JP2008233763A - Electrophotographic carrier, and electrophotographic developer, electrophotographic developer cartridge, process cartridge, and image forming apparatus each using the carrier - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrophotographic carrier excellent in charging characteristics and adhesiveness with magnetic particles and providing high picture quality without fog or a void, and also to provide an electrophotographic developer, an electrophotographic developer cartridge, a process cartridge, and an image forming apparatus, each using the carrier. <P>SOLUTION: The electrophotographic carrier is characterized in that: the carrier comprises at least magnetic particles and a coating resin layer covering the surface of the magnetic particles; the coating resin layer contains a copolymer of (meth)acrylate having a cycloalkyl group in a side chain and (meth)acrylate having a nitrogen atom in a side chain; and the acid value of the copolymer ranges from 10 to 40 mgKOH/g. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an electrophotographic carrier, an electrophotographic developer using the same, an electrophotographic developer cartridge, a process cartridge, and an image forming apparatus.

  A method of visualizing image information through an electrostatic latent image such as electrophotography is currently used in various fields. In electrophotography, an electrostatic latent image is formed on a photoreceptor by charging and exposure processes, the electrostatic latent image is developed with a developer containing toner, and visualized through a transfer and fixing process.

  The developer used here includes a two-component developer composed of a toner and a carrier, and a one-component developer used alone, such as a magnetic toner. Among them, the two-component developer has a feature such as good controllability because the carrier shares functions such as stirring, transporting and charging of the developer and is separated as a developer, and is currently widely used. Yes. In particular, a developer using a carrier coated with a resin has excellent charge controllability and is relatively easy to improve environment dependency.

  In order to improve the adhesion to the core material, a carrier using a polymer of an alicyclic methacrylate and a chain methacrylate as a coating resin has been proposed (see Patent Document 1).

  Furthermore, from the viewpoint of suppressing environmental dependency, a carrier using a vinyl copolymer having an acid value of 2 to 40 mgKOH / g as a coating resin layer has been proposed (see Patent Document 2).

Japanese Patent Laid-Open No. 7-114219 JP-A-10-333364

  As in Document 1, since the chain methacrylate has high hydrophilicity, the carrier may undergo a change in charge (environment dependency) due to an environmental change such as humidity. In addition, since the resin itself is fragile, the coating resin is scraped by stirring in the developing machine, so that the charging ability of the carrier decreases, and as a result, the amount of toner in the developer increases to secure the charge amount necessary for development. However, as a result of a decrease in the development amount or an increase in the amount of toner in the developer, the toner may scatter from the developing device, resulting in image contamination (fogging).

  When a two-component developer composed of a magnetic carrier and a toner is used, the toner is developed by applying a predetermined developing bias to the developing roll and applying a developing electric field between the developing roll and the image carrier. In such a process, a part of the magnetic carrier may move to the surface of the image carrier due to electrostatic attraction force.

  On the other hand, a fine powder carrier (crushed carrier) generated in a developer manufacturing process or in a developing device is often sharp and fragmented, unlike a substantially spherical carrier. Therefore, when a phenomenon occurs in which a part of the magnetic carrier moves to the surface of the image carrier due to electrostatic attraction force, the transfer electric field or the image carrier and the object to be covered are transferred when the toner image is transferred to the transfer material. By receiving the transfer pressure with the transfer material, the fine powder carrier is easily embedded in the surface of the image carrier, and when it adheres to the surface of the image carrier, it is fixed as it is, resulting in white spots in the image.

  Thus, the present condition is that the carrier which is excellent in an electrical charging characteristic and adhesiveness with a core material (magnetic particle), and implement | achieves the high image quality which does not have a fog and a white spot is not found until now.

An object of the present invention is to provide an electrophotographic carrier excellent in charging characteristics and adhesion to magnetic particles, and capable of forming a high image quality without fogging or white spots.
Another object of the present invention is to provide an electrophotographic developer, an electrophotographic developer cartridge, a process cartridge, and an image forming apparatus using the carrier.

The above-mentioned subject is achieved by the following present invention. That is, the present invention
<1> At least magnetic particles and a coating resin layer that covers the surface of the magnetic particles, and the coating resin layer includes a (meth) acrylic acid ester having a cycloalkyl group in the side chain and the side A carrier for electrophotography, comprising a copolymer with a (meth) acrylic acid ester having a nitrogen atom in the chain, wherein the acid value of the copolymer is from 10 mgKOH / g to 40 mgKOH / g.

  <2> The electron according to <1>, wherein the content of the (meth) acrylic acid ester having a cycloalkyl group in the side chain in the copolymer is 90% by weight or more and 98% by weight or less. Photo carrier.

  <3> The carrier for electrophotography according to <1> or <2>, wherein the copolymer has a weight average molecular weight Mw of 30,000 to 150,000.

<4> The electrophotographic carrier according to any one of <1> to <3>, wherein the magnetic particles satisfy the following formula (1).
Formula (1): 2.0 <= A / a <= 7.0
[Wherein, in formula (1), A represents the BET specific surface area (unit: m ² / g) of the magnetic particles, a represents the spherical equivalent specific surface area (unit: m ² / g) of the magnetic particles, The spherical equivalent surface area a is defined as a = 6 / (d, where d (unit: μm) is the volume average particle diameter of the magnetic particles and ρ (unit: dimensionless) is the true specific gravity of the magnetic particles. Xρ). ]

  <5> The electrophotographic apparatus according to any one of <1> to <4>, wherein the (meth) acrylic acid ester having a cycloalkyl group in the side chain is cyclohexyl (meth) acrylate Career.

  <6> The electrophotographic carrier according to any one of <1> to <5>, wherein the coating resin layer contains a conductive agent.

  <7> An electrophotographic developer comprising a toner and the electrophotographic carrier according to any one of <1> to <6>.

<8> A developer that is detachable from the image forming apparatus and stores at least a developer for developing the electrostatic latent image formed on the surface of the electrostatic latent image holding member to form a toner image is stored. The developer is an electrophotographic developer cartridge according to <7>, wherein the developer is an electrophotographic developer cartridge.
<9> The developer for electrophotography according to the above <7> is accommodated, and the electrostatic latent image formed on the surface of the electrostatic latent image holding member is developed with the developer for electrophotography to form a toner image. From the developing means to be formed, the electrostatic latent image holding member, the charging means for charging the surface of the electrostatic latent image holding member, and the cleaning means for removing the toner remaining on the surface of the electrostatic latent image holding member And a process cartridge that is detachable from an image forming apparatus.

  <10> At least an electrostatic latent image holding member, charging means for charging the surface of the electrostatic latent image holding member, and electrostatic latent image formation for forming an electrostatic latent image on the surface of the electrostatic latent image holding member Developing means for developing the electrostatic latent image with a developer to form a toner image; transfer means for transferring the toner image to a recording medium; and fixing means for fixing the toner image to the recording medium; And the developer is the electrophotographic developer according to <7>.

According to the present invention, it is possible to provide an electrophotographic carrier that is excellent in charging characteristics and adhesion to magnetic particles, and that can form high image quality without fogging or white spots.
Furthermore, according to the present invention, an electrophotographic developer, an electrophotographic developer cartridge, a process cartridge, and an image forming apparatus using the carrier can be provided.

[Electrophotographic carrier]
The electrophotographic carrier of the embodiment (hereinafter sometimes abbreviated as carrier) has magnetic particles and a coating resin layer that covers the surface of the magnetic particles. The coating resin layer contains a copolymer of (meth) acrylic acid ester having a cycloalkyl group in the side chain and (meth) acrylic acid ester having a nitrogen atom in the side chain, and the acid value of the copolymer is It is 10 mgKOH / g or more and 40 mgKOH / g or less.

The carrier according to the embodiment is excellent in charging characteristics and adhesion to magnetic particles, and has an effect that a high image quality without fogging or white spots can be formed. The reason for this is not clear, but is presumed to be as follows.
An acrylic resin having a cycloalkyl group has high hydrophobicity and is excellent with respect to a difference in charging environment, but has a problem in adhesion to magnetic particles and brittleness of the resin. Therefore, by copolymerizing a monomer having a cycloalkyl group and a monomer having a nitrogen atom, the monomer having a nitrogen atom is oriented toward the magnetic particles, and the adhesion between the magnetic particles and the resin can be ensured. On the other hand, the cycloalkyl group is oriented to the carrier surface, but does not have a π electron cloud like a benzene ring, so when the orientation progresses and the faces of the cycloalkyl group are aligned, the coating film becomes brittle and wears. On the other hand, it becomes weak.
Therefore, by adding acrylic acid or methacrylic acid (increasing the acid value), the orientation of the cycloalkyl group can be broken to some extent, and the coating film is made stronger by hydrogen bonding between carboxyl groups. It is considered possible.
Moreover, it is preferable that the magnetic particles of the embodiment satisfy the formula (1) to be described later, whereby even when a resin having a cycloalkyl group is used for the coating resin layer, the peeling of the coating resin layer is further suppressed, and the long term Therefore, it is considered that a high-quality image free from fogging and white spots can be stably provided over a long period of time.

-Coating resin layer-
The coating resin layer contains a copolymer of (meth) acrylic acid ester having a cycloalkyl group in the side chain and (meth) acrylic acid ester having a nitrogen atom in the side chain.
The said coating resin layer coat | covers the surface of the magnetic body particle mentioned later.

  Examples of the cycloalkyl group in the (meth) acrylic acid ester having a cycloalkyl group in the side chain include cycloalkyl groups having 3 to 10 carbon atoms, and specific examples include a cyclohexyl group, a cyclopentyl group, an adamantyl group, Examples thereof include a cyclopropyl group, a cyclobutyl group, a cycloheptyl group, a cyclooctyl group, a cyclononyl group, a cyclodecyl group, an isobornyl group, a norbornyl group, and a boronyl group. Of these, a cyclohexyl group and a cyclopentyl group are preferred, and a cyclohexyl group is particularly preferred from the viewpoint of high adhesion to magnetic particles due to its structural stability.

(Meth) acrylic acid means either or both of acrylic acid and methacrylic acid.
In the embodiment, either acrylic acid ester or methacrylic acid ester can be used, but methacrylic acid ester is more preferable from the viewpoint of the glass transition temperature of the copolymerized polymer.

  Having a cycloalkyl group in the side chain means that the (meth) acrylic acid ester has a main chain structure and the side chain has a cycloalkyl group.

  The content of the (meth) acrylic acid ester copolymer having a cycloalkyl group in the side chain is preferably 90% by weight to 98% by weight, and more preferably 91% by weight to 97% by weight. 92 wt% or more and 96 wt% or less is particularly preferable. By setting it in the above range, the hydrophobicity is high, so that the charge difference in a high temperature / high humidity / low temperature / low humidity environment can be reduced.

Any (meth) acrylic acid ester having a nitrogen atom in its side chain can be used without particular limitation as long as it has a nitrogen atom.
Examples of the substituent having a nitrogen atom include amino group, methylamino group, carbamoyl group, ethylamino group, dimethylamino group, butylamino group, cyclopentylamino group, 2-ethylhexylamino group, dodecylamino group, anilino group, and naphthylamino. Group, 2-pyridylamino group, sulfonamido group, sulfamoyl group, carbamoyl group amide group and the like.
Specifically, for example, ester compounds (polyamide, polyimide, etc.), dimethylaminomethyl methacrylate, dimethylaminoethyl methacrylate, N, N-dimethylaminomethyl acrylate, N, N-dimethylaminoethyl acrylate, N, N-dimethylaminopropyl Acrylate, N, N-dimethylaminomethyl methacrylate, N, N-dimethylaminoethyl methacrylate, N, N-dimethylaminopropyl methacrylate, N, N-diethylaminomethyl acrylate, N, N-diethylaminoethyl acrylate, N, N-diethylamino Propyl acrylate, N, N-diethylaminomethyl methacrylate, N, N-diethylaminoethyl methacrylate, N, N-diethylaminopropyl methacrylate, N, N- Propylaminomethyl acrylate, N, N-dipropylaminoethyl acrylate, N, N-dipropylaminopropyl acrylate, N, N-dipropylaminomethyl methacrylate, N, N-dipropylaminoethyl methacrylate, N, N-di Propylaminopropyl methacrylate, N, N-methylethylaminomethyl acrylate, N, N-methylethylaminoethyl acrylate, N, N-methylethylaminopropyl acrylate, N, N-methylethylaminomethyl methacrylate, N, N-methyl Ethylaminoethyl methacrylate, N, N-methylethylaminopropyl methacrylate, N, N-methylpropylaminomethyl acrylate, N, N-methylpropylaminoethyl acrylate, N, N-methylpro Ruaminopropyl acrylate, N, N-methylpropylaminomethyl methacrylate, N, N-methylpropylaminoethyl methacrylate, N, N-methylpropylaminopropyl methacrylate, N, N-ethylpropylaminomethyl acrylate, N, N-ethyl Examples include propylaminoethyl acrylate, N, N-ethylpropylaminopropyl acrylate, N, N-ethylpropylaminomethyl methacrylate, N, N-ethylpropylaminoethyl methacrylate, N, N-ethylpropylaminopropyl methacrylate, and the like. .
Of these, dimethylaminoethyl methacrylate is preferred from the viewpoint of charge imparting ability.

The content of the copolymer of (meth) acrylic acid ester having a nitrogen atom in the side chain is preferably 0.1% by weight or more and 8.5% by weight or less, and 0.5% by weight or more and 8.0% by weight or less. It is more preferable that the content is 0.8% by weight or more and 5.0% by weight or less.
By setting it within the above range, good charging characteristics can be maintained.

  Having a nitrogen atom in the side chain means that the (meth) acrylic acid ester has a main chain structure and the side chain has a substituent containing a nitrogen atom.

The polymerization ratio in the copolymer of (meth) acrylic acid ester having a cycloalkyl group in the side chain and (meth) acrylic acid ester having a nitrogen atom in the side chain is 99.5: 0.5 to 92: 8. It is preferable that the ratio is 99.5: 0.5 to 95: 5.
By setting it as the said range, the adhesiveness of a coating resin layer and a magnetic body particle and fluidity | liquidity can be improved, maintaining the favorable charging characteristic as a carrier.

  The copolymer can contain other components as long as the effects of the embodiments are not impaired.

  The acid value of the copolymer of (meth) acrylic acid ester having a cycloalkyl group in the side chain and (meth) acrylic acid ester having a nitrogen atom in the side chain is from 10 mgKOH / g to 40 mgKOH / g. It is more preferably 12 mgKOH / g or more and 38 mgKOH / g or less, and particularly preferably 15 mgKOH / g or more and 35 mgKOH / g or less.

