temperature and high-humidity environment can be provided.

Brief Description of the Drawings

[0013] [Figure 1] Image of surface observation of magnetic carrier by SEM [Figure 2] Schematic diagram showing a method for measuring the height of protrusions of inorganic fine particles exposed on the surface of magnetic carrier particles

Embodiments for Carrying Out the Invention

[0014] Hereinafter, the present disclosure will be described in detail, but the present disclosure is not limited to these descriptions. In the present disclosure, the description of "XX or more and YY or less" or "XX ≦ or ≦ YY" representing a numerical range means a numerical range including the lower limit and the upper limit which are the endpoints, unless otherwise specified. When the numerical ranges are described stepwise, the upper and lower limits of each numerical range can be arbitrarily combined.

[0015] The two-component developer of the present disclosure is A two-component developer containing toner particles, a magnetic carrier, and inorganic fine particles B, The magnetic carrier has magnetic carrier particles, The magnetic carrier particles have magnetic core particles and a coating resin layer covering the surface of the magnetic core particles, The coating resin layer contains inorganic fine particles A, At least a part of the inorganic fine particles A is exposed on the surface of the magnetic carrier particles, Regarding the recovery amount of the inorganic fine particles B recovered from the two-component developer by the water washing method, when the recovery amount per 100 parts by mass of the magnetic carrier is XB (parts by mass), the XB is 0.01 part by mass to 0.05 part by mass, The inorganic fine particles B have a compression energy of 75 mJ or less when measured in the state of a powder layer formed by compression at 30 kPa. When the work functions of inorganic fine particles A and B are WA(eV) and WB(eV), respectively, WA and WB satisfy the following equation (1), 0.5 ≤ |WA - WB| ≤ 10.0 Equation (1) When the coverage rate of the inorganic fine particles A on the surface of the magnetic carrier particle is XA (area %), XA and XB satisfy the following equation (2), 0.001≦XB / XA≦0.010 Formula (2) The present invention relates to a two-component developer characterized in that, when HA (nm) is the average height of the protrusions of the inorganic fine particles A exposed on the surface of the magnetic carrier particles, and HB (nm) is the number-average particle size of the primary particles of the inorganic fine particles B recovered by the water washing method, HA and HB satisfy the following formula (3). 0.5≦HB / HA≦4.0 Formula (3)

[0016] If the two-component developer of this disclosure satisfies the above configuration, it can suppress the decrease in the amount of charge of the developer due to the deterioration of the developer's durability in a high-temperature, high-humidity environment. The specific mechanism is thought to be as follows.

[0017] In magnetic carrier particles, applying a coating resin layer containing inorganic fine particles to the surface of the magnetic core particles suppresses changes in charge due to humidity changes due to the hygroscopic properties of the inorganic fine particles. The above-mentioned effect of suppressing changes in charge is easily obtained when the inorganic fine particles are exposed on the surface of the magnetic carrier particles. However, as a result of diligent research by the inventors, it has been found that coating resin layers in which inorganic fine particles are exposed on the surface of the magnetic carrier particles are more susceptible to wear of the coating resin layer due to contact between magnetic carrier particles compared to coating resin layers in which the inorganic fine particles are not exposed on the surface of the magnetic carrier particles. In particular, the wear becomes more pronounced when the number of printed sheets is large and the developer is frequently agitated by the replenishment operation in the developing machine. When the coating resin layer wears down, the resistance of the magnetic carrier increases, which tends to cause a decrease in the amount of charge of the developer.

[0018] Therefore, the inventors investigated a means to suppress wear of the coating resin layer due to contact between magnetic carrier particles by incorporating inorganic fine particles with a low coefficient of friction into the developer and arranging the inorganic fine particles exposed on the surface of the magnetic carrier particles adjacent to the inorganic fine particles with a low coefficient of friction. Specifically, by incorporating inorganic fine particles with a low coefficient of friction that have a work function difference with respect to the inorganic fine particles exposed on the surface of the magnetic carrier particles into the developer, the inorganic fine particles exposed on the surface of the magnetic carrier particles and the inorganic fine particles with a low coefficient of friction can be arranged adjacent to each other. As a result, the coefficient of friction on the surface of the magnetic carrier particles is reduced, and the stress caused by collisions between magnetic carrier particles is relieved, thereby suppressing wear of the coating resin layer and preventing a decrease in the charge amount of the developer.

[0019] The following describes in detail each component of this disclosure.

[0020] The two-component developer of this disclosure contains toner particles, a magnetic carrier, and inorganic fine particles B. Regarding the amount of inorganic fine particles B recovered from the two-component developer by a water washing method, when the amount recovered per 100 parts by mass of magnetic carrier is XB (parts by mass), XB is between 0.01 parts by mass and 0.05 parts by mass.

[0021] When XB is between 0.01 and 0.05 parts by mass, the inorganic fine particles A and B exposed on the surface of the magnetic carrier particles can be placed adjacent to each other, which suppresses wear of the coating resin layer due to contact between the magnetic carrier particles and improves charge stability. XB is preferably between 0.01 and 0.03 parts by mass. Further details regarding the water washing method will be described later.

[0022] The inorganic fine particles B have a compression energy of 75 mJ or less, as measured in the state of a powder layer formed by compressing at 30 kPa. When the compression energy is 75 mJ or less, the inorganic fine particles B adjacent to the inorganic fine particles A exposed on the surface of the magnetic carrier particles reduce the coefficient of friction on the surface of the magnetic carrier particles, thereby suppressing wear of the coating resin layer due to contact between the magnetic carrier particles. From the viewpoint of suppressing wear of the coating resin layer, the compression energy is preferably 65 mJ or less. Furthermore, from the viewpoint of development stability, the compression energy is preferably 5 mJ or more.

[0023] When the work functions (eV) of inorganic nanoparticles A and B are denoted as WA(eV) and WB(eV), respectively, WA and WB satisfy the following equation (1). 0.5 ≤ |WA - WB| ≤ 10.0 Equation (1)

[0024] The work function is the minimum energy (eV) required to extract a single electron from the surface of a material to infinity. When WA and WB satisfy equation (1) above, the triboelectric series of inorganic nanoparticles A and B are sufficiently far apart, making it easier for inorganic nanoparticles A and B to be adjacent to each other. From the viewpoint of enhancing the effect of making inorganic nanoparticles B adjacent to inorganic nanoparticles A exposed on the surface of the magnetic carrier particles, and from the viewpoint of charge stability, it is preferable that |WA-WB| be between 0.5eV and 5.2eV.

[0025] When the coverage rate of inorganic fine particles A on the surface of a magnetic carrier particle is XA (area %), XA and XB satisfy the following equation (2). 0.001≦XB / XA≦0.010 Formula (2)

[0026] When XA and XB satisfy equation (2) above, inorganic fine particles A and inorganic fine particles B exposed on the surface of the magnetic carrier particles can be placed adjacent to each other, and wear of the coating resin layer due to contact between magnetic carrier particles can be suppressed. XB / XA is preferably 0.001 or more and 0.003 or less. XA can be controlled by the amount of inorganic fine particles A added to the coating resin that covers the surface of the magnetic core particles. Details on the method for measuring the coating rate XA will be described later.

[0027] When HA (nm) is the average height of the protrusions of inorganic fine particles A exposed on the surface of the magnetic carrier particles, and HB (nm) is the number-average particle size of the primary particles of inorganic fine particles B recovered by the water washing method, HA and HB satisfy the following equation (3). 0.5≦HB / HA≦4.0 Formula (3)

[0028] When HA and HB satisfy the above equation (3), inorganic fine particles A and inorganic fine particles B exposed on the surface of the magnetic carrier particles can be placed adjacent to each other, and wear of the coating resin layer due to contact between magnetic carrier particles can be suppressed. HB / HA is preferably between 0.5 and 3.5. HA can be controlled by the particle size and specific gravity of inorganic fine particles A. Details on the measurement method for the average value HA of the protrusion height and the number-average particle size HB of the primary particles of inorganic fine particles B recovered by the water washing method will be described later.

[0029] <Inorganic fine particles B> The two-component developer in this disclosure contains inorganic fine particles B, the compressed energy of which is 75 mJ or less, as measured in the state of a powder layer formed by compressing at 30 kPa. The inorganic fine particles B are not particularly limited as long as the compressed energy is 75 mJ or less, and can be selected and used from known inorganic fine particles. Examples include strontium titanate fine particles, titanium oxide fine particles, and silica fine particles.

[0030] Inorganic fine particles B are preferably strontium titanate fine particles, from the viewpoint of suppressing wear of the coating resin layer due to contact between magnetic carrier particles and suppressing changes in charge amount due to changes in humidity.

[0031] In the present disclosure, inorganic fine particles B are surface-treated inorganic fine particles, and it is preferable that the surface treatment agent is at least one selected from the group consisting of silane coupling agents, fluorosilane coupling agents, fatty acids, and fatty acid metal salts, in order to suppress wear of the coating layer due to contact between carriers and to suppress changes in the amount of charge due to changes in humidity. Among these, it is even more preferable that inorganic fine particles B are surface-treated inorganic fine particles, and the surface treatment agent is at least one selected from the group consisting of silane coupling agents and fluorosilane coupling agents.

[0032] For example, inorganic fine particles B can be included in a two-component developer by adding them externally to toner particles.

[0033] <Magnetic carrier> In this disclosure, a magnetic carrier (hereinafter sometimes simply referred to as "carrier") comprises a magnetic core particle and a coating resin layer covering the surface of the magnetic core particle. The coating resin layer contains inorganic fine particles A, and at least a portion of the inorganic fine particles A is exposed on the surface of the magnetic carrier particle.

[0034] <Magnetic core particles> Conventional magnetic particles such as ferrite and magnetite can be used as magnetic core particles for magnetic carriers. Alternatively, magnetic core particles in which ferrite or magnetite particles with voids are filled with resin can also be used.

[0035] Among these, a magnetic core in which resin is filled into magnetic particles having voids is preferred from the viewpoint of being able to reduce the magnetization amount of the magnetic carrier. Furthermore, by changing the composition ratio of the raw material metal oxide, a ferrite with a desired magnetization amount can be obtained.

[0036] Furthermore, while copolymer resins used as coating resins can be used as the resin to be contained in the pores of porous magnetic particles, the resin is not limited to this, and known resins such as thermoplastic resins and thermosetting resins can be used.

[0037] As thermoplastic resins, copolymers used as coating resins are preferred, but other examples include the following: polystyrene, polymethyl methacrylate, styrene-acrylic acid ester copolymer, styrene-methacrylic acid ester copolymer, styrene-butadiene copolymer, ethylene-vinyl acetate copolymer, polyvinyl chloride, polyvinyl acetate, polyvinylidene fluoride resin, fluorocarbon resin, perfluorocarbon resin, solvent-soluble perfluorocarbon resin, polyvinylpyrrolidone, petroleum resin, novolac resin, saturated alkyl polyester resin, polyethylene terephthalate, polybutylene terephthalate, aromatic polyester resin such as polyarylate, polyamide resin, polyacetal resin, polycarbonate resin, polyethersulfone resin, polysulfone resin, polyphenylene sulfide resin, and polyetherketone resin.

[0038] Examples of thermosetting resins include: phenolic resins, modified phenolic resins, maleic resins, alkyd resins, epoxy resins, acrylic resins, unsaturated polyesters obtained by polycondensation of maleic anhydride, terephthalic acid, and polyhydric alcohols, urea resins, melamine resins, urea-melamine resins, xylene resins, toluene resins, guanamine resins, melamine-guanamine resins, acetoguanamine resins, glyptal resins, furan resins, silicone resins, polyimides, polyamideimide resins, polyetherimide resins, and polyurethane resins.

[0039] The magnetic core particles preferably have a 50% particle size (D50) of 20 μm or more and 80 μm or less based on volume distribution, which allows for uniform coating of the coating resin, prevents magnetic carrier adhesion, and provides an appropriate density of magnetic particles for obtaining high-quality images.

