JP2015203742A - Magnetic carrier, two-component developer, developer to be supplied, and image forming method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide magnetic carrier configured to prevent leakage, and to improve resistance to white-spot failure and image roughness of an image, while preventing reduction in developing performance.SOLUTION: In magnetic carrier formed by coating a surface layer of a porous ferrite core material with resin, the porous ferrite core material has i) a magnetic intensity (σn) of 55 to 70Am/kg when an external magnetic field of 5000/4π(kA/m) is applied, ii) a pore volume of 60 to 120 mm/g, iii) a peak pore size of 0.40 to 0.90 μm, and iv) a particle size distribution (D50) of 25 to 60 μm. In powder x-ray diffraction measurement, the maximum peak intensity in 20deg≤2θ≤40deg satisfies the following formula 1: 1.00≥P/P≥(2σn-65)/75, where Pis a maximum peak value in x-ray diffraction of the porous ferrite core material, and Pis a maximum peak value in x-ray diffraction with the same formulation as the porous ferrite core material, in a particle having a magnetic intensity of 70Am/kg when an external magnetic field of 5000/4π(kA/m) is applied.

Description

  The present invention relates to a magnetic carrier, a two-component developer, a replenishing developer, and an image forming method using the same used in an image forming method for developing an electrostatic image using electrophotography. Is.

  Conventionally, an electrophotographic image forming method forms an electrostatic latent image on an electrostatic latent image carrier using various means, and attaches toner to the electrostatic latent image to form an electrostatic latent image. A developing method is generally used. For this development, there are a wide variety of two-component development systems in which carrier particles called magnetic carriers are mixed with toner, triboelectrically charged, imparted with an appropriate amount of positive or negative charge to the toner, and developed as a driving force. It has been adopted.

  The two-component development method can give functions such as developer agitation, conveyance, and charging to the magnetic carrier, so the function sharing with the toner is clear, and therefore the developer performance controllability is good. There is.

  On the other hand, in recent years, due to technological advancement in the field of electrophotography, there has been an increasingly strict requirement not only to increase the speed and life of the apparatus, but also to increase the definition and stabilize the image quality. In order to meet such a demand, high performance of the magnetic carrier is required.

  As one of them, a proposal has been made to reduce density fluctuations even in long-term use, and in the case of full color, color fluctuations (see Patent Document 1). This carrier is characterized in that the magnetic core material is uneven, and the unevenness is exposed even when the resin is coated. As a result, the above-mentioned problems will be improved. However, while high-speed copying is required as in recent years, the specific gravity of magnetic carrier particles is heavy and the toner is loaded, so the life of the developer is shortened and the image quality is high. Further improvement was required in the follow-up performance to environmental change.

  Under such circumstances, proposals have been made using a porous magnetic core having pores inside the magnetic core and having a reduced specific gravity (see Patent Documents 2, 3, 4, 5, 6, and 7). Although the life of the developer has been improved by these magnetic carriers, new problems such as leakage, white spots and roughness occur, and a magnetic carrier that satisfies these, a two-component developer, and the use thereof. The development of the image forming method that was required became an urgent task.

JP-A-4-93954 JP 2012-173315 A JP 2006-337579 A JP 2009-175666 A Japanese Patent Laid-Open No. 2004-77568 JP 2009-175666 A JP 2010-237525 A

  An object of the present invention is to provide a magnetic carrier that solves the problems as described above, and can stably form a high-definition image. Specifically, an object of the present invention is to provide a magnetic carrier that suppresses the occurrence of leakage, achieves both white-out and anti-glare properties of an image, and does not deteriorate developability.

  The inventors of the present invention use a porous magnetic core, and by using a magnetic carrier as shown below, the occurrence of leaks is suppressed, and both white-out and anti-gray resistance of an image are achieved, and developability is improved. It has been found that a magnetic carrier that does not decrease can be obtained.

That is, the present invention provides a magnetic carrier in which a surface layer of a porous ferrite core material is coated with a resin,
The porous ferrite core material is
i) The magnetization intensity (σn) when an external magnetic field of 5000 / 4π (kA / m) is applied is 55 Am ² / kg or more and 70 Am ² / kg or less,
ii) The pore volume is 60 mm ³ / g or more and 120 mm ³ / g or less,
iii) The peak pore diameter is 0.40 μm or more and 0.90 μm or less,
iv) Volume distribution standard 50% particle size (D50) is 25 μm or more and 60 μm or less,
In powder X-ray diffraction measurement, the present invention relates to a magnetic carrier characterized in that the maximum peak intensity at 20 deg ≦ 2θ ≦ 40 deg satisfies the relationship of Formula 1.
1.00 ≧ P _n / P ₇₀ ≧ (2σn−65) / 75 (Formula 1)
[Where:
P _n is the maximum peak value of the X-ray diffraction of the porous ferrite core material,
P ₇₀ has the same formulation as the porous ferrite core material, and the X-ray diffraction of particles having a magnetization intensity of 70 Am ² / kg when an external magnetic field of 5000 / 4π (kA / m) is applied. Maximum peak value. ]

Further, the present invention is a two-component developer containing a toner containing a binder resin, a colorant and a release agent, and a magnetic carrier,
The present invention relates to a two-component developer, wherein the magnetic carrier is a magnetic carrier having the above structure.

Further, according to the present invention, a replenishment developer is replenished to the developing device in accordance with a decrease in the toner concentration of the two-component developer in the developing device, and an electrostatic latent image formed on the surface of the electrostatic latent image carrier is obtained. A replenishment developer for use in a two-component development method in which development is performed using a two-component developer in a developing device and excess magnetic carrier is discharged from the developing device as needed. There,
The replenishment developer includes a replenishment magnetic carrier and a toner containing a binder resin, a colorant, and a release agent, and a toner amount with respect to 1 part by mass of the replenishment magnetic carrier is 2 parts by mass or more and 50 parts by mass. In the following, the replenishing magnetic carrier is a magnetic carrier having the above-described configuration.

  The present invention also provides a charging step for charging the electrostatic latent image carrier, an electrostatic latent image forming step for forming an electrostatic latent image on the surface of the electrostatic latent image carrier, and the electrostatic latent image in the developing device. Development using a two-component developer to form a toner image, a transfer step of transferring the toner image to a transfer material with or without an intermediate transfer member, and transferring the transferred toner image to a transfer material The present invention relates to an image forming method having a fixing step of fixing to an image forming method, wherein the two-component developer having the above-described configuration is used as the two-component developer.

  Further, according to the present invention, as the toner concentration of the two-component developer in the developing device decreases, the replenishment developer is supplied to the developing device, and the excess magnetic carrier in the developing device is supplied as necessary. An image forming method for discharging from a developing device, wherein the replenishment developer includes a replenishment magnetic carrier and a toner containing a binder resin, a colorant, and a release agent, and the replenishment magnetic carrier is 1 mass. The present invention relates to an image forming method, wherein the toner amount with respect to a portion is 2 parts by mass or more and 50 parts by mass or less, and the replenishing magnetic carrier is a magnetic carrier having the above-described configuration.

  According to the present invention, since the crystal state hardly changes with respect to the change in magnetization, the leakage resistance is improved, the whitening resistance and the anti-gray resistance of the image are compatible, and the developability is deteriorated even in long-term use. Can provide a magnetic carrier that does not.

1 is a schematic diagram of an image forming apparatus used in the present invention. 1 is a schematic diagram of an image forming apparatus used in the present invention. It is the schematic of the measuring apparatus of the specific resistance of the magnetic carrier used by this invention.

The magnetic carrier of the present invention is a magnetic carrier in which a porous ferrite core material is coated with a resin, and the porous ferrite core material has a magnetization strength when an external magnetic field of 5000 / 4π (kA / m) is applied. (Σn) is 55 Am ² / kg or more and 70 Am ² / kg or less, the pore volume is 60 mm ³ / g or more and 120 mm ³ / g or less, the peak pore diameter is 0.40 μm or more and 0.90 μm or less, and the volume distribution The reference 50% particle size (D50) is 25 μm or more and 60 μm or less, and in powder X-ray diffraction measurement, the maximum peak intensity at 20 deg ≦ 2θ ≦ 40 deg satisfies the relationship of Equation 1, that is, the magnetization strength ( .sigma.n) is the maximum peak intensity at 70 Am ² / kg and P _70, the magnetization intensity (.sigma.n) is a maximum peak intensity in the range of 55 ≦ n ≦ 70Am ² / kg was P _n In case,
1.00 ≧ P _n / P ₇₀ ≧ (2σn−65) / 75 (Formula 1)
It is characterized by being.

  In the porous ferrite core material used in the present invention, the maximum peak intensity at 20 deg ≦ 2θ ≦ 40 deg satisfies the relationship of Formula 1 in the powder X-ray diffraction measurement.

When the maximum peak value in the saturation magnetization ₇₀ Am ² / kg is P ₇₀ and the saturation magnetization (n) is the maximum peak value in the range of 55 ≦ n ≦ 70 Am ² / kg, P _n ,
1.00 ≧ P _n / P ₇₀ ≧ (2σn−65) / 75 (Formula 1)
It is. The maximum peak intensity in the measurement range indicates a characteristic peak of magnetite. The peak intensity tends to increase as the magnetization intensity increases. In general, as the magnetization intensity increases, the specific resistance decreases, and as the magnetization intensity decreases, the specific resistance tends to increase. In the case of the relationship of the above formula 1, it is suggested that the change in the peak intensity is small with respect to the change in the magnetization intensity. The change in the peak intensity indicates the change in the crystal structure of the magnetite component, and the small change indicates that the range of the intensity of the magnetization to be used becomes wider. In addition, since the change in specific resistance is small with respect to the change in the intensity of magnetization, leakage resistance can be improved.

The magnetization strength of the porous ferrite core material used in the present invention is preferably 55 Am ² / kg or more and 70 Am ² / kg or less. When it is less than the above range, white spots tend to deteriorate. On the other hand, when the above range is exceeded, there is a concern about deterioration of the roughness resistance.

The pore volume of the porous ferrite core material used in the present invention is preferably 60 mm ³ / g or more and 120 mm ³ / g or less. When the pore volume is less than 60 mm ³ / g, the particle strength becomes high, which may damage the members of the electrophotographic apparatus, and image defects may occur after durability. When it exceeds 120 mm ³ / g, the particle strength becomes low and carrier adhesion due to scattering of the magnetic carrier tends to occur.

  The peak pore diameter of the porous ferrite core material used in the present invention is preferably 0.40 μm or more and 0.90 μm or less. When the peak pore diameter is less than 0.40 μm, the particle strength becomes high, which may damage the members of the electrophotographic apparatus, and image defects may occur after durability. Furthermore, since the irregularities on the surface of the magnetic carrier particles tend to be smooth, the magnetic carrier particle surface is likely to be contaminated by components such as toner particles and external additives, resulting in problems caused by a decrease in charge imparting ability. It becomes easy. On the other hand, when it exceeds 0.90 μm, the particle strength becomes low, cracks and chips are likely to occur, and carrier adhesion due to scattering of magnetic carriers is likely to occur.

  The volume distribution standard 50% particle diameter (D50) of the porous ferrite core material used in the present invention is preferably 25 μm or more and 60 μm or less. When the thickness is less than 25 μm, the carrier adhesion tends to increase. On the other hand, when the thickness exceeds 60 μm, the charge-imparting ability decreases, and there is a concern that the anti-rusting property or the developability may deteriorate.

The magnetic carrier of the present invention has a specific resistance of 2.0 × 10 ⁶ Ω · cm or more and 1.0 × 10 ⁹ Ω · cm or less at an electric field strength of 2000 V / cm.

When the specific resistance is less than 2.0 × 10 ⁶ Ω · cm, there is a concern about deterioration of the rust resistance, and when the specific resistance exceeds 1.0 × 10 ⁹ Ω · cm, white spots tend to deteriorate. is there.

