JP2009048047A - Magnetic carrier, two-component developer and image forming method - Google Patents

Abstract

Provided is a magnetic carrier that achieves improved dot reproducibility compared to the prior art and is capable of preventing density lowering at the trailing edge of solid images, preventing image density lowering, and scratches on the surface of a photosensitive drum during long-term use. thing.
A magnetic carrier having a magnetic carrier core containing at least a magnetic component and a resin component, and a resin coating layer covering the surface of the magnetic carrier core, the true density of the magnetic carrier being 2.5 g. / Cm ³ or more and 4.2 g / cm ³ or less, and the dynamic resistivity R2500 at the electric field strength of 2500 V / cm of the magnetic carrier is 5.0 × 10 ⁵ Ωcm or more and 1.0 × 10 ⁸ Ωcm or less, A magnetic carrier having a dynamic resistivity R5000 of 1.0 × 10 ⁵ Ωcm or more and 5.0 × 10 ⁷ Ω or less at an electric field strength of 5000 V / cm.
[Selection figure] None

Description

  The present invention relates to a magnetic carrier (hereinafter sometimes simply referred to as “carrier”) used in an electrophotographic system, an electrostatic recording system, and an electrostatic printing system, and a two-component developer (hereinafter, referred to as “carrier”). And an image forming method using the two-component developer.

Development methods such as electrophotography include a one-component development method using only toner and a two-component development method using a mixture of magnetic carrier and toner.
Since the two-component development method uses a magnetic carrier, the triboelectric charging area of the magnetic carrier with respect to the toner is wide, so the charging characteristics are more stable than the one-component development method, and high image quality is maintained over a long period of time. Is advantageous. In addition, since the toner supply capacity of the magnetic carrier to the development area is high, it is often used particularly for a high-speed machine.

In recent years, electrophotographic systems have been used not only for printing documents, but also for printing that requires high image quality with a high image area such as photographs, and printing that requires high speed and high durability such as POD. It was.
In the method of developing with the above two-component developer, in order to secure a sufficient image density and improve fine line reproducibility, the developer magnetic brush is brought into contact with the photosensitive member, and the developing sleeve against the peripheral speed of the photosensitive member. A method is used in which the peripheral speed is increased and development is performed by superimposing an alternating electric field and a direct current electric field.
In this developing method, the magnetic carrier imparts an appropriate amount of positive or negative charge to the toner by frictional charging, and carries the toner on its surface by the electrostatic attraction of the frictional charging. A developer having a toner and a magnetic carrier is coated on a developing sleeve containing a magnet to a predetermined layer thickness by a developer layer thickness regulating member, and an electrostatic charge image carrier (photoconductor) by utilizing magnetic force. And the developing sleeve.
A predetermined developing bias voltage is applied between the photosensitive member and the developing sleeve, and the toner is developed on the photosensitive member in the developing region. There are various properties required for the magnetic carrier, and particularly important properties include appropriate charging properties, pressure resistance against applied electric field, impact resistance, abrasion resistance, spent resistance, and developability. .

As a magnetic carrier used in such a developing method, a carrier in which an insulating resin is coated on the surface of ferrite, magnetite or the like has been used so far. This is because a certain level of pressure resistance against the applied electric field is required. However, with the resin coating, the magnetic carrier is insulated and does not function as a developing electrode at the time of development, so that an edge effect is produced between the halftone and the solid black, and image defects such as so-called white spots may occur.
In order to solve this problem, a magnetic carrier has been proposed in which the volume resistance of the magnetic carrier is controlled to be as low as 10 ^{6 to} 10 ¹⁰ Ωcm (see Patent Document 1). The magnetic carrier improves the white spots at the gradation boundary by controlling the volume resistance and the uneven shape. However, when 100,000 sheets of images having a large image area used in photographs and POD are printed, there is a problem that image density is lowered and dot reproducibility is deteriorated.

In addition, a magnetic carrier is proposed in which the volume resistance in a state where a brush is formed on a developer carrier is defined as 10 ^6.2 Ω · cm or more and 10 ^9.8 Ω · cm or less with an electric field strength of 10 ⁴ V / cm. (See Patent Document 2). The magnetic carrier improves the halftone gradation and carrier adhesion by controlling the volume resistance at an arbitrary electric field strength. However, when used for a long period of time, the toner adheres to or melts on the surface of the magnetic carrier. The toner filming occurs. As a result, there has been a problem that the developer is deteriorated, the developed image is deteriorated, and the density of the trailing edge of the solid image is lowered.
On the other hand, in order to reduce toner adhesion, a magnetic carrier in which the specific gravity of the magnetic carrier is reduced has been proposed (see Patent Document 3). The magnetic carrier has a true specific gravity as small as 1.8 or more and 3.5 g / cm ³ or less, thereby suppressing stress applied to the magnetic carrier and toner in the developing machine and suppressing image deterioration due to toner spent. However, when used for a long time with a high-speed machine such as POD, there is a problem that white spots occur on the photosensitive drum due to carrier adhesion to the image or carrier breakdown.
As described above, various proposals have been made. Improvement of dot reproducibility, prevention of density reduction at the back edge of solid images during long-term use, prevention of image density reduction, prevention of scratches on the surface of the photosensitive drum, and speedup A developer that can cope with the above has not yet been found.
JP 2001-117285 A JP-A-9-197720 Japanese Patent Laid-Open No. 10-142841

The present invention has been made in view of the above circumstances of the prior art.
That is, the object of the present invention is to achieve improved dot reproducibility compared to the prior art, and it is possible to prevent a decrease in density at the rear end of a solid image during long-term use, to prevent a decrease in image density, and to prevent scratches on the surface of the photosensitive drum. It is to provide a magnetic carrier. It is another object of the present invention to provide a magnetic carrier that is free from image defects such as white spots and can cope with high speed. Furthermore, it is to provide a two-component developer containing the magnetic carrier and toner, and an image forming method using the two-component developer.

（式中、Ｒ^１は炭素数１以上２５以下の炭化水素基を示す）
〈４〉 〈１〉乃至〈３〉のいずれかに記載の磁性キャリアと、トナーとを含有する二成分系現像剤に関する。
〈５〉 静電潜像担持体表面を均一に帯電する帯電工程と、該静電潜像担持体表面を露光し静電潜像を形成する露光工程と、該静電潜像担持体表面に形成された静電潜像を二成分系現像剤を用いて現像し、トナー画像を形成する現像工程と、該トナー画像を被転写材上に転写する転写工程と、該被転写材上のトナー画像を定着する定着工程を含む画像形成方法であって、該二成分系現像剤が、〈４〉に記載の二成分系現像剤であることを特徴とする画像形成方法に関する。 As a result of intensive studies, the present inventors have found that the above requirements can be satisfied by adjusting the true density of the magnetic carrier and the dynamic resistivity at a specific electric field strength to the range specified in the present invention. Invented.
That is, the present invention
<1> A magnetic carrier having a magnetic carrier core containing at least a magnetic component and a resin component, and a resin coating layer covering the surface of the magnetic carrier core,
The true density of the magnetic carrier is 2.5 g / cm ³ or more and 4.2 g / cm ³ or less,
The dynamic resistivity R2500 of the magnetic carrier at an electric field strength of 2500 V / cm is 5.0 × 10 ⁵ Ωcm or more and 1.0 × 10 ⁸ Ωcm or less, and the dynamic resistivity R5000 at an electric field strength of 5000 V / cm is 1. The present invention relates to a magnetic carrier that is 0 × 10 ⁵ Ωcm or more and 5.0 × 10 ⁷ Ωcm or less.
<2> The resin coating layer contains conductive fine particles, and the conductive fine particles include conductive fine particles selected from the group consisting of carbon black fine particles, magnetite fine particles, graphite fine particles, titanium oxide fine particles, and alumina fine particles. 1 type or 2 types or more It is related with the magnetic carrier as described in <1> characterized by the above-mentioned.
<3> The resin forming the resin coating layer contains a polymer containing a unit formed from a monomer represented by the following formula (A1), and the proportion of the unit in the polymer is 80. It is related with the magnetic carrier as described in <1> or <2> characterized by being mass% or more.

(Wherein R ¹ represents a hydrocarbon group having 1 to 25 carbon atoms)
<4> A two-component developer containing the magnetic carrier according to any one of <1> to <3> and a toner.
<5> A charging step for uniformly charging the surface of the electrostatic latent image carrier, an exposure step for exposing the surface of the electrostatic latent image carrier to form an electrostatic latent image, and a surface on the surface of the electrostatic latent image carrier. Developing the formed electrostatic latent image using a two-component developer to form a toner image, a transfer step for transferring the toner image onto a transfer material, and a toner on the transfer material An image forming method including a fixing step for fixing an image, wherein the two-component developer is the two-component developer according to <4>.

  According to the preferred embodiment of the present invention, it is possible to achieve dot reproducibility and improvement of a white-out image that are higher than those of conventional ones under the condition that the development bias at the time of image output is kept low. Further, even when used for a long period of time, it is possible to suppress a decrease in density at the rear end of the solid image and a decrease in image density. Furthermore, since the development bias can be kept low, charges are not leaked from the carrier during development, so that scratches on the surface layer of the electrostatic charge image carrier (hereinafter also referred to as a photosensitive drum) and carrier adhesion can be prevented. It is possible to output image quality stably.

The magnetic carrier of the present invention is a magnetic carrier having a magnetic carrier core containing at least a magnetic component and a resin component, and a resin coating layer covering the surface of the magnetic carrier core, wherein the magnetic carrier has a true density. 2.5 g / cm ³ or more and 4.2 g / cm ³ or less, and the dynamic resistivity R2500 of the magnetic carrier at an electric field strength of 2500 V / cm is 5.0 × 10 ⁵ Ωcm or more and 1.0 × 10 ⁸ Ωcm. The dynamic resistivity R5000 at an electric field strength of 5000 V / cm is 1.0 × 10 ⁵ Ωcm or more and 5.0 × 10 ⁷ Ωcm or less.

The magnetic carrier realizes a low-density magnetic carrier by making the magnetic carrier core into composite particles containing at least a magnetic component and a resin component. The true density of the magnetic carrier is 2.5 g / cm ³ or more and 4.2 g / cm ³ or less. Preferably they are 3.0 g / cm < ³ > or more and 4.0 g / cm < ³ > or less. When the true density is within this range, the load on the toner is small in the stirring and mixing of the magnetic carrier and the toner, the contamination of the magnetic carrier surface with the toner is suppressed, and the carrier adheres to the non-image portion of the electrostatic charge image carrier. Is preferable. When it is less than 2.5 g / cm ³ , the carrier adheres to the image portion or the non-image portion and image defects are likely to occur. On the other hand, if it exceeds 4.2 g / cm ³ , the stress on the developer increases between the development regulating blade of the developing device and the developer carrying member, and the developer deterioration accelerates when used at high speed for a long time. , Fog is likely to occur.
Further, when the particle size distribution of the magnetic carrier is measured, the particle ratio (number basis) having a particle size of 10 μm or less is preferably 1% or less. The particle size distribution of the carrier can be measured by a flow type particle image analyzer “FPIA-3000 type” (manufactured by Sysmex Corporation) under measurement and analysis conditions during calibration work. It is considered that 10% or more of the particle diameter of the magnetic carrier having a particle diameter of 10 μm or less corresponds to the resin coating layer. For this reason, since the volume ratio of the resin coating layer to one magnetic carrier is increased, the volume resistance per magnetic carrier is decreased, and the carrier is likely to adhere.

The magnetic carrier of the present invention has a dynamic resistivity R2500 of 5.0 × 10 ⁵ Ωcm or more and 1.0 × 10 ⁸ Ωcm or less at an electric field strength of 2500 V / cm and a dynamic resistivity of 5000 V / cm. R5000 is 1.0 × 10 ⁵ Ωcm or more and 5.0 × 10 ⁷ Ωcm or less. Preferably, R2500 is 1.0 × 10 ⁶ Ωcm or more and 8.0 × 10 ⁷ Ωcm or less, and R5000 is 5.0 × 10 ⁵ Ωcm or more and 3.0 × 10 ⁷ Ωcm or less (
FIG. 1).

By controlling the dynamic resistivity of the magnetic carrier within the above range, the developing bias at the time of image output can be kept low, and high developability can be realized. In other words, this control makes it possible to achieve both high dot reproducibility and stable image density over a long period from a graphic image having a large image area used in photographs and POD to an image having a low image area such as office text. Further, since the developing bias can be kept low, the developing bias does not leak through the carrier, and scratches on the surface layer of the photosensitive drum can be suitably prevented.

  The present inventors have inferred the reason for the excellent performance as follows. Generally, when the toner flies from the carrier surface and is consumed in the development process, a charge having the opposite polarity to the toner is generated on the carrier surface. This is called a counter charge. When the counter charge is accumulated in the carrier, charging of the next toner is prevented, the charge amount distribution is broadened, and toner adhesion (fogging) to the non-image portion is caused. Therefore, by carrying the carrier on the developer carrier, forming a magnetic spike, and rotating the dynamic resistivity within the range of the present invention, the counter charge is instantaneously eliminated, and the carrier surface is made electrostatic. Can be refreshed. As a result, the toner is instantly charged, so that a stable image can be output over a long period of time even if an image having a high image area is output at high speed.

Note that if R2500 exceeds 1.0 × 10 ⁸ Ωcm or R5000 exceeds 5.0 × 10 ⁷ Ωcm, the counter charge tends to accumulate and fog tends to occur. By setting a high value, continuous image output becomes possible. On the other hand, if R2500 is less than 5.0 × 10 ⁵ Ωcm or R5000 is less than 1.0 × 10 ⁵ Ωcm, carrier adhesion may easily occur or a latent image may be found.

