JP2011164230A - Resin coated carrier, method for producing the same, and two-component developer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a resin coated carrier achieving a long life of the carrier and low power consumption by decrease in an agitation torque and capable of stably charging toner even when the number of sheets for printing increases, and to provide a method for producing the resin coated carrier, and a two-component developer containing the resin coated carrier. <P>SOLUTION: The resin coated carrier comprises a carrier core material, a resin coating layer formed on the surface of the carrier core material, and nitrogen-containing crosslinked resin fine particles. The carrier core material comprises a porous material having pores on the surface and has an apparent density of 1.6 g/cm<SP>3</SP>or more and 2.0 g/cm<SP>3</SP>or less. The nitrogen-containing crosslinked resin fine particles satisfy expression (1):(Db+0.3 μm)≥Da>Db, wherein Da (μm) represents the volume average particle diameter of the fine particles and Db (μm) represents the area average diameter of the pores. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a resin-coated carrier, a method for producing the same, and a two-component developer.

  With the recent remarkable development of OA (Office Automation) equipment, image forming apparatuses such as copiers, printers, and facsimile machines that perform image forming processing using an electrophotographic system have become widespread.

  In an image forming apparatus using such an electrophotographic system, for example, a charging process, an exposure process, a development process, a transfer process, a fixing process, and a cleaning process are performed in order to form an image. In the charging step, the surface of the photoconductor as an image carrier is uniformly charged in a dark place. In the exposure step, the signal light of the original image is projected onto the charged photoconductor to remove the charge at the exposed portion and form an electrostatic image (electrostatic latent image) on the surface of the photoconductor. In the development step, an electrostatic image developing toner (hereinafter simply referred to as “toner” unless otherwise specified) is supplied to the electrostatic image on the surface of the photoreceptor to form a toner image (visible image). In the transfer step, the toner image on the surface of the photoreceptor is transferred to the recording medium by applying a charge having a polarity opposite to that of the toner to the recording medium. In the fixing step, the toner image on the recording medium is fixed by means such as heating and pressing. In the cleaning process, the toner remaining on the surface of the photoreceptor without being transferred to the recording medium is collected. An image forming apparatus using an electrophotographic system forms a desired image on a recording medium through the above steps.

  In an image forming apparatus using an electrophotographic system, a one-component developer containing only toner or a two-component developer containing toner and carrier is used as a developer for developing a toner image. In the two-component developer, the carrier has functions of stirring, transporting and charging the toner. Therefore, in the two-component developer, the toner does not need to have both of these functions, and the functions of the toner and the carrier are separated. Therefore, the two-component developer is more controlled than the one-component developer containing the toner alone. Characteristics are improved, and high-quality images are easily obtained.

  The carrier function includes two basic functions: a function of stably charging the toner to a desired charge amount, and a function of transporting the toner to the photoreceptor. The carrier is stirred in the developing tank, conveyed onto the magnet roller, forms a magnetic spike, passes through the regulating blade, returns to the developing tank again, and is repeatedly used. The carrier is required to develop a stable basic function, particularly to stably charge the toner, as it is continuously used. In order to ensure charging stability, a resin-coated carrier in which the surface of the carrier core material is coated with a resin coating layer has been developed.

  However, in general, since the carrier has a high density and a large stirring torque, the share applied to the carrier during stirring is large, so that the resin coating layer is scraped, and the charge imparting ability of the carrier to the toner is reduced accordingly. Is a problem. Further, in order to stir the carrier in the developing tank, a large amount of driving power is required.

  In response to such a problem, improvement of the carrier aiming at extending the life of the developer and reducing the power consumption of the image forming apparatus is underway.

  With regard to prolonging the life of the developer, Patent Document 1 discloses that the charge amount to the toner is not reduced in order to prevent the charge amount imparting ability of the carrier from being applied to the toner even if the resin coating layer of the carrier progresses. A carrier in which nitrogen-containing fine particles having high imparting ability are contained in a matrix resin is disclosed.

  With regard to reducing the power consumption of the image forming apparatus, many studies have been made to reduce the carrier density in order to reduce the stirring torque of the developing tank to reduce the power consumption. Patent Documents 2 and 3 disclose a carrier core material in which a void is provided, the carrier core material is filled with resin to reduce the density, and the carrier core material surface is coated with a silicone resin. Has been.

JP 2001-51451 A JP 2006-337579 A JP 2007-57943 A

  However, in the carrier disclosed in Patent Document 1, since the nitrogen-containing fine particles are uniformly dispersed in the matrix resin, the nitrogen-containing fine particles are detached when the resin coating layer is peeled or worn over a long period of use. There is a concern that adhesion to the toner may destabilize the charge amount of the toner and cause image defects.

  In the carriers disclosed in Patent Documents 2 and 3, since a large amount of resin is required to fill the voids inside the carrier core material, there is a problem that the cost increases accordingly. In addition, it is difficult to control the thickness of the resin coating layer that covers the surface of the carrier core material. Furthermore, the addition of a resin that fills the voids inside the carrier core material makes it easier for carrier particles to adhere to each other, resulting in a uniform resin coating. There is a problem that it cannot be formed. A resin-coated carrier with a non-uniform thickness of the resin coating layer formed on the surface of the carrier core material wears the resin coating layer non-uniformly by stirring in the developing tank, so that the toner can be stably charged. Can not.

  The object of the present invention is to suppress the non-uniform thickness of the resin coating layer formed on the surface of the carrier core made of a porous material, and to reduce the consumption by extending the life of the carrier and reducing the stirring torque. An object of the present invention is to provide a resin-coated carrier capable of realizing electric power and stably charging a toner even when the number of printed sheets is increased, a manufacturing method thereof, and a two-component developer including the resin-coated carrier.

The present invention is a resin-coated carrier having a carrier core material, a resin coating layer formed on the surface of the carrier core material, and nitrogen-containing crosslinked resin fine particles,
The carrier core material is made of a porous material having pores on the surface, and the apparent density is 1.6 g / cm ³ or more and 2.0 g / cm ³ or less,
The nitrogen-containing crosslinked resin fine particles satisfy the following formula (1) when the volume average particle diameter is Da (μm) and the area average diameter of the pores is Db (μm). It is a career.
(Db + 0.3 μm) ≧ Da> Db (1)

Further, the invention is characterized in that the resin coating layer contains conductive particles.
Further, the present invention is characterized in that the resin coating layer contains magnetite having a volume average particle diameter of 0.3 μm or more and 1.0 μm or less.

The present invention is also characterized in that the volume average particle size is 25 μm or more and 50 μm or less.
In the present invention, the ratio of the total projected area of the nitrogen-containing crosslinked resin fine particles to the total surface area of the carrier core material is 10% or more and 30% or less.

The present invention also provides a method for producing the resin-coated carrier described above,
Addition of nitrogen-containing cross-linked resin fine particles for attaching nitrogen-containing cross-linked resin fine particles to the surface of a carrier core material made of a porous material having pores on the surface and having an apparent density of 1.6 to 2.0 g / cm ³ Process,
A coating step of forming a resin coating layer by coating a carrier core material having the nitrogen-containing crosslinked resin fine particles attached to the surface obtained in the nitrogen-containing crosslinked resin fine particle addition step;
The carrier core material and the nitrogen-containing crosslinked resin fine particles used in the step of adding the nitrogen-containing crosslinked resin fine particles have a volume average particle diameter of the nitrogen-containing crosslinked resin fine particles as Da (μm) and an area average diameter of the pores as Db ( [mu] m), a method for producing a resin-coated carrier characterized by satisfying the above formula (1).

  The present invention also provides a two-component developer comprising the resin-coated carrier described above and a toner containing a binder resin and a colorant.

According to the present invention, there is provided a resin-coated carrier having a carrier core material, a resin coating layer formed on the surface of the carrier core material, and nitrogen-containing crosslinked resin fine particles, wherein the carrier core material has pores on the surface. The apparent density is 1.6 g / cm ³ or more and 2.0 g / cm ³ or less. The resin coating layer contains nitrogen-containing crosslinked resin fine particles, and the nitrogen-containing crosslinked resin fine particles have a volume average particle diameter of Da (μm) and an area average diameter of the pores of Db (μm). The resin-coated carrier that satisfies the above formula (1). Therefore, the pores are blocked by the nitrogen-containing crosslinked resin fine particles, and the resin constituting the resin coating layer can be prevented from being transferred to and impregnated into the voids inside the carrier core material of the porous material. Further, since the nitrogen-containing crosslinked resin fine particles are buried in the pores, the nitrogen-containing crosslinked resin fine particles can be prevented from being detached even if the resin coating layer is scraped over a long period of use. As a result, it is possible to form a resin coating layer having a uniform thickness on the surface of the carrier core material in which the pores formed on the surface are closed by the nitrogen-containing crosslinked resin fine particles. It is possible to obtain a resin-coated carrier that achieves low power consumption by reduction and can stably charge the toner even when the number of printed sheets increases.

  According to the invention, since the resin coating layer contains conductive particles, it is possible to improve the charge imparting property of the resin-coated carrier to the toner.

  According to the invention, since the resin coating layer contains magnetite having a volume average particle diameter of 0.3 μm or more and 1.0 μm or less, the action of the resin-coated carrier as a developing electrode is improved, and the edge effect is suppressed. High-quality images can be formed. Moreover, the magnetic force of the resin-coated carrier can be increased and carrier adhesion can be reduced.

  According to the present invention, since the volume average particle diameter of the resin-coated carrier is 25 μm or more and 50 μm or less, carrier adhesion can be suppressed, image quality can be prevented from being lowered, and toner holding ability is high. Deterioration of the graininess of the formed image due to the toner can be suppressed. Therefore, a high-definition high-quality image can be formed.

  According to the present invention, since the ratio of the total projected area of the nitrogen-containing crosslinked resin fine particles to the total surface area of the carrier core material is 10% or more and 30% or less, the pores of the carrier core material can be suitably closed. In addition, since aggregation of the resin fine particles can be suppressed, a uniform resin coating layer can be formed on the surface of the carrier core material.