By setting the acid value within the above range, the orientation of the cycloalkyl group in the copolymer on the carrier surface can be broken, and the coating film of the coating resin layer can be made stronger by hydrogen bonding between carboxyl groups. Can be.
When the acid value is more than 40 mgKOH / g, the strength of the coating film is improved, but (meth) acrylic acid oozes out on the carrier surface and may deteriorate the charging characteristics. If the acid value is less than 10 mgKOH / g, it may be difficult to sufficiently improve the strength of the film.

  The weight average molecular weight Mw of the copolymer is preferably from 30,000 to 150,000, more preferably from 40,000 to 140,000, and particularly preferably from 50,000 to 120,000.

By setting the weight average molecular weight within the above range, the strength of the film can be sufficiently maintained.
When the weight average molecular weight Mw is less than 30,000, molecular chain entanglement is reduced, so that the cycloalkyl group in the polymer tends to be oriented on the carrier surface, and it is difficult to maintain sufficient strength of the coating resin. It is thought that it becomes.
On the other hand, when the weight average molecular weight Mw is more than 150,000, the entanglement of the molecular chain becomes strong, so that the (meth) acrylic acid ester having a nitrogen atom cannot be oriented to the magnetic particle side, Not only does the adhesion not improve, but the (meth) acrylic acid ester, acrylic acid, or methacrylic acid having a nitrogen atom tends to come out on the surface of the carrier, so that the charging characteristics may be deteriorated.

  Moreover, you may use together other resin other than an above-described copolymer for the coating resin layer used for embodiment. Examples of the resin used in combination include polystyrene, polyvinyl acetate, polyvinyl alcohol, polyvinyl butyral, polyvinyl chloride, polyvinyl ether, polyvinyl ketone, vinyl chloride-vinyl acetate copolymer, styrene-acrylic acid copolymer, and organosiloxane bond. Examples include, but are not limited to, straight silicone resins or modified products thereof, fluororesins, polyesters, polycarbonates, phenol resins, epoxy resins, urea resins, urethane resins, and melamine resins. These resins may be used alone or in combination of two or more.

  The total content of the coating resin layer in the carrier of the embodiment is preferably in the range of 0.5 to 10 parts by weight, more preferably 1 to 5 parts by weight with respect to 100 parts by weight of the magnetic particles. The amount is particularly preferably 1 part by weight or more and 3 parts by weight or less. If the content of the coating resin layer is less than 0.5 part by weight, the surface exposure of the magnetic particles is too much, so that a development electric field may be easily injected. Further, when the content of the coating resin layer is more than 10 parts by weight, the resin powder released from the coating resin layer increases, and there is a possibility that the carrier resin powder peeled into the developer from the initial stage is contained. is there.

  The coverage of the magnetic particle surface by the coating resin layer is preferably 80% or more, more preferably 85% or more, and the closer to 100%, the more preferable. When the coverage is less than 80%, when used for a long period of time, the electrical resistance of the carrier is lowered due to peeling of the coating resin, etc., and as a result, charge injection into the carrier occurs, so that charge injection occurs. In some cases, the carrier moves onto the photosensitive member and white spots occur on the image.

  In addition, the coverage of a coating resin layer can be calculated | required by XPS measurement. JPS80 manufactured by JEOL Ltd. is used as the XPS measuring apparatus, and the measurement is performed using MgKα ray as the X-ray source, setting the acceleration voltage to 10 kV, and the emission current to 20 mV, and constituting the coating resin layer. Element (usually carbon) and main elements constituting magnetic particles (for example, iron and oxygen when the magnetic particles are iron oxide-based materials such as magnetite) are measured (hereinafter, the magnetic particles are iron oxide) The explanation is based on the assumption that the system is a system). Here, the C1s spectrum is measured for carbon, the Fe2p3 / 2 spectrum is measured for iron, and the O1s spectrum is measured for oxygen.

Based on the spectrum of each of these elements, the number of elements of carbon (A _C ), oxygen (A _O ), and iron (A _Fe ) (A _C + A _O + A _Fe ) was determined, and the obtained carbon, oxygen, Based on the following formula (I), the iron content rate after coating the magnetic particles alone and the magnetic particles with the coating resin layer (carrier) is determined from the ratio of the number of iron elements, and then the following formula (II) ) To obtain the coverage.
Formula (I): Iron content rate (atomic%) = A _Fe / (A _C + A _O + A _Fe ) × 100
Formula (II): Coverage ratio (%) = {1- (iron content ratio of carrier) / (iron content ratio of magnetic particles alone)} × 100

  The average film thickness of each coating resin layer is preferably 0.1 μm or more and 10 μm or less, more preferably 0.1 μm or more and 3.0 μm or less, and particularly preferably 0.1 μm or more and 1.5 μm or less. When the average thickness of the coating resin layer is less than 0.1 μm, there may be a decrease in resistance due to peeling of the coating resin layer when used for a long time or it may be difficult to sufficiently control the pulverization of the carrier. On the other hand, when the average film thickness of the coating resin layer exceeds 10 μm, it may take time to reach the saturation charge amount.

The average thickness (μm) of the coating resin layer is such that the true specific gravity of the magnetic particles is ρ (dimensionless), the volume average particle size of the magnetic particles is d (μm), the average specific gravity of the coating resin layer is ρ _C , and magnetic When the total content of the coating resin layer with respect to 100 parts by weight of body particles is W _C (parts by weight), it can be determined as follows.
Average film thickness (μm) = [amount of coating resin per carrier (including all additives such as a conductive agent) / surface area per carrier] ÷ average specific gravity of coating resin layer = [4 / 3π · (d / 2) ³ · ρ · W _C ] / [4π · (d / 2) ² ] ÷ ρ _C
= (1/6) · (d · ρ · W _C / ρ _C )

-Magnetic particles-
The magnetic particles of the embodiment preferably satisfy the following formula (1).
Formula (1): 2.0 <= A / a <= 7.0
[Wherein, in formula (1), A represents the BET specific surface area (unit: m ² / g) of the magnetic particles, a represents the spherical equivalent specific surface area (unit: m ² / g) of the magnetic particles, The spherical equivalent surface area a is defined as a = 6 / (d, where d (unit: μm) is the volume average particle diameter of the magnetic particles and ρ (unit: dimensionless) is the true specific gravity of the magnetic particles. Xρ). ]

The BET specific surface area is a specific surface area per unit mass determined by the BET method, and the spherical equivalent surface area a is a specific surface area per unit mass when the magnetic particles are assumed to be completely smooth spheres.
Therefore, the value of (A / a) represents unevenness on the surface of the magnetic particles. That is, the larger the value of (A / a), the greater the irregularities on the surface of the magnetic particles, and the smaller the value of (A / a), the smoother the surface of the magnetic particles.

  With this configuration, in the electrophotographic carrier of the embodiment, the coating resin layer can be made more difficult to peel.

  By adding moderate irregularities to the surface of the magnetic particles, the surface area of the magnetic particles is increased, and at the same time, the resin is infiltrated into the recesses on the surface of the magnetic particles, and the effect of adding a trap between the coating resin layer and the magnetic particles surface, That is, the anchor effect can be imparted to the coating resin layer. Thereby, it becomes possible to suppress peeling of the coating resin layer.

  When (A / a) of the magnetic particles is smaller than 2.0, the coating resin layer and the magnetic particles are caught, that is, the anchor effect on the resin due to the surface irregularities of the magnetic particles is small. The coating resin layer is peeled off, and the peeled resin powder (carrier resin peeling powder) is charged with a polarity opposite to that of the toner, so that it may be developed on the background portion of the latent image on the photoreceptor.

  On the other hand, if (A / a) of the magnetic particles is larger than 7.0, pores exist in the magnetic particles, and the resin penetrates into the magnetic particles. When the particles are exposed, the carrier resistance becomes too low, and the developing electric field is injected, carrier spent may be generated.

The BET specific surface area A (m ² / g) of the magnetic particles in the embodiment is measured by the following method.
Using a BET specific surface area meter (SA3100, manufactured by Beckman Coulter, Inc.) as a measuring device, 0.1 g of a porous silicon nitride fine powder as a measurement sample is precisely weighed and placed in a sample tube, and then degassed. A numerical value obtained by automatic measurement by the point method is defined as a BET specific surface area A of the magnetic particles.

The spherical equivalent specific surface area a (m ² / g) of the magnetic particles is represented by the following formula (2).
Formula (2): a = 6 / (d × ρ)
Here, d represents the volume average particle diameter (unit: μm) of the magnetic particles, and ρ represents the true specific gravity (unit: dimensionless) of the magnetic particles.

The spherical equivalent surface area a is a specific surface area per unit mass when the magnetic particles are assumed to be perfectly smooth spheres, and can be derived as follows.
When the volume average particle diameter of the magnetic particles is d (μm), the surface area S (m ² ) and the volume V (m ² ) of one magnetic particle are represented by the following formulas (3) and (4). .
Formula (3): S = 4π × {(d / 2) × 10 ⁻⁶ } ²
Formula (4): V = (4/3) × π × {(d / 2) × 10 ⁻⁶ } ³
Further, when the true specific gravity of the magnetic particles is ρ (dimensionalless), the density of the magnetic particles is represented by ρ × 10 ⁶ (g / m ³ ), and the mass M (g) of one magnetic particle is as follows. It is represented by Formula (5).
Formula (5): M = V × ρ × 10 ⁶ = (1/6) πρd ³ × 10 ⁻¹²
Therefore, as described above, since the spherical equivalent surface area a is a surface area per unit mass, the above formula (2) is derived as in the following formula (6).
Formula (6): a = S / M = 6 / (d × ρ)

  The volume average particle size d of the magnetic particles is measured using a laser diffraction / scattering particle size distribution analyzer (LS Particle Size Analyzer: LS13 320, manufactured by BECKMAN COULTER). For the particle size range (channel) obtained by dividing the obtained particle size distribution, the volume cumulative distribution is subtracted from the small particle size side, and the particle size at 50% accumulation is defined as the volume average particle size d.

In addition, the true specific gravity ρ of the magnetic particles is measured using a Lechatelier specific gravity bottle in accordance with JIS-K-0061 5-2-1. The operation is as follows.
(1) About 250 ml of ethyl alcohol is put into a Lechatelier specific gravity bottle and adjusted so that the meniscus is at the position of the scale.
(2) The specific gravity bottle is immersed in a constant temperature water bath, and when the liquid temperature reaches 20.0 ± 0.2 ° C., the position of the meniscus is accurately read with the scale of the specific gravity bottle. (Accuracy 0.025ml)
(3) About 100 g of a sample is weighed and its mass is defined as W (g).
(4) Put the weighed sample in a specific gravity bottle to remove bubbles.
(5) The specific gravity bottle is immersed in a constant temperature water bath, and when the liquid temperature becomes 20.0 ± 0.2 ° C., the position of the meniscus is accurately read with the scale of the specific gravity bottle. (Accuracy 0.025ml)
(6) The true specific gravity is calculated by the following formula.
D = W / (L2-L1)
ρ = D / 0.9982
In the above formula, D is the density of the sample (20 ° C.) (g / cm ³ ), ρ is the true specific gravity of the sample (20 ° C.), W is the apparent mass (g) of the sample, and L1 is the sample in a specific gravity bottle. The previous meniscus reading (20 ° C.) (ml), L2 is the meniscus reading after placing the sample in the density bottle (20 ° C.) (ml), 0.9982 is the density of water at 20 ° C. (g / cm ³ ).

  The magnetic particles used in the embodiment are not particularly limited as long as the above-described conditions are satisfied. For example, magnetic metals such as iron, steel, nickel, and cobalt; magnetic oxides such as ferrite and magnetite; A glass bead etc. can be mentioned. In particular, as magnetic particles suitably used in the embodiment, ferrite particles are preferable because surface uniformity is easy and chargeability is stable.

  The magnetic particles are formed by granulation and sintering, but are preferably finely pulverized as a pretreatment. The pulverization method is not particularly limited, and pulverization can be performed according to a known pulverization method. Specific examples include a mortar, a ball mill, and a jet mill. Although the final pulverized state in the pretreatment varies depending on the material and the like, the volume average particle size is preferably 2 μm or more and 10 μm or less. If it is less than 2 μm, the desired particle size may not be obtained. If it exceeds 10 μm, the particle size may become too large, or the circularity may become small.

  In addition, the sintering temperature is preferably kept lower than in the conventional case. Specifically, although it varies depending on the material used, 500 ° C. or more and 1200 ° C. or less is preferable, and 600 ° C. or more and 1000 ° C. or less is more preferable. . If the sintering temperature is less than 500 ° C., the magnetic force required for the carrier may not be obtained. If the sintering temperature exceeds 1200 ° C., the crystal growth is fast and the internal structure tends to become non-uniform, causing cracks and cracks. Easy to enter.

  In order to keep the sintering temperature low, in the sintering process, it is preferable to perform preliminary sintering stepwise. Therefore, it is preferable to increase the time required for the entire sintering.

  The volume average particle size of the magnetic particles is preferably 10 μm to 100 μm, more preferably 20 μm to 60 μm. When the volume average particle diameter of the magnetic particles is less than 10 μm, when used in an electrophotographic developer, the adhesion between the toner and the carrier is increased, and the toner development amount may be reduced. On the other hand, if it exceeds 100 μm, the magnetic brush becomes rough, and it may be difficult to form a fine image.

  As for the magnetic force of the magnetic particles, the saturation magnetization at 1000 oersted is preferably 50 emu / g or more, more preferably 60 emu / g or more. If the saturation magnetization is weaker than 50 emu / g, the carrier may be developed on the photoreceptor together with the toner.

  As a device for measuring magnetic properties, a vibrating sample type magnetic measuring device VSMP10-15 (manufactured by Toei Industry Co., Ltd.) is used. The measurement sample is packed in a cell having an inner diameter of 7 mm and a height of 5 mm and set in the apparatus. The measurement applies an applied magnetic field and sweeps up to 1000 oersted. Next, the applied magnetic field is decreased to create a hysteresis curve on the recording paper. Saturation magnetization, residual magnetization, and coercive force are obtained from the curve data. In an embodiment, saturation magnetization refers to magnetization measured in a 1000 oersted magnetic field.