[0040] <Coating resin layer> The magnetic carrier of this disclosure includes a resin coating layer that covers the surface of magnetic core particles. The coating resin layer contains a coating resin and inorganic fine particles A.

[0041] As coating resins, monopolymers of styrene and its substituted products such as poly-p-chlorostyrene and polyvinyltoluene; styrene copolymers such as styrene-p-chlorostyrene copolymer, styrene-vinyltoluene copolymer, styrene-vinylnaphthalene copolymer, styrene-acrylic acid ester copolymer, and styrene-methacrylic acid ester copolymer; and resins such as styrene copolymer resins, (meth)acrylic resins, silicone resins, polyester resins, styrene-acrylic resins, urethane resins, polyethylene, polyethylene terephthalate, polystyrene resins, polyamide resins, and polypropylene resins can be used.

[0042] Furthermore, a resin having a reactive functional group may be used as the coating resin. Known functional groups such as carboxyl groups, hydroxyl groups, epoxy groups, amino groups, vinyl groups, (meth)acryloyl groups, isocyanate groups, mercapto groups, and oxazoline groups can be selected as reactive functional groups. Specifically, resins having a carboxyl group include resins polymerized from acrylic acid, methacrylic acid, or itaconic acid as monomers; resins having a hydroxyl group include resins consisting of 3-hydroxymethylacrylic, 2-hydroxyethylacrylic acid, 2-hydroxypropylacrylic acid, 2-hydroxypropylmethacrylic acid, 2-hydroxybutylacrylic acid, etc.; resins having a vinyl group include resins consisting of allyl acrylate, allyl methacrylate, etc.; resins having an epoxy group include resins consisting of acrylic glycidyl acid, hydroxybutyl glycidyl ether acrylate, or β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane; and resins having an amine include resins consisting of acrylamide or methacrylamide.

[0043] <Inorganic fine particles A> The magnetic carrier of this disclosure contains inorganic fine particles A within a coating resin layer. The inorganic fine particles A are not particularly limited as long as they satisfy a predetermined relationship with inorganic fine particles B in terms of work function, and can be selected and used from known inorganic fine particles. Examples include silica fine particles, barium titanate fine particles, and strontium titanate fine particles.

[0044] Inorganic fine particles A are preferably silica fine particles from the viewpoint of suppressing changes in charge due to changes in humidity. The silica fine particles are not particularly limited and can be selected and used from known types as long as they do not impair the effects of this disclosure. For example, examples include combustion-processed silica particles, deflagration-processed silica particles, sol-gel silica particles, sedimentation-processed silica particles, and colloidal silica particles. Among these, wet silica particles produced by wet methods such as the sol-gel method or sedimentation method are preferred because they readily adsorb moisture in high-temperature and high-humidity environments, and thus provide a better effect in suppressing changes in charge due to changes in humidity.

[0045] It is preferable that the inorganic fine particles A are hydrophobized by surface treatment. Any known means can be used for surface treatment, and can be selected from silane coupling agents having alkyl groups such as methyl, ethyl, and propyl groups, titanate coupling agents, and aluminate coupling agents, and silica particles with a desired hydrophobicity can be obtained by surface treatment. Of these, silane coupling agents can be used particularly suitably, and since inorganic fine particles A can adsorb moisture appropriately in high temperature and high humidity environments, hexamethyldisilazane treatment is a particularly preferred form.

[0046] The shape of the inorganic fine particles A is not particularly limited, but a spherical shape is preferable because it reduces wear of the coating resin layer due to contact between magnetic carrier particles. The number-average particle size of the inorganic fine particles A is preferably between 15 nm and 200 nm in order to adhere to the surface of the magnetic carrier particles and be sufficiently exposed to the surface of the magnetic carrier particles.

[0047] <Toner particles> The two-component developer in this disclosure contains toner particles manufactured by known methods. Generally, it has a composition in which a binder resin for toner matrix is ​​the main component, and optionally contains a release agent, a colorant, a dispersion aid, and inorganic particles.

[0048] <Binding resin for toner base> The following polymers can be used as binder resins for the toner matrix of toner particles: monopolymers of styrene and its substituted derivatives such as polystyrene, poly-p-chlorostyrene, and polyvinyltoluene; styrene copolymers such as styrene-p-chlorostyrene copolymer, styrene-vinyltoluene copolymer, styrene-vinylnaphthalene copolymer, styrene-acrylic acid ester copolymer, and styrene-methacrylic acid ester copolymer; styrene copolymer resins, polyester resins, hybrid resins obtained by mixing polyester resin and vinyl resin, or by partial reaction of both; polyvinyl chloride, phenolic resin, naturally modified phenolic resin, naturally modified maleic acid resin, acrylic resin, methacrylic resin, polyvinyl acetate, silicone resin, polyester resin, polyurethane, polyamide resin, furan resin, epoxy resin, xylene resin, polyethylene resin, and polypropylene resin. Among these, a main component polyester resin is preferred from the viewpoint of low-temperature fixation.

[0049] Monomers used in polyester units of polyester resins include polyhydric alcohols (dihydric or trihydric or higher alcohols), polyhydric carboxylic acids (dihydric or trihydric or higher carboxylic acids), their acid anhydrides, or their lower alkyl esters. In order to create branched polymers that exhibit "strain hardening properties," partial crosslinking within the amorphous resin molecule is effective, and for this purpose, it is preferable to use polyfunctional compounds with a valency of trihydric or higher. Therefore, it is preferable that the raw material monomers for the polyester unit include trihydric or higher carboxylic acids, their acid anhydrides, or their lower alkyl esters, and / or trihydric or higher alcohols.

[0050] The following polyhydric alcohol monomers can be used as polyhydric alcohol monomers in the polyester units of polyester resin.

[0051] Examples of divalent alcohol components include ethylene glycol, propylene glycol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, diethylene glycol, triethylene glycol, 1,5-pentanediol, 1,6-hexanediol, neopentyl glycol, 2-ethyl-1,3-hexanediol, hydrogenated bisphenol A, and bisphenols represented by formula (A) and their derivatives;

[0052] [ka]

[0053] Diols represented by formula (B);

[0054] [ka]

[0055] Examples of trivalent or higher alcohol components include sorbitol, 1,2,3,6-hexanetetrol, 1,4-sorbitan, pentaerythritol, dipentaerythritol, tripentaerythritol, 1,2,4-butanetriol, 1,2,5-pentanetriol, glycerol, 2-methylpropanetriol, 2-methyl-1,2,4-butanetriol, trimethylolethane, trimethylolpropane, and 1,3,5-trihydroxymethylbenzene. Of these, glycerol, trimethylolpropane, and pentaerythritol are preferred. These divalent and trivalent or higher alcohols can be used individually or in combination.

[0056] The following polycarboxylic acid monomers can be used as polycarboxylic acid monomers in the polyester units of polyester resins.

[0057] Examples of divalent carboxylic acid components include maleic acid, fumaric acid, citraconic acid, itaconic acid, glutaconic acid, phthalic acid, isophthalic acid, terephthalic acid, succinic acid, adipic acid, sebatic acid, azelaic acid, malonic acid, n-dodecenylsuccinic acid, isododecenylsuccinic acid, n-dodecylsuccinic acid, isododecylsuccinic acid, n-octenylsuccinic acid, n-octylsuccinic acid, isooctenylsuccinic acid, isooctylsuccinic acid, anhydrides of these acids, and lower alkyl esters thereof. Of these, maleic acid, fumaric acid, terephthalic acid, and n-dodecenylsuccinic acid are preferably used.

[0058] Examples of trivalent or higher carboxylic acids, their acid anhydrides, or their lower alkyl esters include 1,2,4-benzenetricarboxylic acid, 2,5,7-naphthalentricarboxylic acid, 1,2,4-naphthalentricarboxylic acid, 1,2,4-butanetricarboxylic acid, 1,2,5-hexanetricarboxylic acid, 1,3-dicarboxyl-2-methyl-2-methylenecarboxypropane, 1,2,4-cyclohexanetricarboxylic acid, tetra(methylenecarboxyl)methane, 1,2,7,8-octanetetracarboxylic acid, pyromellitic acid, empole trimeric acid, their acid anhydrides, or their lower alkyl esters. Of these, 1,2,4-benzenetricarboxylic acid, i.e., trimellitic acid or its derivatives, is particularly preferred because it is inexpensive and easy to control the reaction. These divalent carboxylic acids and trivalent or higher carboxylic acids can be used individually or in combination.

[0059] The method for producing the polyester unit is not particularly limited, and known methods can be used. For example, the aforementioned alcohol monomer and carboxylic acid monomer can be charged simultaneously, and polymerized through an esterification reaction or transesterification reaction, and a condensation reaction to produce a polyester resin. The polymerization temperature is not particularly limited, but a range of 180°C to 290°C is preferred. When polymerizing the polyester unit, polymerization catalysts such as titanium-based catalysts, tin-based catalysts, zinc acetate, antimony trioxide, and germanium dioxide can be used. In particular, polyester units polymerized using a tin-based catalyst are more preferred for binder resins for toner substrates.

[0060] Furthermore, a polyester resin with an acid value of 5 mg KOH / g or more and 20 mg KOH / g or less, and a hydroxyl value of 20 mg KOH / g or more and 70 mg KOH / g or less is preferable from the viewpoint of covering properties, as it suppresses the amount of moisture adsorbed in high-temperature and high-humidity environments and keeps the non-electrostatic adhesion low.

[0061] Furthermore, the binder resin for the toner base may be a mixture of low-molecular-weight resin and high-molecular-weight resin. From the viewpoint of low-temperature fixing performance and hot-off resistance, the ratio of high-molecular-weight resin content to low-molecular-weight resin content in the binder resin for the toner base is preferably 40 / 60 or more and 85 / 15 or less by mass.

[0062] <Release agent> Toner particles may contain a release agent to improve separation from the material during heat fixing. Examples include: hydrocarbon waxes such as low molecular weight polyethylene, low molecular weight polypropylene, alkylene copolymers, microcrystalline wax, paraffin wax, and Fischer-Tropsch wax; oxides of hydrocarbon waxes such as oxidized polyethylene wax or block copolymers thereof; waxes mainly composed of fatty acid esters such as carnauba wax; and deoxidized fatty acid esters such as deoxidized carnauba wax. Furthermore, the following are also examples. Saturated linear fatty acids such as palmitic acid, stearic acid, and montanic acid; unsaturated fatty acids such as brassic acid, eleostearic acid, and valinalic acid; saturated alcohols such as stearyl alcohol, aralkyl alcohol, behenyl alcohol, carnaubyl alcohol, ceryl alcohol, and melissyl alcohol; polyhydric alcohols such as sorbitol; esters of fatty acids such as palmitic acid, stearic acid, behenic acid, and montanic acid with alcohols such as stearyl alcohol, aralkyl alcohol, behenyl alcohol, carnaubyl alcohol, ceryl alcohol, and melissyl alcohol; fatty acid amides such as linoleic acid amide, oleic acid amide, and lauric acid amide; methylenebisstearate amide, ethylenebiscaprate amide, ethylenebislaurate amide, and hexamethylene Saturated fatty acid bisamides such as bis-stearamide; unsaturated fatty acid amides such as ethylenebisoleamide, hexamethylenebisoleamide, N,N'dioleyladipamide, and N,N'dioleylsebacamide; aromatic bisamides such as m-xylenebis-stearamide and N,N'distearylisophthalamide; aliphatic metal salts (commonly known as metal soaps) such as calcium stearate, calcium laurate, zinc stearate, and magnesium stearate; waxes grafted onto aliphatic hydrocarbon waxes with vinyl monomers such as styrene or acrylic acid; partially esterified fatty acids and polyhydric alcohols such as behenic acid monoglyceride; methyl ester compounds having a hydroxyl group obtained by hydrogenation of vegetable oils.

[0063] 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 this disclosure, hydrocarbon waxes are more preferred in that they further improve hot offset resistance. In this disclosure, the wax is preferably used in an amount of 3 to 8 parts by mass per 100 parts by mass of the binder resin for the toner base.

