JP2011158830A - Magnetic carrier and two-component developer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a magnetic carrier having superior charge-imparting properties, preventing fogging, preventing leakage or carrier deposition, even at a long-term use, and giving high quality images, without variation in density or density unevenness. <P>SOLUTION: The magnetic carrier comprises magnetic carrier particles comprising porous magnetic particles and a resin. The magnetic carrier is such that in a cross-sectional reflecting electron image of the magnetic carrier particle photographed with a scanning electron microscope, the carrier particle has a specified distribution of the thickness of the resin obtained, by measuring the distance from the surface of the magnetic carrier particle to the surface of the porous magnetic particle; and the particle has a specified number of regions of porous magnetic particle portions, having a length of 6.0 μm or more in the porous magnetic particle and a specified number of regions except porous magnetic particle portions having a length of 4.0 μm or more. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

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

  Conventionally, in electrophotography, an electrostatic latent image is formed on an electrostatic latent image carrier using various means, and toner is attached to the electrostatic latent image to develop the electrostatic latent image. Is commonly used. For this development, there are a wide variety of two-component development systems in which carrier particles called magnetic carriers are mixed with toner, triboelectrically charged, imparted with an appropriate amount of positive or negative charge to the toner, and developed as a driving force. It has been adopted.

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

  The above-mentioned magnetic carrier is generally a magnetic carrier having a coating resin layer on the surface from the viewpoint of developer life and the like, and various types of magnetic carriers have been developed and put into practical use.

  On the other hand, while the demand for higher speed has increased, the speed of machines in recent years has increased significantly. Along with this, the stress received by the developer has also increased dramatically, and it has become impossible to obtain a sufficient life even with a magnetic carrier that has been long-lived in the past.

  Therefore, it has been proposed to reduce the specific gravity of the magnetic carrier for the purpose of reducing the load between the magnetic carrier and the toner. For example, there is an attempt to develop a magnetic material-dispersed resin carrier in which a magnetic material is dispersed in a resin (see, for example, Patent Document 1).

  However, the above-mentioned magnetic material dispersion type resin carrier has a small saturation magnetization with respect to the particle size when a large amount of the magnetic material is not added to the magnetic carrier particles, and the magnetic carrier adheres on the electrostatic latent image carrier during development. There is a problem that so-called carrier adhesion occurs. In addition, when a large amount of magnetic material is added, the amount of magnetic material having low resistance increases, so that the resistance of the magnetic carrier decreases, and this tends to cause a serious problem on the image due to leakage of bias voltage applied during development. .

  Therefore, as an alternative to magnetic material-dispersed resin carriers, attempts have been made to develop magnetic carriers with reduced spent by filling the voids in the magnetic core particles of porous ferrite with silicone resin and reducing the specific gravity of the magnetic carrier. Yes (see, for example, Patent Document 2).

  The magnetic carrier reduces the load between the magnetic carrier and the toner, and can solve the spent problem even in long-term image output. However, since the load between the magnetic carrier and the toner is reduced, when images with high toner consumption are output continuously, the use of a low specific gravity magnetic carrier reduces the stress on the toner and causes sufficient frictional charging of the toner. In some cases, the ratio of the reverse polarity toner in the toner increases. As a result, so-called fogging occurs in which the reverse polarity toner adheres to the electrostatic latent image carrier. In addition, when toner with extremely strong reverse polarity is included, the toner adhesion is so large that it cannot be collected by the cleaner member, and remains on the electrostatic latent image carrier while remaining on the electrostatic latent image carrier. In some cases, exposure failure or charging failure may occur.

  Therefore, a magnetic carrier having a three-dimensional laminated structure in which a resin portion and a core portion are alternately present has been proposed (for example, see Patent Document 3). The magnetic carrier is said to have a stable charge imparting property by having a capacitor property. However, when the toner is developed, counter charges having a polarity opposite to that of the toner remain on the surface of the magnetic carrier. The counter charges move along the core region inside the magnetic carrier. However, since the magnetic carrier has the resin portion and the core portion alternately, the contact area between the core portions is small, and the core portion The charge transfer between them cannot be performed smoothly, and the counter charge is hardly relaxed. For this reason, the counter charge remaining on the surface of the magnetic carrier acts as a force for pulling back the toner developed on the electrostatic latent image carrier, so that the toner is difficult to be developed and the density does not come out or density unevenness occurs. There is a case.

  On the other hand, in recent years, there has been an increasing demand for high quality image quality, and particularly in color image formation, the toner diameter is significantly reduced in order to realize high-definition images. However, in the reduction of the diameter by the conventional pulverization method, there is an extremely fine powder that does not appear in the particle size distribution because of excessive pulverization accompanying the reduction of the particle diameter. When such a toner is used, even if the magnetic carrier has a low specific gravity and reduces stress on the toner, the toner may be spent on the magnetic carrier, and the charge imparting property to the toner may be reduced. Further, since the flowability of the developer is lowered, the problems of density fluctuation and density unevenness become significant, and it is difficult to realize high quality image quality and high reliability at the same time. In order to simultaneously achieve high quality image quality and high reliability, it is necessary to sharpen the toner particle size distribution and reduce the particle size.

  That is, there is an urgent need to develop a magnetic carrier and a two-component developer that satisfy all of charge imparting property, durability, high developability, and high image quality.

JP-A-8-160671 JP 2006-337579 A JP 2007-57943 A

  An object of the present invention is to provide a magnetic carrier and a two-component developer that solve the above-described problems.

  That is, the object of the present invention is excellent in charge imparting property, does not generate fogging including a floating phenomenon, does not generate leakage or carrier adhesion even in long-term use, and has high image quality without density fluctuation or density unevenness. An object is to provide a magnetic carrier and a two-component developer capable of obtaining an image.

The present invention is a magnetic carrier having magnetic carrier particles in which pores of porous magnetic particles are filled with resin,
The magnetic carrier particle has a resin portion on the particle surface,
i) In a reflected electron image of the cross section of the magnetic carrier particle taken by a scanning electron microscope, a straight line that divides 72 equally from the reference point of the cross section of the magnetic carrier particle toward the surface of the magnetic carrier particle every 5 ° When (radius) is subtracted,
1) The number A of straight lines (radius) having a thickness of the resin of 0.3 μm or less measured from the distance from the surface of the magnetic carrier particles to the surface of the porous magnetic particles on the straight line (radius), 7 or more and 50 or less for 72 straight lines (radius),
2) The thickness of the resin measured from the distance from the surface of the magnetic carrier particle to the surface of the porous magnetic particle on the straight line (radius) is 1.5 μm or more and 5.0 μm or less. The number B is 7 or more and 35 or less for 72 straight lines (radius),
ii) In the reflected electron image of the cross section of the magnetic carrier particle taken by a scanning electron microscope, it passes through the reference point of the cross section of the magnetic carrier particle, and from the surface of the magnetic carrier particle to the surface every 36 °. When drawing a straight line (diameter) to divide equally,
1) The number of porous magnetic particle part regions having a length of 6.0 μm or more with respect to the total number of porous magnetic particle part regions having a length of 0.1 μm or more on the straight line (diameter) is 3. 0% to 35.0% by number,
2) The number of regions other than the porous magnetic particle portion having a length of 4.0 μm or more with respect to the total number of regions other than the porous magnetic particle portion having a length of 0.1 μm or more on the straight line (diameter). Is 1.0% by number or more and 15.0% by number or less.

  Furthermore, the present invention relates to a two-component developer comprising the magnetic carrier and a toner.

  By using the magnetic carrier and the two-component developer of the present invention, a high-definition image can be stably formed. Specifically, there is no occurrence of fogging including the floating phenomenon, and there is no occurrence of leakage or carrier adhesion even during long-term use, and a high-quality image free from density fluctuations and density unevenness can be obtained.

It is a schematic sectional drawing of the apparatus which measures the specific resistance of the magnetic carrier of this invention. (A) is a figure in the state of the blank before putting a sample, (b) is a figure which shows a state when a sample is put. It is an example of the figure of the SEM reflected electron image of a magnetic carrier particle cross section. It is the figure which cut out the magnetic carrier particle cross section from the image of FIG. 2, and binarized by image processing. It is the figure which showed typically the example which pulled the straight line (radius) for measuring the distance from the surface of the magnetic carrier particle in the cross section of a magnetic carrier particle to the surface of the porous magnetic particle. (B) is a schematic diagram of the numbered state. It is a figure which shows the result of having measured the distance from the surface of a magnetic carrier particle to the surface of a porous magnetic particle. In the cross section of the magnetic carrier particle, a region other than the porous magnetic particle portion having a length of 0.1 μm or more and a region other than the porous magnetic particle portion having a length of 0.1 μm or more are measured, and the length and number (number%) are measured. It is a figure which shows the measurement result of distribution of (). It is an example of the projection figure which visualized the reflected electrons mainly of the magnetic carrier at a magnification of 600 times. An example of the figure which shows the mode after the pre-process of the image processing of the projection figure which visualized the reflected electron mainly of the magnetic carrier. An example of the figure which shows the state which excluded the carrier particle of the image outer peripheral part from the magnetic carrier particle extracted from the projection figure which visualized the reflected electron mainly of the magnetic carrier. FIG. 10 is an example of a diagram illustrating a state in which particles to be subjected to image processing are further narrowed down by the particle diameter from the magnetic carrier particles extracted in the image of FIG. 9. An example of the figure explaining the state which extracted the metal oxide on a magnetic carrier particle. It is a figure which shows the measurement result of the specific resistance of the magnetic carrier used in Example 1 of this invention, and the porous magnetic particle used for it.

  The magnetic carrier of the present invention is a magnetic carrier having magnetic carrier particles in which pores of porous magnetic particles are filled with a resin, and a resin portion is present on the surface of the magnetic carrier particles.

As shown in FIG. 2 to be described later, the magnetic carrier according to the present invention has a magnetic field from the reference point of the cross section of the magnetic carrier particle in the reflected electron image of the cross section of the magnetic carrier particle taken by a scanning electron microscope. The following 1) and 2) are satisfied when a straight line (radius) that divides 72 equally every 5 ° toward the surface of the carrier particle is drawn (see FIG. 4).
1) The number A of straight lines (radius) having a thickness of the resin of 0.3 μm or less measured from the distance from the surface of the magnetic carrier particles to the surface of the porous magnetic particles on the straight line (radius), The number is 7 or more and 50 or less for 72 straight lines (radius).
2) The thickness of the resin measured from the distance from the surface of the magnetic carrier particle to the surface of the porous magnetic particle on the straight line (radius) is 1.5 μm or more and 5.0 μm or less. The number B is 7 or more and 35 or less for 72 straight lines (radius).

Further, in the reflected electron image of the cross section of the magnetic carrier particle taken by a scanning electron microscope, it passes through the reference point of the cross section of the magnetic carrier particle, and from the surface of the magnetic carrier particle to the surface every 36 °. When a straight line (diameter) to be equally divided is drawn, the following 1) and 2) are satisfied.
3) The number of porous magnetic particle part regions having a length of 6.0 μm or more with respect to the total number of porous magnetic particle part regions having a length of 0.1 μm or more on the straight line (diameter) is 3. It is 0 number% or more and 35.0 number% or less.
4) The number of regions other than the porous magnetic particle portion having a length of 4.0 μm or more with respect to the total number of regions other than the porous magnetic particle portion having a length of 0.1 μm or more on the straight line (diameter). However, it is important that it is 1.0 number% or more and 15.0 number% or less.

  In the magnetic carrier of the present invention, fog, carrier adhesion, leakage, density unevenness, and density fluctuation can be suppressed by controlling all of the above 1) to 4) within the above range.

  More preferably, the number A of straight lines (radius) is 11 or more and 35 or less with respect to 72 total straight lines (radius), and the number B of straight lines (radius) is 72 total straight lines (radius). The number of the porous magnetic particle portion regions having a length of 11 μm or more and 32 or less, and a length of 6.0 μm or more is the total number of the porous magnetic particle portion regions having a length of 0.1 μm or more. The number of areas other than the porous magnetic particle part having a length of 4.0 μm or more has a length of 0.1 μm or more, and is 5.0% by number or more and 20.0% by number or less with respect to the number. It is preferably 2.0% by number to 10.0% by number, and more preferably 2.0% by number to 6.0% by number with respect to the total number of regions other than the porous magnetic particle part. preferable.

  The present inventors infer the reason why the magnetic carrier of the present invention exhibits such excellent effects as follows.

  The number A of straight lines (radius) indicates the existence ratio of the portion where the distance from the surface of the porous magnetic particle to the surface of the magnetic carrier particle is close and the resin on the surface of the magnetic carrier particle is thin. The portion where the resin on the surface of the magnetic carrier particles is thin is considered to be a portion that attenuates the electric charge generated when the toner is frictionally charged.

  On the other hand, the number B of straight lines (radius) indicates the existence ratio of the portion where the distance from the surface of the porous magnetic particle to the surface of the magnetic carrier particle is long and the resin on the surface of the magnetic carrier particle is thick. A portion where the thickness of the resin on the surface of the magnetic carrier particles is thick is considered to be a portion which imparts a charge generated when the toner is frictionally charged.

  By controlling the number of straight lines (radius) A and the number of straight lines (radius) B within the above range with respect to all the straight lines (radius) indicating the opposite portions, the charge generated when the toner is frictionally charged. Can be controlled microscopically. Thus, it is considered that the rising property of frictional charging to the toner can be improved. As a result, even when images that consume a large amount of toner are output continuously, it is speculated that the newly supplied toner can be frictionally charged instantaneously, thereby suppressing the occurrence of fog. .

  Further, the portion where the resin thickness on the surface of the magnetic carrier particle is thin is a portion where counter charge having a polarity opposite to that of the toner generated on the surface of the magnetic carrier particle when the toner is developed is released to the developer carrier through the magnetic carrier. I think there is. Therefore, by controlling the number A of straight lines (radius) within the above range with respect to all straight lines (radius), it is considered that the occurrence of density unevenness can be suppressed by improving developability.

