JP2011145440A - Magnetic carrier and two-component developer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a magnetic carrier and a two-component developer which substantially avoid image density variation and carrier deposition even in long-term use and obtain an image with little roughness, few voids and little fog. <P>SOLUTION: The magnetic carrier comprises magnetic carrier particles containing a porous ferrite core particle and a resin, wherein the porous ferrite core particle contains a ferrite containing Li and Mn and has a grain diameter of 2.0-5.0 μm, the magnetic carrier contains 5.0-20.0 mass% of the resin, and a parameter α of the magnetic carrier when frequency dependent characteristics of an impedance Z obtained by AC impedance measurement are fitted by a fitting function is 0.70-0.90 under an electric field strength of 1×10<SP>3</SP>V/cm. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a magnetic carrier and a two-component developer used in an electrophotographic system, an electrostatic recording system, and an electrostatic printing system.

  Since the two-component development method uses a magnetic carrier, the triboelectric charging area for the toner is wide, so the charging characteristics are more stable than the one-component development method, which is advantageous for maintaining high image quality over a long period of time. is there. In addition, it is excellent in supplying toner to the developing area, and is often used particularly in high-speed machines. In a high-speed machine, since a greater load is applied to the developer, higher durability than ever is required.

  Then, the proposal of the magnetic carrier which becomes a magnetic carrier with small specific gravity and has high durability by using Li-Mg type complex ferrite which is a light metal type ferrite is made (refer patent document 1). According to the present invention, by controlling the amount of Mn contained in a trace amount, ferrite particles having high resistance and less variation in physical properties such as magnetic properties and surface properties can be obtained. Also good performance is obtained.

  However, there is no discussion about performance evaluation when an electrophotographic developer is combined with toner. Although the magnetic carrier as described above can be improved in durability due to its lower specific gravity, it may be inferior in developability such as a decrease in density. The cause of such a decrease in developability is that the electrode effect due to the increase in resistance of the magnetic carrier is reduced. As a result, the toner at the rear end of the halftone part is scraped off at the boundary between the halftone part and the solid black part, resulting in a white stripe, and an image defect (hereinafter referred to as a white spot) in which the edge of the solid black part is emphasized may occur. is there.

  Li-based ferrite generally has a property that it is easy to obtain an electrically high resistance ferrite, but is easily influenced by temperature and humidity. For this reason, there is room for improvement in terms of ensuring developability in various environments where the toner has poor charging startability in high temperature and high humidity environments and fogging occurs, and in low temperature and low humidity environments, the toner is excessively charged and image density is lowered. was there.

JP 2008-175883 A

  An object of the present invention is to provide a magnetic carrier and a two-component developer that are excellent in developability even in long-term use and can obtain a high-quality image.

  Specifically, it is possible to provide a magnetic carrier and a two-component developer capable of obtaining an image with little fluctuation in image density and carrier adhesion even in long-term use, and with less roughness, white spots and fogging. It is in.

  The object of the present invention can be achieved by employing the following configuration.

The present invention is a magnetic carrier having magnetic carrier particles containing at least porous ferrite core particles and a resin,
The porous ferrite core particles contain ferrite containing at least Li and Mn, and the average grain diameter is 2.0 μm or more and 5.0 μm or less,
The magnetic carrier contains at least 5.0% by mass to 20.0% by mass of resin,
When the frequency dependent characteristic of the impedance Z obtained by the AC impedance measurement is fitted by a fitting function represented by the following equation (1), the parameter α of the magnetic carrier is 0. The present invention relates to a magnetic carrier that is 70 or more and 0.90 or less.