In addition, the measuring method of the dynamic resistivity of this invention is as follows.
FIG. 3 shows a schematic diagram of an apparatus for measuring the dynamic resistivity.
400 g of magnetic carrier is prepared, and the magnetic carrier is put into a cleaned CLC5000 developing unit manufactured by Canon Inc. The distance between the developing roller and the regulating blade is adjusted so that the carrier amount on the developing roller (aluminum 24.5φ) as the developer carrying member is 30 mg / cm ² . A 60φ aluminum cylinder (axial length: 358 mm) is set opposite the developing roller, and the distance between the developing roller and the aluminum cylinder is adjusted to (D) 400 μm. The aluminum cylinder is rotated at a speed of 200 mm / s in the circumferential direction, and the developing roller is rotated at a speed of 360 mm / s in the forward direction with the aluminum cylinder. The aluminum cylinder is grounded (potential 0V), the developing roller is DC, a voltage from + 50V to + 1000V is applied, and the dynamic resistivity of the magnetic carrier is obtained from the flowing current value. The dynamic resistivity is calculated using the following formula.
(Expression) Dynamic resistivity = resistance × (development nip width × Sl length) / (D)
Here, resistance = applied voltage / (measured potential / r), r = 12 kΩ, development nip width is 0.3 cm, S1 length is 30 cm, D is 400 μm, applied voltage and measured potential are (V).

In order to adjust the dynamic resistivity of the magnetic carrier within the range of the present invention, a magnetic carrier core containing at least a magnetic component and a resin component may be used as the carrier core. The following problems may occur when a coated (coated) carrier is produced using a core in which a low resistance component is uniformly present, such as a conventionally used iron powder carrier core or ferrite carrier core. When conductive fine particles are added to the coating layer covering the core, the carrier breaks down when a certain amount is exceeded, and the dynamic resistivity cannot be measured. Therefore, it becomes difficult for the carrier using the core to control the dynamic resistivity within the range defined by the present invention. We interpret this event as follows. When a magnetic carrier core containing at least a magnetic component and a resin component is used, the carrier core functions as a resistance member because the resin component (= high resistance component) is contained in the carrier core. As a result, the dynamic resistivity of the coat carrier can be controlled in multiple stages.

Furthermore, examples of the method for controlling the dynamic resistivity of the magnetic carrier of the present invention include the following methods (A) to (E), but are not limited thereto. These methods may be performed alone or in combination.
(A) A method in which the conductive fine particles contained in the carrier coating resin are made highly conductive and the particle size distribution of the particles is made sharp.
(B) A method of coating (coating) the carrier surface uniformly and completely so that the core of the carrier is not exposed.
(C) A method in which organic / inorganic fine particles having a particle size of around 100 nm are contained in a carrier coating resin, and an uneven portion is formed on the carrier surface to control the flow of electrons on the carrier surface.
(D) A method of preparing by changing the number average particle diameter of the magnetic component used in the carrier core.
(E) A method of adding fine particles having high resistance by adding fine particles to be contained in the carrier coating resin to conductive fine particles.

  Moreover, the present inventors show the significance of measuring a dynamic resistivity below. Until now, as a method of measuring the resistance of a magnetic carrier, a cell E as shown in FIG. 4 is filled with a sample, and a lower electrode 41 and an upper electrode 42 are arranged so as to be in contact with the filled sample. This has been done by applying a voltage between them and measuring the current flowing at that time. In this method, the relative volume resistance between carriers can be compared. However, the carrier is used in a state where magnetic spikes are formed, or is held with a magnetic force on the developer carrier, and is used while rotating. That is, since the actual usage pattern and the measurement pattern are different, there are often cases where the measurement result and the developability cannot be correlated with the conventional measurement method. It has been found that the dynamic resistivity of the present invention provides a realistic correlation between each property of the carrier core, the carrier coating resin, and the conductive fine particles present in the coating resin, and developability.

The magnetic carrier core used in the present invention will be described.
The magnetic carrier core used in the present invention contains at least a magnetic component and a resin component from the viewpoint of reducing the true density. In particular, a magnetic component-dispersed resin carrier core, which is a composite particle in which a magnetic component is dispersed in a resin component, obtained by a polymerization method is preferable, but the present application is not limited to this. The carrier core obtained by the polymerization method is preferable because the particle size distribution can be sharpened. The resin component used for the carrier core and the resin component used for the resin coating layer may be the same or different. The resin component used for the carrier core is particularly required to have strength. On the other hand, the resin component used in the resin coating layer is required to have triboelectric chargeability. Therefore, the resin component used for the carrier core and the resin component used for the resin coating layer are preferably different resin components.

When the magnetic component-dispersed resin carrier is used, when the conductive material is added to the resin coating layer covering the surface of the magnetic carrier core, the dynamic resistivity is reduced without breaking down against the applied voltage. It becomes easy to control the range.
This is different from conventional ferrite carrier cores and iron powder carrier cores, because there are resin components that are subdivided inside the carrier core, so that a very fine high resistance region exists inside the carrier core. Therefore, it is expected that the carrier core can be maintained as a resistance material without being broken down even when an arbitrary applied voltage is applied.

The following are mentioned as a magnetic component used for this invention.
1) Iron powder with oxidized or unoxidized surface.
2) Metal particles such as lithium, calcium, magnesium, nickel, copper, zinc, cobalt, manganese, chromium, and rare earth elements.
3) Alloy particles of metals such as iron, lithium, calcium, magnesium, nickel, copper, zinc, cobalt, manganese, chromium, and rare earth elements, or oxide particles containing these elements.
4) Magnetite particles or (magnetic) ferrite particles.
Among these, preferable magnetic components are magnetite particles, or magnetic ferrite particles having at least one element selected from copper, zinc, manganese, calcium, lithium and magnesium.

  The 50% particle size (D50) based on the volume distribution of the magnetic carrier core may be a particle size substantially corresponding to the particle size of the magnetic carrier, and is preferably 15 μm or more and 70 μm or less. By making such a range, since the resin component can be appropriately impregnated, the occurrence of coalescence of the magnetic carrier particles due to an excessive amount of the resin component can be suppressed, and further, the magnetic carrier particles have an appropriate circular shape. Degrees can be granted.

  The number average particle diameter of the magnetic component contained in the magnetic carrier core is preferably 80 nm or more and 800 nm or less. By adjusting the number average particle diameter of the magnetic component to 80 nm or more and 800 nm or less, the detachment of the magnetic component from the carrier core is suppressed. Furthermore, when the number average particle diameter of the magnetic component is adjusted to 80 nm or more and 800 nm or less, aggregation of the magnetic carrier particles can be suppressed when the resin component is contained, so that the magnetic carrier particles and the spherical shape are combined. The abundance of irregularly shaped particles can be reduced.

The intensity of magnetization of the magnetic component in the magnetic carrier core, 1000 / 4π (kA / m ) 30Am 2 / kg or more under a magnetic field of, is preferably not more than 75Am ² / kg, more preferably 40 Am ² / Kg or more and 68 Am ² / kg or less. The purpose of adjusting the strength of magnetization of the magnetic component is to provide a magnetic carrier with a good magnetic transport force and restraining force and to obtain a high image quality by increasing the density of the developing magnetic brush at the developing pole.

The content of the magnetic component in the magnetic carrier core is preferably 70% by mass or more and 95% by mass or less, more preferably 80% by mass or more and 92% by mass or less, based on the total mass of the magnetic carrier. preferable. The purpose of adjusting the content of the magnetic component is to make the true density of the magnetic carrier 2.5 g / cm ³ or more and 4.2 g / cm ³ or less, and to sufficiently secure the mechanical strength of the magnetic carrier. Because.
The magnetic carrier core may contain a nonmagnetic inorganic compound together with a magnetic component. By containing a nonmagnetic inorganic compound, the magnetic properties and specific resistance of the magnetic carrier can be adjusted.

  Although the manufacture example of the said magnetic carrier core is shown, it is not limited to these. The magnetic carrier core can be produced by polymerizing monomers for forming the resin component of the carrier core in the presence of the magnetic component. At this time, the magnetic component itself plays a role of a dispersing agent, thereby suppressing coalescence of the magnetic carrier core particles and suppressing formation of magnetic carrier core particles that are not spherical. As another production example, a resin component (vinyl-based or non-vinyl-based thermoplastic resin), a magnetic component, and other additives as necessary are sufficiently mixed by a mixer. The obtained mixture is melted and kneaded using a kneader such as a heating roll, a kneader, or an extruder. A magnetic carrier core can be obtained by pulverizing and classifying the cooled melt-kneaded product. The resulting carrier core may be further spheroidized thermally or mechanically.

Examples of the resin component used for the magnetic carrier core include resins such as vinyl resin, polyester resin, epoxy resin, phenol resin, urea resin, polyurethane resin, polyimide resin, cellulose resin, silicone resin, acrylic resin, and polyether resin. It is done. These resins may be one kind or a mixed resin of two or more kinds. In particular, a phenol resin is preferable in terms of shape stability and strength of the magnetic carrier core.

  The resin coating layer covering the surface of the magnetic carrier core preferably contains conductive fine particles. Further, the conductive fine particles preferably contain one or more conductive fine particles selected from the group consisting of carbon black fine particles, magnetite fine particles, graphite fine particles, titanium oxide fine particles, alumina fine particles and the like. Among these conductive fine particles, the carbon black fine particles are particularly preferable because they have a small particle size and hardly cause unevenness on the carrier surface. When particles other than the above carbon black fine particles, magnetite fine particles, graphite fine particles, titanium oxide fine particles, alumina fine particles, etc. are used, it is difficult to uniformly disperse in the resin coating layer, and a desired dynamic resistivity is obtained. In some cases, the developability deteriorates and a sufficient image density cannot be obtained.

As for the particle diameter of the conductive fine particles, the maximum peak value based on the number distribution is preferably 10 nm or more and 60 nm or less for uniform dispersion in the resin coating layer (more preferably 15 nm or more and 50 nm or less). Moreover, it is also preferable in order to satisfactorily prevent the removal of the conductive fine particles from the carrier.
The maximum peak value based on the number distribution of the conductive fine particles is preferably close to the primary particle size. Furthermore, it is preferable that the conductive fine particles have a variation coefficient of the particle size distribution of 20% or less as measured using a laser diffraction particle size distribution analyzer. As a result, the conductive fine particles added to the resin coating layer are more likely to be present more uniformly, and the refreshing effect on the carrier surface is easily exhibited.
By allowing the conductive fine particles to be uniformly present in the coating resin, the dynamic resistivity of the magnetic carrier can be controlled within a desired range. Also, in the long-term durability test, the conductive fine particles are removed from the resin coating layer. The initial performance can be maintained without desorption.
As the method for dispersing the conductive fine particles in the resin coating layer, a coating solution (hereinafter also referred to as a coating solution) may be a known one such as a sand mill, a ball mill, a roll mill, a homogenizer, a nanomizer, a paint shaker, or an ultrasonic wave. Examples thereof include a method of dispersing the conductive fine particles using means. For particles with a primary particle size of 20 nm to 50 nm such as carbon black, the particle size distribution can be sharpened more efficiently by using a dispersing machine such as Super Aspec Mill or Ultra Aspec Mill manufactured by Kotobuki Industries. Can be.
Moreover, in this invention, there is no limitation in particular in the method of coat | covering the said resin coating layer on the surface of a magnetic carrier core, A well-known method can be used.

  The conductive fine particles are preferably contained in the resin coating layer in an amount of 2 to 50 parts by mass with respect to 100 parts by mass of the resin used for the resin coating layer. As a result, the dynamic resistivity of the magnetic carrier is not lowered too much, and the counter charge on the surface of the magnetic carrier can be easily removed.

When carbon black is used as the conductive fine particles, the DBP oil absorption of the carbon black is preferably 100 to 500 ml / 100 g. Preferably, it is 350 to 500 ml / 100 g. If it is within this range, the carbon black dispersed in the resin coating layer exhibits appropriate conductive properties and can be easily controlled to a desired dynamic resistivity. However, when the DBP oil absorption is small, the conductivity of the carbon black does not function sufficiently, and it becomes difficult to control the dynamic resistivity of the magnetic carrier within a desired range. If the DBP oil absorption is larger than 500 ml / 100 g, it is difficult to uniformly disperse carbon black in the resin coating layer. As a result, the dynamic resistivity of the magnetic carrier is remarkably lowered or aggregated carbon black particles are generated, leak sites are formed in the resin coating layer, which may cause white spots on the surface of the photosensitive drum.

Next, the resin coating layer that covers the surface of the magnetic carrier core will be described.
The resin forming the resin coating layer of the magnetic carrier (hereinafter also referred to as coating resin) is a monomer represented by the following formula (A1) for providing toner with charging and at the same time developing the toner stably. It is preferable to contain the polymer containing the unit formed from. Moreover, it is preferable that the ratio of this unit occupied in this polymer is 80 mass% or more.
The proportion of the unit in the polymer can be determined by the following method. For example, the coating resin is separated from the magnetic carrier using a solvent such as toluene, additives such as carbon black are removed by centrifugation or the like, and the resin is separated after drying. Perform IR measurement of the obtained ^{resin, 1720cm -1, 1450cm -1, 1150cm} -1, 1120cm -1, obtained by observing the peaks from 1 to 25 carbon atoms. As the measuring device, FT-IR (Spectrum One / AutoImage) manufactured by Perkin Elmer can be used.
The coating resin preferably contains a polymer of a monomer represented by the following formula (A1). The coating resin can also contain a copolymer of a monomer represented by the following formula (A1) and a monomer other than the following formula (A1).

（式中、Ｒ^１は炭素数１以上２５以下の炭化水素基を示す）

(Wherein R ¹ represents a hydrocarbon group having 1 to 25 carbon atoms)

Moreover, it is more preferable that the coating resin contains a polymer containing a unit formed from a methyl methacrylate monomer (a monomer in which R ^{1 in the} formula (A1) is a hydrocarbon group having 1 carbon atom). This is because the methyl methacrylate monomer has a function of charging the toner. The present inventors have found that a coating resin having a smaller carbon number of R ¹ has a higher ability to impart charge to the toner, and a larger carbon number has a lower capability.

