JP2019028299A - Magnetic carrier, two-component developer, developer for replenishment, and image forming method - Google Patents

Abstract

To provide a magnetic carrier which is excellent in stability of image density and thin line reproducibility even after having been left under high humidity environment.SOLUTION: A magnetic carrier has a resin-filled magnetic core particle having a porous magnetic core and a filling resin present in pores of the porous magnetic core, and a resin-coated layer thereon, where in pore size distribution of the porous magnetic core, a peak pore size in a range of 0.1-3.0 μm is 0.20-0.70 μm and a pore size is 20-57 mm/g, when in specific regions R1 and R2, ratios of compositions derived from a resin component on a mass basis are represented by JR1 and JR2, ratios of compositions derived from the porous magnetic core on a mass basis are represented by FR1 and FR2, JR1/FR1 is represented by MR1 and JR2/FR2 is represented by MR2, the magnetic carrier satisfies 0.20≤MR2/MR1≤0.90.SELECTED DRAWING: Figure 1

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 common. In this development, there are a wide variety of two-component development systems in which carrier particles called magnetic carriers are mixed with toner, tribo-charged, impart an appropriate amount of positive or negative charge to the toner, and the charge is 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 in long-term use and to reduce color fluctuations in the case of full color (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 to 8).

JP-A-4-93954 JP 2012-173375 A JP 2006-337579 A JP 2009-175666 A JP 2011-158830 A Japanese Patent No. 4898959 Japanese Patent Laying-Open No. 2015-007758 Japanese Patent No. 6031708

With the magnetic carriers of Patent Documents 2 to 8, problems such as the lifetime of the developer, white spots and roughness are improved.
On the other hand, from the viewpoint of low-temperature fixability of the toner, techniques such as addition of crystalline polyester in the toner, or addition of a large amount of low-resistance external additive from the viewpoint of fluidity and charge control are becoming mainstream. As a result, image density, fine line reproducibility, and the like have been attracting attention as new issues, particularly after being left in a high humidity environment.
Therefore, there is an urgent need to develop a magnetic carrier, a two-component developer, and an image forming method using the same that satisfy the above-mentioned problems.
An object of the present invention is to provide a magnetic carrier that solves the above problems, and provides a magnetic carrier that is excellent in image density stability and fine line reproducibility even after being left in a high humidity environment. There is to do. Also provided are a two-component developer, a replenishment developer, and an image forming method using the magnetic carrier.

The present inventors use a porous magnetic core, and by using a magnetic carrier that defines a composition derived from a resin having a cross section as shown below and an abundance ratio derived from the porous magnetic core, in a high humidity environment. It has been found that a magnetic carrier having excellent image density stability and fine line reproducibility can be obtained even after being left.
That is, the present invention relates to a resin-filled magnetic core particle having a porous magnetic core and a filling resin present in the pores of the porous magnetic core, and a resin present on the surface of the resin-filled magnetic core particle. A magnetic carrier having a coating layer,
In the pore size distribution of the porous magnetic core,
The peak pore diameter that maximizes the differential pore volume in the range of 0.1 μm or more and 3.0 μm or less is 0.20 μm or more and 0.70 μm or less,
The pore volume, which is the integral value of the differential pore volume in the range of 0.1 μm or more and 3.0 μm or less, is 20 mm ³ / g or more and 57 mm ³ / g or less,
The magnetic carrier is in the region R1 and the region R2 defined as follows:
The mass-based proportions of the resin component-derived composition are JR1 and JR2, respectively, and the mass-based proportions of the composition derived from the porous magnetic core are FR1 and FR2, respectively.
Furthermore, when JR1 / FR1 is MR1 and JR2 / FR2 is MR2, MR1 and MR2 are
0.20 ≦ MR2 / MR1 ≦ 0.90
A magnetic carrier characterized by satisfying the relationship:
(Region R1 is a cross-sectional image of the magnetic carrier. Let straight lines be straight lines A and B;
A straight line passing through the intersection of the line segment and the contour line of the resin-filled magnetic core particle and orthogonal to the line segment is defined as a straight line C.
When a straight line that is parallel to the straight line C and is 5.0 μm away from the straight line C toward the center of the magnetic carrier is defined as a straight line D,
It is a region surrounded by the contour line of the resin-filled magnetic core particles and the straight lines A, B and D and in contact with the straight line C.
The region R2 is a region surrounded by the straight lines A, B, and D and a straight line E that is parallel to the straight line D and is 5.0 μm away from the straight line D toward the center of the magnetic carrier. )
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 in which the magnetic carrier is the magnetic carrier.
Further, the present invention provides a charging step for charging the electrostatic latent image carrier,
An electrostatic latent image forming step of forming an electrostatic latent image on the surface of the electrostatic latent image carrier;
Developing the electrostatic latent image with a two-component developer to form a toner image;
An image forming method comprising a transfer step of transferring the toner image to a transfer material with or without an intermediate transfer member, and a fixing step of fixing the transferred toner image to the transfer material,
The present invention relates to an image forming method in which the two-component developer is the two-component developer.
The present invention is also an image forming method in which 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,
The replenishment developer contains a magnetic carrier and a toner containing a binder resin, a colorant and a release agent,
The replenishment developer contains 2 parts by weight or more and 50 parts by weight or less of the toner with respect to 1 part by weight of the magnetic carrier.
The magnetic carrier relates to an image forming method which is the magnetic carrier.
The present invention also provides a replenishment developer for use in the image forming method.

  By using the magnetic carrier of the present invention, the image density is stable and excellent fine line reproducibility can be maintained even after being left in a high humidity environment.

Explanatory drawing of area | region R1 and R2 which concern on the magnetic carrier of this invention Schematic diagram of image forming apparatus Schematic diagram of image forming apparatus Schematic of coating resin content regulation method in GPC molecular weight distribution curve Schematic of coating resin content regulation method in GPC molecular weight distribution curve Schematic of measuring device for specific resistance of magnetic carrier used in the present invention Schematic of current carrier current measurement device used in the present invention Schematic diagram of image for scattering evaluation

In the present invention, the description of “XX or more and XX or less” or “XX to XX” representing a numerical range means a numerical range including a lower limit and an upper limit as endpoints unless otherwise specified.
The magnetic carrier of the present invention is a magnetic carrier using a porous magnetic core, and the mass-based ratios of the composition derived from the resin component in the regions R1 and R2 defined as follows are JR1 and JR2, respectively. The mass-based ratio of the composition derived from the magnetic core is FR1 and FR2, respectively, and the ratio of the ratio of the composition derived from the resin component to the ratio of the composition derived from the porous magnetic core is MR1 and JR2 / FR2 is MR2. When MR1 and MR2 are
0.20 ≦ MR2 / MR1 ≦ 0.90
It is a feature.

Here, the definition of the region R1 will be described with reference to FIG. In the cross-sectional image of the magnetic carrier, A and B are two straight lines that are parallel to the maximum line length of the resin-filled magnetic core particles and are separated from the line segment by 2.5 μm. A straight line C that passes through the intersection of the line segment and the contour line of the resin-filled magnetic core particle, is orthogonal to the line segment, is parallel to the straight line C, and is 5.0 μm from the straight line C toward the center of the magnetic carrier. Assume a straight line D away.
A region surrounded by the contour line of the resin-filled magnetic core particles between the straight lines A and B and the straight lines A, B, and D and in contact with the straight line C is defined as R1.
The region R2 is a region surrounded by straight lines A, B, and D and a straight line E that is parallel to the straight line D and is 5.0 μm away from the straight line D toward the center direction of the magnetic carrier.
This indicates that the resin ratio in the vicinity of the surface layer of the resin-filled magnetic core particles is higher than the internal resin ratio. With this configuration, charge relaxation properties and stabilization of the coating layer can be achieved.
In the present invention, the ratio (MR1) between the ratio of the resin-derived composition in the vicinity of the surface layer of the resin-filled magnetic core particles and the ratio of the composition derived from the porous magnetic core is such that the ratio of the resin-derived composition in the inner portion and the porosity It is characterized by being larger than the ratio (MR2) to the ratio of the composition derived from the magnetic core. That is, it shows that the resin component of the surface layer is more than the inner part.

In the examination so far, the coexistence of the suppression of “gasiness” and “white spot” has been greatly improved by making the resin abundance ratio in the vicinity of the carrier surface layer and its inner part into a specific relationship. However, energy savings and high-definition images are progressing, and new challenges are faced in technological developments such as the addition of crystalline polyester in toners or the addition of large amounts of low-resistance external additives.
This is a decrease in the charge maintaining ability of the developer, and is a problem that appears prominently in a high humidity environment. It has been found that when the resin-filled magnetic core material with unevenness is coated with resin, the film thickness of the coating resin is unevenly slightly following the unevenness of the core material. As a result of intensive studies, the present invention has been achieved.