ただし、ｉは虚数単位
ωは交流インピーダンス測定の角周波数
Ｒｓ及びＲは抵抗の次元を持つ実数パラメータ
αは０以上１以下の値をとる無次元の実数パラメータ
Ｔは（ＲＴ）^1/αが時間の次元を持つ実数パラメータ

However, i is an imaginary unit ω is an AC impedance measurement angular frequency Rs and R is a resistance dimension. A real parameter α is a value of 0 or more and 1 or less. A dimensionless real parameter T is (RT) ^{1 / α} is time. Real parameters with dimensions

  The present invention also relates to a two-component developer including a magnetic carrier and a toner, wherein the magnetic carrier is the above-described magnetic carrier.

  By using the magnetic carrier and the two-component developer of the present invention, it is possible to obtain an image with little fluctuation in image density and carrier adhesion, little roughness, little white spots and fog even in long-term use.

It is the schematic of the parameter (alpha) measuring apparatus used by this invention. This is a circuit used for fitting a Cole-Cole plot. It is a graph (1) showing a Cole-Cole plot. It is a graph (2) showing a Cole-Cole plot. It is the schematic of the measuring apparatus of the resistivity of the magnetic core particle used by this invention.

  Hereinafter, the best mode for carrying out the present invention will be described in detail.

  In the case where development is performed by bringing a developer magnetic brush into contact with the electrostatic latent image carrier, it is important to increase the electrode effect of the magnetic carrier in order to improve developability. Means for increasing the electrode effect of the magnetic carrier can be adjusted by lowering the resistivity of the ferrite core used for the magnetic carrier, or by adding a conductive agent to the coated resin in the case of a resin-coated carrier.

  However, if the resistivity of the ferrite core is too low, charge injection to the surface of the electrostatic latent image carrier occurs via the developer magnetic brush, and the image white spots due to carrier adhesion and the electrostatic latent image are disturbed. There may be some rustling.

  On the other hand, if the resistivity of the ferrite core is increased, charge injection can be suppressed even when a conductive agent is added to the coating resin. However, white spots are worsened in addition to deterioration in developability.

  As described above, it is difficult to achieve both improvement in developability and suppression of charge injection only by changing the electrode effect of the magnetic carrier by the conventional method.

The present invention is a magnetic carrier having magnetic carrier particles containing at least a porous ferrite core particle and a resin,
The porous ferrite core particles contain ferrite containing at least Li and Mn, and the average grain diameter is 2.0 μm or more and 5.0 μm or less,
The magnetic carrier contains at least 5.0% by mass to 20.0% by mass of resin,
When the frequency dependent characteristic of the impedance Z obtained by the AC impedance measurement is fitted by a fitting function represented by the following equation (1), the parameter α of the magnetic carrier is 0. It is 70 or more and 0.90 or less.

ただし、ｉは虚数単位
ωは交流インピーダンス測定の角周波数
Ｒｓ及びＲは抵抗の次元を持つ実数パラメータ
αは０以上１以下の値をとる無次元の実数パラメータ
Ｔは（ＲＴ）^1/αが時間の次元を持つ実数パラメータ

However, i is an imaginary unit ω is an AC impedance measurement angular frequency Rs and R is a resistance dimension. A real parameter α is a value of 0 or more and 1 or less. A dimensionless real parameter T is (RT) ^{1 / α} is time. Real parameters with dimensions

  It has been found that by using the structure of the magnetic carrier, both improvement in developability and suppression of charge injection can be achieved. Furthermore, it has been found that even in long-term use, it is possible to obtain an image with little fluctuation in image density and carrier adhesion, less roughness, less white spots, and less fog.

  First, the parameter α of the magnetic carrier in the present invention will be described.

  The parameter α of the magnetic carrier is a parameter corresponding to the spread of the time constant distribution existing inside the magnetic carrier particle, and it is known that the value of α becomes smaller than 1 as the spread of the time constant distribution increases. [Reference 1]. The spread of the time constant distribution appears in the frequency characteristic of the complex impedance obtained by the AC impedance measurement. When the time constant has a specific distribution, it is known that the frequency characteristic of the complex impedance follows the Cole-Cole equation expressed by the following equation (2) empirically.

