JP2011158742A - Two-component developer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a two-component developer capable of suppressing density variation of images under duration, image quality degradation in intermittent printing at a high process speed, carrier deposition and toner scattering, and having high developing ability. <P>SOLUTION: The two-component developer contains at least a magnetic carrier and toner, wherein the toner contains toner particles containing at least a binder resin and a wax, and the magnetic carrier contains at least magnetic core particles and a resin and has a true specific gravity of 2.5-4.2 g/cm<SP>3</SP>. The two-component developer contains 4-20 pts.mass of the toner based on 100 pts.mass of the magnetic carrier, and E<SB>100 mm/sec</SB>(mJ) and E<SB>10 mm/sec</SB>(mJ) of the two-component developer and ΔE (mJ) given by subtracting the E<SB>100 mm/sec</SB>from the E<SB>10 mm/sec</SB>satisfy specific relationships. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a two-component developer used in electrophotography and electrostatic recording.

In the electrophotographic method, the step of developing the electrostatic charge image forms an image by depositing charged toner on the electrostatic charge image using Coulomb force with the electrostatic charge image. As a developer for developing an electrostatic charge image using a toner, a one-component developer using a magnetic toner in which a magnetic material is dispersed in a resin, and a two-component system using a mixture of a non-magnetic toner and a magnetic carrier. Broadly divided into developers.
In particular, the latter is preferably used in full-color image forming apparatuses such as full-color copying machines or full-color printers that require high image quality.
In recent years, full-color image forming apparatuses are required to have higher durability. Therefore, by controlling the flowability of the developer, a developer has been proposed in which deterioration fogging in a low-temperature and low-humidity environment is reduced and the followability of a solid image is good. Specifically, it is a developer in which the flow rate index 25 FRI value of the two-component developer is controlled to 0 or more and 2.0 or less. By using such a developer, the toner surface has a toner surface that is difficult to be embedded, or even if the toner external additive is embedded, it has fluidity, chargeability, and other characteristics as toner. High toner can be obtained. [25 FRI = (total energy at blade rotation speed 10 mm / s / total energy at 100 mm / s)] (Patent Document 1).
However, when intermittent printing is performed at a high speed of a process speed of 200 mm / sec or more, the image quality is deteriorated, the density variation of the image is large, and improvement is necessary.

JP 2007-183607 A

  The present invention is a two-component developer that has high developability and is capable of reducing the image density deterioration during endurance and reducing the image quality deterioration of intermittent printing at a high process speed, and further suppressing carrier adhesion and toner scattering. For the purpose of provision.

As a result of intensive studies, the inventors have determined that there is a deterioration in image quality when intermittent printing is performed at a high process speed, fluctuations in image density during durability, the true specific gravity of the magnetic carrier, and the total energy of the two-component developer. We found that there is a correlation.
That is, a two-component developer containing at least a magnetic carrier and a toner, wherein the toner contains toner particles containing at least a binder resin and a wax, and the magnetic carrier includes at least magnetic core particles and a resin. And the true specific gravity is 2.5 g / cm ³ or more and 4.2 g / cm ³ or less, and the two-component developer is 4 parts by mass or more and 20 parts by mass or less of toner with respect to 100 parts by mass of the magnetic carrier. The two-component developer is contained at a ratio of E _{100 mm / sec} (mJ) and E _{100 mm / sec} (mJ) of the two-component developer, and E _{100 mm / sec} is subtracted from the E _{10 mm / sec} . ΔE (mJ) satisfies the following formulas (1) and (2).
Expression (1): −0.2 × E _{100 mm / sec} + 100 ≦ ΔE ≦ −0.4 × E _{100 mm / sec} +200
Formula (2): 80 ≦ E _{100 mm / sec} ≦ 360
[In the above formulas (1) and (2), E _{100 mm / sec} (mJ) is a powder fluidity analyzer equipped with a rotary propeller blade, and the propeller blade is the outermost edge of the propeller blade. While rotating at a peripheral speed of 100 mm / sec, the two-component developer powder layer is vertically entered into the two-component developer powder layer in the measurement container filled with the two-component developer. This represents the sum of the rotational torque and the vertical load obtained when the measurement is started from a position 100 mm from the bottom surface and entered to a position 10 mm from the bottom surface. Further, in ΔE (mJ) of the above formula (1), E _{10 mm / sec} (mJ) is a powder flowability analysis apparatus equipped with a rotary propeller blade, and the propeller blade is the top of the propeller blade. While rotating the peripheral speed of the outer edge at 10 mm / sec, the two-component developer powder is allowed to vertically enter the two-component developer powder layer in the measurement container filled with the two-component developer. It represents the sum of rotational torque and vertical load obtained when measurement starts from a position 55 mm from the bottom surface of the body layer and enters a position 2 mm from the bottom surface. ]

  According to the present invention, it is possible to provide a two-component developer that is capable of reducing image density fluctuation during endurance and image quality deterioration of intermittent printing, and further suppressing carrier adhesion and toner scattering and developing properties.

Schematic diagram of powder flowability analyzer (1-a), 23.5 mm diameter blade (1-b), 25 mm × 25 ml split container (1-c). Projected image (2-a) in which reflected electron image of magnetic carrier is visualized, schematic diagram of surface state of magnetic carrier (2-b), state where magnetic carrier is image-processed and magnetic carrier is extracted (2-c) The state (2-d) (drawing substitute photograph) which image-processed the magnetic carrier and extracted the part originating in the metal oxide on the magnetic carrier surface. Projection image (3-a) in which reflected electrons of the magnetic carrier are visualized, projection image (3-b) in which the projection image is visualized at a magnification of 600 times, and a diagram (3) showing a state after pre-processing of image processing of the projection diagram -C) The figure (3-d) which shows the state which extracted the magnetic carrier (drawing substitute photograph). The figure (4-a) which shows the state which excluded the magnetic carrier of the image outer peripheral part from the extracted magnetic carrier, The figure (4-) which shows the state which narrowed down the particle | grains to image-process according to a particle size from the extracted magnetic carrier b) The figure (4-c) of the state which extracted the metal oxide (drawing substitute photograph). The schematic diagram of a surface modification apparatus.

The two-component developer of the present invention is a two-component developer containing at least a magnetic carrier and a toner, the toner contains toner particles containing at least a binder resin and a wax, and the magnetic carrier is magnetic It contains at least core particles and a resin, has a true specific gravity of 2.5 g / cm ³ or more and 4.2 g / cm ³ or less, and the two-component developer is 4 parts by mass or more of toner with respect to 100 parts by mass of the magnetic carrier. It is a two-component developer contained at a ratio of 20 parts by mass or less, and E _{100 mm / sec} (mJ) and E _{100 mm / sec} (mJ) of E, and E _{10 mm / sec} to E _{100 mm / sec.} ΔE (mJ) minus the value satisfies the following formulas (1) and (2).
Expression (1): −0.2 × E _{100 mm / sec} + 100 ≦ ΔE ≦ −0.4 × E _{100 mm / sec} +200
Formula (2): 80 ≦ E _{100 mm / sec} ≦ 360
[In the above formulas (1) and (2), E _{100 mm / sec} (mJ) is a powder fluidity analyzer equipped with a rotary propeller blade, and the propeller blade is the outermost edge of the propeller blade. While rotating at a peripheral speed of 100 mm / sec, the two-component developer powder layer is vertically entered into the two-component developer powder layer in the measurement container filled with the two-component developer. This represents the sum of the rotational torque and the vertical load obtained when the measurement is started from a position 100 mm from the bottom surface and entered to a position 10 mm from the bottom surface. Further, in ΔE (mJ) of the above formula (1), E _{10 mm / sec} (mJ) is a powder flowability analysis apparatus equipped with a rotary propeller blade, and the propeller blade is the top of the propeller blade. While rotating the peripheral speed of the outer edge at 10 mm / sec, the two-component developer powder is allowed to vertically enter the two-component developer powder layer in the measurement container filled with the two-component developer. It represents the sum of rotational torque and vertical load obtained when measurement starts from a position 55 mm from the bottom surface of the body layer and enters a position 2 mm from the bottom surface. ]
Here, ΔE (mJ) is the energy required for stirring (E _{10 mm / sec} ) when the developer is stirred at a low speed at the start of stirring in the developing device, and the stirring speed becomes a specified speed and is stirred at a high speed. The difference from the energy required for stirring (E _{100 mm / sec} ) is shown.
This energy difference (ΔE) satisfies the relationship of −0.2 × E _{100 mm / sec} + 100 ≦ ΔE ≦ −0.4 × E _{100 mm / sec} + 200. Reduction can be made compatible.
Although the mechanism is not clear, the inventors speculate as follows.
In order to suppress image deterioration when intermittent printing is performed, it is necessary to sufficiently frictionally charge the toner. However, in the case of intermittent printing, the toner charge is gradually lost when printing is not performed. This phenomenon is particularly remarkable in a high humidity environment. However, in order to shorten the waiting time for printing by the user, the stirring time of the developer in the developing device at the start of printing is preferably short.
In order to sufficiently triboelectrically charge the toner whose charge has been lost in a short time, it is conceivable as one method to use a developer having a high energy required for stirring in the developing device. However, in the case of such a developer, a large stress is continuously applied to the developer, and as a result, the developer deteriorates during durability and the image density varies. For this reason, conventionally, it has not been possible to achieve both prevention of image degradation in intermittent printing and prevention of density fluctuation during durability.
The inventors have intensively studied the above problem, and selectively increasing the stirring energy when the developer starts to be stirred, that is, when the developer is being stirred at a low speed in the developing device, thereby Solved.
During intermittent printing, the stirring time at a low speed is relatively long. This is because the developing device stops after the printing is completed, and the developing device starts stirring again at the next printing. This is because this frequency is high.
On the other hand, in the case of continuous printing, the developing device is continuously stirred and the time for stirring at a low speed is relatively short. For this reason, in order to suppress the density fluctuation of the image at the time of intermittent printing while suppressing the density fluctuation at the time of durability, it is necessary to selectively increase the energy at the time of low-speed stirring.

Based on this idea, the inventors are stird at a high speed with the energy required for stirring (E _{10 mm / sec} ) and the stirring speed when the developer is stirred at a low speed at the start of stirring in the developing device. The following relational expression was found as an ideal energy relationship of energy (E _{100 mm / sec} ) sometimes required for stirring.
−0.2 × E _{100 mm / sec} + 100 ≦ ΔE ≦ −0.4 × E _{100 mm / sec} +200
[However, ΔE (mJ) is a value obtained by subtracting E _{100 mm / sec} from E _{10 mm / sec} . ]
E _{10 mm / sec} is the two-component developer powder in the container while rotating the peripheral speed of the outermost edge of the propeller blade at _{10 mm / sec} in the powder flowability analyzer (FIG. 1 (1-a)). Measurement is started from a position 55 mm from the bottom surface of the powder layer, and the rotational torque and vertical load obtained when entering the position 2 mm from the bottom surface (blade peripheral speed 10 mm / (also referred to as total energy in sec).
On the other hand, E _{100 mm / sec} is a two-component developer in the container while rotating the peripheral speed of the outermost edge of the propeller blade at _{100 mm / sec} in the powder fluidity analyzer (FIG. 1 (1-a)). The total of rotational torque and vertical load (blade peripheral speed) obtained when the powder layer is entered vertically, measurement is started from a position 100 mm from the bottom surface of the powder layer, and the position is entered 10 mm from the bottom surface. (Also referred to as total energy at 100 mm / sec).
A lower peripheral speed of the outermost edge of the propeller blade can more faithfully reproduce the state when the developer is stirred at a low speed in the developing device. However, if the peripheral speed is less than 10 mm / sec, the reproducibility of the data is lowered because the rotation of the propeller is not stable. For this reason, the inventors considered that it was necessary to perform measurement at a peripheral speed of 10 mm / sec, in which data reliability was obtained and the state in the developing machine could be faithfully reproduced.
In addition, the total energy (E _{100 mm / sec} ) measured at the peripheral speed of 100 mm / sec at the outermost edge of the propeller blade is the energy required for stirring when the stirring speed is the specified speed and the stirring is stable. Show. Specifically, the energy applied to the developer between the developing sleeve and the regulating blade in the developing device.
Usually, the developing sleeve rotates at a speed of 1.2 times to 2.0 times with respect to the developing drum. For this reason, in the case of a main body having a process speed of 200 mm / sec or more, the developing sleeve rotates at a speed of 240 mm / sec or more.
Since the developer is partially blocked by the regulating blade, the developer blocked by the regulating blade is stirred at a speed of 240 mm / sec or more. The energy applied to the developer at this time is expected to be obtained by measuring the peripheral speed of the outermost edge of the propeller blade at 240 mm / sec or more in the powder fluidity analyzer. When measured at high speed, it was not possible to obtain a result that the total energy was correlated with image quality deterioration or density fluctuation. The reason is not clear, but the inventors presume as follows.
When measuring with a powder fluidity analyzer, since the measuring container does not have a lid, the higher the peripheral speed of the propeller blade, the more the developer escapes to the upper side of the measuring container. When the amount of the developer that escapes in this way increases, the energy applied to the developer decreases. On the other hand, in the developing device, a large energy is applied because of the form close to the closed system.
For this reason, as a result of intensive studies, the inventors measured the effect at a peripheral speed of 100 mm / sec or less at the outermost edge of the propeller blade, so that there was little developer escaping on the measurement container, and the effect of the developer escaping. It was found that the amount of developer can be reduced and the state of the developer in the developing machine can be reproduced.
Further, when the blade peripheral speed is slower than 100 mm / sec, the developer stirring speed becomes too low, and the state of the main body at a process speed of 200 mm / sec or more cannot be reproduced.

