Magnetic carrier for electrostatic image development

Abstract

To provide a magnetic carrier for electrostatic charge image development that suppresses a decrease in image density due to an excessive increase in the charge amount of a toner in a low-humidity environment and suppresses contamination in an image forming apparatus due to toner scattering caused by a decrease in the charge amount of the toner in a high-humidity environment.SOLUTION: The magnetic core particle is a particle having a silicone resin on the surface thereof, and the coating resin layer is a layer containing a vinyl resin as a binder resin and containing a silica particle, the M1 and the M2 satisfy the following formula (1), where M1 is a mass of the toner after the toner is stored in a first environmental condition at a temperature of 30 °C and a humidity of 80% for 5 hours, and M2 is a mass of the toner after the toner is stored in a second environmental condition at a temperature of 23 °C and a humidity of 5% for 5 hours. 0.055 ≤ (M1-M2) / M1 * 100 ≤ 0.200 Formula (1) SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a magnetic carrier for electrostatic development used in an image forming method for visualizing an electrostatic image using an electrophotographic system. [Background technology]

[0002] Conventionally, electrophotographic image forming 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 the electrostatic latent image. In this development, a two-component development method is widely used in which carrier particles called magnetic carriers are mixed with the toner, and the toner is frictionally charged to impart an appropriate amount of positive or negative charge to the toner, and the charge is used as a driving force for development.

[0003] In the two-component development method, the magnetic carrier can be given functions such as stirring, transporting, and charging the developer, so the division of functions between the carrier and the toner is clear, which has the advantage of good controllability of developer performance.Here, the magnetic carrier often has a magnetic core that is magnetized to achieve transportability, and a coating resin that coats the magnetic core to provide the ability to charge the toner.

[0004] Because the density of an image created using electrophotography varies depending on the charge amount of the toner, electrophotographic image forming devices are typically equipped with a mechanism for adjusting development conditions to maintain a constant final image density. However, when the toner charge amount fluctuates beyond the adjustable range due to factors such as fluctuations in temperature and humidity in the environment in which the device is installed, problems such as a decrease in image density due to excessive charge or, conversely, contamination inside the device due to toner scattering due to insufficient charge can occur. These problems tend to become more pronounced in image forming device configurations designed to meet the needs for higher image quality and faster speeds, creating a demand for the development of a developer that improves both of these properties.

[0005] In the two-component development method, the charging characteristics of the toner can be changed by the structure of the magnetic carrier described above, and therefore magnetic carriers with specially designed coating resin layer structures are known.

[0006] Patent Document 1 proposes a carrier for an electrophotographic dry developer, characterized in that the surface of a core material has a coating layer formed by curing an epoxy resin containing finely powdered silica particles with a polyamide resin.

[0007] Patent Document 2 describes a resin layer that includes magnetic particles and silica particles that cover the magnetic particles and have an average particle size of 50 nm to 200 nm. When the ratio of Si elements in a region that is 0.1 μm to 0.2 μm away from the surface of the resin layer in the direction toward the inside is defined as Si1, and the ratio of Si elements in a region that is 0 μm to 0.1 μm away from the surface of the magnetic particles in the direction toward the surface of the resin layer is defined as Si2, Formula 1-1: 0.005≦Si1≦2 Formula 2-1:1≦Si1 / Si2≦1000 There has been proposed a carrier for developing electrostatic images that satisfies the above requirements. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Application Publication No. 117555 / 1983 [Patent Document 2] Japanese Patent Publication No. 2022-181065 Summary of the Invention [Problem to be solved by the invention]

[0009] In order to solve the above problems, the present invention aims to provide a magnetic carrier for electrostatic development that suppresses a decrease in image density due to an excessive increase in the amount of charge of toner in a low-humidity environment, and that suppresses contamination inside an image forming apparatus due to toner scattering that occurs due to a decrease in the amount of charge of toner in a high-humidity environment. [Means for solving the problem]

[0010] In order to solve the above problems, the present invention provides: A magnetic carrier for electrostatic development, comprising magnetic core particles and a coating resin layer that coats the surfaces of the magnetic core particles, the magnetic core particles are particles having a silicone resin on the surface thereof, the coating resin layer is a layer containing a vinyl resin as a binder resin and silica particles, The magnetic carrier for electrostatic charge development is characterized in that, when the mass of the magnetic carrier for electrostatic charge development after being kept in a first environment at a temperature of 30°C and a relative humidity of 80% for 5 hours is defined as M1, and the mass of the magnetic carrier for electrostatic charge development after being kept in the first environment for 5 hours is defined as M2 after being kept in a second environment at a temperature of 23°C and a relative humidity of 5% for 5 hours, M1 and M2 satisfy the following formula (1): 0.055≦(M1-M2) / M1×100≦0.200 Formula (1) [Effects of the Invention]

[0011] This can prevent a decrease in image density due to an excessive increase in the amount of charge on toner in a low-humidity environment, and can prevent contamination inside the image forming apparatus due to toner scattering due to a decrease in the amount of charge on toner in a high-humidity environment. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a secondary electron image obtained by observing the surface of a carrier used in the present invention. [Figure 2] FIG. 1 is a schematic diagram of a surface treatment device used in the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0013] [One embodiment] One embodiment is directed to a magnetic carrier for electrostatic development. The magnetic carrier for electrostatic development of the present invention is A magnetic carrier for electrostatic development, comprising magnetic core particles and a coating resin layer that coats the surfaces of the magnetic core particles, the magnetic core particles are particles having a silicone resin on the surface thereof, the coating resin layer is a layer containing a vinyl resin as a binder resin and silica particles, When the mass of the magnetic carrier for electrostatic development after being kept in a first environment at a temperature of 30°C and a relative humidity of 80% for 5 hours is defined as M1, and the mass of the magnetic carrier for electrostatic development after being kept in the first environment for 5 hours after being kept in a second environment at a temperature of 23°C and a relative humidity of 5% for 5 hours is defined as M2, M1 and M2 satisfy the following formula (1): 0.055≦(M1-M2) / M1×100≦0.200 Formula (1) The embodiments of the present invention will be described in more detail below.

[0014] The magnetic carrier for electrostatic development (hereinafter also referred to as carrier) according to the present invention, having the above-mentioned configuration, can suppress the decrease in image density that occurs due to an excessive increase in the charge amount of toner in a low-humidity environment, and can suppress contamination inside an image forming apparatus due to toner scattering that occurs due to a decrease in the charge amount of toner in a high-humidity environment. Although the mechanism by which this occurs is unclear, it is presumed to be as follows.

[0015] In a low-humidity environment, when images with a low image ratio are output continuously, the charge amount of the toner increases excessively, the amount of toner that can fly decreases relative to the size of the development contrast formed on the image carrier, and the image density when a toner image is formed may decrease. The carrier used in the present invention contains silica particles in the coating resin layer, and since silica particles generally have a higher negative chargeability than the coating resin of the carrier, the difference in the charge series with the toner surface is small, and this has the effect of preventing the charge amount of the toner from becoming excessively large.

[0016] Furthermore, since the carrier satisfies the mass loss rate of 0.055% or more in formula (1), the amount of moisture loss in a low humidity environment is greater than that in a high humidity environment, and the carrier surface is more negative in a low humidity environment, which is thought to have a significant effect of preventing the toner charge from becoming excessively large.In the present invention, M1 and M2 can be confirmed, for example, using a thermogravimetric analyzer.

[0017] Furthermore, in a high-humidity environment, when images with a high image ratio are continuously output, the proportion of toner with a low charge amount increases, and the adhesive force between the carrier and the toner decreases, which can cause the toner to scatter from the developing machine and contaminate the inside of the image forming device. This phenomenon is known to be more pronounced in carriers containing highly negative silica particles in the coating resin layer. However, since the carrier according to the present invention satisfies the mass loss rate of formula (1) of 0.055% or more, the increase in moisture in a high-humidity environment is greater than in a high-humidity environment compared to a low-humidity environment, and the negative nature of the carrier surface in a high-humidity environment is considered to be relatively low. This is thought to be because the carrier has a higher ability to impart charge to the toner even in a high-humidity environment compared to conventional carriers containing silica particles.

[0018] Furthermore, the magnetic carrier for electrostatic charge development of the present invention has magnetic core particles having a silicone resin on the surface. That is, the surfaces of the magnetic core particles of the carrier of the present invention are coated with a silicone resin. Silicone resin has a higher affinity with silica particles than magnetic materials, which increases the probability of silica particles being present near the silicone resin that coats the core during carrier production. This reduces the probability of silica particles coming into contact with the magnetic portion of the magnetic core particles, thereby suppressing the decrease in the toner charge due to charge leakage from the toner through the magnetic portion, which is a material with lower resistance than the resin component. As mentioned above, the carrier used in the present invention has a high moisture content in high-humidity environments, but its structure allows for improved charge stability in high-humidity environments by reducing the frequency of contact between silica particles and magnetic materials.

[0019] Furthermore, the magnetic carrier for electrostatic development of the present invention has a coating resin layer containing a vinyl resin as a binder resin and silica particles. Compared to other resins, the vinyl resin has a higher ability to impart charge to the toner and serves to ensure a sufficient charge amount of the toner in a high-humidity environment. In the present invention, the type of chemical substance can be confirmed, for example, by nuclear magnetic resonance (NMR).

[0020] For the above reasons, it is presumed that the carrier of the present invention can suppress the decrease in image density caused by an excessive increase in the charge amount of toner in a low-humidity environment, and can also suppress contamination inside an image forming device caused by toner scattering caused by a decrease in the charge amount of toner in a high-humidity environment.

[0021] Furthermore, the carrier according to the present invention satisfies the requirement that the mass loss rate of formula (1) is 0.200% or less. If the mass loss rate of formula (1) is greater than 0.200%, the moisture content of the carrier is considered to be too high in a high humidity environment, and the effect of suppressing contamination inside the image forming apparatus due to toner scattering cannot be sufficiently achieved.

[0022] Furthermore, in the magnetic carrier for electrostatic development of the present invention, the ratio of the area of ​​the exposed silica particles to the surface area of ​​the coating resin layer on the surface of the magnetic carrier for electrostatic development is preferably 10% or more. This increases the probability that the highly negative silica particles will come into contact with the toner, making the carrier surface more negative in a low-humidity environment and enhancing the effect of preventing excessive toner charge. This further suppresses the decrease in image density associated with excessive toner charge in a low-humidity environment. A silica particle exposure ratio of 13% or more is more preferable because it further increases the negative surface of the carrier.

[0023] The magnetic carrier for electrostatic charge development of the present invention is preferably formed so that 80% or more of the surface of the magnetic material is covered. If the surface of the magnetic material is sufficiently covered, the effect of improving the charge amount stability in a high-humidity environment is more easily achieved. This is thought to be because if the surface of the magnetic material is sufficiently covered, the proportion of exposed parts of the magnetic material, which is a material with lower resistance compared to the resin component, is reduced. If the surface of the magnetic material is covered by 90% or more, the above effect is more significantly achieved, making this a more preferred form.

[0024] The magnetic carrier for electrostatic development of the present invention has a magnetization of 40 (Am) under a magnetic field of 1000 / 4π (kA / m). 2 / kg) or more 80(Am 2 / kg) or less. When the magnetization strength of the carrier is within the above range, the magnetic binding force to the developing sleeve is appropriate, so that carrier adhesion can be more effectively suppressed. In addition, the stress applied to the toner in the magnetic brush can be reduced, so that toner deterioration and adhesion to other components can be effectively suppressed.

[0025] The magnetic carrier for electrostatic development of the present invention preferably has a volume average particle size (D50) of 20 μm or more and 80 μm or less from the viewpoints of the ability to impart charge to the toner, suppressing carrier adhesion to the image area, and achieving high image quality, and more preferably 20 μm or more and 60 μm or less.

[0026] <Magnetic core particles> The magnetic core particles of the present invention are not particularly limited as long as they satisfy the specified range of the present invention, and can use known magnetic particles used as the core material of carriers.Specifically, they can be magnetic particles whose surface is coated with silicone resin, or magnetic particles having pores and a structure in which silicone resin is distributed inside and on the surface.As the magnetic material, any commonly known material can be used without any particular limitation, and for example, magnetic metals such as iron, nickel, cobalt, or oxides of magnetic metals, or oxides of magnetic metals with metal elements such as manganese, magnesium, strontium, copper, zinc, etc. can be used.

[0027] In an embodiment of the present invention, the magnetic core particles are preferably those in which a silicone resin is distributed inside and on the surface of metal oxide particles such as ferrite or magnetite having voids.Since silicone resin has low affinity with magnetic materials, the adhesive strength at the interface with the magnetic material is weak, and this may cause peeling of the resin layer when used for a long period of time, but if the silicone resin is filled into the inside of the magnetic material particles, peeling of the resin layer is thought to be less likely to occur.

[0028] The silicone resin used to coat the magnetic material is a compound having a polysiloxane structure. For example, a cured silicone resin such as a methyl silicone resin or a methyl phenyl silicone resin, or a resin such as a silicone-modified acrylic resin, polyester resin, or epoxy resin can be used. From the viewpoints of solvent resistance and mechanical stability in forming the coating resin layer described below, it is preferable to use a cured methyl silicone resin.

[0029] When coating the magnetic material with a silicone resin, a commonly used curing catalyst may be used as needed. For example, tin compounds, titanium compounds, zinc compounds, aluminum compounds, iron compounds, cobalt compounds, manganese compounds, etc. can be used. Among these, tin compounds and titanium compounds are particularly suitable as catalysts because they have a significant effect of improving the hardness of the silicone resin.