（ただしｉは虚数単位、ωは交流インピーダンス測定の角周波数）
〔参考文献１〕Ｅｖｇｅｎｉｊ Ｂａｒｓｏｕｋｏｖ， Ｊ．Ｒｏｓｓ Ｍａｃｄｏｎａｌｄ ： “Ｉｍｐｅｄａｎｃｅ Ｓｐｅｃｔｒｏｓｃｏｐｙ” Ｗｉｌｅｙ Ｉｎｔｅｒｓｃｉｅｎｃｅ

(Where i is the imaginary unit, ω is the angular frequency of AC impedance measurement)
[Reference 1] Evgenij Barsoukov, J. et al. Ross Macdonald: “Impedance Spectroscopy” Wiley Interscience

  For this reason, the frequency characteristic of the complex impedance is measured by measuring the AC impedance of the magnetic carrier, and further, the value of α is obtained from the fitting by the above-mentioned Cole-Cole equation, so that the extent of the time constant of the magnetic carrier is increased. I can know. A method for measuring the parameter α will be described later.

  As a result of intensive studies by the present inventors, there is a strong correlation between the extent of the time constant distribution of the magnetic carrier particles and the developability, and the greater the spread of the time constant distribution, the better the developability. I found.

  The reason why the magnetic carrier of the present invention exhibits such excellent effects is not clear, but the present inventors speculate as follows.

  The large spread of the time constant distribution of the magnetic carrier particles is considered to be a factor that causes dispersion of the time constant of charge transfer inside the magnetic carrier particles.

  When there is a region having an extremely small time constant and a region having an extremely large time constant inside the magnetic carrier particle, when an external electric field is applied, the electric conduction inside the magnetic carrier particle is locally suppressed, It is thought that a large polarization is formed inside the particle. Due to the effect of large polarization formed inside the particles, the external electric field around the magnetic carrier particles is distorted, and the actual electric field received by the toner attached to the magnetic carrier particles is strengthened. As a result, the toner flies from the magnetic carrier particles. This is thought to be easier.

  As a result of intensive studies by the present inventors, the magnitude of the spread of the time constant distribution of the magnetic carrier particles is “variation” in the state of connection between the grains (crystal particles) of the magnetic ferrite inside the magnetic carrier particles. It was found to correlate with the size of.

  The state of connection between grains is the state of the interface (grain boundary) at the contact portion between grains. Specifically, in order to control the parameter α within the range of the present invention by providing variation in the connection state between grains, the following may be mentioned.

  Examples include morphological variations such as the area and thickness of crystal grain boundaries, variations due to composition, and variations due to spatial arrangement of crystal grain boundaries. In addition, the amount of substances segregated at the grain boundaries during the sintering process and variations in electrical resistance, the size and completeness of the crystal grains around the grain boundaries, the directivity of the magnetic field, the variation in composition distribution, etc. Variation in the state of the field.

  Here, in order that the spread of the time constant distribution of the magnetic carrier particles is large, that is, the parameter α of the magnetic carrier is within the range of the present invention, magnetic carrier particles containing at least porous magnetic ferrite core particles and a resin are used. It is necessary to have a magnetic carrier.

  The porous magnetic ferrite core particle of the present invention is a magnetic ferrite core having pores, in which the magnetic core portions are three-dimensionally connected. Therefore, compared to solid magnetic ferrite core particles, porous magnetic ferrite core particles have many crystal grain boundaries in the surface layer and inside, and the state of crystal grain boundaries tends to have “variation”. preferable.

  Furthermore, the porous ferrite core particle of the present invention is characterized by containing a ferrite containing at least Li and Mn. When the porous ferrite core particles contain ferrite containing at least Li and Mn, it is speculated that a difference in crystal structure occurs in the ferrite, and that it is possible to have further variations.

  Ferrite is a grain combination (component of ferrite) obtained by sintering fine particles of various metal oxides at a high temperature.