By setting E _{100 mm / sec} and ΔE in the above ranges, it is possible to reduce image quality degradation and improve image density fluctuation when intermittent printing is performed at a high process speed.
When ΔE is smaller than [−0.2 × E _{100 mm / sec} + 100], the density fluctuation of the image increases when intermittent printing is performed. The reason for this is not clear, but the inventors speculate that the energy required for stirring at low speed is small, and that the toner is developed before it has sufficient charge.
On the other hand, when ΔE is larger than [−0.4 × E _{100 mm / sec} + 200], image quality deteriorates when intermittent printing is performed. The reason for this is not clear, but the inventors presume that the energy required for stirring at low speed stirring is too large and the developer deteriorates at low speed stirring.
Further, by setting E _{100 mm / sec} (mJ) in the range of 80 ≦ E _{100 mm / sec} ≦ 360, preferably 120 ≦ E _{100 mm / sec} ≦ 300, toner scattering prevention and density stability during durability can be achieved. Can be improved.
When E _{100 mm / sec} (mJ) is less than 80, toner scattering in the developing unit increases and the member is contaminated.
On the other hand, when E _{100 mm / sec} (mJ) is larger than 360, a large energy is required when the developer is stirred in the developing device. For this reason, regardless of the presence or absence of intermittent printing, excessive stress is applied to the developer, and the image density fluctuates during durability.

Next, specific measurement methods for E _{100 mm / sec} (mJ) and E _{10 mm / sec} (mJ) will be described. In the present invention, E _{100 mm / sec} (mJ) and E _{10 mm / s
For} the measurement of _ec (mJ), a powder fluidity analyzer (powder rheometer FT-4, manufactured by Freeman Technology) (hereinafter also referred to as “FT-4”) equipped with a rotary blade was used.
The principle of the device is to move a rotating blade in a powder sample and cause a constant pattern of flow. The particles in the powder sample will flow when the blade is in close proximity and will rest again when it passes. The energy required for the blade to move through the powder is measured, and from this value various fluidity indices are calculated. Since the blade is a propeller type and moves in the upward or downward direction at the same time as rotating, the tip draws a spiral. The angle and speed of the spiral path of the blade can be adjusted by changing the rotational speed and the vertical movement. When the blade moves along a clockwise spiral path with respect to the powder layer surface, there is an action of mixing the powder uniformly. Conversely, when the blade moves along a counterclockwise spiral path with respect to the powder layer surface, the blade receives resistance from the powder. (Fig. 1 (1-a))
Specifically, the measurement was performed by the following operation. In all the operations, a propeller type blade used exclusively for FT-4 measurement [23.5 mm diameter blade (model number: C415)] (see FIG. 1 (1-b), hereinafter abbreviated as “blade”) was used. .
First, toner that is left in a 23 ° C./60% RH environment for 3 days in a dedicated FT-4 measurement [25 mm × 25 ml split container (model number: 2015)] (see FIG. 1 (1-c), hereinafter abbreviated as container). Was put into a full cup (about 30 cc) to form a two-component developer powder layer.
(1) Conditioning operation (a): The peripheral speed of the blade (the peripheral speed of the outermost edge of the blade) was set to 100 (mm / sec). The vertical approach speed to the powder layer is such that the angle formed by the locus drawn by the outermost edge of the moving blade and the surface of the powder layer (hereinafter “blade locus angle”) is 5 (deg). did. The blade enters from the surface of the powder layer to the position of 5 mm from the bottom surface of the two-component developer powder layer in the clockwise direction with respect to the powder layer surface (the direction in which the powder layer is loosened by the rotation of the blade). I let you. After that, the peripheral speed of the blade is 40 (mm / sec) and the vertical approach speed to the powder layer is rotated clockwise with respect to the powder layer surface at a speed at which the blade trajectory angle is 2 (deg). In the direction, the blade was advanced to a position 2 mm from the bottom of the two-component developer powder layer. Thereafter, the toner is rotated clockwise with respect to the powder layer surface at a blade peripheral speed of 40 (mm / sec) and an extraction speed from the powder layer of 5 (deg). The blade was moved to a position 55 mm from the bottom of the powder layer and extracted. When the extraction was completed, the two-component developer adhering to the blade was wiped off by rotating the blade alternately in small clockwise and counterclockwise directions.
(B): A series of the above operations (1) to (a) is performed five times to remove air entrained in the two-component developer powder layer, thereby stabilizing the two-component developer powder. Made a layer.
-Split operation The same volume (25 ml) is obtained by scraping off the two-component developer powder layer at the split portion of the above-mentioned container (Fig. 1 (1-c)) and removing the two-component developer above the powder layer. A two-component developer powder layer was formed.
Measurement operation (a): The same operation as the above (1)-(a) was performed once.
(B): Next, the peripheral speed of the blade was set to 100 (mm / sec), and the approach speed in the vertical direction to the powder layer was set to a speed at which the blade trajectory angle was 5 (deg). The blade was advanced from the bottom surface of the toner powder layer to a position 5 mm in the counterclockwise rotation direction (direction in which the powder layer was pushed in by rotation of the blade) with respect to the powder layer surface. After that, the peripheral speed of the blade is 40 (mm / sec) and the vertical approach speed to the powder layer is rotated clockwise with respect to the powder layer surface at a speed at which the blade trajectory angle is 2 (deg). In the direction, the blade was advanced to the position of 2 mm from the bottom surface of the powder layer. Thereafter, the peripheral speed of the blade is 40 (mm / sec), the vertical extraction speed from the powder layer is a speed at which the blade locus angle is 5 (deg), and the rotation direction is clockwise with respect to the powder layer surface. Then, the blade was extracted from the bottom surface of the powder layer to a position of 55 mm. When the extraction was completed, the two-component developer adhering to the blade was wiped off by rotating the blade alternately in small clockwise and counterclockwise directions.
(C): The above series of operations (b) was repeated 7 times.
Rotational torque obtained when the blade is moved from the bottom surface of the two-component developer powder layer to a position of 100 mm to 10 mm at the seventh blade peripheral speed 100 (mm / sec) in the operation of (c) above. And the sum of the vertical loads was [E _{100 mm / sec} ].
(D): Similar to (3)-(c), measurement was performed with the peripheral speed sequentially reduced to 70 (mm / sec), 40 (mm / sec), and 10 (mm / sec). The measurement was started from a position 55 mm from the bottom surface of the toner powder layer at a peripheral speed of 10 (mm / sec), and the sum of the rotational torque and the vertical load obtained when entering the position 2 mm from the bottom surface was [E _{10 mm. / Sec} ].
And what subtracted _{E100mm / sec} from _{E10mm / sec} was set to (DELTA) E (mJ).

The ΔE and E _{100 mm / sec} can be adjusted within the range of the present invention by controlling the structure or physical properties of the magnetic carrier and the toner.
Regarding the magnetic carrier, first, the true specific gravity is 2.5 g / cm ³ or more and 4.2 g / cm ³ or less. When the true specific gravity is less than 2.5 g / cm ³ , the amount of the magnetic component is reduced. As a result, the magnetic carrier becomes difficult to be held by the developing sleeve, and the magnetic carrier adheres on the drum. When the true specific gravity of the magnetic carrier is greater than 4.2 g / cm ³ , the resistance during stirring of the two-component developer is increased, and E _{100 mm / sec} is greater than the above range.
Next, on the surface of the magnetic carrier, when the developer is stirred at a low speed at the start of stirring in the developing unit, the part involved in the energy required for stirring, and when the stirring speed becomes a specified speed and stirring is performed at a high speed It is preferable to have both of the parts involved in the energy required for.
Specifically, it is preferable that irregularities exist on the surface of the magnetic carrier and that the surface states of the convex portions and the concave portions are made different.
In the case of such a magnetic carrier, since the stirring speed is low during low-speed stirring, both the convex portion and the concave portion are involved in the stirring energy. On the other hand, when stirring at a specified speed, the concave portions are hardly in contact with each other, and only the convex portions are involved in the stirring energy.
For this reason, in the case of a magnetic carrier in which the surface state of the convex portion and the concave portion is changed, the stirring energy at the time of low speed stirring and high speed stirring can be controlled.
Specifically, it is preferable to use a magnetic carrier in which a metal oxide portion having a low resistance during stirring is present in the convex portion and a resin portion having a large resistance during stirring is present in the concave portion.
In addition, E _{100 mm / sec} and ΔE can be adjusted depending on the particle size of the carrier, the type of resin used, and the like.
As for the toner, the stirring energy can be controlled by the shape (average circularity), particle size, and particle size distribution of the toner.
In addition, no matter which method is used, if E _{100 mm / sec} and ΔE are within the scope of the present invention, the effect of the present invention is manifested.

The degree of unevenness of the magnetic carrier for adjusting E _{100 mm / sec} and ΔE within the range of the present invention is set to L1 as the perimeter of the projected image of the magnetic carrier taken with a scanning electron microscope (SEM). When the length of the envelope is L2, the envelope degree {(L1-L2) / L2} × 100 is preferably 0.5 or more and 10.0 or less, and more preferably 1.0 or more and 5.0 or less.
The mechanism is not clear, but the inventors presume as follows.
When the developer is stirred, if the stirring speed is low, it seems that other magnetic carriers and toners pass along the periphery of the magnetic carrier particles. On the other hand, when agitated at a high speed, it seems that magnetic carrier particles and toner pass in a place near the envelope of the carrier particles.
For this reason, the stirring state of the developer at the time of low speed stirring and high speed stirring can be changed by controlling the degree of unevenness of the carrier so that the perimeter and the envelope are shifted. Specifically, when the envelope is 0.5 or more and 10.0 or less, E _{100 mm / sec} and ΔE can be controlled within the range of the present invention. If the degree of envelope is less than 0.5, the unevenness is small, so that the stirring energy becomes large during high-speed stirring. On the other hand, if the envelope degree exceeds 10.0, the unevenness is large, so that the durability as a magnetic carrier is lowered, the carrier is damaged during printing, and carrier adhesion may occur.