  The magnetic carrier of the present invention is a magnetic carrier filled with 3.0 to 7.0 parts by mass of silicone resin or acrylic resin with respect to 100 parts by mass of the porous ferrite core material.

  When the amount of the filled resin is less than 3.0 parts by mass, the surface layer resistance tends to be low, and the coating film of the coating layer becomes unstable, so that the gas resistance and concentration stability tend to decrease. On the other hand, when it exceeds 7.0 parts by mass, the surface layer resistance tends to be high, and the coating layer becomes a thick film.

  The magnetic carrier of the present invention is a magnetic carrier coated with 1.0 to 3.0 parts by mass of a silicone resin or an acrylic resin with respect to 100 parts by mass of the porous ferrite core material.

  When the amount of the coating resin is less than 1.0 part by mass, the surface layer resistance tends to be low, the coating film of the coating layer becomes unstable, and the charge imparting ability also decreases, resulting in a decrease in dust resistance and concentration stability. Tend to. When the amount exceeds 3.0 parts by mass, the surface layer resistance tends to be high and the coating layer becomes a thick film.

  Next, the manufacturing method of the magnetic carrier of this invention is demonstrated.

(Method for producing porous magnetic core particles)
The porous magnetic core particle of the present invention can be produced by the following steps.

  The material of the porous magnetic core particles is preferably ferrite because the porous structure of the porous magnetic core particles can be controlled and the resistance can be adjusted.

Ferrite is a sintered body represented by the following general formula.
(M1 ₂ O) _x (M2O) _y (Fe ₂ O ₃ ) _z
(In the formula, M1 is a monovalent metal, M2 is a divalent metal, and when x + y + z = 1.0, x and y are 0 ≦ (x, y) ≦ 0.8 and z Is 0.2 <z <1.0.)

  The magnetic carrier is required to maintain a moderate amount of magnetization, to make the pore diameter within a desired range, and to make the uneven state on the surface of the porous magnetic core particle suitable. Moreover, it is required that the rate of the ferritization reaction can be easily controlled and the specific resistance and magnetic force of the porous magnetic core can be suitably controlled. Mn-based ferrite, Mn-Mg-based ferrite, and Mn-Mg-Sr-based ferrite are exemplified from the relationship between specific resistance and magnetic force. Among these, Mn-Mg-Sr-based ferrite is most preferable.

  In addition, controlling the content of a trace amount of impurities contained in the ferrite raw material is very important in producing a porous ferrite core material.

  Specific examples include compounds containing elements such as Cl, Al, Ca, P, and S, but the content of the elements when the composition analysis is performed by fluorescent X-rays after the granulation step is 0. When the content is 2% by mass or less, the grain growth can be made uniform, and a porous magnetic core having a relatively uniform grain diameter can be obtained. By doing so, the strength of the particles is secured even as a porous magnetic core.

  Below, the manufacturing process in the case of using a ferrite as a porous magnetic core particle is demonstrated in detail.

-Process 1 (weighing / mixing process):
The ferrite raw materials are weighed and mixed. Examples of the mixing apparatus include the following. Ball mill, planetary mill, Giotto mill, vibration mill. A ball mill is particularly preferable from the viewpoint of mixing properties. Specifically, a weighed ferrite raw material and balls are placed in a ball mill, and pulverized and mixed for 0.1 to 20.0 hours.

-Process 2 (temporary baking process):
The pulverized and mixed ferrite raw material is pelletized using a pressure molding machine or the like, and then calcined. As described above, since the pre-baking step is important for obtaining the magnetic carrier of the present invention, it is important to perform under the above-described conditions. For example, pre-baking is performed for 3 hours or more and 5.0 hours or less in a temperature range of 1000 ° C. or higher and 1100 ° C. or lower to make the raw material ferrite. At this time, the charging amount is appropriately adjusted so that the ferritization reaction proceeds sufficiently. Moreover, it is preferable to make the environment in which the ferritization reaction proceeds more easily by adjusting the atmosphere, particularly by reducing the oxygen concentration such as in a nitrogen atmosphere. For firing, for example, the following furnace is used. Examples thereof include a burner type firing furnace, a rotary type firing furnace, and an electric furnace. In the present invention, it is important to sufficiently advance the ferritization reaction in the preliminary firing step. By doing so, it is possible to obtain a ferrite in which the crystal state hardly changes even if the magnetization amount changes.

-Step 3 (grinding step):
The calcined ferrite produced in step 2 is pulverized with a pulverizer. The pulverizer is not particularly limited as long as a desired particle size can be obtained.

  Further, controlling the particle size and particle size distribution of the finely pulverized product has a correlation with the pore size of the porous magnetic core particles and the degree of irregularities on the surface of the magnetic carrier.

In order to control the particle size distribution of the finely pulverized product of calcined ferrite, for example, it is preferable to control the ball and bead materials used in the ball mill and bead mill and the operation time. Specifically, in order to reduce the particle size of the calcined ferrite, a ball having a high specific gravity may be used or the pulverization time may be increased. The material for the balls and beads is not particularly limited as long as a desired particle size and distribution can be obtained. For example, the following are mentioned. Glasses such as soda glass (specific gravity 2.5 g / cm ³ ), sodaless glass (specific gravity 2.6 g / cm ³ ), high specific gravity glass (specific gravity 2.7 g / cm ³ ), quartz (specific gravity 2.2 g / cm) ³ ), titania (specific gravity 3.9 g / cm ³ ), silicon nitride (specific gravity 3.2 g / cm ³ ), alumina (specific gravity 3.6 g / cm ³ ), zirconia (specific gravity 6.0 g / cm ³ ), steel ( Specific gravity 7.9 g / cm ³ ), stainless steel (specific gravity 8.0 g / cm ³ ). Among these, alumina, zirconia, and stainless steel are preferable because of excellent wear resistance. The particle size of the ball or bead is not particularly limited as long as a desired particle size / distribution is obtained. For example, a ball having a diameter of 4 mm or more and 60 mm or less is preferably used. Also, beads having a diameter of 0.03 mm to 5 mm are preferably used. In the ball mill and bead mill, the wet type is higher than the dry type in that the pulverized product does not rise in the mill and the pulverization efficiency is higher. For this reason, the wet type is more preferable than the dry type.

-Process 4 (granulation process):
To the finely pulverized product of calcined ferrite, a dispersant, water, a binder and, if necessary, a pore adjusting agent may be added. Examples of the pore adjuster include a foaming agent and resin fine particles. For example, polyvinyl alcohol is used as the binder. In Step 3, when wet pulverization is performed, it is preferable to add a binder and, if necessary, a pore adjuster, taking into account the water contained in the ferrite slurry.

  The obtained ferrite slurry is dried and granulated using a spray dryer in a heated atmosphere at a temperature of 100 ° C. or higher and 200 ° C. or lower. The spray dryer is not particularly limited as long as a desired particle size can be obtained. For example, a spray dryer can be used.

  Next, the dispersant and the binder are burned and removed from the granulated product at a temperature of 600 ° C. or higher and 800 ° C. or lower.

-Process 5 (main baking process):
Thereafter, firing is performed in an electric furnace in which the oxygen concentration can be controlled at a temperature of 1000 ° C. to 1300 ° C. for 1 hour to 24 hours in an atmosphere in which the oxygen concentration is controlled. By controlling the temperature, the pore volume can be controlled. For example, by increasing the temperature, the pore volume decreases. The pore volume of the porous magnetic core particles is preferably 60.0 mm ³ / g or more and 120.0 mm ³ / g or less.

  It is preferable to use a range of 700 ° C. to 1200 ° C., which is a temperature range in which the ferritization reaction proceeds, while maintaining the top temperature at 3 hours or more and 5 hours or less. At that time, use a batch-type electric furnace or a continuous electric furnace, and control the oxygen concentration by injecting an inert gas such as nitrogen or a reducing gas such as hydrogen or carbon monoxide into the firing atmosphere. May be.

  In the present invention, a batch type electric furnace or a continuous type electric furnace is preferable as an apparatus used for the main firing and oxidation treatment. A rotary electric furnace can also be used. However, in the case of a rotary electric furnace, compared to the above two electric furnaces, a difference occurs in the ferritization reaction, and when the oxidation treatment is performed, saturation magnetization and The relationship of peak intensity cannot satisfy Equation 1. This is considered to be caused by a difference in crystal growth. In the case of a rotary electric furnace, only the vicinity of the extreme surface layer tends to be oxidized.

-Process 6 (screening process):
After crushing the fired particles, if necessary, the low-magnetic force product is separated by magnetic separation. Coarse particles and fine particles may be removed by sieving with air classification or sieving.

・ Surface treatment process:
If necessary, the resistance can be adjusted by applying an oxide film treatment by heating the surface at a low temperature. The oxide film treatment can be performed using a batch electric furnace or the like, for example, at 300 ° C. or more and 700 ° C. or less.

  The volume distribution standard 50% particle diameter (D50) of the porous magnetic core particles obtained as described above is preferably 25.0 μm or more and 60.0 μm or less. As a result, the triboelectric chargeability of the toner is improved, the image quality of the halftone portion is satisfied, fogging can be suppressed, and carrier adhesion can be prevented.

(Method for producing resin-filled magnetic core particles)
As a method for filling the pores of the porous magnetic core with the filling resin composition, a method of diluting the filling resin in a solvent, adding this to the pores of the porous magnetic core, and removing the solvent can be employed. The solvent used here may be any solvent that can dissolve the filling resin. Examples of the organic solvent include toluene, xylene, cellosolve butyl acetate, methyl ethyl ketone, methyl isobutyl ketone, and methanol. As a method of filling the pores of the porous magnetic core with resin, the resin solution is impregnated with the porous magnetic core by a coating method such as dipping, spraying, brushing, and fluidized bed, and then the solvent is added. The method of volatilizing is mentioned.

  As the dipping method, a method of filling the pores of the porous magnetic core particles with a filled resin composition solution in which a filled resin and a solvent are mixed under reduced pressure, and removing the solvent by degassing or heating is preferable.

  In the present invention, it is preferable to control the impregnation property of the filled resin composition into the pores of the porous magnetic core particles by controlling the solvent removal speed by the deaeration time. Since the filled resin impregnates the pores by capillary action, the longer the time, the more the resin is impregnated inside the porous magnetic core.

  After the filling resin composition is filled, the filling resin composition is heated by various methods as necessary, and the filled filling resin composition is brought into close contact with the porous magnetic core particles. The heating method may be either an external heating method or an internal heating method, for example, a fixed or fluid electric furnace, a rotary electric furnace, a burner furnace, or a microwave baking.

  Since the resin solid content in the filled resin composition solution is 6 mass% or more and 50 mass% or less, the handling of the viscosity of the filled resin composition solution is good. It is preferable from the viewpoint.

  Although it does not specifically limit as filling resin in the filling resin composition with which the void | hole of a porous magnetic core is filled, Resin with high impregnation property is preferable. When a highly impregnated resin is used, the pores in the vicinity of the surface of the filled core particle remain by filling from the pores inside the porous magnetic core particle, and the surface of the resin-filled magnetic core particle depends on the pore. Since it has an uneven shape, it is preferable from the viewpoint of the surface tension of the coating resin composition as described above.

  The filling resin in the filling resin composition may be either a thermoplastic resin or a thermosetting resin, but when coating a magnetic carrier, a thermosetting resin that does not melt even if a solvent is used during coating. In view of ease of filling, a silicone resin is preferable. For example, the following are mentioned as a commercial item. Among straight silicone resins, KR-271, KR-251 and KR-255 manufactured by Shin-Etsu Chemical Co., Ltd., SR2400, SR2405, SR2410 and SR2411 manufactured by Toray Dow Corning Co., Ltd. Among the modified silicone resins, KR206 (alkyd modified), KR5208 (acryl modified), ES1001N (epoxy modified), and SR2110 (alkyd modified) manufactured by Shin-Etsu Chemical Co., Ltd. are used.