  There are a plurality of ferrite crystal structures, but Li-based ferrites and Mn-based ferrites have a spinel structure. There are two types of positions of metal ions in the unit cell, A and B, and each metal ion is known to enter a selective position.

  In general, Li is a monovalent metal and has a structure of 1-3 spinel coordinated at the A position. This structure differs in characteristics from 2-3 spinel formed by Cu, Zn, Ni, etc., which are divalent metals, and tends to be electrically high resistance.

  On the other hand, Mn has not only two valences but also a plurality of valences, and is said to be coordinated to both the A and B positions of the spinel structure. .

  Furthermore, when producing a ferrite containing a plurality of metal oxides, a difference occurs in the sintering rate due to the difference in constituent components. As a result, in ferrite containing Li and Mn, not only the crystal structures are different from each other, but also the valence of Mn fluctuates, so that it is likely to be a ferrite having a more non-uniform crystal structure. Therefore, in Patent Document 1, ferrite particles with little variation in crystal structure are obtained by making the amount of Mn element that causes an inhomogeneous crystal structure in the Li-based ferrite extremely small.

  On the other hand, in the present invention, it is presumed that by using the above-mentioned characteristics, it becomes a structure in which the area state of the interface, the directivity of the magnetic field, and the composition distribution are varied in the contact portion between the grains. Furthermore, in the sintering process, the polarization inside the carrier particles can be controlled by adjusting the inside of the ferrite core particles to be porous.

  In addition, in the ferrite carrier currently disclosed by patent document 1, it is guessed that the ferrite which has dispersion | distribution in the distribution of a composition as mentioned above cannot be obtained because Mn contained is very trace amount.

  Thus, by providing “variation” to the state of the crystal grain boundary inside the carrier of one particle, variation in potential barrier in electrical conduction at each crystal grain boundary occurs. In other words, the presence of an interface having an extremely small time constant to an interface having an extremely large time constant is present inside the ferrite core particle, so that when an external electric field is applied, the electric conduction inside the core particle is locally suppressed. A large polarization is formed.

  Furthermore, the magnetic carrier having such electric conduction characteristics can change the amount and presence of the resin contained in the porous ferrite core particles, or can further coat the surface of the magnetic carrier particles with the resin. Therefore, it is possible to form a large polarization inside the carrier under the application of an electric field while having an electric resistance that can prevent development injection, and it is possible to achieve both improvement in developability and suppression of charge injection. I think.

  In the magnetic carrier of the present invention, when the value of the parameter α is 0.70 or more and 0.90 or less at an electric field strength of 1000 V / cm, it is possible to achieve both improvement in developability and suppression of charge injection. As a result, it is possible to obtain an image with less image density fluctuation and carrier adhesion, less roughness, less white spots, and less fog even in long-term use. More preferably, the value of the parameter α is 0.70 or more and 0.87 or less.

  As a result of intensive studies by the present inventors, it has been found that the parameter α of the magnetic carrier measured under an electric field strength of 1000 V / cm is most correlated with the developability in the realized image region. The inventors have found that the lower the parameter α, the higher the developability of the magnetic carrier.

  Here, when determining the parameter α, the electric field strength was changed and examined, and it was found that the parameter α at the electric field strength of 1000 V / cm most correlated with the developability in the realized image region.

  This field strength of 1000 V / cm is considerably smaller than the field strength applied to the realization image area. For example, let us consider a case in which the contrast voltage (Vcont) is 350 V, the alternating voltage amplitude (Vpp) is 1300 V, and the distance between the developing sleeve and the photosensitive drum (SD distance) is 400 μm as an actual developing area.

In this realization image region, about 1000 V (Vcont: 350 V, 1/2 Vpp: 650 V), which is the sum of Vcont and Vpp, is approximately 25000 V / cm, which is a value obtained by ordering the S-D distance (400 μm). Is applied to the developer magnetic brush instantaneously.
Nevertheless, the reason why the parameter α correlates with developability in the realized image region is not clear, but the present inventors consider as follows.