  In order to control the thin and thick portions of the resin on the surface of the magnetic carrier particles within the above range, it is important to widen the pore size of the porous magnetic particles, especially the pore size distribution on the surface of the porous magnetic particles. It is. Therefore, the pore size distribution on the surface of the porous magnetic particles can be controlled by controlling the particle size distribution of the temporarily calcined particles used as the raw material for the porous magnetic particles. Furthermore, when filling the resin, as will be described later, by controlling the viscosity of the resin varnish and the volatilization rate of the solvent at the time of filling, the portion where the resin thickness on the magnetic carrier particle surface is thin, and the thick portion, It becomes possible to control the range.

  In addition to the pore size distribution on the surface of the porous magnetic particles, the internal structure, that is, the connection of sintered primary particles derived from the starting material, is important for improving developability and suppressing leakage. As described above, the decrease in developability is considered to be caused by the counter charge having the opposite polarity to the toner generated on the surface of the magnetic carrier particles when the toner is developed pulling back the toner. Therefore, it is necessary to release the generated counter charge to the developer carrier via the magnetic carrier. The region where the generated counter charge moves is a porous magnetic particle portion region inside the magnetic carrier particle. In order for the electric charge to move smoothly in this region, it is important that the porous magnetic particle portion region inside the magnetic carrier particle has a specific length and number. This is also derived from the contact area between the sintered primary particles constituting the porous magnetic particles and the sinterability. As a result of extensive studies, the porous magnetic particle part region having a length of 6.0 μm or more has a sufficiently large contact area between the primary particles, so that the adhesion is greatly improved. For this reason, it was found that this is a region where the movement of the porous magnetic particle portion of the counter charge is facilitated. That is, the porous magnetic particle part region having a length of 6.0 μm or more on the straight line (diameter) from the surface to the surface of the magnetic carrier particle passing through the reference point of the cross section of the magnetic carrier particle is controlled within the above range. Thus, it is possible to suppress the occurrence of density unevenness due to the decrease in developability.

  However, since the porous magnetic particle part region having a length of 6.0 μm or more easily moves charges, it leaks through the spikes of the magnetic carrier formed on the developer carrying member, and electrostatic latent It is also an area where the electrostatic latent image on the image carrier is likely to be disturbed.

  Therefore, the existence of a region other than the porous magnetic particle portion that prevents leakage becomes important. Therefore, paying attention to the region other than the porous magnetic particle portion having a length of 4.0 μm or more, and controlling the abundance, it becomes possible to satisfy the contradictory characteristics of counter charge attenuation and leak prevention. It was. The region other than the porous magnetic particle portion having a length of 4.0 μm or more is considered to function as a region that hinders the movement of charges in the porous magnetic particle portion. Since the development area is under a high electric field, the gap between the porous magnetic particle part areas is narrow and the leakage current is small at the part where the length of the area other than the porous magnetic particle part is less than 4.0 μm. It penetrates in areas other than the porous magnetic particle part. As a result, it is insufficient to control charge flow.

  When the number of straight lines (radius) A is less than 7, it indicates that there are few portions where the thickness of the resin is thin as measured from the distance from the surface of the porous magnetic particle having a low specific resistance to the surface of the magnetic carrier particle. ing. In this case, there are few parts that attenuate the charge generated when the toner is frictionally charged, and there are many parts that give the charge. Therefore, although the absolute value of the frictional charge amount is large, the rising property of the charge is slowed down, and the fogging is rather reversed. May occur. Further, when the toner is developed, counter charges having a polarity opposite to that of the toner generated on the surface of the magnetic carrier particles are difficult to be released to the developer carrying member, and density develops in some cases because developability deteriorates. Further, due to the decrease in developability, the spending of extremely small particles also proceeds, and image defects such as a decrease in image density and white spots accompanying a decrease in developability may occur.

  In addition, the number of straight lines (radius) A being more than 50 indicates that there are many portions where the thickness of the resin measured from the distance from the surface of the porous magnetic particle having a low specific resistance to the surface of the magnetic carrier particle is thin. Show. In this case, when the toner is developed, counter charges having a polarity opposite to that of the toner remaining on the surface of the magnetic carrier particles are easily released to the developer carrying member, and the developability is improved. On the other hand, there are few parts that impart charge when frictionally charged with the toner, and there are many parts that attenuate the charge, so that the rising property of the charge is improved, but the absolute value of the triboelectric charge amount becomes small and fogging occurs. May occur. In addition, leakage may occur due to the low resistance of the magnetic carrier.

  The fact that the number of straight lines (radius) B is less than 7 indicates that there are few portions where the thickness of the resin measured from the distance from the surface of the porous magnetic particle having a low specific resistance to the surface of the magnetic carrier is large. Yes. In this case, when the toner is developed, counter charges having a polarity opposite to that of the toner remaining on the surface of the magnetic carrier particles are easily released to the developer carrying member, and the developability is improved. On the other hand, since there are few portions that apply the charge generated when the toner is frictionally charged and there are many portions that attenuate the charge, the absolute value of the triboelectric charge amount becomes small and fogging may occur. Further, since the strength of the porous magnetic particles is low and is easily destroyed, even when a large number of sheets are printed, the broken magnetic carrier may adhere to the toner image. In addition, since the degree of unevenness on the surface of the magnetic carrier is increased, toner spent may easily occur.

  Further, the number of straight lines (radius) B being greater than 35 indicates that there are many portions where the thickness of the resin measured from the distance from the surface of the porous magnetic particle having a low specific resistance to the surface of the magnetic carrier is thick. Show. In this case, there are few portions that leak the charge generated when the toner is frictionally charged, and there are many portions that impart the charge, so the absolute value of the triboelectric charge amount becomes large, but the rising property of charging deteriorates. It may cause fogging that causes surrounding phenomena. Further, when the toner is developed, counter charges having a polarity opposite to that of the toner generated on the surface of the magnetic carrier particles are difficult to be released to the developer carrying member, and density develops in some cases because developability deteriorates. Further, due to the decrease in developability, the spent of extremely small particles also advances, and image defects such as a decrease in image density and white spots may occur.

  When the number of porous magnetic particle part regions having a length of 6.0 μm or more is less than 3.0% by number, the charge is not moved so much and static electricity on the electrostatic latent image carrier due to the leakage is prevented. Disturbing the electrostatic latent image can be suppressed. On the other hand, when the toner is developed, it becomes difficult to attenuate counter charges having a polarity opposite to that of the toner generated on the surface of the magnetic carrier particles, and developability is lowered. Therefore, density unevenness may occur.

  Further, when the number of porous magnetic particle part regions having a length of 6.0 μm or more is more than 30.0% by number, the counter charge on the surface of the magnetic carrier particles is attenuated when the toner is developed, Since the developability is improved, the occurrence of density unevenness can be suppressed. On the other hand, since the movement of the electric charge is easy, there is a case where leakage occurs through the rise of the magnetic carrier formed on the developer carrier, and the electrostatic latent image on the electrostatic latent image carrier is disturbed.

  When the number of regions other than the porous magnetic particle portion having a length of 4.0 μm or more is less than 1.0% by number, counter charges having a polarity opposite to that of the toner are easily released to the developer carrying member, Since the developability is improved, the occurrence of density unevenness can be suppressed. On the other hand, since the movement of the electric charge is easy, there is a case where leakage occurs through the rise of the magnetic carrier formed on the developer carrier, and the electrostatic latent image on the electrostatic latent image carrier is disturbed. In addition, it is likely that the resin in the pores of the porous magnetic particles is insufficient. As a result, the physical strength is reduced, and during long-term durability, part of the magnetic carrier is destroyed, and fogging may occur due to the occurrence of carrier adhesion and a decrease in charge imparting ability.

  When the number of regions other than the porous magnetic particle portion having a length of 4.0 μm or more is more than 15.0% by number, the movement of charges is suppressed, so Disturbing the electrostatic latent image can be suppressed. On the other hand, when the toner is developed, counter charges having a polarity opposite to that of the toner remaining inside the magnetic carrier particles are difficult to be released to the developer carrying member, and density develops in some cases because developability deteriorates. In addition, the specific gravity difference is increased in the magnetic carrier particles, the fluidity of the magnetic carrier is lowered, and the density unevenness may become remarkable.

  In the present invention, the resin part is present on the surface of the magnetic carrier particle. However, in order to control the amount of resin on the surface of the magnetic carrier particle that affects the charge rising property and developability, the resin part is made of resin. It is preferable that the porous magnetic particles after being filled with are coated with a resin. As a method of forming the resin part on the surface of the core particle, in addition to the above method, there is a method of attaching or coating the resin on the particle surface when filling the resin in the pores of the porous magnetic particles. Can be mentioned. Note that the resin portion does not necessarily exist so as to be completely covered.

  It is preferable to further coat the surface of the magnetic carrier particles with a resin because the resin thickness on the surface of the magnetic carrier can be controlled more precisely. In addition, the surface is coated with resin from the viewpoint of controlling the releasability of the toner from the surface of the magnetic carrier particles, the contamination of the toner and external additives on the surface of the magnetic carrier particles, the ability to impart charge to the toner and the magnetic carrier resistance It is preferable to do.

Also, in the reflected electron image of the magnetic carrier particles when the acceleration voltage is 2.0 kV, taken by a scanning electron microscope,
It is preferable that the ratio of magnetic carrier particles having an area ratio S ₁ obtained from the following formula (1) of 0.5 area% or more and 8.0 area% or less is 80 number% or more in the magnetic carrier.
S ₁ = (total area of high luminance portion derived from porous magnetic particles on one magnetic carrier particle / total projected area of the particle) × 100 (1)
If the area S ₁ is using the magnetic carrier particles satisfying the above range, the development site, by since the low resistance to magnetic brush acts as an electrode (electrode effect), the force of the electric field acting on the toner is increased . As a result, the toner is likely to fly and the developability is considered to be improved. In addition, since the area of the high-luminance portion derived from the porous magnetic particles is moderately controlled, the counter charge after the toner flight on the surface of the magnetic carrier particles can be quickly attenuated, and the developability is further improved. .

Further, in the magnetic carrier, the average ratio Av ₁ of the total area of the high luminance portion derived from the porous magnetic particles on the magnetic carrier particles with respect to the total projected area of the magnetic carrier is 0.5 area% or more and 8.0 area%. The following is preferable. More preferably, it is 2.0 area% or more and 5.5 area% or less. When the average ratio Av ₁ is within the above range, the counter charge can be quickly attenuated, the developability can be improved, and the occurrence of density unevenness can be suppressed.

Further, the magnetic carrier preferably has an average ratio Av ₂ obtained from the following formula (2) of 10.0 area% or less. A magnetic carrier having an Av ₂ value within this range can suppress leakage to the latent image latent image carrier.
Av ₂ = (High brightness portion derived from the porous magnetic particles on the magnetic carrier particle, the total area of the portion having a domain area of 6.672 μm ² or more / derived from the porous magnetic particle of the magnetic carrier particle Total area of high brightness part) × 100 (2)
When satisfying the above S ₁ , Av ₁ and Av ₂ , particularly, stable developability is obtained over a long period of time, and more remarkable effects are obtained with respect to density unevenness and leakage suppression.

  The portion having high luminance derived from the porous magnetic particles is high in luminance (the image looks white and bright) in the image (FIG. 7) in which reflected electrons are mainly visualized under a predetermined acceleration voltage of the scanning electron microscope. ) Portion, and refers to the portion where the resin thickness is thin on the surface of the magnetic carrier particles.

  In the magnetic carrier of the present invention, by controlling the ratio and area distribution of the area of high brightness derived from the porous magnetic particles on the surface of the magnetic carrier particle, the counter charge due to the toner is attenuated, and conversely the leak Can be prevented. In addition, by having many portions to which frictional charging is applied, the rising of frictional charging can be accelerated.

  Furthermore, in the present invention, when the electric field strength just before breakdown is 1300 V / cm or more and 5000 V / cm or less in the specific resistance measurement method to be described later of the magnetic carrier, a higher triboelectric charge can be obtained and fogging is good. And improving the developability.

  In the magnetic carrier of the present invention, in order to cause breakdown at a desired electric field strength, it is important to control the distribution of the thin and thick portions of the resin on the surface of the magnetic carrier. As a result, when an electric field is not applied, it is possible to increase the triboelectric chargeability to the toner, and in the development region where the electric field is applied, the resistance of the magnetic carrier rapidly decreases and can act as an electrode effect. Yes.

  The porous magnetic particles of the present invention can be produced by the following steps.

  As the material of the porous magnetic particles, magnetite or ferrite is preferable. Furthermore, it is more preferable that it is a ferrite because the porous structure of the porous magnetic particles can be controlled and the resistance can be adjusted.

Ferrite is a sintered body represented by the following general formula.
(M1 ₂ O) _x (M2O) _y (Fe ₂ O ₃ ) _z
(In the formula, M1 is a monovalent metal, M2 is a divalent metal, and when x + y + z = 1.0, x and y are 0 ≦ (x, y) ≦ 0.8, respectively, and z is 0.2 <z <1.0.)
In the formula, as M1 and M2, it is preferable to use one or more kinds of metal atoms selected from the group consisting of Li, Fe, Mn, Mg, Sr, Cu, Zn, Ni, Co, and Ca.

  Mn-based, containing Mn element, from the viewpoint of easily controlling the growth rate of ferrite crystals and suitably controlling the specific resistance of porous magnetic particles in order to make the porous structure and the uneven surface of the particles suitable. Ferrite, Mn—Mg ferrite, Mn—Mg—Sr ferrite, and Li—Mn ferrite are more preferable.

  Below, the manufacturing process in the case of using a ferrite as a porous magnetic 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, metal element oxides, metal element hydroxides, metal element oxalates, metal element 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 air 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 make the raw material ferrite. For firing, for example, the following furnace is used. Burner-type firing furnace, rotary-type firing furnace, 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. For example, the following are mentioned. Crusher, hammer mill, ball mill, bead mill, planetary mill, Giotto mill.