  According to the present invention, the method for producing a resin-coated carrier includes a nitrogen-containing crosslinked resin fine particle in which nitrogen-containing crosslinked resin fine particles are adhered to the surface of a carrier core material composed of a porous material having pores formed on the surface. An addition step, and a coating step obtained by coating the carrier core material with the nitrogen-containing crosslinked resin fine particles attached to the surface, which is obtained in the nitrogen-containing crosslinked resin fine particle addition step, to form a resin coating layer. The carrier core material and the nitrogen-containing crosslinked resin fine particles used in the step of adding the nitrogen-containing crosslinked resin fine particles have a volume average particle diameter of the nitrogen-containing crosslinked resin fine particles as Da (μm) and the area average diameter of the pores. When Db (μm) is satisfied, the above formula (1) is satisfied. Therefore, it is possible to obtain a carrier core material whose pores are blocked by nitrogen-containing crosslinked resin fine particles, and the pores formed on the surface have a thickness on the surface of the carrier core material closed by nitrogen-containing crosslinked resin particles. A uniform resin coating layer can be formed. As a result, it is possible to obtain a resin-coated carrier that realizes a long life of the carrier and low power consumption by reducing the stirring torque, and can stably charge the toner even when the number of printed sheets increases.

  According to the invention, since the two-component developer is composed of the resin-coated carrier and the toner containing the binder resin and the colorant, the two-component developer having a stable charge amount even when the number of printed sheets is increased. It can be used as a developer, can reproduce images with high definition, has good color reproducibility, high image density, and stably forms high-quality images without image defects such as fogging over a long period of time. Can do.

It is a figure which shows the structure of the resin coating carrier 50 which is one Embodiment of this invention. 1 is a diagram illustrating a configuration of a developing device 20 according to an embodiment of the present invention.

1. Resin-coated carrier FIG. 1 is a diagram showing a configuration of a resin-coated carrier 50 according to an embodiment of the present invention. The resin-coated carrier 50 is used for an electrophotographic developer that develops an electrostatic latent image formed on a photoconductor, which is an image carrier, and visualizes the toner. Two basic functions, i.e., a function of stably charging toner and a function of transporting toner to the photoreceptor. The resin-coated carrier 50 includes a carrier core material 51 and a resin coating layer 52 formed on the surface of the carrier core material 51.

(1) Carrier Core Material A carrier core material 51 constituting the resin-coated carrier 50 of the present embodiment is composed of a porous material in which voids 51b are formed and pores 51a are formed on the surface. The hanging density is 1.6 g / cm ³ or more and 2.0 g / cm ³ or less. In the resin-coated carrier 50 of the present embodiment, pores 51a (hereinafter referred to as “surface pores 51a”) formed on the surface of the carrier core material 51 are nitrogen-containing bridges contained in the resin coating layer 52 described later. The opening is closed by the resin fine particles 53.

A resin-coated carrier including a carrier core material having an apparent density of 2.0 g / cm ³ or less can reduce the driving torque of a magnet roller or the like in the developing tank during the stirring, thereby saving power. . Furthermore, the toner and the resin-coated carrier are constantly stirred inside the developing tank during development, but if the apparent density is sufficiently small, the stirring stress on the resin-coated carrier and the wear of the resin-coated layer are reduced. Even if the number of printed sheets increases, a resin-coated carrier that can give a stable charge amount to the toner can be obtained. Further, since the carrier core material 51 having an apparent density of 1.6 g / cm ³ or more does not have an excessively large area average diameter of the surface pores, the nitrogen-containing crosslinked resin fine particles contained in the resin coating layer 52 The resin-coated carrier 50 in which the surface pores are sufficiently blocked by 53 can be obtained.

  In the resin-coated carrier 50 of the present embodiment, the surface pores 51a of the carrier core material 51 are formed so that the area ratio is 5% or more and 30% or less. Here, the area ratio is the ratio of the total area of the surface pores to the total surface area of the carrier core material. The surface pores 51a are formed so that the area average diameter is 0.3 μm or more and 1.0 μm or less. Here, the area average diameter of the surface pores means that, in the cumulative area distribution obtained by integrating the surface pores formed on the surface of the carrier core material from the small diameter side, the area percentage of the cumulative area with respect to all the surface pores is 50%. The equivalent circle diameter. When the surface pore area ratio is less than 5%, a carrier core material having a sufficiently small apparent density cannot be obtained. Further, when the surface pore area ratio exceeds 30% or the area average diameter exceeds 1 μm, the resin-coated carrier in which the surface pores are sufficiently blocked by the nitrogen-containing crosslinked resin fine particles contained in the resin coating layer It can not be.

  As the carrier core material 51, those commonly used in this field can be used. For example, magnetic metals such as iron, copper, nickel and cobalt, and magnetic oxides such as ferrite and magnetite can be used.

Ferrite as a magnetic oxide is a group of iron oxides generally having a composition of MO · Fe ₂ O _3, and a powder of metal oxide (MO) containing divalent metal ions and iron oxide is mixed, It is obtained by firing after compression molding. Examples of M include divalent metal ions such as Fe ²⁺ , Mn ²⁺ , Mg ²⁺ , Co ²⁺ , Ni ²⁺ , Cu ²⁺ , and Zn ²⁺ . The metal oxide may be one type or two or more types. When the metal oxide has a mixed composition, the controllable range of magnetic characteristics in the carrier core material 51 is widened.

As a raw material of the metal oxide (MO), Fe ₂ O ₃ is suitable if it is a metal oxide containing Fe ²⁺ . MnCO ₃ is suitable as long as it is a metal oxide containing Mn ²⁺ , but Mn ₃ O ₄ or the like may be used. As the metal oxide containing Mg ²⁺ , MgCO ₃ and Mg (OH) ₂ are preferable.

  The ferrite includes soft ferrite exhibiting soft magnetism and hard ferrite exhibiting hard magnetism. The ferrite used in the present embodiment is preferably soft ferrite. Since hard ferrite is a magnet, it has a large residual magnetization, and when hard ferrite is used as the magnetic oxide, resin-coated carrier particles adhere to each other and fluidity as a developer decreases, or the resin-coated carrier is a magnet. There is a risk that it will be difficult to leave the roller. On the other hand, since soft ferrite can reduce the remanent magnetization to 10 emu / g or less, when soft ferrite is used as a magnetic oxide, it has good fluidity as a developer and can obtain a resin-coated carrier that is easily separated from a magnet roller or the like. Can do.

(2) Resin Coating Layer The resin coating layer 52 is a layer formed so that the resin coating composition covers the surface of the carrier core material 51, and contains nitrogen-containing crosslinked resin fine particles 53. Examples of the nitrogen-containing crosslinked resin fine particles include melamine resin fine particles and benzoguanamine resin fine particles. The resin coating composition constituting the resin coating layer 52 is selected from cross-linked silicone resins, and additives such as conductive particles, amino group-containing silane coupling agents, resins other than silicone resins, and bifunctional silicone oils as necessary. 1 type or 2 types or more mixed.

The nitrogen-containing crosslinked resin fine particles 53 are contained in the resin coating layer 52 so as to block the surface pores 51 a of the carrier core material 51, and the volume average particle diameter Da (μm) thereof is that of the surface pores 51 a of the carrier core material 51. When the area average diameter is Db (μm), the following formula (1) is satisfied.
(Db + 0.3 μm) ≧ Da> Db (1)

  At this time, in the resin-coated carrier 50, the total of the opened surface pores 51a (surface pores not blocked by the nitrogen-containing crosslinked resin fine particles) after the addition of the nitrogen-containing crosslinked resin fine particles 53 with respect to the total surface area of the carrier core material 51 is achieved. Nitrogen-containing crosslinked resin fine particles 53 so that the area ratio P1 ((total area of open surface pores 51a after addition of nitrogen-containing crosslinked resin fine particles 53 / total surface area of carrier core material) × 100) is 5% or less. Closes the surface pores 51 a of the carrier core material 51.

  When the ratio P1 (hereinafter referred to as “opening surface pore ratio P1”) exceeds 5%, a resin-coated carrier in which the surface pores are sufficiently blocked by the nitrogen-containing crosslinked resin fine particles cannot be obtained.

  The opening surface pore ratio P1 is calculated as follows. First, the carrier core material after the addition of the nitrogen-containing crosslinked resin fine particles is photographed with an electron microscope (trade name: VE-9500, manufactured by Keyence Corporation) at a magnification of 1000 times. Next, an area of ½ of the radius of the carrier core material from the center of the carrier core material is trimmed from the photograph, and the carrier core is imaged from that area by image analysis software (trade name: A Image-kun, manufactured by Asahi Kasei Engineering Co., Ltd.). By extracting and analyzing the contours of the surface pores of the material, the total area of the surface pores not blocked by the nitrogen-containing crosslinked resin fine particles is calculated. Such analysis is performed on the carrier core material 50 particles after the addition of the nitrogen-containing crosslinked resin fine particles, and the average value is defined as the total surface pore area not blocked by the nitrogen-containing crosslinked resin fine particles. Then, the area of the trimmed region is defined as the total surface area of the carrier core material, and the ratio P1 of the opening surface pores to the total surface area is calculated.

  In the resin-coated carrier 50, the ratio P2 of the total projected area of the nitrogen-containing crosslinked resin fine particles 53 to the total surface area of the carrier core material 51 (sum of the projected areas of all nitrogen-containing crosslinked resin fine particles) The nitrogen-containing crosslinked resin fine particles are preferably added to the resin coating layer so that the total projected area / total surface area of the carrier core material) × 100) is 10% or more and 30% or less. When the ratio P2 (hereinafter referred to as “resin fine particle addition ratio P2”) is less than 10%, the surface pores cannot be sufficiently blocked by the nitrogen-containing crosslinked resin fine particles. On the other hand, when the resin fine particle addition ratio P2 exceeds 30%, aggregation of the nitrogen-containing crosslinked resin fine particles occurs, and a uniform resin coating layer cannot be formed.

  The resin fine particle addition ratio P2 is calculated as follows. First, the surface area (or projected area) per particle is calculated from the radius (1/2 of the volume average particle diameter) of the nitrogen-containing crosslinked resin fine particles. Further, the number of added particles of the nitrogen-containing crosslinked resin fine particles relative to the carrier core material is calculated from the radius of the nitrogen-containing crosslinked resin fine particles, the apparent density of the carrier core material, and the added weight of the nitrogen-containing crosslinked resin fine particles. Then, the total projected area of the nitrogen-containing crosslinked resin fine particles is calculated from the surface area per particle of the nitrogen-containing crosslinked resin fine particles calculated as described above and the number of added particles of the nitrogen-containing crosslinked resin fine particles with respect to the carrier core material. Further, the resin fine particle addition ratio P2 is calculated from this value.