  In the actual development region, the magnetic carrier carries toner, and the toner is an insulator. Therefore, it is considered that the value of the flowing current is small at the portion where the magnetic carrier contacts through the toner. On the other hand, in the situation where only the magnetic carriers are present and the magnetic carriers are in contact with each other, the voltage in the development region seems to be smaller than the voltage applied to the two-component developer. As a result, it is considered that the characteristic in the developing region of only the magnetic carrier and the parameter α at 1000 V / cm are correlated.

  When the value of the parameter α is less than 0.70, the polarization inside the magnetic carrier becomes excessive and the developability is improved, but the roughness in the halftone image is deteriorated. When the value of the parameter α exceeds 0.90, polarization in the magnetic carrier is not sufficiently generated, so that developability is deteriorated and image defects such as white spots are generated.

  Furthermore, the porous ferrite core particles of the present invention are characterized in that the average grain diameter is 2.0 μm or more and 5.0 μm or less, and more preferably 2.2 μm or more and 4.5 μm or less.

  By making the average grain diameter of the porous ferrite core particles in the above range, the pores inside the core particles are easily filled with resin. This is presumably because capillarity occurs when the resin is filled, and the core particle can be sufficiently filled through the holes extending from the surface of the core particle. By filling the resin up to the pores inside the core particle, it is possible to suppress the charging fluctuation due to the difference in use environment, which is a problem of the Li-based ferrite.

  In addition, since the resin is filled in the internal hole, the specific gravity of the magnetic carrier can be controlled to be small, and the physical strength can be sufficiently secured. As a result, the stress applied to the carrier during mixing can be reduced, and stable image quality with little fogging can be ensured even during long-term use.

  Furthermore, by adjusting the average grain diameter, the surface properties of the porous ferrite core particles are uneven due to having appropriate irregularities. As a result, the control of the parameter α becomes easier.

  When the average grain size of the porous ferrite core particles is less than 2.0 μm, it is difficult to uniformly fill the pores inside the core particles with resin, and the mixing of the toner and the carrier is lowered, so that fog is likely to occur. In addition, fluctuations in image density tend to be large under a high temperature and high humidity environment.

  When the average grain diameter of the porous ferrite core particles is larger than 5.0 μm, the bonding area between the grains becomes small, the physical strength tends to decrease, it is difficult to ensure the durability as carrier particles, and carrier adhesion is likely to occur. Become.

  Furthermore, the magnetic carrier of the present invention contains at least 5.0% by mass to 20.0% by mass of resin, more preferably 8.0% by mass to 15.0% by mass.

  By setting the amount of the resin of the magnetic carrier within the above range, excellent charging stability can be obtained regardless of the use environment, and high developability can be ensured.

  When the resin contained in the magnetic carrier is less than 5.0% by mass, the ferrite core particles cannot be sufficiently coated, so that the toner has a poor frictional charge rise property in a high temperature and high humidity environment, and the absolute value of the charge is also low. Fogging occurs.

  If the amount of resin contained in the magnetic carrier is more than 20.0% by mass, the resistance of the magnetic carrier becomes too high, so that the parameter α exceeds 0.90 or the toner is excessively charged in a low temperature and low humidity environment, and the image density Of decline.

In the magnetic carrier of the present invention, Li is preferably at least 5.0 mol% to 25.0 mol% based on Li ₂ O with respect to the total number of moles of the metal oxide contained, and is 7.0 mol% to 20 mol. More preferably, it is 0.0 mol% or less.

When Li is less than 5.0 mol% based on Li ₂ O with respect to the total number of moles of metal oxide contained in the porous ferrite core, it is difficult to reduce the specific gravity, and the stress applied during mixing may increase. is there. On the other hand, when it exceeds 25.0 mol%, the specific gravity difference between the Li component and the Mn component becomes large at the time of production, which may result in an uneven composition. In addition, sufficient magnetic force cannot be obtained and carrier adhesion may occur.