  The volume-based 50% particle size (D50) of the finely pulverized calcined ferrite is 0.5 μm or more and 5.0 μm or less, and the volume-based 90% particle size (D90) is 2.0 μm or more and 7.0 μm or less. It is preferable. Moreover, it is preferable that D90 / D50 which shows the particle size distribution of the finely ground product of this calcined ferrite is 1.5 or more and 10.0 or less. By doing so, it becomes easy to control the number of the porous magnetic particle part regions and the number of the regions other than the porous magnetic particle parts within a preferable range. In addition, the pore size distribution on the surface of the porous magnetic particles can be easily controlled.

In order to make the finely pulverized product of the calcined ferrite have the above particle size distribution, for example, it is preferable to control the material of balls and beads used in the ball mill and the bead mill and the operation time. Specifically, in order to reduce the particle size of the calcined ferrite, a ball having a high specific gravity may be used or the pulverization time may be increased. Moreover, in order to widen the particle size distribution of the calcined ferrite, it can be obtained by using balls having a high specific gravity and shortening the pulverization time. In addition, by mixing a plurality of calcined ferrites having different particle diameters, a calcined ferrite having a wide distribution can be obtained. The material for the balls and beads is not particularly limited as long as a desired particle size and distribution can be obtained. For example, the following can be mentioned. Glass such as soda glass (specific gravity 2.5 g / cm ³ ), sodaless glass (specific gravity 2.6 g / cm ³ ), high specific gravity glass (specific gravity 2.7 g / cm ³ ), quartz (specific gravity 2.2 g / cm ³ ) ³ ), titania (specific gravity 3.9 g / cm ³ ), silicon nitride (specific gravity 3.2 g / cm ³ ), alumina (specific gravity 3.6 g / cm ³ ), zirconia (specific gravity 6.0 g / cm ³ ), steel ( Specific gravity 7.9 g / cm ³ ), stainless steel (specific gravity 8.0 g / cm ³ ). Among these, alumina, zirconia, and stainless steel are preferable because of excellent wear resistance.

  The particle size of the ball or bead is not particularly limited as long as a desired particle size / distribution is obtained. For example, a ball having a diameter of 5 mm or more and 60 mm is preferably used. Further, beads having a diameter of 0.03 mm or more and less than 5 mm are preferably used.

  In the ball mill and bead mill, the wet type is higher than the dry type in that the pulverized product does not rise in the mill and the pulverization efficiency is higher. For this reason, the wet type is more preferable than the dry type.

Process 4 (granulation process):
To the finely pulverized product of calcined ferrite, a dispersant, water, a binder and, if necessary, a pore adjuster are added. Examples of the pore adjuster include a foaming agent and resin fine particles. For example, polyvinyl alcohol is used as the binder. In Step 3, when wet pulverization is performed, it is necessary to consider water contained in the ferrite slurry.
The obtained ferrite slurry is dried and granulated using a spray dryer in a heated atmosphere at a temperature of 100 ° C. or higher and 200 ° C. or lower.
The spray dryer is not particularly limited as long as a desired particle size can be obtained. For example, a spray dryer can be used.

Process 5 (main baking process):
Next, the granulated product is fired at a temperature of 800 ° C. to 1300 ° C. for 1 hour to 24 hours. The temperature is more preferably 1000 ° C. or higher and 1200 ° C. or lower. By shortening the temperature raising time and lengthening the temperature lowering time, the crystal growth rate can be controlled and a desired porous structure can be obtained. The holding time for the firing temperature is preferably 3 hours or more and 5 hours or less in order to obtain a desired porous structure. In order to control the structure of the porous magnetic particle part region in the cross section of the magnetic carrier particles, it is preferable to control the firing temperature and firing time within the above ranges.
By raising the firing temperature or lengthening the firing time, the firing of the porous magnetic particles proceeds, and as a result, the area ratio of the porous magnetic particle portion region increases and the length also increases.

Process 6 (screening 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 size (D50) of the porous magnetic particles is 18.0 μm or more and 58.0 μm or less, which improves the triboelectric chargeability to the toner and satisfies the image quality of the halftone part. This is more preferable for suppressing fogging and preventing carrier adhesion to the image.

  Furthermore, the magnetic carrier particles of the present invention can contain a resin in at least a part of the pores of the porous magnetic particles, and can be present in the vicinity of the surface of the magnetic carrier to control the thickness of the resin. is important. Porous magnetic particles may have low physical strength depending on the size and number of internal pores. However, by containing a resin in the pores of the porous magnetic particles, the physical strength as magnetic carrier particles can be increased. Can be increased.

  When the resin is contained in the porous magnetic particles, the resin may be filled up to the hole in the back of the porous magnetic particle, or the resin may be filled only in the hole on the surface of the porous magnetic particle.

  The resin that fills the pores of the porous magnetic particles is not particularly limited, and either a thermoplastic resin or a thermosetting resin may be used, but the resin has a high affinity for the porous magnetic particles. preferable. When a resin having high affinity is used, the surface of the porous magnetic particle can be easily covered with the resin at the same time when the resin is filled into the pores of the porous magnetic particle.

  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 this 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.

  Further, a resin obtained by modifying these resins may be used. Of these, fluorine-containing resins such as polyvinylidene fluoride resin, fluorocarbon resin, perfluorocarbon resin or solvent-soluble perfluorocarbon resin, modified silicone resin or silicone resin are preferred because of their high affinity for porous magnetic particles.

  Among the above resins, thermosetting resins are preferable because the strength of the magnetic carrier can be increased. Among these, a silicone resin is preferable because it can reduce the adhesion between the magnetic carrier particles and the toner and can improve developability.

  For example, the following are mentioned as a commercial item. Among silicone resins, KR271, KR255, and KR152 manufactured by Shin-Etsu Chemical Co., Ltd., and SR2400, SR2405, SR2410, and SR2411 manufactured by Toray Dow Corning. 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 resin to be filled can be filled according to the pore volume of the porous magnetic particles. The amount of the filled resin is preferably 5.0 to 20.0 parts by mass with respect to the porous magnetic particles. More preferably, it is 7.0 to 15.0 parts by mass.

  The method of filling the pores of the porous magnetic particles with the resin is not particularly limited, but a method of diluting the resin in a solvent, adding this to the pores of the porous magnetic particles, and removing the solvent can be employed. In particular, a method of filling the pores of the porous magnetic particles with a resin solution in which a resin and a solvent are mixed under reduced pressure, and removing the solvent by degassing or heating is preferable. 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. As a method of filling the pores of the porous magnetic particles with the resin, the resin solution is impregnated with the porous magnetic particles by a coating method such as dipping, spraying, brushing, and fluidized bed, and then the solvent is volatilized. The method of letting it be mentioned.

  To adjust the resin thickness on the surface of the magnetic carrier particles, adjust the resin concentration in the resin solution to be filled, the temperature inside the filling device when filling, the temperature when removing the solvent, the number of resin filling steps Etc.

  The amount of the resin in the resin solution is preferably 6% by mass or more and 25% by mass or less. When a resin solution having a resin amount greater than 25% by mass is used, it is difficult to uniformly fill the resin solution to the back of the pores of the porous magnetic particles because the viscosity is high. On the other hand, if the amount is less than 6% by mass, the amount of resin is small, the adhesion of the resin to the porous magnetic particles is low, and it takes time to remove the solvent, which may result in uneven filling. The resin thickness on the surface of the magnetic carrier particles can be reduced by diluting the resin to be filled and filling with a solution having a low concentration, and the resin thickness on the surface of the magnetic carrier particles can be reduced by filling with a solution having a high concentration. The thickness can be increased. By appropriately selecting solutions having different concentrations and filling them in a plurality of times, a magnetic carrier having a suitable resin thickness on the surface can be obtained.

  Moreover, the temperature of the resin solution to be filled is lowered and the solvent is evaporated while slowly stirring while raising the temperature, whereby the resin can be thinly filled on the surface of the magnetic carrier particles. On the other hand, by elevating the temperature of the resin solution to be filled and evaporating while stirring, the resin can be filled thickly while appropriately leaving a thin portion of the resin on the surface of the magnetic carrier particles. In the filling step, it is possible to obtain magnetic carrier particles having a suitable resin thickness on the surface by performing a filling step at different temperatures.

  As described above, by repeating the resin filling step in multiple stages, it is possible to control the thin and thick portions of the resin on the surface of the magnetic carrier particles. At this time, resin solutions having the same concentration may be used, or different resin solutions may be used.

  Moreover, it is preferable to further coat the surface of the porous magnetic particles filled with the resin with the resin. Further coating allows the resin thickness on the magnetic carrier surface to be controlled more precisely. In addition, the surface is coated with resin from the viewpoint of controlling the releasability of the toner from the surface of the magnetic carrier particles, the contamination of the toner and external additives on the surface of the magnetic carrier particles, the ability to impart charge to the toner and the magnetic carrier resistance It is preferable to do.

  The method for coating the particle surface 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 that can appropriately expose the porous magnetic particles on the surface of the magnetic carrier particles is more preferable.

  The amount of the resin to be coated is suitably 0.1 parts by mass or more and 5.0 parts by mass or less with respect to 100 parts by mass of the particles before coating, so that the porous magnetic part on the surface of the magnetic carrier is appropriately exposed on the surface. Can be preferred.

  The resin to be coated can be used alone or in combination. The resin to be coated may be the same as or different from the resin used for filling, and may be a thermoplastic resin or a thermosetting resin. In addition, a curing agent or the like can be mixed with a thermoplastic resin and cured for use. In particular, it is preferable to use a resin having higher releasability.

  Examples of the thermoplastic resin include the thermoplastic resin used in the above-described filling resin.

  As this thermosetting resin, the thermosetting resin used for the filling resin mentioned above is mentioned. Of the above-described resins, silicone resins are particularly preferable. As the silicone resin, conventionally known silicone resins can be used.

  Furthermore, the coating resin may contain particles having conductivity, particles or materials having charge controllability.

  Examples of the conductive particles include carbon black, magnetite, graphite, zinc oxide, and tin oxide. The addition amount is preferably 0.1 parts by mass or more and 10.0 parts by mass or less with respect to 100 parts by mass of the coating resin in order to adjust the resistance of the magnetic carrier.

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

  Next, the toner contained in the two-component developer of the present invention together with a magnetic carrier will be described.

  The toner in the present invention preferably has a weight average particle diameter (D4) of 3.0 μm or more and 8.0 μm or less, more preferably 4.5 μm or more and 6.5 μm or less. When the weight average particle diameter (D4) of the toner is in the above range, good dot reproducibility of the electrostatic latent image on the image carrier can be obtained.

  The toner in the present invention preferably has an average circularity of 0.940 to 1.000. When the average circularity of the toner is within the above range, the releasability between the carrier and the toner is good. The average circularity is a circularity measured by a flow type particle image measuring apparatus having a visual field of 512 × 512 pixels (0.37 μm × 0.37 μm per pixel), and is 0.200 or more. The analysis is performed by dividing 800 into a circularity range of 000 or less. Note that the particles to be measured have a diameter equivalent to a circle equivalent diameter of 1.985 μm or more and less than 39.69 μm.

  In the toner according to the present invention, the proportion of particles having an equivalent circle diameter of 0.60 μm or more and 2.00 μm or less (hereinafter also referred to as small particle toner) measured by the flow type particle image measuring device is 25% by number or less. It is preferably 10% by number or less. When the ratio of the small particle toner is 30% by number or less, the mixing property of the developer and the toner in the developing device is good and the adhesion of the small particle toner to the magnetic carrier can be reduced. It is possible to maintain a stable charge-imparting property for a long period of time without lowering.

  As a method for producing the toner particles of the toner in the present invention, for example, a pulverization method in which a binder resin and a colorant are melt-kneaded and the kneaded product is cooled and then pulverized and classified; the binder resin and the colorant in a solvent Suspension granulation method in which toner particles are obtained by introducing a solution dissolved or dispersed in an aqueous medium into a suspension granulation and removing the solvent; a monomer in which a colorant or the like is uniformly dissolved or dispersed in the monomer A suspension polymerization method in which a composition is dispersed in a continuous layer (for example, an aqueous phase) containing a dispersion stabilizer, and a polymerization reaction is performed to produce toner particles; a polymer dispersant is dissolved in an aqueous organic solvent, and a monomer Dispersion polymerization method in which toner particles are obtained by polymerizing the polymer to obtain toner particles; emulsion polymerization method in which toner particles are directly polymerized in the presence of a water-soluble polar polymerization initiator; at least polymer fine particles and colorant fine particles Agglomerate There are; emulsion aggregation method obtained through the aging step to cause fusion between particles of the process and the fine particles agglomerate to form a particulate aggregate Te.

  In the present invention, a toner with reduced small particles is preferable. In particular, in a toner obtained by a pulverization method, small particles can be reduced by modifying the surface of the toner by mechanical or thermal treatment after pulverization or pulverization / classification.

  In addition, a toner produced by an emulsion aggregation method is preferable in order to have a sharp particle size distribution, suitable for reducing the size, and suppressing the generation of small particles as much as possible. Since the proportion of small particles is small, the spent on the magnetic carrier hardly occurs even in long-term use. Therefore, the triboelectric charge imparting property does not change over a long period of time, and stable charge application is possible, and an image having no density fluctuation can be obtained.

  Hereinafter, a procedure for producing a toner by the emulsion aggregation method will be described.

  As the polymer used for the polymer fine particles, known resins are used. Among them, the polymer preferably used for the polymer fine particles is a resin having a styrene copolymer and a polyester unit. .

  The polymer fine particles may be fine particles that are emulsified and dispersed in an aqueous solvent. The polymer fine particles obtained by emulsion polymerization of a polymerizable monomer or an emulsion obtained by emulsifying and dispersing a polymer that has been polymerized in advance. Fine particles are preferred.

  As the surfactant used in emulsion polymerization and emulsion dispersion, at least one selected from known cationic surfactants, anionic surfactants, and nonionic surfactants can be used. Two or more of these surfactants may be used in combination. In particular, it is preferable to mainly use an anionic surfactant.