  As described above, since the nitrogen-containing crosslinked resin fine particles 53 are contained in the resin coating layer 52 so as to satisfy the formula (1) and close the surface pores 51a of the carrier core material 51, the resin coating layer 52 is configured. It is possible to prevent the resin in the resin coating composition from being transferred to and impregnated into the void 51b inside the carrier core material 51 of the porous material. Further, since the nitrogen-containing crosslinked resin fine particles 53 are buried in the surface pores 51a of the carrier core material 51, the separation of the nitrogen-containing crosslinked resin fine particles 53 can be prevented even during long-term use. Therefore, the thickness of the resin coating layer 52 formed on the surface of the carrier core material 51 is prevented from becoming uneven, and the resin coating layer is uniformly worn by stirring in the developing tank, and the nitrogen-containing cross-linking is performed. Since the resin fine particles are not detached, a resin-coated carrier capable of stably charging the toner can be obtained.

  The volume average particle diameter Da of the nitrogen-containing crosslinked resin fine particles 53 is set to 0.3 μm or more and 1.0 μm or less. When the volume average particle diameter Da of the nitrogen-containing crosslinked resin fine particles is less than 0.3 μm, the surface pores formed on the surface of the carrier core material cannot be sufficiently blocked. Further, when the volume average particle diameter Da of the nitrogen-containing crosslinked resin fine particles exceeds 1.0 μm, aggregation of the nitrogen-containing crosslinked resin fine particles occurs, and a uniform resin coating layer cannot be formed.

  The resin coating layer 52 may contain conductive particles as a conductive material. This improves the charge imparting property of the resin-coated carrier 50 to the toner. Examples of the conductive particles include conductive carbon black, oxides such as conductive titanium oxide and tin oxide. In order to develop conductivity with a small addition amount, conductive carbon black is preferable. However, for the color toner, there is a concern that carbon may be detached from the resin coating layer 52 of the resin-coated carrier 50. In such a case, conductive titanium oxide doped with antimony is preferable.

  Further, the resin coating layer 52 may contain magnetite. The volume average particle diameter of magnetite is preferably 0.3 μm or more and 1.0 μm or less. As a result, the action of the resin-coated carrier 52 as a developing electrode is enhanced, the edge effect is suppressed, and a high-quality image can be formed. Moreover, the magnetic force of a carrier can be raised and carrier adhesion can be suppressed. When the volume average particle diameter of the magnetite is less than 0.3 μm, it is difficult to obtain an appropriate effect as a developing electrode, and when the volume average particle diameter exceeds 1.0 μm, the magnetites tend to aggregate and become uniform. A resin coating layer cannot be formed.

(3) Resin-coated carrier The resin-coated carrier 50 having the resin coating layer 52 formed on the surface of the carrier core material 51 preferably has a volume average particle diameter of 25 μm or more and 50 μm or less. When the volume average particle diameter of the resin-coated carrier is 25 μm or more, carrier adhesion, which is a phenomenon in which the carrier itself adheres to an image carrier on which an electrostatic latent image is formed, is suppressed, and deterioration of image quality is prevented. Can do. Further, when the volume average particle diameter of the resin-coated carrier is 50 μm or less, the toner holding ability is high, and the deterioration of the granularity of the formed image by the toner can be suppressed. Therefore, when the volume average particle diameter of the resin-coated carrier 50 is within this range, a high-definition high-quality image can be formed.

  Further, in the resin-coated carrier 50 according to the present embodiment, the resin is not filled in the gap 51 b formed inside the carrier core material 51. Therefore, compared to a resin-coated carrier in which the voids formed inside the carrier core material are filled with resin, the amount of resin used can be reduced, and carrier particles can be produced by using a large amount of resin during production. Adhesion can be suppressed. In addition, the manufacturing cost can be reduced.

(4) Manufacturing method of resin-coated carrier The manufacturing method of the resin-coated carrier of the present embodiment includes a weighing process, a mixing process, a pulverizing process, a granulating process, a calcining process, a baking process, and a crushing process. And a classification step, a nitrogen-containing crosslinked resin fine particle addition step, and a coating step.

[Weighing process, mixing process]
In this step, raw materials of the carrier core material 51 such as magnetic oxide are weighed and mixed to obtain a metal raw material mixture. When two or more kinds of magnetic oxides are used, the blending ratio of the two or more kinds of magnetic oxides is weighed so as to match the intended composition of the magnetic oxide.

Next, resin particles are added to the metal raw material mixture. Examples of the resin particles added here include carbon-based resin particles such as polyethylene and acrylic, and resin particles containing silicone such as silicone resin (hereinafter referred to as “silicone-based resin particles”). The carbon-based resin particles and the silicone-based resin particles are the same in that they are burned in a calcining step described later, and a hollow structure is generated in the calcined powder by a gas generated during combustion. However, the carbon-based resin particles only generate a hollow structure in the calcined powder after combustion, but the silicone-based resin particles become SiO ₂ after combustion and remain in the generated hollow structure.

  The volume average particle diameter of the resin particles added to the metal raw material mixture is preferably 2 μm or more and 8 μm or less. The amount of resin particles added is preferably 0.1 wt% or more and 20 wt% or less with respect to the total amount of raw materials of the carrier core material 51. Here, by adjusting the addition amount of the resin particles, the area average diameter of the surface pores 51 a formed in the carrier core material 51 and the area ratio with respect to the total surface area of the carrier core material 51 can be controlled.

[Crushing process]
In this step, the metal raw material mixture and the resin particles are put into a pulverizer such as a vibration mill and pulverized until the volume average particle diameter is 0.5 μm or more and 2.0 μm or less, preferably 1 μm. Next, water, 0.5 to 2 wt% binder, and 0.5 to 2 wt% dispersant are added to the pulverized product to form a slurry with a solid content concentration of 50 to 90 wt%. Etc. Wet pulverize. Here, polyvinyl alcohol or the like is preferable as the binder, and ammonium polycarboxylate or the like is preferable as the dispersant.

[Granulation process]
In this step, the slurry pulverized wet in the above step is sprayed and dried in hot air at 100 ° C. to 300 ° C. using a spray dryer to obtain a granulated powder having a volume average particle size of 10 μm to 200 μm. In consideration of the volume average particle diameter of the resin-coated carrier produced by this production method, the obtained granulated powder is adjusted in particle size by excluding coarse particles and fine powder that deviate from it using a vibration sieve. Specifically, since the volume average particle diameter of the resin-coated carrier 50 is preferably 25 μm or more and 50 μm or less, it is preferable to adjust the volume average particle diameter of the granulated powder to 15 μm or more and 100 μm or less.

[Calcination process]
In this step, the granulated powder is put into a furnace heated to 800 ° C. to 1000 ° C. and calcined in the atmosphere to obtain a calcined product. At this time, a hollow structure is formed in the granulated powder by the gas generated by the combustion of the resin particles. When silicone resin particles are used as the resin particles, SiO ₂ that is a nonmagnetic oxide is generated in the hollow structure.

[Baking process]
In this step, the calcined product in which the hollow structure is formed by the above step is put into a furnace heated to 1100 to 1250 ° C. and fired, and then converted into a fermented product. When the firing temperature is high, iron oxidation proceeds and the magnetic force decreases, so the residual magnetization of the carrier core material can be adjusted, for example, by the firing temperature. The atmosphere during firing is appropriately selected according to the type of metal raw material such as magnetic oxide among the carrier core raw materials. For example, when the metal raw material is Fe and Mn (molar ratio 100: 0 to 50:50), the nitrogen atmosphere is used. When the metal raw material is Fe, Mn, and Mg, a nitrogen atmosphere or an oxygen partial pressure adjustment atmosphere is preferable, but when the molar ratio of Mg exceeds 30%, an air atmosphere may be used.

[Disintegration process, classification process]
In this step, the fired product obtained in the firing step is coarsely pulverized by hammer mill pulverization or the like, and then primary classified by an airflow classifier. Further, after aligning the particle size with a vibration sieve or an ultrasonic sieve, the carrier core material 51 having voids 51b inside and having surface pores 51a formed on the surface by removing non-magnetic components by applying a magnetic separator. Get.

[Nitrogen-containing crosslinked resin fine particle addition step]
In this step, the carrier core material obtained in the classification step is immersed in a nitrogen-containing crosslinked resin fine particle dispersion in which nitrogen-containing crosslinked resin fine particles are dispersed in an organic solvent, and heated to 80 ° C. to 100 ° C. while stirring. . The organic solvent is not particularly limited as long as it does not dissolve the nitrogen-containing crosslinked resin fine particles, and examples thereof include toluene.

  Further, the nitrogen-containing crosslinked resin fine particles added to the organic solvent are selected from those whose volume average particle diameter Da satisfies the formula (1). For example, the volume average particle diameter Da of the nitrogen-containing crosslinked resin fine particles added to the organic solvent is measured in advance, and the surface fineness formed on the carrier core material 51 is adjusted by adjusting the amount of resin particles added in the mixing step. You may make it satisfy | fill said Formula (1) by controlling the area average diameter Db of the hole 51a.

  Thereafter, the organic solvent is volatilized and removed, thereby attaching the nitrogen-containing crosslinked resin fine particles 53 to the surface of the carrier core material 51, thereby obtaining the carrier core material 51 in which the surface pores 51 a are blocked with the nitrogen-containing crosslinked resin fine particles 53.

  At this time, the opening surface pore ratio P1 can be controlled by adjusting the amount of the nitrogen-containing crosslinked resin fine particles 53 added to the nitrogen-containing crosslinked resin fine particle dispersion.

[Coating process]
In this step, the resin coating composition is added to an organic solvent such as toluene with respect to the carrier core material 51 whose surface pores are closed with the nitrogen-containing crosslinked resin fine particles 53 obtained in the nitrogen-containing crosslinked resin fine particle addition step. The dissolved coating resin solution is coated while being heated by a dipping method to volatilize and remove the organic solvent, and the resin coating layer 52 can be formed on the surface of the carrier core material 51. Thereafter, the resin-coated carrier 50 is obtained by further heating and curing the resin-coated layer 52.

  In the resin-coated carrier 50 obtained in this manner, the resin is not filled in the gap 51b of the carrier core material 51. The size of the gap 51b is about 0.7 μm, and in order for the carrier core material 51 having the gap 51b of this size to be filled with the resin, the resin needs to permeate by capillary action. In the embodiment, since the surface pores 51 a of the carrier core material 51 are blocked by the nitrogen cross-linked resin fine particles 53, the resin is not filled in the voids 51 b formed inside the carrier core material 51.

2. Two-component developer The two-component developer includes a resin-coated carrier 50 produced as described above and a toner containing a binder resin and a colorant. Since the resin-coated carrier 50 can give a stable charge amount to the toner, a two-component developer having a stable charge amount can be obtained even if the number of printed sheets is increased. By using such a two-component developer, images can be reproduced with high definition, color reproducibility is good, image density is high, and high-quality images free from image defects such as fog are stable over a long period of time. Can be formed.