[0064] Furthermore, in the endothermic curve measured by a differential scanning calorimetry (DSC) device during heating, the peak temperature of the wax's maximum endothermic peak is preferably between 45°C and 140°C. A peak temperature within this range is preferable because it allows for both good storage and resistance to hot offset of the toner particles.

[0065] <Coloring agent> Toner particles may contain colorants. Examples of colorants include the following: Examples of black colorants include carbon black, yellow colorants, magenta colorants, and cyan colorants used to create black. While pigments may be used alone as colorants, using dyes and pigments in combination is preferable from the standpoint of full-color image quality to improve clarity.

[0066] The following are examples of pigments used for magenta toner: 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, 282; CI Pigment Violet 19; CI Bat Red 1, 2, 10, 13, 15, 23, 29, 35.

[0067] Examples of dyes 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, 121; CI Disperse Red 9; CI Solvent Violet 8, 13, 14, 21, 27; 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, 40; and CI Basic Violet 1, 3, 7, 10, 14, 15, 21, 25, 26, 27, 28.

[0068] Examples of pigments for cyan toner include: CI Pigment Blue 2, 3, 15:2, 15:3, 15:4, 16, 17; CI Bat Blue 6; CI Acid Blue 45; and copper phthalocyanine pigments in which phthalimidomethyl groups are substituted onto the phthalocyanine skeleton.

[0069] CI Solvent Blue 70 is an example of a dye used for cyan toner.

[0070] The following pigments are used for yellow toner: 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, 185; CI Bat Yellow 1, 3, 20.

[0071] CI Solvent Yellow 162 is an example of a dye used for yellow toner.

[0072] These colorants can be used individually, in combination, or even in solid solution form. The colorants are selected based on their hue angle, saturation, brightness, lightfastness, OHP transparency, and dispersibility in toner.

[0073] The colorant content is preferably 0.1 parts by mass or more and 30.0 parts by mass or less relative to the total amount of resin components.

[0074] <Dispersing agent> Toner particles preferably contain a dispersion aid to disperse the release agent in the resin. While known dispersion aids can be used, when a hydrocarbon wax is included as the release agent, it is preferable to include a polymer having a structure formed by the reaction of a vinyl resin component with a hydrocarbon compound to disperse the wax in the resin. Among these, it is preferable to include a graft polymer in which vinyl monomers are graft polymerized onto a polyolefin.

[0075] When a polymer is included in the dispersion aid, the compatibility between the wax and the resin is promoted, making it less likely to cause problems such as poor charging due to poor wax dispersion and contamination of components. Furthermore, the content of the dispersion aid is preferably 1.0 part by mass to 15 parts by mass per 100 parts by mass of the binder resin for the toner base. When the content of the dispersion aid is within this range, the wax dispersion in the amorphous resin tends to become uniform. The polyolefin is not particularly limited as long as it is a polymer or copolymer of unsaturated hydrocarbons, and various polyolefins can be used. Polyethylene-based and polypropylene-based polyolefins are particularly preferred. Multiple types of these may be used.

[0076] Examples of monomers having vinyl groups include the following:

[0077] Styrene-based units such as styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, p-methoxystyrene, p-phenylstyrene, p-chlorostyrene, 3,4-dichlorostyrene, p-ethylstyrene, 2,4-dimethylstyrene, pn-butylstyrene, p-tert-butylstyrene, pn-hexylstyrene, pn-octylstyrene, pn-nonylstyrene, pn-decylstyrene, pn-dodecylstyrene, and styrene derivatives thereof.

[0078] Amino group-containing α-methylene aliphatic monocarboxylic acid esters such as dimethylaminoethyl methacrylate and diethylaminoethyl methacrylate; vinyl units containing an N atom, such as acrylic acid or methacrylic acid derivatives such as acrylonitrile, methacrylonitrile, and acrylamide.

[0079] Unsaturated dibasic acids such as maleic acid, citraconic acid, itaconic acid, alkenyl succinic acid, fumaric acid, and mesaconic acid; unsaturated dibasic acid anhydrides such as maleic anhydride, citraconic acid anhydride, itaconic acid anhydride, and alkenyl succinic acid anhydride; methyl maleate half ester, ethyl maleate half ester, butyl maleate half ester, methyl citraconic acid half ester, ethyl citraconic acid half ester, butyl citraconic acid half ester, methyl itaconic acid half ester, methyl alkenyl succinate half ester, f Half-esters of unsaturated dibasic acids such as methyl malate half-ester and methyl mesaconate half-ester; unsaturated dibasic acid esters such as dimethyl maleic acid and dimethyl fumaric acid; α,β-unsaturated acids such as acrylic acid, methacrylic acid, crotonic acid, and cinnamic acid; α,β-unsaturated acid anhydrides such as crotonic acid anhydride and cinnamic acid anhydride, anhydrides of the α,β-unsaturated acid and lower fatty acids; vinyl units containing carboxyl groups such as alkenyl malonic acid, alkenyl glutaric acid, alkenyl adipic acid, their acid anhydrides, and their monoesters.

[0080] Acrylic acid or methacrylic acid esters such as 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, and 2-hydroxypropyl methacrylate, and vinyl units containing a hydroxyl group such as 4-(1-hydroxy-1-methylbutyl)styrene and 4-(1-hydroxy-1-methylhexyl)styrene.

[0081] Ester units consisting of acrylic acid esters such as methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, propyl acrylate, n-octyl acrylate, dodecyl acrylate, 2-ethylhexyl acrylate, stearyl acrylate, 2-chloroethyl acrylate, and phenyl acrylate.

[0082] Ester units consisting of methacrylic acid esters such as cyclohexyl methacrylate, methyl methacrylate, ethyl methacrylate, propyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, n-octyl methacrylate, dodecyl methacrylate, 2-ethylhexyl methacrylate, stearyl methacrylate, phenyl methacrylate, dimethylaminoethyl methacrylate, and diethylaminoethyl methacrylate, which are α-methylene aliphatic monocarboxylic acid esters. Multiple units of these may be used.

[0083] The above-mentioned dispersion aids can be obtained by known methods, such as the reaction of these polymers with each other or the reaction of a monomer of one polymer with the other polymer.

[0084] <External additives> The toner particles of this disclosure may have the above-described inorganic fine particles B added as an external additive. From the viewpoint of including inorganic fine particles B in the two-component developer, it is preferable that the adhesion rate of inorganic fine particles B to the toner particles, as measured by the water washing method, is 5% to 85%. It is more preferable that the adhesion rate of inorganic fine particles B to the toner particles is 10% to 60%, and even more preferable that it is 20% to 40%. The adhesion rate of inorganic fine particles B to the toner particles can be controlled by the number-average particle size of inorganic fine particles B, the surface treatment method, the amount of inorganic fine particles B added to the toner particles, and the external additive conditions.

[0085] Toner particles may contain external additives other than inorganic fine particles B, primarily for the purpose of improving fluidity and electrostatic properties.

[0086] As spacer particles to suppress toner particle blocking, silica particles with a maximum peak particle size of 50 nm to 200 nm based on the number distribution are preferred. More preferably, the silica particles have a particle size of 80 nm to 150 nm, from the viewpoint of being able to function as spacer particles while suppressing detachment from toner particles.

[0087] Furthermore, in order to improve the fluidity of the toner particles, it is preferable to include inorganic fine particles with a maximum peak particle size of 20 nm to 50 nm based on the number distribution, and it is also preferable to use them in combination with the above-mentioned spacer particles.

[0088] Furthermore, other external additives may be added to the toner particles to improve fluidity and transferability. The external additives added to the surface of the toner particles preferably include inorganic fine particles such as titanium dioxide, aluminum oxide, strontium titanate, and barium titanate, and multiple types may be used in combination.

[0089] The total amount of external additives added to the toner particles is preferably 0.3 parts by mass or more and 5.0 parts by mass or less, and more preferably 0.8 parts by mass or more and 4.0 parts by mass or less, per 100 parts by mass of toner particles. Of these, the content of silica particles with a maximum peak particle size of 50 nm or more and 200 nm or less based on the number distribution is preferably 0.1 parts by mass or more and 2.5 parts by mass or less, and more preferably 0.5 parts by mass or more and 2.0 parts by mass or less. Within this range, the effect as spacer particles becomes more pronounced.

[0090] Furthermore, it is preferable that the surface of the inorganic fine particles used as an external additive is hydrophobic. The hydrophobic treatment is preferably performed using coupling agents such as various titanium coupling agents and silane coupling agents; fatty acids and their metal salts; silicone oil; or a combination thereof.

[0091] Hydrophobic treatment is preferably carried out by adding a hydrophobic agent in an amount of 1% to 30% by mass (more preferably 3% to 7% by mass) of the particles to be treated to coat the particles.

[0092] The degree of hydrophobicity of the hydrophobicized external additive is not particularly limited, but for example, it is preferable that the hydrophobicity rate (%) of the external additive is 40% or more and 98% or less. The hydrophobicity rate indicates the wettability of the sample to methanol and is an indicator of hydrophobicity.

[0093] <Toner particles and toner manufacturing method> The method for producing toner particles is not particularly limited, and known methods such as grinding, suspension polymerization, dissolution-suspension, emulsification-coagulation, and dispersion polymerization can be used. Among these, grinding is preferred from the viewpoint of controlling the wax on the surface of the toner particles. In other words, it is preferable that the toner particles are ground toner particles.

[0094] The following describes the manufacturing procedure for toner particles using the grinding method.

[0095] In the raw material mixing process, predetermined amounts of materials constituting the toner particles, such as binder resin, release agent, colorant, crystalline polyester, and other components such as charge control agents as needed, are weighed, blended, and mixed. Examples of mixing equipment include the DoubleCon Mixer (manufactured by Nishimura Machinery Works Co., Ltd.), V-type Mixer (manufactured by Nishimura Machinery Works Co., Ltd.), Drum-type Mixer (manufactured by Eishin Co., Ltd.), Super Mixer (manufactured by Kawata Co., Ltd.), Henschel Mixer (manufactured by Nippon Coke Industries Co., Ltd.), Nauta Mixer (manufactured by Hosokawa Micron Corporation), and MechanoHybrid (manufactured by Nippon Coke Industries Co., Ltd.).

[0096] Next, the mixed materials are melt-kneaded to disperse wax and other substances into the binder resin. In this melt-kneading process, batch-type kneaders such as pressure kneaders and Banbury mixers, or continuous kneaders can be used, and single-screw or twin-screw extruders are the mainstream due to their advantage of being able to produce continuously. Examples include the KTK twin-screw extruder (manufactured by Kobe Steel, Ltd.), the TEM twin-screw extruder (manufactured by Toshiba Machine Co., Ltd.), the PCM kneader (manufactured by Ikegai Iron Works, Ltd.), the twin-screw extruder (manufactured by KCK Co., Ltd.), the Co-kneader (manufactured by Buss Co., Ltd.), and the Nidex (manufactured by Nippon Coke Industries, Ltd.). Furthermore, the resin composition obtained by melt-kneading may be rolled with two rolls or the like and cooled with water in a cooling process.

[0097] Next, the cooled resin composition is pulverized to the desired particle size in a pulverization process. In the pulverization process, for example, it is coarsely pulverized using a pulverizer such as a crusher, hammer mill, or feather mill, and then further finely pulverized using a fine pulverizer such as a Cryptron system (manufactured by Kawasaki Heavy Industries), Super Rotor (manufactured by Nisshin Engineering Co., Ltd.), Turbo Mill (manufactured by Turbo Industries Co., Ltd.), or an air jet type pulverizer.

[0098] Subsequently, the materials are classified as needed using classifiers or sieves such as the inertial classifier Elbow Jet (manufactured by Nippon Steel Mining Co., Ltd.), the centrifugal classifier Turboplex (manufactured by Hosokawa Micron Corporation), the TSP separator (manufactured by Hosokawa Micron Corporation), and the Faculty (manufactured by Hosokawa Micron Corporation).