  Moreover, it is preferable that the filling resin composition contains a silane coupling agent. The silane coupling agent has good compatibility with the filled resin, and the wettability and adhesion between the porous magnetic core particles and the filled resin are further increased. Therefore, the filling resin is filled from the pores inside the porous magnetic core particles. As a result, since the surface of the resin-filled magnetic core particles has an uneven shape due to the pores, it is preferable from the viewpoint of the surface tension of the coating resin composition as described above.

  Although it does not specifically limit as a silane coupling agent to be used, Since an affinity with a coating resin composition also becomes favorable because a functional group exists, an aminosilane coupling agent is preferable.

  The reason why the aminosilane coupling agent enhances the wettability and adhesion between the porous magnetic core particles and the filling resin and improves the affinity with the coating resin composition is considered as follows. The aminosilane coupling agent has a part that reacts with an inorganic substance and a part that reacts with an organic substance. In general, an alkoxy group is considered to react with an inorganic substance and a functional group having an amino group reacts with an organic substance. Therefore, the alkoxy group of the aminosilane coupling agent reacts with the portion of the porous magnetic core particle to improve wettability and adhesion, and the functional group having an amino group is oriented to the filling resin side to cover the surface. It is considered that the affinity with the resin composition is also increased.

  The amount of the silane coupling agent to be added is preferably 1.0 to 20.0 parts by mass with respect to 100 parts by mass of the filled resin. More preferably, it is 5.0 to 10.0 parts by mass from the viewpoint of improving wettability and adhesion between the porous magnetic core particles and the filling resin.

  The filling resin can also be used as a coating resin.

(Method for manufacturing magnetic carrier)
The method of coating the surface of the resin-filled magnetic core particles with the coating resin composition is not particularly limited, but there are methods of treating by a coating method such as a dipping method, a spray method, a brush coating method, a dry method, and a fluidized bed. Can be mentioned. Among these, in order to take advantage of the unevenness characteristic of the surface of the porous magnetic core particle, an immersion method that can control the ratio of the thin part and the thick part of the coating layer is more preferable from the viewpoint of improving developability. The reason why the developability is improved is considered as follows. This is because, due to the uneven shape of the porous magnetic core particles, the coating resin composition layer can have both a thin film portion and a thick film portion, so that the locally existing thin film portion acts as a charge relaxation effect.

  For the adjustment of the coating resin composition solution to be coated, the same method as in the filling step is used. Examples of methods for suppressing granulation during the coating process include adjustment of the resin concentration in the coating resin composition solution, the temperature in the apparatus to be coated, the temperature and degree of vacuum when removing the solvent, and the number of resin coating processes. It is done.

  The resin of the coating resin composition used for the coating layer is not particularly limited, but a vinyl resin that is a copolymer of a vinyl monomer having a cyclic hydrocarbon group in the molecular structure and another vinyl monomer is preferable. . By covering the vinyl resin, it is possible to suppress a decrease in charge amount in a high temperature and high humidity environment.

  In addition, the cause which suppresses the fall of the charge amount in a high-temperature, high-humidity environment by coat | covering this vinyl-type resin is considered as follows. When the vinyl resin is coated on the surface of the resin-filled magnetic core particles, a coating process in which the vinyl resin is dissolved in an organic solvent and the resin-filled magnetic core particles are mixed and desolvated. Go through. In this process, the solvent is removed while the cyclic hydrocarbon group is oriented on the surface of the coating resin layer, and the surface of the completed magnetic carrier is in a state where the highly hydrophobic cyclic hydrocarbon group is oriented. This is because a coating resin layer is formed.

  Specific examples of the cyclic hydrocarbon group include cyclic hydrocarbon groups having 3 to 10 carbon atoms, such as cyclohexyl group, cyclopentyl group, adamantyl group, cyclopropyl group, cyclobutyl group, cycloheptyl group, and cyclooctyl group. , Cyclononyl group, cyclodecyl group, isobornyl group, norbornyl group, boronyl group and the like. Among these, a cyclohexyl group, a cyclopentyl group, and an adamantyl group are preferable, and a cyclohexyl group is particularly preferable from the viewpoint of high structural stability and adhesion to the resin-filled magnetic core particles.

  Moreover, in order to adjust a glass transition temperature (Tg), you may contain another monomer as a structural component of vinyl-type resin.

  As another monomer used as a constituent component of the vinyl resin, a known monomer is used, and examples thereof include the following. Examples include styrene, ethylene, propylene, butylene, butadiene, vinyl chloride, vinylidene chloride, vinyl acetate, methyl methacrylate, ethyl methacrylate, propyl methacrylate, vinyl methyl ether, vinyl ethyl ether, and vinyl methyl ketone.

  Furthermore, the vinyl resin used for the coating layer is preferably a graft polymer because wettability with the porous magnetic core particles is further improved and a uniform coating layer is formed.

  In order to obtain a graft polymer, there are a method of graft polymerization after forming a backbone, and a method of copolymerization using a macromonomer as a monomer. It is preferable because it can be easily controlled.

  The macromonomer used is not particularly limited, but a methyl methacrylate macromonomer is preferable because wettability with the porous magnetic core is further improved.

  The amount used when polymerizing the macromonomer is preferably 10 to 50 parts by mass, more preferably 20 to 40 parts by mass, with respect to 100 parts by mass of the vinyl resin backbone copolymer.

  Further, the coating resin composition may be used by containing conductive particles or charge controllable particles or materials. Examples of the conductive particles include carbon black, magnetite, graphite, zinc oxide, and tin oxide. Among these, by making the filler effect of carbon black act suitably, the surface tension of a coating resin composition can be acted suitably, and it is preferable from a viewpoint of improving the coating property of a coating resin composition.

  In addition, the reason which can improve the coating property of a coating resin composition by making the filler effect of carbon black act suitably originates in the primary particle diameter and cohesiveness of carbon black. That is, since carbon black has a small primary particle size, it exhibits a large specific surface area. On the other hand, since carbon black has high cohesiveness, it exists as large particles as aggregated particles. Due to the primary particle size and the cohesiveness, the particles can greatly deviate from the relationship between the particle size and the specific surface area. That is, the particle diameter is such that the surface tension of the coating resin composition acts, and the contact point is large due to the size of the specific surface area, so the surface tension of the coating resin composition is likely to act.

  The addition amount of the conductive particles is preferably 0.1 parts by mass or more and 10.0 parts by mass or less with respect to 100 parts by mass of the coating resin in order to adjust the resistance of the magnetic carrier. The particles having charge controllability include organometallic complex particles, organometallic salt particles, chelate compound particles, monoazo metal complex particles, acetylacetone metal complex particles, hydroxycarboxylic acid metal complex particles, and polycarboxylic acid metal particles. Complex particles, polyol metal complex particles, polymethyl methacrylate resin particles, polystyrene resin particles, melamine resin particles, phenol resin particles, nylon resin particles, silica particles, titanium oxide particles, alumina particles, etc. Can be mentioned. The addition amount of the particles having charge controllability is preferably 0.5 parts by mass or more and 50.0 parts by mass or less with respect to 100 parts by mass of the coating resin in order to adjust the triboelectric charge amount.

  The above coating resin can also be used as a filling resin.

  Next, a preferable toner configuration for achieving the object in the present invention will be described in detail below.

  Examples of the binder resin used in the present invention include vinyl resins, polyester resins, and epoxy resins. Of these, vinyl resins and polyester resins are more preferable in terms of chargeability and fixability. In particular, when a polyester resin is used, the effect of introducing this apparatus is great.

  In the present invention, vinyl monomer monopolymer or copolymer, polyester, polyurethane, epoxy resin, polyvinyl butyral, rosin, modified rosin, terpene resin, phenol resin, aliphatic or alicyclic hydrocarbon resin, aromatic Petroleum resin or the like can be mixed with the above-described binder resin as necessary.

  When two or more kinds of resins are mixed and used as a binder resin, it is preferable that those having different molecular weights are mixed in an appropriate ratio as a more preferable form.

  The glass transition temperature of the binder resin is preferably 45 to 80 ° C., more preferably 55 to 70 ° C., the number average molecular weight (Mn) is 2,500 to 50,000, and the weight average molecular weight (Mw) is 10,000. It is preferable to be 1,000,000.

  As the binder resin, the following polyester resins are also preferable.

  In the polyester resin, 45 to 55 mol% of all components is an alcohol component, and 55 to 45 mol% is an acid component.

  The acid value of the polyester resin is preferably 90 mgKOH / g or less, more preferably 50 mgKOH / g or less, and the OH value is preferably 50 mgKOH / g or less, more preferably 30 mgKOH / g or less. This is because as the number of terminal groups of the molecular chain increases, the dependency of the toner on the environment increases in the environment.

  The glass transition temperature of the polyester resin is preferably 50 to 75 ° C, more preferably 55 to 65 ° C. The number average molecular weight (Mn) is preferably 1,500 to 50,000, more preferably 2,000 to 20,000. The weight average molecular weight (Mw) is preferably 6,000 to 100,000, more preferably 10,000 to 90,000.

  When the toner of the present invention is used as a magnetic toner, the magnetic material contained in the magnetic toner includes iron oxides such as magnetite, maghemite and ferrite, and iron oxides including other metal oxides; Fe, Co, Ni, etc. Metals or alloys of these metals with metals such as Al, Co, Cu, Pb, Mg, Ni, Sn, Zn, Sb, Be, Bi, Cd, Ca, Mn, Se, Ti, W, V , And mixtures thereof.

Specifically, examples of magnetic materials include triiron tetroxide (Fe ₃ O ₄ ), iron sesquioxide (γ-Fe ₂ O ₃ ), iron oxide zinc (ZnFe ₂ O ₄ ), and iron yttrium oxide (Y ₃ Fe). ₅ O ₁₂ ), iron cadmium oxide (CdFe ₂ O ₄ ), iron gadolinium oxide (Gd ₃ Fe ₅ O ₁₂ ), copper iron oxide (CuFe ₂ O ₄ ), lead iron oxide (PbFe ₁₂ O ₁₉ ), nickel iron oxide (NiFe ₂ O ₄ ), iron neodymium oxide (NdFe ₂ O ₃ ), iron barium oxide (BaFe ₁₂ O ₁₉ ), iron magnesium oxide (MgFe ₂ O ₄ ), iron manganese oxide (MnFe ₂ O ₄ ), iron lanthanum oxide (LaFeO ₃ ), iron powder (Fe), cobalt powder (Co), nickel powder (Ni) and the like.

  These may be used in an amount of 20 to 150 parts by mass, preferably 50 to 130 parts by mass, and more preferably 60 to 120 parts by mass with respect to 100 parts by mass of the binder resin.

  The following are mentioned as a nonmagnetic coloring agent used by this invention.

  Examples of the black colorant include carbon black; those adjusted to black using a yellow colorant, a magenta colorant, and a cyan colorant.

  Examples of the color pigment for magenta toner include the following. Examples include condensed azo compounds, diketopyrrolopyrrole compounds, anthraquinones, quinacridone compounds, basic dye lake compounds, naphthol compounds, benzimidazolone compounds, thioindigo compounds, and perylene compounds. Specifically, C.I. I. Pigment Red 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 21, 22, 23, 30, 31, 32, 37, 38, 39, 40, 41, 48: 2, 48: 3, 48: 4, 49, 50, 51, 52, 53, 54, 55, 57: 1, 58, 60, 63, 64, 68, 81: 1, 83, 87, 88, 89, 90, 112, 114, 122, 123, 144, 146, 150, 163, 166, 169, 177, 184, 185, 202, 206, 207, 209, 220, 221, 238, 254, 269; I. Pigment violet 19, C.I. I. Bat red 1, 2, 10, 13, 15, 23, 29, 35 are mentioned.

  The colorant may be used alone as a pigment, but it is preferable from the viewpoint of the image quality of a full-color image to improve the sharpness by using a dye and a pigment together.