(1) Toner The toner contains toner base particles containing a binder resin and a colorant as essential components, and additionally contains a charge control agent, a release agent and the like. The toner contains two or more external additives having different particle diameters.

(Binder resin)
The binder resin is not particularly limited, and a known binder resin for black toner or color toner can be used. Examples include polyester resins, styrene resins such as polystyrene and styrene-acrylic acid ester copolymer resins, acrylic resins such as polymethyl methacrylate, polyolefin resins such as polyethylene, polyurethane, and epoxy resins. Moreover, you may use resin obtained by mixing a raw material monomer mixture with a mold release agent and performing a polymerization reaction. Binder resin may be used individually by 1 type, and may use 2 or more types together.

  When a polyester resin is used as the binder resin, examples of the aromatic alcohol component for obtaining the polyester resin include bisphenol A, polyoxyethylene- (2.2) -2,2-bis (4-hydroxyphenyl) propane. , Polyoxyethylene- (2.0) -2,2-bis (4-hydroxyphenyl) propane, polyoxypropylene- (2.0) -2,2-bis (4-hydroxyphenyl) propane, polyoxypropylene -(2.2) -Polyoxyethylene- (2.0) -2,2-bis (4-hydroxyphenyl) propane, polyoxypropylene- (6) -2,2-bis (4-hydroxyphenyl) propane , Polyoxypropylene- (2.2) -2,2-bis (4-hydroxyphenyl) propane, polyoxypropylene (2.4) -2,2-bis (4-hydroxyphenyl) propane, polyoxypropylene - (3.3) -2,2-bis (4-hydroxyphenyl) propane and derivatives thereof.

  The polybasic acid component of the polyester resin includes succinic acid, adipic acid, sebacic acid, azelaic acid, dodecenyl succinic acid, n-dodecyl succinic acid, malonic acid, maleic acid, fumaric acid, citraconic acid, itaconic acid, glutaconic acid. , Dibasic acids such as cyclohexanedicarboxylic acid, orthophthalic acid, isophthalic acid, terephthalic acid, acids having three or more bases such as trimellitic acid, trimetic acid, pyromellitic acid, and anhydrides thereof, and lower alkyl esters. From the viewpoint of heat-resistant aggregation, terephthalic acid or its lower alkyl ester is preferred.

  Here, the acid value of the polyester resin constituting the toner is preferably 5 to 30 mgKOH / g. When the acid value is less than 5 mgKOH / g, the charging characteristics of the resin are lowered, and the charge control agent is hardly dispersed in the polyester resin. This adversely affects the charge amount stability of repeated development due to rising of the charge amount or continuous use. Therefore, the above range is preferable.

(Coloring agent)
As the colorant, various colorants can be used according to a desired color, and examples thereof include a yellow toner colorant, a magenta toner colorant, a cyan toner colorant, and a black toner colorant. .

  Examples of the colorant for yellow toner include C.I. I. Pigment yellow 1, C.I. I. Pigment yellow 5, C.I. I. Pigment yellow 12, C.I. I. Pigment yellow 15, C.I. I. Azo pigments such as CI Pigment Yellow 17; inorganic pigments such as yellow iron oxide and ocher; I. Nitro dyes such as Acid Yellow 1, C.I. I. Solvent Yellow 2, C.I. I. Solvent Yellow 6, C.I. I. Solvent Yellow 14, C.I. I. Solvent Yellow 15, C.I. I. Solvent Yellow 19, C.I. I. Examples thereof include oil-soluble dyes such as Solvent Yellow 21.

  Examples of the colorant for magenta toner include C.I. I. Pigment red 49, C.I. I. Pigment red 57, C.I. I. Pigment red 81, C.I. I. Pigment red 122, C.I. I. Solvent Red 19, C.I. I. Solvent Red 49, C.I. I. Solvent Red 52, C.I. I. Basic Red 10, C.I. I. Disperse Red 15 etc. are mentioned.

  Examples of the colorant for cyan toner include C.I. I. Pigment blue 15, C.I. I. Pigment blue 16, C.I. I. Solvent Blue 55, C.I. I. Solvent Blue 70, C.I. I. Direct Blue 25, C.I. I. Direct Blue 86 and the like can be mentioned.

  Examples of the colorant for black toner include carbon black such as channel black, roller black, disk black, gas furnace black, oil furnace black, thermal black, and acetylene black. From these various types of carbon black, an appropriate carbon black may be appropriately selected according to the design characteristics of the toner to be obtained.

  As the colorant, in addition to these pigments, a red pigment, a green pigment, or the like may be used. A coloring agent may be used individually by 1 type, and may use 2 or more types together. Two or more of the same color can be used, and one or more of the different colors can also be used.

  The colorant may be used in the form of a masterbatch. The master batch of the colorant can be produced in the same manner as a general master batch. For example, it can be produced by kneading a melt of a synthetic resin and a colorant to uniformly disperse the colorant in the synthetic resin, and then granulating the resulting melt-kneaded product. As the synthetic resin, the same kind as that of the toner binder resin or one having good compatibility with the toner binder resin is used. At this time, the use ratio of the synthetic resin and the colorant is not particularly limited, but is preferably 30 to 100 parts by weight with respect to 100 parts by weight of the synthetic resin. The master batch is granulated to a particle size of about 2 to 3 mm.

  The amount of the colorant used is not particularly limited, but is preferably 5 to 20 parts by weight with respect to 100 parts by weight of the binder resin. This is not the amount of the master batch but the amount of the colorant itself contained in the master batch. By using the colorant in this range, an image having a high image density and a very good image quality can be formed without impairing various physical properties of the toner.

(Charge control agent)
The charge control agent is added for the purpose of controlling the triboelectric chargeability of the toner. As the charge control agent, a charge control agent for positive charge control or negative charge control commonly used in this field can be used. Examples of charge control agents for controlling positive charge include nigrosine dyes, basic dyes, quaternary ammonium salts, quaternary phosphonium salts, aminopyrines, pyrimidine compounds, polynuclear polyamino compounds, aminosilanes, nigrosine dyes and derivatives thereof, and triphenylmethane. Derivatives, guanidine salts, amidine salts and the like can be mentioned.

  Examples of charge control agents for controlling negative charges include oil-soluble dyes such as oil black and spiron black, metal-containing azo compounds, azo complex dyes, naphthenic acid metal salts, metal complexes and metal salts of salicylic acid and its derivatives ( Examples of the metal include chromium, zinc, zirconium, etc.), boron compounds, fatty acid soaps, long-chain alkyl carboxylates, and resin acid soaps. Among these, a boron compound is particularly preferable as it does not contain a heavy metal.

  The charge control agent for controlling the positive charge and the charge control agent for controlling the negative charge may be properly used according to the respective uses. A charge control agent may be used individually by 1 type, and may use 2 or more types together as needed. The amount of the charge control agent used is not particularly limited and can be appropriately selected from a wide range, but is preferably 0.5 to 3 parts by weight with respect to 100 parts by weight of the binder resin.

(Release agent)
As the release agent, those commonly used in this field can be used, for example, paraffin wax and derivatives thereof, petroleum wax such as microcrystalline wax and derivatives thereof, Fischer-Tropsch wax and derivatives thereof, polyolefin wax and derivatives thereof, Low molecular weight polypropylene wax and derivatives thereof, hydrocarbon-based synthetic waxes such as polyolefin polymer waxes (low molecular weight polyethylene wax and the like) and derivatives thereof, carnauba wax and derivatives thereof, rice wax and derivatives thereof, candelilla wax and derivatives thereof , Plant waxes such as wood wax, animal waxes such as beeswax and spermaceti, synthetic oil waxes such as fatty acid amides and phenol fatty acid esters, long chain carboxylic acids and their derivatives , Long chain alcohols and derivatives thereof, silicone polymers, such as higher fatty acids. Derivatives include oxides, block copolymers of vinyl monomers and waxes, graft modified products of vinyl monomers and waxes, and the like. The amount of the release agent used is not particularly limited and can be appropriately selected from a wide range, but is preferably 0.2 to 20 parts by weight with respect to 100 parts by weight of the binder resin.

(External additive)
As the external additive for the toner, those commonly used in this field can be used, and examples thereof include silicon oxide, titanium oxide, silicon carbide, aluminum oxide, and barium titanate. In the present embodiment, two or more kinds of external additives having different particle diameters are used in combination, and the volume average particle diameter of at least one primary particle diameter is 0.1 to 0.2 μm. When an external additive having at least one primary particle size of 0.1 to 0.2 μm is used, particularly in a color toner, transferability is improved and the external additive adheres to the carrier surface. The toner can be charged for a long time and stably without causing a decrease in charge. The amount of the external additive used is not particularly limited, but is preferably 0.1 to 3.0 parts by weight with respect to 100 parts by weight of the toner.

  The raw materials of these toners are mixed by a mixer such as a Henschel mixer, a super mixer, a mechano mill, and a Q-type mixer, excluding external additives, and the resulting raw material mixture is a twin-screw kneader, a single-screw kneader, and a continuous type 2 After being melt-kneaded at a temperature of about 70 to 180 ° C. by a kneader such as a roll-type kneader, the mixture is cooled and solidified. The melted and kneaded product of the toner raw material after cooling and solidification is roughly pulverized by a cutter mill, a feather mill or the like. The resulting coarsely pulverized product is finely pulverized. For fine pulverization, a jet mill, a fluidized bed type jet pulverizer, or the like is used. These pulverizers pulverize the toner particles by causing the toner particles to collide with each other by colliding the air flow containing the toner particles from a plurality of directions. As a result, non-magnetic toner base particles having a specific particle size distribution can be produced. The particle diameter of the toner base particles is not particularly limited, but the volume average particle diameter is preferably in the range of 3 to 10 μm. Furthermore, particle size adjustment such as classification may be performed as necessary. The external additive is added to the toner base particles thus produced by a known method. The toner manufacturing method is not limited to the above.

(2) Two-component developer The two-component developer is produced by mixing the toner and the resin-coated carrier 50. The mixing ratio of the toner and the resin-coated carrier 50 is not particularly limited, but considering the use in a high-speed image forming apparatus (40 sheets / minute or more for A4-size images), the volume average particle diameter of the resin-coated carrier 50 is / The ratio of the total projected area of the toner (the sum of the projected areas of all the toner particles) to the total surface area of the resin-coated carrier 50 (the total surface area of all the resin-coated carrier particles) when the volume average particle diameter of the toner is 5 or more ( (Total projected area of toner / total surface area of resin-coated carrier 50) × 100) may be 30 to 70%. Thus, a two-component developer that can stably maintain a sufficiently high chargeability of the toner and can stably form a high-quality image for a long period of time even in a high-speed image forming apparatus can be obtained.