  In the magnetic carrier of the present invention, Mn is preferably at least 0.5 mol% to 10.0 mol% on the basis of MnO with respect to the total number of moles of the metal oxide contained, and 1.0 mol% to 8.0 mol. % Or less is more preferable.

  When Mn is less than 0.5 mol% on the basis of MnO with respect to the total number of moles of metal oxides contained in the porous ferrite core, the magnetic force becomes low, and it becomes difficult to vary the grain connection. There is a case. In that case, the parameter α may increase. On the other hand, when it exceeds 10.0 mol%, the average grain diameter becomes too broad, and the carrier fluidity is lowered, so that the charge is likely to be non-uniform and the fluctuation of the image density may increase.

Further, the specific resistance of the magnetic carrier of the present invention at an electric field strength of 1000 V / cm is preferably 7.0 × 10 ⁵ Ω · cm or more and 5.0 × 10 ⁷ Ω · cm or less, and 1.0 × 10 ⁶ Ω or less. More preferably, it is cm or more and 3.0 × 10 ⁷ Ω · cm or less. By making the specific resistance of the magnetic carrier in the above range, the electrode effect can be obtained more effectively, the developability in various environments is improved, and the occurrence of roughing is suppressed.

Furthermore, the specific resistance at an electric field strength of 300 V / cm of the porous magnetic core of the present invention is preferably 1.0 × 10 ⁶ Ω · cm or more and 9.0 × 10 ⁶ Ω · cm or less, and 2.0 It is more preferable that it is not less than × 10 ⁶ Ω · cm and not more than 7.0 × 10 ⁶ Ω · cm.

  By setting the specific resistance of the porous ferrite core in the above range, the polarization in the magnetic carrier particles can be further controlled, and white spots can be suppressed.

  The porous magnetic ferrite core can be manufactured by the following process.

The Li—Mn ferrite used in the present invention is a sintered body represented by the following formula.
(Li ₂ O) _a (MnO) _b (M1O) _c (M2O) _d (Fe ₂ O ₃ ) _e
(0.050 ≦ a ≦ 0.250, 0.005 ≦ b ≦ 0.100, c and d are 0.000 ≦ (c, d) ≦ 0.200, 0.650 <e <0.945, a + b + c + d + e = 1.000))

  In the above formula, M1 and M2 are divalent metals and represent one or more metal elements selected from the group consisting of Fe, Mg, Sr, Cu, Zn, Ni, Co, and Ca. In addition, the said ferrite shows a main element and may contain the trace metal element other than that.

  First, an aspect of the manufacturing process of the porous magnetic ferrite core will be described below.

Process 1 (weighing / mixing process):
The ferrite raw materials are weighed and mixed.

Examples of the ferrite raw material include the following. Li, Mn, Fe, Zn, Ni, Mg, Co, Cu, Ba, Sr, Y, Ca, Si, V, Bi, In, Ta, Zr, B, Mo, Na, Sn, Ti, Cr, Al, Examples include rare earth metal particles, oxides, hydroxides, oxalates, and carbonates. Among them, Li ₂ CO ₃ is preferable as a starting material for Li, and MnCO ₃ and Mn ₃ O ₄ are preferable as a starting material for Mn.

  Examples of the mixing apparatus include the following. Ball mill, planetary mill, Giotto mill, vibration mill. A ball mill is particularly preferable from the viewpoint of mixing properties. Specifically, a weighed ferrite raw material and balls are placed in a ball mill, and pulverized and mixed for 0.1 to 20.0 hours.

Step 2 (temporary firing step):
The ferrite raw material thus pulverized and mixed is calcined in the atmosphere at a firing temperature of 700 ° C. or higher and 1000 ° C. or lower for 0.5 hour or more and 5.0 hours or less to form a ferrite. For firing, for example, the following furnace is used. Burner type incinerator, rotary type incinerator, electric furnace.