  Examples of the magenta toner dye include the following. C. I solvent red 1, 3, 8, 23, 24, 25, 27, 30, 49, 81, 82, 83, 84, 100, 109, 121, C.I. I. Disper thread 9, C.I. I. Solvent Violet 8, 13, 14, 21, 27, C.I. I. Oil-soluble dyes such as Disper Violet 1, C.I. I. Basic Red 1, 2, 9, 12, 13, 14, 15, 17, 18, 22, 23, 24, 27, 29, 32, 34, 35, 36, 37, 38, 39, 40, C.I. I. Basic dyes such as basic violet 1, 3, 7, 10, 14, 15, 21, 25, 26, 27, 28.

  Examples of the color pigment for cyan toner include the following. C. I. Pigment Blue 1, 2, 3, 7, 15: 2, 15: 3, 15: 4, 16, 17, 60, 62, 66; I. Bat Blue 6, C.I. I. Acid Blue 45, a copper phthalocyanine pigment in which 1 to 5 phthalimidomethyls are substituted on the phthalocyanine skeleton.

  Examples of the color pigment for yellow include the following. Condensed azo compounds, isoindolinone compounds, anthraquinone compounds, azo metal compounds, methine compounds, allylamide compounds. Specifically, C.I. I. Pigment Yellow 1, 2, 3, 4, 5, 6, 7, 10, 11, 12, 13, 14, 15, 16, 17, 23, 62, 65, 73, 74, 83, 93, 95, 97, 109, 110, 111, 120, 127, 128, 129, 147, 155, 168, 174, 180, 181, 185, 191; I. Bat yellow 1, 3, and 20 are mentioned. In addition, C.I. I. Direct Green 6, C.I. I. Basic Green 4, C.I. I. Dyes such as Basic Green 6 and Solvent Yellow 162 can also be used.

  The amount of the colorant used is preferably 0.1 to 30 parts by mass, more preferably 0.5 to 20 parts by mass, and most preferably 3 to 15 parts by mass with respect to 100 parts by mass of the binder resin. is there.

  Further, in the toner, it is preferable to use a toner obtained by mixing a colorant with a binder resin in advance to form a master batch. Then, the colorant can be favorably dispersed in the toner by melt-kneading the colorant master batch and other raw materials (binder resin, wax, etc.).

  In the toner of the present invention, a charge control agent can be used as necessary in order to further stabilize the chargeability. The charge control agent is preferably used in an amount of 0.5 to 10 parts by mass per 100 parts by mass of the binder resin. When the amount is less than 0.5 parts by mass, sufficient charging characteristics may not be obtained, which is not preferable. When the amount exceeds 10 parts by mass, compatibility with other materials is deteriorated or charging is performed under low humidity. It may be excessive, which is not preferable.

  Examples of the charge control agent include the following.

  As a negative charge control agent for controlling the toner to be negative charge, for example, an organometallic complex or a chelate compound is effective. Examples include monoazo metal complexes, aromatic hydroxycarboxylic acid metal complexes, and aromatic dicarboxylic acid metal complexes. Other examples include aromatic hydroxycarboxylic acids, aromatic mono and polycarboxylic acids and metal salts thereof, anhydrides or esters thereof, or phenol derivatives of bisphenol.

  Examples of the positive charge control agent for controlling the toner to be positively charged include modified products such as nigrosine and fatty acid metal salts, tributylbenzylammonium-1-hydroxy-4-naphthosulfonate, tetrabutylammonium tetrafluoroborate and the like. As onium salts such as quaternary ammonium salts and their analogs such as phosphonium salts and their chelating pigments, triphenylmethane dyes and their lake pigments (as rake agents are phosphotungstic acid, phosphomolybdic acid, phosphotungsten) Molybdic acid, tannic acid, lauric acid, gallic acid, ferricyanic acid, ferrocyanic compounds, etc.), diorganotin oxides such as dibutyltin oxide, dioctyltin oxide, dicyclohexyltin oxide and dibutyltin as metal salts of higher fatty acids , Dioctyl tin borate include diorgano tin borate such as dicyclohexyl tin borate.

  In the present invention, if necessary, one or more release agents may be contained in the toner particles. Examples of the release agent include the following.

  Aliphatic hydrocarbon waxes such as low molecular weight polyethylene, low molecular weight polypropylene, microcrystalline wax, and paraffin wax can be preferably used. In addition, oxides of aliphatic hydrocarbon waxes such as oxidized polyethylene wax, or block copolymers thereof; waxes mainly composed of fatty acid esters such as carnauba wax, sazol wax, and montanic ester wax; and Examples include those obtained by partially or fully deoxidizing fatty acid esters such as deoxidized carnauba wax.

  The amount of the release agent is 0.1 to 20 parts by mass, preferably 0.5 to 10 parts by mass, per 100 parts by mass of the binder resin.

  The melting point of the releasing agent defined by the maximum endothermic peak temperature at the time of temperature rise measured by a differential scanning calorimeter (DSC) is preferably 65 to 130 ° C. More preferably, it is 80 to 125 ° C. If the melting point is less than 65 ° C., the viscosity of the toner decreases and toner adhesion to the photoreceptor is likely to occur. If the melting point exceeds 130 ° C., the low-temperature fixability may deteriorate, which is not preferable. .

  In the toner of the present invention, a fine powder that can be increased by adding the toner particles externally before and after the addition may be used as a fluidity improver. For example, fluorine resin powders such as vinylidene fluoride fine powder and polytetrafluoroethylene fine powder; wet production silica, fine powder silica such as dry production silica, fine powder titanium oxide, fine powder alumina, etc., silane coupling agent, titanium It is particularly preferable that the surface treatment is performed with a coupling agent and silicone oil, and the surface is hydrophobized, and the surface is hydrophobized as measured by a methanol titration test so as to show a value in the range of 30 to 80.

  The inorganic fine particles in the present invention are used in an amount of 0.1 to 10 parts by weight, preferably 0.2 to 8 parts by weight, based on 100 parts by weight of the toner.

  When the toner of the present invention is mixed with a magnetic carrier and used as a two-component developer, the carrier mixing ratio at that time is 2% by mass to 15% by mass, preferably 4% by mass as the toner concentration in the developer. When the content is from 13% to 13% by mass, good results are usually obtained. If the toner concentration is less than 2% by mass, the image density tends to decrease, and if it exceeds 15% by mass, fogging or in-machine scattering tends to occur.

  Further, in the replenishment developer for replenishing the developing device in accordance with the decrease in the toner concentration of the two-component developer in the developing device, the toner amount is 2 parts by mass or more and 50 masses per 1 part by mass of the magnetic carrier for replenishment. Or less.

  Next, an image forming apparatus provided with a developing device using the magnetic carrier, the two-component developer and the replenishing developer of the present invention will be described by way of example. The developing device used in the developing method of the present invention is described below. It is not limited to.

<Image forming method>
In FIG. 1, the electrostatic latent image carrier 1 rotates in the direction of the arrow in the figure. The electrostatic latent image carrier 1 is charged by a charger 2 that is a charging unit, and the surface of the charged electrostatic latent image carrier 1 is exposed by an exposure unit 3 that is an electrostatic latent image forming unit. Form an image. The developing device 4 has a developing container 5 for storing a two-component developer, the developer carrying member 6 is disposed in a rotatable state, and a magnetic field generating means is provided inside the developer carrying member 6 to provide a magnet. 7 is included. At least one of the magnets 7 is installed so as to face the latent image carrier. The two-component developer is held on the developer carrier 6 by the magnetic field of the magnet 7, the amount of the two-component developer is regulated by the regulating member 8, and the developer component is opposed to the electrostatic latent image carrier 1. Be transported. In the developing unit, a magnetic brush is formed by a magnetic field generated by the magnet 7. Thereafter, the electrostatic latent image is visualized as a toner image by applying a developing bias in which an alternating electric field is superimposed on a DC electric field. The toner image formed on the electrostatic latent image carrier 1 is electrostatically transferred to a recording medium (transfer material) 12 by a transfer charger 11. Here, as shown in FIG. 2, the image may be temporarily transferred from the electrostatic latent image carrier 1 to the intermediate transfer member 9 and then electrostatically transferred to the recording medium 12. Thereafter, the recording medium 12 is conveyed to a fixing device 13 where the toner is fixed on the recording medium 12 by being heated and pressurized. Thereafter, the recording medium 12 is discharged out of the apparatus as an output image. Incidentally, the toner remaining on the electrostatic latent image carrier 1 after the transfer process is removed by the cleaner 15. Thereafter, the electrostatic latent image carrier 1 cleaned by the cleaner 15 is electrically initialized by the light irradiation from the pre-exposure 16, and the image forming operation is repeated.

  FIG. 2 shows an example of a schematic diagram in which the image forming method of the present invention is applied to a full-color image forming apparatus.

  The arrows indicating the arrangement and rotation direction of image forming units such as K, Y, C, and M in the figure are not limited to these. Incidentally, K means black, Y means yellow, C means cyan, and M means magenta. In FIG. 2, the electrostatic latent image carriers 1K, 1Y, 1C, 1M rotate in the direction of the arrow in the figure. Each electrostatic latent image carrier is charged by charging units 2K, 2Y, 2C, and 2M that are charging means, and an exposure unit 3K that is an electrostatic latent image forming unit is provided on the surface of each charged electrostatic latent image carrier. Exposure is performed with 3Y, 3C, and 3M to form an electrostatic latent image. Thereafter, the electrostatic latent image can be converted into a toner image by the two-component developer carried on the developer carrying members 6K, 6Y, 6C, and 6M provided in the developing devices 4K, 4Y, 4C, and 4M as developing means. Visualized. Further, the image is transferred to the intermediate transfer body 9 by the intermediate transfer chargers 10K, 10Y, 10C, and 10M which are transfer means. Further, the image is transferred to a recording medium 12 by a transfer charger 11 serving as a transfer unit, and the recording medium 12 is heated and pressure-fixed by a fixing unit 13 serving as a fixing unit and output as an image. Then, the intermediate transfer body cleaner 14 which is a cleaning member for the intermediate transfer body 9 collects transfer residual toner and the like. In the developing method of the present invention, specifically, an AC voltage is applied to the developer carrying member to form an alternating electric field in the developing region, and the developing is performed while the magnetic brush is in contact with the photosensitive member. It is preferable. The distance between the developer carrying member (developing sleeve) 6 and the photosensitive drum (distance between S and D) is preferably not less than 100 μm and not more than 1000 μm in terms of preventing carrier adhesion and improving dot reproducibility. If it is smaller than 100 μm, the supply of the developer tends to be insufficient, and the image density is lowered. If it exceeds 1000 μm, the magnetic lines of force from the magnetic pole S1 spread and the density of the magnetic brush is lowered, so that the dot reproducibility is inferior, or the force that restrains the magnetic coat carrier is weakened, and the carrier adheres easily.

  The voltage (Vpp) between peaks of the alternating electric field is 300 V or more and 3000 V or less, preferably 500 V or more and 1800 V or less. The frequency is 500 Hz to 10000 Hz, preferably 1000 to 7000 Hz, and can be appropriately selected depending on the process. In this case, the waveform of the AC bias for forming the alternating electric field includes a triangular wave, a rectangular wave, a sine wave, or a waveform with a changed duty ratio. In order to cope with the change in the formation speed of the toner image sometimes, it is preferable to perform development by applying a developing bias voltage (intermittent alternating voltage) having a discontinuous AC bias voltage to the developer carrier. . When the applied voltage is lower than 300 V, it is difficult to obtain a sufficient image density, and the fog toner in the non-image portion may not be recovered well. If the voltage exceeds 3000 V, the latent image may be disturbed via the magnetic brush, leading to a reduction in image quality.