  For example, in the two-component developer, the volume average particle diameter of the toner is 6.5 μm, the volume average particle diameter of the resin-coated carrier 50 is 50 μm, and the ratio of the total projected area of the toner to the total surface area of the resin-coated carrier 50 is 30 to 70%. In this case, the two-component developer contains about 2.2 to 5.3 parts by weight of toner with respect to 100 parts by weight of the resin-coated carrier. When high-speed development is performed with such a two-component developer, the toner consumption amount and the toner supply amount supplied to the developing tank of the developing device are maximized according to the toner consumption. It will not be. If the amount of toner in the two-component developer is greater than about 2.2 to 5.3 parts by weight, the charge amount tends to decrease, so that not only the desired development characteristics cannot be obtained, but also the toner supply amount The amount of toner consumption increases, and sufficient charge cannot be imparted to the toner, resulting in degradation of image quality. Further, if the amount of toner is less than about 2.2 to 5.3 parts by weight, the amount of charge tends to be high, so that it becomes difficult for the toner to be separated from the resin-coated carrier 50 by an electric field. to degrade.

3 and Development Device FIG. 2 is a diagram showing a configuration of a development device 20 according to an embodiment of the present invention. The developing device 20 performs development using the two-component developer 1 produced as described above. As shown in FIG. 2, the developing device 20 includes a developing unit 10 that stores the two-component developer 1 and a developer carrier (developer transport) that transports the two-component developer 1 to an image carrier (photoconductor) 15. Support) 13.

  The two-component developer 1 composed of the resin-coated carrier 50 and the toner, which has been put in advance in the developing unit 10, is stirred by the stirring screw 12, whereby the two-component developer 1 is charged. Then, the two-component developer 1 is conveyed to a developer carrier 13 having a magnetic field generating unit (not shown) disposed therein, and is held on the surface of the developer carrier 13. The two-component developer 1 held on the surface of the developer carrier 13 is adjusted to a constant layer thickness by the developer regulating member 14, and a development region formed in the adjacent region between the developer carrier 13 and the image carrier 15. It is conveyed to. By applying an AC bias to the two-component developer 1 conveyed to the development area, the electrostatic charge image on the image carrier 15 is visualized by a reversal development method, and a visible image is formed on the image carrier 15. It is formed.

  Toner consumption due to visible image formation is detected by the toner concentration sensor 16 as a change in toner concentration, which is a toner weight ratio with respect to the two-component developer weight. The consumed amount is replenished from the toner hopper 17 until the toner concentration sensor 16 detects that a predetermined specified toner concentration has been reached, so that the toner concentration in the two-component developer 1 in the developing unit 10 is substantially the same. Kept constant. In this embodiment, the gap between the developer carrier 13 and the developer regulating member 14 and the gap between the developer carrier 13 and the image carrier 15 in the development region are set to 0.4 mm, for example. This is merely an example, and is not limited to this value. As described above, the developing device 20 according to the present embodiment performs development using the two-component developer according to the present embodiment. Therefore, even if the number of printed sheets increases, the developing device 20 can perform development with toner having a stable charge amount. A high-definition and fog-free toner image can be stably formed over a long period of time.

4. Image Forming Apparatus The image forming apparatus according to the present embodiment includes the developing device 20 described above. Other configurations can be the same as those of a known electrophotographic image forming apparatus. For example, an image carrier, a charging unit, an exposure unit, a transfer unit, a fixing unit, and an image carrier. A cleaning unit; and an intermediate transfer member cleaning unit. The image carrier has a photosensitive layer capable of forming an electrostatic charge image on the surface. The charging unit charges the surface of the image carrier to a predetermined potential. The exposure means irradiates the image carrier with the surface charged with signal light corresponding to the image information to form an electrostatic charge image (electrostatic latent image) on the surface of the image carrier. The transfer unit transfers the toner image on the surface of the image carrier developed by the toner supplied from the developing device 20 to the intermediate transfer member, and then transfers the toner image to the recording medium. The fixing unit fixes the toner image on the surface of the recording medium to the recording medium. The image carrier cleaning means removes toner and paper dust remaining on the surface of the image carrier after the transfer of the toner image to the recording medium. The intermediate transfer member cleaning unit removes excess toner and the like attached to the intermediate transfer member.

  The image forming apparatus of this embodiment includes the developing device 20 described above. Since the developing device 20 can stably form a high-definition, non-fogging toner image over a long period of time, the image forming device of this embodiment also reproduces an image with high definition and color reproduction. It is possible to stably form a high-quality image having good properties and high image density and free from image defects such as fogging over a long period of time.

(Example)
Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples. In the following, “parts” and “%” mean “parts by weight” and “% by weight” unless otherwise specified. In Example and Comparative Example, apparent density of carrier core material, total area and area average diameter of surface pores of carrier core material, volume average particle diameter of resin fine particles and resin-coated carrier, total surface area of resin-coated carrier, toner The volume average particle diameter and the total projected area of the toner were measured as follows.

[Apparent density of carrier core]
The apparent density of the carrier core material was measured according to JIS Z2504 2000 (metal powder apparent density test method).

[Total area and area average diameter of surface pores of carrier core material]
The carrier core material before and after the addition of the crosslinked resin fine particles is photographed with an electron microscope (trade name: VE-9500, manufactured by Keyence Corporation) at a magnification of 1000 times. Next, an area of ½ of the radius of the carrier core material from the center of the carrier core material is trimmed from the photograph, and the carrier core is imaged from that area by image analysis software (trade name: A Image-kun, manufactured by Asahi Kasei Engineering Co., Ltd.). By extracting and analyzing the contours of the surface pores of the material, the total surface pore area and the area average diameter of the carrier core material are calculated. Such an analysis was performed on each of the 50 core particles before and after the addition of the crosslinked resin fine particles, and the average value was defined as the total surface pore area and the area average diameter of the carrier core material.

[Volume average particle diameter of resin fine particles and resin-coated carrier]
Emulgen 109P (manufactured by Kao Corporation, polyoxyethylene lauryl ether HLB 13.6) 5% About 10 to 15 mg of a measurement sample was added to 10 mL and dispersed with an ultrasonic disperser for 1 minute. About 1 mL of this was added to a predetermined part of Microtrac (trade name: Microtrac MT3000, manufactured by Nikkiso Co., Ltd.), and then stirred for 1 minute to confirm that the scattered light intensity was stable and measured.

[Total surface area of resin-coated carrier]
The total surface area of the resin-coated carrier is calculated from the particle diameter and weight measured from Microtrac (trade name: Microtrac MT3000, manufactured by Nikkiso Co., Ltd.). The specific gravity of the resin-coated carrier is 3.7.

[Volume average particle diameter of toner]
In a 100 mL beaker, 20 mL of a 1% aqueous solution (electrolytic solution) of sodium chloride (first grade) was added, 0.5 mL of alkylbenzene sulfonate (dispersant) and 3 mg of a toner sample were sequentially added thereto, and ultrasonically dispersed for 5 minutes. . To this, a 1% aqueous solution of sodium chloride (first grade) was added so that the total amount would be 100 mL, and again ultrasonically dispersed for 5 minutes was used as a measurement sample. For this measurement sample, a Coulter Counter TA-III (trade name, manufactured by Coulter, Inc.) was used, and measurement was performed under the conditions of an aperture diameter of 100 μm and a measurement target particle diameter of 2 to 40 μm on a number basis. Calculated.

[Total projected area of toner]
Based on the volume average particle diameter obtained with a Coulter Counter (trade name: Coulter Counter Multisizer II, manufactured by Beckman Coulter, Inc.), the number of toners with respect to the toner weight is calculated. The number x toner area (calculated assuming a circle) is the total toner projected area.

Example 1
<Production of resin-coated carrier>
[Weighing process, mixing process]
As raw materials for the carrier core material, finely pulverized Fe ₂ O ₃ and MgCO ₃ were weighed and mixed so that the molar ratio Fe ₂ O ₃ : MgCO ₃ = 80: 20 was obtained, thereby obtaining a metal raw material mixture. In addition, polyethylene resin particles (trade name: LE-1080, manufactured by Sumitomo Seika Co., Ltd., volume average particle diameter 5 μm), ammonium polycarboxylate dispersant, SN wet 980 (wetting agent, manufactured by San Nopco) Then, a resin fine particle aqueous solution in which polyvinyl alcohol (binder) was mixed in an amount corresponding to 5 wt%, 1.5 wt%, 0.05 wt%, and 0.02 wt% with respect to all raw materials of the carrier core material was prepared.

[Crushing process]
The metal raw material mixture was added to the resin fine particle aqueous solution prepared in the above step and stirred to obtain a slurry having a concentration of 75 wt%. This slurry was wet pulverized by a wet ball mill and stirred until the volume average particle diameter became 1 μm.

[Granulation process]
The slurry was sprayed into hot air with a spray dryer to obtain dried granulated powder (volume average particle diameter of 10 to 200 μm). Coarse grains were separated from the granulated powder using a sieve net having a mesh size of 61 μm.

[Calcination process]
The dried granulated powder was calcined by heating at 900 ° C. in the atmosphere, and the resin particle component was decomposed to obtain a calcined product.

[Baking process]
The calcined product was calcined for 5 hours in a nitrogen atmosphere at 1160 ° C. to make a ferrite product, thereby obtaining a calcined product.

[Disintegration process, classification process]
The fired product is crushed with a hammer mill, fine powder is removed using an air classifier, and the particle size is adjusted with a vibrating screen having a mesh size of 54 μm, whereby the carrier core material C1 (apparent density 1.80 g / cm ³ , surface The area average diameter of the pores was 0.60 μm).

[Nitrogen-containing crosslinked resin fine particle addition step]
As the nitrogen-containing crosslinked resin fine particles, melamine resin fine particles S1 (trade name: Eposter, manufactured by Nippon Shokubai Co., Ltd., volume average particle diameter 0.70 μm) is used. The weight was adjusted so that the ratio was 20%, and ultrasonic dispersion was performed in 15 parts of toluene to prepare a nitrogen-containing crosslinked resin fine particle dispersion.

  100 parts of the carrier core material C1 was immersed in this nitrogen-containing crosslinked resin fine particle dispersion and stirred while heating. Thereafter, toluene was volatilized and removed, melamine resin fine particles S1 were adhered to the surface of the carrier core material C1, and a carrier core material C1 whose surface pores were blocked with melamine resin fine particles S1 was obtained. The opening surface pore ratio P1 of this carrier core material C1 (the ratio of the total area of the opened surface pores after addition of melamine resin fine particles to the total surface area of the carrier core material) was 3%.