The reason why the film thickness unevenness can be reduced by setting MR2 / MR1 in the above range is considered as follows. That MR2 / MR1 is in the above range indicates that there is a certain amount of filled resin in the surface layer of the magnetic carrier particles. For this reason, it is considered that even when the coating resin penetrates from the surface layer of the magnetic core particles into the recesses when coating with the coating resin, the coating resin can be uniformly coated without unevenness of the coating resin film thickness.
By setting MR2 / MR1 within the above range, it is possible to reduce density change due to charge leakage and to improve fine line reproducibility without deteriorating “gasiness” and “white spot”.
When MR2 / MR1 is less than 0.20, the charge relaxation property is small, so that the density change in both high and low humidity environments is large, and the fine line reproducibility is lowered. When MR2 / MR1 exceeds 0.90, the charge relaxation property becomes too large, a concentration change due to charge leakage in a high humidity environment occurs, and the fine line reproducibility is lowered. MR2 / MR1 can be controlled by the amount of resin to be filled and the viscosity. The control method will also be described in the magnetic carrier manufacturing method described later. MR2 / MR1 preferably satisfies 0.25 ≦ MR2 / MR1 ≦ 0.85, and more preferably satisfies 0.30 ≦ MR2 / MR1 ≦ 0.75.
The present invention is a magnetic carrier having resin-filled magnetic core particles containing a filled resin in pores of a porous magnetic core and a resin coating layer present on the surface of the resin-filled magnetic core particles. Thereby, the charge relaxation property of the magnetic carrier can be controlled, and the density stability and fine line reproducibility of the image are improved.

In the pore diameter distribution of the porous magnetic core, the pore volume, which is an integral value of the differential pore volume in the range of 0.1 μm or more and 3.0 μm or less, may be 20 mm ³ / g or more and 57 mm ³ / g or less. is necessary. When the pore volume is less than 20 mm ³ / g, the density change in both high and low humidity occurs, which is considered to be the effect of damage to the toner due to the increase in specific gravity, resulting in a decrease in fine line reproducibility. There is. The pore volume is preferably 25 mm ³ / g or more and 55 mm ³ / g or less. The pore volume can be controlled by the firing temperature of the porous magnetic core and the firing time. For example, the pore volume can be reduced by increasing the firing temperature.

The porous magnetic core used in the present invention is required to have a peak pore diameter in the range of 0.1 μm or more and 3.0 μm or less in the pore diameter distribution of 0.20 μm or more and 0.70 μm or less. When the pore diameter is less than 0.20 μm, charge relaxation becomes too large, concentration change due to charge leakage in a high humidity environment may occur, and fine line reproducibility may deteriorate. On the other hand, when the thickness exceeds 0.70 μm, since the charge relaxation property is small, the density change occurs in both high and low humidity environments, and the fine line reproducibility tends to be lowered.
The peak pore diameter is preferably 0.25 μm or more and 0.65 μm or less. The peak pore diameter can be controlled by the particle size of the calcined ferrite finely pulverized product, the firing temperature of the porous magnetic core, and the firing time. For example, the peak pore diameter can be reduced by reducing the particle size of the finely pulverized calcined ferrite product.

The content of the resin filled in the magnetic carrier is preferably 1.0 part by mass or more and 6.0 parts by mass or less, and 2.0 parts by mass or more and 5.0 parts by mass or less with respect to 100 parts by mass of the porous magnetic core. More preferably.
When the amount of the filled resin is 1.0 part by mass or more, it is possible to suppress the occurrence of concentration change due to charge leakage in a high-humidity environment and the reduction in fine line reproducibility. On the other hand, when the amount of the filled resin is 6.0 parts by mass or less, the charge relaxation property is good, and it is possible to suppress the occurrence of density change in both high and low humidity environments and the reduction in fine line reproducibility.

The content of the coating resin forming the resin coating layer is preferably 0.5 parts by mass or more and 3.0 parts by mass or less, based on 100 parts by mass of the resin-filled magnetic core particles, and 0.8 parts by mass or more and 2. More preferably, it is 7 parts by mass or less.
When the amount of the coating resin is 0.5 parts by mass or more, it is possible to suppress the occurrence of concentration change due to charge leakage in a high-humidity environment and the reduction in fine line reproducibility. On the other hand, when the amount of the coating resin is 3.0 parts by mass or less, the charge relaxation property is good, and it is possible to suppress the occurrence of concentration change in both high and low humidity environments and the reduction in fine line reproducibility.

  The current value when applying 500 V of the magnetic carrier is preferably 10.0 μA or more and 100.0 μA or less, and more preferably 13.0 μA or more and 95.0 μA or less. When it is 10.0 μA or more, it is possible to suppress the occurrence of concentration changes in both high and low humidity environments and the reduction in fine line reproducibility. On the other hand, when it is 50.0 μA or less, it is possible to suppress the occurrence of concentration change due to charge leakage in a high-humidity environment and the reduction in fine line reproducibility. The current value correlates with the cross-sectional ratio, the total resin amount in the carrier, and the carrier resistance, and can be controlled by the magnetization amount of the porous magnetic core and the content of the filling resin and the coating resin. For example, the current value can be reduced by increasing the content of the coating resin.

The specific resistance value of the magnetic carrier at an electric field strength of 2000 V / cm is preferably 1.0 × 10 ⁶ Ω · cm or more and 1.0 × 10 ¹⁰ Ω · cm or less, and 2.1 × 10 ⁶ Ω · cm or more. It is more preferable that it is 2.1 × 10 ⁹ Ω · cm or less. Thereby, good density stability can be obtained. The specific resistance value can be controlled by the amount of magnetization of the porous magnetic core and the content of the filling resin or coating resin. For example, the specific resistance value can be increased by increasing the content of the coating resin.

When the specific resistance value of the porous magnetic core at an electric field strength of 300 V / cm is 5.0 × 10 ⁵ Ω · cm or more and 8.0 × 10 ⁹ Ω · cm or less, good concentration stability can be obtained. Therefore, it is preferable.

Next, the manufacturing method of the magnetic carrier of this invention is demonstrated.
(Method for producing porous magnetic core)
The porous magnetic core can be manufactured by the following process.
As the material of the porous magnetic core, magnetite or ferrite is preferable. Furthermore, the material of the porous magnetic core is more preferably ferrite, since the porous structure of the porous magnetic core 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, respectively, and z is 0.2 <z <1.0.)

In the formula, it is preferable to use one or more metal atoms selected from the group consisting of Li, Fe, Mn, Mg, Sr, Cu, Zn, and Ca as M1 and M2.
The magnetic carrier is required to have an uneven state on the surface of the porous magnetic core in order to maintain an appropriate amount of magnetization and make the pore diameter in a desired range. 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. From the above viewpoint, Mn-based ferrite, Mn-Mg-based ferrite, Mn-Mg-Sr-based ferrite and Li-Mn-based ferrite containing Mn element are more preferable.
Below, the example of the manufacturing process in the case of using a ferrite as a porous magnetic core is demonstrated.

-Process 1 (weighing / mixing process):
The ferrite raw materials are weighed and mixed. Examples of the ferrite raw material include the following. Metal particles such as Li, Fe, Mn, Mg, Sr, Cu, Zn, Ca, and their oxides, hydroxides, carbonates, oxalates, and the like.
Examples of the mixing apparatus include the following. The pore volume tends to be larger when a hydroxide or carbonate is used as a raw material species to be blended than when an oxide is used. 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 preferably for 0.1 hour or more and 20.0 hours or less.

-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 2.5 hours or more and 5.0 hours or less in a temperature range of 1050 ° C. to 1100 ° C., and the raw material is made into ferrite. At this time, the charging amount is appropriately adjusted so that the ferritization reaction proceeds sufficiently. Further, it is preferable to lower the oxygen concentration such as in an atmosphere adjustment, particularly in a nitrogen atmosphere, because the ferritization reaction is more likely to proceed. 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.

-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. However, since the calcined product manufactured by the above method is a calcined product in which a part of the ferritization reaction has proceeded with respect to the conventional calcined product, the hardness is high. Therefore, in order to obtain a desired particle size, it is preferable to increase the crushing strength. It is preferable to increase the pulverization strength, to reduce the particle size of the finely pulverized product of calcined ferrite, and to control the particle size distribution.

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 can be mentioned.
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.
It is more preferable to adjust the particle size of the calcined product having high hardness by first performing coarse pulverization by dry method and then finely pulverizing by wet method.

-Process 4 (granulation process):
For example, a dispersant, water, a binder and, if necessary, a pore adjusting agent are added to the finely pulverized product of calcined ferrite. 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, preferably 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, preferably at a temperature of 600 ° C. or higher and 800 ° C. or lower. In particular, it is preferable to set the combustion removal temperature to 700 ° C. or higher because the pore diameter of the porous magnetic core can be easily adjusted to a specific range.

-Process 5 (main baking process):
Thereafter, firing is performed in an electric furnace in which the oxygen concentration can be controlled in an atmosphere in which the oxygen concentration is controlled, preferably at a temperature of 1000 ° C. to 1300 ° C. for 1 hour to 24 hours. By controlling the temperature, the pore volume can be controlled. For example, by increasing the temperature, the pore volume decreases. Incidentally, the pore volume of the porous magnetic core, 20.0 mm ³ / g or more 57.0mm and a ³ / g and preferably at most 25.0 mm ³ / g or more 55.0 mm ³ / g.

-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. For the oxide film treatment, a general rotary electric furnace, batch electric furnace or the like can be used, and for example, heat treatment can be performed at 300 ° C. or higher and 700 ° C. or lower.
The volume distribution reference 50% particle size (D50) of the porous magnetic core obtained as described above is preferably 28.0 μm or more and 78.0 μm or less.