[0030] A method for coating a magnetic material with a silicone resin includes diluting the resin component in a solvent and adding magnetic particles to the diluted solution. The solvent used here can be any solvent capable of dissolving the resin component. That is, organic solvents such as toluene, xylene, cellosolve butyl acetate, methyl ethyl ketone, methyl isobutyl ketone, and methanol can be used alone or in combination as needed. Methods for distributing the resin component diluted with a solvent on the magnetic particle surface include coating methods such as immersion, spraying, brushing, fluidized bed coating, and kneading, in which the resin component is distributed on the magnetic material surface, and then the solvent is volatilized. Depending on the curing characteristics of the silicone resin, the solvent is volatilized, and then the temperature is raised to cause a curing reaction, thereby forming a resin layer.

[0031] The silicone resin distributed on the magnetic material surface preferably has a thickness of 30 nm to 300 nm. When the silicone resin is 30 nm or more, it is believed that the surface of the magnetic material is sufficiently covered, reducing the frequency of contact between the silica particles and the magnetic material, making it easier to achieve the effect of improving the charge stability in high-humidity environments. Furthermore, when the thickness is 300 nm or less, it is believed that the carrier resistance can be prevented from becoming excessively high, making it easier to achieve the effect of preventing the toner charge from becoming excessively high in low-humidity environments.

[0032] In the magnetic carrier for electrostatic development of the present invention, the magnetic core particles preferably have a structure in which the pores of the magnetic particles are filled with a silicone resin, which makes it possible to further suppress contamination of the inside of an image forming apparatus due to toner scattering caused by a decrease in the toner charge amount in a high-humidity environment over a long period of use.

[0033] One method for filling the interior of porous magnetic particles with a resin component is to dilute the resin component in a solvent and then add the porous magnetic particles to the diluted solution. The solvent used here can be any solvent capable of dissolving each resin component. In other words, organic solvents such as toluene, xylene, cellosolve butyl acetate, methyl ethyl ketone, methyl isobutyl ketone, and methanol can be used alone or in combination as needed. Methods for adding the solvent-diluted resin component to the interior of the magnetic particles include impregnating the resin component using a coating method such as immersion, spraying, brushing, fluidized bed coating, and kneading, followed by volatilizing the solvent.

[0034] In this case, the solution may be decompressed depending on the viscosity characteristics of the resin to promote filling of the resin component into the pores. Depending on the curing characteristics of the silicone resin, the solvent is volatilized, and then the temperature is raised to cause a curing reaction to form a resin layer. If necessary, the amount of silicone resin added may be adjusted to simultaneously distribute the silicone resin inside and on the surface of the magnetic particles, or the inside of the particles may be filled with the silicone resin, and then the magnetic material may be coated with the silicone resin in the same manner as described above.

[0035] The magnetic carrier for electrostatic development of the present invention preferably has a silicone resin coverage of 60% or more on the surface of the magnetic core particles, as measured by the method described below. By doing so, the greater the proportion of the magnetic material covered with silicone resin, the less frequently the silica particles come into contact with the magnetic material, making it possible to maintain a high charge level, particularly in high-humidity environments. This further reduces contamination inside the image-forming device due to toner scattering caused by a decrease in toner charge level in high-humidity environments. A silicone resin coverage of 70% or more is more preferred.

[0036] When the abundance ratio of silicon atoms on the surface of the magnetic core particle is Si_atm (atomic %) and the total abundance ratio of iron, manganese, magnesium, strontium, copper, zinc, nickel, and cobalt atoms is M_atm (atomic %), it is preferable that Si_atm and M_atm satisfy the following formula (2). M_atm / Si_atm<0.4 Equation (2)

[0037] This increases the proportion of the magnetic material covered with silicone resin, reducing the frequency of contact between the silica particles and the magnetic material, thereby maintaining a high charge amount, especially in high-humidity environments, and further suppressing contamination inside the image forming apparatus due to toner scattering caused by a decrease in toner charge amount in high-humidity environments.

[0038] The magnetic core particles preferably have a volume average particle size (D50) of 20 μm or more and 80 μm or less in order to be uniformly coated with the coating resin, prevent magnetic carrier adhesion, and ensure an appropriate density of the developer magnetic brush to obtain high-quality images.

[0039] The resistivity of the magnetic core particles is 1.0 x 10 at an electric field strength of 1000 (V / cm). 5 (Ω cm) or more 1.0×10 14 (Ω·cm) or less is preferable because good developability can be obtained.

[0040] <Coating resin layer> The carrier according to the present invention has a coating resin layer that coats the surface of the magnetic core particles. The coating resin layer uses a coating resin made of a vinyl resin as a binder resin and contains silica particles.

[0041] The average thickness of the coating resin layer is preferably 100 nm or more, which can reduce the frequency of contact between the magnetic material and the silica particles and can easily ensure the charge amount of the toner, especially in a high-humidity environment. Furthermore, if the thickness is greater than 3000 nm, the charge is likely to increase in a low-humidity environment, so the coating resin layer is preferably 3000 nm or less. If the thickness is 1500 nm or less, the charge increase in a low-humidity environment can be more effectively suppressed, which is more preferable.

[0042] The method for forming a coating resin layer on the surface of magnetic core particles is not particularly limited, and known methods can be used. For example, there is a dipping method in which the magnetic core particles and coating resin solution are stirred while volatilizing the solvent, and the coating resin is coated on the surface of the magnetic core. Specific examples include a universal mixer (manufactured by Fuji Paudal Co., Ltd.) and a Nauta Mixer (manufactured by Hosokawa Micron Corporation). Another method involves spraying the coating resin solution from a spray nozzle while forming a fluidized bed, thereby coating the surface of the magnetic core particles with the coating resin.

[0043] Specific examples include Spiracoater (manufactured by Okada Seiko Co., Ltd.) and Spiraflow (manufactured by Freund Corporation). There is also a dry coating method in which the magnetic core particles are coated with a coating resin in particle form. Specific examples include processing methods using devices such as Hybridizer (manufactured by Nara Machinery Works Co., Ltd.), Mechanofusion (manufactured by Hosokawa Micron Corporation), Hyflex Gral (manufactured by Fukae Powtec), and Theta Composer (manufactured by Tokuju Kogyosho Co., Ltd.).

[0044] The coating resin layer may also contain resin components other than the binder resin and various additives other than silica particles, provided that the effects of the present invention are not impaired. Examples of such additives include resin particles such as acrylic resin, phenolic resin, and melamine resin as charge control agents, and carbon black and metal particles as resistance control agents.

[0045] <Coating resin> The coating resin is made of a vinyl resin and serves as a binder resin for the coating resin layer. The coating resin is not particularly limited as long as it is a polymer of a vinyl monomer, and known resins can be used. Examples of the monomers that can be used include known monomers such as (meth)acrylic acid and esters, olefins, aromatic vinyl compounds such as styrene, and organic acids and esters having a vinyl group such as vinyl acetate. These monomers can be used as homopolymers or as copolymers by combining multiple monomers. When used as a copolymer, the form of polymerization can be selected as needed, such as random polymerization, block polymerization, or graft polymerization.

[0046] When the mass of the vinyl resin after being held in the first environment for 5 hours is defined as M5, and the mass of the vinyl resin after being held in the first environment for 5 hours is defined as M6, it is preferable that M5 and M6 satisfy the following formula (4): 0≦(M5-M6) / M5×100≦0.60 Formula (4)

[0047] By doing so, the moisture content in a high-humidity environment is reduced, making it easier to maintain a high level of charge imparting ability to the toner in a high-humidity environment. This also makes it possible to further suppress contamination inside the image forming apparatus due to toner scattering caused by a decrease in the toner charge amount in a high-humidity environment. In the present invention, M5 and M6 can be confirmed, for example, using a thermogravimetric analyzer.

[0048] In the magnetic carrier for electrostatic development of the present invention, the vinyl resin preferably contains a unit derived from a (meth)acrylic acid ester monomer, and more preferably is a copolymer containing at least one type of monomer containing a (meth)acrylic acid ester having a cyclic hydrocarbon group in its molecular structure. Because of its properties of low moisture absorption in a high-humidity environment and ability to maintain high charge-imparting ability to the toner, it is preferable to use a polymer containing at least one type of (meth)acrylic acid ester as a monomer.

[0049] Furthermore, it is more preferable that at least one of the monomers used is a (meth)acrylic acid ester having an alicyclic hydrocarbon in its molecular structure, since this more effectively reduces moisture absorption in a high-humidity environment. This makes it possible to further suppress contamination inside the image forming apparatus due to toner scattering caused by a decrease in toner charge in a high-humidity environment.

[0050] <Silica particles> The carrier of the present invention contains silica particles in the coating resin layer. The silica particles can be selected from known particles as long as the effects of the present invention are not impaired, and examples thereof include combustion silica particles, deflagration silica particles, sol-gel silica particles, precipitation silica particles, and colloidal silica particles.

[0051] In the magnetic carrier for electrostatic development of the present invention, when the mass of the silica particles after being held in the first environment for 5 hours is M3 and the mass of the silica particles after being held in the first environment for 5 hours is M4, it is preferable that M3 and M4 satisfy the following formula (3): 3.00≦(M3-M4) / M3×100≦10.0 Formula (3)

[0052] By doing so, the effect of suppressing the decrease in image density due to an excessive increase in the amount of charge of the toner in a low-humidity environment is enhanced. Furthermore, the decrease in image density due to an excessive increase in the amount of charge of the toner in a low-humidity environment can be further suppressed. In the present invention, M3 and M4 can be confirmed, for example, using a thermogravimetric analyzer.

[0053] Although the detailed mechanism of this is not clear, it is presumed that the amount of moisture loss in a low-humidity environment is greater than that in a high-humidity environment, which induces a more negative state on the carrier surface in a low-humidity environment, making it easier to achieve the effect of preventing the toner charge from becoming excessively large. In order to achieve the above effect more effectively, it is more preferable that the mass reduction rate is 4% or more. Furthermore, the mass loss rate is preferably 10% or less, since this makes it easier to ensure a sufficient charge amount of the toner in a high humidity environment, and more preferably 7% or less.

[0054] The magnetic carrier for electrostatic development of the present invention is silica particles (wet silica particles) produced by a wet method such as a sol-gel method or a precipitation method. This makes it easier to reduce the amount of moisture lost in a low-humidity environment compared to a high-humidity environment. This also makes it possible to further suppress the decrease in image density caused by an excessive increase in the toner charge amount in a low-humidity environment.

[0055] If the silica particles are subjected to a hydrophobic treatment on their surfaces as necessary, this is preferred because it is more likely to exhibit the effect of suppressing excessive toner charge in a low-humidity environment. When the silica particles are subjected to a hydrophobic treatment on their surfaces, they are more likely to have a structure in which the silica particles are exposed on the surface of the coating resin layer, which is thought to improve the frequency of contact between the toner and the silica particles when the carrier is mixed with the toner and used as a developer.

[0056] Any known means can be used for the surface treatment, and can be selected from silane coupling agents having alkyl groups such as methyl groups, ethyl groups, and propyl groups, titanate coupling agents, and aluminate coupling agents. It is preferable to use coupling agents such as various titanium coupling agents and silane coupling agents; fatty acids and metal salts thereof; silicone oil; or a combination thereof.

[0057] Examples of titanium coupling agents include tetrabutyl titanate, tetraoctyl titanate, isopropyl triisostearoyl titanate, isopropyl tridecylbenzenesulfonyl titanate, and bis(dioctyl pyrophosphate)oxyacetate titanate.

[0058] Furthermore, examples of silane coupling agents include γ-(2-aminoethyl)aminopropyltrimethoxysilane, γ-(2-aminoethyl)aminopropylmethyldimethoxysilane, γ-methacryloxypropyltrimethoxysilane, N-β-(N-vinylbenzylaminoethyl)γ-aminopropyltrimethoxysilane hydrochloride, hexamethyldisilazane, methyltrimethoxysilane, butyltrimethoxysilane, isobutyltrimethoxysilane, hexyltrimethoxysilane, octyltrimethoxysilane, decyltrimethoxysilane, dodecyltrimethoxysilane, phenyltrimethoxysilane, o-methylphenyltrimethoxysilane, and p-methylphenyltrimethoxysilane.

[0059] Examples of fatty acids include long-chain fatty acids such as undecylic acid, lauric acid, tridecylic acid, dodecylic acid, myristic acid, palmitic acid, pentadecylic acid, stearic acid, heptadecylic acid, arachidic acid, montanic acid, oleic acid, linoleic acid, and arachidonic acid. Examples of metals in these fatty acid metal salts include zinc, iron, magnesium, aluminum, calcium, sodium, and lithium. Examples of silicone oils include dimethyl silicone oil, methylphenyl silicone oil, and amino-modified silicone oil.

[0060] Among these, a silane coupling agent can be particularly preferably used, and since the effect of preventing the charge amount of the toner from becoming excessively high in a low-humidity environment is easily achieved, it is particularly preferred to use the same surface treatment agent as that used for the surface treatment of the silica particle external additive contained in the toner.

[0061] It is preferable that the absolute value of the difference in work function between the silica particles and the silica particle external additive contained in the toner described later is 0.20 eV or less, since this makes it easier to prevent the toner from becoming excessively charged in a low-humidity environment. The absolute value of the difference in work function is more preferably 0.10 eV or less.

[0062] The magnetic carrier for electrostatic charge development of the present invention has a silica particle surface on which the number of silanol groups per unit surface area of ​​the silica particle is 1.0 / nm 2 More than 2.0 pieces / nm 2 By doing so, the effect of ensuring a high toner charge amount in a high humidity environment is enhanced.

[0063] Although the detailed mechanism of this is unclear, it is presumed that if the number of highly polar silanol groups on the silica particle surface is small, the affinity with the silicone resin on the magnetic core surface increases, and the probability that the silica particles will be distributed near the exposed magnetic body during the formation of the coating resin layer decreases, thereby reducing the frequency of contact between the silica particles and the magnetic body. One method for reducing the number of silanol groups on the silica particle surface is to perform surface treatment using the various coupling agents mentioned above. The number of silanol groups per unit surface area of ​​silica particles is 1.0 / nm 2 If the amount is more than this, it is possible to reduce the inclusion of by-products derived from the surface treatment agent, which is preferable.