  By using a two-component developer with well-charged toner, the anti-fogging voltage (Vback) can be lowered and the primary charge of the photoreceptor can be lowered, thus extending the life of the photoreceptor. it can. Vback is 200 V or less, more preferably 150 V or less, although it depends on the development system. The contrast potential is preferably 100 V or more and 400 V or less so that a sufficient image density is obtained.

  Further, when the frequency is lower than 500 Hz, although related to the process speed, the structure of the electrostatic latent image bearing photoconductor may be the same as that of a photoconductor used in an image forming apparatus. For example, a photoreceptor having a structure in which a conductive layer, an undercoat layer, a charge generation layer, a charge transport layer, and a charge injection layer as necessary are provided on a conductive substrate such as aluminum or SUS in order.

  The conductive layer, undercoat layer, charge generation layer, and charge transport layer may be those usually used for a photoreceptor. For example, a charge injection layer or a protective layer may be used as the outermost surface layer of the photoreceptor.

<Measurement of resistivity of magnetic carrier>
The specific resistances of the magnetic carrier and the porous magnetic core are measured using a measuring apparatus schematically shown in FIG. The magnetic carrier measures the specific resistance at an electric field strength of 2000 (V / cm).

The resistance measurement cell A is a cylindrical container (made of PTFE resin) 17 having a hole with a cross-sectional area of 2.4 cm ² , a lower electrode (made of stainless steel) 18, a support base (made of PTFE resin) 19, and an upper electrode (made of stainless steel). 20 is comprised. The cylindrical container 18 is placed on the support pedestal 19, the sample (magnetic carrier or porous magnetic core) 21 is filled to a thickness of about 1 mm, the upper electrode 20 is placed on the filled sample 5, and the thickness of the sample is set. Measure. As shown in FIG. 3A, when the gap when there is no sample is d1, and when the gap is d2 when the sample is filled to a thickness of about 1 mm as shown in FIG. d is calculated by the following equation.
d = d2-d1 (mm)

  At this time, the mass of the sample is appropriately changed so that the thickness d of the sample is 0.95 mm or more and 1.04 mm or less.

  The specific resistance of the sample can be determined by applying a DC voltage between the electrodes and measuring the current flowing at that time. For the measurement, an electrometer 22 (Kesley 6517A, manufactured by Kesley) and a processing computer 23 are used for control.

  A control system and control software (LabVEIW National Instruments) manufactured by National Instruments were used as a control processing computer.

As measurement conditions, a measured value d is inputted so that the contact area S of the sample and the electrode is S = 2.4 cm ² and the thickness of the sample is 0.95 mm or more and 1.04 mm or less. The upper electrode load is 270 g and the maximum applied voltage is 1000 V.
Specific resistance (Ω · cm) = (applied voltage (V) / measured current (A)) × S (cm ² ) / d (cm)
Electric field strength (V / cm) = applied voltage (V) / d (cm)

  The specific resistance at the electric field strength of the magnetic carrier and the porous magnetic core is read from the graph of the specific resistance at the electric field strength on the graph.

<Measuring method of volume average particle diameter (D50) of magnetic carrier and porous magnetic core>
The particle size distribution was measured with a laser diffraction / scattering particle size distribution measuring apparatus “Microtrack MT3300EX” (manufactured by Nikkiso Co., Ltd.).

The volume average particle diameter (D50) of the magnetic carrier and the porous magnetic core was measured by mounting a sample feeder “One Shot Dry Sample Conditioner Turbotrac” (manufactured by Nikkiso Co., Ltd.) for dry measurement. As the supply conditions of Turbotrac, a dust collector was used as a vacuum source, the air volume was about 33 l / sec, and the pressure was about 17 kPa. Control is automatically performed on software. For the particle size, a 50% particle size (D50), which is a cumulative value of volume average, is obtained. Control and analysis are performed using attached software (version 10.3.3-202D). The measurement conditions are as follows.
SetZero time: 10 seconds Measurement time: 10 seconds Number of measurements: 1 time Particle refractive index: 1.81%
Particle shape: Non-spherical measurement upper limit: 1408 μm
Measurement lower limit: 0.243 μm
Measurement environment: 23 ° C., 50% RH

<Measurement of pore diameter and pore volume of porous magnetic core>
The pore size distribution of the porous magnetic core is measured by a mercury intrusion method.

  The measurement principle is as follows.

  In this measurement, the pressure applied to mercury is changed, and the amount of mercury that has entered the pores at that time is measured. The conditions under which mercury can enter the pores can be expressed as PD = −4σCOSθ from the following balance, assuming that pressure P, pore diameter D, mercury contact angle and surface tension are θ and σ, respectively. If the contact angle and the surface tension are constants, the pressure P and the pore diameter D into which mercury can enter at that time are inversely proportional. For this reason, the horizontal axis P of the PV curve, which can be measured by changing the pressure P and the amount of infiltrated liquid V at that time, is directly replaced with the pore diameter from this equation to obtain the pore distribution. Yes.

  As a measuring device, it is possible to measure using a fully automatic multifunctional mercury porosimeter, PoleMaster series / PoreMaster-GT series manufactured by Yuasa Ionics, or an automatic porosimeter autopore IV 9500 series manufactured by Shimadzu Corporation.

  Specifically, the measurement was performed under the following conditions and procedures using Autopore IV9520 manufactured by Shimadzu Corporation.

Measurement conditions Measurement environment 20 ℃
Measurement cell Sample volume 5 cm ³ , press-fit volume 1.1 cm ³ , measurement range for powder use 2.0 psia (13.8 kPa) or more and 59989.6 psia (413.7 kPa) or less Measurement step 80 steps
(When taking the logarithm of the pore diameter as a logarithm, ticks the steps so that they are equally spaced)
Press-in parameters Exhaust pressure 50μmHg
Exhaust time 5.0min
Mercury injection pressure 2.0 psia (13.8 kPa)
Equilibrium time 5 secs
High pressure parameter Equilibrium time 5 secs
Mercury parameter advancing contact angle 130.0 degrees
Receding contact angle 130.0 degrees
Surface tension 485.0 mN / m (485.0 dynes / cm)
Mercury density 13.5335 g / mL

Measurement procedure (1) About 1.0 g of a porous magnetic core is weighed and placed in a sample cell.
Enter the weighing value.
(2) In the low pressure part, a range of 2.0 psia (13.8 kPa) to 45.8 psia (315.6 kPa) is measured.
(3) Measure the range of 45.9 psia (316.3 kPa) or more and 59989.6 psia (413.6 kPa) or less in the high pressure section.
(4) The pore size distribution is calculated from the mercury injection pressure and the mercury injection amount.

  (2), (3), and (4) were automatically performed by software attached to the apparatus.

  From the pore diameter distribution measured as described above, the pore diameter that maximizes the differential pore volume in the pore diameter range of 0.1 μm to 3.0 μm is read, and the differential pore volume is maximized. The pore diameter.

  Moreover, the pore volume which integrated the differential pore volume in the range of 0.1 micrometer or more and 3.0 micrometer or less pore diameter was computed using attached software.

<Measuring method of weight average particle diameter (D4) and number average particle diameter (D1)>
The weight average particle diameter (D4) and number average particle diameter (D1) of the toner are measured by a fine particle size distribution measuring apparatus “Coulter Counter Multisizer 3” (registered trademark, Beckman And a dedicated software “Beckman Coulter Multisizer 3 Version 3.51” (manufactured by Beckman Coulter, Inc.) for setting measurement conditions and analyzing measurement data were used. Measurement was performed with 25,000 effective measurement channels, and measurement data was analyzed and calculated.

  As the electrolytic aqueous solution used for the measurement, special grade sodium chloride is dissolved in ion-exchanged water so as to have a concentration of about 1% by mass, for example, “ISOTON II” (manufactured by Beckman Coulter, Inc.) can be used.

  Prior to measurement and analysis, the dedicated software was set as follows.

  In the “Standard Measurement Method (SOM) Change Screen” of the dedicated software, set the total count in the control mode to 50000 particles, set the number of measurements once, and set the Kd value to “standard particles 10.0 μm” (Beckman Coulter, Inc.) Set the value obtained using The threshold and noise level are automatically set by pressing the threshold / noise level measurement button. Also, the current is set to 1600 μA, the gain is set to 2, the electrolyte is set to ISOTON II, and the aperture tube flash after measurement is checked.

  In the “pulse to particle size conversion setting screen” of the dedicated software, the bin interval is set to logarithmic particle size, the particle size bin is set to 256 particle size bin, and the particle size range is set to 2 μm to 60 μm.

The specific measurement method is as follows.
(1) About 200 ml of the electrolytic solution is placed in a glass 250 ml round bottom beaker exclusively for Multisizer 3, set on a sample stand, and the stirrer rod is stirred counterclockwise at 24 rpm. Then, dirt and bubbles in the aperture tube are removed by the “aperture flush” function of the analysis software.
(2) About 30 ml of the electrolytic aqueous solution is put into a glass 100 ml flat bottom beaker. In this, "Contaminone N" (nonionic surfactant, anionic surfactant, 10% by weight aqueous solution of neutral detergent for pH7 precision measuring instrument cleaning, made by organic builder, manufactured by Wako Pure Chemical Industries, Ltd. About 0.3 ml of a diluted solution obtained by diluting 3) with ion-exchanged water is added.
(3) Two oscillators with an oscillation frequency of 50 kHz are incorporated in a state where the phase is shifted by 180 degrees, and placed in a water tank of an ultrasonic dispersion device “Ultrasonic Dissipation System Tetora 150” (manufactured by Nikki Bios Co., Ltd.) having an electrical output of 120 W. Add a fixed amount of ion-exchanged water. About 2 ml of the aforementioned contamination N is added to this water tank.
(4) The beaker of (2) is set in the beaker fixing hole of the ultrasonic disperser, and the ultrasonic disperser is operated. And the height position of a beaker is adjusted so that the resonance state of the liquid level of the electrolyte solution in a beaker may become the maximum.
(5) In a state where the electrolytic aqueous solution in the beaker of (4) is irradiated with ultrasonic waves, about 10 mg of toner is added to the electrolytic aqueous solution little by little and dispersed. Then, the ultrasonic dispersion process is continued for another 60 seconds. In the ultrasonic dispersion, the temperature of the water tank is appropriately adjusted so as to be 10 ° C. or higher and 40 ° C. or lower.
(6) To the round bottom beaker of (1) installed in the sample stand, the electrolyte solution of (5) in which the toner is dispersed is dropped using a pipette, and the measurement concentration is adjusted to about 5%. . Measurement is performed until the number of measured particles reaches 50,000.
(7) The measurement data is analyzed with the dedicated software attached to the apparatus, and the weight average particle diameter (D4) and the number average particle diameter (D1) are calculated. When the graph / volume% is set with the dedicated software, the “average diameter” on the analysis / volume statistics (arithmetic average) screen is the weight average particle size (D4), and the graph / number% is set with the dedicated software. The “average diameter” on the analysis / number statistic (arithmetic average) screen is the number average particle diameter (D1).

<Calculation method of fine powder amount>
The number-based fine powder amount (number%) in the toner is calculated as follows.

  For example, the number% of particles having a particle size of 4.0 μm or less in the toner is measured by the above-described Multisizer 3 and (1) graph / number% is set with dedicated software, and the measurement result chart is displayed in number%. To do. (2) Check “<” in the particle size setting portion on the format / particle size / particle size statistics screen, and enter “4” in the particle size input section below. Then, (3) when the analysis / count statistics (arithmetic mean) screen is displayed, the numerical value of the “<4 μm” display portion is the number% of particles of 4.0 μm or less in the toner.

<Calculation method of coarse powder amount>
The volume-based coarse powder amount (volume%) in the toner is calculated as follows.

  For example, the volume% of particles of 10.0 μm or more in the toner is measured by the above-mentioned Multisizer 3 and (1) graph / volume% is set with dedicated software and the measurement result chart is displayed as volume%. To do. (2) Check “>” in the particle size setting portion on the format / particle size / particle size statistics screen, and enter “10” in the particle size input section below. (3) When the analysis / volume statistics (arithmetic average) screen is displayed, the numerical value of the “> 10 μm” display portion is the volume% of particles of 10.0 μm or more in the toner.