[0099] Subsequently, the toner particles are externally treated with inorganic microparticles such as silica microparticles to obtain toner. Methods for externally treating with inorganic microparticles include mixing a predetermined amount of classified toner with various known inorganic microparticles and stirring and mixing using mixing equipment such as a double mixer (manufactured by Nishimura Machinery Works Co., Ltd.), a V-type mixer (manufactured by Nishimura Machinery Works Co., Ltd.), a drum-type mixer (manufactured by Eishin Co., Ltd.), a super mixer (manufactured by Kawata Co., Ltd.), a Henschel mixer (manufactured by Nippon Coke Industries Co., Ltd.), a Nauta mixer (manufactured by Hosokawa Micron Corporation), a Mechano Hybrid (manufactured by Nippon Coke Industries Co., Ltd.), or a Novilta (manufactured by Hosokawa Micron Corporation) as an external additive machine.

[0100] <Method for manufacturing magnetic carriers> The manufacturing method for magnetic carriers varies depending on the type.

[0101] The following describes in detail the manufacturing process of porous magnetic particles as an example.

[0102] (Method for manufacturing magnetic core particles) [Process 1: Weighing and Mixing Process] First, the ferrite raw materials are weighed and mixed.

[0103] Ferrite is a sintered body represented by the following general formula. (M12O) x(M2O) y (Fe2O3) z

[0104] In the equation, M1 is a monovalent metal and M2 is a divalent metal. When x + y + z = 1.0, x and y are 0 ≤ (x, y) ≤ 0.8, and z is 0.2. <z<1.0である。

[0105] In the formula, it is preferable to use at least one metal atom selected from the group consisting of Li, Fe, Mn, Mg, Sr, Cu, Zn, and Ca as M1 and M2. Other metals that can be used include Ni, Co, Ba, Y, V, Bi, In, Ta, Zr, B, Mo, Na, Sn, Ti, Cr, Al, Si, and rare earth elements.

[0106] Examples of ferrite raw materials include metal particles of the aforementioned metal elements, or their oxides, hydroxides, oxalates, carbonates, etc. Examples of mixing equipment include the following: ball mills, planetary mills, giot mills, and vibratory mills. Ball mills are particularly preferred from the viewpoint of mixability. Specifically, weighed ferrite raw materials and balls are placed in a ball mill and crushed and mixed for preferably 0.1 hours to 20.0 hours.

[0107] [Step 2: Pre-firing process] The crushed and mixed ferrite raw material is calcined in air or under a nitrogen atmosphere, preferably at a calcination temperature of 700°C to 1200°C, and preferably for 0.5 hours to 5.0 hours, to ferrite it. For calcination, for example, the following furnaces can be used: burner-type incinerators, rotary calcination furnaces, electric furnaces, etc.

[0108] [Step 3: Grinding Process] The calcined ferrite prepared in step 2 is crushed in a crusher. The crusher is not particularly limited as long as the desired particle size can be obtained. Examples include crushers, hammer mills, ball mills, bead mills, planetary mills, and giotto mills. To obtain the desired particle size of the crushed ferrite, it is preferable to control the material of the balls or beads used, the particle size, and the operating time in ball mills and bead mills, for example. Specifically, to reduce the particle size of the calcined ferrite slurry, a ball with a higher specific gravity can be used, or the crushing time can be increased. Also, to broaden the particle size distribution of the calcined ferrite, a ball or bead with a higher specific gravity can be used, and the crushing time can be shortened. Furthermore, calcined ferrite with a broad distribution can also be obtained by mixing multiple calcined ferrites with different particle sizes. In addition, in ball mills and bead mills, wet milling is more efficient than dry milling because the crushed material does not fly around in the mill. For this reason, wet milling is more preferable than dry milling.

[0109] [Process 4 Granulation process] To the pulverized calcined ferrite, water, a binder, and, if necessary, a pore modifier are added. Examples of pore modifiers include foaming agents and resin microparticles. Examples of foaming agents include sodium bicarbonate, potassium bicarbonate, lithium bicarbonate, ammonium bicarbonate, sodium carbonate, potassium carbonate, lithium carbonate, and ammonium carbonate.

[0110] For example, polyvinyl alcohol can be used as the binder mentioned above.

[0111] Examples of resin microparticles include polyester, polystyrene, styrene copolymers such as styrene-vinyltoluene copolymer, styrene-vinylnaphthalene copolymer, styrene-acrylic acid ester copolymer, styrene-methacrylic acid ester copolymer, styrene-α-chloromethacrylate methyl copolymer, styrene-acrylonitrile copolymer, styrene-vinylmethyl ketone copolymer, styrene-butadiene copolymer, styrene-isoprene copolymer, and styrene-acrylonitrile-indene copolymer; polyvinyl chloride, phenol resin, modified phenol resin, malein resin, acrylic resin, methacrylic resin, polyvinyl acetate, and silicone resin; polyester resin having monomers selected from aliphatic polyhydric alcohols, aliphatic dicarboxylic acids, aromatic dicarboxylic acids, aromatic dialcohols, and diphenols as structural units; polyurethane resin, polyamide resin, polyvinyl butyral, terpene resin, coumarone indene resin, petroleum resin, and hybrid resin microparticles having polyester units and vinyl polymer units.

[0112] In step 3, if the material is pulverized using a wet process, it is preferable to take into account the water contained in the ferrite slurry and add a binder and, if necessary, a pore-adjusting agent.

[0113] The obtained ferrite slurry is dried and granulated using a spray dryer, preferably in a heated atmosphere between 100°C and 200°C. The spray dryer is not particularly limited as long as it can produce magnetic particles with the desired porous shape. For example, a spray dryer can be used.

[0114] [Process 5: Firing Process] Next, the granulated product is fired at a temperature of preferably 800°C to 1400°C for preferably 1 hour to 24 hours. By increasing the firing temperature and extending the firing time, the firing of the porous magnetic core particles progresses, resulting in smaller pore diameters and a reduction in the number of pores.

[0115] [Process 6: Sorting Process] After crushing the calcined particles as described above, coarse and fine particles may be removed by classification or sieving as needed.

[0116] [Process 7 Filling process] The method for filling the voids of porous magnetic core particles with resin is not particularly limited, but examples include impregnating the porous magnetic core particles with a resin solution by immersion, spraying, brushing, or a fluidized bed, and then evaporating the solvent. Alternatively, the resin can be diluted with a solvent and added to the voids of the porous magnetic core particles.

[0117] The solvent used here can be any solvent capable of dissolving the resin. If the resin is soluble in organic solvents, examples of organic solvents include toluene, xylene, cellulose butyl acetate, methyl ethyl ketone, methyl isobutyl ketone, and methanol. If the resin is water-soluble or an emulsion-type resin, water can be used as the solvent.

[0118] The amount of resin solids in the above resin solution is preferably 1% by mass or more and 50% by mass or less, and more preferably 1% by mass or more and 30% by mass or less. When it is 50% by mass or less, the viscosity is not too high and the resin solution can easily penetrate uniformly into the voids of the porous magnetic core particles. On the other hand, when it is 1% by mass or more, the amount of resin is appropriate and the adhesion of the resin to the porous magnetic core particles is good. The method of coating the surface of the magnetic core particles with resin thereafter is not particularly limited, but examples include coating by immersion, spraying, brushing, dry application, and application methods such as a fluidized bed.

[0119] (Method of coating with coating resin) The method for coating the surface of magnetic core particles with a coating resin is not particularly limited and can be carried out by known methods. For example, there is a so-called immersion method in which the magnetic core particles and the coating resin solution are stirred while the solvent is evaporated, coating the surface of the magnetic core particles with the coating resin. Specifically, examples include a universal mixer / stirrer (manufactured by Fuji Powdal Co., Ltd.), a Nauta Mixer (manufactured by Hosokawa Micron Corporation), and a vacuum degassing kneader. Another method involves spraying the coating resin solution from a spray nozzle while forming a fluidized bed to coat the surface of the magnetic core particles with the coating resin. Specifically, examples include a Spira Coater (manufactured by Okada Seikou Co., Ltd.) and a Spira Flow (manufactured by Freund Industrial Co., Ltd.). There is also a method of dry coating the magnetic carrier core with the coating resin in granular form. Specifically, examples include processing methods using equipment such as a Hybridizer (manufactured by Nara Machine Works Co., Ltd.), MechanoFusion (manufactured by Hosokawa Micron Corporation), HighflexGral (manufactured by Fukae Powtech Co., Ltd.), and Theta Composer (manufactured by Tokuju Kogyo Co., Ltd.).

[0120] <Method for manufacturing a two-component developer> The two-component developer of this disclosure is a two-component developer having toner particles, a magnetic carrier, and inorganic fine particles B. The method for manufacturing the two-component developer is not particularly limited and includes a method of manufacturing by mixing toner particles, a magnetic carrier, and inorganic fine particles B, and a method of manufacturing by mixing toner obtained by mixing toner particles, an external additive, and inorganic fine particles B with a magnetic carrier.

[0121] Common mixing equipment can be used for mixing. Examples include the DoubleCon Mixer (manufactured by Nishimura Machinery Works Co., Ltd.), V-type Mixer (manufactured by Nishimura Machinery Works Co., Ltd.), Drum-type Mixer (manufactured by Eishin Co., Ltd.), Super Mixer (manufactured by Kawata Co., Ltd.), Henschel Mixer (manufactured by Nippon Coke Industries Co., Ltd.), and Nauta Mixer (manufactured by Hosokawa Micron Corporation). By using these devices, the toner and carrier are mixed uniformly, and the mixing properties of the replenishment developer and the developer in the developer unit are improved.

[0122] When toner is mixed with a magnetic carrier, the carrier mixing ratio is preferably 2% to 15% by mass, and more preferably 4% to 13% by mass, as the toner concentration in the two-component developer. Within this range, fogging and toner scattering can be effectively suppressed.

[0123] Furthermore, a two-component developer can also be manufactured by the following method. A step of mixing toner particles with an external additive other than inorganic fine particles B to obtain a toner particle mixture. A process of mixing a toner particle mixture with inorganic fine particles B to obtain toner, and A process of mixing toner and magnetic carrier to obtain a two-component developer, A method for producing a two-component developer having the following properties.

[0124] <Method for recovering inorganic fine particles B from a two-component developer (water washing method)> Inorganic fine particles B are recovered from the two-component developer using the following method. (i) Using a cleaning solution consisting of a surfactant and an organic builder, a mixture containing toner particles and inorganic fine particles B is recovered from the two-component developer. (ii) Inorganic fine particles B are recovered from the mixture recovered in (i) by density gradient centrifugation.

[0125] The following provides a detailed explanation of (i) and (ii) above.

[0126] (i) Prepare a washing solution by adding 1 g of Contaminon N (a 10% aqueous solution of pH 7 neutral detergent for cleaning precision measuring instruments, consisting of a nonionic surfactant, anionic surfactant, and organic builder, manufactured by Wako Pure Chemical Industries, Ltd.) and 50 g of deionized water to a 100 mL poly cup. Add 10 g of two-component developer to the poly cup and mix the washing solution and the two-component developer. Then, place a neodymium magnet on the bottom of the poly cup and collect the supernatant liquid.

[0127] Next, add 1g of Contaminon N and 50g of deionized water to the poly cup, and place a neodymium magnet on the bottom of the poly cup to collect the supernatant liquid. Repeat the above procedure three times, filter the obtained supernatant liquid to remove liquid components, and collect a mixture containing toner particles and inorganic fine particles B. Repeat the above collection procedure until the total amount of the mixture containing toner particles and inorganic fine particles B is 1g or more.