  As polymerization initiators for polymerization, persulfates such as potassium persulfate, sodium persulfate and ammonium persulfate, and redox initiators combining these persulfates as a component with a reducing agent such as acidic sodium sulfite, Water-soluble polymerization initiators such as hydrogen peroxide, 4,4′-azobiscyanovaleric acid, t-butyl hydroperoxide, cumene hydroperoxide, and ferrous salts containing these water-soluble polymerizable initiators as one component Redox initiator systems, benzoyl peroxide, 2,2′-azobis-isobutyronitrile, etc. in combination with other reducing agents are used. These polymerization initiators may be added to the polymerization system before, simultaneously with the addition of the monomer, or after the addition, and these addition methods may be combined as necessary.

  Moreover, in the case of superposition | polymerization, a well-known chain transfer agent can be used as needed. The chain transfer agent may be used alone or in combination of two or more. Further, a crosslinking agent may be used for adjusting the molecular weight of the polymer.

  As the colorant used for the colorant fine particles, known dyes and / or pigments are used. Although the pigment alone may be used, it is more preferable from the viewpoint of the image quality of a full-color image to improve the sharpness by using a dye and a pigment together. These colorants can be obtained by emulsifying and dispersing the fine particles forming the toner particles by the emulsion aggregation method using the surfactant.

  Examples of the colorant include the following. Examples of the black colorant include carbon black; magnetic substance; those adjusted to black using a yellow colorant, a magenta colorant, and a cyan colorant. Examples of the magenta colorant include condensed azo compounds, diketopyrrolopyrrole compounds, anthraquinones, quinacridone compounds, basic dye lake compounds, naphthol compounds, benzimidazolone compounds, thioindigo compounds, and perylene compounds.

  Examples of cyan colorants include C.I. I. Pigment Blue 1, 2, 3, 7, 15: 2, 15: 3, 15: 4, 16, 17, 60, 62, 66; I. Bat Blue 6, C.I. I. Acid Blue 45, and a copper phthalocyanine pigment in which 1 to 5 phthalimidomethyls are substituted on the phthalocyanine skeleton. Examples of the colorant for yellow include condensed azo compounds, isoindolinone compounds, anthraquinone compounds, azo metal compounds, methine compounds, and allylamide compounds. The amount of the colorant used is preferably 0.1 parts by mass or more and 30.0 parts by mass or less, more preferably 0.5 parts by mass or more and 20.0 parts by mass or less, with respect to 100 parts by weight of the binder resin. It is particularly preferably 3.0 parts by mass or more and 15.0 parts by mass or less.

  In the emulsion aggregation method, fine particles obtained by emulsifying and dispersing wax in addition to the polymer fine particles and the colorant fine particles may be used.

  Examples of the wax particularly preferably used in the present invention include aliphatic hydrocarbon waxes and esterified products which are esters of fatty acids and alcohols.

  The wax has a maximum endothermic peak peak temperature in the range of 30 ° C. or higher and 200 ° C. or lower in the endothermic curve at the time of temperature rise measured with a differential scanning calorimetry (DSC) apparatus, 140 ° C. It is preferable to be in the range of ℃ or less. More preferably, it is in the range of 65 to 120 ° C, and particularly preferably in the range of 70 to 105 ° C.

  When the peak temperature of the maximum endothermic peak of the wax is in the range of 45 to 140 ° C., an appropriate fine dispersibility in the toner can be achieved, and a toner having both blocking properties and low-temperature fixability can be obtained.

  The number average particle size of these emulsified and dispersed fine particles (polymer fine particles, colorant fine particles, wax fine particles) is 0.05 μm in order to control the aggregation rate and to obtain the desired particle size of the toner particles. The thickness is preferably 3.00 μm or less, more preferably 0.10 μm or more and 1.00 μm or less, and particularly preferably 0.10 μm or more and 0.50 μm or less. The number average particle diameter can be measured using a fine particle measuring apparatus (for example, UPA manufactured by Microtrack).

  These emulsified and dispersed fine particles can be aggregated by adding an aggregating agent such as an electrolyte to the emulsified dispersion while stirring as necessary, and further heating to form fine particle aggregates. The flocculant used may be either an organic salt or an inorganic salt, but a metal salt is preferably used. When adding an aggregating agent, it is preferable to keep the temperature of the emulsified dispersion at 40 ° C. or lower in order to moderate the aggregation rate. Thereafter, the mixture is heated to produce aggregated particles. The stirring can be performed using a normal known stirring device.

  The particle size growth by the aggregation process is carried out until substantially toner-sized particles are obtained, but can be controlled by adjusting the pH and temperature of the dispersion. The pH value varies depending on the type and amount of the emulsifier used and the target particle size of the toner, but cannot be uniquely defined. However, when an anionic surfactant is mainly used, the pH is usually 2 or more, 6 or less, When a surfactant is used, a pH of about 8 or more and 12 or less is usually used.

  Next, the fusion process will be described.

  The toner can be obtained through a fusing step of causing fusing between the fine particles in the fine particle aggregate after the aggregating step of forming the fine particle aggregate. That is, following the agglomeration step, in order to increase the stability of the fine particle aggregate obtained in the agglomeration step, the agglomerated particles are held for a predetermined time at a temperature higher than the glass transition temperature (Tg) of the polymer primary particles. Fusion can occur between them. The fusing step can be performed using a stirrer similar to the stirrer used in the aggregation step. By performing this step, it is possible to prevent the generation of small particles simultaneously with particles having a desired toner particle diameter.

  The toner particles obtained through each step are solid-liquid separated according to a known method, and the toner particles are collected. Next, the collected toner particles are washed and dried as necessary.

  In addition, a known charge control agent can be used for the toner in order to stabilize its chargeability. The charge control agent varies depending on the type of the charge control agent and the physical properties of other toner constituent materials, but is preferably contained in an amount of 0.1 parts by mass or more and 10.0 parts by mass or less per 100 parts by mass of the resin in the toner. More preferably, it is contained in an amount of 0.1 parts by mass or more and 5.0 parts by mass or less. One or more of various toners can be used depending on the type and use of the toner. Negatively chargeable charge control agents include salicylic acid metal compounds, naphthoic acid metal compounds, dicarboxylic acid metal compounds, polymer compounds having sulfonic acid or carboxylic acid in the side chain, boron compounds, urea compounds, silicon compounds, calixarene Is mentioned. The charge control agent may be added internally or externally to the toner particles.

In particular, the charge control agent is preferably an aromatic metal carboxylic acid compound that is colorless, has a high toner charging speed, and can stably maintain a constant charge amount.
In the present invention, for the purpose of improving the performance of the toner, external additives such as a fluidizing agent, a transfer aid, and a charge stabilizer can be mixed with the toner particles using a mixer such as a Henschel mixer. .

  As the fluidizing agent, any fluidizing agent can be used as long as it can increase the fluidity before and after the addition.

  Further, the toner preferably contains fine particles having a number average particle diameter of 80 nm or more and 300 nm or less in order to maintain high image quality and high stability. This is because by exhibiting the spacer effect on the toner surface, the toner spent on the magnetic carrier can be further suppressed and the charging stability at the time of toner replenishment can be maintained for a long time. In addition, since the stress resistance of the toner in the developing device increases, the toner in the developing device can maintain the initial state, and the difference in chargeability from the replenished toner is reduced, resulting in a result. This is because an image with less fog can be obtained. This is preferably used in combination with the external additive. As the fine particles having a number average particle diameter of 80 nm or more and 300 nm or less, any fine particles having a number average particle diameter in the above range can be used. For example, resin powders such as vinyl resin fine particles, phenol resin fine particles, melamine resin fine particles, vinylidene fluoride fine powder, polytetrafluoroethylene fine powder; titanium oxide fine powder, alumina fine powder, wet process silica, dry process silica Such finely divided silica; treated silica obtained by subjecting them to surface treatment with a silane compound, an organosilicon compound, a titanium coupling agent, silicone oil, or the like. The content of the fine particles is preferably 0.2 parts by mass or more and 5.0 parts by mass or less, more preferably 1.0 parts by mass or more and 3.0 parts by mass or less with respect to 100 parts by mass of the toner particles. . The number average particle diameter can be measured using a fine particle measuring device (for example, UPA manufactured by Microtrac).

  When the toner and the magnetic carrier are mixed and used as a two-component developer in the developing device, the mixing ratio of the toner and the magnetic carrier is 0.04 parts by mass of the toner with respect to 1 part by mass of the magnetic carrier. As mentioned above, it is preferable to use in 0.20 mass part or less. More preferably, they are 0.05 mass part or more and 0.15 mass part or less.

  The measurement of various physical properties according to the present invention will be described below.

<Volume distribution standard 50% particle diameter (D50) of magnetic carrier and porous magnetic particles, volume distribution standard 50% particle diameter (D50) of finely pulverized calcined ferrite (D50), volume distribution standard 90% particle diameter (D90) ) Measuring method>
The particle size distribution was measured with a laser diffraction / scattering particle size distribution measuring apparatus “Microtrack MT3300EX” (manufactured by Nikkiso Co., Ltd.).

  In the measurement of the 50% particle size (D50) based on the volume distribution and the 90% particle size (D90) based on the volume distribution of the finely pulverized product of the calcined ferrite, the sample circulator “Sample Delivery Control (SDC)” for wet use is used. (Nikkiso Co., Ltd.) was installed. The calcined ferrite (ferrite slurry) was dropped into the sample circulator so as to have a measured concentration. The flow rate was 70%, the ultrasonic output was 40 W, and the ultrasonic time was 60 seconds.

The measurement conditions are as follows.
SetZero time: 10 seconds Measurement time: 30 seconds Number of measurements: 10 times Solvation index: 1.33
Particle refractive index: 2.42
Particle shape: Non-spherical constant upper limit: 1408 μm
Measurement lower limit: 0.243 μm
Measurement environment: 23 ° C / 50% RH
The volume distribution standard 50% particle size (D50) of the magnetic carrier and the porous magnetic particles was measured by mounting a sample feeder “One-shot dry sample conditioner Turbotrac” (manufactured by Nikkiso Co., Ltd.) for dry measurement. . As the supply conditions of Turbotrac, a dust collector was used as a vacuum source, the air volume was about 33 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, is obtained. Control and analysis are performed using attached software (version 10.3.3-202D).

The measurement conditions are as follows.
SetZero time: 10 seconds Measurement time: 10 seconds Number of measurements: 1 time Particle refractive index: 1.81
Particle shape: Non-spherical measurement upper limit: 1408 μm
Measurement lower limit: 0.243 μm
Measurement environment: 23 ° C / 50% RH
<Measurement Method of Length of Porous Magnetic Particle Part Region in Section of Magnetic Carrier Particle, Length of Region Excluding Porous Magnetic Particle Part, and Measurement Method of Area Ratio of Porous Magnetic Particle Part Region>
For cross-section processing of the magnetic carrier particles, a focused ion beam processing observation apparatus (FIB), FB-2100 manufactured by Hitachi High-Technologies Corporation was used. A carbon paste is applied on an FIB sample stage (metal mesh), a small amount of magnetic carrier particles are fixed on the FIB sample stand so as to exist 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 particles used as samples are magnetic carrier particles having D50 × 0.9 ≦ Dmax ≦ D50 × 1.1 as the maximum diameter Dmax 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 of (radius) r). Become). 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 the cross-sectional observation of the magnetic carrier particles of the present invention, the metal oxide part derived from the porous magnetic particle part region is bright (high brightness, white), and the region other than the porous magnetic particle part is dark (low brightness). Therefore, an image with a large contrast difference can be obtained. Specifically, observation was performed under the following conditions using a scanning electron microscope (SEM) and S-4800 manufactured by Hitachi High-Technologies Corporation. In addition, it observed after performing 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-mentioned conditions, the reflected electron image is captured by adjusting the brightness to “contrast 5, brightness-5” on the control software of the scanning electron microscope S-4800, turning off the magnetic pair observation mode, and the 256th floor. Toned grayscale image was obtained.

  The calculation of the length of the porous magnetic particle part region in the cross section of the magnetic carrier particle and the length of the region other than the porous magnetic particle part (resin part and / or void) is performed by gray-scale SEM reflection of the magnetic carrier particle cross section. The electronic image is calculated by the following procedure using image analysis software Image-ProPlus 5.1J (manufactured by Media Cybernetics).

  Here, FIG. 2 shows an example of an SEM reflected electron image of a processed cross section of the magnetic carrier particle of the present invention. In FIG. 2, there may be a processed cross section 10 of magnetic carrier particles, a porous magnetic particle portion 11, a resin portion 12, a magnetic carrier surface 13, and a void portion (not shown).

  Only the processed cross-sectional area 10 of the magnetic carrier particles is designated in advance on the image. The boundary between the processed cross-sectional area of the magnetic carrier particles and the background can be easily distinguished from the reflected electron observation image. A cross-sectional area designated by particles is a 256-scale gray scale image. From the lower level of the gradation value, 0 to 10 gradations are divided into three areas of the void area, 11 to 129 gradations of the resin area, and 130 to 254 gradations of the porous magnetic particle area. The 255th gradation is a background portion outside the processed cross-sectional area. FIG. 3 shows a binarized view of the processed cross-sectional area 10 of the magnetic carrier particles. In the present invention, the region other than the porous magnetic particle portion indicates the resin portion 2 and the void portion (not shown).

FIG. 4 schematically shows a measurement example of the porous magnetic particle part region and the region other than the porous magnetic particle part in the cross section of the magnetic carrier particle of the present invention.
1. Let Rx be the maximum diameter in the processed cross-sectional area of the magnetic carrier particles.
2. The midpoint of Rx is taken as the reference point of the cross section of the magnetic carrier particle. Furthermore, let Ry be the diameter in the direction perpendicular to Rx at the midpoint.
3. The measurement targets magnetic carrier particles with Rx / Ry ≦ 1.2.
4). Porous magnetic particle part region having a length of 0.1 μm or more on a straight line (diameter) that passes through the reference point of the cross section of the magnetic carrier particle and is drawn every 5 ° toward the surface of the magnetic carrier particle In addition, the length and the number of regions other than the porous magnetic particle portion are measured. The starting point is 1, and numbers are assigned clockwise. From the above measured values, the number (number%) of “porous magnetic particle part regions having a length of 6.0 μm or more relative to the total number of porous magnetic particle part regions having a length of 0.1 μm or more”, “ The number (number%) of “regions other than the porous magnetic particle portion having a length of 4.0 μm or more” relative to the total number of regions other than the porous magnetic particle portion having a length of 0.1 μm or more.
5. The measurement is repeated for 25 magnetic carriers for particles satisfying Rx / Ry ≦ 1.2, and the average value is calculated. The ratio of particles satisfying Rx / Ry ≦ 1.2 was calculated using the cross-section processed particles required until the measurement reached 25 particles as the denominator.
Ratio of particles satisfying Rx / Ry ≦ 1.2 = 25 / number of particles processed in cross section × 100 (%)
FIG. 6 shows a region other than the porous magnetic particle part region having a length of 0.1 μm or more and the region other than the porous magnetic particle part having a length of 0.1 μm or more in the cross section of the magnetic carrier particle of the present invention. An example of the distribution of length and number (number%) is shown by the above method.