(Method for producing resin-filled magnetic core particles)
A preferred method for filling the pores of the porous magnetic core with the filling resin is to add the filling resin to the pores of the porous magnetic core. The filling resin is preferably a thermosetting resin that does not elute even when a solvent is used during coating of the coating resin. More preferably, it is a silicone resin that can be filled without diluting in a solvent. Thereby, there is no shrinkage | contraction of the resin component during solvent removal, and it becomes easy to adjust MR2 / MR1 to a desired range.
As the silicone resin, a silicone oligomer such as a methyl silicone oligomer or a methyl phenyl silicone oligomer, a methyl silicone resin, or the like can be used.
Examples of the method of filling the pores of the porous magnetic core with the resin include a method of impregnating the porous magnetic core into the resin solution by a coating method such as a dipping method, a spray method, a brush coating method, and a fluidized bed. .

A method of filling the pores of the porous magnetic core with a filled resin composition containing the filled resin at normal pressure and curing by heating is preferable.
Moreover, as a resin composition before hardening, a highly impregnated thing is preferable. By using a resin composition having high impregnation properties, MR2 / MR1 can be easily adjusted, and stability is improved. Examples of the impregnation index include kinematic viscosity of the resin composition itself. Preferably the kinematic viscosity is comparatively small resin composition, for example, not more than 0.5 mm ² / s or more 200.0mm ² / s, preferably in order to adjust the MR2 / MR1 in the above range.

After filling the filled resin composition, it is heated by various methods as necessary, and the filled filled resin composition is brought into close contact with the porous magnetic core. The heating method may be either an external heating method or an internal heating method, and may be, for example, a fixed or fluid electric furnace, a rotary electric furnace, a burner furnace, or a microwave baking.
The amount of the filled resin is preferably 1.0 part by mass or more and 6.0 parts by mass with respect to the porous magnetic core from the viewpoint of improving the coating property of the coating resin composition and maintaining the charge.

Moreover, it is preferable that the filling resin composition contains a silane coupling agent. The silane coupling agent has good compatibility with the filling resin, and the wettability and adhesion between the porous magnetic core and the filling resin are further increased. Therefore, the filling resin is filled from the pores inside the porous magnetic core. 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.
For example, the filled resin composition preferably contains a silicone oligomer and a silane coupling agent. Further, it preferably contains a solvent such as methyl silicone resin and toluene, and a silane coupling agent. The filled resin is preferably a thermoset of these filled resin compositions.

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 and the filling resin and improves the affinity with the coating resin composition is considered as follows.
An 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 to improve wettability and adhesion, and the functional group having an amino group is oriented on the filling resin side, thereby covering the resin. It is thought that the affinity with the composition is also increased.
It is preferable that the quantity of the silane coupling agent to add is 1.0-20.0 mass parts with respect to 100 mass parts of filling resin. More preferably, it is 5.0-10.0 mass parts. The above range is preferable from the viewpoint of improving the wettability and adhesion between the porous magnetic core and the filling resin.

(Method for manufacturing magnetic carrier)
The method of coating the surface of the resin-filled magnetic core particles with the resin coating layer is not particularly limited. Examples of the coating resin composition include a method of treating the surface of the resin-filled magnetic core particles by a coating method such as a dipping method, a spray method, a brush coating method, a dry method, and a fluidized bed.
As the coating resin for forming the resin coating layer, 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. More preferred are (meth) acrylic acid ester having an alicyclic hydrocarbon group, and a monomer and copolymer containing a macromonomer (hereinafter referred to as coating resin A). The coating resin A is a (meth) acrylic acid ester having an alicyclic hydrocarbon group, other (meth) acrylic monomers other than the (meth) acrylic acid ester having the alicyclic hydrocarbon group, and More preferably, it is a macromonomer copolymer.
The coating resin A smoothes the coating surface of the resin layer coated on the surface of the ferrite-based core material. As a result, the toner-derived component is prevented from adhering to the magnetic carrier and has a function of suppressing a decrease in charging ability. It functions to suppress adhesion of toner-derived components to the magnetic carrier and to suppress a decrease in charging ability. In addition, the macromonomer improves the adhesion with the resin-filled magnetic core particles, and the image density stability is improved. Furthermore, in the present invention, charge leakage in the coat thin layer portion can be reduced in a high-humidity environment for a long period of time, and the density and fine line reproducibility after standing can be stabilized.

Examples of the (meth) acrylic acid ester (monomer) having an alicyclic hydrocarbon group include cyclobutyl acrylate, cyclopentyl acrylate, cyclohexyl acrylate, cycloheptyl acrylate, dicyclopentenyl acrylate, and diacrylate acrylate. Examples include cyclopentanyl, cyclobutyl methacrylate, cyclopentyl methacrylate, cyclohexyl methacrylate, cycloheptyl methacrylate, dicyclopentenyl methacrylate, and dicyclopentanyl methacrylate. These may be used alone or in combination of two or more.
The amount of the (meth) acrylic acid ester monomer having an alicyclic hydrocarbon group is preferably 34.0% by mass or more and 95.0% by mass or less based on the total monomers of the coating resin A, and more Preferably they are 40.0 mass% or more and 90.0 mass% or less.

The macromonomer is not particularly limited, but is selected from the group consisting of methyl acrylate, methyl methacrylate, butyl acrylate, butyl methacrylate, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, styrene, acrylonitrile and methacrylonitrile. Preferably, the polymer is at least one monomer.
The amount of the macromonomer used is preferably 10 to 50% by mass, more preferably 15 to 40% by mass, based on the total monomers of the coating resin A.
The weight average molecular weight Mw of the macromonomer is preferably 2000 or more and 10,000 or less, more preferably 2500 or more and 8000 or less.

  The weight average molecular weight (Mw) of the coating resin A is preferably 20,000 or more and 120,000 or less, more preferably 30,000 or more and 100,000 or less, from the viewpoint of coating stability.

Examples of other (meth) acrylic monomers other than the (meth) acrylic acid ester having an alicyclic hydrocarbon group include the following.
For example, methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, butyl acrylate (n-butyl, sec-butyl, iso-butyl or tert-butyl; the same applies hereinafter), butyl methacrylate, 2-acrylic acid 2- Ethylhexyl, 2-ethylhexyl methacrylate, acrylic acid or methacrylic acid.

The case where two or more types of resin compositions are used for the resin coating layer will be described.
In the present invention, it is more preferable to blend the coating resin A and a resin having a specific acid value (hereinafter referred to as coating resin B) than to use the coating resin A alone. The coating resin B is preferably a polymer of monomers containing at least the other (meth) acrylic monomers.
As a result, it is possible to achieve both reduction of the charge leaking portion and improvement of the coating strength of the resin coating layer, and it is possible to output a stable image for a longer period of time, and the stability after being left is improved.
When the coating resin A and the coating resin B are used for the resin coating layer, the mass ratio (A: B) is preferably 9: 1 to 1: 9.
The oxidation of the resin coating layer is preferably 0.1 mgKOH / g or more and 10 mgKOH / g or less.

  The acid value of the coating resin A is preferably 0.0 mgKOH / g or more and 3.0 mgKOH / g or less, and more preferably 0 mgKOH / g or more and 2.5 mgKOH / g or less.

Further, the acid value of the coating resin B is preferably 3.5 mgKOH / g or more and 50.0 mgKOH / g or less, and more preferably 4.0 mgKOH / g or more and 50.0 mgKOH / g or less.
The weight average molecular weight (Mw) of the coating resin B is preferably 30,000 or more and 120,000 or less, more preferably 40,000 or more and 100,000 or less from the viewpoint of coating stability.

  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.

Next, a preferable toner configuration will be described in detail below.
The toner preferably contains a binder resin, a colorant, and a release agent. Examples of the binder resin include vinyl resin, polyester resin, and epoxy resin. Of these, vinyl resins and polyester resins are more preferred in terms of chargeability and fixability. A polyester resin is particularly preferable.
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, etc. If necessary, it can be mixed with the above-described binder resin.

As the binder resin, the following polyester resins are also preferable.
A polyester resin having an acid value of 90 mgKOH / g or less and an OH value of 50 mgKOH / g or less is preferable. 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 ° C. or higher and 75 ° C. or lower. The number average molecular weight (Mn) is preferably 1,500 or more and 50,000 or less. The weight average molecular weight (Mw) is preferably 6,000 to 100,000, more preferably 10,000 to 90,000.

For the purpose of promoting the plastic effect of the toner and improving the low-temperature fixability, the following crystalline polyester resin may be added to the toner.
Examples of the crystalline polyester include a polycondensate of a monomer composition containing, as main components, an aliphatic diol having 2 to 22 carbon atoms and an aliphatic dicarboxylic acid having 2 to 22 carbon atoms.
The aliphatic diol having 2 to 22 carbon atoms (more preferably 6 to 12 carbon atoms) is not particularly limited, but is preferably a chain (more preferably linear) aliphatic diol. Of these, linear aliphatic groups such as ethylene glycol, diethylene glycol, 1,4-butanediol, and 1,6-hexanediol, and α, ω-diol are particularly preferred.
Of the alcohol components, preferably 50 mass% or more, more preferably 70 mass% or more is an alcohol selected from aliphatic diols having 2 to 22 carbon atoms.

On the other hand, the aliphatic dicarboxylic acid having 2 to 22 carbon atoms (more preferably 6 to 12 carbon atoms) is not particularly limited, but is a chain (more preferably linear) aliphatic dicarboxylic acid. Is preferred.
The amount of the crystalline polyester used is preferably 0.1 parts by mass or more and 30 parts by mass or less, more preferably 0.5 parts by mass or more and 20 parts by mass or less, more preferably 100 parts by mass of the binder resin. Is 3 parts by mass or more and 15 parts by mass or less.