[0064] In the magnetic carrier for electrostatic development of the present invention, the volume average particle diameter of the silica particles is preferably 50 nm or more and 250 nm or less. When the volume average particle diameter of the silica particles is 50 nm or more, they are more likely to be exposed from the surface of the coating resin layer, increasing the frequency of contact with the toner, thereby enhancing the effect of preventing excessive charging in low-humidity environments. Furthermore, when the volume average particle diameter is 250 nm or less, the frequency of contact with the magnetic material can be reduced, ensuring sufficient charge even in high-humidity environments. A volume average particle diameter of 200 nm or less is more preferable because it further enhances the effect of improving charge. Furthermore, a volume average particle diameter of 50 nm or more and 250 nm or less can further suppress the decrease in image density associated with an increase in the excessive charge amount of the toner in low-humidity environments.

[0065] <Toner> The carrier of the present invention can be used in combination with a toner produced by a known method without any particular limitation. Generally, the carrier contains a binder resin for the toner base as the main component, and optionally contains a release agent, a colorant, a dispersing aid, and inorganic particles. In particular, a negatively charged toner having a structure in which one or more types of inorganic fine particles, including silica particles, are attached to the surface of toner base particles mainly composed of a binder resin is preferably used, since this is more likely to have the effect of suppressing excessive charge increase of the toner in a low-humidity environment.

[0066] <Binder resin for toner base> The following polymers can be used as the binder resin for the toner matrix. Examples include homopolymers of styrene and its substituted derivatives, such as polystyrene, poly-p-chlorostyrene, and polyvinyltoluene; styrene-based copolymers, such as styrene-p-chlorostyrene copolymer, styrene-vinyltoluene copolymer, styrene-vinylnaphthalene copolymer, styrene-acrylic acid ester copolymer, and styrene-methacrylic acid ester copolymer; styrene-based copolymer resins; polyester resins; hybrid resins, such as mixtures of polyester resin and vinyl resin, or hybrid resins in which both are partially reacted; polyvinyl chloride, phenolic resins, naturally modified phenolic resins, naturally resin-modified maleic acid resins, acrylic resins, methacrylic resins, polyvinyl acetate, silicone resins, polyester resins, polyurethanes, polyamide resins, furan resins, epoxy resins, xylene resins, polyethylene resins, and polypropylene resins. Among these, resins containing polyester resin as the main component are preferred from the viewpoint of low-temperature fixability.

[0067] Monomers used in the polyester unit of the polyester resin include polyhydric alcohols (divalent or trivalent or higher alcohols), polycarboxylic acids (divalent or trivalent or higher carboxylic acids), their acid anhydrides, or their lower alkyl esters. To create a branched polymer that exhibits "strain hardening," partial crosslinking within the molecule of the amorphous resin is effective, and for this purpose, it is preferable to use a polyfunctional compound with a valence of three or more. Therefore, it is preferable to include a trivalent or higher carboxylic acid, its acid anhydride, or its lower alkyl ester, and / or a trivalent or higher alcohol as the raw material monomer for the polyester unit.

[0068] As the polyhydric alcohol monomer used in the polyester unit of the polyester resin, the following polyhydric alcohol monomers can be used. The dihydric alcohol component includes 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 the following formula (A) and their derivatives. [ka] (In formula (A), R is an ethylene or propylene group, x and y are each an integer of 0 or more, and the average value of x+y is 0 or more and 10 or less.) Diols represented by the following formula (B) are preferably used. [ka]

[0069] Examples of trihydric or higher alcohol components include sorbitol, 1,2,3,6-hexanetetrol, 1,4-sorbitan, pentaerythritol, dipentaerythritol, tripentaerythritol, 1,2,4-butanetriol, 1,2,5-pentanetriol, glycerol, 2-methylpropanetriol, 2-methyl-1,2,4-butanetriol, trimethylolethane, trimethylolpropane, and 1,3,5-trihydroxymethylbenzene. Among these, glycerol, trimethylolpropane, and pentaerythritol are preferred. These dihydric and trihydric or higher alcohols can be used alone or in combination.

[0070] As the polycarboxylic acid monomer used in the polyester unit of the polyester resin, the following polycarboxylic acid monomers can be used. Examples of dicarboxylic acid components include maleic acid, fumaric acid, citraconic acid, itaconic acid, glutaconic acid, phthalic acid, isophthalic acid, terephthalic acid, succinic acid, adipic acid, sebacic acid, azelaic acid, malonic acid, n-dodecenylsuccinic acid, isododecenylsuccinic acid, n-dodecylsuccinic acid, isododecylsuccinic acid, n-octenylsuccinic acid, n-octylsuccinic acid, 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.

[0071] Examples of trivalent or higher carboxylic acids, their acid anhydrides, or their lower alkyl esters include 1,2,4-benzenetricarboxylic acid, 2,5,7-naphthalenetricarboxylic acid, 1,2,4-naphthalenetricarboxylic acid, 1,2,4-butanetricarboxylic acid, 1,2,5-hexanetricarboxylic acid, 1,3-dicarboxyl-2-methyl-2-methylenecarboxypropane, 1,2,4-cyclohexanetricarboxylic acid, tetra(methylenecarboxyl)methane, 1,2,7,8-octanetetracarboxylic acid, pyromellitic acid, empol trimer acid, and their acid anhydrides or lower alkyl esters. Among these, 1,2,4-benzenetricarboxylic acid, i.e., trimellitic acid or its derivatives, is particularly preferred due to its low cost and easy reaction control. These divalent carboxylic acids and trivalent or higher carboxylic acids can be used alone or in combination.

[0072] The method for producing the polyester unit of the present invention is not particularly limited, and known methods can be used. For example, the aforementioned alcohol monomer and carboxylic acid monomer are simultaneously charged and polymerized via an esterification reaction or transesterification reaction and a condensation reaction to produce a polyester resin. The polymerization temperature is not particularly limited, but is preferably in the range of 180°C to 290°C. Polymerization of the polyester unit can be performed using polymerization catalysts such as titanium-based catalysts, tin-based catalysts, zinc acetate, antimony trioxide, and germanium dioxide. In particular, the binder resin for toner base of the present invention preferably uses a polyester unit polymerized using a tin-based catalyst.

[0073] In addition, it is preferable from the viewpoint of fogging that the acid value of the polyester resin is 5 mgKOH / g or more and 20 mgKOH / g or less, and the hydroxyl value is 20 mgKOH / g or more and 70 mgKOH / g or less, since this reduces the amount of moisture adsorption in a high-temperature, high-humidity environment and keeps the non-electrostatic adhesion force low.

[0074] The binder resin for the toner base may be a mixture of a low molecular weight resin and a high molecular weight resin. The ratio of the high molecular weight resin to the low molecular weight resin is preferably 40 / 60 or more and 85 / 15 or less by mass from the viewpoint of low temperature fixability and hot offset resistance.

[0075] <Release agent> The toner may contain a release agent to improve separation from the member during thermal fixing. Examples of the release agent 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 containing fatty acid esters as the main component such as carnauba wax; and partially or completely deoxidized fatty acid esters such as deoxidized carnauba wax.

[0076] Furthermore, saturated straight-chain fatty acids such as palmitic acid, stearic acid, and montanic acid; unsaturated fatty acids such as brassidic acid, eleostearic acid, and valinaric acid; saturated alcohols such as stearyl alcohol, aralkyl alcohol, behenyl alcohol, carnaubyl alcohol, ceryl alcohol, and melissyl alcohol; polyhydric alcohols such as sorbitol; esters of fatty acids such as palmitic acid, stearic acid, behenic acid, and montanic acid 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; methylene bisstearic acid amide, ethylene biscapric acid amide, ethylene bislauric acid amide, hexamethylene bis Examples include saturated fatty acid bisamides such as stearic acid amide; unsaturated fatty acid amides such as ethylene bisoleic acid amide, hexamethylene bisoleic acid amide, N,N'-dioleyl adipamide, and N,N'-dioleyl sebacic acid amide; aromatic bisamides such as m-xylene bisstearic acid amide and N,N'-distearyl isophthalic acid amide; fatty metal salts (commonly known as metal soaps) such as calcium stearate, calcium laurate, zinc stearate, and magnesium stearate; waxes obtained by grafting aliphatic hydrocarbon waxes with vinyl monomers such as styrene and acrylic acid; partial esters of fatty acids and polyhydric alcohols such as behenic acid monoglyceride; and methyl ester compounds having hydroxyl groups obtained by hydrogenating vegetable oils and fats.

[0077] 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 property, and in the present invention, hydrocarbon waxes are more preferred from the viewpoint of further improving hot offset resistance. In the present invention, the wax is preferably used in an amount of 3 parts by mass or more and 8 parts by mass or less per 100 parts by mass of the binder resin for the toner base.

[0078] Furthermore, in an endothermic curve during temperature rise measured with a differential scanning calorimetry (DSC) device, the peak temperature of the maximum endothermic peak of the wax is preferably 45° C. or higher and 140° C. or lower. If the peak temperature of the maximum endothermic peak of the wax is within the above range, it is preferable because it is possible to achieve both storage stability and hot offset resistance of the toner.

[0079] <Coloring agent> The toner particles of the present invention may contain a colorant. Examples of the colorant include the following. Examples of black colorants include carbon black, and also include those toned to black using a yellow colorant, a magenta colorant, and a cyan colorant. As the colorant, a pigment may be used alone, but it is more preferable to use a dye and a pigment in combination to improve the clarity from the viewpoint of the image quality of a full-color image.

[0080] Pigments for magenta toner include 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, Examples include 60, 63, 64, 68, 81:1, 83, 87, 88, 89, 90, 112, 114, 122, 123, 146, 147, 150, 163, 184, 202, 206, 207, 209, 238, 269, and 282, as well as CI Pigment Violet 19 and CI Bat Red 1, 2, 10, 13, 15, 23, 29, and 35.

[0081] Examples of dyes for magenta toners include solvent dyes such as CI Solvent Red 1, 3, 8, 23, 24, 25, 27, 30, 49, 81, 82, 83, 84, 100, 109, and 121, CI Disperse Red 9, CI Solvent Violet 8, 13, 14, 21, and 27, and CI Disperse Violet 1; and basic dyes such as CI Basic Red 1, 2, 9, 12, 13, 14, 15, 17, 18, 22, 23, 24, 27, 29, 32, 34, 35, 36, 37, 38, 39, and 40, and CI Basic Violet 1, 3, 7, 10, 14, 15, 21, 25, 26, 27, and 28.

[0082] Examples of pigments for cyan toner include CI Pigment Blue 2, 3, 15:2, 15:3, 15:4, 16, and 17, CI Vat Blue 6, CI Acid Blue 45, and copper phthalocyanine pigments in which 1 to 5 phthalimidomethyl groups are substituted on the phthalocyanine skeleton. An example of a dye for cyan toner is CI Solvent Blue 70.

[0083] Examples of pigments for yellow toner include CI Pigment Yellow 1, 2, 3, 4, 5, 6, 7, 10, 11, 12, 13, 14, 15, 16, 17, 23, 62, 65, 73, 74, 83, 93, 94, 95, 97, 109, 110, 111, 120, 127, 128, 129, 147, 151, 154, 155, 168, 174, 175, 176, 180, 181, and 185, and CI Vat Yellow 1, 3, and 20. An example of a dye for yellow toner is CI Solvent Yellow 162.

[0084] These colorants can be used alone or in combination, or in the form of a solid solution. The colorant is selected in consideration of hue angle, chroma, brightness, lightfastness, transparency on an overhead projector, and dispersibility in toner. The content of the colorant is preferably 0.1 parts by mass or more and 30.0 parts by mass or less relative to the total amount of the resin components.

[0085] <Dispersion aid> In order to disperse the release agent in the resin, it is preferable that the toner particles contain a dispersing aid. Known dispersing aids can be used, but when a hydrocarbon wax is contained as the release agent, it is preferable to contain a polymer having a structure in which a vinyl resin component and a hydrocarbon compound are reacted in order to disperse the wax in the resin. Among these, it is preferable to contain a graft polymer in which a vinyl monomer is graft polymerized onto a polyolefin.

[0086] When this polymer is contained, the compatibility between the wax and the resin is promoted, and problems such as poor charging and component contamination due to poor wax dispersion are less likely to occur. The content of the dispersion aid is preferably 1.0 to 15 parts by mass per 100 parts by mass of the binder resin for the toner base. When the content is within this range, the wax is more likely to be dispersed uniformly in the amorphous resin. The polyolefin is not particularly limited as long as it is a polymer or copolymer of an unsaturated hydrocarbon, and various polyolefins can be used. Polyethylene-based and polypropylene-based polyolefins are particularly preferred. A plurality of these may be used.

[0087] Examples of the monomer having a vinyl group include 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, and pn-dodecylstyrene, and other styrene and derivatives thereof.

[0088] Examples of monomers having a vinyl group include amino group-containing α-methylene aliphatic monocarboxylic acid esters such as dimethylaminoethyl methacrylate and diethylaminoethyl methacrylate, and vinyl units containing an N atom such as acrylic acid or methacrylic acid derivatives such as acrylonitrile, methacrylonitrile, and acrylamide.

[0089] Examples of the monomer having a vinyl group include unsaturated dibasic acids such as maleic acid, citraconic acid, itaconic acid, alkenylsuccinic acid, fumaric acid, and mesaconic acid; unsaturated dibasic acid anhydrides such as maleic anhydride, citraconic anhydride, itaconic anhydride, and alkenylsuccinic 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, and methyl alkenylsuccinic acid half ester. Examples of vinyl units containing a carboxy group include α,β-unsaturated dibasic acid half esters, methyl fumarate half esters, methyl mesaconic acid half esters, and 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 above α,β-unsaturated acids and lower fatty acids, alkenyl malonic acid, alkenyl glutaric acid, alkenyl adipic acid, acid anhydrides thereof, and monoesters thereof.