The volume electric resistance (volume resistivity) of the magnetic particles is preferably in the range of 10 ⁵ Ω · cm to 10 ^9.5 Ω · cm, and preferably in the range of 10 ⁷ Ω · cm to 10 ⁹ Ω · cm. It is more preferable that If the volume electric resistance is less than 10 ⁵ Ω · cm, when the toner concentration in the developer decreases due to repeated copying, charges may be injected into the carrier and the carrier itself may be developed. On the other hand, if the volume electric resistance is greater than 10 ^9.5 Ω · cm, the image quality may be adversely affected, such as the prominent edge effect or pseudo contour.

The volume electric resistance (Ω · cm) of the magnetic particles is measured as follows. The measurement environment is a temperature of 20 ° C. and a humidity of 50% RH.
A measurement object is placed flat on the surface of a circular jig having a 20 cm ² electrode plate so as to have a thickness of about 1 to 3 mm to form a layer. A 20 cm ² electrode plate similar to the above is placed thereon, and the layer is sandwiched. In order to eliminate gaps between objects to be measured, a thickness (cm) of the layer is measured after a load of 4 kg is applied on the electrode plate placed on the layer. Both electrodes above and below the layer are connected to an electrometer and a high voltage power generator. By applying a high voltage so that the electric field is 10 ^3.8 V / cm to both electrodes, and reading the current value (A) flowing at this time, the volume electric resistance (Ω · cm) of the measurement object is calculated. To do. The calculation formula of the volume electrical resistance (Ω · cm) of the measurement object is as shown in the following formula.
Formula: R = E × 20 / (I−I ₀ ) / L

In the above formula, R is the volume electric resistance (Ω · cm) of the measurement object, E is the applied voltage (V), I is the current value (A), I ₀ is the current value (A) at the applied voltage of 0 V, and L is Each layer thickness (cm) is expressed. A coefficient of 20 represents the area (cm ² ) of the electrode plate.

  In particular, in a carrier whose resistance is adjusted by containing a conductive agent in the coating resin layer, further significant charge leakage occurs, so it is more important to suppress this leakage. Further, when the toner contains a crystalline resin, the generated charge amount of the toner is reduced, so that it is necessary to further suppress charge leakage. Therefore, in such a case, it is particularly effective to use the carrier of the embodiment having good charge characteristics on the surface of the coating resin layer.

  In particular, when carbon black or the like is used as a conductive agent in the carrier, when the coating resin layer is peeled off, black carrier resin peeling powder is generated, which is recognized as fogging. Even if a transparent or white conductive agent is used, the carrier resin peels off to cause contamination inside the machine, which can contaminate the exposed area and prevent the formation of a fine latent image, or contaminates the charger to uniformly charge the photoconductor. Cannot produce white spots or black spots. Therefore, in such a case, it is particularly effective to use the carrier of the embodiment in which the coating resin layer is difficult to peel off.

  Further, a developing system in which a two-component developer composed of toner and carrier is contained in a developing machine, and a part of the two-component developer is discharged from the developing machine periodically or continuously, while supplying toner and carrier to the developing machine. In particular, in the image forming method using the method (hereinafter sometimes referred to as trickle method), a new carrier is supplied into the developing machine according to toner consumption. If used, carrier resin peeling powder will accumulate in the developing machine. In this case, the carrier resin peeling powder containing the conductive agent adheres to the toner in the developer, whereby a developing electric field is injected into the toner through the carrier resin peeling powder. Then, the toner into which the electric field is injected is developed as a fog on the background portion on the photoreceptor. Therefore, even in such a case, it is very important to suppress peeling of the coating resin layer, and it is particularly effective to use the carrier of the embodiment.

-Conductive agent-
The coating resin layer preferably contains a conductive agent as necessary for the purpose of controlling resistance.
Specific examples of the conductive agent include metal particles such as gold, silver, and copper; carbon black; ketjen black; acetylene black; semiconductive oxide particles such as titanium oxide and zinc oxide; titanium oxide, zinc oxide, and sulfuric acid. And particles having a surface of barium, aluminum borate, potassium titanate powder or the like covered with tin oxide, carbon black, metal, or the like.
These may be used individually by 1 type and may use 2 or more types together.

As the conductive agent, carbon black particles are preferable in terms of good production stability, cost, conductivity and the like.
Although there is no restriction | limiting in particular as a kind of carbon black, The carbon black whose DBP oil absorption is about 50-250 ml / 100g is excellent in manufacturing stability, and preferable.

  The volume average particle diameter of the conductive agent is preferably 0.5 μm or less, more preferably 0.05 μm or more and 0.5 μm or less, and still more preferably 0.05 μm or more and 0.35 μm or less. If the volume average particle size is larger than 0.5 μm, the conductive agent tends to fall off from the coating resin layer, and stable chargeability may not be obtained.

  The volume average particle diameter of the conductive agent is measured using a laser diffraction particle size distribution measuring device (LA-700: manufactured by Horiba, Ltd.).

  As a measurement method, 2 g of a measurement sample was added to a surfactant, preferably 50 ml of a 5% aqueous solution of sodium alkylbenzenesulfonate, and dispersed for 2 minutes with an ultrasonic disperser (1,000 Hz) to prepare a sample. taking measurement.

  The obtained volume average particle diameter for each channel is accumulated from the smaller volume average particle diameter, and the place where the accumulation reaches 50% is defined as the volume average particle diameter.

The volume electric resistance of the conductive agent is preferably from 10 ¹ Ω · cm to 10 ¹¹ Ω · cm, and more preferably from 10 ³ Ω · cm to 10 ⁹ Ω · cm.
The volume electrical resistance of the conductive agent is measured in the same manner as the volume electrical resistance of the magnetic particles.

  The content of the conductive agent is preferably 1 part by weight or more and 50 parts by weight or less, and more preferably 3 parts by weight or more and 20 parts by weight or less with respect to the entire coating resin layer. When the content is more than 50 parts by weight, the carrier resistance is lowered, and the image may be lost due to carrier adhesion to the developed image. On the other hand, if the content is less than 1 part by weight, the carrier is insulated, and it becomes difficult for the carrier to work as a developing electrode during development, and the edge effect appears particularly when a solid image is formed. May be inferior.

  In addition, the coating resin layer may contain other resin particles. Examples of the resin particles include thermoplastic resin particles and thermosetting resin particles. Among these, a thermosetting resin is preferable from the viewpoint of relatively easily increasing the hardness, and resin particles of a nitrogen-containing resin containing a nitrogen atom are preferable from the viewpoint of imparting negative chargeability to the toner. In addition, these resin particles may be used individually by 1 type, and may use 2 or more types together.

  The volume average particle size of the resin particles is preferably, for example, from 0.1 μm to 2.0 μm, and more preferably from 0.2 μm to 1.0 μm. If the average particle size of the resin particles is less than 0.1 μm, the dispersibility of the resin particles in the coating resin layer may be extremely deteriorated. On the other hand, if the average particle size exceeds 2.0 μm, the resin particles are dispersed from the coating resin layer. Dropout easily occurs and the original effect may not be exhibited.

  The volume average particle diameter of the resin particles can be obtained by performing the same measurement as the volume average particle diameter of the conductive agent.

The method for forming the coating resin layer on the surface of the magnetic particles is not particularly limited, and examples thereof include a method using a coating resin layer forming liquid containing a conductive agent and a coating resin in a solvent.
For example, a dipping method in which magnetic particles are immersed in a coating resin layer forming solution, a spray method in which a coating resin layer forming solution is sprayed on the surface of the magnetic particles, or a coating resin in a state where the magnetic particles are suspended by flowing air Examples thereof include a kneader coater method in which the solvent is removed by mixing with a layer forming solution. Among these, the kneader coater method is preferable in the embodiment.

  The solvent used in the coating resin layer forming liquid is not particularly limited as long as it can dissolve only the resin, and can be selected from known solvents. Specific examples include aromatic hydrocarbons such as toluene and xylene; ketones such as acetone and methyl ethyl ketone; ethers such as tetrahydrofuran and dioxane;

  When resin particles are dispersed in the coating resin layer, the resin particles are uniformly dispersed in the thickness direction and the tangential direction of the carrier surface. However, it is possible to always maintain the same surface formation as when it is not used, and to maintain a good charge imparting ability for the toner over a long period of time.

  In the case where the conductive agent is dispersed in the coating resin layer, the conductive agent is uniformly dispersed in the thickness direction and the tangential direction of the carrier surface. Even if it is worn, it is possible to always maintain the same surface formation as when not in use, and to prevent carrier deterioration for a long time.

  In addition, when the resin particle and the electrically conductive agent are disperse | distributed to the coating resin layer, the above-mentioned effect can be show | played simultaneously.

<Characteristics of carrier>
The volume average particle diameter of the carrier is preferably 15 μm or more and 50 μm or less, and more preferably 25 μm or more and 40 μm or less. When the volume average particle diameter of the carrier is smaller than 15 μm, the carrier contamination may be deteriorated. When the volume average particle diameter of the carrier is larger than 50 μm, toner deterioration due to stirring may become remarkable.

  The volume average particle diameter of the carrier is measured using a laser diffraction / scattering particle size distribution analyzer (LS Particle Size Analyzer: LS13 320, manufactured by BECKMAN COULTER).

  For the particle size range (channel) obtained by dividing the obtained particle size distribution, the volume cumulative distribution is subtracted from the small particle size side, and the particle size at 50% cumulative is taken as the volume average particle size.

  Further, the shape factor SF1 of the carrier is preferably 100 or more and 145 or less. This is to achieve both high image quality and developer agitation efficiency.

The carrier shape factor SF1 means a value obtained by the following formula (III).
Formula (III): SF1 = 100π × (ML) ² / (4 × A)
Here, ML is the maximum length of the carrier particles, and A is the projected area of the carrier particles. The maximum length and projected area of the carrier particles are determined by observing the carrier particles sampled on the slide glass with an optical microscope and importing them into an image analyzer (LUZEX III, manufactured by NIRECO) through a video camera for image analysis. Is obtained by The number of samplings at this time is 100 or more, and the shape factor shown in Formula (III) is obtained using the average value.

The saturation magnetization of the carrier is preferably 40 emu / g or more, and more preferably 50 emu / g or more.
As a device for measuring magnetic properties, a vibrating sample type magnetic measuring device VSMP10-15 (manufactured by Toei Kogyo Co., Ltd.) is used. The measurement sample is packed in a cell having an inner diameter of 7 mm and a height of 5 mm and set in the apparatus. The measurement applies an applied magnetic field and sweeps up to 1000 oersted. Next, the applied magnetic field is decreased to create a hysteresis curve on the recording paper. Saturation magnetization, residual magnetization, and coercive force are obtained from the curve data. In an embodiment, saturation magnetization refers to magnetization measured in a 1000 oersted magnetic field.

The volume electric resistance of the carrier is preferably controlled in the range of 1 × 10 ⁷ Ω · cm to 1 × 10 ¹⁵ Ω · cm, preferably 1 × 10 ⁸ Ω · cm to 1 × 10 ¹⁴ Ω · cm. The range is more preferable, and the range of 1 × 10 ⁸ Ω · cm to 1 × 10 ¹³ Ω · cm is particularly preferable.
When the volume electrical resistance of the carrier exceeds 1 × 10 ¹⁵ Ω · cm, the resistance becomes high and it becomes difficult to work as a developing electrode at the time of development. There is a case. On the other hand, if it is less than 1 × 10 ⁷ Ω · cm, the resistance becomes low, so that when the toner concentration in the developer is lowered, charges are injected from the developing roll into the carrier, and the carrier itself is developed. It may be easier.
The volume electric resistance of the carrier is measured in the same manner as the volume electric resistance of the magnetic particles.

[Electrophotographic developer]
The electrophotographic developer according to the embodiment includes at least a toner and the electrophotographic carrier according to the embodiment. The electrophotographic developer of the embodiment (hereinafter sometimes abbreviated as developer) will be described below.

  There is no restriction | limiting in particular as a toner, A well-known toner can be used, For example, the coloring toner which has binder resin and a coloring agent can be mentioned. In addition, an infrared absorbing toner having a binder resin and an infrared absorber can be used.

  Binder resins include monoolefins such as ethylene, propylene, butylene, and isoprene; vinyl esters such as vinyl acetate, vinyl propionate, vinyl benzoate, and vinyl butyrate; methyl acrylate, phenyl acrylate, octyl acrylate, and methacrylic acid. Α-methylene aliphatic monocarboxylic esters such as methyl, ethyl methacrylate, butyl methacrylate, dodecyl methacrylate; vinyl ethers such as vinyl methyl ether, vinyl ethyl ether, vinyl butyl ether; vinyl methyl ketone, vinyl hexyl ketone, vinyl Homopolymers or copolymers of vinyl ketones such as isopropenyl ketone; Among these, particularly typical binder resins include polystyrene, styrene-alkyl acrylate copolymer, styrene-butadiene copolymer, styrene-maleic anhydride copolymer, polystyrene, polypropylene, and the like. Further examples include polyester, polyurethane, epoxy resin, silicone resin, polyamide, modified rosin and the like.

The weight average molecular weight Mw of the binder resin is preferably in the range of 80,000 to 200,000, more preferably in the range of 140,000 to 190,000, and particularly preferably in the range of 150,000 to 180,000.
By setting it within the above range, it is possible to suppress the deterioration of the toner even when a large stress is applied to the developer as in a high speed machine.

  In the embodiment, the glass transition temperature of the binder resin is measured using a differential scanning calorimeter (DSC) when the temperature is measured from room temperature to 150 ° C. at a heating rate of 10 ° C. per minute. It can be determined as the onset temperature of the input compensation differential scanning calorimetry shown in JIS K-7121.

  The colorant is not particularly limited. For example, carbon black, aniline blue, calcoil blue, chrome yellow, ultramarine blue, deyupon oil red, quinoline yellow, methylene blue chloride, phthalocyanine blue, malachite green oxalate, lamp black, Rose Bengal, C.I. I. Pigment red 48: 1, C.I. I. Pigment red 122, C.I. I. Pigment red 57: 1, C.I. I. Pigment yellow 97, C.I. I. Pigment yellow 12, C.I. I. Pigment blue 15: 1, pigment blue 15: 3, and the like.

  Further, the toner can contain a charge control agent as required. At that time, a colorless or light-color charge control agent that does not affect the color tone is preferable, particularly when used for a color toner or the like. As the charge control agent, known ones can be used, but it is preferable to use an azo metal complex; a metal complex or metal salt of salicylic acid or alkylsalicylic acid; The toner can also contain other known components such as low molecular weight propylene, low molecular weight polyethylene, and an anti-offset agent such as wax.