Further, the coating resin is a unit formed from a methyl methacrylate monomer and a hydrocarbon group having R ¹ in the above formula (A1) having 4 to 25 carbon atoms (more preferably 4 to 20 carbon atoms). More preferably, it contains a copolymer containing units formed from monomers.
By containing the copolymer in the coating resin, charging to the toner is improved, and charge-up or charge-down after the toner reaches the desired charge amount in the developing device can be suppressed. . This is because the unit formed from methyl methacrylate has high chargeability and stable chargeability even in various environments.
On the other hand, the unit formed from the monomer in which R ¹ is a hydrocarbon group having 4 to 25 carbon atoms in the above formula (A1) increases the crystallinity of the coating resin and improves the releasability on the surface of the magnetic carrier. Can do. Therefore, it is considered that quick application of triboelectric charge to the toner and toner adhesion to the magnetic carrier particles can be reduced.

The hydrocarbon group having 4 to 25 carbon atoms may be a chain hydrocarbon group or a cyclic hydrocarbon group.
Examples of the monomer in which R ¹ is a hydrocarbon group having 4 to 25 carbon atoms in the above formula (A1) include the following. Butyl methacrylate, isobutyl methacrylate, t-butyl methacrylate, 2-ethylhexyl methacrylate, lauryl methacrylate, dodecyl methacrylate, tridecyl methacrylate, tetradecyl methacrylate, pentadecyl methacrylate, hexadecyl methacrylate, heptadecyl methacrylate and methacrylic acid Octadecyl, cyclobutyl methacrylate, cyclopentyl methacrylate, cyclohexyl methacrylate, cycloheptyl methacrylate, dicyclopentenyl methacrylate and dicyclopentanyl methacrylate.

を意味する。また、メタクリル酸メチルモノマーから形成されるユニットとは、

を意味する。
また、メタクリル酸メチルモノマーから形成されるユニットと、上記式（Ａ１）においてＲ^１が炭素数４以上２５以下の炭化水素基であるモノマーから形成されるユニットとの共重合比（質量比）は、０．５：９９．５から８０：２０であることが好ましい。 The unit formed from the monomer represented by the formula (A1) is

Means. In addition, the unit formed from methyl methacrylate monomer is

Means.
Further, a unit formed from a methyl methacrylate monomer, the copolymerization ratio of the units R ¹ in the formula (A1) is formed from a monomer is a hydrocarbon group having 4 to 25 carbon atoms (mass ratio) 0.5: 99.5 to 80:20.

  The resin forming the resin coating layer has a weight average molecular weight Mw (THF soluble content) of 15,000 or more and 300,000 or less, so that it adheres to the magnetic carrier core and covers the resin coating layer. It is preferable because the core surface can be uniformly coated.

  Furthermore, the resin forming the resin coating layer is a copolymer obtained by polymerizing a monomer represented by the above formula (A1), a methyl methacrylate monomer, and a monomer represented by the following formula (A2). Is particularly preferred.

（式中、ｎは繰り返し回数を示し、正の整数を示す）

(Where n represents the number of repetitions and represents a positive integer)

The resin forming the resin coating layer is a copolymer obtained by polymerizing the monomer represented by the above formula (A1), the methyl methacrylate monomer, and the monomer represented by the above formula (A2). The adhesion between the coating layer and the magnetic carrier core and the wear resistance of the resin coating layer can be enhanced. The weight average molecular weight Mw (THF soluble content) of the monomer represented by the above formula (A2) is not less than 3,000 to not more than 15,000, and does not inhibit the main chain from being crystallized. This is preferable for improving the adhesion between the layer and the magnetic carrier core. The number of repetitions n is preferably 10 or more and 300 or less.

The amount of the resin forming the resin coating layer is preferably 0.3 parts by mass or more and 4.0 parts by mass or less, more preferably 1.0 parts by mass or more with respect to 100 parts by mass of the magnetic carrier core. 3.5 parts by mass or less. This is to improve the chargeability and charge retention to the toner in the developer, and to improve the separation of the toner from the magnetic carrier during development. Further, it is also suitable as a means for controlling the dynamic resistivity of the magnetic carrier of the present invention within a desired range. If the amount of the resin is too small, the magnetic carrier core may be exposed, and the carrier is likely to break down. Moreover, when there is too much quantity of resin, it will become difficult to obtain the dynamic resistivity which utilized the characteristic of the core.
Furthermore, when adding fine particles described later to the coating resin, it is easy to form minute protrusions on the surface of the magnetic carrier by the fine particles.
When the resin amount of the resin coating layer is 0.3 parts by mass or more and 4.0 parts by mass or less, even if the resin coating is used for durability, good charging of the magnetic carrier to the toner can be performed, and the fine particles are coated with the resin. When it is contained in the layer, the fine particles are well retained.

The fine particles contained in the resin coating layer of the magnetic carrier used in the present invention may be fine particles of either an organic material or an inorganic material, but the strength that can maintain the shape of the fine particles when coated. Cross-linked resin fine particles and inorganic fine particles having bismuth are preferred.
Examples of the crosslinked resin forming the crosslinked resin fine particles include a crosslinked polymethyl methacrylate resin, a crosslinked polystyrene resin, a melamine resin, a phenol resin, and a nylon resin.
Examples of the inorganic fine particles include magnetite, hematite, silica, alumina, and titanium-containing metal oxide. In particular, the above-mentioned inorganic fine particles are preferable from the viewpoints of promoting charging imparted to the toner, reducing charge-up, and improving releasability from the toner.

  The two-component developer of the present invention is characterized by containing the magnetic carrier of the present invention and a toner. Hereinafter, the toner used for the two-component developer of the present invention will be described.

The toner of the present invention preferably has an average circularity of 0.930 to 1.000, more preferably 0.950 to 1.000. A toner having an average circularity of 0.930 or more and 1.000 or less can maintain good developability and transferability from the initial stage to after durable use. In particular, the average circularity of the toner is 0.930 or more and 1.000 or less, and the average circularity of the magnetic carrier is 0.850 or more and 0.950 or less. That is, the toner having the average circularity and the magnetic carrier can hardly damage the toner and maintain the toner on the magnetic carrier while maintaining the charge imparting ability of the magnetic carrier to the toner.
The average circularity of the toner is determined by appropriately selecting a method for producing toner particles (for example, selecting a suspension granulation method or an emulsion polymerization method), or by kneading and pulverizing toner particles by a known method (for example, mechanical force or (By using heat).

The toner preferably contains a toner binder resin and a colorant. Further, the weight average particle diameter of the toner is preferably 4.0 μm or more and 8.0 μm or less, more preferably 4.0 μm or more and 7.0 μm or less, and 4.5 μm or more and 6.5 μm or less. More preferably it is. When the weight average particle diameter of the toner is 4.0 μm or more and 8.0 μm or less, dot reproducibility and transfer efficiency can be sufficiently improved.
The weight average particle diameter of the toner can be adjusted by classification of the toner particles at the time of production and mixing of classified products.

Preferred embodiments of the toner include the toner of the following first embodiment and the toner of the second embodiment.
The toner of the first aspect is a toner having toner particles containing a binder resin mainly composed of a polyester unit and a colorant (hereinafter, also referred to as “the toner of the first aspect”). “Polyester unit” refers to a part derived from polyester, and “resin mainly composed of polyester unit” means a resin in which many of the repeating units constituting the resin are repeating units having an ester bond. However, these will be described in detail later.
The polyester unit is formed by condensation polymerization of ester monomers. Examples of the ester-based monomer include a polyhydric alcohol component and a carboxylic acid component such as a polyvalent carboxylic acid, a polyvalent carboxylic acid anhydride, or a polyvalent carboxylic acid ester having two or more carboxyl groups.

The following are mentioned as a dihydric alcohol component among a polyhydric alcohol component.
Polyoxypropylene (2.2) -2,2-bis (4-hydroxyphenyl) propane, polyoxypropylene (3.3) -2,2-bis (4-hydroxyphenyl) propane, polyoxyethylene (2. 0) -2,2-bis (4-hydroxyphenyl) propane, polyoxypropylene (2.0) -polyoxyethylene (2.0) -2,2-bis (4-hydroxyphenyl) propane, polyoxypropylene (6) alkylene oxide adduct of bisphenol A such as -2,2-bis (4-hydroxyphenyl) propane; ethylene glycol, diethylene glycol, triethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1 , 4-butanediol, neopentyl glycol, 1,4-butenedio , 1,5-pentanediol, 1,6-hexanediol, 1,4-cyclohexanedimethanol, dipropylene glycol, polyethylene glycol, polypropylene glycol, polytetramethylene glycol, bisphenol A, hydrogenated bisphenol A.

Examples of the trihydric or higher alcohol component among the polyhydric alcohol components include the following.
Sorbitol, 1,2,3,6-hexanetetrol, 1,4-sorbitan, pentaerythritol, dipentaerythritol, tripentaerythritol, 1,2,4-butanetriol, 1,2,5-pentanetriol, glycerol 2-methylpropanetriol, 2-methyl-1,2,4-butanetriol, trimethylolethane, trimethylolpropane, 1,3,5-trihydroxymethylbenzene.

The following are mentioned as a carboxylic acid component which comprises a polyester unit.
Aromatic dicarboxylic acids such as phthalic acid, isophthalic acid and terephthalic acid or anhydrides thereof; alkyl dicarboxylic acids such as succinic acid, adipic acid, sebacic acid and azelaic acid or anhydrides thereof; Substituted succinic acids or anhydrides thereof; unsaturated dicarboxylic acids such as fumaric acid, maleic acid and citraconic acid or anhydrides thereof.

Preferable examples of the resin having a polyester unit contained in the toner of the first aspect include the following. That is, a bisphenol derivative represented by the structure represented by the following formula (1) is used as an alcohol component, and a carboxylic acid component (for example, fumaric acid) composed of a divalent or higher carboxylic acid or an acid anhydride thereof or a lower alkyl ester thereof. , Maleic acid, maleic anhydride, phthalic acid, terephthalic acid, dodecenyl succinic acid, trimellitic acid, pyromellitic acid) as a carboxylic acid component, and a polyester resin obtained by polycondensing them. This polyester resin has good charging characteristics. This charging property of the polyester resin works effectively for the effect of the present invention.

〔式中、Ｒはエチレン基及びプロピレン基から選ばれる１種以上であり、ｘ及びｙはそれぞれ１以上の整数であり、且つｘ＋ｙの平均値は２以上１０以下である。〕

[In the formula, R is one or more selected from an ethylene group and a propylene group, x and y are each an integer of 1 or more, and the average value of x + y is 2 or more and 10 or less. ]

Moreover, the polyester resin which has a bridge | crosslinking site | part is contained in the preferable example of resin which has the said polyester unit. The polyester resin having a crosslinking site can be obtained by subjecting a polyhydric alcohol and a carboxylic acid component containing a trivalent or higher polyvalent carboxylic acid to a condensation polymerization reaction.
Examples of the trivalent or higher polyvalent carboxylic acid component include 1,2,4-benzenetricarboxylic acid, 1,2,5-benzenetricarboxylic acid, 1,2,4-naphthalenetricarboxylic acid, 2,5,7. -Naphthalene tricarboxylic acid, 1,2,4,5-benzenetetracarboxylic acid, and acid anhydrides and ester compounds thereof. The content of the trivalent or higher polyvalent carboxylic acid component contained in the ester monomer to be polycondensed is preferably 0.1 or more and 1.9 mol% or less based on the total monomer.

Furthermore, the following (a)-(e) is mentioned as a preferable example of resin which has the said polyester unit.
(A) A hybrid resin having a polyester unit and a vinyl polymer unit. (B) A mixture of a hybrid resin and a vinyl polymer.
(C) A mixture of a polyester resin and a vinyl polymer.
(D) A mixture of a hybrid resin and a polyester resin.
(E) A mixture of a polyester resin, a hybrid resin, and a vinyl polymer.
The hybrid resin is formed by a transesterification reaction between a polyester unit and a vinyl polymer unit obtained by polymerizing a monomer component having a carboxylic acid ester group such as an acrylic ester. Is.
Examples of the hybrid resin include a graft copolymer or a block copolymer in which a vinyl polymer is a trunk polymer and a polyester unit is a branch polymer.
The vinyl polymer unit refers to a portion derived from a vinyl polymer. A vinyl polymer unit or a vinyl polymer can be obtained by polymerizing a vinyl monomer described later.

The toner of the second aspect is a toner having toner particles obtained from a direct polymerization method or in an aqueous medium (hereinafter also referred to as “the toner of the second aspect”). The toner according to the second aspect may be produced by a direct polymerization method, or may be produced by previously forming emulsified fine particles and then aggregating together with a colorant and a release agent. The toner having toner particles produced by the latter is also referred to as “a toner obtained from an aqueous medium” or “a toner obtained by an emulsion polymerization method”.
The toner of the second embodiment preferably has toner particles having a resin mainly composed of a vinyl resin, obtained by a direct polymerization method or an emulsion polymerization method.

The vinyl resin that is the main component of the toner particles is produced by polymerization of a vinyl monomer. The following are mentioned as a vinyl-type monomer.
Styrenic monomers, acrylic monomers; methacrylic monomers; monomers of ethylenically unsaturated monoolefins; monomers of vinyl esters; monomers of vinyl ethers; monomers of vinyl ketones; monomers of N-vinyl compounds: other vinyl monomers.

The following are mentioned as a styrene-type monomer.
Styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, p-methoxystyrene, p-phenylstyrene, p-chlorostyrene, 3,4-dichlorostyrene, p-ethylstyrene, 2,4-dimethyl Styrene, pn-butyl styrene, p-tert-butyl styrene, pn-hexyl styrene, pn-octyl styrene, pn-nonyl styrene, pn-decyl styrene, pn-dodecyl styrene .

The following are mentioned as an acryl-type monomer.
Methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, propyl acrylate, n-octyl acrylate, dodecyl acrylate, 2-ethylhexyl acrylate, stearyl acrylate, dimethylaminoethyl acrylate, acrylic acid Acrylic esters such as phenyl, acrylic acid and acrylic amides.

Moreover, the following are mentioned as a methacrylic monomer.
Ethyl methacrylate, propyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, n-octyl methacrylate, dodecyl methacrylate, 2-ethylhexyl methacrylate, stearyl methacrylate, phenyl methacrylate, dimethylaminoethyl methacrylate, methacryl Methacrylic acid esters such as diethylaminoethyl acid and methacrylic acid and methacrylic acid amides.