Examples of the colorant include the following.
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, anthraquinone compounds, 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 further preferably 3 to 15 parts by mass with respect to 100 parts by mass of the binder resin. It is.

  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 this colorant master batch and other raw materials (binder resin, wax, etc.).

To the toner, 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. If the amount is 0.5 parts by mass or more, sufficient charging characteristics are easily obtained. On the other hand, if it is 10 parts by mass or less, the compatibility with other materials is unlikely to decrease, and it is difficult to be overcharged under low humidity.
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, anhydrides or esters thereof, or phenol derivatives such as 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 chelating pigments thereof, triphenylmethane dyes and lake lake pigments (as rake agents, 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.

The toner preferably contains a release agent. You may use 1 type, or 2 or more types of mold release agents as needed. 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 acid 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 preferably 0.1 to 20 parts by mass, more preferably 0.5 to 10 parts by mass, per 100 parts by mass of the binder resin.
Moreover, it is preferable that melting | fusing point prescribed | regulated by the maximum endothermic peak temperature at the time of temperature rising measured with the differential scanning calorimeter (DSC) of this mold release agent is 65-130 degreeC. More preferably, it is 80-125 degreeC. When the temperature is 65 ° C. or higher, the viscosity of the toner is difficult to decrease, and toner adhesion to the photoreceptor can be suppressed. When it is 130 ° C. or lower, the low-temperature fixability is improved.

The toner may be used as a fluidity improver (external additive) by adding externally to the toner particles so that the fluidity can be increased compared to before and after the addition. For example, fluorine resin powder such as vinylidene fluoride fine powder and polytetrafluoroethylene fine powder; fine powder silica such as wet process silica and dry process silica, fine powder titanium oxide, fine powder alumina and the like are silane coupling agents. It is particularly preferable that the surface treatment is performed with a titanium coupling agent or silicone oil, and the surface is hydrophobized, and the hydrophobization degree measured by a methanol titration test is in a range of 30 to 80. .
The fluidity improver is preferably used in an amount of 0.1 to 10 parts by weight, more preferably 0.2 to 8 parts by weight, based on 100 parts by weight of the toner particles.

  The magnetic carrier according to the present invention is preferably mixed with toner and used as a two-component developer. When the carrier mixing ratio at that time is preferably 2% by mass or more and 15% by mass or less, more preferably 4% by mass or more and 13% by mass or less as the toner concentration in the developer, usually good results are obtained. When it is 2% by mass or more, the image density is hardly lowered, and when it is 15% by mass or less, fog and in-flight scattering can be suppressed.

The two-component developer containing the magnetic carrier of the present invention comprises 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, Developing the electrostatic latent image using a two-component developer to form a toner image, transferring the toner image to a transfer material with or without an intermediate transfer member, and transferring The toner image can be used in an image forming method having a fixing step for fixing the toner image to the transfer material.
In addition, the image forming method includes a two-component developer in the developing unit, and a replenishment developer is supplied to the developing unit in accordance with a reduction in toner concentration of the two-component developer in the developing unit. You may have the structure which is. The magnetic carrier of the present invention can be used as a replenishment developer for use in such an image forming method. The image forming method may have a configuration in which the excess magnetic carrier in the developing device is discharged from the developing device as necessary.

Further, 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 unit contains 2 to 50 parts by mass of toner with respect to 1 part by mass of the magnetic carrier. It is preferable to do.
Next, an image forming apparatus including a developing device using a magnetic carrier, a two-component developer, and a replenishing developer will be described by way of example, but the present invention is not limited to this.

<Image forming method>
In FIG. 2, 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 the recording medium 12 by the transfer charger 11.
Here, as shown in FIG. 3, the image may be temporarily transferred from the electrostatic latent image carrier 1 to the intermediate transfer member 9 and then electrostatically transferred to a transfer material (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. 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. 3 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. 3, 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.
As a developing method, specifically, it is preferable to perform development in a state where the magnetic brush is in contact with the photosensitive member while applying an alternating voltage to the developer carrying member to form an alternating electric field in the developing region. . 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. When the thickness is 100 μm or more, the developer is sufficiently supplied and the image density is appropriate. When the thickness is 1000 μm or less, the magnetic lines of force from the magnetic pole S1 are difficult to spread, the density of the magnetic brush becomes appropriate, and dot reproducibility is improved. Moreover, the force which restrains a magnetic coat carrier becomes appropriate and can suppress carrier adhesion.

The voltage (Vpp) between the peaks of the alternating electric field is preferably 300 V or more and 3000 V or less, more preferably 500 V or more and 1800 V or less. The frequency is preferably 500 Hz or more and 10000 Hz or less, more preferably 1000 Hz or more and 7000 Hz or less, and can be appropriately selected and used depending on the process. In this case, the waveform of the AC bias for forming the alternating electric field includes a triangular wave, a rectangular wave, a sine wave, or a waveform with a changed duty ratio.
In order to cope with the change in the toner image formation speed, 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 300 V or more, a sufficient image density can be easily obtained, and the fog toner in the non-image area can be recovered well. When the voltage is 3000 V or less, the latent image is hardly disturbed via the magnetic brush, and the image quality is hardly deteriorated.

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 preferably 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, 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. As the outermost surface layer of the photoreceptor, for example, a charge injection layer or a protective layer may be used.

<Measurement of resistivity of magnetic carrier, porous magnetic core, and magnetic core>
The specific resistances of the magnetic carrier and the porous magnetic core are measured using a measuring device outlined in FIG. The magnetic carrier measures the specific resistance at an electric field strength of 2000 (V / cm), and the porous magnetic core measures the specific resistance at an electric field strength of 300 (V / cm).
The resistance measuring cell A has a cylindrical container (made of PTFE resin) 17, a lower electrode (made of stainless steel) 18, a support base (made of PTFE resin) 19, an upper electrode (made of stainless steel) having a hole with a cross-sectional area of 2.4 cm ^2. 20 is composed. The cylindrical container 17 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 21, and the thickness of the sample is set. Measure. As shown in FIG. 6A, when the gap when there is no sample is d1, and when the gap is d2 when the sample is filled so as to have a thickness of about 1 mm as shown in FIG. The thickness d is calculated by the following formula.
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 are used as a control processing computer.
As measurement conditions, a measured value d is input 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 is measured with a laser diffraction / scattering particle size distribution measuring apparatus “Microtrack MT3300EX” (manufactured by Nikkiso Co., Ltd.).
The measurement of the volume average particle diameter (D50) of the magnetic carrier and the porous magnetic core is performed by mounting a sample feeder “One-shot dry type sample conditioner Turbotrac” (manufactured by Nikkiso Co., Ltd.) for dry measurement. As a supply condition of Turbotrac, a dust collector is used as a vacuum source, an air volume is about 33 L / sec, and a pressure is 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 magnetization>
The amount of magnetization is measured by the following procedure using an oscillating magnetic field type magnetic property automatic recording apparatus BHV-30 manufactured by Riken Denshi Co., Ltd.
The cylindrical plastic container is packed sufficiently densely, while an external magnetic field of 79.6 (kA / m) (1000 oersted) is created, and the magnetization moment of the sample filled in the container is measured in this state. . Further, the actual mass of the sample filled in the container is measured to determine the magnetization strength (Am ² / kg) of the sample.

<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 by PD = −4σcos θ from the balance of force, 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, the measurement is performed under the following conditions and procedures using Autopore IV9520 of Shimadzu Corporation.
Measurement conditions Measurement environment 20 ℃
Measurement cell Sample volume 5 cm ³ , press-fitting volume 1.1 cm ³ , application for powder Measurement range 2.0 psia (13.8 kPa) or more, 5999.6 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) In the high pressure part, the range of 45.9 psia (316.3 kPa) or more and 59989.6 psia (413.6 kPa) or less is measured.
(4) The pore size distribution is calculated from the mercury injection pressure and the mercury injection amount.
(2), (3), and (4) are automatically performed by software attached to the apparatus.
From the pore size distribution measured as described above, the peak pore size that maximizes the differential pore volume in the pore size range of 0.1 μm to 3.0 μm is read.
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 is calculated using attached software, and is taken as a pore volume.