[Coating process]
Dissolve 2.0 parts of crosslinked silicone resin A (trade name: KR240, manufactured by Shin-Etsu Chemical Co., Ltd.) and 2.0 parts of crosslinked silicone resin B (trade name: KR251, manufactured by Shin-Etsu Chemical Co., Ltd.) in 15 parts of toluene. In addition, 0.20 part of conductive particles (trade name: VULCAN XC-72, manufactured by Cabot Corporation) and 0.20 part of coupling agent (trade name: AY43-059, manufactured by Toray Dow Corning Co., Ltd.) A coating resin solution was prepared by internal addition or dispersion. 19.4 parts of this coating resin solution was added to the carrier core material C1 obtained in the nitrogen-containing crosslinked resin fine particle addition step, and the surface of the carrier core material C1 was coated with a silicone resin by an immersion method. Then, after passing through a curing treatment at a curing temperature of 200 ° C. and a curing time of 1 hour, the resin-coated carrier of Example 1 (volume average particle diameter of 45 μm) was obtained by passing through a sieve having an opening of 150 μm.

(Example 2)
In the mixing step, the carrier core material C2 (apparent density) was obtained in the same manner as in Example 1 except that the addition amount of the polyethylene resin particles was changed from 5 wt% to 0.5 wt% with respect to the total raw material of the carrier core material. 1.98 g / cm ³ and surface pore area average diameter 0.42 μm).

  In the step of adding the nitrogen-containing crosslinked resin fine particles, the weight of the melamine resin fine particles S1 is adjusted so that the ratio of the total projected area of the melamine resin fine particles S1 to the total surface area of the carrier core material C2 is 20%. The carrier core material C2 (opening surface pore ratio P1) in which the surface pores were closed with melamine resin fine particles S1 in the same manner as in Example 1 except that 100 parts of the carrier core material C2 was used instead of the core material C1. : 2%).

  In the coating step, a resin-coated carrier of Example 2 (volume average particle diameter of 45 μm) was obtained in the same manner as in Example 1 except that the carrier core material C2 was used instead of the carrier core material C1.

(Example 3)
In the mixing step, the carrier core material C3 (with an apparent density of 1.) was added in the same manner as in Example 1 except that the addition amount of the polyethylene resin particles was changed from 5 wt% to 15 wt% with respect to all raw materials of the carrier core material. 62 g / cm ³ and an area average diameter of surface pores of 0.67 μm).

  In the step of adding the nitrogen-containing crosslinked resin fine particles, the weight of the melamine resin fine particles S1 is adjusted so that the ratio of the total projected area of the melamine resin fine particles S1 to the total surface area of the carrier core material C3 is 20%. The carrier core material C3 (opening surface pore ratio P1) in which the surface pores were closed with the melamine resin fine particles S1 in the same manner as in Example 1 except that 100 parts of the carrier core material C3 was used instead of the core material C1. : 4%).

  In the coating step, a resin-coated carrier of Example 3 (volume average particle diameter of 45 μm) was obtained in the same manner as in Example 1 except that the carrier core material C3 was used instead of the carrier core material C1.

Example 4
In the coating step, a resin-coated carrier of Example 4 (volume average particle diameter of 45 μm) was obtained in the same manner as in Example 1 except that the conductive particles were not added to the coating resin solution. In the resin-coated carrier of Example 4, the carrier core material C4 had an apparent density of 1.80 g / cm ³ and an area average diameter of surface pores of 0.60 μm.

  At this time, the aperture surface pore ratio P1 (the ratio of the total area of the apertured surface pores after addition of fine particles to the total surface area of the carrier core material) was 3%.

(Example 5)
A carrier core material C5 (apparent density 1.83 g / cm ³ , surface pore area average diameter 0.61 μm) was obtained in the same manner as in Example 1 except that the conditions of the granulation step were changed.

  In the step of adding the nitrogen-containing crosslinked resin fine particles, the weight of the melamine resin fine particles S1 is adjusted so that the ratio of the total projected area of the melamine resin fine particles S1 to the total surface area of the carrier core material C5 is 20%. The carrier core material C5 (opening surface pore ratio P1) in which the surface pores were closed with the melamine resin fine particles S1 in the same manner as in Example 1 except that 100 parts of the carrier core material C5 was used instead of the core material C1. : 4%).

  In the coating step, a resin-coated carrier of Example 5 (volume average particle diameter of 25 μm) was obtained in the same manner as in Example 1 except that the carrier core material C5 was used instead of the carrier core material C1.

(Example 6)
A carrier core material C6 (apparent density 1.79 g / cm ³ , surface pore area average diameter 0.59 μm) was obtained in the same manner as in Example 1 except that the conditions of the granulation step were changed.

  In the step of adding the nitrogen-containing crosslinked resin fine particles, the weight of the melamine resin fine particles S1 is adjusted so that the ratio of the total projected area of the melamine resin fine particles S1 to the total surface area of the carrier core material C6 is 20%. Carrier core material C6 (opening surface pore ratio P1) in which the surface pores were closed with melamine resin fine particles S1 in the same manner as in Example 1 except that 100 parts of carrier core material C6 was used instead of core material C1. : 3%).

  In the coating step, a resin-coated carrier of Example 6 (volume average particle diameter of 50 μm) was obtained in the same manner as in Example 1 except that the carrier core material C6 was used instead of the carrier core material C1.

(Example 7)
A carrier core material C7 (apparent density 1.78 g / cm ³ , surface pore area average diameter 0.58 μm) was obtained in the same manner as in Example 1 except that the conditions of the granulation step were changed.

  In the step of adding the nitrogen-containing crosslinked resin fine particles, the weight of the melamine resin fine particles S1 is adjusted so that the ratio of the total projected area of the melamine resin fine particles S1 to the total surface area of the carrier core material C7 is 20%. The carrier core material C7 (opening surface pore ratio P1) in which the surface pores were closed with the melamine resin fine particles S1 in the same manner as in Example 1 except that 100 parts of the carrier core material C7 was used instead of the core material C1. : 3%).

  In the coating step, a resin-coated carrier of Example 7 (volume average particle diameter 55 μm) was obtained in the same manner as in Example 1 except that the carrier core material C7 was used instead of the carrier core material C1.

(Example 8)
A carrier core material C8 (apparent density 1.75 g / cm ³ , surface pore area average diameter 0.62 μm) was obtained in the same manner as in Example 1 except that the conditions of the granulation step were changed.

  In the step of adding the nitrogen-containing crosslinked resin fine particles, the weight of the melamine resin fine particles S1 is adjusted so that the ratio of the total projected area of the melamine resin fine particles S1 to the total surface area of the carrier core material C8 is 20%. The carrier core material C8 (opening surface pore ratio P1) in which the surface pores were closed with the melamine resin fine particles S1 in the same manner as in Example 1 except that 100 parts of the carrier core material C8 was used instead of the core material C1. : 3%).

  In the coating step, a resin-coated carrier of Example 8 (volume average particle diameter of 20 μm) was obtained in the same manner as in Example 1 except that the carrier core material C8 was used instead of the carrier core material C1.

Example 9
In the step of adding the nitrogen-containing crosslinked resin fine particles, except that the weight of the melamine resin fine particles S1 is adjusted so that the ratio of the total projected area of the melamine resin fine particles S1 to the total surface area of the carrier core material C2 is 10%. In the same manner as in Example 2, a carrier core material C2 (opening surface pore ratio P1: 3%) whose surface pores were closed with melamine resin fine particles S1 was obtained.

  In the coating step, the same procedure as in Example 2 was performed except that the carrier core material C2 having an opening surface pore ratio P1 of 3% was used instead of the carrier core material C2 having an opening surface pore ratio P1 of 2%. Thus, a resin-coated carrier of Example 9 (volume average particle diameter of 45 μm) was obtained.

(Example 10)
In the step of adding the nitrogen-containing crosslinked resin fine particles, except that the weight of the melamine resin fine particles S1 is adjusted so that the ratio of the total projected area of the melamine resin fine particles S1 to the total surface area of the carrier core material C2 is 5%. In the same manner as in Example 2, a carrier core material C2 (opening surface pore ratio P1: 5%) whose surface pores were closed with melamine resin fine particles S1 was obtained.

  In the coating step, the same procedure as in Example 2 was performed except that the carrier core material C2 having an opening surface pore ratio P1 of 5% was used instead of the carrier core material C2 having an opening surface pore ratio P1 of 2%. Thus, a resin-coated carrier of Example 10 (volume average particle diameter of 45 μm) was obtained.

(Example 11)
In the step of adding the nitrogen-containing crosslinked resin fine particles, except that the weight of the melamine resin fine particles S1 is adjusted so that the ratio of the total projected area of the melamine resin fine particles S1 to the total surface area of the carrier core material C3 is 30%. In the same manner as in Example 3, a carrier core material C3 (opening surface pore ratio P1: 2%) whose surface pores were blocked with melamine resin fine particles S1 was obtained.

  In the coating step, the same procedure as in Example 3 was performed except that the carrier core material C3 having an opening surface pore ratio P1 of 2% was used instead of the carrier core material C3 having an opening surface pore ratio P1 of 4%. Thus, a resin-coated carrier of Example 11 (volume average particle diameter of 45 μm) was obtained.

(Example 12)
In the step of adding the nitrogen-containing crosslinked resin fine particles, except that the weight of the melamine resin fine particles S1 is adjusted so that the ratio of the total projected area of the melamine resin fine particles S1 to the total surface area of the carrier core material C3 is 35%. In the same manner as in Example 3, a carrier core material C3 (opening surface pore ratio P1: 3%) whose surface pores were closed with melamine resin fine particles S1 was obtained.

  In the coating step, the same procedure as in Example 3 was performed except that the carrier core material C3 having an opening surface pore ratio P1 of 3% was used instead of the carrier core material C3 having an opening surface pore ratio P1 of 4%. Thus, a resin-coated carrier of Example 12 (volume average particle diameter of 45 μm) was obtained.

(Example 13)
In the coating step, the same as in Example 1 except that 0.8 parts by weight of magnetite fine particles (trade name: BL-10, manufactured by Titanium Industry Co., Ltd., volume average particle size 0.3 μm) was further added to the coating resin solution. Thus, a resin-coated carrier of Example 13 (volume average particle diameter of 45 μm) was obtained.