Examples of the monomer of the ethylenically unsaturated monoolefins include ethylene, propylene, butylene, and isobutylene.
Examples of vinyl ester monomers include vinyl acetate, vinyl propionate, and vinyl benzoate.
Examples of vinyl ether monomers include vinyl methyl ether, vinyl ethyl ether, and vinyl isobutyl ether.
Examples of vinyl ketone monomers include vinyl methyl ketone, vinyl hexyl ketone, and methyl isopropenyl ketone.
Examples of the monomer of the N-vinyl compound include N-vinyl pyrrole, N-vinyl carbazole, N-vinyl indole, and N-vinyl pyrrolidone.
Other vinyl monomers include acrylic acid derivatives or methacrylic acid derivatives such as vinyl naphthalenes, acrylonitrile, methacrylonitrile and acrylamide.
These vinyl monomers can be used alone or in combination of two or more.

The following are mentioned as a polymerization initiator used when manufacturing a vinyl-type resin.
2,2′-azobis- (2,4-dimethylvaleronitrile), 2,2′-azobisisobutyronitrile, 1,1′-azobis (cyclohexane-1-carbonitrile), 2,2′-azobis Azo or diazo polymerization initiators such as -4-methoxy-2,4-dimethylvaleronitrile, azobisisobutyronitrile; benzoyl peroxide, methyl ethyl ketone peroxide, diisopropyl peroxycarbonate, cumene hydroperoxide, t-butyl hydroperoxide, Di-t-butyl peroxide, dicumyl peroxide, 2,4-dichlorobenzoyl peroxide, lauroyl peroxide, 2,2-bis (4,4-t-butylperoxycyclohexyl) propane, tris- (t-butylperoxy) triazine Peroxide system such as Initiator or initiator having a peroxide in the side chain; persulfate such as potassium persulfate or ammonium persulfate; hydrogen peroxide.

  Examples of radically polymerizable trifunctional or higher polymerization initiators include tris (t-butylperoxy) triazine, vinyltris (t-butylperoxy) silane, 2,2-bis (4,4-di-). t-butylperoxycyclohexyl) propane, 2,2-bis (4,4-di-t-amylperoxycyclohexyl) propane, 2,2-bis (4,4-di-t-octylperoxycyclohexyl) propane And a radical polymerizable polyfunctional polymerization initiator such as 2,2-bis (4,4-di-t-butylperoxycyclohexyl) butane.

  Both the two-component developer using the toner of the first aspect and the toner of the second aspect are preferably used in an electrophotographic process employing oilless fixing. Therefore, the toner (the toner of the first aspect and the toner of the second aspect) preferably contains a release agent.

Examples of the release agent include the following.
Low molecular weight polyethylene, low molecular weight polypropylene, polyolefin copolymer, polyolefin wax, microcrystalline wax, paraffin wax, aliphatic hydrocarbon wax such as Fischer-Tropsch wax; oxide of aliphatic hydrocarbon wax such as oxidized polyethylene wax, Or block copolymers thereof; waxes mainly composed of fatty acid esters such as carnauba wax, montanic acid ester wax, and behenyl behenate; fatty acid esters such as deoxidized carnauba wax partially or fully deoxidized . Suitable release agents include hydrocarbon waxes and paraffin waxes.

The toner has one or more endothermic peaks in the temperature range of 30 ° C. to 200 ° C. in the endothermic curve of the toner in differential scanning calorimetry (DSC) analysis measurement, and the maximum endothermic peak temperature in the endothermic peak is 50. When the temperature is not lower than 110 ° C. and not higher than 110 ° C., the toner can have good low-temperature fixability and durability.
Examples of the apparatus used for the differential scanning calorimetry measurement include Perkin Elmer DSC-7, TA Instrument DSC2920, TA Instrument Q1000, and the like. The temperature correction of the device detection unit uses the melting points of indium and zinc, and the correction of heat quantity uses the heat of fusion of indium. An aluminum pan is used as a measurement sample, and an empty pan is set for control and measured.

  The content of the release agent is preferably 1 part by mass or more and 15 parts by mass or less, and preferably 3 parts by mass or more and 10 parts by mass or less with respect to 100 parts by mass of the binder resin in the toner particles. More preferred. When the content of the release agent is 1 part by mass or more and 15 parts by mass or less, excellent release properties can be exhibited when an oilless fixing method is employed.

  The toner used in the present invention may contain a charge control agent. Charge control agents include organometallic complexes, metal salts, chelate compounds, metal salts of carboxylic acids, metal compounds of aromatic carboxylic acids, carboxylic acid anhydrides, condensates of aromatic compounds such as esters , Phenol derivatives such as bisphenols and calixarenes, and the like. Examples of the organometallic complexes include monoazo metal complexes, acetylacetone metal complexes, hydroxycarboxylic acid metal complexes, polycarboxylic acid metal complexes, and polyol metal complexes. The charge control agent is preferably a metal compound of an aromatic carboxylic acid from the viewpoint of improving the charge rising of the toner.

The content of the charge control agent is 0.1 parts by mass or more with respect to 100 parts by mass of the binder resin.
It is preferably 0 parts by mass or less, and more preferably 0.2 parts by mass or more and 5.0 parts by mass or less. When the content of the charge control agent satisfies the above range, the change in the charge amount of the toner can be reduced in a wide range of environments from high temperature and high humidity to low temperature and low humidity.

  The triboelectric charge amount of the toner is not particularly limited, but the absolute value is preferably 25 mC / Kg or more and 45 mC / Kg or less.

The toner used in the two-component developer of the present invention preferably contains a colorant. Here, the colorant may be a pigment or a dye, or a combination thereof.
Examples of the dye include the following.
C. I. Direct Red 1, C.I. I. Direct Red 4, C.I. I. Acid Red 1, C.I. I. Basic Red 1, C.I. I. Modern Tread 30, C.I. I. Direct Blue 1, C.I. I. Direct Blue 2, C.I. I. Acid Blue 9, C.I. I. Acid Blue 15, C.I. I. Basic Blue 3, C.I. I. Basic Blue 5, C.I. I. Modern Blue 7, C.I. I. Direct Green 6, C.I. I. Basic Green 4, C.I. I. Basic green 6.
Examples of the pigment include the following.
Mineral Fast Yellow, Navel Yellow, Naphthol Yellow S, Hansa Yellow G, Permanent Yellow NCG, Tartrazine Lake, Molybdenum Orange, Permanent Orange GTR, Pyrazolone Orange, Benzidine Orange G, Permanent Red 4R, Watching Red Calcium Salt, Eosin Lake, Brilliant Carmine 3B, Manganese Purple, Fast Violet B, Methyl Violet Lake, Cobalt Blue, Alkaline Blue Lake, Victoria Blue Lake, Phthalocyanine Blue, Fast Sky Blue, Indanthrene Blue BC, Chrome Green, Pigment Green B, Malachite Green Lake, Final Yellow green G.

When the two-component developer of the present invention is used as a developer for forming a full-color image, the toner can contain a magenta color pigment.
Examples of the magenta coloring pigment include the following.
C. I. Pigment Red 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 21, 22, 23, 30, 31, 32, 37, 38, 39, 40, 41, 48, 49, 50, 51, 52, 53, 54, 55, 57, 58, 60, 63, 64, 68, 81, 83, 87, 88, 89, 90, 112, 114, 122, 123, 163, 202, 206, 207, 209, 238, C.I. I. Pigment violet 19, C.I. I. Bat red 1, 2, 10, 13, 15, 23, 29, 35.

The toner may contain only the magenta color pigment, but if it contains a combination of a dye and a pigment, the clarity of the developer can be improved and the image quality of the full-color image can be improved.
Examples of the magenta dye include the following.
C. I. Solvent Red 1, 3, 8, 23, 24, 25, 27, 30, 49, 81, 82, 83, 84, 100, 109, 121, C.I. I. Disper thread 9, C.I. I. Solvent Violet 8, 13, 14, 21, 27, C.I. I. Oil-soluble dyes such as Disperse Violet 1; I. Basic Red 1, 2, 9, 12, 13, 14, 15, 17, 18, 22, 23, 24, 27, 29, 32, 34, 35, 36, 37, 38, 39, 40, C.I. I. Basic dyes such as Basic Violet 1, 3, 7, 10, 14, 15, 21, 25, 26, 27, 28.

Examples of the color pigment for cyan include the following.
C. I. Pigment Blue 2, 3, 15, 15: 1, 15: 2, 15: 3, 16, 17
C. I. Acid Blue 6; I. A copper phthalocyanine pigment in which 1 to 5 phthalimidomethyl groups are substituted on Acid Blue 45 or a phthalocyanine skeleton.

Examples of the color pigment for yellow include the following.
C. I. Pigment Yellow 1, 2, 3, 4, 5, 6, 7, 10, 11, 12, 13, 14, 15, 16, 17, 23, 65, 73, 74, 83, 93, 97, 155, 180, C. I. Bat yellow 1, 3, 20

Examples of the black pigment include carbon powder such as furnace black, channel black, acetylene black, thermal black, and lamp black, and magnetic powder such as magnetite and ferrite.
Further, the color may be adjusted by combining a magenta dye and a pigment, a yellow dye and a pigment, a cyan dye and a pigment, and the carbon black may be used in combination.

  The content of the colorant is preferably 1 part by mass or more and 10 parts by mass or less, more preferably 3 parts by mass or more and 10 parts by mass or less, with respect to 100 parts by mass of the binder resin in the toner. More preferably, it is 4 to 10 parts by mass. When the content of the colorant is 1 part by mass or more and 10 parts by mass or less with respect to 100 parts by mass of the binder resin in the toner, the transparency is maintained, and in addition, it is represented by human skin color. The reproducibility of intermediate colors is also improved. Furthermore, the stability of the charging property of the toner is improved, and a low-temperature fixing property is also obtained.

The toner used in the two-component developer of the present invention may be externally added with external additives that are fine particles. By externally adding fine particles, fluidity and transferability can be improved. The external additive externally added to the toner particle surface preferably contains inorganic fine particles of titanium oxide, alumina oxide, and silica fine particles. The inorganic fine particles preferably have an average particle size (maximum peak value based on the number distribution) of 80 nm or more and 200 nm or less in order for the toner particles to function as spacer particles for easily separating the toner particles from the magnetic carrier.
The external additive can contain fine particles having an average particle size (maximum peak value based on the number distribution) of 50 nm or less in addition to the inorganic fine particles having an average particle size of 80 nm or more and 200 nm or less. Can be improved.

  The surface of the inorganic fine particles contained in the external additive is preferably subjected to a hydrophobic treatment. The hydrophobizing treatment is preferably carried out by a hydrophobizing agent such as various titanium coupling agents and coupling agents such as silane coupling agents; fatty acids and metal salts thereof; silicone oils; or combinations thereof.

Examples of the titanium coupling agent for the hydrophobic treatment include the following.
Tetrabutyl titanate, tetraoctyl titanate, isopropyl triisostearoyl titanate, isopropyl tridecylbenzene sulfonyl titanate, bis (dioctyl pyrophosphate) oxyacetate titanate.
Examples of the silane coupling agent for the hydrophobic treatment include the following.
γ- (2-aminoethyl) aminopropyltrimethoxysilane, γ- (2-aminoethyl) aminopropylmethyldimethoxysilane, γ-methacryloxypropyltrimethoxysilane, N-β- (N-vinylbenzylaminoethyl) γ -Aminopropyltrimethoxysilane hydrochloride, hexamethyldisilazane, methyltrimethoxysilane, butyltrimethoxysilane, isobutyltrimethoxysilane, hexyltrimethoxysilane, octyltrimethoxysilane, decyltrimethoxysilane, dodecyltrimethoxysilane, phenyl Trimethoxysilane, o-methylphenyltrimethoxysilane, p-methylphenyltrimethoxysilane.
Examples of the fatty acid for the hydrophobic treatment include the following.
Long chain fatty acids such as undecylic acid, lauric acid, tridecylic acid, dodecylic acid, myristic acid, palmitic acid, pentadecylic acid, stearic acid, heptadecylic acid, arachidic acid, montanic acid, oleic acid, linoleic acid, arachidonic acid. Examples of the metal of the fatty acid metal salt include zinc, iron, magnesium, aluminum, calcium, sodium, and lithium.
Examples of the silicone oil for the hydrophobic treatment include dimethyl silicone oil, methylphenyl silicone oil, and amino-modified silicone oil.

  The hydrophobic treatment is performed by adding 1% by mass or more and 30% by mass or less (more preferably 3% by mass or more and 7% by mass or less) of a hydrophobizing agent to the inorganic fine particles. It is preferable to carry out by coating.

  The degree of hydrophobization of the hydrophobized inorganic fine particles is not particularly limited. For example, the hydrophobization degree measured by methanol titration test of the treated inorganic microparticles (methanol wettability; an indicator of wettability to methanol) Is preferably 40 or more and 95 or less.

  The content of the external additive in the toner is preferably 0.1% by mass or more and 5.0% by mass or less, and more preferably 0.5% by mass or more and 4.0% by mass or less. . The external additive may be a combination of a plurality of types of fine particles.

  The image forming method of the present invention comprises a charging step for uniformly charging the surface of the electrostatic latent image carrier, an exposure step for exposing the surface of the electrostatic latent image carrier to form an electrostatic latent image, and the electrostatic latent image. The electrostatic latent image formed on the surface of the image carrier is developed using a two-component developer to form a toner image, the transfer step for transferring the toner image onto a transfer material, An image forming method including a fixing step of fixing a toner image on a transfer material, wherein the two-component developer is the two-component developer of the present invention.

Hereinafter, an example of an image forming method in which the magnetic carrier and the two-component developer of the present invention can be suitably used will be described with reference to FIG.
An image forming method in which the present invention is preferably used includes a charging step for uniformly charging the surface of the electrostatic latent image carrier, an exposure step for exposing the surface of the electrostatic latent image carrier to form an electrostatic latent image, Developing the electrostatic latent image formed on the surface of the electrostatic latent image carrier using a two-component developer to form a toner image, and transferring the toner image onto a transfer material And a fixing step of fixing the toner image on the transfer material.
In such an image forming method, the developing step includes a developing container (from 10a in FIG. 2) having a plurality of developing units each having a developer carrying member (developing roller) carrying a two-component developer corresponding to each color toner. 10d), a two-component developer is supported on the developer carrier of each developer container, and a developing bias formed by superimposing an AC electric field on the DC electric field is applied to the developer carrier. A toner image of each color is sequentially formed on an image carrier (photoconductor).