  Examples of the wax include the following. Paraffin wax and derivatives thereof, montan wax and derivatives thereof, microcrystalline wax and derivatives thereof, Fischer-Tropsch wax and derivatives thereof, polyolefin wax and derivatives thereof, and the like. Derivatives include oxides, polymers with vinyl monomers, and graft modified products. In addition, alcohols, fatty acids, plant waxes, animal waxes, mineral waxes, ester waxes, acid amides, and the like can be used.

The toner may contain inorganic oxide particles inside. Examples of the inorganic oxide particles include SiO ₂ , TiO ₂ , Al ₂ O ₃ , CuO, ZnO, SnO ₂ , CeO ₂ , Fe ₂ O ₃ , MgO, BaO, CaO, K ₂ O, Na ₂ O, and ZrO _2. , it can be exemplified _{CaO · SiO 2, K 2 O} · (TiO 2) n, Al 2 O 3 · 2SiO 2, CaCO 3, MgCO 3, BaSO 4, MgSO 4 , and the like. Of these, silica particles and titania particles are particularly preferable.
The surface of the inorganic oxide particles does not necessarily need to be hydrophobized in advance, but may be hydrophobized. When the hydrophobic treatment is performed, even when some of the internal inorganic particles are exposed on the toner surface, it is possible to effectively reduce the environmental dependency of charging and carrier contamination.

  The hydrophobic treatment can be performed by immersing an inorganic oxide in a hydrophobic treatment agent. Although there is no restriction | limiting in particular as a hydrophobization processing agent, For example, a silane coupling agent, a silicone oil, a titanate coupling agent, an aluminum coupling agent etc. are mentioned. These may be used individually by 1 type and may use 2 or more types together. Of these, silane coupling agents are preferred.

  As the silane coupling agent, for example, any of chlorosilane, alkoxysilane, silazane, and a special silylating agent can be used. Specifically, methyltrichlorosilane, dimethyldichlorosilane, trimethylchlorosilane, phenyltrichlorosilane, diphenyldichlorosilane, tetramethoxysilane, methyltrimethoxysilane, dimethyldimethoxysilane, phenyltrimethoxysilane, diphenyldimethoxysilane, tetraethoxysilane, Methyltriethoxysilane, dimethyldiethoxysilane, phenyltriethoxysilane, diphenyldiethoxysilane, isobutyltriethoxysilane, decyltrimethoxysilane, hexamethyldisilazane, N, O- (bistrimethylsilyl) acetamide, N, N- ( Trimethylsilyl) urea, tert-butyldimethylchlorosilane, vinyltrichlorosilane, vinyltrimethoxysilane, vinyltriethoxysilane , Γ-methacryloxypyrroletrimethoxysilane, β- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, γ-mercapto Examples thereof include propyltrimethoxysilane and γ-chloropropyltrimethoxysilane.

  The amount of the hydrophobizing agent varies depending on the kind of the inorganic oxide particles and cannot be defined unconditionally, but is usually preferably about 5 to 50 parts by weight with respect to 100 parts by weight of the inorganic oxide particles.

In the toner, inorganic oxide particles can be added to the toner surface. Inorganic oxide particles added to the toner surface include SiO ₂ , TiO ₂ , Al ₂ O ₃ , CuO, ZnO, SnO ₂ , CeO ₂ , Fe ₂ O ₃ , MgO, BaO, CaO, K ₂ O, Na Examples include ₂ O, ZrO ₂ , CaO · SiO ₂ , K ₂ O · (TiO ₂ ) n, Al ₂ O ₃ · 2SiO ₂ , CaCO ₃ , MgCO ₃ , BaSO ₄ , MgSO _{4, and the} like. Of these, silica particles and titania particles are particularly preferable.

The amount of inorganic oxide particles added as an external additive to the total amount of toner is preferably 2 parts by weight or more and 10 parts by weight or less, more preferably 3 parts by weight or more and 9 parts by weight or less, and 3.5 parts by weight or more and 8 parts by weight or less. Is particularly preferred.
By setting it within the above range, good fluidity can be secured in the developing device, and therefore, there is an effect of reducing stress applied to the developer.

  It is desirable that the surface of the inorganic oxide particles is previously hydrophobized. In addition to improving the powder fluidity of the toner, this hydrophobic treatment can effectively suppress the environmental dependency of charging and carrier contamination.

  The hydrophobic treatment can be performed by immersing an inorganic oxide in a hydrophobic treatment agent, as described above. Although there is no restriction | limiting in particular as a hydrophobization processing agent, For example, a silane coupling agent, a silicone oil, a titanate coupling agent, an aluminum coupling agent etc. are mentioned. These may be used individually by 1 type and may use 2 or more types together. Of these, silane coupling agents are preferred.

  As the silane coupling agent, for example, any one of chlorosilane, alkoxysilane, silazane, and a special silylating agent can be used. Specifically, methyltrichlorosilane, dimethyldichlorosilane, trimethylchlorosilane, phenyltrichlorosilane, diphenyldichlorosilane, tetramethoxysilane, methyltrimethoxysilane, dimethyldimethoxysilane, phenyltrimethoxysilane, diphenyldimethoxysilane, tetraethoxysilane, methyl Triethoxysilane, dimethyldiethoxysilane, phenyltriethoxysilane, diphenyldiethoxysilane, isobutyltriethoxysilane, decyltrimethoxysilane, hexamethyldisilazane, N, O- (bistrimethylsilyl) acetamide, N, N- (trimethylsilyl) ) Urea, tert-butyldimethylchlorosilane, vinyltrichlorosilane, vinyltrimethoxysilane, vinyltriethoxysila , Γ-methacryloxypropyl trimethoxysilane, β- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, γ-mercaptopropyl Examples include trimethoxysilane and γ-chloropropyltrimethoxysilane.

  The amount of the hydrophobizing agent varies depending on the kind of the inorganic oxide particles and cannot be defined unconditionally as described above, but is usually about 5 to 50 parts by weight with respect to 100 parts by weight of the inorganic oxide particles. Is preferred.

  Regarding the particle size distribution of the toner, toner particles having a particle size of 4 μm or less are preferably 6 to 25% by number, more preferably 6 to 16% by number of the total number of toner particles. If the toner particles having a particle diameter of 4 μm or less are less than 6% by number, there are few particles that contribute to fine dot reproducibility and graininess, and they are selectively consumed because they are effective particle diameters. In this case, the toner having a particle diameter that hardly contributes to the development stays in the developing machine, so that the image quality may gradually deteriorate. On the other hand, if it exceeds 25% by number, the fluidity of the toner is deteriorated, so that the developer transportability is lowered, and there is a concern that the developability is adversely affected.

  The toner particles having a particle diameter of 16 μm or more are preferably 1.0% by volume or less. If it exceeds 1.0% by volume, not only will fine line reproducibility and gradation be adversely affected, but also during transfer, coarse toner particles of 16 μm or more will be present in the toner layer, so Since it works to hinder the electroadhesion state, there is a risk of lowering transfer efficiency and eventually image quality.

  Further, the volume average particle diameter of the toner is preferably 5 to 9 μm, and in order to reproduce high image quality, it is desirable that the toner satisfies both the preferable range of the particle size distribution described above. When the volume average particle size is less than 5 μm, not only the fluidity of the toner is deteriorated, but also it becomes difficult to give sufficient chargeability from the carrier, so fogging to the background portion is likely to occur and density reproducibility is liable to be lowered. It may become. When the volume average particle diameter exceeds 9 μm, the above-mentioned carrier characteristics cannot be sufficiently exhibited, and the effect of improving the reproducibility, gradation and graininess of fine dots may be poor.

  Therefore, by having the above-described toner particle size distribution and volume average particle size, the image area of photographs, paintings, pamphlets, etc. has a large image area, and even in the case of repeated copying of a document having a density gradation, it can be used for fine latent image dots. , Faithful reproducibility can be expected.

  The particle size distribution and volume average particle size of the toner will be described later.

  As a method for producing the toner, generally used kneading and pulverizing methods, wet granulation methods, and the like can be used. Here, as the wet granulation method, suspension polymerization method, emulsion polymerization method, emulsion polymerization aggregation method, soap-free emulsion polymerization method, non-aqueous dispersion polymerization method, in-situ polymerization method, interfacial polymerization method, emulsion dispersion granulation Method, agglomeration / unification method and the like can be used.

  In order to produce the toner of the embodiment by the kneading and pulverization method, the binder resin and, if necessary, the colorant and other additives are sufficiently mixed by a mixer such as a Henschel mixer, a ball mill, etc. In addition, while melting and kneading using a thermal kneader such as an extruder to make the resins compatible with each other, an infrared absorber, an antioxidant, etc. are dispersed or dissolved, and after cooling and solidification, the toner is crushed and classified. Obtainable.

When toner particles are produced by a wet granulation method, the shape factor of the toner particles is preferably in the range of 110-135.
Here, the shape factor of the toner particles is obtained in the same manner as the shape factor SF1 of the carrier.

  In the developer of the exemplary embodiment, the toner / carrier mixing weight ratio is preferably 0.01 to 0.3 and more preferably 0.03 to 0.2.

  The developer of the embodiment can be applied not only as a developer stored in advance in a developing means (developer storage container) but also as a supply developer used in, for example, a trickle developing system. .

[Electrophotographic developer cartridge, image forming apparatus, process cartridge]
Next, the electrophotographic developer cartridge of the embodiment (hereinafter sometimes abbreviated as “cartridge”) will be described. The cartridge according to the embodiment is detachable from the image forming apparatus, and at least for developing the electrostatic latent image formed on the surface of the electrostatic latent image holding member to supply to a developing unit that forms a toner image. A developer is accommodated, and the developer is the developer of the embodiment described above.

  Accordingly, in the image forming apparatus having a configuration in which the cartridge can be attached and detached, by using the cartridge of the embodiment in which the developer of the embodiment is housed, the environmental dependency such as temperature and humidity is small, and the coating resin The layer is difficult to peel off, and image formation can be performed stably over a long period of time.

  Here, the cartridge of the embodiment may be a cartridge that stores the developer of the embodiment, particularly when used in an image forming apparatus of a trickle developing system, or a cartridge that stores toner alone and the cartridge of the embodiment. It may be a separate body from the cartridge that houses the carrier alone.

  The image forming apparatus according to the embodiment includes an electrostatic latent image holding member, an electrostatic latent image forming unit that forms an electrostatic latent image on the surface of the electrostatic latent image holding member, and developing the electrostatic latent image with a developer. Development means for forming a toner image, transfer means for transferring the toner image to a recording medium, and fixing means for fixing the toner image on the recording medium. It is a photographic developer.

  Therefore, by using the image forming apparatus of the embodiment using the developer of the embodiment, the environmental dependency such as temperature and humidity is small, and the coating resin layer is difficult to peel off, and the image can be stably formed over a long period of time. Formation can be performed.

  The image forming apparatus according to the embodiment includes at least the electrostatic latent image holding member, the electrostatic latent image forming unit, the developing unit, the transfer unit, and the fixing unit as described above. Although there is no particular limitation, other cleaning means, static elimination means, and the like may be included as necessary.

  The developing means is housed in the developer containing container for containing the developer of the embodiment, the developer supplying means for supplying the developer to the developer containing container, and the developer containing container. A configuration including a developer discharging means for discharging at least a part of the developer, that is, a trickle developing method may be employed.

  Here, the developer (supplying developer) to be supplied to the developer storage container preferably has a toner / carrier mixing weight ratio of toner weight / carrier weight ≧ 2, more preferably the weight ratio is toner. Weight / carrier weight ≧ 3, more preferably toner weight / carrier weight ≧ 5.

  When such a trickle development method is used, if a resin-coated carrier from which the coating resin layer is easy to peel off is used, not only does the coating resin layer peel from the developer originally in the developer container, but also from the developer supply means. The coating resin layer in the developer that is supplied to the developer container as needed is also peeled off, and the influence of the carrier resin peeling powder is greater than when the trickle developing method is not used.

  However, if the image forming apparatus of the embodiment using the developer of the embodiment is used, the resin coating layer in the developer of the embodiment is difficult to peel off, and the above-described problem is hardly caused even when the trickle development method is used. Therefore, it is possible to stably form an image over a long period of time while maintaining charging characteristics.

  The process cartridge according to the embodiment stores the developer according to the embodiment, is detachable from the image forming apparatus, includes a developing unit, and is selected from an electrostatic latent image holding member, a charging unit, and a cleaning unit. It is characterized by providing at least one kind. In addition, the process cartridge according to the embodiment may include other members such as a static eliminating unit as necessary.

  Therefore, in the image forming apparatus having a configuration in which the process cartridge can be attached and detached, by using the process cartridge according to the embodiment, the coating resin layer is hardly peeled off while maintaining the charging characteristics, and the image can be stably formed over a long period of time. Formation can be performed.

  Hereinafter, an electrophotographic developer cartridge, an image forming apparatus, and a process cartridge according to an embodiment will be specifically described with reference to the drawings.

  FIG. 1 is a cross-sectional view schematically showing a basic configuration of a preferred embodiment (first embodiment) of an image forming apparatus. The image forming apparatus illustrated in FIG. 1 includes the cartridge according to the embodiment.

An image forming apparatus 10 shown in FIG. 1 includes an electrostatic latent image holding body 12, a charging unit 14, an electrostatic latent image forming unit 16, a developing unit 18, a transfer unit 20, a cleaning unit 22, a neutralizing unit 24, a fixing unit 26, A cartridge 28 is provided.
The developer stored in the developing unit 18 and the cartridge 28 is the developer of the embodiment.

  For convenience, FIG. 1 illustrates only a configuration including the developing unit 18 and the cartridge 28 each containing the developer according to the embodiment. However, for example, in the case of a color image forming apparatus, the image forming apparatus includes It is also possible to adopt a configuration including a corresponding number of developing means 18 and cartridges 28.

  The image forming apparatus shown in FIG. 1 is an image forming apparatus having a configuration in which a cartridge 28 can be attached and detached. The cartridge 28 is connected to the developing means 18 through a developer supply pipe 30. Therefore, when image formation is performed, the developer of the embodiment accommodated in the cartridge 28 is supplied to the developing means 18 through the developer supply rod 30 so that the development of the embodiment can be performed over a long period of time. An image using the agent can be formed. Further, when the amount of developer stored in the cartridge 28 is reduced, the cartridge 28 can be replaced.