(Example 14)
In the coating step, magnetite fine particles having a volume average particle size of 1.0 μm (trade name: RB-BL-P, manufactured by Titanium Industry Co., Ltd.) are used in the coating resin solution instead of the magnetite fine particles having a volume average particle size of 0.3 μm. A resin-coated carrier of Example 14 (volume average particle diameter of 45 μm) was obtained in the same manner as Example 13 except that 0.8 part by weight was added.

(Example 15)
In the coating step, magnetite fine particles having a volume average particle size of 0.1 μm (trade name: RB-BL-P, manufactured by Titanium Industry Co., Ltd.) are used in the coating resin solution instead of the magnetite fine particles having a volume average particle size of 0.3 μm. A resin-coated carrier of Example 15 (volume average particle diameter of 45 μm) was obtained in the same manner as Example 13 except that 0.8 part by weight was added.

(Example 16)
In the coating step, magnetite fine particles having a volume average particle size of 3.0 μm (trade name: RB-BL-P, manufactured by Titanium Industry Co., Ltd.) are used instead of the magnetite fine particles having a volume average particle size of 0.3 μm. A resin-coated carrier of Example 16 (volume average particle diameter of 45 μm) was obtained in the same manner as Example 13 except that 0.8 part by weight was added.

(Example 17)
In the mixing step, the carrier core material C17 (apparent density 1...) Was changed in the same manner as in Example 1 except that the addition amount of the polyethylene resin particles was changed from 5 wt% to 20 wt% with respect to all raw materials of the carrier core material. 60 g / cm ³ and area average diameter of surface pores of 0.70 μm) were obtained.

  In the step of adding the nitrogen-containing crosslinked resin fine particles, benzoguanamine resin fine particles S2 (trade name: Eposter MS, manufactured by Nippon Shokubai Co., Ltd., volume average particle size 1.0 μm) is used instead of the melamine resin fine particles S1, and the total surface area of the carrier core material C17. Example except that the weight was adjusted so that the ratio of the total projected area of the benzoguanamine resin fine particles S2 to 20% was 20% and that 100 parts of the carrier core material C17 was used instead of the carrier core material C1. In the same manner as in Example 1, a carrier core material C17 (opening surface pore ratio P1: 5%) whose surface pores were closed with benzoguanamine resin fine particles S2 was obtained.

  In the coating step, a resin-coated carrier of Example 17 (volume average particle diameter of 45 μm) was obtained in the same manner as in Example 1 except that the carrier core material C17 was used instead of the carrier core material C1.

(Example 18)
In the mixing step, the carrier core material C18 (apparent density) was obtained in the same manner as in Example 1 except that the addition amount of the polyethylene resin particles was changed from 5 wt% to 0.3 wt% with respect to all raw materials of the carrier core material. 2.00 g / cm ³ and surface pore area average diameter 0.40 μm).

  In the step of adding the nitrogen-containing crosslinked resin fine particles, the weight of the melamine resin fine particles S1 is adjusted so that the ratio of the total projected area of the melamine resin fine particles S1 to the total surface area of the carrier core material C18 is 20%. The carrier core material C18 (opening surface pore ratio P1) in which the surface pores were closed with the melamine resin fine particles S1 in the same manner as in Example 1 except that 100 parts of the carrier core material C18 was used instead of the core material C1. : 2%).

  In the coating step, a resin-coated carrier of Example 18 (volume average particle diameter of 45 μm) was obtained in the same manner as in Example 1 except that the carrier core material C18 was used instead of the carrier core material C1.

(Example 19)
A carrier core material C19 (apparent density 1.84 g / cm ³ , surface pore area average diameter 0.65 μm) was obtained in the same manner as in Example 1 except that the conditions of the granulation step were changed.

  In the step of adding the nitrogen-containing crosslinked resin fine particles, the weight of the melamine resin fine particles S1 is adjusted so that the ratio of the total projected area of the melamine resin fine particles S1 to the total surface area of the carrier core material C19 is 20%. The carrier core material C19 (opening surface pore ratio P1) in which the surface pores were closed with the melamine resin fine particles S1 in the same manner as in Example 1 except that 100 parts of the carrier core material C19 was used instead of the core material C1. : 5%).

  In the coating step, a resin-coated carrier of Example 19 (volume average particle diameter of 20 μm) was obtained in the same manner as in Example 1 except that the carrier core material C19 was used instead of the carrier core material C1.

(Example 20)
A carrier core material C20 (apparent density 1.78 g / cm ³ , surface pore area average diameter 0.55 μm) was obtained in the same manner as in Example 1 except that the conditions of the granulation step were changed.

  In the step of adding the nitrogen-containing crosslinked resin fine particles, the weight of the melamine resin fine particles S1 is adjusted so that the ratio of the total projected area of the melamine resin fine particles S1 to the total surface area of the carrier core material C20 is 20%. The carrier core material C20 (opening surface pore ratio P1) in which the surface pores were closed with the melamine resin fine particles S1 in the same manner as in Example 1 except that 100 parts of the carrier core material C20 was used instead of the core material C1. : 2%).

  In the coating step, a resin-coated carrier of Example 20 (volume average particle diameter 55 μm) was obtained in the same manner as in Example 1 except that the carrier core material C20 was used instead of the carrier core material C1.

(Comparative Example 1)
In the mixing step, the carrier core material C1c (apparent density 2.15 g / cm) was prepared in the same manner as in Example 1 except that the resin fine particle aqueous solution was prepared without adding the polyethylene resin particles and the calcining step was not performed. ³ and the area average diameter of surface pores was 0.35 μm).

  In the step of adding the nitrogen-containing crosslinked resin fine particles, the weight of the melamine resin fine particles S1 is adjusted so that the ratio of the total projected area of the melamine resin fine particles S1 to the total surface area of the carrier core material C1c is 20%. The carrier core material C1c (opening surface pore ratio P1) in which the surface pores were closed with melamine resin fine particles S1 in the same manner as in Example 1 except that 100 parts of the carrier core material C1c was used instead of the core material C1. : 4%).

  In the coating step, a resin-coated carrier of Comparative Example 1 (volume average particle diameter 45 μm) was obtained in the same manner as in Example 1 except that the carrier core material C1c was used instead of the carrier core material C1.

(Comparative Example 2)
In the mixing step, the carrier core material C2c (with an apparent density of 1.) was added in the same manner as in Example 1 except that the addition amount of the polyethylene resin particles was changed from 5 wt% to 25 wt% with respect to all raw materials of the carrier core material. 51 g / cm ³ and an area average diameter of surface pores of 0.75 μm).

  In the step of adding the nitrogen-containing crosslinked resin fine particles, the weight of the melamine resin fine particles S1 is adjusted so that the ratio of the total projected area of the melamine resin fine particles S1 to the total surface area of the carrier core material C2c is 20%. The carrier core material C2c (opening surface pore ratio P1) in which the surface pores were closed with the melamine resin fine particles S1 in the same manner as in Example 1 except that 100 parts of the carrier core material C2c was used instead of the core material C1. : 10%).

  In the coating step, a resin-coated carrier of Comparative Example 2 (volume average particle diameter of 45 μm) was obtained in the same manner as in Example 1 except that the carrier core material C2c was used instead of the carrier core material C1.

(Comparative Example 3)
The same procedure as in Example 1 except that amorphous silica fine particles (trade name: Seahoster, manufactured by Nippon Shokubai Co., Ltd., volume average particle size 0.70 μm) were used in place of the melamine resin S1 in the nitrogen-containing crosslinked resin fine particle addition step. Thus, a carrier core material C1 (opening surface pore ratio P1: 3%) whose surface pores were closed with amorphous silica fine particles was obtained.

  Example except that in the coating step, the carrier core material C1 whose surface pores were closed with amorphous silica fine particles was used instead of the carrier core material C1 whose surface pores were closed with melamine resin fine particles S1. In the same manner as in Example 1, a resin-coated carrier of Comparative Example 3 (volume average particle diameter of 45 μm) was obtained.

(Comparative Example 4)
The carrier core material C1 in which the surface pores were closed with benzoguanamine resin fine particles in the same manner as in Example 1 except that the benzoguanamine resin fine particles S2 were used instead of the melamine resin S1 in the nitrogen-containing crosslinked resin fine particle addition step. (Opening surface pore ratio P1: 7%) was obtained.

  In the coating step, except that the carrier core material C1 whose surface pores were closed with benzoguanamine resin fine particles S2 was used instead of the carrier core material C1 whose surface pores were closed with melamine resin fine particles S1. In the same manner as in Example 1, the resin-coated carrier of Comparative Example 4 (volume average particle diameter 45 μm) was obtained.

(Comparative Example 5)
In the mixing step, the carrier core material C5c (with an apparent density of 1.) was added in the same manner as in Example 1 except that the addition amount of the polyethylene resin particles was changed from 5 wt% to 25 wt% with respect to all the raw materials of the carrier core material. 51 g / cm ³ and an area average diameter of surface pores of 0.75 μm).

  In the step of adding the nitrogen-containing crosslinked resin fine particles, the weight of the benzoguanamine resin fine particles S2 is adjusted so that the ratio of the total projected area of the benzoguanamine resin fine particles S2 to the total surface area of the carrier core material C5c is 20%. The carrier core material C5c (opening surface pore ratio P1) in which the surface pores were closed with the benzoguanamine resin fine particles S2 in the same manner as in Example 1 except that 100 parts of the carrier core material C5c was used instead of the core material C1. : 5%).

  In the coating step, a resin-coated carrier of Comparative Example 5 (volume average particle diameter of 45 μm) was obtained in the same manner as in Example 1 except that the carrier core material C5c was used instead of the carrier core material C1.

(Comparative Example 6)
In the mixing step, the same procedure as in Example 1 was conducted, except that the resin fine particle aqueous solution was prepared without adding the polyethylene resin particles, the calcining step was not performed, and the firing temperature was changed in the firing step. Carrier core material C6c (apparent density 2.25 g / cm ³ , surface pore area average diameter 0.15 μm) was obtained.

  In the step of adding the nitrogen-containing crosslinked resin fine particles, the weight of the melamine resin fine particles S3 (trade name: Eposter S, manufactured by Nippon Shokubai Co., Ltd., volume average particle diameter 0.20 μm) is used as the melamine resin fine particles S3 with respect to the total surface area of the carrier core material C6c. The surface pores were adjusted in the same manner as in Example 1 except that the weight was adjusted so that the ratio of the total projected area was 20% and that 100 parts of the carrier core material C6c was used instead of the carrier core material C1. A carrier core material C6c (opening surface pore ratio P1: 1%) closed with melamine resin fine particles S3 was obtained.