Specifically, the developing step includes applying an AC voltage to the developer carrying member to form an alternating electric field in the developing area and developing the magnetic brush in contact with the electrostatic latent image carrying member. It is preferable to carry out. The distance between the developer carrier and the electrostatic latent image carrier (SD distance) is preferably 100 μm or more and 1000 μm or less in terms of preventing carrier adhesion and improving dot reproducibility. If it is smaller than 100 μm, the supply of the developer tends to be insufficient, and the image density tends to be low. On the other hand, if the thickness exceeds 1000 μm, the lines of magnetic force from the magnetic poles spread and the density of the magnetic brush is lowered, so that the dot reproducibility is inferior, or the force that restrains the magnetic carrier is weakened and carrier adhesion tends to occur.
The voltage between the peaks of the alternating electric field is preferably 300 V or more and 3000 V or less, and the frequency is 50
Although it is 0 Hz or more and 10000 Hz or less, preferably 1000 Hz or more and 7000 Hz or less, it can be appropriately selected and used depending on the process. In this case, the waveform of the AC bias for forming the alternating electric field includes a triangular wave, a rectangular wave, a sine wave, or a waveform with a changed duty ratio. In order to cope with the change in the formation speed of the toner image sometimes, it is preferable to perform development by applying a developing bias voltage (intermittent alternating voltage) having a discontinuous AC bias voltage to the developer carrier. . When the applied voltage is lower than 300 V, it is difficult to obtain a sufficient image density, and the fog toner in the non-image portion may not be recovered well. If the voltage exceeds 3000 V, the latent image may be disturbed via a magnetic brush, resulting in a decrease in image quality. In addition, charges are injected onto the electrostatic latent image carrier, and a part of the image falls out white. It may become a state. That is, when the applied voltage is increased, the image quality is degraded. Therefore, there is a demand for a developer that can obtain a sufficient image density with the voltage between peaks kept as low as possible. The present inventors have found that by using a magnetic carrier having a desired dynamic resistivity, a sufficient image density can be obtained while suppressing the peak-to-peak voltage of the alternating electric field.

By using a two-component developer having a well-charged toner, the fog removal voltage (Vback) can be lowered, and the primary charge of the electrostatic latent image carrier can be lowered. The life of the image carrier can be extended. Vback is 200 V or less, more preferably 150 V or less, although it depends on the development system. The contrast potential is preferably 100 V or more and 400 V or less so that sufficient image density is obtained.
Further, when the frequency is lower than 500 Hz, although it is related to the process speed, when the toner in contact with the electrostatic latent image carrier is returned to the developer carrier, sufficient vibration is not applied and fog is likely to occur. . If it exceeds 10,000 Hz, the toner cannot follow the electric field, and the image quality is likely to deteriorate.

An example of a color image forming apparatus (a copying machine or a laser beam printer) that suitably realizes the image forming method will be described with reference to FIG. Reference numeral 7a denotes a drum-like electrostatic latent image carrier as a first image carrier, which is driven to rotate at a predetermined peripheral speed (process speed) in the direction of the arrow in the figure. In the rotation process, the electrostatic latent image carrier 7a is uniformly charged to a predetermined potential by the charging device 8a (charging process) and then exposed by the image exposure apparatus 9a (latent image forming process). In this manner, an electrostatic latent image corresponding to the first color component image (for example, a yellow toner image) of the target color image is formed.
Next, the electrostatic latent image is developed into a yellow toner image of the first color by the first developing container (yellow toner developing container 10a). Sequentially developing is performed in the same manner by the second to fourth developing containers, that is, the magenta toner developing container 10b, the cyan toner developing container 10c, and the black toner developing container 10d (developing step).
The toner image formed on the electrostatic latent image carrier in the development step is subjected to a transfer step. The transfer process used in the image forming method of the present invention is formed on a transfer material by sequentially superimposing and transferring each color toner image formed on the electrostatic latent image carrier onto the intermediate transfer body. It may comprise a primary transfer process for forming a color toner image on the intermediate transfer body and a secondary transfer process for transferring the color toner image formed on the intermediate transfer body onto a transfer material.
In FIG. 2, the intermediate transfer belt 14 as an intermediate transfer member is rotationally driven in the direction of the arrow at the same peripheral speed as that of the electrostatic latent image carrier 7a (from 7d). The yellow toner image of the first color formed on the electrostatic latent image carrier 7 a passes through the contact portion between the electrostatic latent image carrier 7 a and the intermediate transfer belt 14 and passes through the primary transfer roller 13. Then, the image is sequentially transferred onto the outer peripheral surface of the intermediate transfer belt 14 by the electric field formed by the primary transfer bias applied to the intermediate transfer belt 14. Note that a bias having a polarity opposite to that of the toner is applied as the primary transfer bias at this time. The applied voltage is, for example, in the range of +100 V or more and +2 kV or less. The surface of the electrostatic latent image carrier 7a after the transfer of the first color yellow toner image to the intermediate transfer belt 14 is cleaned by the cleaning device 11a. Similarly, magenta, cyan, and black toner images are also transferred to the intermediate transfer belt 14 to form a full-color image on the intermediate transfer belt 14.
Next, the color toner image is transferred to a transfer material, and this process is called secondary transfer. Reference numeral 4 denotes a secondary transfer roller, which is supported in parallel with the secondary transfer counter roller 3 and arranged in a state in which it can be separated from the lower surface of the intermediate transfer belt 14.
The secondary transfer roller 4 is brought into contact with the intermediate transfer belt 14, and the transfer material P is fed from the paper feed roller 16 to the contact portion between the intermediate transfer belt 14 and the secondary transfer roller 4 at a predetermined timing. At this time, the secondary transfer bias is applied to the secondary transfer roller 4, whereby the full color image transferred onto the intermediate transfer belt 14 is secondarily transferred to the transfer material P. The transfer material P onto which the toner image has been transferred is introduced into the fixing device 15 and is heated and fixed. After the image transfer to the transfer material P is completed, the toner (transfer residual toner) remaining on the intermediate transfer belt is scraped off by the belt cleaning device 5 and carried to a waste toner box.

  The method for measuring various physical properties of the magnetic carrier and toner will be described below.

<Measurement method of true density of magnetic carrier>
The true density of the magnetic carrier of the present invention was measured using a dry automatic densimeter autopycnometer (manufactured by Yuasa Ionics). The measurement conditions are as follows.
(Measurement condition)
Cell SM cell (10 mL)
Sample amount 2.0g
This measurement method measures the true density of a solid / liquid based on a gas phase substitution method. Like the liquid phase replacement method, it is based on Archimedes' principle.

<Measurement of resistivity of magnetic carrier, nonmagnetic inorganic compound, magnetic component and conductive fine particles>
The specific resistances of the magnetic component and the conductive fine particles were measured using a measuring apparatus outlined in FIG. A resistance measurement cell E is filled with a magnetic carrier 47, a lower electrode 41 and an upper electrode 42 are arranged so as to be in contact with the filled magnetic carrier, a voltage is applied between these electrodes, and a current flowing at that time is measured. Thus, the specific resistance of the magnetic carrier was determined.
The specific resistance was measured under the condition that the contact area S between the filled magnetic carrier and the electrode was 2.3 cm ² , the sample thickness L of the filled magnetic carrier was 0.8 mm, and the load on the upper electrode 42 was 180 g. The specific resistance of the magnetic carrier and the nonmagnetic inorganic compound can be measured in the same manner.

<Measurement method of 50% particle size (D50) based on magnetic carrier or magnetic carrier core volume distribution>
The measurement was performed under the measurement and analysis conditions at the time of calibration using a 50% particle diameter (D50) flow type particle image analyzer “FPIA-3000 type” (manufactured by Sysmex Corporation) based on the magnetic carrier or magnetic carrier core volume distribution. The measurement principle of the flow-type particle image analyzer “FPIA-3000 type” (manufactured by Sysmex Corporation) is to capture flowing particles as a still image and perform image analysis. The sample added to the sample chamber is fed into the flat sheath flow cell by the sample suction syringe. The sample fed into the flat sheath flow is sandwiched between sheath liquids to form a flat flow. The sample passing through the flat sheath flow cell is irradiated with strobe light at 1/60 second intervals, and the flowing particles can be photographed as a still image. Further, since the flow is flat, the image is taken in a focused state. The particle image is captured by a CCD camera, and the captured image is subjected to image processing at an image processing resolution of 512 × 512 (0.37 × 0.37 μm per pixel), and the contour of each particle image is extracted, Projected area, perimeter, etc. are measured.
Next, the projected area S and the perimeter L of each particle image are obtained. The equivalent circle diameter is obtained using the area S and the peripheral length L. The equivalent circle diameter is the diameter of a circle having the same area as the projected area of the particle image. Each obtained equivalent circle diameter was divided into 256 parts of 4 to 100 μm and expressed in a logarithmically displayed graph based on volume. From this, a 50% particle diameter (D50) based on volume distribution was obtained.
Specifically, in a 100 cc glass bottle, 0.1 g of the magnetic carrier, 5 drops of the surfactant specified by the measurement device manufacturer, and 50 cc of the sheath water specified by the measurement device manufacturer are treated in an ultrasonic device for 2 minutes. A dispersion of magnetic carrier was prepared. The dispersion was introduced into the measuring apparatus using a dropper and measured.

<Measuring method of maximum peak value based on number distribution of conductive fine particles or external additives>
The maximum peak value (also referred to as the maximum peak particle size) based on the number distribution of the conductive fine particles or external additives is a laser diffraction particle size distribution analyzer SALD-3000, SALD-2200, or SALD-300V (manufactured by Shimadzu Corporation). The measurement was performed according to the operation manual of the measuring instrument, and the above values were calculated.
Specifically, when measurement was performed by a dry method, 0.1 g of both the conductive fine particles and the external additive were introduced into the apparatus and measured. When wet measurement is performed, glass beads having a diameter of 1 mm are put into a 450 cc glass bottle by about 40% of the glass bottle volume. Next, 1.0 g of conductive fine particles and 200 cc of a solvent (for example, toluene) were added, and the mixture was shaken using a paint shaker for 2 hours while applying cold air to the bottle to obtain a dispersion. The dispersion was introduced into the measuring apparatus using a dropper and measured.

<Measurement of DBP oil absorption of carbon black>
The measurement was performed according to JIS 4656/1.

<Method for Measuring Number Average Particle Size of Magnetic Component or Nonmagnetic Inorganic Compound>
The number average particle diameter of the magnetic component or the nonmagnetic inorganic compound was measured by the following procedure.
It was measured by the same method as the method for measuring the maximum peak value based on the number distribution of the conductive fine particles or external additives.
On the other hand, when calculating | requiring the number average particle diameter from a magnetic carrier (core), it measured in the following procedures.
The magnetic component or the nonmagnetic inorganic compound was observed with a transmission electron microscope (TEM) (50,000 times), and 300 or more particles having a particle size of 5 nm or more were randomly extracted. The length of the major axis and minor axis of each extracted particle was measured with a digitizer. The average value of the measured lengths of the major axis and the minor axis is taken as the particle size, and the particle size distribution of 300 or more particles (column width is 5-15, 15-25, (unit: nm),. In this way, the particle diameter of the center value of the column that becomes the peak of the column is defined as the number average particle diameter.

<Measurement method of weight average molecular weight or number average molecular weight of THF soluble content of resin>
The weight average molecular weight (THF soluble content) (Mw) or number average molecular weight (Mn) of the resin is measured by the following procedure by gel permeation chromatography (GPC). The weight average molecular weight of the resin component used in the magnetic carrier core and the binder resin of the toner can also be measured by this measurement procedure.
A THF sample solution adjusted to a sample concentration of 0.05% by mass or more and 0.6% by mass or less by flowing tetrahydrofuran (THF) at a flow rate of 1 ml / min through a column stabilized in a 40 ° C. heat chamber. Is measured by injecting 50 μl or more and 200 μl or less. An RI (refractive index) detector is used as the detector. The column to be used is preferably a combination of a plurality of commercially available polystyrene gel columns in order to accurately measure a molecular weight region of 1 × 10 ³ or more and 2 × 10 ⁶ or less. For example, a combination of μ-styragels 500, 103, 104, and 105 manufactured by Waters and a combination of shodex KA-801, 802, 803, 804, 805, 806, and 807 manufactured by Showa Denko are preferable.
In measuring the molecular weight, the molecular weight distribution of the sample is calculated from the relationship between the logarithmic value of the calibration curve prepared from several monodisperse polystyrene standard samples and the number of counts. As a standard polystyrene sample for preparing a calibration curve, for example, Pressure Chemical Co. Manufactured by Tosoh Corporation, the molecular weight is 6 × 10 ² , 2.1 × 10 ³ , 4 × 10 ³ ,
1.75 × 10 ⁴ , 5.1 × 10 ⁴ , 1.1 × 10 ⁵ , 3.9 × 10 ⁵ , 8.6 × 10 ⁵ , 2 × 10 ⁶ , 4.48 × 10 ⁶ It is appropriate to use at least about 10 standard polystyrene samples.
The coating resin to be measured may be a resin that is a raw material for manufacturing the resin coating layer of the magnetic carrier. In addition, as the coating resin, a methyl ethyl ketone liquid to which a magnetic carrier having a resin coating layer is added at a concentration of 10% by mass is subjected to a dispersion treatment for 2 minutes with an ultrasonic disperser “Tetora 150 type” (manufactured by Nikka Ki Bios). And the dried product of the filtrate obtained by filtering with a membrane filter with an opening of 0.2 μm may be used.