[0090] Examples of monomers having a vinyl group include acrylic acid or methacrylic acid esters such as 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, and 2-hydroxypropyl methacrylate, and vinyl units containing a hydroxy group such as 4-(1-hydroxy-1-methylbutyl)styrene and 4-(1-hydroxy-1-methylhexyl)styrene.

[0091] Furthermore, examples of the monomer having a vinyl group include ester units consisting of acrylate 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.

[0092] Examples of monomers having a vinyl group include ester units of methacrylic acid esters such as α-methylene aliphatic monocarboxylic 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. A plurality of these may be used. The dispersing aid can be obtained by a known method such as a reaction between the above-mentioned polymers or a reaction between a monomer of one polymer and a monomer of another polymer.

[0093] <Inorganic fine particles> The toner preferably contains inorganic fine particles, mainly for the purpose of improving fluidity and chargeability, and the particles are preferably attached to the toner surface. In particular, in the present invention, a negatively chargeable toner having silica particles added to the surface is preferred in order to fully exert the effect of suppressing excessive charge in a low-humidity environment.

[0094] As inorganic fine particles serving as spacer particles for improving the releasability between the toner and the magnetic carrier, silica particle external additives having a maximum peak particle size of 80 nm to 200 nm based on the number distribution are preferred, and in order to function as spacer particles while better suppressing separation from the toner, silica particle sizes of 100 nm to 150 nm are more preferred.

[0095] In order to improve the fluidity of the toner, it is preferable to contain inorganic fine particles having a maximum peak particle size of 20 nm or more and 50 nm or less based on the number distribution, and it is also preferable to use them in combination with the silica particle external additive.

[0096] Furthermore, other external additives may be added to the toner particles in order to improve fluidity and transferability. The external additives added to the surface of the toner particles preferably contain inorganic fine particles such as titanium oxide, alumina oxide, strontium titanate, and barium titanate, and a plurality of types may be used in combination.

[0097] The total content of the external additives is preferably 0.3 to 5.0 parts by weight, more preferably 0.8 to 4.0 parts by weight, per 100 parts by weight of toner particles. Among these, the content of silica particles having a number distribution-based maximum peak particle size of 80 to 200 nm is 0.1 to 2.5 parts by weight, more preferably 0.5 to 2.0 parts by weight. Within this range, the effect as spacer particles becomes more pronounced.

[0098] The surfaces of silica particles or inorganic fine particles used as external additives are preferably subjected to a hydrophobic treatment, preferably using a coupling agent such as a titanium coupling agent or a silane coupling agent, a fatty acid or a metal salt thereof, a silicone oil, or a combination thereof.

[0099] The hydrophobic treatment is preferably carried out by adding a hydrophobic treatment agent to the particles to be treated in an amount of 1% by mass or more and 30% by mass or less (more preferably 3% by mass or more and 7% by mass or less) relative to the particles to be treated, thereby coating the particles to be treated.

[0100] The degree of hydrophobicity of the hydrophobized external additive is not particularly limited, but for example, the degree of hydrophobicity after the treatment is preferably 40 or more and 98 or less. The degree of hydrophobicity indicates the wettability of the sample with respect to methanol, and is an index of hydrophobicity.

[0101] <Method of manufacturing toner particles> The method for producing toner particles is not particularly limited, and known methods such as a kneading and pulverizing method, a suspension polymerization method, a solution suspension method, an emulsion aggregation method, and a dispersion polymerization method can be used. Among these, the kneading and pulverizing method is preferred from the viewpoint of controlling the dispersion state of the release agent and the crystalline resin. In other words, the toner particles are preferably pulverized toner particles. The procedure for producing toner using the kneading and pulverizing method will be described below.

[0102] The kneading and pulverization method includes, for example, a raw material mixing step of mixing a release agent, a crystalline polyester and an amorphous polyester as a binder resin for a toner base, and, if necessary, other components such as a colorant and a charge control agent; a step of melting and kneading the mixed raw materials to obtain a resin composition; and a step of pulverizing the obtained resin composition to obtain toner particles.

[0103] In the raw material mixing process, materials constituting the toner particles, such as a binder resin for the toner base, a release agent, and optionally other components such as a colorant and a charge control agent, are weighed out in predetermined amounts, blended, and mixed. Examples of mixing devices include a double cone mixer, a V-type mixer, a drum mixer, a super mixer, a Henschel mixer, a Nauta mixer, and a Mechano Hybrid (manufactured by Nippon Coke and Engineering Co., Ltd.).

[0104] Next, the mixed materials are melt-kneaded to disperse the materials in the binder resin for the toner base. For this melt-kneading process, a batch kneader such as a pressure kneader or a Banbury mixer, or a continuous kneader can be used. Single-screw or twin-screw extruders are the mainstream due to their advantage of continuous production. Examples include a KTK twin-screw extruder (manufactured by Kobe Steel, Ltd.), a TEM twin-screw extruder (manufactured by Toshiba Machine Co., Ltd.), a PCM kneader (manufactured by Ikegai Iron Works), a twin-screw extruder (manufactured by KCK Corporation), a Ko-Kneader (manufactured by Buss Co., Ltd.), and a Kneadex (manufactured by Nippon Coke and Engineering Co., Ltd.). Furthermore, the resin composition obtained by melt-kneading may be rolled using a twin roll or the like and cooled with water or the like in a cooling process.

[0105] The cooled resin composition is then crushed to the desired particle size in a crushing process. In the crushing process, the resin composition is coarsely crushed using a crusher such as a crusher, hammer mill, or feather mill. The resin composition is then finely crushed using a crusher such as a Kryptron System (Kawasaki Heavy Industries), a Super Rotor (Nisshin Engineering), a Turbo Mill (Turbo Kogyo), or an air jet type fine crusher.

[0106] Thereafter, as necessary, the mixture is classified using a classifier or sieve such as an inertial classification type Elbow Jet (manufactured by Nittetsu Mining Co., Ltd.), a centrifugal classification type Turboplex (manufactured by Hosokawa Micron Corporation), a TSP Separator (manufactured by Hosokawa Micron Corporation), or a Faculty (manufactured by Hosokawa Micron Corporation).

[0107] Thereafter, in order to cover the surface of the toner particles with an appropriate amount of release agent, it is preferable to perform a surface treatment of the toner particles by heating from the viewpoint of suppressing blooming. For example, the surface treatment can be performed by using hot air using a surface treatment device shown in FIG.

[0108] The surface treatment using the surface treatment apparatus shown in FIG. 2 will be described below. The mixture supplied by the material supply means 1 is introduced into an introduction pipe 3, which is installed vertically to the material supply means, by compressed gas adjusted by a compressed gas adjustment means 2. The mixture that passes through the introduction pipe 3 is uniformly dispersed by a conical protruding member 4 installed in the center of the material supply means, and is introduced into eight supply pipes 5 that radiate outward, and then into a treatment chamber 6 where heat treatment is carried out.

[0109] At this time, the flow of the mixture supplied to the processing chamber 6 is regulated by a regulating means 9 for regulating the flow of the mixture, which is provided in the processing chamber 6. Therefore, the mixture supplied to the processing chamber is heat-treated while swirling inside the processing chamber 6, and then cooled.

[0110] The hot air for heat-treating the supplied mixture is supplied from hot air supply means 7 through distribution member 12, and is introduced into treatment chamber 6 by spirally swirling it using swirling member 13. The swirling member 13 for swirling the hot air has multiple blades, and the swirling of the hot air can be controlled by changing the number and angle of the blades.

[0111] The hot air supplied into the processing chamber 6 preferably has a temperature of 100°C to 300°C at the hot air supply means outlet 11. If the temperature at the hot air supply means outlet 11 is within the above range, it is possible to uniformly spheronize the toner particles while preventing fusion and coalescence of the toner particles caused by overheating the mixture.

[0112] The heat-treated toner particles are then cooled by cold air supplied from cold air supplying means 8-1, 8-2, and 8-3. The temperature of the cold air supplied from the cold air supplying means 8-1, 8-2, and 8-3 is preferably -20°C to 30°C. If the temperature of the cold air is within the above range, the heat-treated toner particles can be efficiently cooled, and the fusion and coalescence of the heat-treated toner particles can be prevented without impeding the uniform spheroidization of the mixture. The absolute moisture content of the cold air is 0.5 g / m 3 More than 15.0g / m 3 It is preferable that:

[0113] Next, the cooled heat-treated toner particles are collected by the collection means 10 at the bottom end of the processing chamber 6. A blower (not shown) is provided ahead of the collection means 10, which is configured to suck and transport the toner particles.

[0114] The powder particle supply port 14 is provided so that the swirling direction of the supplied mixture and the swirling direction of the hot air are the same, and the recovery means 10 of the surface treatment device is provided on the outer periphery of the treatment chamber 6 so as to maintain the swirling direction of the swirled powder particles. Furthermore, the cold air supplied from the cold air supply means 8-1, 8-2, and 8-3 is configured to be supplied from the outer periphery of the device to the inner circumferential surface of the treatment chamber 6 in a horizontal and tangential direction.

[0115] The swirling direction of the toner particles supplied from the powder supply port, the swirling direction of the cold air supplied from the cold air supply means 8, and the swirling direction of the hot air supplied from the hot air supply means 7 are all the same. As a result, no turbulence occurs within the processing chamber 6, the swirling flow within the device is strengthened, a strong centrifugal force is applied to the toner particles, and the dispersibility of the toner particles is further improved, resulting in toner particles with fewer coalesced particles and uniform shapes. When the average circularity of the toner particles is 0.950 or more and 0.980 or less, the surfaces of the toner particles are easily covered with the release agent to an appropriate degree.

[0116] The toner is then obtained by externally adding an external additive such as silica particles to the surface of the toner particles. Methods for externally adding external additives include blending the classified toner with a predetermined amount of various known external additives, and stirring and mixing them using a mixer such as a double con mixer, V-type mixer, drum mixer, super mixer, Henschel mixer, Nauta mixer, Mechano Hybrid (manufactured by Nippon Coke and Engineering Co., Ltd.), or Nobilta (manufactured by Hosokawa Micron Corporation).

[0117] <Developer> When the carrier of the present invention is mixed with a toner to be used as a two-component developer, good results are generally obtained when the mixing ratio of the magnetic carrier is 2% by mass to 15% by mass, preferably 4% by mass to 13% by mass, in terms of the toner concentration in the developer. If the toner concentration is less than 2% by mass, the image density tends to decrease, and if it exceeds 15% by mass, fogging and toner scattering tend to occur.

[0118] Furthermore, in a replenishment developer to be replenished to a developing device in response to a decrease in the toner concentration of the two-component developer in the developing device, the amount of toner is preferably 2 to 50 parts by mass per part by mass of the replenishment magnetic carrier. This range is preferable because it is unlikely that the charge amount of the toner will decrease even when images with a high image ratio are output continuously over a long period of time, and toner scattering can be suppressed.

[0119] The methods for measuring various physical properties of carriers, raw materials, and intermediates are explained below. <Method for separating magnetic core particles from carrier> 100 mL of methyl isobutyl ketone was added to 10 g of carrier, and ultrasonic cleaning was performed at 60 kHz for 15 minutes. After separating the solid component using filter paper with a retention particle size of 7 μm, 100 mL of toluene was added again, and the same washing and filtration process was repeated two more times. The resulting solid was completely dried using a vacuum dryer to obtain magnetic core particles.

[0120] <Method for separating silica particles from carrier> 10 mL of methyl isobutyl ketone was added to 10 g of carrier, and ultrasonic cleaning was performed at 60 kHz for 15 minutes. The liquid phase was recovered by decantation, and then 10 mL of toluene was added again, and the same washing and liquid phase recovery procedure was repeated two more times. All the recovered liquid phases were combined, and the magnetic material was completely removed using a permanent magnet.

[0121] The resulting liquid phase was placed in a centrifuge and rotated at 15,000 rpm for two hours to separate the solid component. 20 mL of tetrahydrofuran was added to the resulting solid component, and ultrasonic waves were applied to dissolve or disperse all of the solid component in the liquid. The resulting liquid was placed in a centrifuge and rotated at 15,000 rpm for two hours to separate the solid component, which was then completely dried using a vacuum dryer. The resulting solid component was subjected to the same tetrahydrofuran addition, centrifugation, and drying procedures twice more, and then vacuum dried at 120°C for 24 hours to obtain silica particles.

[0122] <Method for separating coating resin from carrier> 10 mL of methyl isobutyl ketone was added to 10 g of carrier, and ultrasonic cleaning was performed at 60 kHz for 15 minutes. The liquid phase was recovered by decantation, and then 10 mL of toluene was added again, and the same washing and liquid phase recovery procedure was repeated two more times. All the recovered liquid phases were combined, and the magnetic material was completely removed using a permanent magnet.

[0123] The resulting liquid phase was placed in a centrifuge and rotated at 15,000 rpm for two hours to separate the solid component. The solvent in the resulting liquid phase was concentrated by vacuum evaporation until the volume of the solution was approximately 1 mL. 15 mL of n-hexane was added, and the precipitated solid component was filtered through filter paper with a retention particle size of 1 μm, followed by washing with 15 mL of n-hexane. This procedure was repeated three times. The resulting solid component was completely dried in a vacuum dryer to obtain the coating resin.

[0124] <Method for separating silica-based external additives from toner> A sucrose solution was prepared by adding 160 g of sucrose (Kishida Chemical) to 100 mL of ion-exchanged water and dissolving it in a hot water bath. 31 g of the concentrated sucrose solution was mixed with 6 mL of Contaminon N (a 10% by weight aqueous solution of a pH 7 neutral detergent for cleaning precision measuring instruments, consisting of a nonionic surfactant, an anionic surfactant, and an organic builder, manufactured by Wako Pure Chemical Industries, Ltd.) to prepare a dispersion.