<Powder X-ray diffraction analysis>
The XRD pattern was measured using an X-ray diffraction analyzer (X'pert PRO-MPD: manufactured by PANalytical).

  X-rays were generated at an acceleration voltage of 45 kV and a current of 40 mA.

The measurement conditions of the powder X-ray are:
Divergent slit: 1/4 rad (fixed)
Anti-scattering slit: 1/2 rad
Solar slit: 0.04 rad
Mask: 15mm
Anti-scatter slit: 7.5mm
Spinner: Yes Measurement method Scan axis: Continuous 2θ / θ
Measurement range: 5.0 ≦ 2θ ≦ 80 °
Step interval: 0.026 deg / s
Scan speed: 0.525 deg / s
The measurement was performed.

As the sample used in measuring the P _70, using the same formulation as the porous ferrite core material, by varying the oxygen concentration in the firing process during manufacturing, the external magnetic field of 5000 / 4π (kA / m) Particles adjusted so that the magnetization intensity when applied is 70 Am ² / kg are used.

<Measurement method of magnetization intensity of carrier core>
The magnetization intensity of the carrier core can be obtained by a vibrating magnetic field measuring device (Vibrating sample magnetometer) or a direct current magnetization characteristic recording device (BH tracer). In Examples described later, the measurement is performed by the following procedure using a vibrating magnetic field type magnetic property measuring apparatus BHV-30 (manufactured by Riken Electronics Co., Ltd.)

  A sample in which a cylindrical plastic container is sufficiently packed with a carrier core is used. The actual mass of the sample filled in the container is measured. Thereafter, the sample in the plastic container is bonded so that the sample is not moved by the instantaneous adhesive.

  Calibration of the external magnetic field axis and the magnetization moment axis at 5000 / 4π (kA / m) is performed using a standard sample.

The strength of magnetization was measured from a loop of magnetization moment to which an external magnetic field of 5000 / 4π (kA / m) was applied at a sweep speed of 5 (min / loop). From these, by dividing by the sample weight, the magnetization strength (Am ² / kg) of the carrier core is obtained.

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

<Example of production of porous magnetic core 1>
Process 1 (weighing / mixing process)
Fe ₂ O ₃ 68.3 mass%
MnCO ₃ 28.5 mass%
Mg (OH) ₂ 2.0 mass%
SrCO ₃ 1.2% by mass

The composition of the ferrite is shown below.
(MnO) _a (MgO) _b (SrO) _c (M1 ₂ O) _d (M2O) _e (Fe ₂ O ₃ ) _f
In the above formula, a = 0.35, b = 0.04, c = 0.01, d = 0, e = 0, and f = 0.60.

  The ferrite raw material was weighed, 20 parts by mass of water was added to 80 parts by mass of the ferrite raw material, and then wet-mixed with a ball mill for 3 hours using zirconia having a diameter (φ) of 10 mm to prepare a slurry. The solid content concentration of the slurry was 80% by mass.

Process 2 (temporary firing process)
The mixed slurry is dried with a spray dryer (Okawara Kako Co., Ltd.) and then calcined in a batch-type electric furnace under a nitrogen atmosphere (oxygen concentration: 1.0% by volume) at a temperature of 1050 ° C. for 3.0 hours. Ferrite was produced.

Process 3 (Crushing process)
After the calcined ferrite was pulverized to about 0.5 mm with a crusher, water was added to prepare a slurry. The solid content concentration of the slurry was 70% by mass. The slurry was pulverized for 3 hours with a wet ball mill using 1/8 inch stainless beads. Further, this slurry was pulverized by a wet bead mill using zirconia having a diameter of 1 mm for 4 hours to obtain a calcined ferrite slurry having a volume-based 50% particle diameter (D50) of 1.3 μm.

Process 4 (granulation process)
After adding 100 parts by weight of the calcined ferrite slurry at a ratio of 1.0 part by weight of ammonium polycarboxylate as a dispersing agent and 1.5 parts by weight of polyvinyl alcohol as a binder, a spray dryer (manufactured by Okawara Chemical Co., Ltd.) Granulated into spherical particles and dried. After adjusting the particle size of the obtained granulated product, it was heated at 700 ° C. for 2 hours using a rotary electric furnace to remove organic substances such as a dispersant and a binder.

Process 5 (firing process)
Under a nitrogen atmosphere (oxygen concentration 0.8% by volume), the time from room temperature to the firing temperature (1100 ° C.) was 2 hours, and the temperature was maintained at 1100 ° C. for 4 hours for firing. Thereafter, the temperature was lowered to 60 ° C. over 8 hours, returned to the atmosphere from the nitrogen atmosphere, and taken out at a temperature of 40 ° C. or lower.

Process 6 (screening process)
After the agglomerated particles are crushed, the coarse particles are removed by sieving with a sieve having a mesh opening of 150 μm, fine particles are removed by air classification, and the low magnetic force is further removed by magnetic separation, so that the porous magnetic core 1 is formed. Obtained. The obtained porous magnetic core 1 was porous and had pores. The production conditions for each step of the obtained porous magnetic core 1 are shown in Table 1, and the physical properties are shown in Table 2.

<Production example of porous magnetic cores 2 to 19>
In the same manner as in the production example of the porous magnetic core 1, porous magnetic cores 2 to 19 were obtained. The conditions of the mixing process in the manufacturing process 1 of the porous magnetic cores 2 to 19 are the same as those of the porous magnetic core 1. In addition, Table 1 shows manufacturing conditions for each step, and Table 2 shows physical property values.

<Example of production of magnetic carriers 1 to 25>
Process 1 (filling process)
100 parts by mass of porous magnetic core particles 1 are put into a stirring vessel of a mixing stirrer (universal stirrer NDMV type manufactured by Dalton), nitrogen is introduced while maintaining the temperature at 60 ° C. and reducing the pressure to 2.3 kPa. The resin solution 1 shown in Table 4 was dropped on the porous magnetic core particles 1. The amount of dripping was adjusted so that the solid content of the resin component was 5.0 parts by mass with respect to 100 parts by mass of the porous magnetic core particles.

  Stirring was continued for 2 hours after completion of the dropping, and then the temperature was raised to 70 ° C., the solvent was removed under reduced pressure, and the resin composition obtained from the resin solution 1 was filled in the particles of the porous magnetic core 1.

  After cooling, the obtained resin-filled magnetic core particles are transferred into a rotatable mixing vessel and transferred to a mixer having a spiral blade (Drum mixer UD-AT type manufactured by Sugiyama Heavy Industries Co., Ltd.) and 2 ° C. under a nitrogen atmosphere. The temperature was increased to a set temperature of the stirrer of 220 ° C. at a rate of temperature increase per minute. Stirring was performed at this temperature for 1.0 hour to cure the resin, and stirring was continued for an additional 1.0 hour while maintaining 200 ° C.

  Thereafter, it was cooled to room temperature, the ferrite particles filled and cured with resin were taken out, and the nonmagnetic material was removed using a magnetic separator. Further, coarse particles were removed with a vibration sieve to obtain resin-filled magnetic particles filled with resin.

Process 2 (resin coating process)
Subsequently, the resin solution 3 shown in Table 4 was added to 100 parts by mass of a porous magnetic core in a planetary motion type mixer (Nauta mixer VN type manufactured by Hosokawa Micron Corporation) maintained at 60 ° C. under reduced pressure (1.5 kPa). In contrast, the resin component was added so as to have a solid content of 2.0 parts by mass. As a method of charging, a 1/3 amount of the resin solution was charged, and solvent removal and coating operation were performed for 20 minutes. Next, a 1/3 amount of the resin solution was added, and the solvent was removed and applied for 20 minutes. Further, a 1/3 amount of the resin solution was added, and the solvent was removed and applied for 20 minutes.

  Thereafter, the magnetic carrier coated with the coating resin composition is transferred to a mixer (drum mixer UD-AT type manufactured by Sugiyama Heavy Industries Co., Ltd.) having spiral blades in a rotatable mixing container. The mixture container was heat-treated at a temperature of 120 ° C. for 2 hours under a nitrogen atmosphere while stirring at 10 rotations per minute. The obtained magnetic carrier 1 was classified by a magnetic classifier after separating a low-magnetic force product by magnetic separation, passing through a sieve having an opening of 150 μm. A magnetic carrier 1 having a volume distribution standard 50% particle size (D50) of 39.1 μm was obtained.

  Table 3 shows physical property values of the obtained magnetic carrier 1.

  However, for the magnetic carriers 10 to 12, the step 2 described above was used for the filling step, and the step 1 described above was used for the resin coating step.

[Production Example of Toner 1]
-Binder resin (polyester resin) 100 parts by mass-C.I. I. Pigment Blue 15: 3 4.5 parts by mass, 1,4-di-t-butylsalicylic acid aluminum compound 0.5 part by mass, normal paraffin wax (melting point: 78 ° C.) 6 parts by mass (FM-75J type, manufactured by Mitsui Mining Co., Ltd.) After mixing well, the feed amount of 10 kg / h was obtained with a twin-screw kneader (PCM-30 type, manufactured by Ikekai Steel Co., Ltd.) set at a temperature of 130 ° C. (Kneaded material temperature at the time of discharge was about 150 ° C.). The obtained kneaded product was cooled, coarsely crushed with a hammer mill, and then finely pulverized with a mechanical pulverizer (T-250: manufactured by Turbo Kogyo Co., Ltd.) at a Feed amount of 15 kg / hr. A particle having a weight average particle size of 5.5 μm, 55.6% by number of particles having a particle size of 4.0 μm or less, and 0.8% by volume of particles having a particle size of 10.0 μm or more is obtained. It was.

  The obtained particles were classified using a rotary classifier (TTSP100, manufactured by Hosokawa Micron Corporation) to cut fine powder and coarse powder. Cyan toner particles 1 having a weight average particle size of 6.4 μm, an abundance of particles having a particle size of 4.0 μm or less, 25.8% by number, and 2.5% by volume of particles having a particle size of 10.0 μm or more Got.

Further, the following materials were put into a Henschel mixer (FM-75 type, manufactured by Nippon Coke Co., Ltd.), the peripheral speed of the rotary blade was set to 35.0 (m / sec), and mixing was performed for 3 minutes. Cyan toner 1 was obtained by attaching silica and titanium oxide to the surfaces of the particles 1.
-Cyan toner particles 1 100 parts by mass-Silica 3.5 parts by mass (Silica fine particles prepared by the sol-gel method were surface-treated with 1.5% by mass of hexamethyldisilazane and then adjusted to a desired particle size distribution by classification) .)
・ 0.5 parts by mass of titanium oxide (surface-treated with an octylsilane compound of metatitanic acid having anatase crystallinity)

  Table 5 shows the formulation and physical property values of the obtained toner.

[Example 1]
9 parts by mass of toner 1 was added to 91 parts by mass of magnetic carrier 1, and shaken with a shaker (YS-8D type: manufactured by Yayoi Co., Ltd.) to prepare 300 g of a two-component developer. The amplitude condition of the shaker was 200 rpm for 2 minutes.

  On the other hand, 90 parts by mass of toner 1 was added to 10 parts by mass of magnetic carrier 1 and mixed for 5 minutes with a V-type mixer in an environment of normal temperature and normal humidity of 23 ° C./50% RH to obtain a replenishment developer. .

  The following evaluation was performed using the two-component developer and the replenishment developer.

  As an image forming apparatus, a Canon color copier imageRUNNER ADVANCE C9075 PRO remodeling machine was used.

  A two-component developer was placed in each color developer, a replenishment developer container containing each color replenishment developer was set, an image was formed, and various evaluations were performed before and after the durability test.