  Around the electrostatic latent image holding body 12, a charging means 14 for uniformly charging the surface of the electrostatic latent image holding body 12 in order along the rotation direction (arrow A direction) of the electrostatic latent image holding body 12, an image An electrostatic latent image forming unit 16 that forms an electrostatic latent image on the surface of the electrostatic latent image holding body 12 according to information, a developing unit 18 that supplies the developer of the embodiment to the formed electrostatic latent image, The drum-shaped transfer means 20 that contacts the surface of the electrostatic latent image holding body 12 and can be driven to rotate in the direction of arrow B as the electrostatic latent image holding body 12 rotates in the direction of arrow A, and the electrostatic latent image holding body 12. A cleaning device 22 that abuts on the surface, and a static elimination means 24 that neutralizes the surface of the electrostatic latent image holding body 12 are disposed.

  A recording medium 50 transported in the direction of arrow C by a transport unit (not shown) from the opposite side to the direction of arrow C can be inserted between the electrostatic latent image holding body 12 and the transfer unit 20. A fixing unit 26 incorporating a heating source (not shown) is disposed on the side of the electrostatic latent image holding body 12 in the direction of arrow C. The fixing unit 26 is provided with a pressure contact portion 32. Further, the recording medium 50 that has passed between the electrostatic latent image holding member 12 and the transfer means 20 can be inserted through the pressure contact portion 32 in the direction of arrow C.

As the electrostatic latent image holding member 12, for example, a photosensitive member or a dielectric recording member can be used.
As the photoreceptor, for example, a photoreceptor having a single layer structure or a photoreceptor having a multilayer structure can be used. As the material of the photoconductor, an inorganic photoconductor such as selenium or amorphous silicon, an organic photoconductor, or the like can be considered.

  Examples of the charging means 14 include a contact charging device using a conductive or semiconductive roller, brush, film, rubber blade, etc., a non-contact type charging device such as corotron charging or scorotron charging using corona discharge, etc. Any known means can be used.

As the electrostatic latent image forming means 16, in addition to the exposure means, any conventionally known means capable of forming a signal capable of forming a toner image at a desired position on the surface of the recording medium can be used. .
As the exposure means, for example, a conventionally known exposure means such as a combination of a semiconductor laser and a scanning device, a laser scanning writing device comprising an optical system, or an LED head can be used. In order to realize a preferable mode of producing a uniform and high-resolution exposure image, it is preferable to use a laser scanning writing device or an LED head.

  Specifically, as the transfer unit 20, for example, a conductive or semiconductive roller, brush, film, rubber blade, or the like to which a voltage is applied is used, and the electrostatic latent image holding member 12 and the recording medium 50 are used. A charged toner particle is formed by corona charging the back surface of the recording medium 50 with a means for transferring a toner image composed of charged toner particles, a corotron charger using a corona discharge, or a scorotron charger. Conventionally known means such as a means for transferring a toner image comprising the above can be used.

  A secondary transfer unit can also be used as the transfer unit 20. That is, although not shown, the secondary transfer unit is a unit that transfers the toner image to the intermediate transfer member and then secondary-transfers the toner image from the intermediate transfer member to the recording medium 50.

  Examples of the cleaning unit 22 include a cleaning blade and a cleaning brush.

  Examples of the static eliminating unit 24 include a tungsten lamp and an LED.

As the fixing unit 26, for example, a heat fixing unit that fixes a toner image by heating and pressing such as a heating roll and a pressure roll, or an optical fixing unit that heats and fixes a toner image by light irradiation with a flash lamp or the like. Etc. are available.
The material forming the roll surface such as a heating roll or a pressure roll is preferably, for example, a material excellent in releasability with respect to the toner, silicon rubber, fluorine resin, or the like for the purpose of preventing the toner from adhering. At this time, it is desirable not to apply a releasable liquid such as silicone oil to both sides of the roll. The releasable liquid is effective for widening the fixing latitude, but since it is transferred to the recording medium to be fixed, stickiness is generated on the printed matter on which the image is formed, and the tape cannot be attached or the character is printed by magic. May cause problems such as being unable to write. This problem becomes more prominent when a film such as OHP is used as the recording medium. In addition, since it is difficult for the releasable liquid to make the surface of the fixed image smooth, the image transparency, which is particularly important when an OHP film is used as a recording medium, may be a factor that decreases. However, when the toner contains a wax (offset preventing agent), it exhibits a sufficient fixing latitude, so that a releasable liquid such as silicone oil applied to the fixing roll is not necessary.

  The recording medium 50 is not particularly limited, and conventionally known media such as plain paper and glossy paper can be used. A recording medium having a base material and an image receiving layer formed on the base material can also be used.

  Next, image formation using the image forming apparatus 10 will be described. First, as the electrostatic latent image holding body 12 rotates in the direction of arrow A, the surface of the electrostatic latent image holding body 12 is charged by the charging unit 14, and the electrostatic latent image holding body 12 surface is charged with the electrostatic latent image. An electrostatic latent image corresponding to the image information is formed by the image forming means 16, and the developing means 18 is formed on the surface of the electrostatic latent image holding body 12 on which the electrostatic latent image is formed according to the color information of the electrostatic latent image. A toner image is formed by supplying the developer of the embodiment.

  Next, the toner image formed on the surface of the electrostatic latent image holding body 12 is brought into contact with the electrostatic latent image holding body 12 and the transfer unit 20 as the electrostatic latent image holding body 12 rotates in the arrow A direction. Move to the department. At this time, the recording medium 50 is inserted through the contact portion in the direction of arrow C by a paper conveyance roll (not shown), and the electrostatic latent image is transferred by the voltage applied between the electrostatic latent image holder 12 and the transfer means 20. The toner image formed on the surface of the image carrier 12 is transferred to the surface of the recording medium 50 at the contact portion.

  The toner remaining on the surface of the electrostatic latent image holding body 12 after the toner image is transferred to the transfer unit 20 is removed by the cleaning blade of the cleaning unit 22 and the charge is removed by the charge removing unit 24.

  The recording medium 50 having the toner image transferred onto the surface in this way is conveyed to the pressure contact portion 32 of the fixing unit 26 and passes through the pressure contact portion 32 to be pressed by a built-in heating source (not shown). The surface of the section 32 is heated by the heated fixing means 26. At this time, an image is formed by fixing the toner image on the surface of the recording medium 50.

  FIG. 2 is a cross-sectional view schematically showing a basic configuration of another preferred embodiment (second embodiment) of the image forming apparatus. In the image forming apparatus shown in FIG. 2, the developer (supplying developer) according to the embodiment is appropriately supplied to the developer storage container in the developing means by the developer supply means, and is stored in the developer storage container. The trickle developing method is adopted in which at least a part of the developer is appropriately discharged by the developer discharging means.

  As shown in FIG. 2, the image forming apparatus 100 according to the embodiment includes an electrostatic latent image holder 110 that rotates clockwise as indicated by an arrow a, and an electrostatic latent image holder 110. Above, the charging means 120 which is provided relative to the electrostatic latent image holding body 110 and negatively charges the surface of the electrostatic latent image holding body 110, and the electrostatic latent image holding body 110 charged by the charging means 120. An electrostatic latent image forming unit 130 for forming an electrostatic latent image by writing an image to be formed with a developer (toner) on the surface thereof, and a downstream side of the electrostatic latent image forming unit 130, While the toner is attached to the electrostatic latent image formed by the latent image forming unit 130 to form a toner image on the surface of the electrostatic latent image holding member 110, the electrostatic latent image holding member 110 is in contact with the developing unit 140. While traveling in the direction indicated by the arrow b, the electrostatic latent image holder 1 The endless belt-shaped intermediate transfer belt 150 for transferring the toner image formed on the surface of 0 and the surface of the electrostatic latent image holding member 110 after the toner image is transferred to the intermediate transfer belt 150 are discharged to the surface. A neutralization unit 160 that makes it easy to remove the remaining transfer residual toner and a cleaning unit 170 that cleans the surface of the electrostatic latent image holding member 110 to remove the transfer residual toner are provided.

  The charging unit 120, the electrostatic latent image forming unit 130, the developing unit 140, the intermediate transfer belt 150, the neutralizing unit 160, and the cleaning unit 170 are arranged in a clockwise direction on the circumference surrounding the electrostatic latent image holding body 110. It is installed.

  The intermediate transfer belt 150 is tensioned and held from the inside by the stretching rollers 150A and 150B, the backup roller 150C, and the driving roller 150D, and is driven in the direction of the arrow b as the driving roller 150D rotates. At a position opposite to the electrostatic latent image holder 110 inside the intermediate transfer belt 150, the intermediate transfer belt 150 is positively charged, and the toner on the electrostatic latent image holder 110 is placed on the outer surface of the intermediate transfer belt 150. A primary transfer roller 151 that adsorbs the toner is provided. On the outer side below the intermediate transfer belt 150, the recording medium P is positively charged and pressed against the intermediate transfer belt 150, thereby transferring the toner image formed on the intermediate transfer belt 150 onto the recording medium P. A transfer roller 152 is provided to face the backup roller 150C.

  Below the intermediate transfer belt 150, a recording medium supply device 153 that supplies the recording medium P to the secondary transfer roller 152 and a recording medium P on which a toner image is formed on the secondary transfer roller 152 are conveyed. Fixing means 180 for fixing the toner image is provided.

  The recording medium supply device 153 includes a pair of conveying rollers 153A and a guide slope 153B that guides the recording medium P conveyed by the conveying rollers 153A toward the secondary transfer roller 152. On the other hand, the fixing unit 180 includes a fixing roller 181 that is a pair of heat rollers for fixing the toner image by heating and pressing the recording medium P on which the toner image has been transferred by the secondary transfer roller 152, and fixing. A conveyance conveyor 182 that conveys the recording medium P toward the roller 181.

  The recording medium P is conveyed in the direction indicated by the arrow c by the recording medium supply device 153, the secondary transfer roller 152, and the fixing unit 180.

  In the vicinity of the intermediate transfer belt 150, an intermediate transfer body cleaning unit 154 having a cleaning blade for removing toner remaining on the intermediate transfer belt 150 after the toner image is transferred to the recording medium P by the secondary transfer roller 152 is provided. It has been.

  Hereinafter, the developing unit 140 will be described in detail. The developing unit 140 is disposed in the developing region so as to face the electrostatic latent image holding member 110. For example, the developing unit 140 includes two-component developing including a toner charged to a negative (−) polarity and a carrier charged to a positive (+) polarity. A developer storage container 141 for storing the developer. The developer container 141 includes a developer container main body 141A and a developer container cover 141B that closes the upper end of the developer container main body 141A.

  The developer container main body 141A has a developing roll chamber 142A for storing the developing roll 142 therein, and is adjacent to the first stirring chamber 143A and the first stirring chamber 143A adjacent to the developing roll chamber 142A. 144A of 2nd stirring chambers. Further, a layer thickness regulating member 145 is provided in the developing roll chamber 142A for regulating the layer thickness of the developer on the surface of the developing roll 142 when the developer containing container cover 141B is attached to the developer containing container main body 141A. It has been.

  The first stirring chamber 143A and the second stirring chamber 144A are partitioned by a partition wall 141C. Although not shown, the first stirring chamber 143A and the second stirring chamber 144A are arranged in the longitudinal direction of the partition wall 141C (developing device). (Longitudinal direction) Communication portions are provided at both ends to communicate with each other, and the first stirring chamber 143A and the second stirring chamber 144A constitute a circulation stirring chamber (143A + 144A).

  The developing roll 142 is disposed in the developing roll chamber 142A so as to face the electrostatic latent image holding body 110. Although not shown, the developing roll 142 is provided with a sleeve outside a magnetic roll (fixed magnet) having magnetism. The developer in the first stirring chamber 143A is adsorbed on the surface of the developing roll 142 by the magnetic force of the magnetic roll and is transported to the developing area. Further, the roll axis of the developing roll 142 is rotatably supported by the developer container main body 141A. Here, the developing roll 142 and the electrostatic latent image holding body 110 rotate in the opposite directions, and the developer adsorbed on the surface of the developing roll 142 at the facing portion advances by the electrostatic latent image holding body 110. The sheet is conveyed to the development area from the same direction as the direction.

  A bias power supply (not shown) is connected to the sleeve of the developing roll 142 so that a predetermined developing bias is applied (in this embodiment, an alternating electric field is applied to the developing region. , Applying a bias in which the AC component (AC) is superimposed on the DC component (DC)).

  The first stirring chamber 143A and the second stirring chamber 144A are provided with a first stirring member 143 (stirring / conveying member) and a second stirring member 144 (stirring / conveying member) that transport the developer while stirring. The first agitating member 143 includes a first rotating shaft extending in the axial direction of the developing roll 142, and an agitating / conveying blade (protrusion) fixed in a spiral manner on the outer periphery of the rotating shaft. Similarly, the second stirring member 144 includes a second rotating shaft and a stirring conveyance blade (protrusion). The stirring member is rotatably supported by the developer container main body 141A. The first stirring member 143 and the second stirring member 144 are arranged such that the developer in the first stirring chamber 143A and the second stirring chamber 144A is conveyed in the opposite directions by rotation thereof. .

  One end of a developer supply unit 146 for appropriately supplying a supply developer including supply toner and a supply carrier to the second agitation chamber 144A is connected to one end side in the longitudinal direction of the second agitation chamber 144A. A developer cartridge 147 containing a supply developer is connected to the other end of the developer supply means 146. One end of the second stirring chamber 144A in the longitudinal direction is also connected to one end of a developer discharging means 148 for appropriately discharging the stored developer, and the other end of the developer discharging means 148 is connected to the other end of the developer discharging means 148. Although not shown, it is connected to a developer collecting container for collecting the discharged developer.

  As described above, the developing unit 140 appropriately supplies the developer for supply from the developer cartridge 147 through the developer supplying unit 146 to the developing unit 140 (second stirring chamber 144A), and the old developer is supplied to the developer discharging unit. A so-called trickle developing system that appropriately discharges from 148 (to prevent the developer charging performance from deteriorating and to extend the developer replacement interval, supply developer (trickle developer) is gradually supplied into the developing device. On the other hand, it is a developing method in which development is performed while discharging the deteriorated developer that is excessive (including many deteriorated carriers).

  In this embodiment, the configuration using the developer cartridge 147 that stores the supply developer according to the embodiment has been described as an example. However, the developer cartridge 147 includes a cartridge that stores the supply toner alone. The cartridge for separately storing the supply carrier according to the embodiment may be separated.