[0125] 1 g of toner was added to this dispersion, and ultrasonic cleaning was performed at an output of 60 kHz for 15 minutes to completely disperse the toner particles in the dispersion, obtaining a toner dispersion. The resulting toner dispersion was centrifuged in a centrifuge at 3500 rpm for 30 minutes.

[0126] After centrifugation, the toner was present in the top layer, and the external additive was present in the lower aqueous solution. The lower aqueous solution was collected and centrifuged to separate the sucrose and the external additive. Centrifugation was repeated as necessary to thoroughly separate the particles, and the dispersion was then dried to obtain a mixture of inorganic particles. The obtained mixture of inorganic particles was fractionated by centrifugation to obtain a silica-based external additive.

[0127] <Method for measuring the volume average particle size (D50) of magnetic carrier and magnetic core particles> The particle size distribution was measured using a laser diffraction / scattering particle size distribution measuring device "Microtrac MT3300EX" (manufactured by Nikkiso Co., Ltd.). The volume average particle size (D50) of the magnetic carrier and magnetic core particles was measured using a sample supply device for dry measurements, the "One-Shot Dry Sample Conditioner Turbotrac" (manufactured by Nikkiso Co., Ltd.). The supply conditions for the Turbotrac were a dust collector used as the reduced pressure source, with an air volume of approximately 33 L / sec and a pressure of approximately 17 kPa. Control was performed automatically on the software. The particle size was calculated as the 50% particle size (D50), which is the cumulative value of the volume average. Control and analysis were performed using the accompanying software (version 10.3.3-202D). The measurement conditions were as follows: SetZero time: 10 seconds Measurement time: 10 seconds Number of measurements: 1 Particle refractive index: 1.81% Particle shape: non-spherical Measurement upper limit: 1408 μm Measurement lower limit: 0.243μm Measurement environment: Temperature 23°C, relative humidity 50%

[0128] <Method for measuring the magnetization strength of magnetic core particles and carriers> The magnetization strength of the magnetic core particles and carrier can be measured using a vibrating sample magnetometer or a direct current magnetization characteristic recorder (BH tracer). In the examples described below, measurements are performed using a vibrating sample magnetometer BHV-30 (manufactured by Riken Denshi Co., Ltd.) according to the following procedure.

[0129] A cylindrical plastic container is filled with magnetic core particles or carriers in a sufficiently dense manner, and the sample is used as a sample. The actual mass of the sample filled in the container is measured. The sample is then adhered to the inside of the plastic container with instant adhesive to prevent it from moving. Using a standard sample, the external magnetic field axis and the magnetization moment axis are calibrated at 1000 / 4π (kA / m).

[0130] The magnetization intensity was measured from the loop of the magnetization moment when an external magnetic field of 1000 / 4π (kA / m) was applied at a sweep speed of 5 (min / roop). From this, the magnetization intensity (Am 2 / kg).

[0131] <Measurement of Average Layer Thickness of Resin Coating Layer or Silicone Resin Layer> The average thickness of the resin coating layer was measured by observing the cross section of the magnetic carrier with a transmission electron microscope (TEM) (50,000x magnification). Specifically, the magnetic carrier was subjected to ion milling using an argon ion milling device (manufactured by Hitachi High-Technologies Corporation, product name E-3500). The ion milling measurement conditions were as follows. Beam diameter: 400 μm (half width) Ion gun acceleration voltage: 5 kV Ion gun discharge voltage: 4kV Ion gun discharge current: 463 μA Ion gun irradiation current: 90 μA / cm 3 / 1min

[0132] Using a scanning electron microscope SU8220 (Hitachi High-Tech Corporation), the thickness of the resin coating layer on the cross section of the prepared magnetic carrier was measured at any five points per particle, and the arithmetic average of these measurements was taken as the thickness of the resin coating layer of the carrier particle. At this time, the image regions showing the coating resin layer part, silicone resin part, and magnetic part within the field of view can be distinguished by also using EDX observation.

[0133] The same measurement as above was performed on 50 magnetic carrier particles, and the above operation was performed on 50 particles. When the particles were arranged in order of resin layer thickness, the arithmetic average of the 30 values ​​excluding the values ​​corresponding to the 1st to 10th positions and the values ​​corresponding to the 41st to 50th positions was taken as the thickness of the resin coating layer.

[0134] <Measurement of carrier resistivity> Resistivity is measured by filling a cell with carrier, arranging a lower electrode and an upper electrode so that they are in contact with the carrier, applying a voltage between these electrodes, and measuring the current that flows. The measurement conditions for resistivity are: contact area S between the filled magnetic carrier and the electrodes = approximately 2.4 cm 2 The thickness of the sample was d = approximately 0.2 cm, and the load on the upper electrode was 240 g.

[0135] The voltage was applied under the following conditions (I), (II), and (III) in that order, and the current was measured under the applied voltage under condition (III).The thickness d of the sample was then accurately measured, and the resistivity (Ω·cm) at each electric field strength (V / cm) was calculated.The resistivity at an electric field strength of 3000 V / cm was taken as the resistivity of the magnetic carrier sample. Application conditions (I): (Change from 0V to 1000V: Increase in steps of 200V every 30 seconds) (II): (1000V, 30 seconds hold) (III): (Change from 1000V to 0V: Decrease in steps of 200V every 30 seconds) Magnetic carrier resistivity (Ω·cm) = (applied voltage (V) / measured current (A)) × S (cm 2 ) / d(cm) Electric field strength (V / cm) = applied voltage (V) / d (cm)

[0136] <Measurement of the temperature and humidity response of the carrier mass, silica particles, or coating resin> The mass of the carrier or the temperature and humidity response of the silica particles or coating resin was measured using a thermogravimetric analyzer Q5000 (manufactured by TA Instruments) under the following measurement conditions. Pan: Metallized Quartz Gas 1: Nitrogen Gas 2: Nitrogen Balance Gas: Nitrogen 10.0ml / min Humidity Gas: Nitrogen 200.0ml / min The measurement sample was measured after tare operation of the pan, and the following mass was weighed as accurately as possible. In addition, the instrument was calibrated before measurement. Carrier: 25mg Silica particles: 5 mg Coating resin: 25 mg

[0137] The measurement method was set as follows: Specifically, the sample was placed in an environment of 23°C and 5% RH for 5 hours, then changed to an environment of 30°C and 80% RH and left there for 5 hours, and then returned to an environment of 23°C and 5% RH and left there for 5 hours. 1: Equilibrate at 25.00℃ 2: Relative humidity 5.00% 3: Mark data 4: Isothermal for 300.00 min 5: Ramp 1.00℃ / min to 30.00℃ 6: Ramp relative humidity 0.50% / min to 80.00% 7: Isothermal for 300.00 min 8: Ramp relative humidity 0.50% / min to 50.00% 9: Ramp 1.00℃ / min to 23.00℃ 10: Ramp relative humidity 0.50% / min to 5.00% 11: Isothermal for 300.00 min

[0138] Of the masses recorded by the above measurements, the arithmetic mean of the masses recorded for 5 minutes from 750 minutes to 755 minutes after the start of recording was used as the mass of the carrier after being held in a first environment of 30°C and 80% relative humidity for 5 hours, and the arithmetic mean of the masses recorded for 5 minutes from 1210 minutes to 1215 minutes after the start of recording was used as the mass of the carrier after being held in the first environment and then held in a second environment of 23°C and 5% relative humidity for 5 hours.

[0139] <Method for measuring the exposure rate of silica particles on the carrier surface> The exposure rate of silica particles on the surface of the carrier was measured by analyzing a secondary electron image taken with a scanning electron microscope. Secondary electron images were obtained using a scanning electron microscope SU8220 (Hitachi High-Tech Corporation). Specifically, carrier particles were fixed in a single layer on a specimen stage for electron microscope observation with carbon tape, and observation was performed after a flushing operation. The observation conditions were as follows: SignalName=SE(U) AcceleratingVoltage=800 Volt WorkingDistance=8000 um EmissionCurrent=10000 nA LensMode=High Condenser1=5000 ScanSpeed=slow3 ColorMode=Grayscale DataSize=1280x960 Magnification=25000

[0140] When measuring the secondary electron image, the control software was set to a contrast of 60 and a brightness of -15, and the image was acquired so that the resin layer was as flat as possible in the center and the contrast resulting from the surface shape was minimized. At this point, the image regions within the field of view that represent the resin layer and the silica particle regions can be distinguished by using EDX observation in combination.

[0141] The exposure rate of silica particles on the carrier surface was calculated by analyzing the obtained secondary electron image. Specifically, the image was binarized using the programming language "Python" and the extension libraries "OpenCV" and "NumPy," and the number of pixels with a brightness value of 255 was calculated. The detailed method is as follows.

[0142] First, a 400 x 400 pixel area was trimmed from a portion of the image. In this case, an image area was selected that contained only the coating resin and silica particles to the observer's naked eye, was as smooth as possible, and had little contrast due to unevenness. An example of the image obtained is shown in Figure 1. Next, median blur processing was performed as shown in conditional formula (1) to remove noise. Note that "img" in conditional formula (1) is a variable that indicates the input image. cv2.medianBlur(img, ksize=9) Conditional expression (1)

[0143] Furthermore, the image after noise removal was binarized using Otsu's method so that it contained only pixels with a brightness value of 0 and pixels with a brightness value of 255. This process used the condition shown in conditional formula (2). Note that "img" in conditional formula (2) is a variable that indicates the image after median blur processing. cv2.threshold(img, 0, 255, cv2.THRESH_OTSU) Conditional expression (2)

[0144] For the binarized image, the number of pixels with a brightness value of 255 was calculated and divided by 160,000, the number of pixels contained in a 400 pixel x 400 pixel area, to calculate the exposure rate of silica particles on the carrier surface. The condition used here is shown in conditional formula (3). Note that "img" in conditional formula (3) is a variable that indicates the image after binarization processing. (img / 255).sum() / 160000*100 Conditional expression (3)

[0145] The above procedure was performed on 50 particles, and the arithmetic mean of the 30 values ​​excluding the values ​​1 to 10 and the values ​​41 to 50 when arranged in order of exposure rate was used as the exposure rate of silica particles on the carrier surface.

[0146] <Measurement of silicone resin coverage on the surface of magnetic core particles> The coverage of the silicone resin on the surface of the magnetic core particles was measured by analyzing backscattered electron images taken with a scanning electron microscope. It is known that in scanning electron microscope observations, the amount of backscattered electrons emitted from a sample increases with the amount of heavy elements. In samples containing both resin and core-derived metal oxide, such as the surface of magnetic core particles, the metal oxide appears bright and the resin appears dark, resulting in images with a large contrast between the two.

[0147] The backscattered electron images were obtained using a scanning electron microscope SU8220 (Hitachi High-Tech Corporation). Specifically, the carrier particles were fixed in a single layer on a specimen stage for electron microscope observation with carbon tape, and the specimen was flashed before observation. The observation conditions were as follows: SignalName=LA100(U) Accelerating Voltage=10000 Volt WorkingDistance=8000 um EmissionCurrent=10000 nA LensMode=High Condenser1=5000 ScanSpeed=slow3 ColorMode=Grayscale DataSize=1280x960 Magnification=2200

[0148] When measuring the secondary electron image, the control software was set to a contrast of 60 and a brightness of -15, and the image was acquired so that the center captured the center of the magnetic core particle. However, after acquiring the image, if the mass-equivalent abundance ratio of Si atoms measured by energy dispersive X-ray spectroscopy over the same field of view at an accelerating voltage of 20,000 volts was 10% or less of all detected elements, the image was not digitized using the image processing described below, and the coverage by silicone resin was set to 0.

[0149] The obtained backscattered electron image was analyzed to calculate the coverage of the silicone resin on the surface of the magnetic core particles. Specifically, the image was binarized using the programming language "Python" and the extension libraries "OpenCV" and "NumPy," and the number of pixels with a brightness value of 255 was calculated. An example of the detailed method is shown below.

[0150] First, a 400 pixel x 400 pixel range was cropped from a portion of the image. The image range was selected so that the center of the magnetic core particle coincided with the center of the image to the observer's naked eye. Next, median blurring was performed as shown in conditional formula (4) to remove noise. Note that "img" in conditional formula (4) is a variable that indicates the input image. cv2.medianBlur(img, ksize=9) Conditional expression (4)

[0151] Furthermore, the image after noise removal was binarized using Otsu's method so that it contained only pixels with a brightness value of 0 and pixels with a brightness value of 255. This process used the condition shown in conditional formula (5). Note that "img" in conditional formula (5) is a variable that indicates the image after median blur processing. cv2.threshold(img, 0, 255, cv2.THRESH_OTSU) Conditional expression (5)

[0152] For the binarized image, the number of pixels with a brightness value of 0 was calculated and divided by 160,000, the number of pixels contained in a 400 pixel x 400 pixel area, to calculate the coverage rate of the silicone resin on the surface of the magnetic core particles. The condition used here is shown in conditional formula (6). Note that "img" in conditional formula (6) is a variable that indicates the image after binarization processing. 1-(img / 255).sum() / 160000*100 Conditional expression (6)

[0153] The above procedure was performed on 50 particles, and the arithmetic mean of the 30 values ​​excluding the 1st to 10th and 41st to 50th values ​​when arranged in order of coverage was used as the coverage rate of the silicone resin on the surface of the magnetic core particles.

[0154] <Measurement of magnetic material coverage on the carrier surface> The coverage of the magnetic material on the surface of the carrier was measured by analyzing a backscattered electron image taken with a scanning electron microscope. The backscattered electron images were obtained using a scanning electron microscope SU8220 (Hitachi High-Tech Corporation). Specifically, the carrier particles were fixed in a single layer on a specimen stage for electron microscope observation with carbon tape, and the specimen was flashed before observation. The observation conditions were as follows: SignalName=LA100(U) Accelerating Voltage=10000 Volt WorkingDistance=8000 um EmissionCurrent=10000 nA LensMode=High Condenser1=5000 ScanSpeed=slow3 ColorMode=Grayscale DataSize=1280x960 Magnification=2200

[0155] When measuring the secondary electron image, the contrast and brightness were set on the control software, and the image was acquired under conditions that allowed for sufficient contrast to be obtained between the silica particles (silicone resin) on the surface of the carrier and the magnetic material portion.