[0128] (ii) Add 160 g of sucrose (manufactured by Kishida Chemical Co., Ltd.) to 100 mL of deionized water and dissolve it while heating in a water bath to prepare a sucrose solution. Mix 31 g of this concentrated sucrose solution with 6 mL of Contaminon N (a 10% by mass aqueous solution of pH 7 neutral detergent for cleaning precision measuring instruments, consisting of a nonionic surfactant, anionic surfactant, and organic builder, manufactured by Wako Pure Chemical Industries, Ltd.) to prepare a dispersion. Add 1 g of the mixture containing the toner particles and inorganic fine particles B obtained above to this dispersion and shake in a shaker (NR-10, manufactured by Taitec Co., Ltd.) at a rate of 350 reciprocations per minute for 5 minutes. Transfer the shaken dispersion to a centrifugation tube and centrifuge in a centrifuge at a rate of 3500 rpm for 30 minutes.

[0129] After centrifugation, toner particles are present in the uppermost layer of the tube, while a mixture of inorganic fine particles B is present in the lower aqueous solution layer. The lower aqueous solution is collected and centrifuged to separate the dispersion from the mixture of inorganic fine particles B. If necessary, the centrifugation process is repeated to ensure sufficient separation, after which the dispersion is dried and the inorganic fine particles B are recovered. From the mass of the obtained inorganic fine particles B, the amount of inorganic fine particles B recovered per 100 parts by mass of the two-component developer (GB / m²) is calculated.

[0130] <Method for separating magnetic carriers from two-component developers> Prepare a cleaning solution by adding 1g of Contaminon N (a 10% by mass aqueous solution of a pH 7 neutral detergent for cleaning precision measuring instruments, consisting of a nonionic surfactant, anionic surfactant, and organic builder, manufactured by Wako Pure Chemical Industries, Ltd.) and 50g of deionized water to a 100mL poly cup. Add 10g of two-component developer to the poly cup and mix the cleaning solution and the two-component developer. Then, place a neodymium magnet on the bottom of the poly cup and remove the supernatant liquid.

[0131] Next, 1g of Contaminon N and 50g of deionized water are placed in the above-mentioned poly cup, and a neodymium magnet is placed on the bottom of the poly cup to remove the supernatant liquid. The above procedure is repeated three times. Magnetic carriers are obtained by drying the solid matter in the poly cup at 50°C. From the mass of the obtained magnetic carriers, the GC (parts by mass) content of magnetic carriers per 100 parts by mass of two-component developer is calculated.

[0132] The amount of magnetic carrier recovered per 100 parts by mass XB (parts by mass) as defined in this disclosure is calculated using GB and GC as follows: The amount of magnetic carrier recovered per 100 mass parts XB (mass parts) = 100 × GB / GC

[0133] <Method for separating magnetic core particles from carriers> 100 mL of methyl isobutyl ketone was added to 10 g of carrier material, and ultrasonic cleaning was performed at a power of 60 kHz for 15 minutes. After separating only the solid components using filter paper with a retained particle size of 7 μm, 100 mL of toluene was added, and the same ultrasonic cleaning and filtration process was repeated twice. Magnetic core particles were obtained by drying the resulting solid using a vacuum dryer.

[0134] <Method for separating inorganic microparticles A from a carrier> 10 mL of methyl isobutyl ketone was added to 10 g of carrier material, and ultrasonic cleaning was performed at 60 kHz for 15 minutes. After the liquid phase was recovered by decantation, 10 mL of toluene was added, and the same ultrasonic cleaning and liquid phase recovery process was repeated twice. After combining all the recovered liquid phases, the magnetic material (magnetic core particles) was removed from the liquid phase using a permanent magnet.

[0135] The obtained liquid phase was placed in a centrifuge and rotated at 15,000 rpm for 2 hours to separate the solid components. 20 mL of tetrahydrofuran was added to the obtained solid components, and sonication was applied to dissolve or disperse all the solid components in the liquid. The obtained liquid was placed in a centrifuge and rotated at 15,000 rpm for 2 hours to separate the solid components, and the solid components were vacuum-dried at 120°C for 24 hours using a vacuum dryer. The process of adding tetrahydrofuran, centrifuging, and drying was repeated twice to obtain inorganic fine particles A.

[0136] <Method for separating the coating resin from the carrier> 10 mL of methyl isobutyl ketone was added to 10 g of carrier material, and ultrasonic cleaning was performed at 60 kHz for 15 minutes. After the liquid phase was recovered by decantation, 10 mL of toluene was added, and the same ultrasonic cleaning and liquid phase recovery process was repeated twice. After combining all the recovered liquid phases, the magnetic material (magnetic core particles) was removed from the liquid phase using a permanent magnet.

[0137] The obtained liquid phase was placed in a centrifuge and rotated at 15,000 rpm for 2 hours to separate the solid components. The solvent of the obtained liquid phase was concentrated by vacuum distillation until the volume of the solution was approximately 1 mL. 15 mL of n-hexane was added to precipitate the solid components, and the solid components were filtered off using filter paper with a retaining particle size of 1 μm. Washing with 15 mL of n-hexane and filtering were repeated three times. The obtained solid components were dried in a vacuum dryer to obtain a coating resin.

[0138] <Measurement of the adhesion rate of inorganic fine particles B to toner particles> The adhesion rate of inorganic fine particles B to toner particles is measured as follows: First, the amount of inorganic fine particles B contained in 1g of toner is quantified. Next, the amount of inorganic fine particles B recovered from 1g of toner by the separation process described below is quantified. The adhesion rate is calculated using the following formula. Adhesion rate (%) = ((Amount of inorganic fine particles B in 1g of toner) - (Amount of inorganic fine particles B recovered from 1g of toner in the separation process)) / (Amount of inorganic fine particles B in 1g of toner) × 100

[0139] A sucrose solution is prepared by adding 160g of sucrose (manufactured by Kishida Chemical Co., Ltd.) to 100mL of deionized water and dissolving it in a water bath. A dispersion is prepared by mixing 31g of this concentrated sucrose solution with 6mL of Contaminon N (a 10% by mass aqueous solution of a pH 7 neutral detergent for cleaning precision measuring instruments, consisting of a nonionic surfactant, anionic surfactant, and organic builder, manufactured by Wako Pure Chemical Industries, Ltd.). 1g of toner is added to this dispersion and shaken for 5 minutes in a shaker (NR-10, manufactured by Taitec Co., Ltd.) at a rate of 350 reciprocations per minute. The shaken dispersion is transferred to a centrifuge tube and centrifuged in a centrifuge at 3500 rpm for 30 minutes.

[0140] After centrifugation, toner particles are present in the uppermost layer of the tube, while a mixture of inorganic microparticles B is present in the lower aqueous solution layer. The lower aqueous solution is collected and centrifuged to separate the dispersion from the mixture of inorganic microparticles B. If necessary, centrifugation is repeated to ensure sufficient separation, then the dispersion is dried to recover the inorganic microparticles B. The mass of the obtained inorganic microparticles B is defined as the amount of inorganic microparticles B recovered from 1 g of toner.

[0141] <Method for measuring the coverage rate of inorganic fine particles A on the surface of magnetic carrier particles> The coverage XA in this disclosure was measured by analyzing secondary electron images obtained using a scanning electron microscope.

[0142] Secondary electron images were acquired using a scanning electron microscope SU8220 (manufactured by Hitachi High-Tech Corporation). Specifically, magnetic carrier particles were fixed in a single layer on the sample stage for electron microscope observation using carbon tape, and observation was performed after a flushing operation. The observation conditions were as follows: SignalName=SE(U) Accelerating Voltage = 800V Standing distance = 8000 μm EmissionCurrent = 10000nA LensMode=High Condencer1=5000 ScanSpeed=slow3 ColorMode=Grayscale DataSize=1280x960 Magnification = 25000

[0143] During the measurement of the secondary electron image, the control software was set to a contrast of 60 and a brightness of -15. The image was acquired by capturing a resin layer as flat as possible in the center, minimizing the contrast caused by the surface shape. At this time, the image regions representing the resin layer and the inorganic fine particle A within the field of view can be distinguished by using EDX observation in conjunction.

[0144] By analyzing the obtained secondary electron images, the coverage rate of inorganic microparticles A exposed on the surface of magnetic carrier particles was calculated. Specifically, this was done by using the programming language "Python" and its extension libraries "OpenCV" and "NumPy" to perform image binarization and calculate the number of pixels with a brightness value of 255. The detailed method is as follows.

[0145] First, a 400x400 pixel area was cropped from a portion of the image. At this time, an image area was selected that, to the naked eye, contained only the coating resin and silica particles, and was as smooth as possible with minimal contrast due to surface irregularities. An example of this image is shown in Figure 1. Next, a median blur process was performed as shown in conditional equation (1) to remove noise. In conditional equation (1), "img" is a variable representing the input image. cv2.medianBlur(img,ksize=9) Conditional expression (1)

[0146] Furthermore, the denoised image was binarized to contain only pixels with a brightness value of 0 and pixels with a brightness value of 255. This process used the conditions shown in condition (2). In condition (2), "img" is a variable that represents the image after medial blurring. cv2.threshold(img,0,255,cv2.THRESH_OTSU) Conditional expression (2)

[0147] For the binarized image, the number of pixels with a brightness value of 255 was calculated, and the coverage rate of silica particles on the carrier surface was calculated by dividing this number by 160,000, which is the number of pixels contained within a 400x400 pixel area. The conditions used in this process are shown in conditional equation (3). In conditional equation (3), "img" is a variable that represents the image after binarization. (img / 255).sum() / 160000*100 Conditional expression (3)

[0148] The above procedure was performed on 50 particles, and the arithmetic mean of the 30 values ​​obtained by excluding the 1st to 10th values ​​and the 41st to 50th values ​​when sorted in order of coverage was defined as the coverage XA (area %) of inorganic fine particles A on the surface of the magnetic carrier particles.

[0149] <Measurement of the average height of the protrusions of inorganic fine particles A exposed on the surface of magnetic carrier particles> The cross-section of the magnetic carrier particles is observed using a transmission electron microscope (TEM), and the average height of the protrusions of the inorganic microparticles A exposed on the surface of the magnetic carrier particles is measured.

[0150] First, magnetic carrier particles are ion-milled using an argon ion milling apparatus (Hitachi High-Technologies Corporation, product name E-3500) to obtain a cross-section of the magnetic carrier particles. The ion milling measurement conditions are as follows. Beam diameter: 400 μm (full width at half maximum) Ion gun acceleration voltage: 5kV Ion gun discharge voltage: 4kV Ion gun discharge current: 463 μA

[0151] Next, the cross-section of the magnetic carrier particles is observed using a transmission electron microscope (JEOL Ltd., product name: JEM-2800) (TEM-EDX) at a magnification of 50,000x, in a field of view that allows confirmation of the outermost surface of the magnetic carrier particles. At this time, the cross-section of the coating resin layer and the cross-section of inorganic microparticle A at the outermost surface of the magnetic carrier particles within the field of view can be distinguished by using EDX observation in combination. From the observed image of the cross-section of inorganic microparticle A, the cross-sectional area of ​​inorganic microparticle A is determined, and the diameter of a circle with an area equal to that cross-sectional area (equivalent circle diameter) is determined. The image of the cross-section of inorganic microparticle A in which this equivalent circle diameter is within ±10% of the number-average particle size of inorganic microparticle A separated from the magnetic carrier particles is used for measurement.

[0152] Figure 2 shows a schematic diagram illustrating the method for measuring the average height of the protrusions of inorganic microparticles A exposed on the surface of magnetic carrier particles. In the observed image, the contour line of inorganic microparticles A that are in contact with the coating resin layer is defined as contour line X, and the contour lines of inorganic microparticles A other than contour line X are defined as contour line Y. Inorganic microparticles A having contour lines X and Y are determined to be inorganic microparticles A exposed on the surface of magnetic carrier particles and are to be measured. For the inorganic microparticles A to be measured, the endpoints of contour line X are connected by a straight line to determine the baseline Z. Among the perpendiculars connecting baseline Z and contour line Y, the perpendicular line L with the longest length is determined, and the length of perpendicular line L is measured.

[0153] Following the procedure described above, the perpendicular L of 100 inorganic microparticles A exposed on the surface of the magnetic carrier particles was measured. The arithmetic mean of the 100 obtained measurements was taken as the average height HA (nm) of the convex portion.