  Next, the cleaning unit 170 will be described in detail. The cleaning unit 170 includes a housing 171 and a cleaning blade 172 disposed so as to protrude from the housing 171. The cleaning blade 172 is a plate-like member extending in the extending direction of the rotation axis of the electrostatic latent image holding body 110, and is rotated in the rotation direction (arrow) from the transfer position by the primary transfer roller 151 in the electrostatic latent image holding body 110. a direction) A tip end portion (hereinafter referred to as an edge portion) is provided in pressure contact with the downstream side and the downstream side in the rotational direction from the position where the charge is removed by the charge removal means 160.

  The cleaning blade 172 is held on the electrostatic latent image holding body 110 without being transferred to the recording medium P by the primary transfer roller 151 by rotating the electrostatic latent image holding body 110 in a predetermined direction (direction of arrow a). Foreign matter such as untransferred residual toner and paper dust of the recording medium P is dammed and removed from the electrostatic latent image holding member 110.

  Further, a transport member 173 is disposed at the bottom of the housing 171, and toner particles (developer) removed by the cleaning blade 172 are developed on the downstream side of the transport direction of the transport member 173 in the housing 171 by the developing unit 140. One end of a supply conveying means 174 for supplying to is connected. The other end of the supply / conveyance unit 174 is connected to join the developer supply unit 146.

  As described above, the cleaning unit 170 transports the untransferred residual toner particles to the developing unit 140 (second stirring chamber 144A) through the supply transport unit 174 in accordance with the rotation of the transport member 173 provided at the bottom of the housing 171. Toner reclaim is employed in which the developer (toner) contained therein is stirred and conveyed for reuse.

  FIG. 3 is a cross-sectional view schematically showing a basic configuration of another preferred embodiment (third embodiment) of the image forming apparatus. The image forming apparatus shown in FIG. 3 includes the process cartridge according to the embodiment.

  An image forming apparatus 200 shown in FIG. 3 includes a process cartridge 210 detachably disposed in an image forming apparatus main body (not shown), an electrostatic latent image forming unit 216, a transfer unit 220, and a fixing unit 226. It has.

  The process cartridge 210 has an electrostatic latent image holding body 212 in a casing 211 provided with an opening 211A for forming an electrostatic latent image, and a charging unit 214, a developing unit 218, and a cleaning unit 222 around the electrostatic latent image holding member 212. These are combined and integrated by mounting rails (not shown). Note that the process cartridge 210 is not limited to this, and it is only necessary to include the developing unit 218 and at least one selected from the group consisting of the electrostatic latent image holding member 212, the charging unit 214, and the cleaning unit 222.

  On the other hand, the electrostatic latent image forming unit 216 is disposed at a position where an electrostatic latent image can be formed on the electrostatic latent image holding body 212 from the opening 211A of the casing 211 of the process cartridge 210. The transfer unit 220 is disposed at a position facing the electrostatic latent image holder 212.

  The individual details of the electrostatic latent image holding member 212, the charging unit 214, the electrostatic latent image forming unit 216, the developing unit 218, the transfer unit 220, the cleaning unit 222, the fixing unit 226, and the recording medium 250 are illustrated in FIG. The same as the electrostatic latent image holding body 12, the charging unit 14, the electrostatic latent image forming unit 16, the developing unit 18, the transfer unit 20, the cleaning unit 22, the fixing unit 26, and the recording medium 50 in the image forming apparatus 10 of FIG. .

  The image formation using the image forming apparatus 200 of FIG. 3 is the same as the image formation using the image forming apparatus 10 of FIG.

  Hereinafter, embodiments will be described in detail with reference to examples. However, the embodiments are not limited to the following examples.

(Measuring method of particle size and particle size distribution)
The toner particle size and particle size distribution measurement in the embodiment will be described. In the embodiment, when the particle to be measured is 2 μm or more, Coulter Multisizer-II type (manufactured by Beckman-Coulter) was used as the measuring apparatus, and ISOTON-II (manufactured by Beckman-Coulter) was used as the electrolyte.
As a measuring method, 0.5 to 50 mg of a measurement sample is added to 2 ml of a 5% aqueous solution of a surfactant, preferably sodium alkylbenzenesulfonate as a dispersant. This was added to 100 to 150 ml of the electrolytic solution.
The electrolyte in which the sample is suspended is subjected to a dispersion treatment with an ultrasonic disperser for about 1 minute, and the particle size distribution of particles of 2 to 60 μm is measured using the Coulter Multisizer-II type with an aperture diameter of 100 μm. The volume average distribution was determined. The number of particles to be measured was 50,000.

Further, the particle size distribution of the toner in the embodiment was determined by the following method. For the particle size range (channel) obtained by dividing the measured particle size distribution, draw the volume cumulative distribution from the smaller particle size, define the volume average particle size to be 16% cumulative as D16, and the volume average to be 50% cumulative The particle size is defined as D50v. Furthermore, the volume average particle diameter that is 84% cumulative is defined as D84.
The volume average particle diameter in the embodiment is D50v, and GSDv is calculated by the following equation.
GSDv = (D84 / D16) ^0.5

(Toner shape factor SF1 measurement method)
The toner shape factor SF1 is obtained by taking an optical microscope image of toner dispersed on a slide glass into a Luzex image analyzer through a video camera, measuring the maximum length (ML) and projection area (A) of each of 100 toners, It is obtained by measuring SF1 of each particle from the following formula and averaging this.
SF1 = {(ML) ² / A} × (100 × π / 4)

  The acid value was measured according to JIS K0070, and was measured using a neutralization titration method. That is, an appropriate amount of a sample is taken, 100 ml of a solvent (diethyl ether / ethanol mixed solution) and a few drops of an indicator (phenolphthalein solution) are added, and the mixture is thoroughly shaken on a water bath until the sample is completely dissolved. This was titrated with a 0.1 mol / l potassium hydroxide ethanol solution, and the end point was when the indicator was light red for 30 seconds. When the acid value is A, the sample amount is S (g), the 0.1 mol / l potassium hydroxide ethanol solution used for the titration is B (ml), and f is the factor of the 0.1 mol / l potassium hydroxide ethanol solution. , A = (B × f × 5.611) / S.

The true specific gravity ρ of the magnetic particles is measured using a Le Chatelier specific gravity bottle in accordance with JIS-K-0061 5-2-1. The operation is as follows.
(1) About 250 ml of ethyl alcohol is put into a Lechatelier specific gravity bottle and adjusted so that the meniscus is at the position of the scale.
(2) The specific gravity bottle is immersed in a constant temperature water bath, and when the liquid temperature reaches 20.0 ± 0.2 ° C., the position of the meniscus is accurately read with the scale of the specific gravity bottle. (Accuracy 0.025ml)
(3) About 100 g of a sample is weighed and its mass is defined as W (g).
(4) Put the weighed sample in a specific gravity bottle to remove bubbles.
(5) The specific gravity bottle is immersed in a constant temperature water bath, and when the liquid temperature becomes 20.0 ± 0.2 ° C., the position of the meniscus is accurately read with the scale of the specific gravity bottle. (Accuracy 0.025ml)
(6) The true specific gravity is calculated by the following formula.
D = W / (L2-L1)
ρ = D / 0.9982
In the above formula, D is the density of the sample (20 ° C.) (g / cm ³ ), ρ is the true specific gravity of the sample (20 ° C.), W is the apparent mass (g) of the sample, and L1 is the sample in a specific gravity bottle. The previous meniscus reading (20 ° C.) (ml), L2 is the meniscus reading after placing the sample in the density bottle (20 ° C.) (ml), 0.9982 is the density of water at 20 ° C. (g / cm ³ ).

  The volume average particle diameter d of the magnetic particles and the carrier is measured using a laser diffraction / scattering type particle size distribution analyzer (LS Particle Size Analyzer: LS13 320, manufactured by BECKMAN COULTER). For the particle size range (channel) obtained by dividing the obtained particle size distribution, the volume cumulative distribution is subtracted from the small particle size side, and the particle size that becomes 50% cumulative is defined as the volume average particle size d.

The BET specific surface area A (m ² / g) of the magnetic particles is measured by the following method.
Using a BET specific surface area meter (SA3100, manufactured by Beckman Coulter, Inc.) as a measuring device, 0.1 g of a porous silicon nitride fine powder as a measurement sample is precisely weighed and placed in a sample tube, and then degassed. A numerical value obtained by automatic measurement by the point method is defined as a BET specific surface area A of the magnetic particles.

The spherical equivalent specific surface area a (m ² / g) of the magnetic particles is represented by the following formula (2).
Formula (2): a = 6 / (d × ρ)
Here, d represents the volume average particle diameter (unit: μm) of the magnetic particles, and ρ represents the true specific gravity (unit: dimensionless) of the magnetic particles.

The spherical equivalent surface area a is a specific surface area per unit mass when the magnetic particles are assumed to be perfectly smooth spheres, and can be derived as follows.
When the volume average particle diameter of the magnetic particles is d (μm), the surface area S (m ² ) and the volume V (m ² ) of one magnetic particle are represented by the following formulas (3) and (4). .
Formula (3): S = 4π × {(d / 2) × 10 ⁻⁶ } ²
Formula (4): V = (4/3) × π × {(d / 2) × 10 ⁻⁶ } ³
Further, when the true specific gravity of the magnetic particles is ρ (dimensionalless), the density of the magnetic particles is represented by ρ × 10 ⁶ (g / m ³ ), and the mass M (g) of one magnetic particle is as follows. It is represented by Formula (5).
Formula (5): M = V × ρ × 10 ⁶ = (1/6) πρd ³ × 10 ⁻¹²
Therefore, as described above, since the spherical equivalent surface area a is a surface area per unit mass, the above formula (2) is derived as in the following formula (6).
Formula (6): a = S / M = 6 / (d × ρ)

The volume electric resistance (Ω · cm) of the magnetic particles is measured as follows. The measurement environment is a temperature of 20 ° C. and a humidity of 50% RH.
A measurement object is placed flat on the surface of a circular jig having a 20 cm ² electrode plate so as to have a thickness of about 1 to 3 mm to form a layer. A 20 cm ² electrode plate similar to the above is placed thereon, and the layer is sandwiched. In order to eliminate gaps between objects to be measured, a thickness (cm) of the layer is measured after a load of 4 kg is applied on the electrode plate placed on the layer. Both electrodes above and below the layer are connected to an electrometer and a high voltage power generator. By applying a high voltage so that the electric field is 10 ^3.8 V / cm to both electrodes, and reading the current value (A) flowing at this time, the volume electric resistance (Ω · cm) of the measurement object is calculated. To do. The calculation formula of the volume electrical resistance (Ω · cm) of the measurement object is as shown in the following formula.
Formula: R = E × 20 / (I−I ₀ ) / L

In the above formula, R is the volume electric resistance (Ω · cm) of the measurement object, E is the applied voltage (V), I is the current value (A), I ₀ is the current value (A) at the applied voltage of 0 V, and L is Each layer thickness (cm) is expressed. A coefficient of 20 represents the area (cm ² ) of the electrode plate.

[Regarding magnetic particles A to F]
<Production of magnetic particles A>
The production of the magnetic particles A was performed as follows.
After mixing 70 parts by weight of Fe ₂ O ₃ , 22.5 parts by weight of MnO _{2 and} 6.5 parts by weight of Mg (OH) ₂ , mixing / pulverizing with a wet ball mill for 30 hours, granulating and drying with a spray dryer, Pre-baking 1 was performed for 7 hours at 850 ° C. using a rotary kiln. The pre-fired product thus obtained was pulverized for 2 hours with a wet ball mill to a volume average particle size of 2.1 μm, further granulated and dried with a spray dryer, and then at 910 ° C. for 6 hours using a rotary kiln. The preliminary firing 2 was performed. The two calcined products thus obtained were pulverized for 4.8 hours with a wet ball mill to a volume average particle size of 5.5 μm, further granulated and dried with a spray dryer, and then heated at a temperature of 950 using an electric furnace. The main calcination was performed at a temperature of 16 hours. Through the crushing step and the classification step, magnetic particles A having a volume average particle size of 36.0 μm were prepared. The BET specific surface area was 0.1332 m ² / g.
The characteristics of the obtained magnetic particles A are as shown in Table 1.

<Production of magnetic particles B>
The production of the magnetic particles B was performed as follows.
After mixing 70 parts by weight of Fe ₂ O ₃ , 22.5 parts by weight of MnO _{2 and} 6.5 parts by weight of Mg (OH) ₂ , mixing / pulverizing with a wet ball mill for 30 hours, granulating and drying with a spray dryer, Pre-baking 1 was performed for 7 hours at 850 ° C. using a rotary kiln. The pre-fired product thus obtained was pulverized for 2 hours with a wet ball mill to a volume average particle size of 2.1 μm, further granulated and dried with a spray dryer, and then at 910 ° C. for 6 hours using a rotary kiln. The preliminary firing 2 was performed. The two calcined products thus obtained were pulverized with a wet ball mill for 7 hours to a volume average particle size of 4.6 μm, further granulated and dried with a spray dryer, and then heated at a temperature of 950 ° C. using an electric furnace. The main baking was performed for 20 hours. Magnetic particles B having a volume average particle size of 29.6 μm were prepared through the crushing step and the classification step. The BET specific surface area was 0.0902 m ² / g.
The characteristics of the obtained magnetic particles B are as shown in Table 1.

<Production of magnetic particles C>
The production of the magnetic particles C was performed as follows.
After mixing 70 parts by weight of Fe ₂ O ₃ , 22.5 parts by weight of MnO _{2 and} 6.5 parts by weight of Mg (OH) ₂ , mixing / pulverizing with a wet ball mill for 30 hours, granulating and drying with a spray dryer, Pre-baking 1 was performed for 7 hours at 850 ° C. using a rotary kiln. The pre-fired product thus obtained was pulverized for 2 hours with a wet ball mill to a volume average particle size of 2.1 μm, further granulated and dried with a spray dryer, and then at 910 ° C. for 6 hours using a rotary kiln. The preliminary firing 2 was performed. The two calcined products thus obtained were pulverized for 4.8 hours by a wet ball mill to a volume average particle size of 5.6 μm, further granulated and dried by a spray dryer, and then heated at a temperature of 920 using an electric furnace. The main calcination was performed at a temperature of 10 hours. Through the crushing step and the classification step, magnetic particles C having a volume average particle size of 35.8 μm were prepared. The BET specific surface area was 0.1895 m ² / g.
The characteristics of the obtained magnetic particles C are as shown in Table 1.