[0156] The backscattered electron image obtained was analyzed to calculate the exposure rate of silica particles on the carrier surface. Specifically, the image was binarized using the programming language "Python" and the extension libraries "OpenCV" and "NumPy," and the number of pixels with a brightness value of 255 was calculated. The detailed method is as follows.

[0157] First, a 400 x 400 pixel range was cropped from a portion of the image. The image range was selected so that the center of the carrier particle and the center of the image coincided with the observer's naked eye. Next, median blur processing was performed as shown in conditional formula (7) to remove noise. Note that "img" in conditional formula (4) is a variable that indicates the input image. cv2.medianBlur(img, ksize=9) Conditional expression (7)

[0158] Furthermore, the image after noise removal was binarized using Otsu's method so that it contained only pixels with a brightness value of 0 and pixels with a brightness value of 255. This process used the condition shown in conditional formula (5). Note that "img" in conditional formula (8) is a variable that indicates the image after median blur processing. cv2.threshold(img, 0, 255, cv2.THRESH_OTSU) Conditional expression (8)

[0159] For the binarized image, the number of pixels with a brightness value of 0 was calculated, and the coverage rate of the magnetic material on the carrier surface was calculated by dividing this by 160,000, which is the number of pixels contained in a 400 pixel x 400 pixel area. The condition used here is shown in conditional formula (9). Note that "img" in conditional formula (9) is a variable that indicates the image after binarization processing. 1-(img / 255).sum() / 160000*100 Conditional expression (9)

[0160] The above procedure was performed on 50 particles, and the arithmetic mean of 30 values ​​excluding the 1st to 10th and 41st to 50th values ​​when arranged in order of magnetic material coverage was used as the magnetic material coverage on the carrier surface.

[0161] <Measurement of element ratio on the surface of magnetic core particles> The element ratios on the surface of the magnetic core particles were measured by XPS measurement. For the measurement, the magnetic carrier was attached to an indium foil. The particles were attached evenly so that the indium foil was not exposed. The measurement was performed using a PHI5000VERSAPROBE II (manufactured by ULVAC-PHI, Inc.) under the following measurement conditions.

[0162] A survey measurement was carried out under the same conditions as a preliminary measurement to select elements for which XPS peaks were to be observed, and then all elements detected in the main measurement were analyzed. Irradiation: AlKα radiation Output: 25W 15kV Photoelectron capture angle: 45° Pass Energy: 58.7 eV Step size: 0.125 eV Measurements were made at five or more points for each sample, and the arithmetic mean of these measurements was used as the measured value.

[0163] <Method for measuring the volume average particle size of silica particles> A solution was prepared by adding 0.2 g of 5% Triton solution and 19.8 g of RO water to 10 mg of dried silica particles. The tip of an ultrasonic disperser probe was then immersed in the solution, and ultrasonic dispersion was performed at 20 W for 15 minutes to obtain a dispersion. The volume average particle size of this dispersion was then measured using 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 Dispersion medium refractive index: 1.33 (water) Measurement time: 120 seconds

[0164] <Measurement of the density of silanol groups on the surface of silica particles> The density of silanol groups on the silica particle surface (the number of silanol groups on the surface of the silica particle per unit surface area of ​​the silica particle) was calculated using the lithium aluminum hydride (LAH) method. Specifically, the vacuum-dried silica particles were dispersed in dehydrated dimethyl ether, and a sufficient amount of LAH dimethyl ether solution was added dropwise and thoroughly stirred until hydrogen generation ceased. The amount of hydrogen generated was measured using a gas chromatograph.

[0165] The silanol group density per unit surface area was calculated by dividing the number of silanol groups calculated from the amount of hydrogen generated by the specific surface area measured using an automatic specific surface area and pore distribution analyzer, TriStar3000 (Shimadzu Corporation), which uses the constant volume gas adsorption method as its measurement method.

[0166] The measurement conditions for the specific surface area and the analysis of the measurement data are set using the dedicated software "TriStar3000 Version 4.00" that comes with the device. The device is also connected to a vacuum pump, nitrogen gas piping, and helium gas piping. Nitrogen gas is used as the adsorption gas, and the value calculated by the BET multipoint method is taken as the BET specific surface area.

[0167] <Method for measuring the work function of silica particles or silica particle external additives> A surface analyzer (Riken Keiki AC-2, low-energy electron counting system) was used to measure the work function. A deuterium lamp was used in the analyzer, with the irradiation light intensity set to 500 nW, monochromatic light selected using a spectroscope, and a spot size of 4 mm square. The energy scan range was set to 3.40 to 6.20 eV at intervals of 0.05 eV, and the sample was irradiated with light at a measurement time of 10 sec per point, and photoelectrons emitted from the sample surface were detected. The work function was measured with a repeatability (standard deviation) of 0.02 eV.

[0168] In this measurement, when the excitation energy of monochromatic light is scanned from low to high, photon emission begins at a certain energy value (eV), and this energy value is defined as the work function (eV). When the excitation energy (eV) is plotted on the horizontal axis and the normalized photon yield (the nth power of the photoelectron yield per unit photon) on the vertical axis, a certain slope (Y / eV) is obtained, and the work function is indicated by the excitation energy value (eV) at the bending point (A). An example of how to determine the bending point (A) is shown below.

[0169] Regression curve: The regression curve was created by selecting the first four points where the normalized photon yield continuously increased between 3.40 eV and 6.20 eV of the excitation energy of the irradiated light, from the first point to the fourth point where there were four or more values.

[0170] Ground line: The ground line was selected from the excitation energy of the irradiated light, 3.40 eV, up to the point not including the fulcrum. The excitation energy value at the intersection of the ground line and the regression curve was taken as the work function. To ensure data reproducibility, the measurement sample was left for 24 hours under conditions of 23°C temperature and 50% RH. [Example]

[0171] The effects of the present invention will be explained below with reference to examples. The materials, additives, amounts and concentrations used, and processing methods and procedures shown in the following examples can be modified as appropriate without departing from the spirit of the present invention, and the present invention should not be construed as being limited by the content of the examples. In the following description, "%" and "parts" are by mass unless otherwise specified.

[0172] <Toner manufacturing example> <Production example of resin A> 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 The above materials were weighed and placed in a reaction vessel equipped with a condenser, a stirrer, a nitrogen inlet tube, and a thermocouple.

[0173] Next, the atmosphere in the flask was replaced with nitrogen gas, and the temperature was gradually raised with stirring, and the mixture was allowed to react for 4 hours at a temperature of 200°C with stirring. Furthermore, the pressure inside the reaction vessel was reduced to 8.3 kPa and maintained at that level for 1 hour, after which the vessel was cooled to 160°C and returned to atmospheric pressure (first reaction step).

[0174] tert-butylcatechol (polymerization inhibitor): 0.1 parts The above materials were then added, the pressure in the reactor was reduced to 8.3 kPa, and the reaction was carried out for 1 hour while maintaining the temperature at 180°C. Once the softening point measured according to ASTM D36-86 reached 90°C, the temperature was reduced to stop the reaction (second reaction step), yielding Resin A. The resulting 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.

[0175] <Resin B manufacturing example> 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 The above materials were weighed and placed in a reaction vessel equipped with a condenser, a stirrer, a nitrogen inlet tube, and a thermocouple.

[0176] Next, the atmosphere in the flask was replaced with nitrogen gas, and the temperature was gradually raised with stirring, and the mixture was allowed to react for 2 hours at 200°C with stirring. Furthermore, the pressure inside the reaction vessel was reduced to 8.3 kPa and maintained at that level for 1 hour, after which the vessel was cooled to 160°C and returned to atmospheric pressure (first reaction step).

[0177] Trimellitic acid: 5.9 parts tert-butylcatechol (polymerization inhibitor): 0.1 parts The above materials were then added, the pressure in the reactor was reduced to 8.3 kPa, and the reaction was carried out for 15 hours while maintaining the temperature at 200°C. Once it was confirmed that the softening point measured according to ASTM D36-86 had reached 140°C, the temperature was reduced to stop the reaction (second reaction step), yielding Resin B. The resulting Resin B had a peak molecular weight Mp of 10,000, a softening point Tm of 140°C, and a glass transition temperature Tg of 60°C.

[0178] <Resin C manufacturing example> Hexanediol: 33.9 parts Dodecanedioic acid: 66.1 parts The above materials were weighed and placed in a reaction vessel equipped with a condenser, a stirrer, a nitrogen inlet tube, and a thermocouple. After the atmosphere in the flask was replaced with nitrogen gas, the temperature was gradually raised with stirring, and the mixture was allowed to react for 3 hours at 140°C with stirring.

[0179] Tin 2-ethylhexanoate: 0.5 parts The above materials were then 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 Resin C (first reaction step). The obtained Resin C had a weight-average molecular weight Mw of 11,000 and a peak melting temperature Tp of 72°C.

[0180] <Production Example of Dispersant D> Low molecular weight polypropylene (Viscol 660P manufactured by Sanyo Chemical Industries, Ltd.): 10.0 parts Xylene: 25.0 parts The above materials were weighed and placed in a reaction vessel equipped with a condenser, a stirrer, a nitrogen inlet tube, and a thermocouple. The atmosphere in the flask was then replaced with nitrogen gas, and the temperature was gradually raised to 175°C while stirring.

[0181] 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-butyl peroxyhexahydroterephthalate: 0.5 parts The above materials were then added dropwise over 3 hours and stirred for an additional 30 minutes. The solvent was then distilled off to obtain Dispersant D, in which a styrene-acrylic polymer was graft-polymerized onto polyolefin. Dispersant D had a peak molecular weight Mp of 6000 and a softening point of 125°C.

[0182] <Toner manufacturing example> Resin A 62 parts ·Resin B 28 parts ·Resin C 10 parts Dispersant D 4 parts Fischer-Tropsch wax (maximum endothermic peak temperature 90°C) 4 parts CI Pigment Blue 15:3 7 parts The above materials were mixed in a Henschel mixer (FM-75 model, manufactured by Mitsui Mining Co., Ltd.) at a rotation speed of 20 s. -1 After mixing for 5 minutes, the mixture was kneaded in a twin-screw kneader (PCM-30, manufactured by Ikegai Corporation) set at a temperature of 130°C. The kneaded mixture was cooled and coarsely pulverized to 1 mm or less using a hammer mill to obtain a coarsely pulverized product. The coarsely pulverized product was then finely pulverized using a mechanical pulverizer (T-250, manufactured by Turbo Kogyo Co., Ltd.). Further, classification was carried out using a Faculty F-300 (manufactured by Hosokawa Micron Corporation) to obtain toner particles. The operating conditions were a classifying rotor rotation speed of 130 s -1 , distributed rotor rotation speed 120s -1 It was decided.

[0183] The obtained toner particles were subjected to a heat treatment using the surface treatment device shown in FIG. 2 to obtain heat-treated toner particles. The operating conditions were a feed rate of 5 kg / hr, a hot air temperature of 160°C, and a hot air flow rate of 6 m. 3 / min., cold air temperature = -5℃, cold air flow rate = 4m 3 / min., Blower air volume = 20m 3 / min., injection air flow rate = 1m 3 / min.

[0184] 100 parts of the obtained heat-treated toner particles were mixed with hydrophobic silica particles (BET: 200m 2 / g) 1.0 part, titanium oxide fine particles surface-treated with isobutyltrimethoxysilane (BET: 80m 2 1.0 parts of 1 / g of ethanol was mixed in a Henschel mixer (FM-75, manufactured by Mitsui Miike Chemical Engineering Co., Ltd.) at a rotation speed of 30 s. -1 The mixture was mixed for 10 minutes, and a toner was obtained. The volume average particle size (D4) of the toner was measured using a CDA-1000X (aperture diameter: 100 μm, manufactured by Sysmex Corporation) and found to be 6.3 μm. The average circularity of the toner was measured using a flow particle image analyzer FPIA-3000 (manufactured by Sysmex Corporation) and found to be 0.967.

[0185] <Magnetic core particle manufacturing example> <Production example of magnetic particle 1> Process 1 (weighing and mixing process) Fe2O368.3% MnCO3 28.5% Mg(OH)22.0% SrCO31.2% The ferrite raw material was weighed so that Thereafter, 20 parts of distilled water was added to 80 parts of the above ferrite raw material mixture, and the mixture was pulverized and mixed for 3 hours in a ball mill using zirconia balls (φ10 mm) to obtain a slurry.

[0186] Process 2 (pre-firing process) The slurry was dried using a spray dryer (manufactured by Okawara Kakoki Co., Ltd.) and fired in a batch electric furnace in a nitrogen atmosphere (oxygen concentration 1.0% by volume) at a temperature of 1050°C for 3.0 hours to produce calcined ferrite.

[0187] Process 3 (crushing process) The calcined ferrite was crushed to about 0.5 mm using a crusher and then crushed for 3 hours in a wet bead mill using 1 / 8-inch diameter stainless steel beads to obtain a slurry. This slurry was then crushed for 4 hours in a wet ball mill using zirconia balls (φ1.0 mm) to obtain a calcined ferrite slurry.

[0188] Process 4 (granulation process) To 100 parts by mass of the calcined ferrite slurry, 1.0 part by mass of ammonium polycarboxylate and 1.5 parts by mass of polyvinyl alcohol were added, and the mixture was granulated into spherical particles of 37 μm using a spray dryer (manufactured by Okawara Kakoki Co., Ltd.). The resulting granules were heated at 700°C for 2 hours using a rotary electric furnace.