<Method for measuring weight average particle diameter of toner>
The weight average particle diameter of the toner can be measured using a Coulter Counter TA-II or Coulter Multisizer II (manufactured by Beckman Coulter, Inc.). The electrolytic solution is an approximately 1% NaCl aqueous solution, may be prepared using primary sodium chloride, or may be a commercially available product of ISOTON (registered trademark) -II (manufactured by Coulter Scientific Japan).
The weight average particle diameter of the toner is measured as follows. A surfactant (preferably alkylbenzenesulfone hydrochloric acid) as a dispersant is added in an amount of 0.1 ml to 5 ml, and further a measurement sample (toner) is added in an amount of 2 mg to 20 mg. The electrolyte solution in which the sample is suspended is subjected to dispersion treatment for about 1 to 3 minutes with an ultrasonic disperser to obtain a measurement sample.
The aperture is a 100 μm aperture. The volume and number of samples are measured for each channel, and the volume distribution and number distribution of the samples are calculated. From the calculated distribution, the weight average particle diameter of the sample is obtained. The channel is 2.00 to 2.52 μm; 2.52 to 3.17 μm; 3.17 to 4.00 μm; 4.00 to 5.04 μm; 5.04 to 6.35 μm; 6 35 to 8.00 μm; 8.00 to 10.08 μm; 10.08 to 12.70 μm; 12.70 to 16.00 μm; 16.00 to 20.20 μm; 20.20 to 25. 13 channels of 40 μm or less; 25.40 or more and 32.00 μm or less; 32 or more and 40.30 μm or less are used.

<Measurement of average circularity of toner>
The average circularity of the toner was measured with a flow type particle image analyzer “FPIA-3000 type” (manufactured by Sysmex Corporation) under the measurement and analysis conditions during calibration.
As a specific measurement method, an appropriate amount of a surfactant, preferably an alkylbenzene sulfonate, is added to 20 ml of ion-exchanged water, and then 0.06 g of a measurement sample is added, and the oscillation frequency is 50 kHz and the electrical output is 150 W. Dispersion treatment was carried out for 2 minutes using a desktop type ultrasonic cleaner / disperser (for example, “VS-150” (manufactured by Velvo Crea Co., Ltd.)) to obtain a dispersion for measurement. It cooled suitably so that it might become 10 to 40 degreeC.
For the measurement, the flow type particle image analyzer equipped with a high-magnification imaging unit (objective lens (20 ×)) was used, and a particle sheath “PSE-900A” (manufactured by Sysmex Corporation) was used as the sheath liquid. The dispersion prepared in accordance with the above procedure is introduced into the flow type particle image analyzer, and 2000 toner particles are measured in the total count mode in the HPF measurement mode, and the binarization threshold at the time of particle analysis is 85%. The analysis particle diameter was limited to a circle equivalent diameter of 2.00 μm or more and 200.00 μm or less, and the average circularity of the toner particles was determined.
In the measurement, automatic focus adjustment was performed using standard latex particles (for example, 5100A manufactured by Duke Scientific) diluted with ion-exchanged water before the measurement was started. Thereafter, focus adjustment was performed every 2 hours from the start of measurement.
In this embodiment, a flow type particle image analyzer that has been issued a calibration certificate issued by Sysmex Corporation, which has been calibrated by Sysmex Corporation, has an analysis particle diameter of 2.00 μm. The measurement was performed under the measurement and analysis conditions when the calibration certificate was received, except that it was limited to 200.00 μm or less.

<Magnetic strength of magnetic component>
The strength of the magnetization of the magnetic component can be obtained by a vibrating magnetic field type magnetic characteristic device VSM (Vibrating sample magnetometer), a direct current magnetization characteristic recording device (BH tracer), or the like. For example, the measurement can be performed by the following procedure using an oscillating magnetic field type magnetic property automatic recording apparatus BHV-30 manufactured by Riken Denshi Co., Ltd. A cylindrical plastic container is filled with a magnetic component sufficiently densely, while an external magnetic field of 1000 / 4π (kA / m) (1000 oersted) is created, and in this state, the magnetization moment of the magnetic component filled in the container is determined. taking measurement. Further, the actual mass of the magnetic component filled in the container is measured to determine the magnetization intensity (Am ² / kg) of the magnetic component.

  EXAMPLES Hereinafter, although this invention is demonstrated more concretely with reference to an Example, this invention is not limited only to these Examples.

[Manufacture of carrier A]
Magnetite fine particles (number average particle size 260 nm, magnetization strength 65 Am ² / kg, specific resistance 3.2 × 10 ⁵ Ω · cm) and silane coupling agent (3- (2-aminoethylaminopropyl) trimethoxy Silane) (amount of 3.0% by mass with respect to the mass of the magnetite fine particles) was introduced into a container, and the mixture was stirred at a high speed at 100 ° C. or higher in the container to surface-treat the magnetite fine particles.
Next, the following materials, phenol 10 parts by mass, formaldehyde solution (formaldehyde 36% by weight aqueous solution) 16 parts by mass, and surface-treated magnetite fine particles 86 parts by mass were introduced into a flask and mixed well at 40 ° C. At this time, the amount of dissolved oxygen in the reaction medium was 9.00 g / m ³ . Next, nitrogen gas was introduced into the reaction medium while heating to 65 ° C. The flow rate of the introduced amount of nitrogen gas was 250 cm ³ / min, and gas replacement was performed for 30 minutes. The amount of dissolved oxygen in the reaction medium after gas replacement for 30 minutes was 0.90 g / m ³ .
Thereafter, 4 parts by mass of 28% by mass aqueous ammonia and 8 parts by mass of water were added to the flask while keeping the amount of nitrogen introduced at 50 cm ³ / min so as not to allow oxygen to enter. While stirring, the mixture was heated from 65 ° C. to 85 ° C. at an average heating rate of 3 ° C./min. It was kept at 85 ° C. and cured by polymerization reaction for 3 hours. The peripheral speed of the stirring blade at this time was 1.8 m / sec.
After the polymerization reaction, the mixture was cooled to 30 ° C. and water was added. The precipitate obtained by removing the supernatant was washed with water and further air-dried. The obtained air-dried product was dried at 60 ° C. under reduced pressure (5 hPa or less) to obtain a spherical magnetic carrier core (a) in which magnetic components were dispersed. The volume-based 50% particle size (D50) of the magnetic carrier core (a) was 35 μm.
Next, 1 part by mass of a methyl methacrylate macromer having a weight average molecular weight of 5,000 having an ethylenically unsaturated group at one end having a structure represented by the following formula (1) (where n represents the number of repetitions), 197 parts by mass of a cyclohexyl methacrylate monomer having an ester moiety with cyclohexyl having a structure represented by the following formula (2) as a unit, and 2 parts by mass of a methyl methacrylate monomer are reflux condenser, thermometer, nitrogen suction tube, and a mixture To a four-necked flask with a stirrer. Further, 90 parts by mass of toluene, 110 parts by mass of methyl ethyl ketone, and 2.0 parts by mass of azobisisovaleronitrile were added. The obtained mixture was held at 70 ° C. for 10 hours under a nitrogen stream to obtain a graft copolymer solution (solid content: 33% by mass). The weight average molecular weight of this solution by gel permeation chromatography (GPC) was 50,000.

得られたグラフト共重合体溶液３０質量部に、疎水化処理することにより得られた疎水性シリカ粒子（個数分布基準の最大ピーク粒径が１００ｎｍ）１質量部、カーボンブラック微粒子（個数分布基準の最大ピーク粒径が３０ｎｍ、比抵抗が１．０×１０^−４Ω・ｃｍ）１質量部、およびトルエン１００質量部を加えて、該スーパーアスペックミルによりよく混合して、コート液を得た。
次いで、磁性キャリアコア（ａ）５００質量部を、剪断応力を連続して加えながら撹拌しつつ、上記コート液を徐々に加えた。減圧下（５ｈＰａ）で７０℃に保持して撹拌しながら溶媒を揮発させて、磁性キャリアコア表面を樹脂で被覆した。
この樹脂で被覆された磁性キャリアコアを、１００℃で２時間撹拌しながら熱処理した。冷却した後、解砕し、さらに目開き７６μｍの篩で粗粒を除去して、磁性キャリアであるキャリアＡを得た。キャリアＡの体積基準の５０％粒径（Ｄ５０）は３５．０μｍであり、表１に示すような物性を持つキャリアであった。

30 parts by mass of the obtained graft copolymer solution is 1 part by mass of hydrophobic silica particles (number distribution standard maximum peak particle size is 100 nm) obtained by hydrophobizing, carbon black fine particles (number distribution standard 1 part by mass of the maximum peak particle size of 30 nm and specific resistance of 1.0 × 10 ⁻⁴ Ω · cm) and 100 parts by mass of toluene were added and mixed well with the Super Aspec Mill to obtain a coating solution. .
Subsequently, the coating liquid was gradually added while stirring 500 parts by mass of the magnetic carrier core (a) while continuously applying shear stress. The solvent was volatilized while stirring at 70 ° C. under reduced pressure (5 hPa), and the surface of the magnetic carrier core was coated with a resin.
The magnetic carrier core coated with this resin was heat-treated with stirring at 100 ° C. for 2 hours. After cooling, the mixture was crushed and coarse particles were removed with a sieve having an aperture of 76 μm to obtain carrier A as a magnetic carrier. The volume-based 50% particle size (D50) of Carrier A was 35.0 μm, and it was a carrier having physical properties as shown in Table 1.

[Manufacture of carrier B]
Carrier B was obtained in the same manner as Carrier A except that the following fine particles were used in place of 86 parts by mass of the surface-treated magnetite fine particles when preparing the magnetic carrier core.
-Surface-treated magnetite fine particles 73 parts by mass-Surface-treated hematite fine particles 10 parts by mass Carrier B has a volume-based 50% particle size (D50) of 36.0 μm and is a carrier having physical properties as shown in Table 1. It was.

[Manufacture of carrier C]
Magnetite fine particles (number average particle size 260 nm, magnetization strength 65 Am ² / kg, specific resistance 3.2 × 10 ⁵ Ω · cm) and silane coupling agent (3- (2-aminoethylaminopropyl) trimethoxy Instead of (silane) (amount of 3.0% by mass with respect to the mass of magnetite fine particles), magnetite fine particles (number average particle size 200 nm, magnetization strength 65 Am ² / kg, specific resistance 8.0 × 10 ⁵ Ω · cm) and a silane coupling agent (3- (2-aminoethylaminopropyl) trimethoxysilane) (amount of 6.0% by mass with respect to the mass of magnetite fine particles), hydrophobic silica particles (number distribution) 1 part by mass of the standard maximum peak particle size is 100 nm) and 1 part by mass of hydrophobic silica particles (the maximum peak particle size of the number distribution standard is 200 nm). The same as carrier A except that 1 part by mass of the fine particles (maximum peak particle size based on the number distribution is 30 nm, specific resistance is 1.0 × 10 ⁻⁴ Ω · cm) is changed to 0.7 parts by mass of the carbon black fine particles. Carrier C was obtained by the method. The volume-based 50% particle size (D50) of carrier C was 35.0 μm, and the carrier had physical properties as shown in Table 1.

[Manufacture of carrier D]
Magnetite fine particles (number average particle size 260 nm, magnetization strength 65 Am ² / kg, specific resistance 3.2 × 10 ⁵ Ω · cm) and silane coupling agent (3- (2-aminoethylaminopropyl) trimethoxy Instead of (silane) (amount of 3.0% by mass relative to the mass of magnetite fine particles), magnetite fine particles (number average particle size 300 nm, magnetization strength 65 Am ² / kg, specific resistance 4.0 × 10 ⁵ Ω · cm) and a silane coupling agent (3- (2-aminoethylaminopropyl) trimethoxysilane) (2.0% by mass with respect to the mass of the magnetite fine particles), carbon black fine particles (number distribution standard) The maximum peak particle size of 30 nm and the specific resistance is 1.0 × 10 ⁻⁴ Ω · cm) except that 1 part by mass is changed to 1.2 parts by mass of carbon black fine particles. Carrier D was obtained in the same manner as Carrier A. The volume-based 50% particle size (D50) of carrier D was 35.5 μm, and it was a carrier having physical properties as shown in Table 1.

[Manufacture of Carrier E]
1 part by weight of carbon black fine particles (number distribution based maximum peak particle size 30 nm, specific resistance 1.0 × 10 ⁻⁴ Ω · cm), carbon black fine particles (number distribution based maximum peak particle size 45 nm, ratio Carrier E was obtained in the same manner as Carrier A, except that the resistance was changed to 3 parts by mass (9.0 × 10 ⁻⁴ Ω · cm). The volume-based 50% particle size (D50) of Carrier E was 36.2 μm, and it was a carrier having physical properties as shown in Table 1.

[Manufacture of Carrier F]
1 part by mass of carbon black fine particles (maximum peak particle size based on number distribution is 30 nm, specific resistance is 1.0 × 10 ⁻⁴ Ω · cm), fine particles of zinc oxide (maximum peak particle size based on number distribution is 50 nm, ratio Carrier F was obtained in the same manner as carrier A, except that the resistance was changed to 2.5 parts by mass (1.0 × 10 ⁻⁵ Ω · cm). The volume-based 50% particle size (D50) of Carrier F was 36.0 μm, and it was a carrier having physical properties as shown in Table 1.

[Manufacture of carrier G]
1 part by weight of methyl methacrylate macromer having a weight average molecular weight of 5,000 (where n represents the number of repetitions) is 1 part by weight, 197 parts by weight of cyclohexyl methacrylate monomer having an ester moiety is 100 parts by weight, methacrylic acid Carrier G was obtained in the same manner as Carrier A except that 2 parts by mass of methyl monomer was changed to 91 parts by mass. The volume-based 50% particle size (D50) of carrier G was 35.5 μm, and it was a carrier having physical properties as shown in Table 1.

[Manufacture of Carrier H]
1 part by mass of methyl methacrylate macromer having a weight average molecular weight of 5,000 (where n represents the number of repetitions) is 0 part by mass, 197 parts by mass of cyclohexyl methacrylate monomer having an ester moiety is 100 parts by mass, methacrylic acid Carrier H was obtained in the same manner as Carrier A except that 2 parts by mass of methyl monomer was changed to 100 parts by mass. The volume-based 50% particle size (D50) of Carrier H was 35.5 μm, and it was a carrier having physical properties as shown in Table 1.