[0154] <Measurement of the number-average particle size of primary inorganic microparticles> First, 5.0 g of Triton-X100 (manufactured by Kishida Chemical Co., Ltd.) was added to 95.0 g of RO water to prepare a 5% Triton-X100 aqueous solution (hereinafter referred to as 5% Triton solution). A solution was then prepared by adding 0.2 g of the 5% Triton solution and 19.8 g of RO water to 10 mg of dried inorganic microparticles. Next, a dispersion was obtained by immersing the tip of the probe of an ultrasonic disperser in the above solution and ultrasonically dispersing at an output of 20 W for 15 minutes. Subsequently, the number-average particle size (nm) of the primary particles of the inorganic microparticles was measured using this dispersion with a dynamic light scattering (DLS) particle size distribution analyzer (product name: NanoTrac 150, manufactured by MicroTrac Bell). Mode: Transparent Particle condition: Spherical Particle refractive index: 1.45 Particle density: 1.30 Refractive index of dispersion medium: 1.33 (water) Measurement time: 120 seconds

[0155] <Method for measuring the 50% diameter (D50) of the volume distribution of magnetic carriers> Particle size distribution was measured using the "Microtrac MT3300EX" laser diffraction / scattering particle size distribution analyzer (manufactured by Nikkiso Co., Ltd.).

[0156] The 50th percentile diameter (D50) of the volume distribution of magnetic carriers and magnetic core particles was measured using a dry sample feeder, the "Turbotrac One-Shot Dry Sample Conditioner" (manufactured by Nikkiso Co., Ltd.). For the Turbotrac's supply conditions, a dust collector was used as a pressure source, with an airflow of approximately 33 L / sec and a pressure of approximately 17 kPa. Control was performed automatically using the included software (version 10.3.3-202D), and analysis was also performed using the same software. The measurement conditions are as follows. SetZero time: 10 seconds Measurement time: 10 seconds Number of measurements: 1 Particle refractive index: 1.81 Particle shape: non-spherical Measurement limit: 1408 μm Measurement lower limit: 0.243μm Measurement environment: Temperature 23°C, relative humidity 50%

[0157] <Measurement of Compression Energy of Inorganic Microparticles> The compression energy of inorganic microparticles is measured using a powder rheometer (FT4, Freeman Technology). First, 10 g of inorganic microparticles is weighed into a dedicated cylindrical split container, and the inorganic microparticles are compressed to a specified pressure (30 kPa) using a compression test piston attached to the main unit. The compressed inorganic microparticle layer is scraped off at the split portion of the measuring container, removing the upper part of the powder layer. Next, a dedicated needle-shaped jig is attached to the main unit and inserted perpendicularly into the powder layer. The compression energy (mJ) is obtained by measuring the force of penetration at this time.

[0158] <Measurement of work function of inorganic microparticles> The work function of inorganic microparticles is measured using a photoelectron spectrometer (AC-3; manufactured by RIKEN Keiki Co., Ltd.). The inorganic microparticles are spread out and placed in the measurement holder. The measurement conditions are as follows. UV light source: Deuterium lamp Irradiation light intensity: 150nW Spot size: 2 x 5 mm Energy scanning range: 4.0eV~7.0eV Measurement time: 10 seconds / 1 point

[0159] Measurements are taken under the above conditions, and the work function of inorganic microparticles is obtained by performing calculations using the work function calculation software of the same device. The work function is measured with a repeatability (standard deviation) of 0.02 eV. [Examples]

[0160] Examples and comparative examples are shown below to illustrate the present disclosure in detail. The materials, additives, amounts and concentrations used, and processing methods and procedures shown below may be modified as appropriate without departing from the spirit of this disclosure, and the form of this disclosure should not be interpreted restrictively based on the content of the examples.

[0161] In the following explanation, unless otherwise specified, "%" and "parts" refer to mass.

[0162] <Examples of toner manufacturing> <Example of resin A manufacturing process> Polyoxypropylene (2,2)-2,2-bis(4-hydroxyphenyl)propane: 76.3 parts Terephthalic acid: 16.1 parts Succinic acid: 7.6 parts Titanium tetrabutoxide (esterification catalyst): 0.5 parts

[0163] The above materials were weighed into a reaction vessel equipped with a condenser, stirrer, nitrogen inlet tube, and thermocouple. Next, the reaction vessel was purged with nitrogen gas, and the temperature was gradually increased while stirring. The reaction was carried out at 200°C for 4 hours while stirring. Furthermore, the pressure inside the reaction vessel was reduced to 8.3 kPa and maintained for 1 hour, after which it was cooled to 160°C and returned to atmospheric pressure (first reaction step). • tert-butylcatechol (polymerization inhibitor): 0.1 part

[0164] Subsequently, the above materials were added, the pressure in the reaction vessel was reduced to 8.3 kPa, and the reaction was allowed to proceed for 1 hour while maintaining the temperature at 180°C. After confirming that the softening point, measured according to ASTM D36-86, reached 90°C, the temperature was lowered to stop the reaction (second reaction step), yielding amorphous resin A. The obtained resin A had a peak molecular weight Mp of 4500, a softening point Tm of 90°C, and a glass transition temperature Tg of 54°C.

[0165] <Example of resin B manufacturing> Polyoxypropylene (2,2)-2,2-bis(4-hydroxyphenyl)propane: 74.8 parts Terephthalic acid: 12.9 parts • Adipic acid: 7.9 parts Titanium tetrabutoxide (esterification catalyst): 0.5 parts

[0166] The above materials were weighed into a reaction vessel equipped with a condenser, stirrer, nitrogen inlet tube, and thermocouple. Next, the reaction vessel was purged with nitrogen gas, and the temperature was gradually increased while stirring. The reaction was carried out at 200°C for 2 hours while stirring. Furthermore, the pressure inside the reaction vessel was reduced to 8.3 kPa and maintained for 1 hour, after which it was cooled to 160°C and returned to atmospheric pressure (first reaction step). Trimellitus: 5.9 parts • tert-butylcatechol (polymerization inhibitor): 0.1 part

[0167] Subsequently, the above materials were added, the pressure in the reaction vessel was reduced to 8.3 kPa, and the reaction was carried out for 15 hours while maintaining the temperature at 200°C. After confirming that the softening point, measured according to ASTM D36-86, reached 140°C, the temperature was lowered to stop the reaction (second reaction step), and amorphous resin B was obtained. The obtained resin B had a peak molecular weight Mp of 10000, a softening point Tm of 140°C, and a glass transition temperature Tg of 60°C.

[0168] <Examples of resin C manufacturing> • 1,6-Hexanediol: 33.9 parts Dodecanedioic acid: 66.1 parts

[0169] The above materials were weighed into a reaction vessel equipped with a condenser, stirrer, nitrogen inlet tube, and thermocouple. Next, the reaction vessel was purged with nitrogen gas, and the temperature was gradually increased while stirring. The mixture was then reacted at 140°C while stirring for 3 hours. • Tin 2-ethylhexanoate: 0.5 parts

[0170] Subsequently, the above materials were added, the pressure in the reaction vessel was reduced to 8.3 kPa, and the reaction was carried out for 4 hours while maintaining the temperature at 200°C to obtain crystalline resin C (first reaction step). The obtained resin C had a weight-average molecular weight Mw of 11000 and a melting peak temperature Tp of 72°C.

[0171] <Example of dispersant D production> Low molecular weight polypropylene (Viscol 660P, manufactured by Sanyo Chemical Industries, Ltd.): 10.0 parts Xylene: 25.0 parts

[0172] The above materials were weighed into a reaction vessel equipped with a condenser, stirrer, nitrogen inlet tube, and thermocouple. Next, the reaction vessel was purged with nitrogen gas, and the temperature was gradually raised to 175°C while stirring. Styrene: 65.0 parts Cyclohexyl acrylate: 5.5 parts Butyl acrylate: 12.5 parts • Methacrylic acid: 5.5 parts Xylene: 10.0 parts • Di-t-butylperoxyhexahydroterephthalate: 0.5 parts

[0173] Subsequently, the above materials were added dropwise over 3 hours, and the mixture was stirred for a further 30 minutes. Next, the solvent was removed by distillation to obtain dispersant D, in which a styrene-acrylic polymer was graft-polymerized onto a polyolefin. Dispersant D had a peak molecular weight of Mp6000 and a softening point of 125°C.

[0174] <Example of manufacturing inorganic fine particles B1> After de-ironizing and bleaching the metatitanic acid obtained by the sulfuric acid method, a sodium hydroxide aqueous solution was added to adjust the pH to 9.0 for desulfurization. Subsequently, the pH was neutralized to 5.8 with hydrochloric acid and then filtered and washed. Water was added to the washed cake to form a slurry with a TiO2 concentration of 1.5 mol / L, and then hydrochloric acid was added to adjust the pH to 1.5 for dispactation.

[0175] The desulfurized and disintegrated metatitanic acid was collected as TiO2 and placed in a 3L reaction vessel. To the disintegrated metatitanic acid slurry, an aqueous strontium chloride solution was added to achieve a SrO / TiO2 molar ratio of 1.15, and the TiO2 concentration was adjusted to 0.8 mol / L.

[0176] Next, the mixture was heated to 90°C while stirring, and then 444 mL of 10 mol / L sodium hydroxide aqueous solution was added over 50 minutes while microbubbling nitrogen gas at 600 mL / min. After that, the mixture was stirred at 95°C for 1 hour while microbubbling nitrogen gas at 400 mL / min.

[0177] Subsequently, the reaction slurry was rapidly cooled to 15°C by stirring while 10°C cooling water flowed through the jacket of the reaction vessel. Hydrochloric acid was added until the pH reached 2.0, and stirring continued for 1 hour. After decanting the obtained precipitate, 6 mol / L hydrochloric acid was added to adjust the pH to 2.0. 4.6 parts of 3,3,3-trifluoropropyltrimethoxysilane and 4.6 parts of i-butyltrimethoxysilane were added per 100 parts of solids, and the mixture was stirred for 18 hours. The mixture was neutralized with a 4 mol / L aqueous sodium hydroxide solution, stirred for 2 hours, filtered, and separated. The mixture was then dried in air at 120°C for 8 hours to obtain inorganic fine particles B1, in which the substrate is strontium titanate. The physical properties of the obtained inorganic fine particles B1 are shown in Table 1.

[0178] <Manufacturing examples of inorganic fine particles B2-B5> Inorganic fine particles B2 to B5 were manufactured using the same method as for inorganic fine particles B1, but with the type and amount of surface treatment agent added changed as shown in Table 3. Their physical properties are shown in Table 1.

[0179] <Inorganic fine particles B6> Titanium oxide nanoparticles surface-treated with isobutyltrimethoxysilane (Titanium Industry: ST-570) were used as inorganic nanoparticles B6. Their physical properties are shown in Table 1.

[0180] <Inorganic fine particles B7> Hydrophobic dry silica nanoparticles (Shin-Etsu Chemical Co., Ltd.: X24-9600) surface-treated with hexamethyldisilazane were used as inorganic nanoparticles B7. Their physical properties are shown in Table 1.

[0181] [Table 1]

[0182] <Example of Toner 1 manufacturing> • Resin A: 62 parts ·Resin B: 28 parts ·Resin C: 10 parts • Dispersant D: 4 parts Fischer-Tropsch wax (peak temperature of maximum endothermic peak: 90°C): 4 parts ·7 parts of C.I. Pigment Blue 15:3

[0183] Using a Henschel mixer (FM-75 type, manufactured by Mitsui Mining Co., Ltd.), the above materials were mixed at a rotation speed of 20 s -1 and a rotation time of 5 minutes, and then kneaded with a twin-screw kneader (PCM-30 type, manufactured by Ikegai Corporation) set at a temperature of 130°C. The obtained kneaded product was cooled and coarsely pulverized to 1 mm or less with a hammer mill to obtain a coarsely pulverized product. The obtained coarsely pulverized product was finely pulverized with a mechanical pulverizer (T-250, manufactured by Turbo Industry Co., Ltd.). Further, classification was performed using a Faculty F-300 (manufactured by Hosokawa Micron Corporation) to obtain toner particles. The operating conditions of the Faculty were a classification rotor rotation speed of 130 s -1 and a dispersion rotor rotation speed of 120 s -1 as such.