Step 3 (grinding step):
The calcined ferrite produced in step 2 is pulverized with a pulverizer.

The pulverizer is not particularly limited as long as a desired particle size can be obtained. For example, a crusher, a hammer mill, a ball mill, a bead mill, a planetary mill, a Giotto mill, and the like can be given.
The volume-based 50% particle size (D50) of the calcined ferrite finely pulverized product is preferably 0.5 μm or more and 3.0 μm or less.

  Further, it is preferable that D90 / D50, which is the ratio of the volume-based 50% particle size (D50) and the volume-based 90% particle size (D90) of the calcined ferrite finely pulverized product to be 1.5 or more and 6.0 or less. 2.0 to 5.0 is more preferable. D90 / D50 is an index of particle size distribution, and the larger the value, the wider the particle size distribution.

In the present invention, one of the means for setting the parameter α of the magnetic carrier within a desired range is to control the particle size and particle size distribution of the calcined ferrite finely pulverized product, and the larger D90 / D50 is, It is preferable because the parameter α of the magnetic carrier can be reduced.
This is because the grain size distribution of the finely pulverized calcined ferrite product tends to cause “variation” in the state of the connection between grains (crystal grain boundary) inside the magnetic carrier particles.

  In order to make the finely pulverized calcined ferrite product have the above particle size, for example, when pulverizing using a ball mill or a bead mill, it can be achieved by controlling the material of the ball or bead, the particle size, and the operation time. Specifically, in order to reduce the particle diameter of the calcined ferrite finely pulverized product, a ball having a large specific gravity is used and the pulverization time is lengthened. Moreover, in order to widen the particle size distribution of the calcined ferrite finely pulverized product, it can be obtained by using balls and beads having a high specific gravity and shortening the pulverization time. Moreover, the calcined ferrite finely pulverized product having a wide particle size distribution can be obtained by separately adjusting and mixing the calcined ferrite finely pulverized product having different particle diameters.

The material of the balls and beads is not particularly limited as long as the desired particle size distribution can be obtained. For example, the following can be mentioned. Glasses such as soda glass (specific gravity 2.5 g / cm ³ ), sodaless glass (specific gravity 2.6 g / cm ³ ), high specific gravity glass (specific gravity 2.7 g / cm ³ ), quartz (specific gravity 2.2 g / cm) ³ ), titania (specific gravity 3.9 g / cm ³ ), silicon nitride (specific gravity 3.2 g / cm ³ ), alumina (specific gravity 3.6 g / cm ³ ), zirconia (specific gravity 6.0 g / cm ³ ), steel ( Specific gravity 7.9 g / cm ³ ), stainless steel (specific gravity 8.0 g / cm ³ ). Among these, alumina, zirconia, and stainless steel are preferable because of excellent wear resistance.

  The particle size of the ball or bead is not particularly limited as long as a desired particle size / distribution is obtained. For example, a ball having a diameter of φ5 mm or more and φ60 mm is preferably used. Further, beads having a diameter of φ0.03 mm or more and less than φ5 mm are preferably used.

  In addition, ball mills and bead mills have a high grinding efficiency when a wet method is used rather than a dry method, and a pulverized product does not rise in the mill. For this reason, the wet type is more preferable than the dry type.

Process 4 (granulation process):
Water, a binder, a dispersant, and, if necessary, a pore adjuster are added to the pulverized product of calcined ferrite.