<Production of magnetic particles D>
The production of the magnetic particles D was performed as follows.
After mixing 70 parts by weight of Fe ₂ O ₃ , 22.5 parts by weight of MnO _{2 and} 6.5 parts by weight of Mg (OH) ₂ , mixing / pulverizing with a wet ball mill for 30 hours, granulating and drying with a spray dryer, Pre-baking 1 was performed for 7 hours at 850 ° C. using a rotary kiln. The pre-fired product thus obtained was pulverized for 2 hours with a wet ball mill to a volume average particle size of 2.1 μm, further granulated and dried with a spray dryer, and then at 910 ° C. for 6 hours using a rotary kiln. The preliminary firing 2 was performed. The two calcined products thus obtained were pulverized for 4.5 hours with a wet ball mill to a volume average particle size of 5.8 μm, further granulated and dried with a spray dryer, and then heated at a temperature of 850 using an electric furnace. The main calcination was performed at a temperature of 10 hours. Magnetic particles C having a volume average particle size of 37.6 μm were prepared through a crushing step and a classification step. The BET specific surface area was 0.2421 m ² / g.
The characteristics of the obtained magnetic particles D are as shown in Table 1.

<Production of magnetic particles E>
The production of the magnetic particles E was performed as follows.
After mixing 70 parts by weight of Fe ₂ O ₃ , 22.5 parts by weight of MnO _{2 and} 6.5 parts by weight of Mg (OH) ₂ , mixing / pulverizing with a wet ball mill for 30 hours, granulating and drying with a spray dryer, Pre-baking 1 was performed for 7 hours at 850 ° C. using a rotary kiln. The pre-fired product thus obtained was pulverized for 2 hours with a wet ball mill to a volume average particle size of 2.1 μm, further granulated and dried with a spray dryer, and then at 910 ° C. for 6 hours using a rotary kiln. The preliminary firing 2 was performed. The two calcined products thus obtained were pulverized for 7.0 hours with a wet ball mill to a volume average particle size of 4.5 μm, further granulated and dried with a spray dryer, and then heated at a temperature of 950 using an electric furnace. The main calcination was performed at 24 ° C. for 24 hours. Through the crushing step and the classification step, magnetic particles E having a volume average particle size of 28.5 μm were prepared. The BET specific surface area was 0.0888 m ² / g.
The characteristics of the obtained magnetic particles E are as shown in Table 1.

<Production of magnetic particles F>
The production of the magnetic particles F was performed as follows.
After mixing 70 parts by weight of Fe ₂ O ₃ , 22.5 parts by weight of MnO _{2 and} 6.5 parts by weight of Mg (OH) ₂ , mixing / pulverizing with a wet ball mill for 30 hours, granulating and drying with a spray dryer, Pre-baking 1 was performed for 7 hours at 850 ° C. using a rotary kiln. The pre-fired product thus obtained was pulverized for 2 hours with a wet ball mill to a volume average particle size of 2.1 μm, further granulated and dried with a spray dryer, and then at 910 ° C. for 6 hours using a rotary kiln. The preliminary firing 2 was performed. The two calcined products thus obtained were pulverized for 4.5 hours by a wet ball mill to a volume average particle size of 5.8 μm, further granulated and dried by a spray dryer, and then heated at a temperature of 840 using an electric furnace. The main calcination was performed at 8 ° C. for 8 hours. Through the crushing step and the classification step, magnetic particles F having a volume average particle size of 37.0 μm were prepared. The BET specific surface area was 0.2926 m ² / g.
The characteristics of the obtained magnetic particles F are as shown in Table 1.

[Manufacture of resin used as material for coating resin layer]
<Manufacture of resin A>
The resin A was produced as follows.
960 parts by weight of cyclohexyl methacrylate (cyclohexyl methacrylate), 10 parts by weight of dimethylaminoethyl methacrylate (dimethylaminoethyl methacrylate), 30 parts by weight of methacrylic acid (methyl acrylate), 1000 parts by weight of benzene, 20 parts by weight of azobisisobutyronitrile Are mixed, heated to 60 ° C., shaken for 8 hours, and polymerized. The reaction product was dissolved in methyl ethyl ketone and precipitated with 7 times the amount of hexane to obtain Resin A. The obtained resin had an acid value of 20.03 mg · KOH / g and a weight average molecular weight of 108,000.

<Manufacture of resin B>
Production of the resin B was performed as follows.
975 parts by weight of cyclohexyl methacrylate (cyclohexyl methacrylate), 10 parts by weight of dimethylaminoethyl methacrylate (dimethylaminoethyl methacrylate), 15 parts by weight of methacrylic acid (methyl acrylate), 1000 parts by weight of benzene, 20 parts by weight of azobisisobutyronitrile Are mixed, heated to 60 ° C., shaken for 8 hours, and polymerized. The reaction product was dissolved in methyl ethyl ketone and precipitated with 7 times the amount of hexane to obtain Resin B. The obtained resin had an acid value of 10.38 mg · KOH / g and a weight average molecular weight of 104,000.

<Manufacture of resin C>
Production of Resin C was performed as follows.
945 parts by weight of cyclohexyl methacrylate (cyclohexyl methacrylate), 10 parts by weight of dimethylaminoethyl methacrylate (dimethylaminoethyl methacrylate), 45 parts by weight of methacrylic acid (methyl acrylate), 1000 parts by weight of benzene, 20 parts by weight of azobisisobutyronitrile Are mixed, heated to 60 ° C., shaken for 8 hours, and polymerized. The reaction product was dissolved in methyl ethyl ketone and precipitated with 7 times the amount of hexane to obtain Resin C. The obtained resin had an acid value of 30.82 mg · KOH / g and a weight average molecular weight of 97,000.

<Manufacture of resin D>
The resin D was produced as follows.
930 parts by weight of cyclopentyl methacrylate (cyclopentyl methacrylate), 10 parts by weight of dimethylaminoethyl methacrylate (dimethylaminoethyl methacrylate), 60 parts by weight of methacrylic acid (methyl acrylate), 1000 parts by weight of benzene, 20 parts by weight of azobisisobutyronitrile Are mixed, heated to 60 ° C., shaken for 8 hours, and polymerized. The reaction product was dissolved in methyl ethyl ketone and precipitated with 7 times the amount of hexane to obtain Resin D. The obtained resin had an acid value of 39.84 mg · KOH / g and a weight average molecular weight of 102,000.

<Manufacture of resin E>
The resin E was produced as follows.
960 parts by mass of cyclohexyl acrylate (cyclohexyl acrylate), 10 parts by mass of dimethylaminoethyl methacrylate (dimethylaminoethyl methacrylate), 30 parts by mass of methacrylic acid (methyl acrylate), 1000 parts by mass of benzene, 20 parts by mass of azobisisobutyronitrile Are mixed, heated to 60 ° C., shaken for 8 hours, and polymerized. The reaction product was dissolved in methyl ethyl ketone and precipitated with 7 times the amount of hexane to obtain Resin E. The obtained resin had an acid value of 19.81 mg · KOH / g and a weight average molecular weight of 107,000.

<Manufacture of resin F>
Production of the resin F was performed as follows.
970 parts by weight of cyclohexyl methacrylate (cyclohexyl methacrylate), 30 parts by weight of methacrylic acid (methyl acrylate), 1000 parts by weight of benzene, and 20 parts by weight of azobisisobutyronitrile are mixed, heated to 60 ° C. and shaken for 8 hours. , Polymerize. The reaction product was dissolved in methyl ethyl ketone and precipitated with 7 times the amount of hexane to obtain Resin F. The obtained resin had an acid value of 20.25 mg · KOH / g and a weight average molecular weight of 110,000.

<Manufacture of resin G>
Production of the resin G was performed as follows.
Mix 970 parts by weight of cyclohexyl acrylate (cyclohexyl acrylate), 30 parts by weight of methacrylic acid (methyl acrylate), 1000 parts by weight of benzene, 20 parts by weight of azobisisobutyronitrile, heat to 60 ° C. and shake for 8 hours. , Polymerize. The reaction product was dissolved in methyl ethyl ketone and precipitated with 7 times the amount of hexane to obtain Resin G. The obtained resin had an acid value of 20.41 mg · KOH / g and a weight average molecular weight of 108,000.

<Manufacture of resin H>
Production of the resin H was performed as follows.
960 parts by weight of methyl methacrylate (methyl methacrylate), 10 parts by weight of dimethylaminoethyl methacrylate (dimethylaminoethyl methacrylate), 30 parts by weight of methacrylic acid (methyl acrylate), 1000 parts by weight of benzene, 20 parts by weight of azobisisobutyronitrile Are mixed, heated to 60 ° C., shaken for 8 hours, and polymerized. The reaction product was dissolved in methyl ethyl ketone and precipitated with 7 times the amount of hexane to obtain Resin H. The obtained resin had an acid value of 19.8 mg · KOH / g and a weight average molecular weight of 105,000.

<Manufacture of resin I>
Resin I was produced as follows.
982 parts by mass of cyclohexyl methacrylate (cyclohexyl methacrylate), 10 parts by mass of dimethylaminoethyl methacrylate (dimethylaminoethyl methacrylate), 8 parts by mass of methacrylic acid (methyl acrylate), 1000 parts by mass of benzene, 20 parts by mass of azobisisobutyronitrile Are mixed, heated to 60 ° C., shaken for 8 hours, and polymerized. The reaction product was dissolved in methyl ethyl ketone and precipitated with 7 times the amount of hexane to obtain Resin I. The obtained resin had an acid value of 5.38 mg · KOH / g and a weight average molecular weight of 101,000.

<Manufacture of resin J>
Resin J was produced as follows.
910 parts by weight of cyclohexyl methacrylate (cyclohexyl methacrylate), 10 parts by weight of dimethylaminoethyl methacrylate (dimethylaminoethyl methacrylate), 80 parts by weight of methacrylic acid (methyl acrylate), 1000 parts by weight of benzene, 20 parts by weight of azobisisobutyronitrile Are mixed, heated to 60 ° C., shaken for 8 hours, and polymerized. The reaction product was dissolved in methyl ethyl ketone and precipitated with 7 times the amount of hexane to obtain Resin J. The obtained resin had an acid value of 52.33 mg · KOH / g and a weight average molecular weight of 105,000.

<Manufacture of resin K>
Production of the resin K was performed as follows.
1000 parts by mass of cyclohexyl methacrylate (cyclohexyl methacrylate), 1000 parts by mass of benzene and 20 parts by mass of azobisisobutyronitrile are mixed, heated to 60 ° C., shaken for 8 hours, and polymerized. The reaction product was dissolved in methyl ethyl ketone and precipitated with 7 times the amount of hexane to obtain Resin K. The obtained resin had an acid value of 0.23 mg · KOH / g and a weight average molecular weight of 106,000.

  Details of Resin A to Resin K are shown in Table 2.

[About Carriers 1-13]
<Preparation of carrier 1>
Magnetic particles A: 1000 parts by weight Toluene: 100 parts by weight Resin A: 25 parts by weight Carbon black (VXC-72; manufactured by Cabot Corporation): 2.6 parts by weight Of the above materials, resin A is converted to toluene After dilution, carbon black was added and stirred for 5 minutes with a homogenizer to prepare a resin solution. The resin solution and magnetic particles A are placed in a vacuum degassing kneader and stirred at 90 ° C. for 20 minutes, and then the pressure is reduced to remove toluene, and cooling and stirring are performed until the product temperature reaches 60 ° C. Was taken out and sieved with a 75 μm sieving mesh to obtain Carrier 1.

<Production of Carrier 2>
Carrier 2 was obtained in the same manner as carrier 1 except that magnetic particle A used in preparation of carrier 1 was replaced with magnetic particle B and resin A was replaced with resin B.

<Preparation of carrier 3>
A carrier 3 was obtained in the same manner as the carrier 1 except that the magnetic particles A and the resin A were used instead of the magnetic particles A and C, respectively.

<Preparation of carrier 4>
A carrier 4 was obtained in the same manner as the carrier 1 except that the magnetic particles A and the resin A were replaced with the magnetic particles A and D used in the production of the carrier 1, respectively.

<Preparation of carrier 5>
A carrier 5 was obtained in the same manner as the carrier 1 except that the resin A used in the production of the carrier 1 was replaced with the resin E.

<Preparation of carrier 6>
A carrier 6 was obtained in the same manner as the carrier 1 except that the resin A used in the production of the carrier 1 was replaced with the resin F.

<Preparation of carrier 7>
A carrier 7 was obtained in the same manner as the carrier 1 except that the resin A used in the production of the carrier 1 was replaced with the resin G.

<Preparation of carrier 8>
A carrier 8 was obtained in the same manner as the carrier 1 except that the resin A used in the production of the carrier 1 was replaced with the resin H.

<Preparation of carrier 9>
A carrier 9 was obtained in the same manner as the carrier 1 except that the resin A used in the production of the carrier 1 was replaced with the resin I.

<Preparation of carrier 10>
A carrier 10 was obtained in the same manner as the carrier 1 except that the resin A used in the production of the carrier 1 was replaced with the resin J.

<Preparation of carrier 11>
A carrier 11 was obtained in the same manner as the carrier 1 except that the resin A used in the production of the carrier 1 was replaced with the resin K.

<Preparation of carrier 12>
A carrier 12 was obtained in the same manner as the carrier 1 except that the magnetic particles A used in the production of the carrier 1 were replaced with the magnetic particles E.

<Preparation of carrier 13>
A carrier 13 was obtained in the same manner as the carrier 1 except that the magnetic particles A used in the production of the carrier 1 were replaced with the magnetic particles F.

  The details of the carriers 1 to 13 obtained as described above are shown in Table 3.

<Manufacture of toner>
As an example, the toner production example of the embodiment will be described in detail, but the present invention is not limited in any way.