  In the method for measuring the area ratio of the porous magnetic particle portion in the cross section of the magnetic carrier particle, the processing cross sectional area of the magnetic carrier particle is designated in advance on the image, and the cross sectional area of the magnetic carrier particle is set. A value obtained by dividing the area occupied by the porous magnetic particle part 1 by the cross-sectional area of the magnetic carrier particle is referred to as “area ratio (area%) of the porous magnetic particle part”. In the present invention, the same measurement is performed on the 25 magnetic carrier particles described above, and the average value is used.

<Method of measuring resin thickness measured from distance from surface of magnetic carrier particle to surface of porous magnetic particle in cross section of magnetic carrier particle>
<Method for measuring the length of the porous magnetic particle portion region in the cross section of the magnetic carrier particle, the length of the region other than the porous magnetic particle portion, and the method for measuring the area ratio of the porous magnetic particle portion region shown above>> The same operation was performed, and the analysis method was changed as follows.

FIG. 4A is a diagram schematically showing a measurement example of the resin thickness measured from the distance from the surface of the magnetic carrier particle to the surface of the porous magnetic particle in the cross section of the magnetic carrier particle of the present invention. The operation procedure is as follows.
1. Let Rx be the maximum diameter in the processed cross-sectional area of the magnetic carrier particles.
2. The midpoint of Rx is taken as the reference point of the cross section of the magnetic carrier particle. Furthermore, let Ry be the diameter in the direction perpendicular to Rx at the midpoint.
3. The measurement targets magnetic carrier particles with Rx / Ry ≦ 1.2. A straight line that divides 72 equally from the reference point Rx of the magnetic carrier particle toward the surface of the magnetic carrier particle every 5 ° is numbered from 1 to 72 in a clockwise direction. The result is shown in FIG. On the straight line, the distance from the surface of the magnetic carrier particle to the surface of the porous magnetic particle is measured to obtain the resin thickness. This operation is repeated 72 times.
4). Of the total number (72) where the resin thickness is 0.0 μm or more and 0.3 μm or less and the total number (72) where the resin thickness is 1.5 μm or more and 5.0 μm or less ) In B) is calculated.
5. This measurement is repeated for 25 magnetic carriers, and the average value is calculated. The result is shown in FIG.

<Area ratio of part derived from porous magnetic particles on the surface of magnetic carrier particles>
The area% of the portion derived from the porous magnetic particles on the surface of the magnetic carrier particle of the present invention can be determined by observation of a reflected electron image with a scanning electron microscope and subsequent image processing.

  The area ratio of the portion derived from the porous magnetic particles on the surface of the magnetic carrier particles used in the present invention was measured using a scanning electron microscope (SEM) and S-4800 (manufactured by Hitachi, Ltd.). The area ratio of the portion derived from the porous magnetic particles is calculated from image processing of an image that visualizes mainly reflected electrons when the acceleration voltage is 2.0 kV. Specifically, the carrier particles are fixed in a single layer with a carbon tape on a sample stage for observation with an electron microscope, and scanning electron microscope S-4800 (Hitachi) is used under the following conditions without performing deposition with platinum. (Manufactured by Seisakusho). Observe after performing 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 = 1280 × 960
ColorMode = Grayscale
The reflected electron image is adjusted to brightness of “Contrast 5 and Brightness-5” on the control software of the scanning electron microscope S-4800, the capture speed / total number of images “Slow 4 is 40 seconds”, and the image size is 1280 × 960 pixels of 8 bits. A projection image of the magnetic carrier was obtained as a 256 gray scale gray scale image (FIG. 7). 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 .

  Then, the area ratio (area%) of the part originating in a metal oxide was calculated about 50 magnetic carrier particles using the obtained projection image by a reflected electron. Details of the method of selecting 50 magnetic carrier particles to be analyzed will be described later. Image processing software Image-Pro Plus 5.1J (manufactured by Media Cybernetics) was used for the area% of the portion derived from the metal oxide.

  First, the character string at the bottom of the image in FIG. 7 is unnecessary for image processing, and unnecessary portions were deleted and cut into a size of 1280 × 895 (FIG. 8).

  Next, the magnetic carrier particle part was extracted, and the size of the extracted magnetic carrier particle part was counted. Specifically, first, in order to extract the magnetic carrier particles to be analyzed, the magnetic carrier particles and the background portion are separated. Select “Measurement”-“Count / Size” of Image-Pro Plus 5.1J. In “Brightness range selection” of “Count / Size”, the brightness range was set to a range of 50 to 255, and the low-brightness carbon tape portion reflected in the background was excluded, and magnetic carrier particles were extracted. (FIG. 9). When the magnetic carrier particles are fixed by a method other than the 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 particles. However, the boundary between the magnetic carrier particles and the background can be easily distinguished from the backscattered electron observation image. When performing the extraction, select 4 connections in the “Count / Size” extraction option, enter a smoothness of 5, enter a check for fill in holes, and check for particles or other points on all boundaries (peripheries) of the image. Particles overlapping with particles were excluded from the calculation. Next, in the “count / size” measurement item, an area and a ferret diameter (average) were selected, and the area selection range was set to a minimum of 300 pixels and a maximum of 10000000 pixels. Further, 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 particles subjected to image analysis are selected. Extracted (FIG. 10). One particle was selected from the extracted particle group, and (ja) was determined for the size (number of pixels) of the portion derived from the particle.

  Next, in “Brightness range selection” of “Count / Size” of Image-Pro Plus 5.1J, the brightness range was set to a range of 140 to 255, and a portion with high brightness on the carrier particles was extracted ( FIG. 11). The selection range of the area was a minimum of 10 pixels and a maximum of 10000 pixels.

  And about the particle | grains selected when calculating | requiring ja, the magnitude | size (pixel number) (ma) of the part originating in the metal oxide of the magnetic carrier particle surface was calculated | required. In each magnetic carrier particle, extracted portions derived from the metal oxide are scattered with a certain size, and ma is the total area. Each of these scattered portions is called a “domain” in the present invention.

Then, the area ratio _{S 1} according to the present invention is obtained by (ma / ja) × 100.
Next, the same processing was performed on each particle of the extracted particle group until the number of selected magnetic carrier particles reached 50. When the number of particles in one field was less than 50, the same operation was repeated for the projected image of magnetic carrier particles in another field.

The average ratio Av _{1 according} to the present invention can be calculated from the following equation using the total value Ma of ma measured for 50 particles and the total value Ja of ja measured for 50 particles. It is the average value when measured.
Av ₁ = (Ma / Ja) × 100
<Area distribution with respect to the total area of the portion derived from the metal oxide>
The area distribution of the portion derived from the metal oxide with respect to the total area of the portion derived from the metal oxide can be obtained by observation of reflected electron images with a scanning electron microscope, image processing, and subsequent statistical processing. In the same manner as obtaining the area% of the part derived from the metal oxide, 50 magnetic carrier particles were observed, and the part derived from the metal oxide in the magnetic carrier was extracted from the image. The size of each domain of the portion derived from the extracted metal oxide for 50 pieces was determined and distributed to channels for every 20 pixels. The area of 1 pixel is 0.0278 μm ² . The average value Av ₂ (area%) distributed over 6.672 μm ² was calculated using the center value of each channel as a representative value.

<Measurement of electric field strength just before breakdown of magnetic carrier>
The electric field strength just before the magnetic carrier breaks down is measured using a measuring apparatus schematically shown in FIG.

The resistance measurement cell A includes a cylindrical PTFE resin container 1 having a hole with a cross-sectional area of 2.4 cm ² , a lower electrode (made of stainless steel) 2, a support base (made of PTFE resin) 3, and an upper electrode (made of stainless steel) 4. Composed. A cylindrical PTFE resin container 1 is placed on the support pedestal 3, and a sample (magnetic carrier or porous magnetic particle) 5 is filled to a thickness of about 1 mm, and the upper electrode 4 is placed on the filled sample 5; Measure the thickness of the sample. As shown in FIG. 1A, when the gap when there is no sample is d1, and when the gap is d2 when the sample is filled to a thickness of about 1 mm as shown in FIG. d is calculated by the following equation.
d = d2-d1
At this time, it is important to appropriately change the mass of the sample so that the thickness of the sample becomes 0.95 mm or more and 1.04 mm.

By applying a DC voltage between the electrodes and measuring the current flowing at that time, the electric field strength just before the magnetic carrier breaks down can be obtained. For the measurement, an electrometer 6 (Kesley 6517A, manufactured by Kesley) and a computer 7 are used for control. This is performed by software using a control system and control software (manufactured by LabVEIW National Instruments) manufactured by National Instruments for the control computer. As measurement conditions, a measured value d is input so that the contact area S of the sample and the electrode is S = 2.4 cm ² and the thickness of the sample is 0.95 mm or more and 1.04 mm or less. The upper electrode load is 270 g and the maximum applied voltage is 1000 V. The voltage application conditions are 1V (2 ⁰ V), 2 V (2 ¹ V), 4 V (using the IEEE-488 interface for control between the control computer and the electrometer, and using the electrometer automatic range function. 2 ² V), 8 V (2 ³ V), 16 V (2 ⁴ V), 32 V (2 ⁵ V), 64 V (2 ⁶ V), 128 V (2 ⁷ V), 256 V (2 ⁸ V), 512 V (2 ⁹ V), screening is performed by applying a voltage of 1000 V for 1 second. At that time, the electrometer determines whether or not up to 1000 V (for example, 10000 V / cm as the electric field strength in the case of a sample thickness of 1.00 mm) can be applied, and if an overcurrent flows, “VOLTAGE SOURCE OPERATE” Flashes. Then, the applied voltage is lowered, the applicable voltage is further screened, and the maximum value of the applied voltage is automatically determined. Then, this measurement is performed. The resistance value is measured from the current value after holding the voltage obtained by dividing the maximum voltage value into five steps for 30 seconds. For example, when the maximum applied voltage is 1000 V, 200 V (first step), 400 V (second step), 600 V (third step), 800 V (fourth step), 1000 V (fifth step), 1000 V (first step) 6 steps), 800V (7th step), 600V (8th step), 400V (9th step), 200V (10th step), and then increase and decrease the voltage in 200V increments, which is 1/5 of the maximum applied voltage The resistance value is measured from the current value after holding for 30 seconds in each step.

In the case of the magnetic carrier used in Example 1, at the time of screening, 1 V (2 ⁰ V), 2 V (2 ¹ V), 4 V (2 ² V), 8 V (2 ³ V), 16 V (2 ⁴ V) DC voltage of 32V (2 ⁵ V), 64 V (2 ⁶ V), 128 V (2 ⁷ V), 256 V (2 ⁸ V), 512 V (2 ⁹ V) is applied to the magnetic carrier for 1 second, and “VOLTAGE” The display was turned on until the display of “SOURCE OPERATE” was up to 256V, and the display of “VOLTAG SOURCE OPERATE” flashed at 512V. Then flashing the DC voltage 362V ^{(2 8.5} V), flashing a DC voltage 294V (≒ ^{2 8.2} V), further, by converging the maximum applicable voltage, DC voltage 274V ^{(2 8.1} illuminates V), as a result, the maximum applied voltage becomes 274V ^{(2 8.1} V). 274V 1/5 value 54.8V (first step) 274V 2/5 value 109.6V (second step) 274V 3/5 value 164.4V (third step) 274V 4/5 value 219.2V (4th step) 274V 5/5 value 274V (5th step) 5/5 value 274V (6th step) 274V 4 / 59.2 value 219.2V (7th step) 274V 3/5 value 164.4V (8th step) 274V 2/5 value 109.6V (9th step) 274V 1 A DC voltage is applied in the order of 54.8 V (tenth step) of / 5. The current value thus obtained is processed by a computer, and the electric field strength and specific resistance are calculated from the sample thickness of 1.04 mm and the electrode area, and plotted on a graph. In that case, 5 points to decrease the voltage from the maximum applied voltage are plotted. In the measurement at each step, “VOLTAGE SOURCE OPERATE” blinks, and when an overcurrent flows, the resistance value is displayed as 0 for measurement. This phenomenon is defined as breakdown. This “VOLTAGE SOURCE OPERATE” flashing phenomenon is defined as the electric field strength just before the breakdown. Therefore, “VOLTAGE SOURCE OPERATE” blinks and the point at which the maximum electric field strength of the above-described profile is plotted is defined as the electric field strength just before the breakdown. When “VOLTAGE SOURCE OPERATE” blinks when the maximum applied voltage is applied, if the resistance value does not become zero and plotting is possible, the electric field strength is set to the point just before breakdown.

In addition, specific resistance and electric field strength are calculated | required by a following formula.
Specific resistance (Ω · cm) = (applied voltage (V) / measured current (A)) × S (cm ² ) / d (cm)
Electric field strength (V / cm) = applied voltage (V) / d (cm)
<Method for Measuring Toner Weight Average Particle Size (D4)>
The weight average particle diameter (D4) of the toner is calculated as follows. As a measuring device, a precise particle size distribution measuring device “Coulter Counter Multisizer 3” (registered trademark, manufactured by Beckman Coulter, Inc.) using a pore electrical resistance method equipped with a 100 μm aperture tube is used. For setting the measurement conditions and analyzing the measurement data, the attached dedicated software “Beckman Coulter Multisizer 3 Version 3.51” (manufactured by Beckman Coulter, Inc.) is used. The measurement is performed with 25,000 effective measurement channels.