[0184] To 100 parts of the obtained toner particles, 1.0 part of hydrophobic silica particles (BET: 200 m 2 / g, compression energy: 85 mJ) was mixed with a Henschel mixer (FM-75 type, manufactured by Mitsui Miike Chemical Co., Ltd.) at a rotation speed of 30 s -1 and a rotation time of 10 minutes to obtain a toner particle mixture. To the obtained toner particle mixture, 0.6 part of inorganic fine particles B1 was added and mixed with a Henschel mixer (FM-75 type, manufactured by Mitsui Miike Chemical Co., Ltd.) at a rotation speed of 30 s -1 and a rotation time of 1 minute to obtain Toner 1. When the weight average particle diameter (D4) of the toner was measured with a "CDA-1000X" (aperture diameter: 100 μm, manufactured by Sysmex Corporation), it was 5.8 μm. When the average circularity of the toner was measured with a flow-type particle image analyzer "FPIA-3000" (manufactured by Sysmex Corporation), it was 0.963. The physical properties are shown in Table 2.

[0185] <Production Example of Toner 13> ·Resin A: 62 parts ·Resin B: 28 parts ·Resin C: 10 parts ·Dispersant D: 4 parts ·Fisher-Tropsch wax (peak temperature of the maximum endothermic peak: 90°C): 4 parts CI Pigment Blue 15:3:7 parts

[0186] The above materials were mixed using a Henschel mixer (FM-75 model, manufactured by Mitsui Mining Co., Ltd.) at a rotation speed of 20 seconds. -1 After mixing for 5 minutes, the mixture was kneaded in a twin-screw mixer (PCM-30 model, manufactured by Ikegai Co., Ltd.) set to a temperature of 130°C. The resulting mixture was cooled and coarsely ground to less than 1 mm in a hammer mill to obtain coarse material. The obtained coarse material was finely ground in a mechanical grinder (T-250, manufactured by Turbo Kogyo Co., Ltd.). Further classification was performed using a Faculty F-300 (manufactured by Hosokawa Micron Corporation) to obtain toner particles. The operating conditions for the Faculty were a classification rotor rotation speed of 130 s. -1 , the distributed rotor rotation speed is set to 120s -1 That's what I decided.

[0187] To 100 parts of the obtained toner particles, hydrophobic silica particles (BET: 200m) 2 Add 1.0 part (compression energy: 85 mJ / g) and mix in a Henschel mixer (FM-75 model, manufactured by Mitsui Miike Chemical Machinery Co., Ltd.) at a rotation speed of 30s. -1 The mixture was rotated for 10 minutes to obtain toner 13. The weight-average particle size (D4) of the toner was measured using a "CDA-1000X" (aperture diameter: 100 μm, manufactured by Sysmex Corporation) and was found to be 5.8 μm. The average circularity of the toner was measured using a flow-type particle image analyzer "FPIA-3000" (manufactured by Sysmex Corporation) and was found to be 0.963. The physical properties are shown in Table 2.

[0188] <Manufacturing examples for toners 2-12> Toners 3 to 12 were obtained in the same manner as in the manufacturing example of toner 2, except that the type and amount of inorganic fine particles B added, and the external additive conditions were changed as shown in Table 2. The physical properties are shown in Table 2.

[0189] [Table 2]

[0190] <Example of manufacturing inorganic fine particles A1> 100 parts methanol and 16 parts 15% aqueous ammonia were added to a glass reaction vessel equipped with a stirrer and two dropper systems, and the resulting mixture was stirred at 35°C under a nitrogen stream. The stirrer speed was adjusted to 150 rpm, and tetramethoxysilane and 5.4% aqueous ammonia were added dropwise simultaneously. The dropper systems were set to add at rates of 31.1 parts per hour and 13.4 parts per hour, respectively. After adding tetramethoxysilane for 6 hours and 5.4% aqueous ammonia for 5 hours, the mixture was stirred for 10 minutes while maintaining the temperature to obtain an inorganic fine particle substrate dispersion.

[0191] The inorganic microparticle substrate was recovered from the obtained inorganic microparticle substrate dispersion by suction filtration, and then heated in a 400°C oven for 10 minutes to obtain inorganic microparticle substrate.

[0192] 100 parts of the obtained inorganic fine particle substrate were placed in an autoclave, and the autoclave was purged with nitrogen. While stirring the inorganic fine particle substrate in the autoclave, 0.7 parts of hexamethyldisilazane and 0.2 parts of distilled water, atomized using a two-fluid nozzle, were uniformly sprayed onto it. The autoclave was sealed and stirred for 30 minutes, then heated at 200°C for 2 hours. After that, the internal pressure was reduced while still heating to obtain inorganic fine particles A1, in which the substrate is silica. The physical properties of the obtained inorganic fine particles A1 are shown in Table 3.

[0193] <Examples of manufacturing inorganic fine particles A2 and A3> Inorganic fine particles A2 and A3 were obtained in the same manner as for inorganic fine particles A1, except that the amount of methanol added was changed. The physical properties are shown in Table 3.

[0194] <Inorganic fine particles A4~A6> Commercially available barium titanate with different number-average particle sizes was used as inorganic fine particles A4 to A6. The physical properties are shown in Table 3.

[0195] <Inorganic fine particles A7> Commercially available strontium titanate treated with n-octyltriethoxysilane was used as inorganic fine particles A7. Its properties are shown in Table 3.

[0196] [Table 3]

[0197] <Examples of magnetic core particle manufacturing> Process 1 (Weighing and Mixing Process) • Fe2O3: 68.3% • MnCO3: 28.5% Mg(OH)2: 2.0% • SrCO3: 1.2% The ferrite raw materials were weighed to achieve the following result.

[0198] Subsequently, 20 parts of distilled water were added to 80 parts of the above ferrite raw material mixture, and the mixture was ground and mixed for 3 hours using a zirconia ball (φ10 mm) in a ball mill to obtain a slurry.

[0199] Step 2 (Calibration Process) The slurry was dried using a spray dryer (manufactured by Okawara Chemical Machinery Co., Ltd.), and then calcined in a batch-type electric furnace under a nitrogen atmosphere (oxygen concentration 1.0 vol%) at a temperature of 1050°C for 3.0 hours to obtain calcined ferrite.

[0200] Step 3 (Grinding Process) Calcined ferrite was crushed to approximately 0.5 mm using a crusher, and then ground for 3 hours in a wet bead mill using 1 / 8-inch diameter stainless steel beads. Furthermore, using zirconia balls (φ1.0 mm), it was ground for 4 hours in a wet ball mill to obtain a calcined ferrite slurry.

[0201] Process 4 (granulation process) 1.0 part by mass of ammonium polycarboxylate and 1.5 parts by mass of polyvinyl alcohol were added to 100 parts by mass of calcined ferrite slurry, and the mixture was granulated into 37 μm spherical particles using a spray dryer (manufactured by Okawara Chemical Machinery). The resulting granules were heated in a rotary electric furnace at 700°C for 2 hours.

[0202] Step 5 (Firing Process) Under a nitrogen atmosphere (oxygen concentration 1.0 vol%), the temperature was raised from room temperature to the firing temperature (1100°C) in 2 hours, and then maintained at 1100°C for 4 hours for firing. After that, the temperature was lowered to 60°C over 8 hours, the atmosphere was changed from nitrogen to air, and the product was removed at a temperature of 40°C or lower.

[0203] Process 6 (Sorting Process) The aggregated particles were crushed, sieved with a 150 μm mesh to remove coarse particles, and then air-driven classification removed the fine powder. Further magnetic separation removed the low-magnetic-field components to obtain magnetic core particles. Observation of the shape of the magnetic core particles using a scanning electron microscope SU8220 (manufactured by Hitachi High-Tech Corporation) revealed that they were porous and contained pores.

[0204] <Examples of magnetic core particle manufacturing> 100.0 parts of the above magnetic core particles were placed in the stirring vessel of a mixing and stirring machine (Dalton NDMV type universal stirring machine), and while maintaining the temperature at 60°C, the pressure was reduced to 2.3 kPa and the inside of the stirring vessel was replaced with nitrogen. 10.0 parts of silicone resin solution (product name SR2410, manufactured by Toray Dow Corning), 89.9 parts of toluene, and 0.1 parts of titanium n-butoxide were mixed and stirred for 10 minutes using a multi-blender mixer. The amount added was such that the resin component amounted to 7.5 parts. After the addition was complete, stirring was continued for 2 hours. Furthermore, the temperature was raised to 70°C, and the solvent was removed under reduced pressure to fill the pores inside the magnetic core particles with the silicone resin composition and coat the surface of the magnetic core particles with the silicone resin composition. After cooling, the obtained particles were transferred to a rotatable mixing vessel in a mixer with spiral blades (Drum mixer UD-AT type manufactured by Sugiyama Heavy Industries Co., Ltd.), and heated to 220°C at a heating rate of 2°C / min under a nitrogen atmosphere and atmospheric pressure. The mixture was heated and stirred at this temperature for 60 minutes to cure the silicone resin. After curing, low-magnetic-force particles were separated by magnetic separation, and the particles were classified using a sieve with an opening of 150 μm to obtain carrier core particles filled with silicone resin.

[0205] <Examples of resin coating liquid manufacturing> 80 parts of cyclohexyl methacrylate and 20 parts of methyl methacrylate were added to a four-necked flask equipped with a reflux condenser, thermometer, nitrogen suction tube, and ground-joint stirring device.

[0206] Furthermore, 100 parts of toluene, 100 parts of methyl ethyl ketone, and 2.0 parts of azobisisovaleronitrile were added. The resulting mixture was held at 70°C under a nitrogen stream for 10 hours to carry out polymerization. After the polymerization reaction was complete, hexane was injected to precipitate the copolymer, the precipitate was filtered off, and then vacuum-dried to obtain the coating resin.

[0207] To the obtained coating resin, toluene and methyl ethyl ketone were added in a 1:1 ratio to obtain a coating resin solution (5% solids) with a solids content of 5%. Furthermore, 25 parts of inorganic fine particles A1 were added to 2000 parts of the coating resin solution (100 parts resin solids), and the resulting mixture was shaken and stirred for 15 minutes using a paint shaker (manufactured by RADIA) to obtain a resin coating liquid.

[0208] <Example of manufacturing magnetic carrier 1> • Magnetic core particles: 100 units • Resin coating liquid: 40 parts

[0209] The above materials were placed in a planetary mixer (Nauta Mixer VN type, manufactured by Hosokawa Micron Corporation) maintained under reduced pressure (1.5 kPa) and at a temperature of 60°C. The process involved first adding the entire amount of magnetic core particles, then adding 1 / 3 of the resin coating solution, and performing solvent removal and coating operations for 20 minutes. Next, another 1 / 3 of the resin coating solution was added, and solvent removal and coating operations were performed for 20 minutes, followed by the final 1 / 3 of the resin coating solution, and solvent removal and coating operations for 20 minutes.

[0210] Subsequently, the magnetic carriers coated with the coating resin composition were transferred to a mixer with spiral blades (Drum mixer UD-AT type manufactured by Sugiyama Heavy Industries Co., Ltd.) in a rotatable mixing container. The mixture was heat-treated at 120°C for 2 hours under a nitrogen atmosphere while stirring by rotating the mixing container 10 times per minute. The obtained magnetic carriers were separated for low magnetic force by magnetic separation, passed through a sieve with an opening of 150 μm, and then classified in an air classifier to obtain magnetic carrier 1. The physical properties of the obtained magnetic carrier 1 are shown in Table 4.