<Preparation of resin particle dispersion>
・ Styrene ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ 296 parts by weight ・ N-butyl acrylate ・ ・ ・ ・ 104 parts by weight ・ Acrylic acid ・ ・ ・ ・ ・ ・ ・ ・ ・・ ・ ・ ・ ・ ・ ・ 6 parts by weight ・ Dodecanethiol ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ 10 parts by weight ・ Divinyl adipate ・ ・ ・ ・ ・ 1.8 parts by weight Wako Pure Chemical Industries, Ltd.)
A mixture obtained by mixing and dissolving the above components was mixed with 12 parts of a nonionic surfactant (Sanyo Kasei Co., Ltd .: Nonipol 400) and an anionic surfactant (Daiichi Kogyo Seiyaku Co., Ltd .: Neogen SC) 8 Part by weight was added to a solution dissolved in 610 parts by weight of ion-exchanged water, dispersed in a flask, emulsified, and 8 parts of ammonium persulfate (manufactured by Wako Pure Chemical Industries, Ltd.) was dissolved while slowly mixing for 10 minutes. 50 parts by weight of ion-exchanged water was added, and nitrogen substitution was performed at 0.1 liter / min for 20 minutes. Thereafter, the contents in the flask were heated in an oil bath until the content reached 73 ° C. while stirring, and emulsion polymerization was continued for 5 hours to prepare a resin particle dispersion having a solid content of 40% by weight. A part of the dispersion was left on an oven at 100 ° C. to remove water and the molecular weight was measured. The weight average molecular weight was 32,000.

-Preparation of colorant dispersion-
100 parts by weight of carbon black (Cabot Corporation: Mogal L)
Nonionic surfactant: 10 parts by weight (manufactured by Sanyo Chemical Co., Ltd .: Nonipol 400)
490 parts by weight or more of ion-exchanged water is mixed and dissolved, and dispersed for 30 minutes using a homogenizer (manufactured by IKA: Ultra Turrax T50). A colorant dispersion obtained by dispersing (carbon black) was prepared.

-Preparation of release agent dispersion-
100 parts by weight of paraffin wax (manufactured by Nippon Seiwa Co., Ltd .: HNP0190, melting point 85 ° C.)
Cationic surfactant: 10 parts by weight (manufactured by Kao Corporation: SANISOL B50)
Ion-exchanged water: 390 parts by weight The above is heated to 95 ° C. and dispersed using a homogenizer (IKA Corp .: Ultra Turrax T50), and then pressure discharge type homogenizer A release agent dispersion was prepared by dispersing a release agent having an average particle diameter of 550 nm.

Production of Toner I-Preparation of Aggregated Particles-
Resin particle dispersion ... 320 parts by weight Colorant dispersion ... 80 parts by weight release Agent dispersion liquid: 96 parts by weight Aluminum sulfate (Wako Pure Chemical Industries, Ltd.) 1.5 parts by weight ion-exchanged water ... 1270 parts by weight

The above components were housed in a round stainless steel flask with a temperature control jacket, and dispersed at 5,000 rpm for 5 minutes using a homogenizer (manufactured by IKA, Ultra Turrax T50). The mixture was allowed to stand with stirring with 4 paddles at 20 ° C for 20 minutes. Thereafter, the mixture was heated with a mantle heater while stirring and heated at a heating rate of 1 ° C./min until the inside reached 48 ° C., and held at 48 ° C. for 20 minutes. Next, 80 parts of the resin particle dispersion was gradually added and kept at 48 ° C. for 30 minutes, and then a 1N aqueous sodium hydroxide solution was added to adjust the pH to 6.5.
Thereafter, the temperature was raised to 95 ° C. at a rate of 1 ° C./min and held for 30 minutes. A 0.1N aqueous nitric acid solution was added to adjust the pH to 4.8, and the mixture was allowed to stand at 95 ° C. for 2 hours. Thereafter, the 1N aqueous sodium hydroxide solution was further added to adjust the pH to 6.5, and the mixture was allowed to stand at 95 ° C. for 5 hours. Thereafter, it was cooled to 30 ° C. at 5 ° C./min.
The resulting toner particle dispersion was filtered, (A) 2,000 parts of ion-exchanged water at 35 ° C. was added to the obtained toner particles, (B) allowed to stand for 20 minutes, and (C) then filtered. After the operations from (A) to (C) were repeated 5 times, the toner particles on the filter paper were transferred to a vacuum dryer and dried at 45 ° C. and 1,000 Pa or less for 10 hours. The reason why the pressure is 1,000 Pa or less is that the above-mentioned toner particles are in a water-containing state, and in the initial stage of drying, the water freezes even at 45 ° C. and then the water sublimates. This is because is not constant. However, it was stable at 100 Pa at the end of drying. After returning the inside of the dryer to normal pressure, this was taken out to obtain toner mother particles, and 1.5 parts by weight of silica external additive (manufactured by Nippon Aerosil Co., Ltd., RY-50) was added to 100 parts of the toner mother particles. Part of the mixture was added and mixed with a Henschel mixer at 3,000 rpm for 3 minutes to obtain toner I.
The obtained toner I had a D50v of 5.8 μm, a GSDv of 1.23, and a shape factor SF1 of 132.

<Manufacture of developer>
100 parts by weight of the carrier (carriers 1 to 13) produced above and 7 parts by weight of the toner I produced above were mixed and mixed in a V blender at 40 rpm for 20 minutes to obtain a developer.

  The image quality of this developer was evaluated using a Docu Center Color 400 modified machine manufactured by Fuji Xerox Co., Ltd. The contents of the modification are to operate even when the developer is contained only in the black developing machine. Details are as follows.

<Evaluation test of actual machine>
The developer was housed in a modified Docu Center Color 400 manufactured by Fuji Xerox Co., Ltd., and the test was performed under a cleaning bias of 120 V and a high temperature and high humidity environment (32 ° C./85% RH). While maintaining the toner density at a constant level, the developer having 1000%, 20000, and 50000 images with an image density of 20% is output, and then the development amount, fogging, and injectability are evaluated.

<Evaluation method>
(Development amount)
An image having two 2 cm × 5 cm solid patches was copied, the apparatus was forcibly stopped before transfer to paper, and the development amount (amount of toner before transfer to paper) was measured. Specifically, two precisely weighed tapes are prepared, and two development portions on the surface of the latent image holding member are transferred to the tape using adhesiveness, and the tape after toner collection is accurately weighed again. The amount of development was determined by subtracting the tape mass before toner collection and averaging.
-Criteria-
○: Within the range of development amount 4.5 ± 0.5 g / m ² Δ: Within the range of development amount 4.5 ± 0.75 g / m ² × +: Development amount exceeding 5.25 g / m ² × −: Development amount less than 3.75 g / m ²

(Cover)
In the above (development amount evaluation method), when toner is collected from the surface of the latent image holding member with the tape, toner collection with the tape is performed using the same method as in the evaluation of the development amount for the background portion 10 mm away from the solid patch. The number of toners per 1 cm ^{2 on the} tape was counted.
-Criteria-
○: Less than 100
Δ: 100 or more and less than 200
×: 200 or more

(Injectability)
The white bias in the image was evaluated at cleaning biases of 120V and 240V.
-Criteria-
○ No problem at all △ Some problem × Pretty problem ×× Very problem

  Table 4 shows the evaluation results for each of the images after 1000 images were output.

  Table 5 shows the evaluation results for each after outputting 20000 images.

  Table 6 shows the evaluation results for each after outputting 50000 images.

  As can be seen from these results, this example is an electrophotographic carrier that is superior in charging characteristics and adhesion to magnetic particles as compared with the comparative example, and provides high image quality without fogging or white spots. be able to. Further, the coating resin layer is difficult to peel off, and image formation can be performed stably over a long period of time.

[Toners 1 to 5]
Toners 1 to 5 were produced as follows.
<Manufacture of toner 1>
Polyester resin (Bisphenol A and 1,3-propanediol copolymer, weight average molecular weight (Mw) = 153,000): 77 parts Plant wax (carnauba wax): 6 parts Aromatic hydrocarbon copolymer Petroleum resin: 7 parts · SiO ₂ particles (R972; manufactured by Nippon Aerosil Co., Ltd.): 5 parts · Pigment blue 15: 3: 5 parts After cooling, the mixture is finely pulverized by a jet mill, and further classified twice by an air classifier. The number of toner particles having an average particle diameter of 6.3 μm and a particle diameter of 4 μm or less is 15% by number, and the toner particles having a particle diameter of 16 μm or more. 0.7% by volume of toner base particles a was produced.
A Henschel mixer was prepared by adding 100 parts of these particles, 1.0 part of hydrophobic titanium oxide particles having a particle diameter of 20 nm, 1.8 parts of hydrophobic silica particles having a particle diameter of 40 nm, and 1.8 parts of hydrophobic silica particles having a particle diameter of 120 nm as external additives. The toner 1 was prepared by mixing.

<Manufacture of toner 2>
The external additives used in the production of the toner 1 were 0.8 parts of hydrophobic titanium oxide particles having a particle diameter of 20 nm, 1.0 part of hydrophobic silica particles having a particle diameter of 40 nm, and 0.6 part of hydrophobic silica particles having a particle diameter of 120 nm. A toner 2 was obtained in the same manner as the toner 1 except that the toner was replaced.

<Manufacture of toner 3>
The external additive used in the production of the toner 1 was added to 2.0 parts of hydrophobic titanium oxide particles having a particle diameter of 20 nm, 2.5 parts of hydrophobic silica particles having a particle diameter of 40 nm, and 2.5 parts of hydrophobic silica particles having a particle diameter of 120 nm. A toner 3 was obtained in the same manner as the toner 1 except that the toner was replaced.

<Manufacture of toner 4>
Except for the weight average molecular weight (Mw) of the polyester resin being 97,000, the number of toner particles having an average particle size of 6.1 μm and a particle size of 4 μm or less is 18% by number, and the particle size of 16 μm or more is the same as that of the toner 1 Toner base particles b having 0.5% by volume of toner particles were produced.
A Henschel mixer was prepared by adding 100 parts of these particles, 1.0 part of hydrophobic titanium oxide particles having a particle diameter of 20 nm, 1.8 parts of hydrophobic silica particles having a particle diameter of 40 nm, and 1.8 parts of hydrophobic silica particles having a particle diameter of 120 nm as external additives. The toner 4 was prepared by mixing.

<Manufacture of toner 5>
Except for the weight average molecular weight (Mw) of the polyester resin being 195,000, the toner particles had an average particle diameter of 6.4 μm, a particle diameter of 4 μm or less, 15% by number, and a particle diameter of 16 μm or more, in the same manner as the toner 1. Toner base particles c having 0.8% by volume of toner particles were produced.
A Henschel mixer was prepared by adding 100 parts of these particles, 1.0 part of hydrophobic titanium oxide particles having a particle diameter of 20 nm, 1.8 parts of hydrophobic silica particles having a particle diameter of 40 nm, and 1.8 parts of hydrophobic silica particles having a particle diameter of 120 nm as external additives. To prepare toner 5.

  Table 7 shows the characteristics of the toners 1 to 5.

  100 parts by weight of the carrier 1 produced above and 7 parts by weight of the toner (toners 1 to 5) produced above were mixed and mixed in a V blender at 40 rpm for 20 minutes to obtain developers 1 to 5. Obtained.

  A test similar to the actual machine evaluation test was performed using the developers 1 to 5. Table 8 shows the results of evaluation of the development amount, fogging and injectability after outputting 1,000 images. The evaluation method and criteria are the same as those described above.

  Table 9 shows the results of the development amount, fogging and injectability after outputting 20000 images.

  Table 10 shows the results of development amount, fogging, and injectability after outputting 50000 images.

  As can be seen from these results, the developer using the carrier of the embodiment is excellent in durability.

1 is a cross-sectional view schematically showing a basic configuration of a preferred embodiment (first embodiment) of an image forming apparatus. It is sectional drawing which shows schematically the basic composition of other suitable one Embodiment (2nd embodiment) of an image forming apparatus. It is sectional drawing which shows schematically the basic composition of other suitable one Embodiment (3rd embodiment) of an image forming apparatus.

Explanation of symbols

10, 100, 200... Image forming apparatus 12, 110, 212... Electrostatic latent image holder 14, 120, 214... Charging means 16, 130, 216. , 140, 218... Developing means 141... Developer containing container 146... Developer supplying means 148. , 180, 226... Fixing means 28, 147... Cartridge 210.

Claims (10)

At least magnetic particles,
A coating resin layer that covers the surface of the magnetic particles,
The coating resin layer contains a copolymer of a (meth) acrylic acid ester having a cycloalkyl group in the side chain and a (meth) acrylic acid ester having a nitrogen atom in the side chain,
An electrophotographic carrier, wherein the copolymer has an acid value of 10 mgKOH / g or more and 40 mgKOH / g or less.   2. The electrophotographic carrier according to claim 1, wherein the content of the (meth) acrylic acid ester having a cycloalkyl group in the side chain in the copolymer is 90 wt% or more and 98 wt% or less.   3. The electrophotographic carrier according to claim 1, wherein the copolymer has a weight average molecular weight Mw of 30,000 to 150,000. The carrier for electrophotography according to any one of claims 1 to 3, wherein the magnetic particles satisfy the following formula (1).
Formula (1): 2.0 <= A / a <= 7.0
[Wherein, in formula (1), A represents the BET specific surface area (unit: m ² / g) of the magnetic particles, a represents the spherical equivalent specific surface area (unit: m ² / g) of the magnetic particles, The spherical equivalent surface area a is defined as a = 6 / (d, where d (unit: μm) is the volume average particle diameter of the magnetic particles and ρ (unit: dimensionless) is the true specific gravity of the magnetic particles. Xρ). ]   The electrophotographic carrier according to any one of claims 1 to 4, wherein the (meth) acrylic acid ester having a cycloalkyl group in the side chain is cyclohexyl (meth) acrylate.   The carrier for electrophotography according to any one of claims 1 to 5, wherein the coating resin layer contains a conductive agent. Toner and
An electrophotographic developer comprising: the electrophotographic carrier according to any one of claims 1 to 6.   At least a developer for developing the electrostatic latent image formed on the surface of the electrostatic latent image holding member and supplying it to a developing means for forming a toner image; The electrophotographic developer cartridge according to claim 7, wherein the developer is the electrophotographic developer according to claim 7.   8. A developing means for storing the electrophotographic developer according to claim 7 and developing a toner image by developing the electrostatic latent image formed on the surface of the electrostatic latent image holding member with the electrophotographic developer. And an electrostatic latent image holding member, a charging means for charging the surface of the electrostatic latent image holding member, and a cleaning means for removing toner remaining on the surface of the electrostatic latent image holding member. A process cartridge that is detachable from an image forming apparatus.   At least an electrostatic latent image holding body, a charging means for charging the surface of the electrostatic latent image holding body, an electrostatic latent image forming means for forming an electrostatic latent image on the surface of the electrostatic latent image holding body, Developing means for developing the electrostatic latent image with a developer to form a toner image; transfer means for transferring the toner image to a recording medium; and fixing means for fixing the toner image to the recording medium. An image forming apparatus, wherein the developer is the electrophotographic developer according to claim 7.

Images