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

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

  On the “Change Standard Measurement Method (SOM)” screen of the dedicated software, set the total count in the control mode to 50,000 particles, set the number of measurements once, and set the Kd value to “standard particles 10.0 μm” (Beckman Coulter Set the value obtained using By pressing the “Threshold / Noise Level Measurement Button”, the threshold and noise level are automatically set. In addition, the current is set to 1600 μA, the gain is set to 2, the electrolyte is set to ISOTON II, and the “aperture tube flush after measurement” is checked.

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

The specific measurement method is as follows.
(1) About 200 ml of the electrolytic solution is placed in a glass 250 ml round bottom beaker exclusively for Multisizer 3, set on a sample stand, and the stirrer rod is stirred counterclockwise at 24 rpm. Then, the dirt and bubbles in the aperture tube are removed by the “aperture flush” function of the dedicated software.
(2) About 30 ml of the electrolytic aqueous solution is put into a glass 100 ml flat bottom beaker. In this, "Contaminone N" (nonionic surfactant, anionic surfactant, 10% by weight aqueous solution of neutral detergent for pH7 precision measuring instrument cleaning, made by organic builder, manufactured by Wako Pure Chemical Industries, Ltd. About 0.3 ml of a diluted solution obtained by diluting 3) with ion-exchanged water is added.
(3) Two oscillators with an oscillation frequency of 50 kHz are incorporated with the phase shifted by 180 degrees, and an ultrasonic disperser “Ultrasonic Dissipation System Tetora 150” (manufactured by Nikkei Bios) with an electrical output of 120 W is prepared. About 3.3 l of ion-exchanged water is placed in the water tank of the ultrasonic disperser, and about 2 ml of Contaminone N is added to the 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 by the dedicated software is the weight average particle diameter (D4).

<Measurement of Ratio of Particles (Small Particles) That Have an Equivalent Circle Diameter of 0.6 μm to 2.0 μm and Average Circularity of Toner>
The proportion of particles (small particles) having an equivalent circle diameter of 0.6 μm or more and 2.0 μm or less and the average circularity of the toner are calibrated by a flow type particle image measuring device “FPIA-3000 type” (manufactured by Sysmex Corporation). The measurement was performed under the measurement and analysis conditions during work.

  The measurement principle of the flow-type particle image measuring device “FPIA-3000 type” (manufactured by Sysmex Corporation) is to capture flowing particles as a still image and perform image analysis. The sample added to the sample chamber is fed into the flat sheath flow cell by a sample suction syringe. The sample fed into the flat sheath flow is sandwiched between sheath liquids to form a flat flow. The sample passing through the flat sheath flow cell is irradiated with strobe light at 1/60 second intervals, and the flowing particles can be photographed as a still image. Further, since the flow is flat, the image is taken in a focused state. The particle images are picked up by a CCD camera, and the picked-up image is 512 pixels × 512 pixels in one field of view, and image processing is performed at an image processing resolution of 0.37 × 0.37 μm per pixel, and the contour of each particle image Extraction is performed, and the projected area and perimeter of the particle image are measured.

Next, the projected area S and the perimeter L of each particle image are obtained. Using the area S and the perimeter L, the equivalent circle diameter and the circularity are obtained. The circular equivalent diameter is the diameter of a circle having the same area as the projected area of the particle image, and the circularity is a value obtained by dividing the circumference of the circle obtained from the circular diameter by the circumference of the projected particle image. Defined and calculated by the following formula.
Circularity C = 2 × (π × S) ^1/2 / L
When the particle image is a perfect circle, the circularity becomes 1.000, and the circularity becomes smaller as the degree of irregularities on the outer periphery of the particle image increases.

  After calculating the circularity of each particle, the range of the circularity of 0.2 or more and 1.0 or less is distributed to 800 divided channels, the average value is calculated by using the center value of each channel as a representative value, and the average circularity is calculated. Do.

  As a specific measurement method, 0.02 g of a surfactant, preferably an alkylbenzene sulfonate, is added to 20 ml of ion-exchanged water, and then 0.02 g of a measurement sample is added, an oscillation frequency of 50 kHz, electrical output. Dispersion treatment was carried out for 2 minutes using a 150 W tabletop type ultrasonic cleaner / disperser (for example, “VS-150” (manufactured by VervoCrea Co., Ltd.)) to obtain a dispersion for measurement. It cools suitably so that temperature may become 10 to 40 degreeC.

  The flow type particle image analyzer equipped with a standard objective lens (10 ×) was used for the measurement, and a particle sheath “PSE-900A” (manufactured by Sysmex Corporation) was used as the sheath liquid. The dispersion prepared in accordance with the above procedure is introduced into the flow type particle image measuring apparatus, 3000 toner particles are measured in the total count mode in the HPF measurement mode, and the binarization threshold at the time of particle analysis is 85%. By specifying the analysis particle diameter, the number ratio (%) of particles in the range and the average circularity can be calculated. The ratio of particles (small particles) having an equivalent circle diameter of 0.60 μm or more and 2.00 μm or less is set such that the analysis particle diameter range of the equivalent circle diameter is 0.60 μm or more and 2.00 μm or less. The number ratio (%) of was calculated. The average circularity of the toner was set to an equivalent circle diameter of 2.00 μm to 200.00 μm, and the average circularity of the toner was determined.

  In the measurement, automatic focus adjustment is performed using standard latex particles (for example, Duke Scientific 5200A diluted with ion-exchanged water) before the measurement is started. Thereafter, it is preferable to perform focus adjustment every two hours from the start of measurement.

  In the embodiment of the present application, a flow type particle image measuring apparatus, which has been calibrated by Sysmex Corporation and has been issued a calibration certificate issued by Sysmex Corporation, has an analysis particle diameter of 2.00 μm. The measurement was performed under the measurement and analysis conditions when the calibration certificate was received, except that it was limited to 200.00 μm or less.

<Method of measuring weight average molecular weight (Mw) of resin>
The weight average molecular weight (Mw) is measured by gel permeation chromatography (GPC) as follows.

  First, a sample is dissolved in tetrahydrofuran (THF) at room temperature over 24 hours. As the sample, resin or toner is used. 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: Seven series of Shodex KF-801, 802, 803, 804, 805, 806, 807 (manufactured by Showa Denko KK)
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.

<Production Example of Porous Magnetic Particle 1>
Process 1 (weighing / mixing process):
Fe ₂ O ₃ 58.7 mass%
MnCO ₃ 34.9% by mass
Mg (OH) ₂ 5.2% by mass
SrCO ₃ 1.2% by mass
The ferrite raw material was weighed so that the material had the above composition ratio. Thereafter, the mixture was pulverized and mixed for 2 hours in a dry ball mill using zirconia balls having a diameter of 10 mm.

Step 2 (temporary firing step):
After pulverization and mixing, firing was performed at a temperature of 950 ° C. for 2 hours in the air using a burner-type firing furnace to prepare calcined ferrite. The composition of the ferrite is as follows.
(MnO) _a (MgO) _b (SrO) _c (Fe ₂ O ₃ ) _d
In the above formula, a = 0.395, b = 0.116, c = 0.111, d = 0.478.
Step 3 (grinding step):
After crushing to about 0.3 mm with a crusher, 30 parts by mass of water was added to 100 parts by mass of calcined ferrite using a stainless steel ball having a diameter of 10 mm, and the mixture was pulverized with a wet ball mill for 1 hour. The slurry was pulverized with a wet bead mill using zirconia beads having a diameter of 1.0 mm for 1 hour to obtain a ferrite slurry (a finely pulverized product of calcined ferrite). The obtained finely pulverized product of calcined ferrite has a volume distribution standard 50% particle size (D50) of 2.0 μm, a volume distribution standard particle size of 90% (D90) of 6.4 μm, and D90 / D50 = 3.2. there were.

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 with a spray dryer (manufacturer: Okawara Chemical).

Process 5 (firing process):
In order to control the firing atmosphere, the temperature was raised from room temperature to 1150 ° C. in a nitrogen atmosphere (oxygen concentration 0.01% by volume) in an electric furnace in 3 hours, and then fired at 1150 ° C. for 4 hours. Thereafter, the temperature was lowered to 80 ° C. over 8 hours, returned from the nitrogen atmosphere to the atmosphere, and taken out at a temperature of 40 ° C. or less.

Process 6 (screening process):
After the aggregated particles were crushed, coarse particles were removed by sieving with a sieve having an opening of 250 μm to obtain porous magnetic particles 1 having a volume distribution standard 50% particle size (D50) of 36.0 μm. The obtained physical properties are shown in Table 1.

<Production example of porous magnetic particles 2 to 15>
Porous magnetic particles 2 to 15 were produced in the same manner except that the porous magnetic particle 1 production example was changed as shown in Table 2. The obtained physical properties are shown in Table 1.

<Preparation of resin liquid 1>
Silicone varnish (KR271, manufactured by Shin-Etsu Chemical Co., Ltd.) was mixed with 20.0 parts by mass in terms of solid content, 0.4 parts by mass of γ-aminopropyltriethoxysilane, and 179.6 parts by mass of toluene for 1 hour, Obtained.

<Preparation of resin liquid 2>
Silicone varnish (SR2410, manufactured by Toray Dow Corning Co., Ltd.) was mixed for 2 hours with 60.0 parts by mass in terms of solid content, 1.2 parts by mass of γ-aminopropyltriethoxysilane, and 138.8 parts by mass of toluene for 2 hours. Liquid 2 was obtained.

<Preparation of resin liquid 3>
Silicone varnish (SR2411, manufactured by Toray Dow Corning Co., Ltd.) in terms of solid content was 20.0 parts by mass, γ-aminopropyltriethoxysilane 0.4 parts by mass, conductive carbon (Ketjen Black International Co., Ltd. (Chen Black EC) 0.4 parts by mass and toluene 179.2 parts by mass were mixed for 1 hour to obtain a resin liquid 3.

<Example of production of magnetic carrier 1>
Step 1 (resin filling step 1):
100.0 parts by mass of the porous magnetic particles 1 are put into a stirring vessel of a mixing stirrer (universal stirrer NDMV type manufactured by Dalton), and nitrogen is introduced while reducing the pressure while maintaining the temperature at 30 ° C. Liquid 1 was added dropwise to the porous magnetic particles 1 under reduced pressure so as to be 8.0 parts by mass as a resin component, and stirring was continued for 2 hours after completion of the addition. Thereafter, the temperature was raised to 70 ° C., the solvent was removed under reduced pressure, and the pores of the porous magnetic particles 1 were filled with a silicone resin composition having a silicone resin obtained from the resin liquid 1. After cooling, the obtained magnetic carrier particles are transferred to a mixer having a spiral blade in a rotatable mixing container (drum mixer UD-AT type manufactured by Sugiyama Heavy Industries Co., Ltd.) and heat-treated at a temperature of 200 ° C. for 2 hours in a nitrogen atmosphere. After that, it was classified with a sieve having an opening of 70 μm to obtain a magnetic carrier 1a.

Step 2 (resin coating step 1):
100.0 parts by mass of the magnetic carrier 1a is put into a planetary motion type mixer (Nauta mixer VN type manufactured by Hosokawa Micron Co., Ltd.), the screw-like stirring blade is rotated 3.5 revolutions per minute, and the rotation is performed per minute. Stirring while rotating 100 times, flowing nitrogen at a flow rate of 0.1 m ³ / min, and heating to a temperature of 70 ° C. to further remove toluene under reduced pressure (about 0.01 MPa). The resin liquid 1 was added so that it might become 2.0 mass parts as a resin component with respect to a magnetic carrier. As a method of charging, 1/3 amount of the resin liquid was charged, and toluene was removed and coating operation was performed for 20 minutes. Next, a further 1/3 amount of the resin solution was added, and toluene removal and coating operation were performed for 20 minutes. Further, a 1/3 amount of the resin solution was added, and toluene removal and coating operation were performed for 20 minutes. The coating amount was 2.0 parts by mass with respect to 100 parts by mass of the magnetic carrier. Thereafter, the magnetic carrier coated with the silicone resin is transferred to a mixer (spiral mixer UD-AT type manufactured by Sugiyama Heavy Industries Co., Ltd.) having spiral blades in a rotatable mixing container, and the mixing container is rotated 10 times per minute. While stirring, heat treatment was performed for 2 hours at a temperature of 200 ° C. in a nitrogen atmosphere. By stirring, the thickness of the resin on the surface of the magnetic carrier particles was controlled. The obtained magnetic carrier was passed through a sieve having an opening of 70 μm, and then classified by an air classifier, and the fine particle side and the coarse particle side were cut to obtain a magnetic carrier 1. Table 3 shows the obtained physical properties.

<Examples of production of magnetic carriers 2 to 8, 11 to 14, and 17>
Magnetic carriers 2 to 8, 11 to 14, and 17 were produced in the same manner except that the magnetic carrier 1 was manufactured as shown in Table 4 in the production example. Table 3 shows the obtained physical properties.

<Example of manufacturing magnetic carrier 9>
The resin filling step 2 shown in the manufacturing example of the magnetic carrier 1 was not performed, and the resin coating step 2 shown below was performed.

Step 2 (resin coating step 2):
Put 100.0 parts by mass of the porous magnetic particles 8 into a fluidized bed coating apparatus (Spiraflow SFC type manufactured by Freund Sangyo Co., Ltd.), introduce nitrogen with an air supply rate of 0.8 m ³ / min, and set the air supply temperature to The temperature was 100 ° C. The number of rotations of the rotating rotor was set to 1000 rotations per minute, and after the product temperature reached 50 ° C., spraying was started using the resin liquid 2. The spray rate was 3.5 g / min. The magnetic carrier 9 was obtained by covering the 100.0 parts by mass of the porous magnetic particles 8 until the coating resin amount was 3.0 parts by mass. Thereafter, the magnetic carrier coated with the silicone resin is transferred to a mixer (spiral mixer UD-AT type manufactured by Sugiyama Heavy Industries Co., Ltd.) having spiral blades in a rotatable mixing container, and the mixing container is rotated 20 times per minute. While stirring, heat treatment was performed for 2 hours at a temperature of 200 ° C. in a nitrogen atmosphere. By stirring, the thickness of the resin on the surface of the magnetic carrier particles was controlled. The obtained magnetic carrier was passed through a sieve having an opening of 70 μm, and then classified by an air classifier, and the coarse particle side was cut to obtain a magnetic carrier 9.