The magnetic carrier used in the present invention will be described in detail.
The magnetic carrier of the present invention is a magnetic carrier containing at least a magnetic core particle containing a metal oxide and a resin. In the projected image of reflected electrons obtained when the acceleration voltage is 2.0 kV using a scanning electron microscope, the area of the portion derived from the metal oxide is smaller than the projected area of the magnetic carrier. 0.5 area% or more and 8.0 area% or less, and the area of the portion derived from the metal oxide of 6.672 μm ² or more is 10 area% with respect to the total area of the portion derived from the metal oxide. The following is preferable in order to adjust the ΔE to the range defined in the present invention.
The inventors believe that the portion derived from the metal oxide has lower adhesion to the toner than the resin portion and can reduce the stirring energy of the developer.
In the projected image of reflected electrons obtained when the acceleration voltage is 2.0 kV, when the area of the portion derived from the metal oxide is smaller than 0.5 area% with respect to the projected image area of the magnetic carrier, Since the area of the portion derived from the metal oxide present on the carrier surface is small, the stirring energy of the developer cannot be lowered during high-speed stirring, and the developer tends to deteriorate, and the image quality tends to deteriorate during durability.
On the other hand, when the area is larger than 8.0 area% with respect to the projected image area of the magnetic carrier, since there are many portions derived from the metal oxide, the stirring energy during low-speed stirring is low, and as a result, the image is displayed during intermittent printing. The concentration tends to fluctuate.
In addition, the inventors have 200 pixel (5.560 μm ² ), 220 pixel (6.116 μm ² ), 240 pixel (6.672 μm ² )... And the ratio of the exposed metal area and the leakage of charge every 20 pixels. The relationship was examined. As a result, it has been found that charge leakage occurs remarkably in a portion where the area derived from the metal oxide is 6.672 μm ² or more. 6.672 μm ² or more is a size of 240 pixels in the observation of the reflected electron projection image with a scanning electron microscope. (The area of 1 pixel is 0.0278 μm ² )
The inventors infer the reason as follows.
A covering resin exists around the portion derived from the metal oxide. The resin has a certain thickness, and the thickness suppresses the contact of the portion derived from the metal oxide, so that leakage is hardly generated. On the other hand, when the portion derived from the metal oxide is 6.672 μm ² or more, there can be a portion that contributes to the contact without being influenced by the surrounding resin. For this reason, when the carriers come into contact with each other, it is considered that charges leak from the portion.
By making this area 10 area% or less with respect to the total area of the portion derived from the metal oxide, it is possible to suppress a decrease in charge amount during long-term use and to suppress fluctuations in image density.

Note that the portion derived from the metal oxide on the projected image of the reflected electrons photographed under a predetermined acceleration voltage using the scanning electron microscope is mainly an image obtained by visualizing the reflected electrons (FIG. 2 (2- In (a)), it refers to a portion that is observed as a portion with high luminance (which appears white and bright on the image). The scanning electron microscope is a device that visualizes the surface and composition information of a sample by irradiating the sample with an accelerated electron beam and detecting secondary electrons and reflected electrons emitted from the sample. In observation with a scanning electron microscope, it is known that the amount of reflected electrons emitted is larger for heavy elements. For example, in the case of a sample in which an organic compound and iron are distributed on a plane, the amount of reflected electrons emitted from the iron is large, so that the iron portion appears bright (high brightness, white) on the image. On the other hand, since the amount of reflected electrons from the organic compound composed of light elements is not large, it appears dark (low brightness and black) on the image.
On the surface of the magnetic carrier, a resin portion that is an organic compound and a magnetic core portion that is a metal oxide are distributed on the surface of the magnetic carrier. In the reflected electron image of the magnetic carrier, the metal oxide portion is bright and the resin portion is dark, and a projection image having a large contrast difference on the image is obtained. FIG. 2 (2-b) schematically shows the distribution of the metal oxide portion and the resin portion on the surface of the magnetic carrier in FIG. 2 (2-a), where the white portion is derived from the metal oxide. The black part corresponds to the resin part. In the present invention, first, a magnetic carrier is extracted from the projected image of the magnetic carrier in FIG. 2 (2-a), and the projected image area of the magnetic carrier is obtained. The part that is white in FIG. 2 (2-c) indicates the part extracted as the magnetic carrier part from the projected image in FIG. 2 (2-a). Subsequently, a metal oxide portion is extracted from the projected image of FIG. 2 (2-a) (see FIG. 2 (2-d)), and in FIG. Represents a part. The projected image area of the magnetic carrier and the area of the metal oxide portion are obtained by image processing. Next, the ratio of the area of the metal oxide portion to the projected image area of the magnetic carrier and the area distribution of the metal oxide portion are calculated. Details of observation conditions, imaging conditions, and image procedures with a scanning electron microscope will be described later. Moreover, it can also be confirmed by the elemental analyzer attached to the electron microscope that the portion that shines white is actually a metal oxide.

There are various methods for controlling the presence of the magnetic core portion on the surface of the magnetic carrier (that is, the area of the portion derived from the metal oxide), such as the composition of the coating resin contained in the magnetic core particles, the amount of the coating resin, and the coating method. Can be adjusted in a way. In addition, it is preferable to selectively introduce the resin into the concave portion during coating with the resin.
Specifically, it is preferable to control the presence state of the magnetic core portion by performing coating treatment in multiple times with coating resin solutions having different solid content concentrations.

Examples of the magnetic core particles include metal particles such as surface oxidized or unoxidized iron, lithium, calcium, magnesium, nickel, copper, zinc, cobalt, manganese, chromium, rare earth, alloy particles thereof, oxide particles, and the like. A ferrite etc. can be illustrated suitably.
The magnetic carrier is preferably a magnetic carrier in which the magnetic core particles are filled with a resin and / or a coated magnetic carrier in which the surface of the magnetic core particles is coated with a resin. As a resin coating method, a method of adhering a coating solution prepared by dissolving or suspending a coating material such as resin in a solvent to the surface of the magnetic core particles, a method of mixing the magnetic core particles and the coating material in powder form A conventionally known method can be applied.
The magnetic core particles are preferably porous magnetic core particles described below, and more preferably porous ferrite particles.
Here, as the above-mentioned magnetic carrier, a porous magnetic core particle containing a resin is particularly preferable because the magnetic carrier surface can be provided with irregularities having an envelope degree of 0.5 or more and 10 or less.
The porous magnetic core particles can be produced by the following process.
Examples of the material for the porous magnetic core particles include the following. 1) Iron powder with oxidized surface 2) Unoxidized iron powder 3) Metal particles such as lithium, calcium, magnesium, nickel, copper, zinc, cobalt, manganese, chromium and rare earth elements 4) Iron, lithium Alloy particles of metals such as calcium, magnesium, nickel, copper, zinc, cobalt, manganese, chromium and rare earth elements, or oxide particles containing these elements, 5) magnetite particles or ferrite particles.
A ferrite particle is a sintered body represented by the following formula.
(M1 ₂ O) _u (M ₂ O) _v (M _{3 2} O ₃ ) _w (M ₄ O ₂ ) _x (M 5 ₂ O ₅ ) _y (Fe ₂ O ₃ ) _z
(In the formula, M1 is monovalent, M2 is divalent, M3 is trivalent, M4 is tetravalent, M5 is pentavalent metal, and u, v, w, x, and x when u + v + w + x + y + z = 1.0. y is 0 ≦ (u, v, w, x, y) ≦ 0.8, respectively, and z is 0.2 <z <1.0.)
In the above formula, M1 to M5 are at least Li, Fe, Zn, Ni, Mn, Mg, Co, Cu, Ba, Sr, Ca, Si, V, Bi, In, Ta, Zr, B,
1 selected from the group consisting of Mo, Na, Sn, Ti, Cr, Al, Sc, Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu Represents more than one kind of metal element.
For example, magnetic Li-based ferrite (for example, (Li ₂ O) _a (Fe ₂ O ₃ ) _b (0.0 <a <0.4, 0.6 ≦ b <1.0, a + b = 1)), Mn ferrite (for example, (MnO) _a (Fe ₂ O ₃ ) _b (0.0 <a <0.5, 0.5 ≦ b <1.0, a + b = 1)), Mn—Mg ferrite ( For example, (MnO) _a (MgO) _b (Fe ₂ O ₃ ) _c (0.0 <a <0.5, 0.0 <b <0.5, 0.5 ≦ c <1.0, a + b + c = 1)), Mn—Mg—Sr ferrite (for example, (MnO) _a (MgO) _b (SrO) _c (Fe ₂ O ₃ ) _d (0.0 <a <0.5, 0.0 <b < 0.5,0.0 <c <0.5,0.5 ≦ d < 1.0, a + b + c + d = 1), Cu-Zn ferrite (e.g., _(CuO) a (Zn _{) B (Fe 2 O 3)} c (0.0 <a <0.5,0.0 <b <0.5,0.5 ≦ c <1.0, a + b + c = 1) there is. The above Ferrite indicates the main element, and includes those containing other trace metals.
From the viewpoint of easy control of crystal growth rate, Mn-based ferrite, Mn-Mg-based ferrite, and Mn-Mg-Sr-based ferrite containing Mn element are preferable.

Below, the manufacturing process in the case of using a ferrite particle as a porous magnetic carrier particle is demonstrated in detail.
<Process 1 (weighing / mixing process)>
The ferrite raw materials are weighed and mixed.
Examples of the ferrite raw material include the following. Li, Fe, Zn, Ni, Mn, Mg, Co, Cu, Ba, Sr, Y, Ca, Si, V, Bi, In, Ta, Zr, B, Mo, Na, Sn, Ti, Cr, Al, Rare earth metal particles, oxides, hydroxides, oxalates, carbonates.
Examples of the mixing apparatus include the following. Ball mill, planetary mill, Giotto mill, vibration mill. A ball mill is particularly preferable from the viewpoint of mixing properties.
Specifically, a weighed ferrite raw material and balls are placed in a ball mill, and pulverized and mixed for 0.1 to 20.0 hours.
<Step 2 (temporary firing step)>
The ferrite raw material thus pulverized and mixed is calcined in the atmosphere at a firing temperature of 700 ° C. or higher and 1000 ° C. or lower for 0.5 hour or more and 5.0 hours or less to form a ferrite. For firing, for example, the following furnace is used. Burner type incinerator, rotary type incinerator, 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. Examples include the following. Crusher, hammer mill, ball mill, bead mill, planetary mill, Giotto mill.
In order to make the ferrite pulverized product have a desired particle size, for example, it is preferable to control the material, particle size, and operation time of the balls and beads used in the ball mill and bead mill. Specifically, in order to reduce the particle size of the calcined ferrite slurry, a ball having a high specific gravity may be used or the pulverization time may be increased. Further, in order to widen the particle size distribution of the calcined ferrite, it can be obtained by using balls and beads having a high specific gravity and shortening the grinding time. In addition, by mixing a plurality of calcined ferrites having different particle diameters, a calcined ferrite having a wide distribution can be obtained.
In addition, ball mills and bead mills have a high grinding efficiency when a wet method is used rather than a dry method, and a pulverized product does not rise in the mill. For this reason, the wet type is more preferable than the dry type.
<Process 4 (granulation process)>
Water, a binder and, if necessary, a pore adjuster are added to the pulverized product of calcined ferrite. Examples of the pore adjuster include a foaming agent and resin fine particles. Examples of the foaming agent include sodium hydrogen carbonate, potassium hydrogen carbonate, lithium hydrogen carbonate, ammonium hydrogen carbonate, sodium carbonate, potassium carbonate, lithium carbonate, and ammonium carbonate. Examples of resin fine particles include polyester, polystyrene, styrene-vinyltoluene copolymer, styrene-vinylnaphthalene copolymer, styrene-acrylic acid ester copolymer, styrene-methacrylic acid ester copolymer, and styrene-α-chloromethacrylic acid. Styrene copolymers such as acid methyl copolymer, styrene-acrylonitrile copolymer, styrene-vinyl methyl ketone copolymer, styrene-butadiene copolymer, styrene-isoprene copolymer, styrene-acrylonitrile-indene copolymer Polyvinyl chloride, phenolic resin, modified phenolic resin, maleic resin, acrylic resin, methacrylic resin, polyvinyl acetate, silicone resin; aliphatic polyhydric alcohol, aliphatic dicarboxylic acid, aromatic dicarboxylic acid, aromatic dialcohol and Polyester resin having monomers selected from phenols as structural units; polyurethane resin, polyamide resin, polyvinyl butyral, terpene resin, coumarone indene resin, petroleum resin, hybrid resin having polyester unit and vinyl polymer unit 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 in consideration of water contained in the ferrite slurry.
The obtained ferrite slurry is dried and granulated using a spray dryer in a heated atmosphere of 100 ° C. or higher and 200 ° C. or lower. The spray dryer is not particularly limited as long as a desired porous magnetic core particle size can be obtained. For example, a spray dryer can be used.
<Step 5 (main firing step)>
Next, the granulated product is fired at 800 ° C. to 1400 ° C. for 1 hour to 24 hours.
By raising the firing temperature and lengthening the firing time, the firing of the porous magnetic core particles proceeds, and as a result, the pore diameter is small and the number of pores is also reduced. Further, by controlling the firing atmosphere, the breakdown field strength can be controlled within a preferable range. For example, the breakdown field strength of the porous magnetic core particles can be lowered by lowering the oxygen concentration or reducing atmosphere (in the presence of hydrogen).
<Process 6 (sorting process)>
After pulverizing the particles fired as described above, coarse particles and fine particles may be removed by classification or sieving as necessary.
The volume distribution reference 50% particle diameter (D50) of the magnetic core particles is more preferably 18.0 μm or more and 68.0 μm or less in order to suppress the carrier adhesion to the image and the roughness.