[0189] Step 5 (baking process) The material was fired in a nitrogen atmosphere (oxygen concentration 1.0% by volume) over a period of 2 hours from room temperature to the firing temperature (1100°C), and then held at 1100°C for 4 hours. The temperature was then lowered to 60°C over 8 hours, and the material was returned from the nitrogen atmosphere to the air and removed when the temperature was below 40°C.

[0190] Process 6 (sorting process) The agglomerated particles were crushed and sieved through a sieve with 150 μm openings to remove coarse particles, and then fine powder was removed by air classification. Furthermore, low magnetic force particles were removed by magnetic separation to obtain magnetic particles 1. When the shape of magnetic particles 1 was observed using a scanning electron microscope SU8220 (manufactured by Hitachi High-Tech Corporation), it was found to be porous and have pores.

[0191] <Production Example of Magnetic Particle 2> Process 1 (weighing and mixing process) Fe2O361.7% MnCO334.2% Mg(OH)23.0% SrCO31.1% The ferrite raw material was weighed so that Thereafter, 20 parts of distilled water was added to 80 parts of the above ferrite raw material mixture, and the mixture was pulverized and mixed for 3 hours in a ball mill using zirconia balls (φ10 mm) to obtain a slurry.

[0192] Process 2 (pre-firing process) The slurry was dried using a spray dryer (manufactured by Okawara Kakoki Co., Ltd.) and fired in a batch electric furnace in a nitrogen atmosphere (oxygen concentration 1.0% by volume) at a temperature of 1050°C for 3.0 hours to produce calcined ferrite.

[0193] Process 3 (crushing process) The calcined ferrite was crushed to about 0.5 mm using a crusher and then crushed for 3 hours in a wet bead mill using 1 / 8-inch diameter stainless steel beads to obtain a slurry. This slurry was then crushed for 4 hours in a wet ball mill using zirconia balls (φ1.0 mm) to obtain a calcined ferrite slurry.

[0194] Process 4 (granulation process) To 100 parts by mass of the calcined ferrite slurry, 1.0 part by mass of ammonium polycarboxylate and 1.5 parts by mass of polyvinyl alcohol were added, and the mixture was granulated into spherical particles of 37 μm using a spray dryer (manufactured by Okawara Kakoki Co., Ltd.). The resulting granules were heated at 700°C for 2 hours using a rotary electric furnace.

[0195] Step 5 (baking process) In order to control the firing atmosphere, firing was carried out in an electric furnace under a nitrogen atmosphere (oxygen concentration 0.6% by volume) at 1200°C for 6 hours.

[0196] Process 6 (sorting process) The agglomerated particles were crushed and sieved through a sieve with 150 μm openings to remove coarse particles, and then fine powder was removed by air classification. Furthermore, low magnetic force particles were removed by magnetic separation to obtain magnetic particles 2. When the surface shape of magnetic particles 2 was observed using a scanning electron microscope SU8220 (manufactured by Hitachi High-Tech Corporation), no particles with holes on the magnetic surface were observed.

[0197] <Magnetic core particle manufacturing example> <Production example of magnetic core particle 1> 100.0 parts of magnetic particles 1 were placed in the stirring vessel of a mixer / stirrer (a universal stirrer NDMV type manufactured by Dalton), and while maintaining the temperature at 60°C, nitrogen was introduced while reducing the pressure to 2.3 kPa. A silicone resin solution (product name SR2410, manufactured by Toray Dow Corning Co., Ltd., a toluene solution with a 10% solids content to which 1% titanium n-butoxide based on the solids content had been added) was added dropwise under reduced pressure to a resin component of 7.5 parts, and stirring was continued for 2 hours after the addition was completed.

[0198] The temperature was then raised to 70°C, the solvent was removed under reduced pressure, and the silicone resin composition obtained from the silicone resin solution was distributed within and on the surfaces of the magnetic particles 1. After cooling, the resulting magnetic core particles were transferred to a mixer (a UD-AT drum mixer manufactured by Sugiyama Heavy Industries Co., Ltd.) equipped with a spiral blade in a rotatable mixing vessel, and the temperature was raised 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 harden the resin. After heat treatment, low magnetic force particles were separated by magnetic separation and classified using a sieve with 150 μm openings to obtain magnetic core particles 1.

[0199] <Production example of magnetic core particle 2> Magnetic core particles 2 were obtained in the same manner as magnetic core particles 1, except that the magnetic particles used were changed to magnetic particles 2 and the amount of silicone resin solution added dropwise was changed to 0.5 parts as the resin component.

[0200] <Production Example of Magnetic Core Particle 3> Magnetic core particles 3 were obtained in the same manner as magnetic core particles 1, except that the amount of silicone resin solution added dropwise was 7.2 parts as the resin component.

[0201] <Production Example of Magnetic Core Particle 4> Magnetic core particles 4 were obtained in the same manner as magnetic core particles 1, except that the amount of silicone resin solution added dropwise was 6.8 parts as the resin component.

[0202] <Production Example of Magnetic Core Particle 5> Magnetic core particles 5 were obtained in the same manner as magnetic core particles 1, except that the amount of silicone resin solution added dropwise was 6.3 parts as the resin component.

[0203] <Production Example of Magnetic Core Particle 6> Magnetite microparticles (spherical, number-average particle size 250 nm) and a silane coupling agent (3-(2-aminoethylaminopropyl)trimethoxysilane) (3.0% amount relative to the magnetite microparticles) were introduced into a container. Then, the mixture was mixed and stirred at high speed at a temperature of 100°C or higher in the container to surface-treat the magnetite microparticles. Phenol 10 parts Formaldehyde solution (37% formaldehyde aqueous solution) 16 parts 84 parts of the above surface-treated magnetite particles The above materials were introduced into a reactor and mixed thoroughly at a temperature of 40°C.

[0204] The mixture was then heated to 85°C at an average heating rate of 3°C / min while stirring, and 4 parts of 28% aqueous ammonia and 25 parts of water were added to the reactor. The temperature was maintained at 85°C, and the mixture was polymerized and cured for 3 hours. The peripheral speed of the stirring blade was 1.8 m / sec.

[0205] After the polymerization reaction, the mixture was cooled to 30°C and water was added. The supernatant was removed, and the resulting precipitate was washed with water and air-dried. The air-dried product was dried under reduced pressure (5 hPa or less) at 60°C to obtain magnetic core particles 6 of a magnetic material dispersion type.

[0206] <Preparation of magnetic core particle 7> The produced magnetic particles 2 were used as magnetic core particles 7. The physical properties of each of the produced magnetic core particles are shown in Table 1.

[0207] [Table 1]

[0208] <Silica particle manufacturing example> <Production example of silica particles 1> 100 parts of methanol and 16 parts of 15% aqueous ammonia solution were added to a glass reaction vessel equipped with a stirrer and two dropping devices, and the resulting mixture was stirred at 35°C under a nitrogen stream. The stirrer rotation speed was adjusted to 150 rpm, and tetramethoxysilane and 5.4% aqueous ammonia solution were added dropwise simultaneously. The dropping devices were set so that the dropping rates were 31.1 parts per hour and 13.4 parts per hour, respectively. After 6 hours of dropwise addition of tetramethoxysilane and 5 hours of dropwise addition of 5.4% aqueous ammonia solution, the mixture was stirred for 10 minutes while maintaining the temperature.

[0209] The solvent in the resulting mixture was distilled off under reduced pressure, and the resulting solid was thoroughly dried and heated in an oven at 400°C for 10 minutes. 100 parts of the obtained solid was placed in an autoclave, and the inside of the autoclave was replaced with nitrogen. While stirring the contents of the autoclave, 0.7 parts of hexamethyldisilazane atomized with a two-fluid nozzle and 0.2 parts of distilled water were sprayed uniformly. The autoclave was sealed and stirred for 30 minutes, and then heated at 200°C for 2 hours. Thereafter, the inside pressure was reduced while still heated, and silica particles 1 were obtained.

[0210] <Production Example of Silica Particles 2> Silica particles 2 were obtained in the same manner as silica particles 1, except that the amount of methanol added was changed to 120 parts.

[0211] <Production Example of Silica Particles 3> Silica particles 3 were obtained in the same manner as silica particles 1, except that the amount of methanol added was changed to 70 parts.

[0212] <Production Example of Silica Particles 4> Silica particles 4 were obtained in the same manner as silica particles 1, except that the amount of methanol added was changed to 150 parts.

[0213] <Production Example of Silica Particles 5> Silica particles 5 were obtained in the same manner as silica particles 1, except that the amount of methanol added was changed to 55 parts.

[0214] <Production Example of Silica Particles 6> Silica particles 6 were obtained in the same manner as silica particles 1, except that the amount of hexamethyldisilazane sprayed from the two-fluid nozzle was changed to 0.2 parts and the amount of distilled water was changed to 0.5 parts.

[0215] <Production Example of Silica Particles 7> Silica particles 7 were obtained in the same manner as silica particles 1, except that the amount of hexamethyldisilazane sprayed from the two-fluid nozzle was changed to 0.1 parts and the amount of distilled water was changed to 0.5 parts.

[0216] <Production Example of Silica Particles 8> Silica particles 8 were obtained in the same manner as silica particles 1, except that the amount of methanol added was changed to 75 parts, the amount of hexamethyldisilazane sprayed using a two-fluid nozzle was changed to 1.2 parts, and the amount of distilled water was changed to 0.5 parts.

[0217] <Production Example of Silica Particles 9> Silica particles 9 were obtained in the same manner as silica particles 1, except that the amount of methanol added was changed to 70 parts, the amount of hexamethyldisilazane sprayed using a two-fluid nozzle was changed to 1.2 parts, and the amount of distilled water was changed to 0.5 parts.

[0218] <Preparation of Silica Particles 10> Commercially available fumed silica particles whose surfaces were treated with hexamethyldisilazane were prepared and used as silica particles 10.

[0219] <Production Example of Silica Particles 11> Silica particles 11 were obtained in the same manner as silica particles 1, except that the amount of hexamethyldisilazane sprayed from the two-fluid nozzle was changed to 2.5 parts and the amount of distilled water was changed to 0.3 parts.

[0220] <Production Example of Silica Particles 12> Silica particles 12 were obtained in the same manner as silica particles 1, except that the amount of hexamethyldisilazane sprayed from the two-fluid nozzle was changed to 0.05 parts and the amount of distilled water was changed to 0.7 parts.

[0221] <Production example of silica particles 13> Silica particles 13 were obtained in the same manner as silica particles 1, except that the amount of hexamethyldisilazane sprayed from the two-fluid nozzle was changed to 0.02 parts and the amount of distilled water was changed to 0.7 parts. The physical properties of the produced silica particles are shown in Table 2.

[0222] [Table 2]

[0223] <Example of coating resin production> <Production example of coating resin solution 1> 80 parts of cyclohexyl methacrylate and 20 parts of methyl methacrylate were added to a four-neck flask equipped with a reflux condenser, a thermometer, a nitrogen inlet tube, and a rotary stirrer. Further, 100 parts of toluene, 100 parts of methyl ethyl ketone, and 2.0 parts of azobisisovaleronitrile were added. The resulting mixture was maintained at 70°C for 10 hours under a nitrogen stream, and after the polymerization reaction was completed, washing was repeated to obtain a coating resin solution 1 (solid content 35%).

[0224] <Production example of coating resin solution 2> Coating resin solution 2 was obtained in the same manner as for coating resin 1, except that 60 parts of cyclohexyl methacrylate and 40 parts of methyl methacrylate were used instead of 80 parts of cyclohexyl methacrylate and 20 parts of methyl methacrylate.

[0225] <Production example of coating resin solution 3> Coating resin solution 3 was obtained in the same manner as for coating resin 1, except that 40 parts of cyclohexyl methacrylate and 60 parts of methyl methacrylate were used instead of 80 parts of cyclohexyl methacrylate and 20 parts of methyl methacrylate.

[0226] <Production example of coating resin solution 4> Coating resin solution 4 was obtained in the same manner as in coating resin solution 1, except that 100 parts of methyl methacrylate was used instead of 80 parts of cyclohexyl methacrylate and 20 parts of methyl methacrylate.

[0227] <Preparation of coating resin solution 5> Methyl ethyl ketone was added to KR271 manufactured by Shin-Etsu Chemical Co., Ltd. to adjust the solid content to 35%, and this was used as coating resin solution 5.

[0228] <Production of Resin Coating Solution 1> Toluene and methyl ethyl ketone were added in a 1:1 ratio to 100 parts of coating resin solution 1 so that the solid content ratio was 5% as resin solid content. 25 parts of silica particles 1 were then added, and the resulting mixture was shaken and stirred for 15 minutes using a paint shaker (manufactured by RADIA) to obtain resin coating solution 1.

[0229] <Method for producing resin coating solutions 2 to 23> Resin coating solutions 2 to 23 were obtained in the same manner as Resin Coating Solution 1, except that the type of coating resin solution and the type and amount of silica particles added were changed as shown in Table 3.

[0230] [Table 3]

[0231] <Magnetic carrier manufacturing example> <Magnetic Carrier 1 Manufacturing Example> Magnetic core particles 1 100 parts Resin coating liquid 1 40 parts The above materials were charged into a planetary mixer (Nauta Mixer VN type manufactured by Hosokawa Micron Corporation) maintained at a reduced pressure (1.5 kPa) and a temperature of 60°C. The charging method was as follows: first, the entire amount of magnetic core particles was charged, then 1 / 3 of the resin coating liquid was charged, and the solvent was removed and coated for 20 minutes. Next, another 1 / 3 of the resin coating liquid was charged, and the solvent was removed and coated for 20 minutes, and then another 1 / 3 of the resin coating liquid was charged, and the solvent was removed and coated for 20 minutes.