<Method for measuring acid value>
The acid value is the number of mg of potassium hydroxide necessary for neutralizing the acid contained in 1 g of the sample. That is, the number of mg of potassium hydroxide required to neutralize free fatty acids and resin acids contained in 1 g of a sample is referred to as an acid value.
In the present invention, the acid value is measured according to JIS K 0070-1992. Specifically, the measurement is performed according to the following procedure.
(1) Preparation of Reagent 1.0 g of phenolphthalein is dissolved in 90 mL of ethyl alcohol (95% by volume), and ion exchanged water is added to make 100 mL to obtain a phenolphthalein solution.
7 g of special grade potassium hydroxide is dissolved in 5 mL of water, and ethyl alcohol (95% by volume) is added to make 1 L. In order to avoid contact with carbon dioxide, etc., it is placed in an alkali-resistant container and allowed to stand for 3 days, followed by filtration to obtain a potassium hydroxide solution. The obtained potassium hydroxide solution is stored in an alkali-resistant container. As the factor of the potassium hydroxide solution, take 25 mL of 0.1 mol / L hydrochloric acid in an Erlenmeyer flask, add a few drops of the phenolphthalein solution, titrate with the potassium hydroxide solution, and the hydroxylation required for neutralization. Determined from the amount of potassium solution. As the 0.1 mol / L hydrochloric acid, one prepared according to JIS K 8001-1998 is used.
(2) Operation (A) Main test 2.0 g of a sample is precisely weighed into a 200 mL Erlenmeyer flask, and 100 mL of a mixed solution of toluene / ethanol (2: 1) is added and dissolved over 5 hours. Subsequently, several drops of the phenolphthalein solution is added as an indicator, and titration is performed using the potassium hydroxide solution. The end point of titration is when the light red color of the indicator lasts for about 30 seconds.
(B) Blank test Titration is performed in the same manner as above except that no sample is added (that is, only a mixed solution of toluene / ethanol (2: 1) is used).
(3) Calculation of acid value The obtained result is substituted into the following formula to calculate the acid value.
AV = [(B−A) × f × 5.61] / S
Here, AV: acid value (mgKOH / g), A: addition amount (mL) of potassium hydroxide solution in blank test, B: addition amount (mL) of potassium hydroxide solution in this test, f: potassium hydroxide Solution factor, S: sample (g).

<Separation of resin coating layer from magnetic carrier and fractionation of coating resins A and B in the resin coating layer>
As a method of separating the resin coating layer from the magnetic carrier, there is a method of taking the magnetic carrier in a cup and eluting the coating resin with toluene.
The eluted resin is dried and then dissolved in tetrahydrofuran (THF), and fractionated using the following apparatus.
[Device configuration]
LC-908 (manufactured by Nippon Analysis Industry Co., Ltd.)
JRS-86 (Company; repeat injector)
JAR-2 (Company; Autosampler)
FC-201 (Gilson, Hula cushion collector)
[Column structure]
JAIGEL-1H to 5H (20φ × 600 mm: preparative column) (manufactured by Nippon Analytical Industries, Ltd.)
[Measurement condition]
Temperature: 40 ° C
Solvent: THF
Flow rate: 5 ml / min.
Detector: RI
Based on the molecular weight distribution of the coating resin, the elution time for the peak molecular weight (Mp) of the coating resin A and the coating resin B is measured in advance using the resin configuration specified by the following method. Separate the ingredients. Thereafter, the solvent is removed and dried to obtain coating resin A and coating resin B.
In addition, an atomic group can be specified from the absorption wave number using a Fourier transform infrared spectroscopic analyzer (Spectrum One: manufactured by PerkinElmer), and the resin configuration of the coating resin A and the coating resin B can be specified.

<Separation of porous magnetic core from magnetic carrier>
For example, in the case of a magnetic carrier filled and coated with a thermoplastic resin, the porous magnetic core can be separated from the magnetic carrier by the following method, and the peak pore diameter and the like can be measured.
A Place about 5 g of magnetic carrier in a 100 ml beaker.
B Place about 50 ml of toluene in a beaker and shake with an ultrasonic shaker for 5 minutes.
C Allow to stand for several minutes after the shaking, stir the sample in the beaker 20 times with a neodymium magnet so that the bottom of the beaker is traced, and then flow only the toluene solution in which the coating resin and the filling resin are dissolved.
D While holding the sample in the beaker with a neodymium magnet from the outside, about 50 ml of toluene is again put into the beaker, and the above operations B and C are repeated 10 times.
E Change the solvent to chloroform and perform the above operations B and C once.
F The whole beaker is put into a vacuum dryer to dry and remove the solvent (use a vacuum dryer with a solvent trap, temperature 50 ° C., degree of vacuum −0.093 MPa or less, drying time 12 hours).
G Remove the beaker from the vacuum dryer and let it cool for about 20 minutes.

<Measurement of weight average molecular weight (Mw), peak molecular weight (Mp), and content ratio of coating resin A, coating resin B, and coating resin in the resin coating layer>
The weight average molecular weight (Mw) and peak molecular weight (Mp) of the coating resin A, the coating resin B, and the coating resin were measured by gel permeation chromatography (GPC) according to the following procedure.
First, the measurement sample was produced as follows.
A sample (a coating resin separated from a magnetic carrier, a coating resin A and a coating resin B separated by a preparative device) and tetrahydrofuran (THF) were mixed at a concentration of 5 mg / ml, and the mixture was stirred at room temperature for 24 hours. Let stand and dissolve the sample in THF. Then, let the thing which passed the sample processing filter (Mishori disk H-25-2 Tosoh Corporation make) the sample of GPC.
Next, using a GPC measurement apparatus (HLC-8120GPC manufactured by Tosoh Corporation), measurement is performed under the following measurement conditions according to the operation manual of the apparatus.
(Measurement condition)
Equipment: High-speed GPC “HLC8120 GPC” (manufactured by Tosoh Corporation)
Column: Seven series of Shodex KF-801, 802, 803, 804, 805, 806, 807 (manufactured by Showa Denko KK)
Eluent: THF
Flow rate: 1.0 ml / min
Oven temperature: 40.0 ° C
Sample injection volume: 0.10 ml
Moreover, in calculating the weight average molecular weight (Mw) and the peak molecular weight (Mp) of the sample, a calibration curve was obtained using standard polystyrene resin (TSK standard polystyrene F-850, F-450, F-288, F-128, manufactured by Tosoh Corporation). F-80, F-40, F-20, F-10, F-4, F-2, F-1, A-5000, A-2500, A-1000, A-500) Is used.
The content ratio is obtained from the peak area ratio in the molecular weight distribution measurement. As shown in FIG. 4, when the region 1 and the region 2 were completely separated, the resin content ratio was obtained from the area ratio of each region. As shown in FIG. 5, when each region overlaps, it is divided by a line drawn vertically from the inflection point of the GPC molecular weight distribution curve to the horizontal axis, and the content ratio is calculated from the area ratio of region 1 and region 2 shown in FIG. Ask for.

<Measurement of current value>
800 g of the magnetic carrier is weighed and exposed to an environment of temperature 20 to 26 ° C. and humidity 50 to 60% RH for 15 minutes or more. Thereafter, the current value is measured at an applied voltage of 500 V using a current value measuring device in which the magnet roller and the Al base tube shown in FIG.

<Measurement of MR1 and MR2 of magnetic carrier cross section>
1. Cutting out a cross section A cross section processing of a magnetic carrier uses a focused ion beam processing observation apparatus (FIB) and FB-2100 (manufactured by Hitachi High-Technologies Corporation). A carbon paste is applied on an FIB sample stage (metal mesh), a small amount of magnetic carriers are fixed on the FIB sample stand so that each particle is present independently, and a sample is prepared by depositing platinum as a conductive film. The sample is set in an FIB apparatus, and rough processing is performed (beam current: 39 nA) using an acceleration voltage of 40 kV and a Ga ion source, followed by finishing (beam current: 7 nA), and the carrier cross section as a sample is cut out.
The cross section of the magnetic carrier selected as the measurement sample is a magnetic carrier satisfying D50 × 0.9 ≦ H ≦ D50 × 1.1, where H is the length of the line segment that is the maximum length of the cross section of the carrier particle. Prepare 100 cross-sectional samples to be targeted and within this range.
2. Analysis of the component derived from the porous magnetic core of the magnetic carrier and the resin component Using a scanning electron microscope (S4700, manufactured by Hitachi, Ltd.), the elements of the magnetic component and the resin component of the magnetic carrier cross-section sample were scanned. Analysis is performed using elemental analysis means (energy dispersive X-ray analyzer EDAX) attached to the electron microscope.
The observation magnification is set to 10,000 times or more, and an area composed of only the magnetic component is observed at an acceleration voltage of 20 kV and an uptake time of 100 sec to identify elements in the component derived from the porous magnetic core. Similarly, the element in the resin component is also specified.
The component derived from the porous magnetic core is the element specified above. However, oxygen is contained in both the component derived from the porous magnetic core and the resin component, and it is difficult to specify the content ratio. Therefore, it is excluded from the components derived from the porous magnetic core. That is, the component derived from the porous magnetic core in the present invention is a metal element in the ferrite constituting the porous magnetic core.
The resin component is the element specified above, but oxygen is excluded from the resin component because it is contained in both the magnetic component and the resin component and it is difficult to specify the content ratio. In addition, since the energy dispersive X-ray analyzer used in the present invention cannot identify hydrogen, hydrogen is also excluded from the resin component. That is, in the present invention, when an acrylic resin composed of carbon, hydrogen, and oxygen is used, the element that becomes the resin component is only carbon. In the case of silicone resin, carbon and silicon are used.
3. Measurement of metal component abundance ratio and resin abundance ratio of cross section The above-mentioned magnetic carrier cross section is magnified 2000 times and observed using a scanning electron microscope.
In the obtained cross-sectional image, two straight lines that are parallel to the maximum line length of the resin-filled magnetic core particles and separated from the line segment by 2.5 μm are A and B. A straight line C that passes through the intersection of the line segment and the contour line of the resin-filled magnetic core particle, is orthogonal to the line segment, is parallel to the straight line C, and extends from the straight line C to 5 toward the center of the magnetic carrier. Assume a straight line D separated by 0 μm.
A region surrounded by the contour line of the resin-filled magnetic core particles between the straight lines A and B and the straight lines A, B, and D and in contact with the straight line C is defined as R1.
By dividing the region in this way, the measurement can be performed under the condition that the influence of the coating resin component is suppressed as much as possible.
Further, a region surrounded by the straight lines A, B, and D and a straight line E that is parallel to the straight line D and is 5.0 μm away from the straight line D toward the center of the magnetic carrier is R2.
For each of the R1 and R2 regions, the element mass analysis (mass%) is measured using an elemental analysis means at an acceleration voltage of 20 kV and an uptake time of 100 sec.
For example, in the case of a magnetic carrier in which the magnetic core particle component is Mn-Mg-Sr ferrite, filled with silicone resin, and coated with acrylic resin, the elements of the metal component are iron, manganese, magnesium, and strontium The elements of the resin component are carbon and silicon. The total mass ratio of the mass ratio (mass%) of carbon and silicon elements in the R1 region at this time is JR1, and the total mass ratio of the mass ratio (mass%) of elements of iron, manganese, magnesium, and strontium is FR1. Become. Further, the total mass ratio of the mass ratio (mass%) of the carbon and silicon elements in the R2 region is JR2, and the total mass ratio of the mass ratio (mass%) of the elements of iron, manganese, magnesium, and strontium is FR2.
MR2 / MR1 of one magnetic carrier particle is calculated from the above values, and an arithmetic average value of 80 particles obtained by cutting the upper and lower 10 points out of 100 particle cross-sectional measurements is defined as MR2 / MR1 of the magnetic carrier cross section.