As described above, the magnetic carrier is preferably a magnetic carrier in which resin is filled in at least a part of the voids of the porous magnetic core particles.
Porous magnetic core particles may have low physical strength depending on the internal void volume, and in order to increase physical strength as a magnetic carrier, at least part of the voids of the porous magnetic core particles are filled with resin. It is preferable to carry out. The amount of the resin filled in the porous magnetic core particles is preferably 6% by mass or more and 25% by mass or less with respect to the porous magnetic core particles. If there is little variation in the resin content for each magnetic carrier, the resin is filled only in the voids near the surface of the porous magnetic core particles and the voids remain inside even if the resin is filled only in a part of the inner voids. Or the internal voids may be completely filled with resin.
The method for filling the voids in the porous magnetic core particles with the resin is not particularly limited, but the resin solution is impregnated with the porous magnetic core particles by a coating method such as dipping, spraying, brushing, and fluidized bed. And then a method of volatilizing the solvent. In particular, in order to leave a metal oxide-derived portion on the surface of the magnetic carrier, a method of filling a void in the porous magnetic core particles with a resin solution in which a resin and a solvent are mixed is preferable. As a method for filling the voids in the porous magnetic core particles with the resin, a method in which the resin is diluted with a solvent and added to the voids in the porous magnetic core particles can be employed. The solvent used here should just be what can melt | dissolve resin. When the resin is soluble in an organic solvent, examples of the organic solvent include toluene, xylene, cellosolve butyl acetate, methyl ethyl ketone, methyl isobutyl ketone, and methanol. In the case of a water-soluble resin or an emulsion type resin, water may be used as a solvent.
The resin that fills the voids of the porous magnetic core particles is not particularly limited, and either a thermoplastic resin or a thermosetting resin may be used. It is preferable that the resin has a high affinity for the porous magnetic core particles. When a resin having a high affinity is used, the surface of the porous magnetic core particles is simultaneously filled with the resin in the voids of the porous magnetic core particles. It becomes easy to cover with resin.
As the resin to be filled, examples of the thermoplastic resin include the following. Polystyrene, polymethyl methacrylate, styrene-acrylic resin; styrene-butadiene copolymer, ethylene-vinyl acetate copolymer, polyvinyl chloride, polyvinyl acetate, polyvinylidene fluoride resin, fluorocarbon resin, perfluorocarbon resin, polyvinylpyrrolidone, petroleum Resin, novolak resin, saturated alkyl polyester resin, polyethylene terephthalate, polybutylene terephthalate, polyarylate, polyamide resin, polyacetal resin, polycarbonate resin, polyethersulfone resin, polysulfone resin, polyphenylene sulfide resin, polyetherketone resin.
Moreover, the following are mentioned as said thermosetting resin. Phenolic resin, modified phenolic resin, maleic resin, alkyd resin, epoxy resin, unsaturated polyester obtained by polycondensation of maleic anhydride, terephthalic acid and polyhydric alcohol, urea resin, melamine resin, urea-melamine resin, xylene resin , Toluene resin, guanamine resin, melamine-guanamine resin, acetoguanamine resin, gliptal resin, furan resin, silicone resin, polyimide, polyamideimide resin, polyetherimide resin, polyurethane resin.
Among the above resins, a thermosetting resin is preferable because the strength of the magnetic carrier can be increased. Among these, a silicone resin is more preferable because ΔE (difference in stirring energy) of the developer can be easily controlled within the range of the present invention.
Specific examples of the silicone resin include the following. For straight silicone resins, KR271, KR255, KR152 manufactured by Shin-Etsu Chemical Co., Ltd., SR2400, SR2405, SR2410, SR2411 manufactured by Toray Dow Corning Co., Ltd. are used. Among the modified silicone resins, KR206 (alkyd modified), KR5208 (acrylic modified), ES1001N (epoxy modified), KR305 (urethane modified) manufactured by Shin-Etsu Chemical, SR2115 (epoxy modified), SR2110 (alkyd) manufactured by Toray Dow Corning Co., Ltd. Denatured).
The amount of the resin solid content in the resin solution is preferably 1% by mass or more and 50% by mass or less, and more preferably 1% by mass or more and 30% by mass or less. When a resin solution having a resin amount larger than 50% by mass is used, the resin solution is difficult to uniformly penetrate into the voids of the porous magnetic core particles because of its high viscosity. In addition, if the amount is less than 1% by mass, the amount of the resin is small, and the adhesive force of the resin to the porous magnetic core particles may be low.

Even if the porous magnetic core particle is simply filled with a resin, it can be used as a magnetic carrier. In that case, in order to improve the charge imparting property to the toner, it is preferable that the resin solution is filled in advance with a charge control agent, a charge control resin, or the like contained therein.
In addition, the magnetic carrier used in the present invention is such that after the resin is filled in the voids of the porous magnetic core particles, the surface of the magnetic carrier is coated with the resin. And more preferable in adjusting the area distribution.
Covering the surface of the magnetic carrier with a resin is preferable because the ratio and area of the metal oxide-derived portion can be more precisely controlled. In addition, the surface of the magnetic carrier is coated with a resin in order to control the releasability of the toner from the surface of the magnetic carrier, the contamination of the toner and external additives on the surface of the magnetic carrier, the ability to impart charge to the toner and the magnetic carrier resistance. It is preferable to do.
The method for coating the surface of the magnetic core particles with a resin is not particularly limited, and examples thereof include a coating method such as a dipping method, a spray method, a brush coating method, a dry method, and a fluidized bed. Among these, a dipping method capable of appropriately exposing the magnetic core particles to the surface is more preferable. The amount of the resin to be coated is preferably 0.1 parts by mass or more and 5.0 parts by mass or less with respect to 100 parts by mass of the magnetic core particles because the metal oxide portion can be appropriately exposed on the surface. . As the resin to be coated, the resin used for filling can be used.

The toner used in the present invention is a toner containing toner particles containing at least a binder resin and a wax. The binder resin is not particularly limited, and conventionally known binder resins can be used. Specific examples include the following. Polyester, polystyrene; polymer of styrene derivatives such as poly-p-chlorostyrene and polyvinyltoluene; styrene-p-chlorostyrene copolymer, styrene-vinyltoluene copolymer, styrene-vinylnaphthalene copolymer, styrene-acrylic Acid ester copolymer, styrene-methacrylic acid ester copolymer, styrene-α-chloromethyl methacrylate copolymer, styrene-acrylonitrile copolymer, styrene-vinyl methyl ketone copolymer, styrene-butadiene copolymer, Styrene copolymers such as styrene-isoprene copolymer, styrene-acrylonitrile-indene copolymer; polyvinyl chloride, phenol resin, modified phenol resin, maleic resin, acrylic resin, methacrylic resin, polyvinyl acetate, silicone resin; Polyester resin having as a structural unit a monomer selected from aliphatic polyhydric alcohol, aliphatic dicarboxylic acid, aromatic dicarboxylic acid, aromatic dialcohol and diphenol; polyurethane resin, polyamide resin, polyvinyl butyral, terpene resin, A hybrid resin having coumarone indene resin, petroleum resin, polyester unit and vinyl polymer unit. The wax is not particularly limited, and a conventionally known wax can be used. Specific examples include the following. Low molecular weight polyethylene, low molecular weight polypropylene, alkylene copolymer, hydrocarbon wax such as microcrystalline wax, paraffin wax, Fischer-Tropsch wax; oxide of hydrocarbon wax such as oxidized polyethylene wax or block copolymer thereof Waxes mainly composed of fatty acid esters such as carnauba wax, behenic acid behenyl ester wax, and montanic acid ester wax; fatty acid esters such as deoxidized carnauba wax that have been partially or fully deoxidized. Furthermore, the toner used in the present invention may contain a conventionally known colorant, charge control agent, inorganic fine powder, and the like, if necessary.
On the other hand, the method for producing the toner particles and toner is not particularly limited, and a conventionally known production method can be used.
The toner used in the present invention has an equivalent circle diameter of 1.98 μm or more measured by a flow type particle image measuring apparatus having a toner image processing resolution of 512 × 512 pixels (0.37 μm × 0.37 μm per pixel). The average circularity analyzed by dividing a particle of 200.00 μm or less into 800 in the range of circularity of 0.200 or more and 1.000 or less is 0.950 or more and 0.990 or less, and the equivalent circle diameter is 0.00. 25.0% by number or less of particles of 0.50 μm or more and 1.98 μm or less with respect to all particles of 50 μm or more and 200.00 μm or less can suppress image deterioration during durability while improving developability. ,preferable.
When the average circularity is smaller than 0.950, the adhesion area between the toner and the magnetic carrier is increased, and as a result, the adhesion between the toner and the carrier is increased and the developability may be lowered.
On the other hand, when the average circularity is larger than 0.990, the adhesion between the toner and the magnetic carrier becomes too small, and the toner scattering may deteriorate.

Further, in the toner used in the present invention, when the above-mentioned equivalent circle diameter of 0.50 μm or more and 1.98 μm or less is larger than 25.0% by number, the particles of 0.50 μm or more and 1.98 μm or less are used as the magnetic carrier during durability. It may adhere to the metal oxide portion, increase the stirring energy during high-speed stirring, and may change the concentration during durability.
As a method for controlling the average circularity of the toner and the number% of particles having an equivalent circle diameter of 0.50 μm or more and 1.98 μm or less within the above range, a method of classification or a modification treatment of the surface of the toner particles using hot air is used. The method of doing is mentioned.
Specifically, classifiers such as inertial class elbow jet (manufactured by Nippon Steel & Mining), centrifugal classifier turboplex (manufactured by Hosokawa Micron), TSP separator (manufactured by Hosokawa Micron), Faculty (manufactured by Hosokawa Micron) Or a sieving machine, particles of 0.50 μm or more and 1.98 μm or less can be removed.
Further, the average circularity can be controlled while performing the surface modification treatment of the toner particles using hot air. Further, in the case of surface modification treatment of toner particles using hot air, particles of 0.50 μm or more and 1.98 μm or less are firmly held on the toner surface during the surface modification treatment. As a result, it is possible to control the particles of 0.50 μm or more and 1.98 μm or less to 25.0% by number or less.
The method for modifying the surface of the toner particles using the hot air is not particularly limited as long as the surface treatment of the toner particles is performed using hot air. For example, a method using a device such as a hybridization system (manufactured by Nara Machinery Co., Ltd.), a mechano-fusion system (manufactured by Hosokawa Micron Corporation), a faculty (manufactured by Hosokawa Micron Corporation), or Meteoleinbo MR Type (manufactured by Nippon Pneumatic Co., Ltd.) can be mentioned. Here, either a method of performing surface treatment with hot air using a surface treatment apparatus and subsequently classifying, or a method of performing surface treatment with hot air using a surface treatment apparatus after pre-classification is used. May be.
An outline of a method for modifying the surface of toner particles with hot air using the above-described surface treatment apparatus will be described with reference to FIG. 5, but is not limited thereto. Specifically, toner particles are obtained by a conventionally known method and then supplied to the surface treatment apparatus. The toner particles (114) supplied from the toner particle supply port (100) are accelerated by the injection air injected from the high-pressure air supply nozzle (115) and travel toward the airflow injection member (102) below the injection air. Diffusion air is ejected from the airflow ejecting member (102), and the toner particles are diffused outward by the diffusion air. At this time, the toner diffusion state can be controlled by adjusting the flow rate of the injection air and the flow rate of the diffusion air. Further, for the purpose of preventing fusion of the toner particles, a cooling jacket (106) is provided on the outer periphery of the toner particle supply port (100), the outer periphery of the surface treatment apparatus, and the outer periphery of the transfer pipe (116). In addition, it is preferable to pass cooling water (preferably antifreeze such as ethylene glycol) through the cooling jacket. On the other hand, the toner particles diffused by the diffusion air are treated on the surface of the toner particles by the hot air supplied from the hot air supply port (101). At this time, the temperature of the hot air is preferably 100 ° C. or higher and 450 ° C. or lower, and more preferably 100 ° C. or higher and 400 ° C. or lower. When the temperature of the hot air is less than 100 ° C., the surface roughness of the toner particle surface may vary. In addition, when the temperature exceeds 450 ° C., toner particles may be coalesced due to excessive progress of the molten state, and toner particles may be coarsened or fused.
The toner particles whose surface has been treated with hot air are cooled by cold air supplied from a cold air supply port (103) provided on the outer periphery of the upper part of the apparatus. At this time, cold air may be introduced from the second cold air supply port (104) provided on the side surface of the main body of the apparatus for the purpose of controlling the temperature distribution in the apparatus and controlling the surface state of the toner particles. The outlet of the second cold air supply port (104) can use a slit shape, a louver shape, a perforated plate shape, a mesh shape, etc., the introduction direction is horizontal to the center direction, and the direction along the apparatus wall surface depends on the purpose. Selectable.
At this time, the temperature in the cold air supply port and the second cold air supply port is preferably −50 ° C. or higher and 10 ° C. or lower, and more preferably −40 ° C. or higher and 8 ° C. or lower. The cold air is preferably dehumidified cold air. Specifically, the absolute water content is preferably 5 g / m ³ or less. More preferably, it is 3 g / m ³ or less.
When these cold air temperatures are less than −50 ° C., the temperature in the apparatus is too low, and the heat treatment that is the original purpose is not sufficiently performed, and the toner particles may not be spheroidized. When the temperature exceeds 10 ° C., the control of the hot air zone in the apparatus becomes insufficient, and the wax may be segregated excessively on the toner surface during the surface treatment.
Thereafter, the cooled toner particles are sucked by a blower and collected by a cyclone or the like through a transfer pipe (116).