  As a durability test, an FFH output chart with an image ratio of 1% was used in a printing environment at a temperature of 23 ° C./humidity of 5 RH% (hereinafter “N / L”). In a printing environment of a temperature of 30 ° C./humidity of 80 RH% (hereinafter “H / H”), an FFH output chart with an image ratio of 40% was used. FFH is a value representing 256 gradations in hexadecimal, 00h is the first gradation (white background) of 256 gradations, and FFH is the 256th gradation (solid part) of 256 gradations. .

The number of image outputs was changed according to each evaluation item.
conditions:
Paper Laser beam printer paper CS-814 (81.4 g / m ² )
(Canon Marketing Japan Inc.)
Image formation speed A4 size, full color, modified to output at 80 (sheets / min)
It was.
Development conditions The development contrast can be adjusted to an arbitrary value, and automatic correction by the main unit is activated.
It was remodeled so that there was no.
The voltage (Vpp) between the peaks of the alternating electric field has a frequency of 2.0 kHz and Vpp
Modified to change from 0.7kV to 1.8kV in increments of 0.1kV
It was.
Each color was modified to output a single color image.

  Each evaluation item is shown below.

(1) Leakage Evaluation Under an N / L environment, the initial Vpp is fixed at 1.3 kV, and the contrast potential when the density of the cyan single-color solid image becomes 1.50 (reflection density) is set. Pass the paper.

  After passing the paper, a contrast potential is set when the density of the cyan monochrome solid image becomes 1.50 (reflection density) again.

  Using that contrast, an A4 full-size FFH image was output in increments of 0.1 kV from Vpp to 1.0 kV to 1.8 kV, and leakage characteristics were evaluated.

Evaluation criteria were evaluated according to the following criteria based on the value of Vpp at which three or more image defects such as white spots occur on an A4 full-size FFH image.
A: No generation even at 1.8 kV (very good)
B: Generated at 1.6 to 1.8 kV (good)
C: Generated at 1.4 to 1.5 kV (somewhat good)
D: Generated at 1.2 to 1.3 kV (acceptable level in the present invention)
E: Generated at 1.0 to 1.1 kV (impossible level in the present invention)
F: Less than 1.0 kV (impossible level in the present invention)

(2) White spots Initially under N / L environment, and immediately after 2000 continuous sheets of paper, a halftone horizontal band (30H width 10 mm) and a solid black horizontal band (FFH width 10 mm) in the transfer paper transport direction. Output alternating charts. The image is read by a scanner and binarized. A luminance distribution (256 gradations) of a certain line in the conveyance direction of the binarized image was taken. Draw a tangent line to the brightness of the halftone at that time, and the brightness area (area: sum of brightness numbers) that deviates from the tangent at the rear end of the halftone part until it intersects with the solid part brightness. Based on the evaluation. The evaluation was performed with cyan single color.
A: Less than 20 (very good)
B: 20 or more and less than 30 (good)
C: 30 or more and less than 40 (slightly good)
D: 40 or more and less than 50 (Acceptable level in the present invention)
E: 50 or more (impossible level in the present invention)

(3) Anti-Gassiness of Halftone Image After an initial and durable image output evaluation (50,000 sheets) in an H / H environment, one halftone image (30H) was printed with A4. For the image, a digital microscope VHX-500 (lens wide range zoom lens VH-Z100, manufactured by Keyence Corporation) was used, and the area of 1000 dots was measured. The number average (S) of dot areas and the standard deviation (σ) of dot areas were calculated, and the dot reproducibility index was calculated by the following formula. Then, the roughness of the halftone image was evaluated by the dot reproducibility index (I).
Dot reproducibility index (I) = σ / S × 100

As an evaluation standard of the roughness, it was evaluated by the following standard for cyan single color.
A: I is less than 3.0 (very good)
B: I is 3.0 or more and less than 5.0 (good)
C: I is 5.0 or more and less than 6.0: (slightly good)
D: I is 6.0 or more and less than 8.0 (acceptable level in the present invention)
E: I is 8.0 or more (impossible level in the present invention)

(4) Post-endurance developability The post-endurance developability was evaluated by comparing the initial Vpp at 1.3 kV in a N / L environment and the density of a cyan monochrome solid image being 1.50 (reflection density). The last potential was set. After the endurance of 20,000 sheets at that setting, Vpp was 1.3 kV, and a contrast potential at an image density of 1.50 was obtained, and the difference from the initial value was compared.

  The reflection density was measured using a spectral densitometer 500 series (manufactured by X-Rite).

Development criteria A: Difference from initial is less than 40V (very good)
B: Difference from the initial value is 40V or more and less than 60V (good)
C: Difference from the initial value is 60V or more and less than 80V (slightly good)
D: Difference from the initial value is 80 V or more and less than 100 V (acceptable level in the present invention)
E: The difference from the initial value is 100 V or more (impossible level in the present invention)

(5) Carrier adhesion after durability After durability image output evaluation under N / L environment, carrier adhesion was evaluated. A 00H image was output, the power was turned off in the middle of the image output, and sampling was performed with a transparent adhesive tape in close contact with the electrostatic latent image carrier before cleaning. The number of magnetic carrier particles adhering to the electrostatic latent image bearing member in 1 cm × 20 cm was counted, the number of adhering carrier particles per 1 cm ² was calculated, and evaluated according to the following criteria.
A: Less than 0.5 (very good)
B: 0.5 or more and less than 1.0 (good)
C: 1.0 or more and less than 2.0 (slightly good)
D: 2.0 or more and less than 2.5 (carrier adhesion is slightly noticeable)
E: 2.5 or more (impossible level in the present invention)

(6) Gradation change before and after endurance In the initial setting, an image in which each pattern is set to the following density is output immediately after passing 2000 sheets under the N / L environment. A shift in gradation was observed immediately after. The image was judged by measuring each image density with an X-Rite color reflection densitometer (Color reflection densitometer X-Rite 404A).
Pattern 1: 0.10 to 0.13
Pattern 2: 0.25 to 0.28
Pattern 3: 0.45 to 0.48
Pattern 4: 0.65 to 0.68
Pattern 5: 0.85 to 0.88
Pattern 6: 1.05 to 1.08
Pattern 7: 1.25 to 1.28
Pattern 8: 1.45 to 1.48

Judgment criteria are as follows.
A: All pattern images satisfy the above density range (very good).
B: One pattern image is out of the above density range (good).
C: Two pattern images deviate from the above density range (slightly good).
D: Three pattern images deviate from the above density range (acceptable level in the present invention).
E: Four or more pattern images deviate from the above density range (impossible level in the present invention).

(7) Evaluation of scratches on copying machine members In an N / L environment, with an endurance of 50000 sheets, an A4 full-size FFH image is output every 500 sheets, and the copying machine members are generated by scattering of carriers such as white lines and spots. The occurrence of scratches was evaluated.

The evaluation criteria were determined by the number of durable sheets when two or more image defects such as white streaks and spots occurred on every 500 A4 full-size FFH images.
A: Image defect does not occur even after enduring 50000 sheets (very good)
B: Image defect occurs at 40000 sheets or more (good)
C: Image defect occurs at 30000 sheets or more (slightly good)
D: Image defects occur at 20000 sheets or more (acceptable level in the present invention)
E: Image defects occur at less than 20000 sheets (impossible level in the present invention)

(8) Comprehensive judgment The evaluation ranks in the evaluation items (1) to (7) are quantified (A = 5, B = 4, C = 3, D = 2, E = 0), and the total value is based on the following criteria. Judgment was made.

However, only in the leak resistance evaluation of (1), the evaluation rank was set as follows from the magnitude of the image defect. A = 10, B = 7, C = 5, D = 3, E = 1, F = 0
Overall judgment A: 45 or more: Very good.
B: 40 or more and 44 or less: Good.
C: 35 or more and 39 or less: In the present invention, it is an acceptable level as a high-quality copying machine.
D: 30 or more and 34 or less: An image defect is worrisome (difficult to use as a high-quality copying machine).
E: 25 or more and 29 or less: Unusable level in actual use in the present invention.
F: 24 or less: Unacceptable level in the present invention.

  In Example 1, it was a very good result in any evaluation. The evaluation results are shown in Table 6.

[Example 2]
In the same manner as in Example 1, a two-component developer and a replenishment developer were prepared using the magnetic carrier 2 at the same ratio as in Example 1. Evaluation was performed in the same manner as in Example 1 except that the obtained developer was used.

  In Example 2, since the saturation magnetization was low and the specific resistance of the magnetic carrier was high, white spots and carrier adhesion were affected, but the results were generally good. The evaluation results are shown in Table 6.

Example 3
In the same manner as in Example 1, a two-component developer and a replenishment developer were prepared using the magnetic carrier 3 at the same ratio as in Example 1. Evaluation was performed in the same manner as in Example 1 except that the obtained developer was used.

  In Example 3, since the saturation magnetization was high and the specific resistance of the magnetic carrier was low, the anti-rust property was affected, but the results were generally good. The evaluation results are shown in Table 6.

Example 4
In the same manner as in Example 1, a two-component developer and a replenishment developer were prepared using the magnetic carrier 4 at the same ratio as in Example 1. Evaluation was performed in the same manner as in Example 1 except that the obtained developer was used.

  In Example 4, since the pore volume is small and the peak pore diameter is small, a large amount of filling resin and coating resin are present in the magnetic carrier surface layer, and the surface roughness of the magnetic carrier is reduced. There was a tendency to increase the spent, and there was a slight impact on durability, but the results were generally good. The evaluation results are shown in Table 6.

Example 5
In the same manner as in Example 1, a two-component developer and a replenishment developer were prepared using the magnetic carrier 5 at the same ratio as in Example 1. Evaluation was performed in the same manner as in Example 1 except that the obtained developer was used.

  In Example 5, since the pore volume is large and the peak pore diameter is large, there is a concern that the strength of the particles themselves may be reduced. In addition, there is a concern about the deterioration of leakage due to a decrease in the conduction path inside the particles themselves, and some effects were observed on leakage and scratches on the members, but the results were generally good. The evaluation results are shown in Table 6.

Example 6
In the same manner as in Example 1, a two-component developer and a replenishment developer were prepared using the magnetic carrier 6 at the same ratio as in Example 1. Evaluation was performed in the same manner as in Example 1 except that the obtained developer was used.

  In Example 6, since the particle size of the porous magnetic core core material was small, there was an effect on carrier adhesion and the like, but the result was good. The evaluation results are shown in Table 6.

Example 7
In the same manner as in Example 1, a two-component developer and a replenishment developer were prepared using the magnetic carrier 7 at the same ratio as in Example 1. Evaluation was performed in the same manner as in Example 1 except that the obtained developer was used.

  In Example 7, since the particle size of the porous magnetic core core material was large, there was an influence on the roughness resistance and the like, but the results were generally good. The evaluation results are shown in Table 6.

Example 8
Similarly to Example 1, a two-component developer and a replenishment developer were prepared using the magnetic carrier 8 at the same ratio as in Example 1. Evaluation was performed in the same manner as in Example 1 except that the obtained developer was used.

  In Example 8, since the saturation magnetization was high and the amount of the filling resin and coating resin to be used was small, the specific resistance of the magnetic carrier was low. For this reason, there was an influence on the roughness resistance, but the result was generally good. The evaluation results are shown in Table 6.

Example 9
In the same manner as in Example 1, a two-component developer and a replenishment developer were prepared using the magnetic carrier 9 at the same ratio as in Example 1. Evaluation was performed in the same manner as in Example 1 except that the obtained developer was used.

  In Example 9, since the saturation magnetization was low and the amount of filling resin and coating resin used was large, the specific resistance of the magnetic carrier was high. Therefore, white spots and carrier adhesion were affected, but the results were generally good. The evaluation results are shown in Table 6.

Example 10
In the same manner as in Example 1, a two-component developer and a replenishment developer were prepared using the magnetic carrier 10 at the same ratio as in Example 1. Evaluation was performed in the same manner as in Example 1 except that the obtained developer was used.