[0211] <Manufacturing examples of magnetic carriers 2-10> In the example of manufacturing magnetic carrier 1, magnetic carriers 2 to 10 were obtained in the same manner as magnetic carrier 1, except that the type and amount of inorganic fine particles A added to the resin coating liquid were changed as shown in Table 4. The physical properties are shown in Table 4.

[0212] [Table 4]

[0213] <Example of manufacturing a two-component developer 1> 92 parts by mass of magnetic carrier 1 were mixed with 8 parts by mass of toner 1 and mixed for 5 minutes using a V-type mixer (V-20, manufactured by Seishin Corporation) to obtain a two-component developer 1. The physical properties are shown in Table 5. Since toner 1 contains toner particles and inorganic fine particles B, the two-component developer contains toner particles, inorganic fine particles B, and magnetic carriers. This is also true for other two-component developers.

[0214] As a result of recovering inorganic fine particles B from the two-component developer 1 by washing with water, the amount of inorganic fine particles B recovered per 100 parts by mass of carrier was 0.03 parts by mass.

[0215] <Two-component developer 2-20> In the example of the production of two-component developer 1, the same procedure was followed except that the magnetic carriers were changed to the combinations shown in Table 5 to obtain two-component developers 2 to 20. The physical properties are shown in Table 5.

[0216]

Table 5

[0217] <Evaluation method> (1) Evaluation of image quality The full-color copier imagePRESS V1000 manufactured by Canon was modified so that images could be output using only the developer at the cyan position. Also, the developing contrast was made adjustable to any value, and the automatic correction of image density by the main body was disabled. The image formation speed was set to 100 sheets per minute. Two-component developer was put into the developer at the cyan position, images were output, and various evaluations were carried out while conducting a durability test. The evaluation paper used was GF-C081 (81.4 g / m 2 )(Canon Marketing Japan Inc.).

[0218] Under a high-temperature and high-humidity environment (30°C, 80% RH), 50,000 images (A4 landscape) with a printing ratio of 40% were output. After that, one halftone image (A4 landscape, 30H) was output. Note that the 30H image is a value obtained by displaying 256 gradations in hexadecimal, and it is a halftone image when 00H is solid white (non-image) and FFH is solid black (full-image). The dot area in the obtained halftone image was measured, and the image quality was evaluated by quantifying the variation in dot area (hereinafter, dot reproducibility index (I)).

[0219] The dot reproducibility index (I) was calculated as follows. Using a digital microscope VHX-500 (lens wide-range zoom lens VH-Z100 manufactured by Keyence Corporation), the areas of 1000 dots in the halftone image were measured. From the average value (S) and standard deviation (σ) of the obtained dot areas based on the number of dots, the dot reproducibility index (I) was calculated by the following formula, and the image quality was evaluated according to the following criteria. The evaluation results are shown in Table 6. Dot reproducibility index (I) = σ / S × 100 A: Dot reproducibility index (I) is less than 4.0 B: Dot reproducibility index (I) is 4.0 or more and less than 6.0 C: Dot reproducibility index (I) is 6.0 or more and less than 8.0 D: Dot Reproducibility Index (I) is 8.0 or higher

[0220] (2) Evaluation of changes in image density A Canon imagePRESS C800 full-color copier was modified to output images using only the cyan-positioned developer unit. Additionally, the mechanism for discharging excess magnetic carriers from the developer unit was removed. A two-component developer was placed in the cyan-positioned developer unit, and toner was placed in the cyan toner container for the evaluation described below. A4-sized GF-C081 (81.4g / m²) paper was used for the evaluation. 2 (Canon Marketing Japan Inc.) was used. The amount of toner on the paper in the FFH image (solid image) was 0.45 mg / cm². 2 I adjusted it so that it would be as follows.

[0221] An image output test of 1,000 sheets was conducted under high temperature and high humidity conditions (30°C, 80%RH) with a print ratio of 1%. During the continuous feeding of 1,000 sheets, the same development and transfer conditions (without calibration) as the first sheet were used. Subsequently, an image output test of 1,000 sheets was conducted with a print ratio of 80%. During the continuous feeding of 1,000 sheets, the same development and transfer conditions (without calibration) as the first sheet were used.

[0222] The image density of the printed images was measured using an X-Rite color reflectance densitometer (500 series: manufactured by X-Rite). The image density of the 1,000th image in the image output test at a print ratio of 1% was defined as the initial density, and the image density of the 1,000th image in the image output test at a print ratio of 80% was defined as the post-test density. The absolute value of the difference between the initial density and the post-test density (image density difference Δ) was calculated, and the image density change was evaluated according to the following criteria. For density measurement, measurements were repeated a sufficient number of times to minimize measurement error, and the arithmetic mean of these measurements was adopted as the measured value. The evaluation results are shown in Table 6. A: Image density difference Δ is less than 0.02 B: Image density difference Δ is 0.02 or greater and less than 0.05 C: Image density difference Δ is 0.05 or greater and less than 0.10 D: Image density difference Δ is 0.10 or greater

[0223] (3) Evaluation of charge retention The amount of triboelectric charge on the toner was calculated by collecting the toner on the electrostatic latent image carrier using a metal cylindrical tube and a cylindrical filter.

[0224] Specifically, the amount of triboelectric charge on the toner on the electrostatic latent image carrier was measured using a Faraday cage. A Faraday cage is a coaxial double cylinder with the inner and outer cylinders insulated from each other. If a charged object with charge Q is placed inside the inner cylinder, electrostatic induction makes it behave as if a metal cylinder with charge Q were present. This induced charge was measured using an electrometer (Kessley 6517A, manufactured by Kessley), and the amount of charge Q (mC) divided by the toner mass M (kg) in the inner cylinder (Q / M) was defined as the amount of triboelectric charge on the toner. The amount of triboelectric charge on toner (mC / kg) = Q / M Evaluation image: A 2cm x 5cm image of FFh is placed in the center of an A4 sheet of paper.

[0225] First, the evaluation image described above was formed on the electrostatic latent image carrier under high temperature and high humidity conditions (30°C, 80%RH). Before the image was transferred to the intermediate transfer medium, the rotation of the electrostatic latent image carrier was stopped, and the toner on the electrostatic latent image carrier was collected by suction using a metal cylindrical tube and a cylindrical filter. The initial Q / M ratio on the electrostatic latent image carrier was then measured.

[0226] Subsequently, under high temperature and high humidity conditions (30°C, 80%RH), the developer was left inside the evaluation machine (Canon imagePRESS C800 full-color copier) for two weeks. After that, the same operations as before the storage were performed, and the Q / M on the electrostatic latent image carrier after storage (Q / M after storage) was measured. The retention rate of Q / M after storage was calculated using the following formula, and the charge retention performance was evaluated according to the following criteria. For the measurement of Q / M, measurements were repeated a sufficient number of times to minimize the measurement error, and the arithmetic mean of these measurements was adopted as the measured value. The evaluation results are shown in Table 6. Q / M maintenance rate (%) = (Q / M after hiatus) / (Initial Q / M) × 100 A: Q / M maintenance rate is 98% or higher B:Q / M maintenance rate is between 95% and 98% C:Q / M maintenance rate is between 90% and 95% D:Q / M maintenance rate is less than 90%

[0227] [Table 6]

[0228] This disclosure relates to the following configuration.

[0229] (Composition 1) A two-component developer containing toner particles, a magnetic carrier, and inorganic fine particles B, The magnetic carrier has magnetic carrier particles, The magnetic carrier particle comprises a magnetic core particle and a coating resin layer that covers the surface of the magnetic core particle. The coating resin layer contains inorganic fine particles A, At least a portion of the inorganic fine particles A is exposed on the surface of the magnetic carrier particles, Regarding the amount of inorganic fine particles B recovered from the two-component developer by a water washing method, when the amount recovered per 100 parts by mass of the magnetic carrier is XB (parts by mass), XB is between 0.01 parts by mass and 0.05 parts by mass. The inorganic fine particles B have a compression energy of 75 mJ or less, as measured in the state of a powder layer formed by compressing at 30 kPa. When the work functions of inorganic fine particles A and B are WA(eV) and WB(eV), respectively, WA and WB satisfy the following equation (1), 0.5 ≤ |WA - WB| ≤ 10.0 Equation (1) When the coverage rate of the inorganic fine particles A on the surface of the magnetic carrier particle is XA (area %), XA and XB satisfy the following equation (2), 0.001≦XB / XA≦0.010 Formula (2) When the average value of the convex height of the inorganic fine particle A exposed on the surface of the magnetic carrier particles is HA (nm), and the number average particle diameter of the primary particles of the inorganic fine particle B recovered by the water washing method is HB (nm), the two-component developer is characterized in that HA and HB satisfy the following formula (3). 0.5 ≦ HB / HA ≦ 4.0 Formula (3)

[0230] (Configuration 2) The two-component developer according to Configuration 1, wherein the inorganic fine particle A is silica fine particles.

[0231] (Configuration 3) The two-component developer according to Configuration 1 or 2, wherein the inorganic fine particle B is strontium titanate fine particles.

[0232] (Configuration 4) The two-component developer according to any one of Configurations 1 to 3, wherein the inorganic fine particle B is a surface-treated inorganic fine particle, and the surface treatment agent is at least one selected from the group consisting of a silane coupling agent, a fluorosilane coupling agent, a fatty acid, and a fatty acid metal salt.

[0233] (Configuration 5) A method for producing a two-component developer for producing the two-component developer according to Configurations 1 to 4, The production method is A step of mixing the toner particles and an external additive other than the inorganic fine particle B to obtain a toner particle mixture, A step of mixing the toner particle mixture and the inorganic fine particle B to obtain a toner, and A step of mixing the toner and the magnetic carrier to obtain a two-component developer. A method for producing a two-component developer having the above steps.

Claims

1. A two-component developer containing toner particles, a magnetic carrier, and inorganic fine particles B, The magnetic carrier has magnetic carrier particles, The magnetic carrier particle comprises a magnetic core particle and a coating resin layer that covers the surface of the magnetic core particle. The coating resin layer contains inorganic fine particles A, At least a portion of the inorganic fine particles A is exposed on the surface of the magnetic carrier particles, Regarding the amount of inorganic fine particles B recovered from the two-component developer by a water washing method, when the amount recovered per 100 parts by mass of the magnetic carrier is XB (parts by mass), XB is between 0.01 parts by mass and 0.05 parts by mass. The inorganic fine particles B have a compression energy of 75 mJ or less, as measured in the state of a powder layer formed by compressing at 30 kPa. When the work functions of inorganic particles A and inorganic particles B are WA (eV) and WB (eV), respectively, WA and WB satisfy the following equation (1), 0.5 ≤ |WA - WB| ≤ 10.0 Equation (1) When the coverage rate of the inorganic fine particles A on the surface of the magnetic carrier particle is XA (area %), XA and XB satisfy the following formula (2), 0.001≦XB / XA≦0.010 Formula (2) A two-component developer characterized in that, when the average height of the protrusions of the inorganic fine particles A exposed on the surface of the magnetic carrier particles is HA (nm), and the number-average particle size of the primary particles of the inorganic fine particles B recovered by the water washing method is HB (nm), HA and HB satisfy the following formula (3). 0.5≦HB / HA≦4.0 Formula (3)

2. The two-component developer according to claim 1, wherein the inorganic fine particles A are silica fine particles.

3. The two-component developer according to claim 1 or 2, wherein the inorganic fine particles B are strontium titanate fine particles.

4. The two-component developer according to claim 1 or 2, wherein the inorganic fine particles B are surface-treated inorganic fine particles, and the surface treatment agent is at least one selected from the group consisting of silane coupling agents, fluorine silane coupling agents, fatty acids, and fatty acid metal salts.

5. A method for producing a two-component developer according to claim 1 or 2, The manufacturing method is A step of mixing the toner particles with an external additive other than the inorganic fine particles B to obtain a toner particle mixture. A step of mixing the toner particle mixture with the inorganic fine particles B to obtain toner, and A step of mixing the toner and the magnetic carrier to obtain a two-component developer, A method for producing a two-component developer having the following properties.

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