  The two-component developer of the present invention contains toner in a proportion of 4 parts by mass or more and 20 parts by mass or less with respect to 100 parts by mass of the magnetic carrier, from the viewpoint of suppressing image density fluctuation and image quality deterioration. Component developer. Preferably, the two-component developer contains toner in a proportion of 4 parts by mass or more and 18 parts by mass or less with respect to 100 parts by mass of the magnetic carrier. When the amount of toner is less than 4 parts by mass, when images having a high image area ratio are continuously printed, the toner in the developing device may be insufficient and the image density may be lowered. On the other hand, when the amount of toner is more than 20 parts by mass, toner scattering in the developing device increases and the member is contaminated with the scattered toner. In the two-component developer, the toner ratio relative to 100 parts by mass of the magnetic carrier can be arbitrarily controlled by changing the ratio of the toner and the magnetic carrier at the time of preparing the two-component developer.

<Measurement method of true density of magnetic carrier>
The true specific gravity of the magnetic carrier is measured using a dry automatic densitometer AccuPick 1330 (manufactured by Shimadzu Corporation). First, 5 g of a sample sample left in an environment of 23 ° C. and 50% RH for 24 hours is accurately weighed, placed in a measurement cell (10 cm ³ ), and inserted into the main body sample chamber. The measurement can be automatically performed by inputting the sample sample mass into the main body and starting the measurement.
The measurement conditions in the automatic measurement were that helium gas adjusted at 20.000 psig (2.392 × 10 ² kPa) was used, and after purging the sample chamber 10 times, the pressure change in the sample chamber was 0.005 psig / min (3 .447 × 10 ⁻² kPa / min) is set as an equilibrium state, and helium gas is repeatedly purged until the equilibrium state is reached. Measure the pressure in the sample chamber in the equilibrium state. The sample sample volume can be calculated from the pressure change when the equilibrium state is reached (Boil's law). Since the volume of the sample sample can be calculated, the true specific gravity of the sample sample can be calculated by the following formula.
True specific gravity of sample sample (g / cm ³ ) = Sample sample mass (g) / Sample sample volume (cm ³ )
The average of the values measured five times by this automatic measurement is defined as the true specific gravity (g / cm ³ ) of the magnetic carrier and magnetic core particles.

<Measuring Method of Average Circularity of Toner and Number% of Particles with Equivalent Circle Diameter of 0.50 μm to 1.98 μm>
The average circularity of the toner is calibrated using a flow type particle image measuring apparatus “FPIA-3000 type” (manufactured by Sysmex Corporation) having an image processing resolution of 512 × 512 pixels (0.37 μm × 0.37 μm per pixel). Measure under the same measurement and analysis conditions.
A specific measurement method is as follows. First, about 20 ml of ion-exchanged water from which impure solids are removed in advance is put in a glass container. 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 0.2 ml of a diluted solution obtained by diluting the solution with ion exchange water about 3 times by mass. Further, about 0.02 g of a measurement sample is added, and dispersion treatment is performed for 2 minutes using an ultrasonic disperser to obtain a dispersion for measurement. In that case, it cools suitably so that the temperature of a dispersion liquid may become 10 to 40 degreeC. As the ultrasonic disperser, a desktop type ultrasonic cleaner disperser (for example, “VS-150” (manufactured by VervoCrea)) having an oscillation frequency of 50 kHz and an electric output of 150 W is used. Ion exchange water is added, and about 2 ml of the above-mentioned Contaminone N is added to this water tank.
The flow type particle image analyzer equipped with a standard objective lens (10 ×) is used for measurement, and a particle sheath “PSE-900A” (manufactured by Sysmex Corporation) is used as the sheath liquid.
By using a standard objective lens (10 ×), the image processing resolution is 512 × 512 pixels (0.37 μm × 0.37 μm per pixel).
The dispersion prepared in accordance with the above procedure is introduced into the flow type particle image analyzer, and 3000 toner particles are measured in the HPF measurement mode and in the total count mode. Then, the binarization threshold at the time of particle analysis is set to 85%, the analysis particle diameter is limited to a circle equivalent diameter of 1.98 μm or more and less than 200.00 μm, and is divided into 800 in a range of circularity of 0.200 or more and 1.000 or less. To obtain the average circularity of the toner particles.
In measurement, automatic focus adjustment is performed using standard latex particles (for example, “RESEARCH AND TEST PARTICLES Latex Microsphere Suspensions 5200A” manufactured by Duke Scientific) diluted with ion-exchanged water before starting the measurement. Thereafter, it is preferable to perform focus adjustment every two hours from the start of measurement.
In the examples of the present application, a flow-type particle image analyzer that has been issued a calibration certificate issued by Sysmex Corporation, which has been calibrated by Sysmex Corporation, was used. The analysis particle diameter is measured under the measurement and analysis conditions when the calibration certificate is received, except that the equivalent particle diameter is limited to 1.98 μm or more and less than 200.00 μm.
At this time, the ratio of particles of 0.50 μm or more and 1.98 μm or less to all particles having an equivalent circle diameter of 0.50 μm or more and 200.00 μm or less is obtained as number%.

<Calculation method of area% of portion derived from metal oxide on magnetic carrier surface>
The area% of the portion derived from the metal oxide on the surface of the magnetic carrier can be determined by observing the projected image of reflected electrons with a scanning electron microscope and subsequent image processing.
The area% of the portion derived from the metal oxide on the surface of the magnetic carrier is calculated using a scanning electron microscope (SEM) and S-4800 (manufactured by Hitachi, Ltd.). The area of the portion derived from the metal oxide is calculated from image processing of an image obtained by visualizing reflected electrons obtained when the acceleration voltage is 2.0 kV. In observation with a scanning electron microscope, it is known that the amount of reflected electrons emitted from a sample is larger as a heavy element. In a sample having a resin part and a metal oxide part derived from a magnetic core, such as the magnetic carrier surface used in the present invention, the metal oxide part is bright (high brightness, white), and the resin part is dark (luminance) Therefore, images with large contrast differences can be obtained.
Specifically, a magnetic carrier is fixed with a carbon tape on a sample stage for observation with a scanning electron microscope in a single layer, and vapor deposition with platinum is not performed. Observe with 4800 (manufactured by Hitachi, Ltd.). Observation is performed after the flushing operation.
SignalName = SE (U, LA80)
AcceleratingVoltage = 2000Volt
EmissionCurrent = 10000nA
Working distance = 6000um
LensMode = High
Condencer1 = 5
ScanSpeed = Slow4 (40 seconds)
Magnification = 600
DataSize = 1280x960
ColorMode = Grayscale
The projected image of the reflected electrons is adjusted to “contrast 5, brightness-5” on the control software of the scanning electron microscope S-4800, the capture speed / total number of images “Slow4 is 40 seconds”, and the image size is 1280 × Obtained as a 960 pixel 8-bit 256 gray scale image (FIG. 3 (3-a)). From the scale on the image, the length of 1 pixel is 0.1667 μm, and the area of 1 pixel is 0.0278 μm ² .
Subsequently, using the obtained projected image of the reflected electrons, the area% of the portion derived from the metal oxide is calculated for 50 magnetic carriers. Details of the method of selecting 50 magnetic carriers to be analyzed will be described later. Image processing software Image-Pro Plus 5.1J (manufactured by Media Cybernetics) is used to calculate the area% of the portion derived from the metal oxide.
First, the character string at the bottom of the image in FIG. 3 (3-b) is unnecessary for image processing, and unnecessary portions are deleted and cut out to a size of 1280 × 895 (FIG. 3 (3-c)). Next, the magnetic carrier portion was extracted, and the size of the extracted magnetic carrier portion was counted. Specifically, first, in order to extract the magnetic carrier to be analyzed, the magnetic carrier and the background portion are separated. Select “Measurement”-“Count / Size” of Image-Pro Plus 5.1J. In the “Brightness range selection” of “Count / Size”, the brightness range is set to a range of 50 to 255, and the low-brightness carbon tape portion reflected as the background is excluded to extract the magnetic carrier (see FIG. 3 (3-d)). When a magnetic carrier is fixed by a method other than carbon tape, there is no possibility that the background does not necessarily have a low luminance area or that the luminance is partially the same as that of the magnetic carrier. However, the boundary between the magnetic carrier and the background can be easily distinguished from the projected image of the reflected electrons. When performing the extraction, select the 4 option in the “Count / Size” extraction option, enter a smoothness of 5 and check “Fill hole”. Particles overlapping other particles are excluded from the calculation. Next, in the “count / size” measurement item, an area and a ferret diameter (average) are selected, and the area selection range is set to a minimum of 300 pixels and a maximum of 10000000 pixels (FIG. 4 (4-a)). In addition, the selection range is set so that the ferret diameter (average) is within a range of ± 25% of the measured value of the volume distribution reference 50% particle diameter (D50) of the magnetic carrier, which will be described later, and the magnetic carrier for image analysis is extracted (FIG. 4 (4-b)). The size (number of pixels) derived from the extracted magnetic carrier is determined as (ja), the sum of the extracted portions (Σja = Ja), and the number of extracted portions (Jc). The same operation is repeated for the magnetic carrier projection image of another field until the number Jc of the extracted magnetic carriers becomes Jc = 50.
Next, a portion derived from the metal oxide was extracted from the selected particles. In “Brightness range selection” of “Count / Size” of Image-Pro Plus 5.1J, the brightness range is set to a range of 140 to 255, and a portion with high brightness on the magnetic carrier is extracted. The area selection range is a minimum of 10 pixels and a maximum of 10000 pixels, and a portion derived from the metal oxide on the surface of the magnetic carrier is extracted (FIG. 4 (4-c)). Further, similarly to the extraction of the magnetic carrier part, particles located on the outer periphery of the image and those deviating from the range of ± 25% diameter of the measured value of 50% particle diameter (D50) were excluded from the calculation. The size (pixel number) (ma) of the extracted portion derived from the metal oxide and the sum (Ma) of each extracted portion were calculated according to the following formula.
Formula: Area% of part derived from metal oxide = Ma / Ja × 100

<Calculation method of area% of portion derived from metal oxide of 6.672 μm ² or more>
The area% of the area derived from the metal oxide of 6.672 μm ² or more with respect to the total area of the area derived from the metal oxide is the observation and image processing of the reflected electron projection image by the scanning electron microscope, and subsequent statistics. It can be determined by processing. In the same manner as obtaining the area% of the portion derived from the metal oxide, the magnetic carrier was observed, and the portion derived from the metal oxide in the magnetic carrier was extracted from the image. Portions derived from the extracted metal oxide were distributed in channels of size 20 pixels. Area of 1pixel performs the area calculated as 0.0278Myuemu ^2, the total area of the part from the metal oxide, and calculating the ratio distributed in 6.672Myuemu ² or more.