  In Example 10, an acrylic resin was used as the filling resin and a silicone resin was used as the coating resin. The evaluation results are shown in Table 6.

Example 11
In the same manner as in Example 1, a two-component developer and a replenishment developer were prepared using the magnetic carrier 11 at the same ratio as in Example 1. Evaluation was performed in the same manner as in Example 1 except that the obtained developer was used.

  In Example 11, since the amount of the filling resin and the coating resin to be used is small, the specific resistance of the magnetic carrier is low. For this reason, there was an influence on the roughness resistance, but the result was generally good. The evaluation results are shown in Table 6.

Example 12
In the same manner as in Example 1, a two-component developer and a replenishment developer were prepared using the magnetic carrier 12 at the same ratio as in Example 1. Evaluation was performed in the same manner as in Example 1 except that the obtained developer was used.

  In Example 12, the specific resistance of the magnetic carrier was increased because of the large amount of filler resin and coating resin used. For this reason, white spots and carrier adhesion were affected, but good results were obtained. The evaluation results are shown in Table 6.

Example 13
In the same manner as in Example 1, a two-component developer and a replenishment developer were prepared using the magnetic carrier 13 at the same ratio as in Example 1. Evaluation was performed in the same manner as in Example 1 except that the obtained developer was used.

  In Example 13, since the specific amount of the magnetic carrier became lower because the amount of the filled resin was small, the anti-rust property was affected, but the result was generally good. The evaluation results are shown in Table 6.

Example 14
In the same manner as in Example 1, a two-component developer and a replenishment developer were prepared using the magnetic carrier 14 at the same ratio as in Example 1. Evaluation was performed in the same manner as in Example 1 except that the obtained developer was used.

  In Example 14, since the amount of the filled resin was large and the specific resistance of the magnetic carrier was higher, the white spots were affected, but the results were generally good. The evaluation results are shown in Table 6.

Example 15
In the same manner as in Example 1, a two-component developer and a replenishment developer were prepared using the magnetic carrier 15 at the same ratio as in Example 1. Evaluation was performed in the same manner as in Example 1 except that the obtained developer was used.

  In Example 15, the amount of the coating resin was small, the specific resistance of the magnetic carrier was lower, and the roughness was affected, but the result was generally good. The evaluation results are shown in Table 6.

Example 16
In the same manner as in Example 1, a two-component developer and a replenishing developer were prepared using the magnetic carrier 16 at the same ratio as in Example 1. Evaluation was performed in the same manner as in Example 1 except that the obtained developer was used.

  In Example 16, although the amount of the coating resin was large and the specific resistance of the magnetic carrier became higher and the white spots were affected, the results were generally good. The evaluation results are shown in Table 6.

[Comparative Example 1]
In the same manner as in Example 1, a two-component developer and a replenishment developer were prepared using the magnetic carrier 17 at the same ratio as in Example 1. Evaluation was performed in the same manner as in Example 1 except that the obtained developer was used.

  In the comparative example 1, the magnetic carrier which performed this baking with the rotary electric furnace was used. As a result, even when the saturation magnetization was the same, the peak intensity in the powder X-ray diffraction measurement was low, suggesting a difference in crystal structure, and a large difference in leakage was generated. For this reason, in the second half of the endurance, image defects due to leaks appeared remarkably. The evaluation results are shown in Table 6.

[Comparative Example 2]
Similarly to Example 1, a two-component developer and a replenishment developer were prepared using the magnetic carrier 18 at the same ratio as in Example 1. Evaluation was performed in the same manner as in Example 1 except that the obtained developer was used.

  In Comparative Example 2, a magnetic carrier having a lower saturation magnetization was used. As a result, the specific resistance increased and white spots were affected. Further, since the saturation magnetization is low, the carrier adhesion is also affected, and the image result is of a concern. The evaluation results are shown in Table 6.

[Comparative Example 3]
In the same manner as in Example 1, a two-component developer and a replenishment developer were prepared using the magnetic carrier 19 at the same ratio as in Example 1. Evaluation was performed in the same manner as in Example 1 except that the obtained developer was used.

  In Comparative Example 3, since the saturation magnetization was higher, there were problems such as deterioration of leak and deterioration of roughness due to low specific resistance. The evaluation results are shown in Table 6.

[Comparative Example 4]
Similarly to Example 1, a two-component developer and a replenishment developer were prepared using the magnetic carrier 20 at the same ratio as in Example 1. Evaluation was performed in the same manner as in Example 1 except that the obtained developer was used.

  In Comparative Example 4, since the pore volume is smaller and the peak pore diameter is also smaller, the coating state of the surface layer of the magnetic carrier becomes non-uniform, and the surface roughness is also reduced, which has an effect on durability, and is particularly rugged. As a result, the image was badly affected by the deterioration. The evaluation results are shown in Table 6.

[Comparative Example 5]
In the same manner as in Example 1, a two-component developer and a replenishment developer were prepared using the magnetic carrier 21 at the same ratio as in Example 1. Evaluation was performed in the same manner as in Example 1 except that the obtained developer was used.

  In Comparative Example 5, since the pore volume was larger and the peak pore diameter was larger, the particle strength was weak, and the image defect due to the member scratch was conspicuous. In addition, image deterioration due to deterioration in leakage was also observed due to the fact that there was little conduction inside the particles. The evaluation results are shown in Table 6.

[Comparative Example 6]
In the same manner as in Example 1, a two-component developer and a replenishment developer were prepared using the magnetic carrier 22 at the same ratio as in Example 1. Evaluation was performed in the same manner as in Example 1 except that the obtained developer was used.

  In Comparative Example 6, since the pore volume is small and the peak pore diameter is also small, the coating state of the surface layer of the magnetic carrier becomes non-uniform, and the surface roughness is also small, which has an effect on durability, and is particularly rugged. As a result, the image was badly affected by the deterioration. The evaluation results are shown in Table 6.

[Comparative Example 7]
Similarly to Example 1, a two-component developer and a replenishment developer were prepared using the magnetic carrier 23 at the same ratio as in Example 1. Evaluation was performed in the same manner as in Example 1 except that the obtained developer was used.

  In Comparative Example 7, since the pore volume was large and the peak pore diameter was larger, the particle strength was weak, and the image defect due to the scratch on the member was conspicuous. In addition, image deterioration due to deterioration in leakage was also observed due to the fact that there was little conduction inside the particles. The evaluation results are shown in Table 6.

[Comparative Example 8]
In the same manner as in Example 1, a two-component developer and a replenishment developer were prepared using the magnetic carrier 24 at the same ratio as in Example 1. Evaluation was performed in the same manner as in Example 1 except that the obtained developer was used.

  In Comparative Example 8, since the particle diameter of the porous ferrite core material was smaller, the carrier adhesion was deteriorated and the particle strength was also lowered, so that an image defect was observed. The evaluation results are shown in Table 6.

[Comparative Example 9]
In the same manner as in Example 1, a two-component developer and a replenishment developer were prepared using the magnetic carrier 25 at the same ratio as in Example 1. Evaluation was performed in the same manner as in Example 1 except that the obtained developer was used.

  In Comparative Example 9, since the particle diameter of the porous ferrite core material was very large, the charge imparting ability was lowered, the deterioration of the roughness was prominent, and image defects were caused. The evaluation results are shown in Table 6.

  1, 1K, 1Y, 1C, 1M: electrostatic latent image carrier, 2, 2K, 2Y, 2C, 2M: charger, 3, 3K, 3Y, 3C, 3M: exposure unit, 4, 4K, 4Y, 4C 4M: developing device, 5: developing container, 6, 6K, 6Y, 6C, 6M: developer carrier, 7: magnet, 8: regulating member, 9: intermediate transfer member, 10K, 10Y, 10C, 10M: intermediate Transfer charger, 11: Transfer charger, 12: Recording medium (transfer material), 13: Fixing device, 14: Intermediate transfer body cleaner, 15, 15K, 15Y, 15C, 15M: Cleaner, 16: Pre-exposure, 17: Cylindrical container, 18: lower electrode, 19: support pedestal, 20: upper electrode, 21: magnetic carrier, 22: electrometer, 23: processing computer, d1: gap when no sample is present, d2: when sample is filled Gap

Claims (8)

In the magnetic carrier in which the surface layer of the porous ferrite core material is coated with resin,
The porous ferrite core material is
i) The magnetization intensity (σn) when an external magnetic field of 5000 / 4π (kA / m) is applied is 55 Am ² / kg or more and 70 Am ² / kg or less,
ii) The pore volume is 60 mm ³ / g or more and 120 mm ³ / g or less,
iii) The peak pore diameter is 0.40 μm or more and 0.90 μm or less,
iv) Volume distribution standard 50% particle size (D50) is 25 μm or more and 60 μm or less,
In a powder X-ray diffraction measurement, the maximum peak intensity at 20 deg ≦ 2θ ≦ 40 deg satisfies the relationship of Formula 1.
1.00 ≧ P _n / P ₇₀ ≧ (2σn−65) / 75 (Formula 1)
[Where:
P _n is the maximum peak value of the X-ray diffraction of the porous ferrite core material,
P ₇₀ has the same formulation as the porous ferrite core material, and the X-ray diffraction of particles having a magnetization intensity of 70 Am ² / kg when an external magnetic field of 5000 / 4π (kA / m) is applied. Maximum peak value. ] 2. The magnetic carrier according to claim 1, wherein a specific resistance of the magnetic carrier is 2.0 × 10 ⁶ Ω · cm or more and 1.0 × 10 ⁹ Ω · cm or less at an electric field strength of 2000 V / cm. .   3. The magnetic carrier according to claim 1, wherein a silicone resin or an acrylic resin of 3.0 parts by mass or more and 7.0 parts by mass or less is filled with respect to 100 parts by mass of the porous ferrite core material. .   The silicone resin or acrylic resin of 1.0 to 3.0 parts by mass is coated on 100 parts by mass of the porous ferrite core material. The magnetic carrier according to 1.   5. A two-component developer containing a toner containing a binder resin, a colorant and a release agent, and a magnetic carrier, wherein the magnetic carrier is the magnetic material according to claim 1. A two-component developer characterized by being a carrier. In response to a decrease in the toner concentration of the two-component developer in the developing device, a replenishment developer is supplied to the developing device, and the electrostatic latent image formed on the surface of the electrostatic latent image carrier is converted into the two-component developer in the developing device. A developer for replenishment for use in a two-component development method in which development is performed using a system developer and excess magnetic carrier inside the developer is discharged from the developer as necessary.
The replenishment developer includes a replenishment magnetic carrier and a toner containing a binder resin, a colorant, and a release agent, and a toner amount with respect to 1 part by mass of the replenishment magnetic carrier is 2 parts by mass or more and 50 parts by mass. And
The replenishment developer, wherein the replenishment magnetic carrier is the magnetic carrier according to any one of claims 1 to 4. A charging step for charging the electrostatic latent image carrier, an electrostatic latent image forming step for forming an electrostatic latent image on the surface of the electrostatic latent image carrier, and a two-component developer in the developing device. A developing process for forming a toner image, a transfer process for transferring the toner image to a transfer material with or without an intermediate transfer member, and a fixing process for fixing the transferred toner image to the transfer material. An image forming method comprising:
6. The image forming method according to claim 5, wherein the two-component developer according to claim 5 is used as the two-component developer. An image in which a developer for replenishment is replenished to the developer as the toner concentration of the two-component developer in the developer decreases, and excess magnetic carrier in the developer is discharged from the developer as necessary. Forming method,
The replenishment developer contains a replenishment magnetic carrier and a toner containing a binder resin, a colorant, and a release agent, and a toner amount with respect to 1 part by mass of the replenishment magnetic carrier is 2 parts by mass or more and 50 parts by mass. And
The image forming method according to claim 7, wherein the magnetic carrier for supply is the magnetic carrier according to claim 1.

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