<Examples of production of magnetic carriers 10, 15, 16>
Magnetic carriers 10, 15, and 16 were produced in the same manner except that the magnetic carrier 9 was manufactured as shown in Table 4 in the production example. Table 3 shows the obtained physical properties.

<Example of manufacturing magnetic carrier 18>
Step 1 (resin filling step 2):
Put 100.0 parts by mass of the porous magnetic particles 14 into a uniaxial indirect heating dryer (Torus disk TD type, manufactured by Hosokawa Micron), and maintain the temperature at 75 ° C. while introducing nitrogen, while maintaining the temperature of the resin liquid 1 to be porous. It dripped so that it might become 13.0 mass parts as a resin component with respect to the magnetic particle 14, and stirring was continued as it was for 2 hours after completion | finish of dripping. Thereafter, the temperature was raised to 200 ° C., and the solvent was removed under reduced pressure. Thereafter, the stirring rotation speed of the mixer having spiral blades is changed from 10 to 1.5 times per minute, heated at 200 ° C. for 2 hours, cooled, classified with a sieve having an opening of 70 μm, and the magnetic carrier 18a is Obtained.

Step 2 (resin coating step 3):
100.0 parts by mass of the magnetic carrier 18a is put into a fluidized bed coating apparatus (Spiraflow SFC type manufactured by Freund Sangyo Co., Ltd.), nitrogen with an air supply rate of 0.8 m ³ / min is introduced, and the air supply temperature is set to a temperature of 70. C. The number of rotations of the rotating rotor was 1000 rpm, and after the product temperature reached 50 ° C., spraying was started using the resin liquid 3. The spray rate was 3.5 g / min. The coating was performed until the coating resin amount became 2.0 parts by mass with respect to 100.0 parts by mass of the porous magnetic particles 8, and the magnetic carrier 18 was obtained. Further, the heat treatment after the coating is replaced with a vacuum dryer, and the magnetic carrier 18 is treated at a temperature of 220 ° C. for 2 hours under reduced pressure (about 0.01 MPa) while flowing nitrogen at a flow rate of 0.01 m ³ / min. Obtained.

<Example of manufacturing magnetic carrier 19>
A magnetic carrier 19 was produced in the same manner except that the magnetic carrier 18 was changed as shown in Table 4. Table 3 shows the obtained physical properties.

<Example of production of crystalline polyester resin dispersion 1>
In a heat-dried three-necked flask, an acid component consisting of 98 mol% dimethyl sebacate and 2 mol% dimethyl-5-sulfonic acid sodium salt and an alcohol component consisting of ethylene glycol were added at a molar ratio of 1: 1. After adding 0.3 parts of dibutyltin oxide as a catalyst to a total of 100 parts, the air in the container is brought into an inert atmosphere with nitrogen gas by depressurization and stirred and refluxed at 180 ° C. for 5 hours with mechanical stirring. Went. Thereafter, the temperature was gradually raised to 230 ° C. under reduced pressure, and the mixture was stirred for 2 hours. When it became viscous, it was air-cooled to stop the reaction, and a crystalline polyester resin having a weight average molecular weight (Mw) of 9700. 1 was synthesized.

-Crystalline polyester resin 1:90 parts-Ionic surfactant (Neogen RK, Daiichi Kogyo Seiyaku): 1.8 parts-Ion exchange water: 210 parts The above ingredients are mixed and the mixture is heated to 100 ° C. After sufficiently dispersing with a homogenizer (manufactured by IKA, Ultra Tarrax T50), dispersion treatment was performed for 1 hour with a pressure discharge type gorin homogenizer. Thereafter, the pH of the system was adjusted to 12.5 with a 0.5 mol / l sodium hydroxide aqueous solution and treated at 96 ° C. for 6 hours, then the pH was adjusted to 7.0 with an aqueous nitric acid solution, and the solid content was further adjusted. Thus, a crystalline polyester resin dispersion 1 having a volume average particle size of 200 nm and a solid content of 30% was obtained.

<Example of production of crystalline polyester resin dispersion 2>
In a heat-dried three-necked flask, an acid component consisting of 90.5 mol% 1,10-dodecanedioic acid, 2 mol% dimethyl-5-sulfonate sodium and 7.5 mol% 5-t-butylisophthalic acid, An alcohol component composed of 9-nonanediol was added at a molar ratio of 1: 1, and 0.3 parts of dibutyltin oxide was added as a catalyst to a total of 100 parts thereof. Thereafter, the air in the container was brought into an inert atmosphere with nitrogen gas by a depressurization operation, and the mixture was stirred and refluxed at 180 ° C. for 5 hours by mechanical stirring. Thereafter, the temperature was gradually raised to 230 ° C. under reduced pressure, and the mixture was stirred for 4 hours. When it became viscous, it was air-cooled to stop the reaction, and a crystalline polyester resin having a weight average molecular weight (Mw) of 28000. 2 was synthesized.

-Crystalline polyester resin 2: 90 parts-Ionic surfactant (Neogen RK, Daiichi Kogyo Seiyaku): 1.8 parts-Ion exchange water: 210 parts The above ingredients are mixed and the mixture is heated to 100 ° C. Then, after sufficiently dispersing with a homogenizer (IKA, Ultra Tarrax T50), the dispersion process is performed with a pressure discharge type gorin homogenizer for 1 hour, and then the pH of the system is adjusted with 0.5 mol / l sodium hydroxide aqueous solution. After adjusting to 13.0 and treating at 96 ° C. for 8 hours, the pH is adjusted to 7.0 with an aqueous nitric acid solution, the solid content is adjusted, and a crystalline polyester having a volume average particle size of 300 nm and a solid content of 30%. A resin dispersion 2 was obtained.

<Example of production of amorphous polyester resin dispersion 1>
An acid component composed of 30 mol% terephthalic acid and 70 mol% fumaric acid and an alcohol component composed of 20 mol% bisphenol A ethylene oxide 2 mol adduct and 80 mol% bisphenol A propylene oxide 2 mol adduct in a molar ratio of 1: 1. In a 5 liter flask equipped with a stirrer, nitrogen inlet tube, temperature sensor, and rectifying column, charge it to 190 ° C over 1 hour and confirm that the reaction system is uniformly stirred. did. Thereafter, 1.2 parts of dibutyltin oxide was added to 100 parts of the mixture, and the temperature was raised to 240 ° C. over 6 hours from the same temperature while distilling off the water formed, and the temperature was further increased to 240 ° C. for 3 hours. The dehydration condensation reaction was continued to obtain an amorphous polyester resin 1 having a weight average molecular weight (Mw) of 9700.

Subsequently, the obtained amorphous polyester resin 1 was transferred in a molten state to Cavitron CD1010 (manufactured by Eurotech Co., Ltd.) at a rate of 100 g / min. Separately prepared aqueous medium tank is filled with 0.37% dilute aqueous ammonia diluted with reagent-exchanged ammonia water with ion-exchanged water, heated at 120 ° C. with a heat exchanger at a rate of 0.1 liter per minute, The amorphous polyester resin 1 melt was transferred to Cavitron CD1010 (manufactured by Eurotech Co., Ltd.). The Cavitron was operated under conditions of a rotor rotation speed of 60 Hz and a pressure of 5 kg / cm ² . Thereafter, the pH in the system was adjusted to 13.0 with a 0.5 mol / l sodium hydroxide aqueous solution and treated at 96 ° C. for 8 hours, then the pH was adjusted to 7.0 with an aqueous nitric acid solution, and the solid content was further adjusted. Thus, an amorphous polyester resin dispersion 1 having a volume average particle size of 160 nm and a solid content of 30% was obtained.

<Example of production of amorphous polyester resin dispersion 2>
An acid component composed of 60 mol% terephthalic acid, 10 mol% trimellitic anhydride and 30 mol% dodecenyl succinic acid, an alcohol component composed of 50 mol% bisphenol A ethylene oxide 2 mol adduct and 50 mol% bisphenol A propylene oxide 2 mol adduct, Amorphous polyester resin 2 having a weight average molecular weight (Mw) of 16000 was prepared in the same manner as amorphous polyester resin 1 by charging at a molar ratio of 1: 1.

  Next, using the obtained amorphous polyester resin 2, in the same manner as the amorphous polyester resin dispersion 1, an amorphous polyester resin dispersion 2 having a volume average particle size of 150 nm and a solid content of 30% is obtained. Obtained.

<Production Example of Styrene / Acrylic Resin Dispersion 1>
-Styrene: 370 parts-n-butyl acrylate: 30 parts-Acrylic acid: 8 parts-Dodecanethiol: 24 parts-Carbon tetrabromide: 4 parts A mixture of the above and dissolved is a nonionic surfactant (Sanyo Kasei) Co., Ltd., Nonipol 400) 6 parts and anionic surfactant (Daiichi Kogyo Seiyaku Co., Ltd., Neogen SC) 10 parts dissolved in 550 parts of ion-exchanged water was added to the flask and dispersed. Emulsified. While slowly mixing for 10 minutes, 50 parts of ion-exchanged water in which 4 parts of ammonium persulfate was dissolved was added thereto, and after replacing with nitrogen, an oil bath was used until the contents reached 70 ° C. while stirring the flask. The emulsion polymerization was continued for 5 hours. Then, after adjusting the system pH to 12.5 with 0.5 mol / l sodium hydroxide aqueous solution and treating at 96 ° C. for 6 hours, the pH is adjusted to 3.0 with nitric acid aqueous solution, and the solid content is further adjusted. Thus, a styrene-acrylic resin dispersion 1 having a volume average particle size of 155 nm, a weight average molecular weight (Mw) of 12,000, and a solid content of 40% was obtained.

<Production example of styrene / acrylic resin dispersion 2>
-Styrene: 280 parts-n-butyl acrylate: 120 parts-Acrylic acid: 8 parts 6 parts of a nonionic surfactant (manufactured by Sanyo Chemical Co., Ltd., Nonipol 400) and an anionic interface 12 parts of an activator (Daiichi Kogyo Seiyaku Co., Ltd., Neogen SC) dissolved in 550 parts of ion-exchanged water was added to the flask and dispersed and emulsified. While mixing slowly for 10 minutes, 50 parts of ion-exchanged water in which 3 parts of ammonium persulfate was dissolved was added thereto, and after replacing with nitrogen, an oil bath was used until the contents reached 70 ° C. while stirring the flask. The emulsion polymerization was continued for 5 hours. Then, after adjusting the system pH to 12.5 with 0.5 mol / l sodium hydroxide aqueous solution and treating at 96 ° C. for 6 hours, the pH is adjusted to 3.0 with nitric acid aqueous solution, and the solid content is further adjusted. Thus, a styrene-acrylic resin dispersion 2 having a volume average particle size of 105 nm, a weight average molecular weight (Mw) of 550,000, and a solid content of 40% was obtained.

<Amorphous polyester resin 3>
Terephthalic acid: 299 parts by mass Trimellitic anhydride: 19 parts by mass Polyoxypropylene (2.2) -2,2-bis (4-hydroxyphenyl) propane: 747 parts by mass Titanium dihydroxybis (triethanolamine) Nate): 1 part by mass The following materials were weighed in a reaction vessel equipped with a cooling tube, a stirrer, and a nitrogen introducing tube. Then, it is heated to a temperature of 200 ° C., reacted for 10 hours while removing the water generated while introducing nitrogen, then reduced in pressure to 10 mmHg and reacted for 1 hour, and an amorphous polyester having a weight average molecular weight (Mw) of 6000. Resin 3 was obtained.

<Amorphous polyester resin 4>
-Terephthalic acid: 332 parts by mass-Polyoxyethylene (2.2) -2,2-bis (4-hydroxyphenyl) propane: 996 parts by mass-Titanium dihydroxybis (triethanolaminate): 1 part by mass Thereafter, 220 The mixture was heated to 0 ° C. and reacted for 10 hours while removing generated water while introducing nitrogen. Further, 96 parts by mass of trimellitic anhydride was added, heated to a temperature of 180 ° C., and reacted for 2 hours to obtain an amorphous polyester resin 4 having a weight average molecular weight (Mw) of 84000.

<Preparation of colorant dispersion>
-Cyan pigment (CI Pigment Blue 15: 3 (copper phthalocyanine), manufactured by Dainichi Seika): 45 parts-Ionic surfactant (Neogen RK, Daiichi Kogyo Seiyaku): 5 parts-Ion-exchanged water: 200 The above components were mixed and dissolved, and dispersed for 10 minutes with a homogenizer (IKA, Ultra Turrax T50) to obtain a colorant dispersion having a volume average particle size of 168 nm and a solid content of 23.0%.

<Preparation of release agent dispersion>
-Paraffin wax (HNP-9, manufactured by Nippon Seiki Co., Ltd., melting point: 75 ° C): 45 parts-Cationic surfactant (Neogen RK, Daiichi Kogyo Seiyaku): 5 parts-Ion exchange water: 200 parts Heat to 95 ° C., fully disperse with a homogenizer (IKA's Ultra Turrax T50), and then disperse with a pressure discharge type gorin homogenizer, and release with a volume average particle size of 190 nm and a solid content of 20% An agent dispersion was obtained.