<Measuring method of envelope of magnetic carrier>
A focused ion beam processing observation apparatus (FIB) and FB-2100 (manufactured by Hitachi High-Technologies Corporation) are used for the cross-section processing of the magnetic carrier. 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 processing (beam current: 7 nA), and the sample cross section is cut out.
The magnetic carrier used as a sample is a magnetic carrier that satisfies D50 × 0.9 ≦ Dmax ≦ D50 × 1.1, where Dmax is the maximum diameter of each sample. Further, the position of the plane including the maximum length in the direction parallel to the fixing surface of each sample is set as a distance h from the fixing surface (for example, h = r in the case of a perfect sphere having a radius r). . A cross section is cut out in a direction perpendicular to the fixing surface within a range of 0.9 × h to 1.1 × h from the fixing surface.
The sample whose cross section has been processed can be directly applied to observation with a scanning electron microscope (SEM). In observation with a scanning electron microscope, it is known that the amount of reflected electrons emitted from a sample is larger as a heavy element. For example, in the case of a sample in which an organic compound and a metal such as iron are distributed in a planar shape, the amount of reflected electrons emitted from iron is detected more, so the iron portion is bright on the image (high brightness) White). On the other hand, since the amount of reflected electrons from the organic compound composed of the light element compound is small, it appears dark on the image (low brightness and black). In cross-sectional observation of the magnetic carrier, the metal oxide portion derived from the magnetic core region is bright (high brightness, white), and the region other than the magnetic core portion appears dark (low brightness, black). An image with a contrast difference is obtained. Specifically, observation is performed under the following conditions using a scanning electron microscope (SEM) and S-4800 (manufactured by Hitachi High-Technologies Corporation). Observe after performing the flushing operation.
SignalName = SE (U, LA100)
AcceleratingVoltage = 5000Volt
EmissionCurrent = 10000nA
Working distance = 4000um
LensMode = High
Condencer1 = 3
ScanSpeed = Slow4 (40 sec)
Magnification = 1500
DataSize = 1280x960
ColorMode = Grayscale
SpecimenBias = 0V
In addition to the above conditions, the projected image of the reflected electrons is adjusted to brightness of “contrast 5, brightness-5” on the control software of the scanning electron microscope S-4800, the magnetic substance observation mode is turned off, and the 256th floor. Obtained as a gray scale image.
Next, using the obtained projection image, image processing software Image-Pro Plus 5.1J (manufactured by Media Cybernetics) is used to determine the envelope L2 and the perimeter L1 for 50 magnetic carriers, and the envelope from the following equation Find the degree.
Formula: Envelope degree = {(L1-L2) / L2} × 100

<Measurement of weight average particle diameter (D4) of toner>
The weight average particle diameter (D4) of the toner is a precision particle size distribution measuring apparatus “Coulter Counter Multisizer by pore electrical resistance method equipped with an aperture tube of 100 μm.
3 ”(registered trademark, manufactured by Beckman Coulter) and attached dedicated software“ Beckman Coulter Multisizer 3 Version 3.51 ”(manufactured by Beckman Coulter, Inc.) for measurement condition setting and measurement data analysis, Measure with 25,000 effective measurement channels, analyze and calculate the measurement data.
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 is 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, the number of measurements is 1 and the Kd value is “standard particles 10.0 μm” (Beckman Coulter 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 or more and 60 μm or less.
The specific measurement method is as follows.
(1) About 200 ml of the electrolytic solution is placed in a glass 250 ml round bottom beaker exclusively for Multisizer 3, set on a sample stand, and the stirrer rod is stirred counterclockwise at 24 rpm. Then, dirt and bubbles in the aperture tube are removed by the “aperture flush” function of the analysis software.
(2) About 30 ml of the electrolytic aqueous solution is put in a glass 100 ml flat bottom beaker, and "Contaminone N" (nonionic surfactant, anionic surfactant, organic builder pH 7 precision measurement is used as a dispersant therein. About 0.3 ml of a diluted solution obtained by diluting a 10% by weight aqueous solution of a neutral detergent for washing a vessel (made by Wako Pure Chemical Industries, Ltd.) 3 times 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 Dissipation System Tetora 150” (manufactured by Nikkiki Bios Co., Ltd.) having an electrical output of 120 W. A predetermined amount of ion-exchanged water is put, and about 2 ml of the above-mentioned Contaminone N is added to this water tank.
(4) The beaker of (2) is set in the beaker fixing hole of the ultrasonic disperser, and the ultrasonic disperser is operated. And the height position of a beaker is adjusted so that the resonance state of the liquid level of the electrolyte solution in a beaker may become the maximum.
(5) In a state where the electrolytic aqueous solution in the beaker of (4) is irradiated with ultrasonic waves, about 10 mg of toner is added to the electrolytic aqueous solution little by little and dispersed. Then, the ultrasonic dispersion process is continued for another 60 seconds. In the ultrasonic dispersion, the temperature of the water tank is appropriately adjusted so as to be 10 ° C. or higher and 40 ° C. or lower.
(6) To the round bottom beaker of (1) installed in the sample stand, the electrolyte solution of (5) in which the toner is dispersed is dropped using a pipette, and the measurement concentration is adjusted to about 5%. . Measurement is performed until the number of measured particles reaches 50,000.
(7) The measurement data is analyzed with the dedicated software attached to the apparatus, and the weight average particle diameter (D4) is calculated. The “average diameter” on the analysis / volume statistics (arithmetic average) screen when the graph / volume% is set with the dedicated software is the weight average particle diameter (D4).

<Measurement method of resin peak molecular weight (Mp), number average molecular weight (Mn), weight average molecular weight (Mw)>
The molecular weight distribution of the resin is measured by gel permeation chromatography (GPC) as follows.
First, the resin is dissolved in tetrahydrofuran (THF) at room temperature over 24 hours. The obtained solution is filtered through a solvent-resistant membrane filter “Maescho Disc” (manufactured by Tosoh Corporation) having a pore diameter of 0.2 μm to obtain a sample solution. The sample solution is adjusted so that the concentration of the component soluble in THF is about 0.8% by mass. Using this sample solution, measurement is performed under the following conditions.
Apparatus: HLC8120 GPC (detector: RI) (manufactured by Tosoh Corporation)
Column: Shodex KF-801, 802, 803, 804, 805, 806,
7 series of 807 (made by Showa Denko)
Eluent: Tetrahydrofuran (THF)
Flow rate: 1.0 ml / min
Oven temperature: 40.0 ° C
Sample injection volume: 0.10 ml
In calculating the molecular weight of the sample, standard polystyrene resin (for example, trade name “TSK Standard Polystyrene F-850, F-450, F-288, F-128, F-80, F-40, F-20, F— 10, F-4, F-2, F-1, A-5000, A-2500, A-1000, A-500 ", manufactured by Tosoh Corporation) are used.

<Measurement method of maximum endothermic temperature of wax and glass transition temperature (Tg) of resin>
The temperature showing the maximum endothermic peak of the wax is the differential scanning calorimeter “Q1000” (TA
Measured in accordance with ASTM D3418-82 using Instruments, Inc.).
The temperature correction of the device detection unit uses the melting points of indium and zinc, and the correction of heat uses the heat of fusion of indium. Specifically, about 10 mg of wax is precisely weighed, placed in an aluminum pan, and an empty aluminum pan is used as a reference. Measurement is performed at ° C / min. In the measurement, the temperature is once raised to 200 ° C., subsequently lowered to 30 ° C., and then the temperature is raised again. The temperature showing the maximum endothermic peak of the DSC curve in the temperature range of 30 to 200 ° C. in the second temperature raising process is defined as the maximum endothermic temperature.
Further, the glass transition temperature (Tg) of the resin is measured by precisely weighing about 10 mg of the resin in the same manner as in the wax measurement. In the specific heat change in the temperature range of 40 ° C. to 100 ° C., the intersection of the midpoint line of the baseline before and after the specific heat change and the DSC curve is defined as the glass transition temperature (Tg) of the binder resin. .

<Measurement method of softening point of resin>
The softening point of the resin is measured by using a constant load extrusion type capillary rheometer “flow characteristic evaluation device Flow Tester CFT-500D” (manufactured by Shimadzu Corporation) according to the manual attached to the device. In this device, while applying a constant load from the top of the measurement sample with the piston, the measurement sample filled in the cylinder is heated and melted, and the melted measurement sample is pushed out from the die at the bottom of the cylinder, and the piston drop amount at this time A flow curve showing the relationship between temperature and temperature can be obtained.
In the present invention, the “melting temperature in the 1/2 method” described in the manual attached to the “flow characteristic evaluation apparatus Flow Tester CFT-500D” is the softening point. The melting temperature in the 1/2 method is calculated as follows. First, ½ of the difference between the piston lowering amount Smax at the time when the outflow ends and the piston lowering amount Smin at the time when the outflow starts is obtained (this is X. X = (Smax−Smin) / 2). Then, the temperature of the flow curve when the piston descending amount is the sum of X and Smin in the flow curve is the melting temperature in the 1/2 method.
As a measurement sample, about 1.0 g of resin is compression-molded at about 10 MPa at about 10 MPa in a 25 ° C. environment using a tablet molding compressor (for example, NT-100H, manufactured by NPA System). A cylindrical shape having a diameter of about 8 mm is used. Moreover, the measurement conditions of CFT-500D are as follows.
Test mode: Temperature rising start temperature: 40 ° C
Achieving temperature: 200 ° C
Measurement interval: 1.0 ° C
Temperature increase rate: 4.0 ° C./min
Piston cross-sectional area: 1.000 cm ²
Test load (piston load): 10.0 kgf (0.9807 MPa)
Preheating time: 300 seconds Die hole diameter: 1.0 mm
Die length: 1.0mm

<Measurement method of 50% particle size (D50) based on volume distribution of magnetic carrier>
The particle size distribution was measured with a laser diffraction / scattering particle size distribution measuring apparatus “Microtrack MT3300EX” (manufactured by Nikkiso Co., Ltd.). The measurement was performed by attaching a sample feeder “One-shot dry type sample conditioner Turbotrac” (manufactured by Nikkiso Co., Ltd.) for dry measurement. As the supply conditions of Turbotrac, a dust collector was used as a vacuum source, the air volume was about 33 liters / sec, and the pressure was about 17 kPa. Control is automatically performed on software. For the particle size, a 50% particle size (D50), which is a cumulative value based on volume distribution, 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: Normal temperature and humidity environment (23 ° C, 50% RH)

  Specific examples of the present invention will be described below, but the present invention is not limited to these examples. In addition, the number of parts in the following composition is part by mass unless otherwise specified.

[Production Example 1 of Resin]
The following materials were weighed in a reaction vessel equipped with a cooling tube, a stirrer, and a nitrogen introduction tube.
Terephthalic acid 22.6 parts by weight trimellitic anhydride 1.7 parts by weight polyoxypropylene (2.2) -2,2-bis (4-hydroxyphenyl) propane
75.6 parts by mass Titanium dihydroxybis (triethanolaminate) 0.1 parts by mass Thereafter, the mixture is heated to 200 ° C., reacted for 10 hours while removing water generated while introducing nitrogen, and then reduced in pressure to 10 mmHg. Resin 1 was synthesized by reacting for 1 hour. The molecular weight of the resin 1 determined by GPC was a weight average molecular weight (Mw) of 6200, a number average molecular weight (Mn) of 2500, a peak molecular weight (Mp) of 2900, a glass transition point of 55 ° C., and a softening point of 93 ° C. .

[Resin Production Example 2]
The following materials were weighed in a reaction vessel equipped with a cooling tube, a stirrer, and a nitrogen introduction tube.
Terephthalic acid 17.2 parts by weight polyoxyethylene (2.2) -2,2-bis (4-hydroxyphenyl) propane
76.6 parts by mass Titanium dihydroxybis (triethanolaminate) 0.1 parts by mass Thereafter, the mixture was heated to 220 ° C. and reacted for 10 hours while removing water produced while introducing nitrogen. Further, 6.1 parts by mass of trimellitic anhydride was added, heated to 180 ° C., and reacted for 2 hours to synthesize resin 2. The molecular weight of the resin 2 determined by GPC was a weight average molecular weight (Mw) of 86000, a number average molecular weight (Mn) of 6000, a peak molecular weight (Mp) of 12800, a glass transition point of 62 ° C., and a softening point of 132 ° C.