[0232] The magnetic carrier coated with the coating resin composition was then transferred to a mixer (a UD-AT drum mixer manufactured by Sugiyama Heavy Industries Co., Ltd.) equipped with a spiral blade and placed in a rotatable mixing container. While stirring at 10 revolutions per minute, the mixture was heat-treated in a nitrogen atmosphere at 120°C for 2 hours. The resulting magnetic carrier 1 was separated by magnetic separation to separate out low-magnetic-force particles, which were then passed through a sieve with 150 μm openings and then classified using an air classifier to obtain magnetic carrier 1.

[0233] <Manufacturing Examples of Magnetic Carriers 2 to 24> Magnetic Carriers 2 to 24 were obtained in the same manner as Magnetic Carrier 1, except that the types and amounts of the magnetic core particles and resin coating liquid added were changed as shown in Table 4.

[0234] <Magnetic Carrier 25 Manufacturing Example> Magnetic core particles 1 100 parts Resin coating liquid 19 40 parts The above materials were charged into a planetary mixer (Nauta Mixer VN type manufactured by Hosokawa Micron Corporation) maintained at a reduced pressure (1.5 kPa) and a temperature of 40°C. The charging method was as follows: first, the entire amount of magnetic core particles was charged, then 1 / 3 of the resin coating liquid was charged, and the solvent was removed and coated for 20 minutes. Next, another 1 / 3 of the resin coating liquid was charged, and the solvent was removed and coated for 20 minutes, and then another 1 / 3 of the resin coating liquid was charged, and the solvent was removed and coated for 20 minutes.

[0235] The contents were then transferred to a mixer equipped with a spiral blade in a mixing vessel (a UD-AT drum mixer manufactured by Sugiyama Heavy Industries Co., Ltd.) and heat-treated at 200°C for 2 hours in a nitrogen atmosphere while stirring at 10 revolutions per minute, thereby obtaining magnetic carrier 25.

[0236] <Manufacturing example of magnetic carriers 26 to 30> Magnetic Carriers 26 to 30 were obtained in the same manner as Magnetic Carrier 1, except that the types and amounts of the magnetic core particles and resin coating liquid added were changed as shown in Table 4. Table 4 shows the physical properties and composition of the manufactured magnetic carrier.

[0237] [Table 4]

[0238] <Example of developer manufacturing> <Manufacturing example of two-component developer 1> 10 parts by mass of toner was added to 90 parts by mass of magnetic carrier 1, and the mixture was shaken in a shaker (product name: YS-8D model, manufactured by Yayoi Co., Ltd.) to prepare 300 g of a two-component developer. The shaking conditions using the shaker were 200 rpm and 5 minutes.

[0239] <Production examples of two-component developers 2 to 30> In the production example of two-component developer 1, the same operation was carried out except that the combinations were changed to those shown in Table 5, thereby obtaining two-component developers 2 to 30.

[0240] <Production example of replenishment developer 1> 95 parts by mass of toner was added to 5 parts by mass of magnetic carrier 1, and mixed for 5 minutes in a V-type mixer to obtain replenishment developer 1.

[0241] <Production examples of replenishment developers 2 to 30> Replenishment developers 2 to 30 were obtained in the same manner as in the production example of replenishing developer 1, except that the combinations were changed to those shown in Table 5.

[0242] Example 1 The image forming apparatus used was a modified Canon full-color copier (product name: imagePRESS V1350). The image forming speed was set to 100 sheets per minute in full color, A4 size. The development contrast was made adjustable to any value, and the machine was modified so that automatic correction by the main unit would not operate. The evaluation paper was GFC-081 (81.0 g / m 2 ) (Canon Marketing Japan Inc.) was used. I modified it so that it could output images in monochrome. Each measurement was repeated a number of times until the measurement error was sufficiently small, and the arithmetic mean value was used as the measurement value.

[0243] (1) Evaluation of image density A durability test was carried out by placing 600 g of two-component developer 1 in the developing device, setting a replenishment developer container containing replenishment developer 1 in the developing device, forming an image, and carrying out a durability test under the following conditions. Temperature 23℃ / Humidity 5%RH Number of images output: 10,000 Output image: FFH output chart with 2% image ratio Here, FFH is a value that represents 256 gradations in hexadecimal, with 00H being the first gradation of the 256 gradations (white background) and FFH being the 256th gradation of the 256 gradations (solid area).

[0244] Before the test began, a 1cm square FFH patch was printed, and the development contrast was adjusted so that the cyan image density value of the patch area measured with a spectrodensitometer eXact Advance (manufactured by X-Rite) was 1.55. The image forming device was then set to maintain this development contrast throughout the durability test. After the test, the same square FFH patch was printed again, and the cyan image density value was measured. The higher the value, the more the charge increase during the durability test was suppressed, and the more the image density was maintained.

[0245] The evaluation of this test was determined based on the following criteria for the density of the square FFH patch output after the durability test. A: 1.50 or more B: 1.40 or more and less than 1.50 C: 1.30 or more and less than 1.40 D: Less than 1.30

[0246] (2) Evaluation of toner contamination suppression A durability test was carried out by placing 600 g of two-component developer 1 in the developing device, setting a replenishment developer container containing replenishment developer 1 in the developing device, forming an image, and carrying out a durability test under the following conditions. Temperature 27℃ / Humidity 80%RH Number of output images: 300,000 Output image: FFH output chart with 40% image ratio Before the test began, a 1 cm square FFH patch was printed, and the development contrast was adjusted so that the cyan value of the image density of the patch area measured using a spectrodensitometer eXact Advance (manufactured by X-Rite) was 1.45.Thereafter, during the durability test, similar measurements were made every 500 images printed, and the development contrast was adjusted each time so that the cyan value of the image density of the patch area was 1.45.

[0247] The evaluation of this test was performed by visually checking the degree of toner contamination inside the image forming apparatus after the durability test and comparing it with the following criteria: The less the degree of toner contamination, the greater the effect of maintaining charge even when used in a high humidity environment. A: No toner contamination was observed. B: Toner contamination is very thin or only locally observed. C: Toner contamination is observed throughout the entire image, but does not affect the output image and does not pose a problem in practical use. D: Toner contamination was observed throughout the entire print, and problems in practical use such as an effect on the output image were confirmed.

[0248] <Examples 2 to 25, Comparative Examples 1 to 5> The evaluation was carried out in the same manner as in Example 1, except that the developers used were changed to the combinations shown in Table 5. The evaluation results for each example and comparative example are shown in Table 5. When all evaluation results were rated C or higher, it was determined that the effects of the present invention were manifested.

[0249] [Table 5]

[0250] The disclosure of this embodiment includes the following configuration. (Configuration 1) A magnetic carrier for electrostatic development, comprising magnetic core particles and a coating resin layer that coats the surfaces of the magnetic core particles, the magnetic core particles are particles having a silicone resin on the surface thereof, the coating resin layer is a layer containing a vinyl resin as a binder resin and silica particles, A magnetic carrier for electrostatic charge development, characterized in that when the mass of the magnetic carrier for electrostatic charge development after being kept in a first environment having a temperature of 30°C and a relative humidity of 80% for 5 hours is defined as M1, and the mass of the magnetic carrier for electrostatic charge development after being kept in the first environment for 5 hours after being kept in a second environment having a temperature of 23°C and a relative humidity of 5% for 5 hours is defined as M2, M1 and M2 satisfy the following formula (1): 0.055≦(M1-M2) / M1×100≦0.200 Formula (1) (Configuration 2) 2. The magnetic carrier for electrostatic development according to claim 1, wherein the silicone resin has a coverage of 60% or more on the surface of the magnetic core particles. (Configuration 3) The magnetic carrier for electrostatic development according to configuration 1 or 2, wherein, on the surface of the magnetic core particle, when the abundance ratio of silicon atoms is Si_atm (atomic %) and the total abundance ratio of iron, manganese, magnesium, strontium, copper, zinc, nickel, and cobalt atoms is M_atm (atomic %), Si_atm and M_atm satisfy the following formula (2): M_atm / Si_atm<0.4 Equation (2) (Configuration 4) 4. The magnetic carrier for electrostatic charge development according to any one of configurations 1 to 3, wherein the ratio of the area of ​​the portion where the silica particles are exposed to the surface of the magnetic carrier for electrostatic charge development relative to the surface area of ​​the coating resin layer is 10% or more. (Configuration 5) The magnetic carrier for electrostatic development according to any one of configurations 1 to 4, wherein M3 is the mass of the silica particles after being held in the first environment for 5 hours, and M4 is the mass of the silica particles after being held in the first environment for 5 hours and then held in the second environment for 5 hours, and M3 and M4 satisfy the following formula (3): 3.00≦(M3-M4) / M3×100≦10.0 Formula (3) (Configuration 6) The magnetic carrier for electrostatic development according to any one of configurations 1 to 5, wherein M5 is the mass of the vinyl resin after being held in the first environment for 5 hours, and M6 is the mass of the vinyl resin after being held in the first environment for 5 hours and then held in the second environment for 5 hours, and M5 and M6 satisfy the following formula (4): 0≦(M5-M6) / M5×100≦0.60 Formula (4) (Configuration 7) 7. The magnetic carrier for electrostatic charge development according to any one of configurations 1 to 6, wherein the silica particles are wet silica particles. (Configuration 8) 8. The magnetic carrier for electrostatic charge development according to any one of configurations 1 to 7, wherein the volume average particle size of the silica particles is 50 nm or more and 250 nm or less. (Configuration 9) The number of silanol groups on the surface of the silica particle per unit surface area of ​​the silica particle is 1.0 / nm 2 More than 2.0 pieces / nm 2 9. A magnetic carrier for electrostatic charge development according to any one of configurations 1 to 8, which is as follows: (Configuration 10) 10. The magnetic carrier for electrostatic charge development according to any one of configurations 1 to 9, wherein the vinyl resin contains a unit derived from a (meth)acrylic acid ester monomer. (Configuration 11) 11. The magnetic carrier for electrostatic charge development according to any one of configurations 1 to 10, wherein the vinyl resin is a copolymer containing at least one type of monomer, including a (meth)acrylic acid ester having a cyclic hydrocarbon group in its molecular structure. (Configuration 12) 12. The magnetic carrier for electrostatic charge development according to any one of configurations 1 to 11, wherein the magnetic core particles have a structure in which the pores of magnetic particles having pores are filled with a silicone resin. [Explanation of symbols]

[0251] 1 Raw material quantitative supply means 2. Compressed gas adjustment means 3 Introductory tube 4. Protruding member 5 Supply pipe 6 Processing Room 7 Hot air supply means 8-1, 8-2, 8-3 Cold air supply means 9. Regulatory measures 10. Recovery Methods 11 Hot air supply means outlet 12 Distribution member 13 Swivel member 14 Powder particle supply port

Claims

1. A magnetic carrier for electrostatic development, comprising magnetic core particles and a coating resin layer that coats the surfaces of the magnetic core particles, the magnetic core particles are particles having a silicone resin on the surface thereof, the coating resin layer is a layer containing a vinyl resin as a binder resin and silica particles, A magnetic carrier for electrostatic charge development, characterized in that when the mass of the magnetic carrier for electrostatic charge development after being held in a first environment having a temperature of 30°C and a relative humidity of 80% for 5 hours is defined as M1, and the mass of the magnetic carrier for electrostatic charge development after being held in the first environment for 5 hours after being held in a second environment having a temperature of 23°C and a relative humidity of 5% for 5 hours is defined as M2, M1 and M2 satisfy the following formula (1): 0.055≦(M1-M2) / M1×100≦0.200 Formula (1)

2. 2. The magnetic carrier for electrostatic development according to claim 1, wherein the coverage of the surface of the magnetic core particles with the silicone resin is 60% or more.

3. 2. The magnetic carrier for electrostatic development according to claim 1, wherein, on the surface of the magnetic core particle, when the abundance ratio of silicon atoms is Si atm (atomic %) and the total abundance ratio of iron, manganese, magnesium, strontium, copper, zinc, nickel, and cobalt atoms is M atm (atomic %), Si atm and M atm satisfy the following formula (2): M_atm / Si_atm<0.4 Formula (2)

4. 2. The magnetic carrier for electrostatic charge development according to claim 1, wherein the ratio of the area of ​​the exposed portion of the silica particles to the surface area of ​​the coating resin layer on the surface of the magnetic carrier for electrostatic charge development is 10% or more.

5. 2. The magnetic carrier for electrostatic development according to claim 1, wherein M3 is the mass of the silica particles after being held in the first environment for 5 hours, and M4 is the mass of the silica particles after being held in the first environment for 5 hours and then held in the second environment for 5 hours, and M3 and M4 satisfy the following formula (3): 3.00≦(M3-M4) / M3×100≦10.0 Formula (3)

6. 2. The magnetic carrier for electrostatic development according to claim 1, wherein M5 is the mass of the vinyl resin after being held in the first environment for 5 hours, and M6 is the mass of the vinyl resin after being held in the first environment for 5 hours and then held in the second environment for 5 hours, and M5 and M6 satisfy the following formula (4): 0≦(M5-M6) / M5×100≦0.60 Formula (4)

7. 2. The magnetic carrier for electrostatic development according to claim 1, wherein the silica particles are wet silica particles.

8. 2. The magnetic carrier for electrostatic development according to claim 1, wherein the volume average particle size of the silica particles is 50 nm or more and 250 nm or less.

9. The number of silanol groups on the surface of the silica particle per unit surface area of ​​the silica particle is 1.0 / nm ２ 2.0 pieces / nm or more ２ 2. The magnetic carrier for electrostatic development according to claim 1, wherein:

10. 2. The magnetic carrier for electrostatic development according to claim 1, wherein the vinyl resin contains a unit derived from a (meth)acrylic acid ester monomer.

11. 2. The magnetic carrier for electrostatic charge development according to claim 1, wherein the vinyl resin is a copolymer containing at least one monomer containing a (meth)acrylic acid ester having a cyclic hydrocarbon group in its molecular structure.

12. 2. The magnetic carrier for electrostatic charge development according to claim 1, wherein the magnetic core particles have a structure in which the pores of the magnetic particles are filled with a silicone resin.

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