<Production Example of Toner 1>
-Example of production of toner particles 1-
Amorphous polyester resin dispersion 1: 95.0 parts Amorphous polyester resin dispersion 2: 95.0 parts Crystalline polyester resin dispersion 2: 18.0 parts Colorant dispersion: 22.0 Part: Release agent dispersion: 50.0 parts or more is put into a round stainless steel flask, the pH is adjusted to 2.5 with an aqueous nitric acid solution, and thoroughly mixed and dispersed with a homogenizer (UltraTurrax T50). did. Next, 0.35 part of polyaluminum chloride was added thereto, and the dispersion operation was continued with an ultra turrax T50. Thereafter, the flask was heated to 48 ° C. while stirring the flask in an oil bath for heating, and held at 48 ° C. for 60 minutes, and then the amorphous polyester resin dispersion 1 and the amorphous polyester resin dispersion 2 were gently added thereto. Added 3 copies at a time. Thereafter, the pH of the system was adjusted to 7.8 with a 0.5 mol / l sodium hydroxide aqueous solution, and then the stainless steel flask was sealed, and heated to 89 ° C. while continuing to stir using a magnetic seal for 3 hours. Retained.

  After completion of the reaction, the mixture was cooled, filtered, sufficiently washed with ion exchange water, and then subjected to solid-liquid separation by Nutsche suction filtration. This was further redispersed in 1 L of ion exchange water at 40 ° C., and stirred and washed at 300 rpm for 15 minutes. This was repeated five more times, and when the pH of the filtrate was 7.5 and the electric conductivity was 7.0 μS / cmt, solid-liquid separation was performed using No5A filter paper by Nutsche suction filtration. The separated product is vacuum-dried for 12 hours, and is dried on a shelf, batted to a toner thickness of 5 mm to 1 cm, dried for 24 hours at an ambient temperature of 48 ° C. with ventilation, and sieved to obtain toner particles 1. It was.

  Next, 1100 parts of the above toner particles are mixed with 1.0 part of rutile type titanium oxide (volume average particle diameter: 20 nm, n-decyltrimethoxysilane treatment), silica (prepared by vapor phase oxidation method, volume average particle diameter: 40 nm, Silicone oil treatment) 2.0 parts, silica (prepared by sol-gel method, volume average particle size: 140 nm, silicone oil treatment) 2.0 parts are added, blended for 15 minutes at a peripheral speed of 30 m / s using a 5 liter Henschel mixer Then, coarse particles were removed using a sieve having an opening of 45 μm to obtain toner 1.

  The obtained toner 1 had a weight average particle diameter (D4) of 6.0 μm, an average circularity of 0.963, and a ratio of small particles of 2 μm or less was 8.5% by number.

<Production Example of Toner 2>
-Styrene / acrylic resin dispersion 1: 120 parts-Styrene / acrylic resin dispersion 2: 80 parts-Colorant dispersion: 30 parts-Release agent dispersion: 40 parts-Polyaluminum hydroxide (manufactured by Asada Chemical Co., Ltd., (Paho2S): 0.3 parts The above components were mixed in a round stainless steel flask, mixed and dispersed with a homogenizer (Ultra Turrax T50, manufactured by IKA), and then stirred while heating the flask in an oil bath for heating. Heated to ° C. After holding at 55 ° C. for 30 minutes, the particle size was measured with Coulter Multisizer 3 (manufactured by Beckman Coulter), and it was confirmed that aggregated particles having a weight average particle diameter (D4) of about 5.0 μm were formed. It was done. Further, 30 parts of styrene / acrylic resin dispersions 1 and 2 were gradually added thereto, and the temperature of the heating oil bath was raised and held at 65 ° C. for 1 hour. When the particle size was measured, it was confirmed that aggregated particles having a weight average particle diameter (D4) of about 5.8 μm were produced.

  Then, after adding 3 parts of an anionic surfactant (Neogen RK, Daiichi Kogyo Seiyaku) to the dispersion containing the aggregated particles, the stainless steel flask was sealed, and stirring was continued using a magnetic seal. Heat to 0 ° C. and hold for 4 hours. After cooling, the particle size was measured in the same manner as described above, and it was confirmed that the weight average particle size (D4) was 5.9 μm. Toner particles were filtered off from the toner particle-containing solution, washed with a sodium hydroxide solution having a pH of 10.0, and then washed with ion-exchanged water three times. Thereafter, the toner particles are freeze-dried for 6 hours and then vacuum-dried for 24 hours, and then dried on a shelf and dried for 24 hours at an ambient temperature of 48 ° C. while ventilating with a vat from 5 mm to 1 cm. And sieved to obtain toner particles 2.

  Using the obtained toner particles 2, a toner 2 was obtained in the same manner as in the production example of the toner 1. The obtained toner 2 had a weight average particle diameter (D4) of 6.1 μm, an average circularity of 0.965, and a ratio of small particles of 9.3% by number.

<Production Example of Toner 3>
Amorphous polyester resin 3: 50.0 parts by mass Amorphous polyester resin 4: 50.0 parts by mass Paraffin wax (HNP-9, manufactured by Nippon Seiki, melting point: 75 ° C): 5 parts Cyan pigment (C.I. Pigment Blue 15: 3 (copper phthalocyanine), manufactured by Dainichi Seika): 5 parts The above materials are thoroughly mixed with a Henschel mixer (FM-75 type, manufactured by Mitsui Miike Chemical Co., Ltd.), and then the temperature is increased. It knead | mixed with the biaxial kneader set to 130 degreeC (PCM-30 type | mold, Ikegai Iron Works Co., Ltd. product). 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 by thermal spheronization treatment. Surface reforming was performed at a raw material supply rate of 2.0 kg / hr and a hot air discharge temperature of 220 ° C. Next, it is classified by a wind classifier (Elbow Jet Lab EJ-L3, manufactured by Nippon Steel Mining Co., Ltd.) using the Coanda effect, and fine powder and coarse powder are simultaneously classified and removed. Further, a mechanical surface reformer (Faculty F- 100, manufactured by Hosokawa Micron Corporation), the treatment was repeated 3 times to obtain toner particles 3.

  Using the obtained toner particles 3, a toner 3 was obtained in the same manner as in the production example of the toner 1. The obtained toner 3 had a weight average particle diameter (D4) of 6.0 μm, an average circularity of 0.957, and a ratio of small particles of 12.8% by number.

  Table 5 shows the physical properties of Toners 1 to 3.

<Preparation of two-component developer>
Next, a two-component developer was prepared by combining the magnetic carrier and toner thus prepared in Table 6. The two-component developer was blended in a proportion of 92.0% by mass of magnetic carrier and 8.0% by mass of toner, and mixed for 5 minutes with a V-type mixer.

<Example 1>
As an image forming apparatus, Canon digital commercial printing printer imagePRESS C1 remodeled machine was used, and the two-component developer 1 was put in a cyan developing device to form an image for evaluation. The remodeling point is that the mechanism that discharges the excess magnetic carrier inside the developing device is removed from the developing device, and the AC voltage and DC voltage V _DC of 2.0 kHz and Vpp 1.3 kV are applied to the developer carrier. did. The DC voltage _VDC was adjusted so that the amount of toner on the paper for the FFh image (solid image) was 0.6 mg / cm ² . The FFh image is a value in which 256 gradations are displayed in hexadecimal notation, where 00h is the first gradation (white background portion) of 256 gradations and FFh is the 256th gradation (solid portion) of 256 gradations.

Under the above conditions, an endurance test of 100,000 sheets was performed using an original document (A4) with an image ratio of 5% and an FFh image, and the following evaluation was performed.
Printing environment Normal temperature and humidity environment: Temperature 23 ° C / Humidity 50% RH (hereinafter “N / N”)
Low temperature and humidity environment: Temperature 23 ° C / Humidity 5% RH (hereinafter “N / L”)
High-temperature and high-humidity environment: Temperature 30 ° C / Humidity 80% RH (hereinafter “H / H”)
Paper Laser beam printer paper CS-814 (81.4 g / m ² )
(Sold from Canon Marketing Japan Inc.)
Evaluation is based on the following evaluation methods, and the results are shown in Tables 7-9.

1. Carrier adhesion The carrier adhesion after durability was evaluated. 00h image was printed, the electrostatic latent image carrier (photosensitive drum) was sampled with a transparent adhesive tape in close contact, and the magnetic carrier particles adhered to the electrostatic charge latent image carrier in 1 cm × 1 cm The number was counted, and the number of adhered carrier particles per 1 cm ² was calculated.
A: 3 or less B: 4 or more and 10 or less C: 11 or more and 20 or less D: 21 or more Leak test (white pot)
The leak after durability was evaluated. Five solid (FFH) images are continuously output on A4 plain paper, the number of white spots with a diameter of 1 mm or more is counted in the image, and evaluation is performed from the total number of the five sheets.
A: 0 pieces B: 1 piece or more and less than 10 pieces C: 10 pieces or more and less than 20 pieces D: 20 pieces or more Density unevenness Density unevenness after durability was evaluated. Three 90h images were output on the entire surface of A4 paper, and the third image was used for evaluation. The image uniformity was evaluated by measuring the image density at five locations and determining the difference between the maximum value and the minimum value. The image density was measured with an X-Rite color reflection densitometer (Color reflection densitometer X-Rite 404A).
A: Less than 0.04 B: 0.04 or more and less than 0.08 C: 0.08 or more and less than 0.12 D: 0.12 or more Density fluctuation before and after endurance Before the endurance test, the contrast potential was adjusted so that the applied toner amount was an image density of 1.5 in the FFh image on paper. A solid image (3 cm × 3 cm) was output at 400 lines to obtain a fixed image. Next, after the endurance image output test for 100,000 sheets, the same fixed FFh image was output at the same development voltage as that before the endurance test. The difference in image density before and after durability was determined. The image density was measured with an X-Rite color reflection densitometer (Color reflection densitometer X-Rite 404A).
A: Less than 0.10 B: 0.10 or more and less than 0.15 C: 0.15 or more and less than 0.20 D: 0.20 or more The fog after endurance was evaluated. After endurance, 10 FFh images are output, then 00h image is output, and the average reflectance Dr (%) on the paper is measured by a reflectometer ("REFECTOMETER MODEL TC-6DS" manufactured by Tokyo Denshoku Co., Ltd.). It was measured. On the other hand, the reflectance Ds (%) on paper on which no image was output was measured, and the fog (%) was calculated from the following equation.
Fog (%) = Dr (%) − Ds (%)
A: Less than 0.5% B: 0.5% or more and less than 1.0% C: 1.0% or more and less than 2.0% D: 2.0% or more.

<Examples 2 to 15 and Comparative Examples 1 to 5>
Evaluation was performed in the same manner as in Example 1 except that the developer to be used was replaced with the two-component developer 2-15 and the comparative two-component developer 1-5. The evaluation results are shown in Tables 7-9.

DESCRIPTION OF SYMBOLS 1 Resin container 2 Lower electrode 3 Support base 4 Upper electrode 5 Sample 6 Electron meter 7 Processing computer A Resistance measurement cell d Sample height d1 Height without sample d2 Height with sample 10 Processing of magnetic carrier Cross section 11 Porous magnetic particle part 12 Resin part 13 Magnetic carrier surface

Claims (5)

A magnetic carrier having magnetic carrier particles in which pores of porous magnetic particles are filled with resin,
The magnetic carrier particle has a resin portion on the particle surface,
i) In a reflected electron image of the cross section of the magnetic carrier particle taken by a scanning electron microscope, a straight line that divides 72 equally from the reference point of the cross section of the magnetic carrier particle toward the surface of the magnetic carrier particle every 5 ° When (radius) is subtracted,
1) The number A of straight lines (radius) having a thickness of the resin of 0.3 μm or less measured from the distance from the surface of the magnetic carrier particles to the surface of the porous magnetic particles on the straight line (radius), 7 or more and 50 or less for 72 straight lines (radius),
2) The thickness of the resin measured from the distance from the surface of the magnetic carrier particle to the surface of the porous magnetic particle on the straight line (radius) is 1.5 μm or more and 5.0 μm or less. The number B is 7 or more and 35 or less for 72 straight lines (radius),
ii) In the reflected electron image of the cross section of the magnetic carrier particle taken by a scanning electron microscope, it passes through the reference point of the cross section of the magnetic carrier particle, and from the surface of the magnetic carrier particle to the surface every 36 °. When drawing a straight line (diameter) to divide equally,
1) The number of porous magnetic particle part regions having a length of 6.0 μm or more with respect to the total number of porous magnetic particle part regions having a length of 0.1 μm or more on the straight line (diameter) is 3. 0% to 35.0% by number,
2) The number of regions other than the porous magnetic particle portion having a length of 4.0 μm or more with respect to the total number of regions other than the porous magnetic particle portion having a length of 0.1 μm or more on the straight line (diameter). Is a magnetic carrier characterized by being 1.0% by number or more and 15.0% by number or less.   2. The magnetic carrier according to claim 1, wherein the magnetic carrier particle is a particle obtained by further coating the surface of a particle in which pores of the porous magnetic particle are filled with a resin. In the reflected electron image of the magnetic carrier particle when the acceleration voltage is 2.0 kV taken by a scanning electron microscope,
The ratio of magnetic carrier particles in which the area ratio S ₁ obtained from the following formula (1) is 0.5 area% or more and 8.0 area% or less is 80 number% or more in the magnetic carrier,
S ₁ = (total area of high luminance portion derived from porous magnetic particles on one magnetic carrier particle / total projected area of the particle) × 100 (1)
In the magnetic carrier, the average ratio Av ₁ of the total area of the high-luminance portion derived from the porous magnetic particles on the magnetic carrier particles with respect to the total projected area of the magnetic carrier is 0.5 area% or more and 8.0 area% or less. Yes,
3. The magnetic carrier according to claim 1, wherein the magnetic carrier has an average ratio Av ₂ obtained from the following formula (2) of 10.0 area% or less.
Av ₂ = (High brightness portion derived from the porous magnetic particles on the magnetic carrier particle, the total area of the portion having a domain area of 6.672 μm ² or more / derived from the porous magnetic particle of the magnetic carrier particle Total area of high brightness part) × 100 (2)   The magnetic carrier according to any one of claims 1 to 3, wherein the magnetic carrier has an electric field strength immediately before breakdown of 1300 V / cm or more and 5000 V / cm or less. A two-component developer containing a magnetic carrier and a toner,
A two-component developer, wherein the magnetic carrier is the magnetic carrier according to any one of claims 1 to 4.

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