[Toner Production Example 1]
Resin 1 50.0 parts by mass Resin 2 50.0 parts by mass Fischer-Tropsch wax (maximum endothermic temperature: 75 ° C.) 7.5 parts by mass C.I. I. Pigment Blue 15: 3 5.0 parts by mass After the above materials were thoroughly mixed with a Henschel mixer (FM-75 type, manufactured by Mitsui Miike Chemical Co., Ltd.), a twin-screw kneader (PCM-30) set at a temperature of 130 ° C. Kneaded with a mold, manufactured by Ikekai Tekko Co., Ltd. The obtained kneaded material was cooled and coarsely pulverized to 1 mm or less with a hammer mill to obtain a coarsely pulverized material. The obtained coarsely crushed material was finely pulverized using a collision-type airflow pulverizer using high-pressure gas.
Next, the obtained finely pulverized product was subjected to surface modification using a surface modification apparatus shown in FIG. The conditions for the surface modification were as follows: the raw material supply rate was 2.0 kg / hr, the hot air flow rate was 4.5 m ³ / min, the hot air discharge temperature was 230 ° C., the cold air temperature was 0 ° C., and the cold air flow rate was 3.0 m ³ / min. It was. Next, classification was performed with an air classifier (Elbow Jet Lab EJ-L3, manufactured by Nippon Steel Mining Co., Ltd.) utilizing the Coanda effect, and fine powder and coarse powder were simultaneously classified and removed to obtain toner particles 1.
In 100.0 parts by mass of the toner particles 1 thus obtained, inorganic fine particles having a number average particle diameter of 40 nm and 1.0 part by mass of titanium oxide fine powder treated with i-butyltrimethoxysilane, a primary average particle diameter. Sol-gel silica fine powder having a number average particle diameter of 200 nm and treated with hexamethyldisilazane, 0.5 parts by mass of hydrophobic silica fine particles of 16 nm and surface-treated with 20% by mass of hexamethyldisilazane The toner 1 was obtained by externally mixing 1.0 part by mass of the toner.

[Toner Production Example 2]
Example 1 of toner production example 1 except that the flow rate of hot air under conditions during surface modification was changed from 4.5 m ³ / min to 4.0 m ³ / min and the discharge temperature of hot air was changed from 230 ° C. to 210 ° C. 1 was obtained in the same manner as in Example 1.

[Toner Production Example 3]
Example 1 of toner production example 1 except that the flow rate of hot air under conditions for surface modification was changed from 4.5 m ³ / min to 5.0 m ³ / min and the discharge temperature of hot air was changed from 230 ° C. to 250 ° C. 1 was obtained in the same manner as in Example 1.

[Toner Production Example 4]
Toner 4 was obtained in the same manner as in Toner Production Example 1 except that the surface modification treatment was not performed in Toner Production Example 1.

Table 1 shows the physical properties of Toners 1 to 4.

[Production Example 1 of Porous Magnetic Core]
<Process 1 (weighing / mixing process)>
Fe ₂ O ₃ 59.7% by mass
MnCO ₃ 34.4% by mass
Mg (OH) ₂ 4.8% by mass
SrCO ₃ 1.1% by mass
The ferrite raw material was weighed so that Thereafter, the mixture was pulverized and mixed for 2 hours in a dry ball mill using zirconia (φ10 mm) balls.
<Step 2 (temporary firing step)>
After pulverization and mixing, using a burner-type firing furnace, firing was performed at 950 ° C. for 2 hours in the air to prepare calcined ferrite.
The composition of ferrite is as follows.
(MnO) _a (MgO) _b (SrO) _c (Fe ₂ O ₃ ) _d
In the above formula, a = 0.39, b = 0.11, c = 0.01, d = 0.49
<Step 3 (grinding step)>
After crushing to about 0.5 mm with a crusher, 30 parts by mass of water was added to 100 parts by mass of calcined ferrite using zirconia (φ10 mm) balls, and the mixture was pulverized with a wet ball mill for 2 hours. The slurry was pulverized for 3 hours by a wet bead mill using zirconia beads (φ1.0 mm) to obtain a ferrite slurry (calcined ferrite finely pulverized product).
The obtained calcined ferrite finely pulverized product had a volume-based 50% particle size (D50) of 1.7 μm.
<Process 4 (granulation process)>
To the ferrite slurry, 2.0 parts by mass of polyvinyl alcohol was added as a binder with respect to 100 parts by mass of calcined ferrite, and granulated into spherical particles of about 36 μm with a spray dryer (manufacturer: Okawahara Chemical).
<Step 5 (main firing step)>
In order to control the firing atmosphere, firing was performed at 1150 ° C. for 4 hours in a nitrogen atmosphere (oxygen concentration of 0.01% by volume or less) in an electric furnace.
<Process 6 (sorting process)>
After the aggregated particles were crushed, coarse particles were removed by sieving with a sieve having an opening of 250 μm to obtain a porous magnetic core 1.

<Production Example 2 of Porous Magnetic Core>
Of the porous magnetic core production example 1, the ratio of the ferrite raw material in step 1 is
Fe ₂ O ₃ 62.8 mass%
MnCO ₃ 31.2% by mass
Mg (OH) ₂ 6.0% by mass
Changed to The composition of ferrite is as follows.
(MnO) _a (MgO) _b (Fe ₂ O ₃ ) _c
In the above formula, a = 0.45, b = 0.15, c = 0.40
The particle size of the crusher in Step 3 was changed from about 0.5 mm to about 0.3 mm, the ball of the wet ball mill was changed from zirconia (φ10 mm) to stainless steel (φ10 mm), and the beads of the wet bead mill were changed from zirconia (φ1.0 mm). The grinding time was changed from 3 hours to 2 hours for stainless steel (φ1.0 mm).
The obtained calcined ferrite finely pulverized product had D50 = 0.8 μm.
The amount of polyvinyl alcohol added in step 4 was changed from 2 parts by mass to 1.0 part by mass.
The firing temperature in step 5 is changed from 1150 ° C. to 1200 ° C., the firing atmosphere is changed from a nitrogen atmosphere (oxygen concentration 0.01% by volume or less) to a nitrogen atmosphere (oxygen concentration 1.0% by volume), and the firing time is started from 4 hours. Changed to 8 hours. Except for the above, a porous magnetic core 2 was obtained in the same manner as in Production Example 1 of the porous magnetic core.

<Production Example 3 of Porous Magnetic Core>
In the porous magnetic core production example 1, the pulverization time of the wet bead mill in step 3 was changed from 2 hours to 3 hours. The obtained calcined ferrite finely pulverized product had D50 = 1.3 μm. In addition, the firing temperature in step 5 was changed from 1150 ° C. to 1050 ° C. Except for the above, a porous magnetic core 3 was obtained in the same manner as in the porous magnetic core production example 1.

<Production Example 4 of Porous Magnetic Core>
Of the porous magnetic core production example 1, the ratio of the ferrite raw material in step 1 is
Fe ₂ O ₃ 62.4% by mass
MnCO ₃ 30.5% by mass
Mg (OH) ₂ 6.4% by mass
SrCO ₃ 0.7% by mass
Changed to The composition of ferrite is as follows.
(MnO) _a (MgO) _b (SrO) _c (Fe ₂ O ₃ ) _d
In the above formula, a = 0.34, b = 0.14, c = 0.01, d = 0.51
The pulverization particle size in the crusher in Step 3 was changed from about 0.5 mm to about 1.0 mm, the ball of the wet ball mill was changed from zirconia (φ10 mm) to alumina (φ10 mm), and the pulverization time was changed from 2 hours to 1 hour. The beads of the wet bead mill were changed from zirconia (φ1.0 mm) to alumina (φ1.0 mm). The obtained calcined ferrite fine pulverized product had a D50 of 4.8 μm.
The amount of polyvinyl alcohol added in Step 4 was changed from 2.0 parts by mass to 5.0 parts by mass.
The firing temperature in Step 5 was changed from 1150 ° C. to 1000 ° C., and the firing atmosphere was changed from a nitrogen atmosphere (oxygen concentration 0.01% by volume or less) to a nitrogen atmosphere (oxygen concentration 0.5% by volume). Except for the above, a porous magnetic core 4 was obtained in the same manner as in Production Example 1 of the porous magnetic core.

<Production Example 5 of Porous Magnetic Core>
Of the porous magnetic core production example 1, the ratio of the ferrite raw material in step 1 is
Fe ₂ O ₃ 62.8 mass%
MnCO ₃ 31.2% by mass
Mg (OH) ₂ 6.0% by mass
Changed to The composition of ferrite is as follows.
(MnO) _a (MgO) _b (Fe ₂ O ₃ ) _c
In the above formula, a = 0.45, b = 0.15, c = 0.40
The particle size of the crusher in Step 3 was changed from about 0.5 mm to about 0.3 mm, the ball of the wet ball mill was changed from zirconia (φ10 mm) to stainless steel (φ10 mm), and the beads of the wet bead mill were changed from zirconia (φ1.0 mm). The grinding time was changed from 3 hours to 2 hours for stainless steel (φ1.0 mm).
The obtained calcined ferrite finely pulverized product had D50 = 0.8 μm.
The amount of polyvinyl alcohol added in step 4 was changed from 2.0 parts by mass to 1.0 part by mass.
The firing temperature in step 5 is changed from 1150 ° C. to 1200 ° C., the firing atmosphere is changed from a nitrogen atmosphere (oxygen concentration 0.01% by volume or less) to a nitrogen atmosphere (oxygen concentration 1.0% by volume), and the firing time is started from 4 hours. Changed to 8 hours. Except for the above, a porous magnetic core 5 was obtained in the same manner as in Porous Magnetic Core Production Example 1.

<Production Example 6 of Porous Magnetic Core>
In porous magnetic core production example 4, the pulverization time of the wet bead mill in step 3 was changed from 3 hours to 2 hours. The obtained calcined ferrite finely pulverized product had D50 = 5.6 μm.
The amount of polyvinyl alcohol added in Step 4 was changed from 5.0 parts by mass to 10.0 parts by mass.
The firing time in step 5 was changed from 4 hours to 2 hours, and the firing atmosphere was changed from a nitrogen atmosphere (oxygen concentration 0.5 vol%) to a nitrogen atmosphere (oxygen concentration 1.0 vol%). Except for the above, the porous magnetic core 6 was obtained in the same manner as in the porous magnetic core production example 4.

<Production Example 7 of Porous Magnetic Core>
Of the porous magnetic core production example 4, the pulverization particle size in the crusher in step 3 was changed from about 1.0 mm to about 0.3 mm, and the ball of the wet ball mill was changed from alumina (φ10 mm) to stainless steel (φ10 mm). Was changed from 1 hour to 3 hours. The beads of the wet bead mill were changed from alumina (φ1.0 mm) to stainless steel (φ1.0 mm), and the grinding time was changed from 3 hours to 2 hours. The obtained calcined ferrite finely pulverized product had D50 = 0.4 μm.
The amount of polyvinyl alcohol added in step 4 was changed from 5.0 parts by mass to 1.0 part by mass.
The firing temperature in step 5 was changed from 1000 ° C. to 1250 ° C. Except for the above, a porous magnetic core 7 was obtained in the same manner as in Production Example 4 of the porous magnetic core.