<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 with a fine particle size distribution measuring apparatus “Coulter Counter Multisizer 3” (registered trademark, Beckman And Beckman Coulter M, a dedicated software for setting measurement conditions and analyzing measurement data.
Ultrasizer 3 Version 3.51 "(manufactured by Beckman Coulter, Inc.) was 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, the dirt and bubbles in the aperture tube are removed by the “aperture tube flush” function of the dedicated 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 disperser “Ultrasonic Dispersion System Tetora 150” (manufactured by Nikkiki Bios) with 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 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 (1) installed in the sample stand, the electrolytic solution (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 may
After performing the measurement of (3), (1) graph / volume% is set with dedicated software, and the measurement result chart is displayed in volume%. (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.

<Measurement of amount of resin filled in magnetic carrier>
For example, when the coating resin is not dissolved in toluene and a thermoplastic resin is used as the filling resin, the amount of the filling resin can be measured from the magnetic carrier by the following method.
A Weigh about 5 g of the sample to be measured, and grind it thoroughly with a mortar.
B After precisely weighing a 100 ml beaker (measurement value 1), put about 5 g of a sample to be measured, and precisely weigh the total mass of the sample and the beaker (measurement value 2).
C Place about 50 ml of toluene in a beaker and shake with an ultrasonic shaker for 5 minutes.
D After shaking is completed, the sample is left to stand for several minutes, and the sample in the beaker is stirred 20 times with a neodymium magnet so that the bottom of the beaker is traced, and then only the toluene solution in which the filled resin is dissolved is allowed to flow as waste liquid.
E While holding the sample in the beaker from the outside with a neodymium magnet, about 50 ml of toluene is again put in the beaker, and the above operations B and C are repeated 10 times.
F The solvent is changed to chloroform and the above operations B and C are performed once.
G The beaker is put into a vacuum dryer, and the solvent is dried and removed (use a vacuum dryer with a solvent trap, temperature 50 ° C., vacuum degree −0.093 MPa or less, drying time 12 hours).
H Remove the beaker from the vacuum dryer, let it cool for about 20 minutes, and then weigh the mass precisely (measurement value 3).
I From the measured values obtained as described above, the filling amount (% by mass) according to the following formula
Is calculated.
Filled resin amount = (initial sample weight−sample weight after filling resin dissolution) / sample weight × 100
In the above formula, the sample weight is obtained by calculating (Measurement Value 2 -Measurement Value 1), and the sample weight after dissolution of the filled resin is obtained by (Measurement Value 3 -Measurement Value 1).

<Measurement of amount of coating resin of magnetic carrier>
For example, when the filling resin is not dissolved in toluene and a thermoplastic resin is used as the coating resin, the amount of the coating resin can be measured from the magnetic carrier by the following method.
A After accurately weighing a 100 ml beaker (measurement value 1), put about 5 g of a sample to be measured, and precisely weigh the total mass of the sample and the beaker (measurement value 2).
B Place about 50 ml of toluene in a beaker and shake with an ultrasonic shaker for 5 minutes.
C Allow to stand for a few minutes after shaking, stir the sample in the beaker 20 times with a neodymium magnet so that the bottom of the beaker is traced, and then flow only the toluene solution in which the coating resin is dissolved.
D While holding the sample in the beaker with a neodymium magnet from the outside, about 50 ml of toluene is again put into the beaker, and the above operations B and C are repeated 10 times.
E Change the solvent to chloroform and perform the above operations B and C once.
F The whole beaker is put into a vacuum dryer to dry and remove the solvent (use a vacuum dryer with a solvent trap, temperature 50 ° C., degree of vacuum −0.093 MPa or less, drying time 12 hours).
G Take out the beaker from the vacuum dryer, let it cool for about 20 minutes, and then weigh the mass precisely (measurement value 3).
H From the measured values obtained as described above, the coating resin amount (% by mass) is calculated according to the following formula.
Amount of coating resin = (initial sample mass−sample mass after dissolution of coating resin) / sample mass × 100
In the above formula, the sample mass is obtained by calculating (Measurement Value 2 -Measurement Value 1), and the sample mass after dissolution of the coating resin is obtained by (Measurement Value 3 -Measurement Value 1).

  EXAMPLES Hereinafter, although this invention is demonstrated more concretely with reference to an Example, this invention is not limited only to these Examples. In the following formulations, parts are based on mass unless otherwise specified.

<Examples of production of porous magnetic cores 1 to 10 and magnetic core 1>
Process 1 (weighing / mixing process)
Fe ₂ O ₃ 69.3 mass%
MnCO ₃ 27.5% by mass
Mg (OH) ₂ 1.7% by mass
SrCO ₃ 1.5% by mass
The ferrite raw material was weighed, 20 parts of water was added to 80 parts 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 by a spray dryer (Okawara Chemical Co., Ltd.), then baked in a batch-type electric furnace in a nitrogen atmosphere (oxygen concentration: 1.0% by volume) at a temperature of 1070 ° C. for 3.0 hours, and calcined. 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 with a wet ball mill using 1/8 inch stainless beads for 3.5 hours. 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 1.1 μm.
Process 4 (granulation process)
To 100 parts of the calcined ferrite slurry, 1.0 part of ammonium polycarboxylate as a dispersant and 1.5 parts of polyvinyl alcohol as a binder are added, and then granulated into spherical particles with a spray dryer (manufactured by Okawara Kako Co., Ltd.). , Dried. After adjusting the particle size of the obtained granulated product, it was heated at 720 ° 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: 1.0% by volume), the time from room temperature to the firing temperature (1100 ° C.) was 1.7 hours, and the temperature was maintained at 1180 ° C. for 4.5 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 physical properties are shown in Table 1.
Among the production examples of the porous magnetic core 1, porous magnetic cores 2 to 10 were produced by changing the firing temperature or firing time of each step. In addition, the magnetic core 1 was produced by adjusting the firing temperature in step 5. Table 1 shows the physical properties of the obtained porous magnetic cores 2 to 10 and the magnetic core 1.

<Manufacture of resin composition (filling resin) 1-4>
Table 2 shows methyl silicone oligomer (KR-400: manufactured by Shin-Etsu Silicone Co., Ltd.) as a resin component and γ-aminopropyltriethoxysilane (KBM-903: manufactured by Shin-Etsu Silicone Co., Ltd.) as an additive. Filling resin 1 was obtained by mixing at the stated ratio.
Further, a filling resin only of methyl silicone oligomer (KR-400: manufactured by Shin-Etsu Silicone Co., Ltd.) was used as filling resin 2.
Filling resin 3 was obtained in the same manner as filling resin 1 except that methylphenyl silicone oligomer (KR-401: manufactured by Shin-Etsu Silicone Co., Ltd.) was used as the resin component.
Moreover, the filling resin 4 was obtained like the filling resin 1 except having used methyl silicone resin (KR-251: Shin-Etsu Silicone Co., Ltd.) as a resin component, and using toluene as a solvent component.

<Manufacture of coating resin A-1 to A-3>
The raw materials listed in Table 3 (total of 109.0 parts) were added to a four-necked flask equipped with a reflux condenser, a thermometer, a nitrogen suction pipe and a mixing type stirring apparatus, and further 100 parts of toluene, 100 parts of methyl ethyl ketone, 2.4 parts of azobisisovaleronitrile was added, and kept at 80 ° C. for 10 hours under a nitrogen stream to obtain a coating resin A-1 solution (solid content: 35% by mass).
Moreover, using the raw materials described in Table 3, coating resins A-2 to A-3 were obtained in the same manner. Table 3 shows the physical properties.

<Manufacture of coating resin B-1 to B-7>
The raw materials listed in Table 4 (total 101.6 parts) were added to a four-necked flask equipped with a reflux condenser, a thermometer, a nitrogen suction pipe, and a mixing type stirring apparatus, and further 50 parts of toluene, 100 parts of methyl ethyl ketone, 2.4 parts of azobisisovaleronitrile was added and kept at 80 ° C. for 10 hours under a nitrogen stream to obtain a coating resin B-1 solution (solid content: 40% by mass).
Moreover, using the raw materials described in Table 4, coating resins B-2 to B-7 were obtained in the same manner. Table 4 shows the physical properties.