[Manufacture of Carrier I]
30 parts by mass of the graft copolymer solution was added “10 parts by mass of a monomer or oligomer that forms a polysiloxane in which all organic groups are methyl groups and T units: D units = 90: 10, γ-aminopropyltrimethoxy A coating operation in which the solvent is volatilized while being stirred while being maintained at 70 ° C.
Carrier I was obtained in the same manner as carrier A except that the baking treatment was carried out at 2 ° C. for 2 hours. The volume-based 50% particle size (D50) of Carrier I was 36.0 μm, and it was a carrier having physical properties as shown in Table 1.
The T unit refers to a trifunctional group having one organic group R (here, a methyl group) that forms a bridge (see the following structural formula). The D unit refers to a bifunctional group having two organic groups R (here, a methyl group) (see the following structural formula).

（式中、Ｒはメチル基を表す。）

(In the formula, R represents a methyl group.)

[Manufacture of Carrier J]
A mixture of Fe ₂ O ₃ ; 80 mol%, MnO; 4.0 mol%, MgO; 16 mol% was mixed for 10 hours using a ball mill. The obtained mixture was calcined at 800 ° C. for 2 hours, and the calcined mixture was pulverized with a ball mill. The average particle size of the obtained pulverized product was 0.2 μm.
Water (300% by mass with respect to the pulverized product), polyvinyl alcohol (2% by mass with respect to the pulverized product) and CaCO ₃ (3% by mass with respect to the pulverized product) are added to the obtained pulverized product, and further a spray dryer. Was granulated. The granulated product was sintered at 980 ° C. for 10 hours, then pulverized and further classified to obtain a Mn—Mg ferrite carrier core (J). The average particle diameter (D50) of this Mn—Mg ferrite carrier core was 40 μm.
Subsequently, using 500 parts by mass of the carrier core (J), coating treatment was performed in the same manner as the carrier A, and a carrier J was obtained. The volume-based 50% particle size (D50) of carrier J was 40.0 μm, and it was a carrier having physical properties as shown in Table 1. As shown in FIG. 1, the carrier J broke down before reaching the electric field strength of 2500 V / cm.

[Manufacture of carrier K]
The carrier core of the carrier (I) is used as the carrier core (J), and 1 part by mass of carbon black fine particles (maximum peak particle size based on the number distribution is 30 nm, specific resistance is 1.0 × 10 ⁻⁴ Ω · cm) Except for changing to 1 part by mass of black fine particles (the maximum peak particle size based on the number distribution is 45 nm, the specific resistance is 9.0 × 10 ⁻⁴ Ω · cm),
Carrier K was obtained in the same manner as Carrier I. The volume-based 50% particle size (D50) of carrier K was 40.2 μm, and it was a carrier having physical properties as shown in Table 1.

[Manufacture of carrier L]
Binder resin (styrene / acrylic copolymer) 100 parts by weight Magnetite (number average particle size 300 nm, magnetization strength 68 Am ² / kg, specific resistance 6.0 × 10 ⁵ Ω · cm) 400 parts by weight , Dry-mixed using a Henschel mixer, melt-kneaded with a screw co-rotating twin-screw extruder, then cooled and coarsely crushed with a hammer mill, and collision plate impact pulverizer IDS-2 ) To give a carrier core (L) having a volume-based 50% particle size (D50) of 38.0 μm.
Thereafter, coating was performed in the same manner as carrier I except that no conductive particles were added, and carrier L was obtained. The volume-based 50% particle size (D50) of the carrier L was 38.0 μm, and the carrier had physical properties as shown in Table 1.

[Production of Toner 1]
A mixture of 2.00 mol of styrene, 0.20 mol of 2-ethylhexyl acrylate, 0.14 mol of fumaric acid, 0.03 mol of dimer of α-methylstyrene, and 0.05 mol of dicumyl peroxide was placed in a dropping funnel.
On the other hand, polyoxypropylene (2.2) -2,2-bis (4-hydroxyphenyl) propane 7.00 mol, polyoxyethylene (2.2) -2,2-bis (4-hydroxyphenyl) propane 3. A mixture of 00 mol, 3.00 mol of terephthalic acid, 1.7 mol of trimellitic anhydride, 5.00 mol of fumaric acid, and 0.2 g of titanium terephthalate was placed in a glass 4-liter four-necked flask.
The above-mentioned dropping funnel, thermometer, stirring bar, condenser and nitrogen inlet tube were attached to this four-necked flask, and the four-necked flask was placed in a mantle heater. Next, the temperature of the flask was gradually raised to 145 ° C. while stirring the contents of the flask while flowing nitrogen gas into the four-necked flask. After reaching 145 ° C., the contents of the above dropping funnel were added dropwise over 4 hours. After completion of the dropwise addition, the temperature was raised to 200 ° C. and reacted at the same temperature for 4 hours to obtain a resin 1 having a weight average molecular weight of 78,000 and a number average molecular weight of 3,500.

The following materials / resins 1 100 parts by mass Fischer-Tropsch wax (maximum endothermic peak temperature 80 ° C.) 5.5 parts by mass Aluminum compound 3,5-di-t-butylsalicylate 0.5 parts by mass I. Pigment Blue 15: 3 5 parts by mass

Were mixed with a Henschel mixer (FM-75 type, manufactured by Mitsui Miike Chemical Co., Ltd.), and then kneaded with a biaxial kneader (PCM-30 type, manufactured by Ikekai Tekko Co., Ltd.) set at 130 ° C. The obtained kneaded product was cooled and coarsely pulverized to 1 mm or less with a hammer mill to obtain a coarsely pulverized product. The obtained coarsely crushed material was pulverized using a collision type airflow pulverizer using high-pressure gas. Furthermore, the pulverized product was classified by a multi-division classifier using the Coanda effect to obtain a classified product.
Furthermore, using a hybridizer (manufactured by Nara Machinery Co., Ltd.), the classified product was subjected to surface modification under the conditions of a rotational speed of 6400 rpm, a processing time of 3 minutes, and a processing frequency of 2 times to obtain cyan particles. The weight average particle diameter of the cyan particles was 5.8 μm, and the average circularity was 0.955.
With respect to 100 parts by mass of the obtained cyan particles, 0.5 part by mass of anatase-type titanium oxide fine powder (BET specific surface area 100 m ² / g, treated with 12% by mass of isobutyltrimethoxysilane) and the maximum peak particle based on the number distribution First, 1.5 parts by mass of hydrophobized silica having a diameter of 100 nm was externally added using a Henschel mixer. Further, 1.5 parts by mass of oil-treated silica (BET specific surface area of 200 m ² / g, silicone oil treated by 18% by mass) was additionally charged and externally added with a Henschel mixer to obtain toner 1. The toner 1 had a weight average particle diameter of 5.8 μm and had physical properties as shown in Table 2.

[Production of Toner 2]
3.6 mol of polyoxypropylene (2.2) -2,2-bis (4-hydroxyphenyl) propane, 1.6 mol of polyoxyethylene (2.2) -2,2-bis (4-hydroxyphenyl) propane, 1.7 mol of terephthalic acid, 1.1 mol of trimellitic anhydride, 2.4 mol of fumaric acid, and 0.12 g of titanium terephthalate were placed in a glass 4-liter four-necked flask. A thermometer, a stirring rod, a condenser, and a nitrogen introducing tube were attached to the four-necked flask and placed in a mantle heater. Under a nitrogen atmosphere, reaction was performed at 215 ° C. for 5 hours to obtain a resin 2 having a weight average molecular weight of 30,000 and a number average molecular weight of 4000. A classified product of Resin 2 was obtained in the same manner as in Toner 1.
Further, the obtained classified product was subjected to surface modification by a hybridizer (manufactured by Nara Machinery Co., Ltd.) (rotation speed: 5000 rpm, treatment time: 3 minutes, treatment frequency: 1 time) to obtain cyan particles. The cyan particles had a weight average particle diameter of 6.0 μm and an average circularity of 0.930. Thereafter, the same processing as in the toner 1 was performed to obtain a toner 2.
Toner 2 had a weight average particle diameter of 6.0 μm and was a toner having physical properties as shown in Table 2.

[Production of Toner 3]
The following materials, 90 parts by mass of styrene, 13 parts by mass of n-butyl acrylate, 3 parts by mass of acrylic acid, 6 parts by mass of dodecanethiol and 1 part by mass of carbon tetrabromide were mixed and dissolved to obtain an organic solution.
On the other hand, 1.5 parts by mass of a nonionic surfactant (Sanyo Kasei Co., Ltd .: Nonipol 400) and 2.5 parts by mass of an anionic surfactant (Daiichi Kogyo Seiyaku Co., Ltd .: Neogen SC) , And dissolved in 140 parts by mass of ion-exchanged water in a flask. The organic solution was added to the obtained aqueous solution, dispersed and emulsified, and slowly mixed for 10 minutes.
To the obtained mixture, 10 parts by mass of ion-exchanged water in which 1 part by mass of ammonium persulfate was dissolved was added to perform nitrogen substitution. While stirring the inside of the flask, the content was heated in an oil bath until the temperature reached 70 ° C., and emulsion polymerization was continued as it was for 5 hours to prepare a resin particle dispersion 1. The number average particle diameter of the particles contained in the resin particle dispersion 1 was 0.15 μm.
The following materials, 75 parts by mass of styrene, 25 parts by mass of n-butyl acrylate, and 2 parts by mass of acrylic acid were mixed to obtain an organic solution.
On the other hand, 1.5 parts by mass of a nonionic surfactant (Sanyo Kasei Co., Ltd .: Nonipol 400) and 3 parts by mass of an anionic surfactant (Daiichi Kogyo Seiyaku Co., Ltd .: Neogen SC) An aqueous solution was obtained by dissolving in 150 parts by mass of exchange water in a flask. The organic solution was added to the obtained aqueous solution, dispersed and emulsified, and slowly mixed for 10 minutes.
While mixing, 10 parts by mass of ion-exchanged water in which 0.8 part by mass of ammonium persulfate was further dissolved was added to perform nitrogen substitution. While stirring the inside of the flask, the content was heated in an oil bath until the temperature reached 70 ° C., and emulsion polymerization was continued for 5 hours to prepare a resin particle dispersion 2. The number average particle diameter of the particles contained in the resin particle dispersion 2 was 0.12 μm.
The following materials, paraffin wax (melting point 95 ° C.) 50 parts by mass, anionic surfactant 5 parts by mass (Daiichi Kogyo Seiyaku Co., Ltd .: Neogen SC)
-200 parts by mass of ion-exchanged water mixed and heated to 97 ° C, dispersed using a homogenizer (manufactured by IKA: Ultra Tarrax T50), and further dispersed using a pressure discharge type homogenizer and a release agent A particle dispersion was prepared. The number average particle diameter of the release agent particles in the dispersion was 0.42 μm.
The following materials and C.I. I. Pigment Blue 15: 3 11 parts by mass, anionic surfactant 2 parts by mass (Daiichi Kogyo Seiyaku Co., Ltd .: Neogen SC)
-Ion-exchanged water A colorant dispersion was prepared by dispersing 78 parts by mass using a sand grinder mill.
The following materials obtained by processing as described above: 150 parts by mass of the resin particle dispersion 1 210 parts by mass of the resin particle dispersion 2 210 parts by weight of the colorant dispersion 70 parts by weight of the release agent dispersion 70 The part was put into a reaction vessel equipped with a stirrer, a condenser, and a thermometer and stirred. The mixture was adjusted to pH = 5.4 using 1N potassium hydroxide.
150 parts by mass of a 10% sodium chloride aqueous solution as a flocculant was dropped into the obtained mixed liquid, and the flask was heated to 70 ° C. while stirring in the heating oil bath. While maintaining this temperature, 3 parts by mass of the resin particle dispersion 2 was further added. After maintaining the obtained solution at 60 ° C. for 1 hour, after adding 3 parts by mass of an anionic surfactant (Daiichi Kogyo Seiyaku Co., Ltd .: Neogen SC), the stainless steel reaction vessel was sealed, The mixture was heated to 90 ° C. while continuing stirring using a magnetic seal and held for 3 hours.
After cooling, the reaction product was filtered, and the resulting filtered product was sufficiently washed with ion-exchanged water and then dried to obtain cyan particles. The obtained cyan particles had a weight average particle diameter of 5.7 μm and an average circularity of 0.969. Thereafter, the same processing as in the toner 1 was performed to obtain a toner 3.
The toner 3 had a weight average particle diameter of 5.7 μm and was a toner having physical properties as shown in Table 2.

[Production of Toner 4]
To 710 parts by mass of ion-exchanged water, 450 parts by mass of 0.12M-Na ₃ PO ₄ aqueous solution was added and the aqueous solution obtained by heating to 60 ° C. was obtained using a TK homomixer (manufactured by Tokushu Kika Kogyo). And stirred at 15,000 rpm. This gradually added 1.2M-CaCl ₂ aqueous solution 70 parts by _mass, to obtain an aqueous medium containing Ca 3 _{(PO 4) 2.}
The following materials: 160 parts by mass of styrene 38 parts by mass of n-butyl acrylate Ester wax (maximum endothermic peak temperature 72 ° C.) 20 parts by mass Aluminum compound 3,5-di-t-butylsalicylate 1 part by mass Saturated polyester (terephthalate Acid-propylene oxide modified bisphenol A; acid value 15, peak molecular weight 6000) 10 parts by mass I. Pigment Blue 15: 3 11 parts by mass was heated to 60 ° C., and uniformly dissolved and dispersed at 10,000 rpm using a TK homomixer (manufactured by Tokushu Kika Kogyo Co., Ltd.). In this, 10 parts by mass of a polymerization initiator 2,2′-azobis (2,4-dimethylvaleronitrile) was dissolved to prepare a polymerizable monomer composition.
The obtained polymerizable monomer composition was put into the aforementioned aqueous medium. The obtained mixture was stirred at 15,000 rpm for 10 minutes at 60 ° C. in a nitrogen atmosphere using a TK homomixer to granulate the polymerizable monomer composition. Then, it heated up at 80 degreeC, stirring with a paddle stirring blade, and was made to react for 10 hours. After completion of the polymerization reaction, the remaining monomer was distilled off under reduced pressure. After cooling, hydrochloric acid was added to dissolve Ca ₃ (PO ₄ ) ₂ . The resulting solution was filtered, and the filtered product was washed with water and dried to obtain cyan particles. The weight average particle diameter of the cyan particles was 6.1 μm. Thereafter, the same processing as in the toner 1 was performed to obtain a toner 4. The toner had the physical properties shown in Table 2.