  In the coating step, a resin-coated carrier of Comparative Example 6 (volume average particle diameter of 45 μm) was obtained in the same manner as in Example 1 except that the carrier core material C6c was used instead of the carrier core material C1.

  Two-component developers were respectively prepared for the resin-coated carriers of Examples 1 to 20 and Comparative Examples 1 to 6, and evaluated as follows. For each evaluation, a copying machine MX-3600FN (manufactured by Sharp Corporation, color print speed 36 ppm, monochrome print speed 36 ppm) was used.

<Preparation of two-component developer>
[Production of toner]
Polyester resin (trade name: FC1494, manufactured by Mitsubishi Rayon Co., Ltd.) 87.5 parts by weight as binder resin, C.I. I. Pigment Red 57: 1, 5 parts by weight, release agent (trade name: HNP11, manufactured by Nippon Seiki Co., Ltd.), charge control agent (trade name: LR-147, manufactured by Nippon Carlit Co., Ltd.) 1.5 The parts by weight were premixed with a Henschel mixer and then melt kneaded with a twin screw extruder kneader to obtain a kneaded product.

  The kneaded material was coarsely pulverized with a cutting mill, then finely pulverized with a jet mill, and classified with an air classifier to prepare toner base particles having a volume average particle diameter of 6.5 μm. Next, 97.8% by weight of the classified toner base particles, 1.2% by weight of silica having a primary particle diameter of 0.1 μm hydrophobized with i-butyltrimethoxysilane, and primary particles hydrophobized with HMDS 1.0% by weight of silica fine particles having a diameter of 12 nm was added, mixed in a Henschel mixer, and subjected to external addition treatment to prepare a negatively chargeable magenta toner (nonmagnetic magenta toner).

  The resin-coated carriers of Examples 1 to 16 and Comparative Examples 1 to 3 and the toner are put into a resin cylindrical container so that the ratio of the total projected area of the toner to the total surface area of the resin-coated carrier is 70%. A two-component developer was prepared by mixing and stirring for 1 hour at a rotation speed of 200 rpm on a double-axis driven polybottle rotary mount.

[Charging rise characteristics]
Each of the two-component developers is put in a 5 ml glass bottle, stirred for 1 minute at 32 rpm in a rotary incubator, then taken from the glass bottle, and a suction-type charge measuring device (trade name: 210H-2A Q / M Meter, TREK). The charge amount was measured by a company). Further, the charge amount was measured in the same manner with a stirring time of 3 minutes. From the difference between the charge amount after 1 minute and the charge amount after 3 minutes, the charge rising characteristics were evaluated according to the following criteria.
◎ (good): difference in charge amount is 5 μC / g or less in absolute value ○ (possible): difference in charge amount is greater than 5 μC / g in absolute value and 7 μC / g or less × (defect): difference in charge amount is absolute Greater than 7 μC / g in value

[Image density, whiteness, charging stability of two-component developer]
Each of the two-component developers is set in the copying machine, and after taking 50K images of a printing rate of 5% under normal temperature and humidity, the image density of the image portion, the whiteness of the non-image portion, and the two-component developer The charge amount of was measured. The image density is measured with an X-Rite 938 spectrophotometric densitometer, and the whiteness is obtained by determining tristimulus values X, Y, and Z using an SZ90 type spectrocolor difference meter manufactured by Nippon Denshoku Industries Co., Ltd. evaluated. Further, the charge amount of the two-component developer at the initial stage and after 50K was measured using a suction-type charge amount measuring device. Each measurement was evaluated according to the following criteria.

(Image density)
◎ (Good): Image density is 1.4 or more ○ (Yes): Image density is 1.3 or more and less than 1.4 × (Bad): Image density is less than 1.3

(Whiteness)
◎ (good): Z value is 0.5 or less ○ (possible): Z value is larger than 0.5 and 0.7 or less × (defect): Z value is larger than 0.7

(Charge stability of two-component developer)
◎ (Good): The difference between the initial charge amount and the charge amount after 50K is 3 μC / g or less in absolute value. ○ (Yes): The difference between the initial charge amount and the charge amount after 50 K is 3 μC / g in absolute value. greater than g and 5 μC / g or less x (defect): the difference between the initial charge amount and the charge amount after 50 K is greater than 5 μC / g in absolute value

[Agitating torque]
The two-component developer was set in the developing tank of the copying machine, and the torque was measured. The stirring torque was evaluated from the torque value according to the following criteria.
◎ (good): Torque value is 11.5 g · cm or less ○ (possible): Torque value is greater than 11.5 g · cm and 12.5 g · cm or less × (defect): Torque value is greater than 12.5 g · cm

[Carrier adhesion]
Each of the two-component developers was set in the copying machine, and the number of carriers adhered in a fixed area (297 mm × 24 mm) in the non-image area on the image carrier was determined. At this time, the DC bias voltage applied to the developer carrier was 200 V, the AC bias voltage was 400 V, and the frequency was 9 kHz, and the surface of the image carrier was not charged. Carrier adhesion was evaluated from the number of carrier adhesion according to the following criteria.
◎ (Good): Number of carriers attached is less than 15 ○ (Yes): Number of carriers attached is 15 or more and 20 or less × (Defect): Carrier attached number is more than 20

[Granularity]
Each of the two-component developers is set in the copying machine, an image test chart is printed, and a granularity score value when the color difference from white is 30, 50, and 70 is used as an automatic printer image quality evaluation system (trade name: APQS, manufactured by Oji Scientific Instruments). The graininess was evaluated according to the following criteria from each score value. A lower score value indicates less image roughness and higher image quality.
◎ (good): maximum score value is less than 11500 ○ (possible): maximum score value is 11500 or more and 12000 or less × (bad): maximum score value is more than 12000

[Edge effect]
Each of the two-component developers was set in the copying machine, a test chart having divided images was printed, and the image density difference between the central portion and the end portion of the solid image was visually observed. The edge effect was evaluated from the image density difference according to the following criteria.
◎ (Good): Almost no difference in density is observed. ○ (Yes): Slight difference in density is observed. X (Poor): Difference in density is clearly recognized.

[Comprehensive evaluation]
The above evaluation results were combined and comprehensive evaluation was performed according to the following criteria.
◎: All results are ◎ ○: Any result is ○, but there is no × ×: Any result is ×

  Table 1 shows the resin-coated carriers of Examples 1 to 20 and Comparative Examples 1 to 6, and Table 2 shows the evaluation results of each resin-coated carrier.

In the carriers of Examples 1 to 20, the apparent density of the carrier core material is 1.6 g / cm ³ or more and 2.0 g / cm ³ or less, and the volume average particle diameter of the nitrogen-containing resin fine particles contained in the resin coating layer There is a relationship satisfying the above formula (1) between the surface average diameter of the surface pores of the carrier core material, and the overall evaluation is ◎ or ○.

In the carrier of Comparative Example 1, the apparent density of the carrier core material is larger than 2.0 g / cm ³ , and the relationship between the volume average particle diameter of the nitrogen-containing resin fine particles and the area average diameter of the surface pores of the carrier core material is as described above. It is considered that the charging stability and the stirring torque were evaluated as x because of not satisfying the formula (1).

In the carrier of Comparative Example 2, the apparent density of the carrier core material is smaller than 1.6 g / cm ³ , and the relationship between the volume average particle diameter of the nitrogen-containing resin fine particles and the area average diameter of the surface pores of the carrier core material is as described above. It is considered that the evaluation of charging stability and carrier adhesion was evaluated as x due to not satisfying the formula (1).

  In the carrier of Comparative Example 3, it is considered that the evaluation of whiteness and charging stability was x because the resin coating layer did not contain nitrogen-containing resin fine particles.

  The carrier of Comparative Example 4 was evaluated for charging stability because the relationship between the volume average particle diameter of the nitrogen-containing resin fine particles and the area average diameter of the surface pores of the carrier core material does not satisfy the above formula (1). Is considered to be x.

The carrier of Comparative Example 5 is considered to have an evaluation of carrier adhesion of x because the apparent density of the carrier core material is smaller than 1.6 g / cm ³ .

The carrier of Comparative Example 6 is considered to have an evaluation of charging stability of x because the apparent density of the carrier core material is larger than 2.0 g / cm ³ .

DESCRIPTION OF SYMBOLS 1 Two-component developer 20 Developing apparatus 50 Resin coated carrier 51 Carrier core material 51a Surface pore 51b Void 52 Resin coating layer 53 Nitrogen-containing crosslinked resin fine particles

Claims (7)

A resin-coated carrier having a carrier core material, a resin coating layer formed on the surface of the carrier core material, and nitrogen-containing crosslinked resin fine particles,
The carrier core material is made of a porous material having pores on the surface, and the apparent density is 1.6 g / cm ³ or more and 2.0 g / cm ³ or less,
The nitrogen-containing crosslinked resin fine particles satisfy the following formula (1) when the volume average particle diameter is Da (μm) and the area average diameter of the pores is Db (μm). Career.
(Db + 0.3 μm) ≧ Da> Db (1)   The resin-coated carrier according to claim 1, wherein the resin-coated layer contains conductive particles.   The resin-coated carrier according to claim 1, wherein the resin-coated layer contains magnetite having a volume average particle diameter of 0.3 μm to 1.0 μm.   The resin-coated carrier according to any one of claims 1 to 3, wherein a volume average particle diameter is 25 µm or more and 50 µm or less.   The resin-coated carrier according to any one of claims 1 to 4, wherein the ratio of the total projected area of the nitrogen-containing crosslinked resin fine particles to the total surface area of the carrier core material is 10% or more and 30% or less. A method for producing the resin-coated carrier according to any one of claims 1 to 5,
Addition of nitrogen-containing cross-linked resin fine particles for attaching nitrogen-containing cross-linked resin fine particles to the surface of a carrier core material made of a porous material having pores on the surface and having an apparent density of 1.6 to 2.0 g / cm ³ Process,
A coating step of forming a resin coating layer by coating a carrier core material having the nitrogen-containing crosslinked resin fine particles attached to the surface obtained in the nitrogen-containing crosslinked resin fine particle addition step;
The carrier core material and the nitrogen-containing crosslinked resin fine particles used in the step of adding the nitrogen-containing crosslinked resin fine particles have a volume average particle diameter of the nitrogen-containing crosslinked resin fine particles as Da (μm) and an area average diameter of the pores as Db ( μm), the following formula (1) is satisfied: A method for producing a resin-coated carrier.
(Db + 0.3 μm) ≧ Da> Db (1)   A two-component developer comprising the resin-coated carrier according to claim 1 and a toner containing a binder resin and a colorant.

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