<Production example of magnetic carriers 1 to 22>
Process 1 (filling process)
The porous magnetic core 1 is placed in a stirring vessel of a 100-part mixing stirrer (universal stirrer NDMV type manufactured by Dalton), the temperature is kept at 60 ° C., and the resin composition 1 shown in Table 2 at normal pressure is obtained. It was dripped at the porous magnetic core.
After completion of dropping, stirring was continued while adjusting the time, the temperature was raised to 70 ° C., and the resin composition was filled in the particles of the porous magnetic core.
The resin-filled magnetic core particles obtained after cooling are transferred to a mixer having a spiral blade in a rotatable mixing container (Drum mixer UD-AT type, manufactured by Sugiyama Heavy Industries Co., Ltd.). The temperature was raised to the curing temperature of the resin composition 1 shown in Table 2 while stirring at a temperature rising rate of minutes. Then, heating and stirring were continued for the curing time shown in Table 2 while maintaining the curing temperature shown in Table 2.
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. Furthermore, coarse particles were removed with a vibration sieve to obtain resin-filled magnetic core particles filled with resin.
Process 2 (resin coating process)
The resin for coating (A-1 and B-1) shown in Table 3 and Table 4 was diluted with toluene so that the resin component would be 5% at the ratio shown in Table 5, and sufficiently stirred. Prepared. Thereafter, in a planetary motion type mixer (Nauta mixer VN type manufactured by Hosokawa Micron Corporation) maintained at a temperature of 60 ° C., the coating resin shown in Table 6 as a solid content of the resin component with respect to 100 parts of the resin-filled magnetic core particles. The resin solution was added so that the amount became equal. As a method of charging, a half amount of the resin solution was charged, and solvent removal and coating operation were performed for 30 minutes. Next, a half amount of the resin solution was added, and the solvent removal and coating operation were performed for 40 minutes.
Thereafter, the magnetic carrier coated with the coating resin composition was 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 was separated from a low magnetic force product by magnetic separation, passed through a sieve having an opening of 150 μm, and then classified by an air classifier to obtain a magnetic carrier 1.
Magnetic carriers 2 to 22 were obtained in the same manner except that the coating resin layer was formed using the magnetic core and the resin composition (filling resin) shown in Table 6 and the formulations shown in Tables 5 and 6. The magnetic carrier 22 did not perform step 1. Table 6 shows physical property values of the obtained magnetic carrier.

[Synthesis of crystalline polyester resin]
Into a reaction vessel equipped with a cooling tube, a stirrer and a nitrogen introduction tube, 1,6-hexanediol 1200 parts, decanedioic acid 1200 parts, and dibutyltin oxide 0.4 parts as a catalyst were added, and then the vessel was subjected to decompression. The inside air was made an inert atmosphere with nitrogen gas, and the mixture was stirred at 180 rpm for 4 hours by mechanical stirring. Thereafter, the temperature was gradually raised to 210 ° C. under reduced pressure, and the mixture was stirred for 1.5 hours. When the mixture became viscous, the reaction was stopped by air cooling to obtain [Crystalline Polyester Resin].

[Production example of cyan toner]
7 parts of the above crystalline polyester resin. 93 parts of binder resin (Tg: 57 ° C., acid value: 12 mgKOH / g, hydroxyl value: 15 mgKOH / g, polyester (dihydric alcohol component: polyoxypropylene (2.2)- 2,2-bis (4-hydroxyphenyl) propane 0.20 mol polyvalent carboxylic acid component: terephthalic acid 0.17 mol trimellitic anhydride 0.01 mol))
・ C. I. Pigment Blue 15: 3 5.5 parts, 3,5-di-t-butylsalicylic acid aluminum compound 0.2 part, normal paraffin wax (melting point: 78 ° C.) 6 parts 75J type, manufactured by Mitsui Mining Co., Ltd.) and then mixed in a twin-screw kneader (trade name: 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 150 ° C.). The obtained kneaded material was cooled and coarsely crushed with a hammer mill, and then finely pulverized with a mechanical pulverizer (trade name: T-250, manufactured by Turbo Kogyo Co., Ltd.) at a Feed amount of 15 kg / hr. A weight average particle diameter of 5.5 μm, 55.6% by number of particles having a particle diameter of 4.0 μm or less, and 0.8% by volume of particles having a particle diameter of 10.0 μm or more were obtained. .
The obtained particles were classified using a rotary classifier (trade name: TTSP100, manufactured by Hosokawa Micron Corporation) to cut fine powder and coarse powder. Cyanide having a weight average particle size of 6.0 μm, abundance of particles having a particle size of 4.0 μm or less is 27.8% by number, and abundance of particles having a particle size of 10.0 μm or more is 2.2% by volume Toner particles 1 were obtained.
Furthermore, the following materials were put into a Henschel mixer (trade name: FM-75 type, manufactured by Nihon Coke Kogyo Co., Ltd.), the peripheral speed of the rotary blade was 35.0 (m / sec), and the mixing time was 3 minutes. Thus, an external additive was adhered to the surface of the cyan toner particles 1 to obtain cyan toner 1. Cyan toner particles 1: 100 parts Silica particles: 3.5 parts (Silica particles prepared by the sol-gel method are surface-treated with 1.5% by mass of hexamethyldisilazane and then adjusted to a desired particle size distribution by classification. )
Titanium oxide particles: 0.9 part (surface-treated with an octylsilane compound of metatitanic acid having anatase crystallinity)
Strontium titanate particles: 1.0 part (surface treated with an octylsilane compound)

<Examples 1 to 17 and Comparative Examples 1 to 5>
9 parts of cyan toner 1 was added to 91 parts of magnetic carrier 1 and shaken with a shaker (YS-8D type: manufactured by Yayoi Co., Ltd.) to prepare 200 g of a two-component developer. The amplitude condition of the shaker was 200 rpm for 2 minutes.
On the other hand, 95 parts of cyan toner 1 was added to 5 parts of magnetic carrier 1 and mixed in a V-type mixer for 5 minutes in an environment of normal temperature and humidity of 23 ° C./50% RH to obtain a replenishment developer.
Similarly, developers of Examples 2 to 17 were obtained using magnetic carriers 2 to 17, respectively. Moreover, the magnetic carrier of Comparative Examples 1-5 was obtained using the magnetic carriers 18-22, respectively.
The following evaluation was performed using these two-component developers and replenishment developers.
A Canon color copier imageRUNNER ADVANCE C3330 modified machine was used as the image forming apparatus.
A two-component developer was placed in the developing unit, a replenishment developer container containing a replenishment developer was set, an image was formed, and various evaluations were performed before and after the durability test.
As a durability test, in a printing environment at a temperature of 30 ° C./humidity of 80 RH% (hereinafter “H / H”), an FFH output chart with an image ratio of 5% was intermittently output. In a printing environment of temperature 23 ° C./humidity 5RH% (hereinafter “N / L”), three charts of FFH output with an image ratio of 1% were output intermittently.
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. The number of output sheets per day was 1000.
(conditions)
Paper: Laser beam printer paper CS-680 (68.0 g / m ² ) (Canon Marketing Japan Inc.)
Image formation speed: A4 size, output at 35 (sheets / min) (3-sheet intermittent output)
Development conditions: The development contrast can be adjusted to an arbitrary value, and it has been modified so that automatic correction by the main unit does not work. Modified to output images in cyan single color. Modified to output unfixed images.

Each evaluation item is shown below.
(1) Change in gradation before and after the endurance of 20000 sheets An image in which each pattern was set to the following density was output in the initial setting. Then, a similar image was output immediately after the 20000 sheet durability test under the HH environment, and the difference in gradation between the initial stage and the 20000 sheet durability test was confirmed. The image was judged by measuring each image density with an X-Rite color reflection densitometer (Color reflection densitometer X-Rite 504). The evaluation was performed with cyan single color.
Pattern 1: 0.10 to 0.13
Pattern 2: 0.25 to 0.28
Pattern 3: 0.40 to 0.43
Pattern 4: 0.55-0.58
Pattern 5: 0.70 to 0.73
Pattern 6: 0.85-0.88
Pattern 7: 1.00 to 1.03
Pattern 8: 1.15 to 1.18
Pattern 9: 1.30 to 1.33
Pattern 10: 1.45 to 1.48
Judgment criteria are as follows.
A: All pattern images satisfy the above density range.
B: One pattern image deviates from the above density range.
C: Two pattern images deviate from the above density range.
D: Three pattern images deviate from the above density range.
E: Four pattern images deviate from the above density range.
F: Five pattern images deviate from the above density range.
G: Six pattern images deviate from the above density range.
H: Seven pattern images deviate from the above density range.
I: Eight pattern images deviate from the above density range.
J: Nine or more pattern images deviate from the above density range.