<Manufacture example 1 of a magnetic core>
Magnetite fine particles (spherical, number average particle size 250 nm, magnetization strength 65 Am ² / kg, remanent magnetization 4.2 Am ² / kg, coercive force 4.4 kA / m, specific resistance 3.3 × 10 ⁵ Ω at 500 V / cm Cm) and a silane coupling agent (3- (2-aminoethylaminopropyl) trimethoxysilane) (amount of 3.0% by mass with respect to the mass of magnetite fine particles) were introduced into the container. Then, the magnetite fine particles were surface-treated by mixing and stirring at a high temperature at a temperature of 100 ° C. or higher in the container.
-Phenol 10 mass parts-Formaldehyde solution (formaldehyde 37 mass% aqueous solution) 16 mass parts-Surface-treated said magnetite fine particle 84 mass parts The said material was introduce | transduced into the reaction kettle, and it was made into the temperature of 40 degreeC, and was mixed well.
Thereafter, the mixture was heated to 85 ° C. at an average temperature increase rate of 3 ° C./min with stirring, and 4 parts by mass of 28% by mass aqueous ammonia and 25 parts by mass of water were added to the reaction kettle. It was held at a temperature of 85 ° C. and cured by polymerization reaction for 3 hours. The peripheral speed of the stirring blade at this time was 1.8 m / sec.
After the polymerization reaction, the mixture was cooled to 30 ° C. and water was added. The precipitate obtained by removing the supernatant was washed with water and further air-dried. The obtained air-dried product was dried at a temperature of 60 ° C. under reduced pressure (5 hPa or less) to obtain a magnetic core 1 in which a magnetic material was dispersed in a resin.

<Manufacture example 2 of magnetic core>
Step 1:
Fe ₂ O ₃ 71.0 mass%
CuO 12.5 mass%
ZuO 16.5% by mass
The ferrite raw material was weighed so that Thereafter, the mixture was pulverized and mixed for 2 hours in a dry ball mill using zirconia (φ10 mm) balls.
Step 2:
After pulverization and mixing, firing was performed at 950 ° C. for 2 hours in the air to prepare calcined ferrite.
The composition of ferrite is as follows.
(CuO) _a (ZnO) _b (Fe ₂ O ₃ ) _c
In the above formula, a = 0.20, b = 0.25, c = 0.55
Step 3:
After crushing to about 0.5 mm with a crusher, 30 parts by mass of water was added to 100 parts by mass of calcined ferrite using a stainless ball (φ10 mm), and the mixture was pulverized with a wet ball mill for 6 hours. The obtained calcined ferrite finely pulverized product had D50 = 0.5 μm and D90 = 2.8 μm.
Step 4:
To the ferrite slurry, 2.0 parts by mass of polyvinyl alcohol was added as a binder with respect to 100 parts by mass of calcined ferrite, and granulated into spherical particles with a spray dryer (manufacturer: Okawahara Chemical).
Step 5:
Firing was performed at 1300 ° C. for 4 hours in the air.
Step 6:
After the agglomerated particles were crushed, coarse particles were removed by sieving with a sieve having an opening of 250 μm to obtain a magnetic core 2.

<Preparation of resin solution>
Resin liquid 1
Straight silicone (SR2411 Toray Dow Corning) 20.0 parts by mass γ-aminopropyltriethoxysilane 0.5 parts by mass Toluene 79.5 parts by mass Using a ball mill (soda glass ball φ10 mm) for 1 hour, Resin liquid 1 was obtained.

Resin liquid 2
Polymethyl methacrylate polymer (Mw = 66,000) 5.0 parts by mass Bontron P51 (Orient Chemical Co., Ltd.) 2.0 parts by mass Toluene 93.0 parts by mass The above was used using a bead mill (zirconia beads φ1.0 mm). For 3 hours to obtain a resin liquid 2.

<Example of production of magnetic carrier 1>
Step 1 (resin filling step):
100.0 parts by mass of the porous magnetic core 1 is put into a universal stirring mixer (manufactured by Dalton) and stirred while heating to 80 ° C. under reduced pressure. Subsequently, the resin liquid 1 was added to 100 parts by mass of the porous magnetic core 1 so as to be 8 parts by mass as a resin component, and heating was continued for 2 hours to remove the solvent. The obtained sample was transferred to a Julia mixer (manufactured by Tokuju Kogakusha Co., Ltd.), heat-treated at 200 ° C. for 2 hours in a nitrogen atmosphere, and classified with a mesh having an opening of 70 μm to obtain a filled core 1.
Process 2 (resin coating process):
100.0 parts by mass of the filling core 1 was put into a Nauta mixer (manufactured by Hosokawa Micron), and further, the resin liquid 2 was put into the Nauta mixer so as to be 0.5 parts by mass as a resin component. It heated at 70 degreeC under pressure reduction, mixed by 1.7S < ^-1 > (100 rpm), and solvent removal and application | coating operation were performed over 4 hours. Thereafter, the obtained sample was transferred to a Julia mixer (manufactured by Tokuju Kogakusha Co., Ltd.), heat-treated at a temperature of 200 ° C. for 2 hours in a nitrogen atmosphere, and then classified with a mesh having an opening of 70 μm to obtain a magnetic carrier 1.

<Production example of magnetic carriers 2 to 13>
In the production example of the magnetic carrier 1, the core particles, the filling resin amount, and the coating resin amount were changed as shown in Table 2 to obtain magnetic carriers 2 to 13. Table 3 shows the physical properties of the obtained carriers 1 to 13.

[Examples 1 to 22 and Comparative Examples 1 to 12]
Using the produced magnetic carrier and toner, a two-component developer was produced in accordance with the combination of the magnetic carrier and the toner and the toner ratio with respect to 100 parts by mass of the magnetic carrier as described in Table 4. The two-component developer was mixed with a V-type mixer for 5 minutes. Table 5 shows numerical values of E _{100 mm / sec} , E _{10 mm / sec} , ΔE, and 25 FRI (E _{10 mm / sec} / E _{100 mm / sec} ) of the obtained two-component developer.

<Evaluation of two-component developer>
A Canon color copier imageRUNNER iR C3580 was used as the image forming apparatus, and the copier was modified so that the following evaluation was possible. The developer was placed in a cyan position developer and evaluated. The development conditions were modified so that the peripheral speed of the developing sleeve with respect to the developing drum was 1.5 times and the process speed was 245 mm / sec. An AC voltage and a DC voltage _VDC having a frequency of 2.0 kHz and Vpp of 1.3 kV were applied to the developing sleeve. The DC voltage _VDC was adjusted so that the amount of toner on the paper of the FFH image (solid portion) was 0.5 mg / cm ² .
Initial carrier adhesion, toner scattering, and roughness were evaluated.
Further, after continuous printing of 50000 sheets at an image area ratio of 25%, image density stability and roughness were evaluated.
The above evaluation was performed in two environments of a temperature of 23 ° C./humidity of 50% RH and a temperature of 30 ° C./humidity of 80% RH.
Note that the FFH image is a value in which 256 gradations are displayed in hexadecimal, and 00H is the first gradation (
The white background portion) and FFH are the 256th gradation (solid portion).
Printing environment Temperature 23 ° C / Humidity 50% RH (hereinafter “N / N”)
Temperature 30 ° C./Humidity 80% RH (hereinafter “H / H”)
Paper Plain paper for color copiers and printers CS-814 (A4, 81.4 g / m ² )
(Sold from Canon Marketing Japan Inc.)

<Carrier adhesion>
A 00H image is printed, a part of the photosensitive drum is sampled with a transparent adhesive tape adhered, the number of magnetic carriers adhering to the photosensitive drum in 1 cm × 1 cm is counted, and the adhering carrier per 1 cm ² is counted. The number of particles was calculated.
A: 3 or less (excellent)
B: 4 or more and 10 or less (good)
C: 11 or more and 20 or less (Acceptable level in the present invention)
D: 21 or more (not acceptable in the present invention)

<Toner scattering>
The developing device and the toner contamination in the main body were visually confirmed.
A: Almost no toner scattering (excellent)
B: Slight scattering of toner is confirmed (good)
C: Toner scattering confirmed (Acceptable level in the present invention)
D: Severe toner scattering is confirmed (not acceptable in the present invention)

<Gastsuki>
1000 sheets of FFH images with an image ratio of 5% were printed by repeating 10 sheets printing → 10 minutes leaving → 10 sheets printing.
Thereafter, a dot image (FFH image) in which one pixel is formed by one dot was created. The spot diameter of the laser beam was adjusted so that the area per dot on the paper was 20000 μm ² or more and 25000 μm ² or less. The area of 1000 dots was measured using a digital microscope VHX-500 (lens wide range zoom lens VH-Z100, manufactured by Keyence Corporation). The number average (S) of dot areas and the standard deviation (σ) of dot areas were calculated, and the roughness was calculated according to the following formula.
Gastling index (I) = σ / S × 100
A: I is less than 4.0 (excellent)
B: I is 4.0 or more and less than 6.0 (good)
C: I is 6.0 or more and less than 8.0 (Acceptable level in the present invention)
D: I is 8.0 or more (not acceptable in the present invention)

<Image density stability>
Before performing the durability evaluation, one 20 mm × 20 mm FFH image was printed. The image density of the FFH image portion was measured using an X-Rite color reflection densitometer (500 series: manufactured by X-Rite). After endurance, the same image was printed and the image density was measured. The difference in image density between the initial stage and the endurance was evaluated based on the following criteria.
(Evaluation criteria)
A: 0.00 or more and less than 0.05 (excellent)
B: 0.05 or more and less than 0.10 (good)
C: 0.10 or more and less than 0.20 (Acceptable level in the present invention)
D: 0.20 or more (not acceptable in the present invention)

Claims (4)

A two-component developer containing at least a magnetic carrier and a toner,
The toner contains toner particles containing at least a binder resin and a wax,
The magnetic carrier contains at least magnetic core particles and a resin, and has a true specific gravity of 2.5 g / cm ³ or more and 4.2 g / cm ³ or less,
The two-component developer is a two-component developer contained in a ratio of 4 parts by weight or more and 20 parts by weight or less of toner with respect to 100 parts by weight of the magnetic carrier.
E _{100 mm / sec} (mJ) and E _{100 mm / sec} (mJ) of the two-component developer, and ΔE (mJ) obtained by subtracting E _{100 mm / sec} from E _{10 mm / sec} are expressed by the following formulas (1) and ( A two-component developer characterized by satisfying 2).
Expression (1): −0.2 × E _{100 mm / sec} + 100 ≦ ΔE ≦ −0.4 × E _{100 mm / sec} +200
Formula (2): 80 ≦ E _{100 mm / sec} ≦ 360
[In the above formulas (1) and (2), E _{100 mm / sec} (mJ) is a powder fluidity analyzer equipped with a rotary propeller blade, and the propeller blade is the outermost edge of the propeller blade. While rotating at a peripheral speed of 100 mm / sec, the two-component developer powder layer is vertically entered into the two-component developer powder layer in the measurement container filled with the two-component developer. This represents the sum of the rotational torque and the vertical load obtained when the measurement is started from a position 100 mm from the bottom surface and entered to a position 10 mm from the bottom surface. Further, in ΔE (mJ) of the above formula (1), E _{10 mm / sec} (mJ) is a powder flowability analysis apparatus equipped with a rotary propeller blade, and the propeller blade is the top of the propeller blade. While rotating the peripheral speed of the outer edge at 10 mm / sec, the two-component developer powder is allowed to vertically enter the two-component developer powder layer in the measurement container filled with the two-component developer. It represents the sum of rotational torque and vertical load obtained when measurement starts from a position 55 mm from the bottom surface of the body layer and enters a position 2 mm from the bottom surface. ] Particles having an equivalent circle diameter of 1.98 μm or more and 200.00 μm or less of the toner measured by a flow type particle image measuring apparatus having an image processing resolution of 512 × 512 pixels (0.37 μm × 0.37 μm per pixel) of the toner. The average circularity analyzed by dividing into 800 in the range of the circularity of 0.200 or more and 1.000 or less is 0.950 or more and 0.990 or less,
2. The two-component development according to claim 1, wherein 25.0% by number or less of particles of 0.50 μm to 1.98 μm with respect to all particles having an equivalent circle diameter of 0.50 μm to 200.00 μm. Agent. The magnetic carrier is a magnetic carrier containing at least a magnetic core particle containing a metal oxide and a resin, and the magnetic carrier is obtained when an acceleration voltage is 2.0 kV using a scanning electron microscope. In the projected image of the reflected electrons, the area of the portion derived from the metal oxide is 0.5 area% or more and 8.0 area% or less with respect to the projected image area of the magnetic carrier, and the metal is 6.672 μm ² or more. The two-component developer according to claim 1 or 2, wherein the area of the portion derived from the oxide is 10 area% or less with respect to the total area of the portion derived from the metal oxide.   The two-component developer according to any one of claims 1 to 3, wherein the toner particles are toner particles that have been surface-treated with at least hot air.

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