[Production of Toner 5]
560 parts by mass of polyoxypropylene (2.2) -2,2-bis (4-hydroxyphenyl) propane, 250 parts by mass of polyoxyethylene (2.2) -2,2-bis (4-hydroxyphenyl) propane, 300 parts by mass of terephthalic acid and 2 parts by mass of titanium terephthalate were placed in a glass 4-liter four-necked flask. A thermometer, a stirring rod, a condenser and a nitrogen introducing tube were attached to this four-necked flask and placed in a mantle heater. The reaction was carried out at 230 ° C. for 7 hours under a nitrogen atmosphere. Then, it cooled to 160 degreeC, 30 mass parts of phthalic anhydride was added, and it was made to react for 2 hours.
It was then cooled to 80 ° C. A solution prepared by dissolving 180 parts by mass of isophorone diisocyanate in 1000 parts by mass of ethyl acetate (preliminarily heated to 80 ° C.) was put into the above solution and reacted for 2 hours.
Furthermore, it cooled to 50 degreeC, 70 mass parts of isophoronediamine was added, and it was made to react for 2 hours, and the urea modified polyester resin was obtained. The urea-modified polyester resin had a weight average molecular weight of 60,000 and a number average molecular weight of 5,500.
-Urea-modified polyester resin 100 parts by mass-Ester wax (maximum endothermic peak temperature 72 ° C) 5 parts by mass-Aluminum compound 3,5-di-t-butylsalicylate 1 part by mass-C.I. I. Pigment Blue 15: 3 6 parts by mass The above materials are added to 100 parts by mass of ethyl acetate, heated to 60 ° C., and uniformly dissolved and dispersed at 12,000 rpm using a TK homomixer (manufactured by Tokushu Kika Kogyo). did.
On the other hand, 450 parts by mass of 0.12M-Na ₃ PO ₄ aqueous solution was added to 710 parts by mass of ion-exchanged water, heated to 60 ° C., and then TK type homomixer (manufactured by Tokushu Kika Kogyo Co., Ltd.) to Stir at 000 rpm. To the obtained aqueous solution, 68 parts by mass of 1.2M-CaCl ₂ aqueous solution was gradually added to prepare an aqueous medium containing Ca ₃ (PO ₄ ) ₂ .
The above-mentioned dispersion liquid was put into the obtained aqueous medium, and the obtained liquid mixture was granulated by stirring at 15,000 rpm for 10 minutes at 60 ° C. using a TK homomixer. Thereafter, the temperature was raised to 98 ° C. while stirring with a paddle stirring blade, the solvent was removed, and after cooling, hydrochloric acid was added to dissolve Ca ₃ (PO ₄ ) ₂ . The resulting mixture was filtered, and the filtered product was washed with water and dried to obtain particles. The obtained particles were classified by wind to obtain cyan particles. The weight average particle diameter of the cyan particles was 5.9 μm. Thereafter, the same processing as in the toner 1 was performed to obtain a toner 5. The toner had the physical properties shown in Table 2.

[Production of Toner 6]
Toner 6 was obtained in the same manner as toner 1 except that the cyan particles used in toner 1 were subjected to a thermal spheronization treatment. The thermal spheronization treatment was performed using a thermal spheronization apparatus (Nippon Pneumatic Co., Ltd., SFS3 type). The temperature of the atmosphere during the heat spheronization treatment was 270 ° C. The toner 6 had a weight average particle diameter of 6.5 μm, and was a toner having physical properties as shown in Table 2.

[Production of Toners 7 to 9]
7 parts by weight of Pigment Yellow 180 (Toner 7), 8 parts by weight of Pigment Red 122 (Toner 8), 6 parts by weight of carbon black NIpex 60 (manufactured by Degussa) (toner) Toners 7 to 9 were produced in the same procedure as that for the production of toner 1 except that each of 9) was replaced.
The resulting toner 7 (yellow toner) has a weight average particle diameter of 5.7 μm; the toner 8 (magenta toner) has a weight average particle diameter of 5.8 μm; the toner 9 (black toner) has a weight average particle diameter of 5. The toner was 9 μm and had the physical properties shown in Table 2.

Example 1
To 92 parts by mass of carrier A obtained above, 8 parts by mass of toner 1 is added and mixed in a normal temperature and normal humidity (23 ° C., 50% RH) environment using a V-type mixer, and two-component developer 1 It was.
Using this two-component developer, image evaluation was performed under normal temperature and low humidity (23 ° C., 5% RH) using a Canon full color copier CLC5000 remodeling machine.
That is, 100,000 images were output (durability) using a chart with an image area of 30% in the above environment, and image evaluation before and after durability was performed. The modified CLC5000 machine is as follows. (1) The laser spot diameter was narrowed so that it could be output at 600 dpi. (2) The surface layer of the fixing roller of the fixing unit was changed to a PFA tube, and the oil application mechanism was removed.
The development conditions for image evaluation are as follows. The developing sleeve and the photosensitive member were rotated in the forward direction in the developing region. The rotation speed of the developing sleeve was 1.90 times the rotation speed of the photoconductor. A dark portion potential Vd−600 V, a light portion potential Vl−110 V, a direct current / alternating current electric field (direct current potential Vdc−450 V, alternating current rectangular wave electric field Vpp 0.8 V, frequency 1.3 kHz).
When the following items were evaluated at the initial stage of image output and 100,000 sheets, a cyan image that faithfully reproduced an original without fogging was formed even after endurance. In addition, the image density was stable and high even after the endurance. Also, the level of roughness of the HT image was good before and after endurance. The evaluation results are shown in Table 3. The HT image is a halftone image when the density is the 48th density in 256 gradation display where 0 is solid white and 256 is solid black.

The image evaluation items and evaluation criteria are shown below.
(1) Image density Using the above-mentioned CLC5000 (Canon) remodeling machine, using a normal copying machine plain paper (75 g / m ² ) transfer material, a solid image is output at the end of durability evaluation in the image output test. Then, the concentration was evaluated by measuring. The image density was measured by using a “Macbeth reflection densitometer RD918” (manufactured by Macbeth Co., Ltd.) to measure the relative density with respect to an image of a white background portion having a document density of 0.00. The evaluation results are shown in Table 3.
(Evaluation criteria)
A: Very good 1.40 or more B: Good 1.35 or more, less than 1.40 C: No problem in practical use 1.00 or more, less than 1.35 D: Somewhat difficult Less than 1.00

(2) Dot reproducibility A dot image in which one pixel is formed by one dot was created. The spot diameter of the laser beam of the CLC5000 was adjusted so that the area per one dot of paper was 20000 or more and 25000 μm ² or less. The area of 1000 dots was measured using a digital microscope VHX-500 (lens wide range zoom lens VH-Z100, manufactured by Keyence Corporation).
The number average (S) of dot areas and the standard deviation (σ) of dot areas were calculated, and the dot reproducibility index was calculated by the following formula. The evaluation results are shown in Table 3.
(Formula) Dot reproducibility index (I) = σ / S × 100
(Evaluation criteria)
A: I is less than 4.0. Very good image B: I is 4.0 or more and less than 6.0. Good image C: I is 6.0 or more and less than 8.0. No practical problem D: I is 8.0 or more. bad

(3) Carrier adhesion Using the above-mentioned CLC5000 (Canon) modified machine, a solid white image is printed on the plain paper (75 g / m ² ) and Vd is changed every 50V so that Vback is 0V or more and 300V or less. I put it out. After printing a solid white image with each Vback, the part on the photosensitive drum between the developing unit and the cleaner unit is sampled by attaching a transparent adhesive tape, and is adhered to the photosensitive drum in 1 cm × 1 cm. The number of magnetic carrier particles that had been counted was counted, and the number of adhered carriers per 1 cm ² was calculated. Carrier adhesion was evaluated according to the following evaluation criteria. Table 3 shows the evaluation when Vback = 150V.
(Evaluation criteria)
A: Less than 10 per 1 cm ² B: 10 or more per 1 cm ² , less than 20 C: 20 or more per 1 cm ² , less than 50 (Practical level so far)
D: 50 or more per 1 cm ² , less than 100 E: 100 or more per 1 cm ²

(4) <Outline evaluation>
Using the CLC5000 (Canon) modified machine, a chart in which halftone horizontal bands (30H width 10 mm) and solid black horizontal bands (FFH width 10 mm) are alternately arranged in the transfer paper conveyance direction is output. The image is read by a scanner and binarized. Taking the luminance distribution (256 gradations) of a certain line in the conveyance direction of the binarized image, drawing a tangent to the luminance of the halftone at that time, and deviating from the tangent at the rear end of the halftone part until it intersects with the solid part luminance The brightness area (area: sum of the brightness numbers) is used as the whiteness degree. The evaluation criteria are as follows.
A: 50 or less, hardly noticeable and very good.
B: 51 to 150, good.
C: 151 to 300, white spots are present but at a level that is not problematic in practice.
D: From 301 to 600, white spots are conspicuous, which is a problem.
E: 601 or more, very noticeable.

(5) Fogging measurement Using the above CLC5000 (manufactured by Canon Inc.), an original document with an image area ratio of 5% in a single color mode under a normal temperature and low humidity environment (23 ° C./5%) was used for initial and 100,000 sheet durability tests. Evaluate.
In the durability test, the method for measuring fog is as follows. First, in the case of a cyan image, the average reflectance Dr (%) of plain paper before image printing is measured with a reflectometer (“REFECTOMETER MODEL TC-6DS” manufactured by Tokyo Denshoku Co., Ltd.) equipped with an amber filter. . On the other hand, a solid white image is drawn on plain paper, and then the reflectance Ds (%) of the solid white image is measured. Using these measured values, fog (Fog [%]) is obtained by the following formula (2).
Fog [%] = Dr [%] − Ds [%] (2)
(Evaluation criteria)
A: Less than 0.7%, excellent B: 0.7 or more, less than 1.2%, good C: 1.2 or more, less than 1.5%, no practical problem
D: 1.5 or more and less than 2.0%, there are practical problems
E: It is bad at 2.0% or more

(Examples 2 to 14 and Comparative Examples 1 to 3)
As shown in Table 3, the same evaluation as in Example 1 was performed except that the types of the magnetic carrier and the toner were changed. The evaluation results are shown in Table 3.

(Examples 15 to 17)
Using a Canon full color copier CLC5000 remodeling machine (all developing stations were remodeled in the same way as in Example 1 and all developing conditions were the same as in Example 1), each developer was set in each color station. The durability test was conducted in the same manner as in Example 1. The evaluation was performed in a single color in the same manner as in Example 1. The results are as shown in Table 3. Moreover, as a result of outputting a full-color image after endurance of 100,000 sheets, a product having an image quality almost comparable to the initial image was obtained.

The range of the dynamic resistivity of the magnetic carrier of the present invention is shown. 1 is a schematic cross-sectional view showing an example of an image forming apparatus that can suitably implement the present invention. The schematic diagram of the measuring apparatus of the dynamic resistivity of the magnetic carrier of this invention is shown. Schematic sectional view of an apparatus for measuring the specific resistance value of a magnetic carrier, a nonmagnetic inorganic compound and a magnetic component

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Drive roller 2 Follower roller 3 Secondary transfer counter roller 4 Secondary transfer roller 5 Belt cleaning device 6 Paper cassette 7a to 7d Electrostatic latent image carrier 8a to 8d Charging device 9a to 9d Image exposure device 10a to 10d Developer container 11a To 11d Cleaning device 12a to 12d Process cartridge 13 Primary transfer roller 14 Intermediate transfer belt 15 Fixing device 16 Paper feed roller 41 Lower electrode 42 Upper electrode 43 Insulator 44 Ammeter 45 Voltmeter 46 Constant voltage device 47 Carrier 48 Guide ring E Resistance Measurement cell L Sample thickness P Transfer material

Claims (5)

A magnetic carrier having a magnetic carrier core containing at least a magnetic component and a resin component, and a resin coating layer covering the surface of the magnetic carrier core,
The true density of the magnetic carrier is 2.5 g / cm ³ or more and 4.2 g / cm ³ or less,
The dynamic resistivity R2500 of the magnetic carrier at an electric field strength of 2500 V / cm is 5.0 × 10 ⁵ Ωcm or more and 1.0 × 10 ⁸ Ωcm or less, and the dynamic resistivity R5000 at an electric field strength of 5000 V / cm is 1. A magnetic carrier characterized by being not less than 0 × 10 ⁵ Ωcm and not more than 5.0 × 10 ⁷ Ωcm.   The resin coating layer contains conductive fine particles, and the conductive fine particles include one or more conductive fine particles selected from the group consisting of carbon black fine particles, magnetite fine particles, graphite fine particles, titanium oxide fine particles, and alumina fine particles. The magnetic carrier according to claim 1, comprising two or more kinds. The resin forming the resin coating layer contains a polymer containing a unit formed from a monomer represented by the following formula (A1), and the proportion of the unit in the polymer is 80% by mass or more. The magnetic carrier according to claim 1, wherein the magnetic carrier is a magnetic carrier.

(Wherein R ¹ represents a hydrocarbon group having 1 to 25 carbon atoms)   A two-component developer containing the magnetic carrier according to any one of claims 1 to 3 and a toner.   A charging step for uniformly charging the surface of the electrostatic latent image carrier, an exposure step for exposing the surface of the electrostatic latent image carrier to form an electrostatic latent image, and a surface formed on the surface of the electrostatic latent image carrier The electrostatic latent image is developed using a two-component developer to form a toner image, the transfer step for transferring the toner image onto a transfer material, and the toner image on the transfer material is fixed. An image forming method including a fixing step, wherein the two-component developer is the two-component developer according to claim 4.

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