(2) Change in gradation before and after standing for 7 days after HH endurance After the 20000 sheet endurance test in the HH environment in the evaluation of (1), it was left in an HH environment for 7 days and a similar pattern image was output. The difference in gradation before and after being left was confirmed. The image was judged by measuring each image density with an X-Rite color reflection densitometer (Color reflection densitometer X-Rite 504). The evaluation was performed with cyan single color.
Judgment criteria are as follows.
A: All pattern images satisfy the above density range.
B: One pattern image deviates from the above density range.
C: Two pattern images deviate from the above density range.
D: Three pattern images deviate from the above density range.
E: Four pattern images deviate from the above density range.
F: Five pattern images deviate from the above density range.
G: Six pattern images deviate from the above density range.
H: Seven pattern images deviate from the above density range.
I: Eight pattern images deviate from the above density range.
J: Nine or more pattern images deviate from the above density range.

(3) Image scattering before and after standing for 7 days after HH durability (1) Immediately after the 20000 sheet durability test under the HH environment in the evaluation, the image shown in FIG. 8 (19 lines, line width 100 μm, interval) Three unfixed images (300 μm, line length 1.0 cm) were output and fixed in an oven at 100 ° C. for 3 minutes.
The lines of this image were observed using a magnifying glass, and the number of scattered toner particles other than the line portion was counted. The average value among the three sheets was evaluated as Z. The evaluation criteria are as follows.
A: Spatter 19 or less B: 20 or more and 24 or less C: 25 or more and 29 or less D: 30 or more and 34 or less E: 35 or more and 39 or less F: 40 or more and 44 or less G: 45 49 or more and 49 or less H: 50 or more and 54 or less I: 55 or more and 59 or less J: 60 or more

(4) Change in gradation before and after endurance of 20000 sheets An image in which each pattern was set to the density shown below was output in the initial setting. A similar image was output immediately after the 20000 sheet endurance test under the NL environment, and the difference in gradation between the initial stage and the 20000 sheet endurance test was confirmed. The image was judged by measuring each image density with an X-Rite color reflection densitometer (Color reflection densitometer X-Rite 404A). The evaluation was performed with cyan single color.
Pattern 1: 0.10 to 0.13
Pattern 2: 0.25 to 0.28
Pattern 3: 0.40 to 0.43
Pattern 4: 0.55-0.58
Pattern 5: 0.70 to 0.73
Pattern 6: 0.85-0.88
Pattern 7: 1.00 to 1.03
Pattern 8: 1.15 to 1.18
Pattern 9: 1.30 to 1.33
Pattern 10: 1.45 to 1.48
Judgment criteria are as follows.
A: All pattern images satisfy the above density range.
B: One pattern image deviates from the above density range.
C: Two pattern images deviate from the above density range.
D: Three pattern images deviate from the above density range.
E: Four pattern images deviate from the above density range.
F: Five pattern images deviate from the above density range.
G: Six pattern images deviate from the above density range.
H: Seven pattern images deviate from the above density range.
I: Eight pattern images deviate from the above density range.
J: Nine or more pattern images deviate from the above density range.

(5) Comprehensive judgment The evaluation rank in the evaluation S to the evaluation Z is quantified (A = 10, B = 9, C = 8, D = 7, E = 6, F = 5, G = 4, H = 3, I = 2, J = 1), and the total value was determined according to the following criteria.
A: 38 to 40 B: 34 to 37 C: 28 to 33 D: 22 to 27 E: 21 The results are shown in Table 7.

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: Transfer material (recording medium), 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 or porous magnetic core, 22: electrometer, 23: processing computer, d1: gap when no sample is present, d2: Gap when filling sample

Claims (14)

A magnetic material having a porous magnetic core, a resin-filled magnetic core particle having a filled resin present in the pores of the porous magnetic core, and a resin coating layer present on the surface of the resin-filled magnetic core particle Career,
In the pore size distribution of the porous magnetic core,
The peak pore diameter that maximizes the differential pore volume in the range of 0.1 μm or more and 3.0 μm or less is 0.20 μm or more and 0.70 μm or less,
The pore volume, which is the integral value of the differential pore volume in the range of 0.1 μm or more and 3.0 μm or less, is 20 mm ³ / g or more and 57 mm ³ / g or less,
The magnetic carrier is in the region R1 and the region R2 defined as follows:
The mass-based proportions of the resin component-derived composition are JR1 and JR2, respectively, and the mass-based proportions of the composition derived from the porous magnetic core are FR1 and FR2, respectively.
Furthermore, when JR1 / FR1 is MR1 and JR2 / FR2 is MR2, MR1 and MR2 are
0.20 ≦ MR2 / MR1 ≦ 0.90
A magnetic carrier characterized by satisfying the relationship:
(Region R1 is a cross-sectional image of the magnetic carrier. Let straight lines be straight lines A and B;
A straight line passing through the intersection of the line segment and the contour line of the resin-filled magnetic core particle and orthogonal to the line segment is defined as a straight line C.
When a straight line that is parallel to the straight line C and is 5.0 μm away from the straight line C toward the center of the magnetic carrier is defined as a straight line D,
It is a region surrounded by the contour line of the resin-filled magnetic core particles and the straight lines A, B and D and in contact with the straight line C.
The region R2 is a region surrounded by the straight lines A, B, and D and a straight line E that is parallel to the straight line D and is 5.0 μm away from the straight line D toward the center of the magnetic carrier. )   2. The magnetic carrier according to claim 1, wherein a content of the filling resin is 1.0 part by mass or more and 6.0 parts by mass or less with respect to 100 parts by mass of the porous magnetic core.   The content of the coating resin forming the resin coating layer is 0.5 parts by mass or more and 3.0 parts by mass or less with respect to 100 parts by mass of the resin-filled magnetic core particles. Magnetic carrier.   The magnetic carrier according to any one of claims 1 to 3, wherein a current value when 500 V of the magnetic carrier is applied is 10.0 µA or more and 100.0 µA or less. The resin coating layer is a (meth) acrylic acid ester having at least an alicyclic hydrocarbon group, other (meth) acrylic monomers other than the (meth) acrylic acid ester having an alicyclic hydrocarbon group, And a macromonomer copolymer,
The macromonomer is a polymer of at least one monomer selected from methyl acrylate, methyl methacrylate, butyl acrylate, butyl methacrylate, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, styrene, acrylonitrile, and methacrylonitrile. The magnetic carrier according to any one of claims 1 to 4, which is a coalescence. The resin coating layer is
i) a copolymer of a monomer containing a (meth) acrylic acid ester having an alicyclic hydrocarbon group and a macromonomer, the acid value of which is 0.0 mgKOH / g or more and 3.0 mgKO
A coating resin A of H / g or less;
ii) Polymers of other (meth) acrylic monomers other than the (meth) acrylic acid ester having an alicyclic hydrocarbon group, and having an acid value of 3.5 mgKOH / g or more and 50.0 mgKOH / g The magnetic carrier as described in any one of Claims 1-4 containing the following resin B for coating | covering. The magnetic resistance according to any one of claims 1 to 6, wherein a specific resistance of the magnetic carrier at an electric field strength of 2000 V / cm is 1.0 x 10 ⁶ Ω · cm or more and 1.0 x 10 ¹⁰ Ω · cm or less. Career.   The magnetic carrier according to claim 1, wherein the filling resin is a silicone resin. A two-component developer containing a toner containing a binder resin, a colorant and a release agent, and a magnetic carrier,
A two-component developer, wherein the magnetic carrier is the magnetic carrier according to any one of claims 1 to 8.   The two-component developer according to claim 9, wherein the toner contains a crystalline polyester. A charging step for charging the electrostatic latent image carrier,
An electrostatic latent image forming step of forming an electrostatic latent image on the surface of the electrostatic latent image carrier;
Developing the electrostatic latent image with a two-component developer to form a toner image;
An image forming method comprising a transfer step of transferring the toner image to a transfer material with or without an intermediate transfer member, and a fixing step of fixing the transferred toner image to the transfer material,
The image forming method, wherein the two-component developer is the two-component developer according to claim 9 or 10. An image forming method in which a replenishing developer is replenished to the developing device in accordance with a decrease in toner concentration of a two-component developer in the developing device,
The replenishment developer contains a magnetic carrier and a toner containing a binder resin, a colorant and a release agent,
The replenishment developer contains 2 parts by weight or more and 50 parts by weight or less of the toner with respect to 1 part by weight of the magnetic carrier.
The image forming method according to claim 1, wherein the magnetic carrier is the magnetic carrier according to claim 1. A charging step for charging the electrostatic latent image carrier,
An electrostatic latent image forming step of forming an electrostatic latent image on the surface of the electrostatic latent image carrier;
A developing step of developing the electrostatic latent image with a two-component developer in a developing unit 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 a fixing step of fixing the transferred toner image to the transfer material,
A replenishment developer for use in an image forming method in which a replenishment developer is replenished to the developer in response to a decrease in toner concentration of the two-component developer in the developer,
The replenishment developer contains a magnetic carrier and a toner containing a binder resin, a colorant and a release agent,
The replenishment developer contains 2 parts by weight or more and 50 parts by weight or less of the toner with respect to 1 part by weight of the magnetic carrier.
The replenishment developer, wherein the magnetic carrier is the magnetic carrier according to claim 1. A charging step for charging the electrostatic latent image carrier,
An electrostatic latent image forming step of forming an electrostatic latent image on the surface of the electrostatic latent image carrier;
A developing step of developing the electrostatic latent image with a two-component developer in a developing unit to form a toner image;
13. The image forming method according to claim 12, further comprising: a transfer step of transferring the toner image to a transfer material with or without an intermediate transfer member; and a fixing step of fixing the transferred toner image to the transfer material. .