  Examples of the pore adjuster include a foaming agent and resin fine particles. Examples of the foaming agent include sodium hydrogen carbonate, potassium hydrogen carbonate, lithium hydrogen carbonate, ammonium hydrogen carbonate, sodium carbonate, potassium carbonate, lithium carbonate, and ammonium carbonate. Examples of resin fine particles include polyester, polystyrene, styrene-vinyltoluene copolymer, styrene-vinylnaphthalene copolymer, styrene-acrylic acid ester copolymer, styrene-methacrylic acid ester copolymer, and styrene-α-chloromethacrylic acid. Styrene copolymers such as acid methyl copolymer, styrene-acrylonitrile copolymer, styrene-vinyl methyl ketone copolymer, styrene-butadiene copolymer, styrene-isoprene copolymer, styrene-acrylonitrile-indene copolymer Polyvinyl chloride, phenolic resin, modified phenolic resin, maleic resin, acrylic resin, methacrylic resin, polyvinyl acetate, silicone resin; aliphatic polyhydric alcohol, aliphatic dicarboxylic acid, aromatic dicarboxylic acid, aromatic dialcohol and Polyester resin having monomers selected from phenols as structural units; polyurethane resin, polyamide resin, polyvinyl butyral, terpene resin, coumarone indene resin, petroleum resin, hybrid resin having polyester unit and vinyl polymer unit Fine particles.

  For example, polyvinyl alcohol is used as the binder.

  In Step 3, when wet pulverization is performed, it is preferable to add a binder and, if necessary, a pore adjuster, taking into account the water contained in the ferrite slurry.

  The obtained ferrite slurry is dried and granulated using a spray dryer in a heated atmosphere of 100 ° C. or higher and 200 ° C. or lower. As the spray dryer, a conventionally known one can be used, but a spray dryer can be preferably used because the particle diameter of the obtained porous magnetic ferrite core particles can be easily controlled.

Process 5 (main baking process):
Next, the granulated product is fired. The baking is preferably performed at 800 ° C. to 1300 ° C. for 1 hour to 24 hours, more preferably 1000 ° C. to 1200 ° C.

  Here, the degree of porosity of the porous magnetic ferrite core particles can be adjusted by controlling the firing temperature and firing time within the above range. For example, by raising the firing temperature or lengthening the firing time, firing of the calcined ferrite finely pulverized product proceeds and becomes ferrite, and at the same time, coalescence of crystal particles can proceed. Thereby, a porous magnetic ferrite core in which the grains of magnetic ferrite are three-dimensionally connected can be obtained.

  As described above, the porous magnetic ferrite core having a high degree of porosity has a large number of connections between grains, and “variation” tends to occur in the connection state. Therefore, the parameter α of the obtained magnetic carrier tends to be easily reduced.

  On the other hand, if the firing temperature is set too high or the firing time is set too long, the calcined ferrite is completely united and integrated, resulting in a solid ferrite core with few or no holes. End up. Even if such a solid ferrite core is used as a magnetic carrier, the parameter α is only close to 1 and cannot be adjusted to a desired range, which is not preferable.

  It is also important to control the atmosphere during firing as a means for controlling the parameter α of the obtained magnetic carrier within a preferable range. For example, the parameter α of the obtained magnetic carrier can be reduced by firing in an atmosphere having a low oxygen concentration or in a reducing atmosphere (in the presence of hydrogen). This is probably because the oxidation of the grains composing the porous magnetic ferrite core was suppressed, and the applied development bias acts on the connection between more grains in the magnetic carrier, and apparently `` variation '' of the connection state Is estimated to increase.

Process 6 (screening process):
After pulverizing the baked particles as described above, sieving with classification or sieving to remove coarse particles and fine particles, so that the final magnetic carrier can be adjusted to the desired particle size distribution Is preferred. Furthermore, it is preferable to remove weak magnetic substances and non-magnetic substances by magnetic separation.

  The volume distribution reference 50% particle diameter (D50) of the porous ferrite core particles is more preferably 23 μm or more and 68 μm or less in order to suppress the adhesion of the carrier to the image when it becomes a magnetic carrier.

<Method for manufacturing magnetic carrier>
A magnetic carrier having magnetic carrier particles containing at least a porous magnetic ferrite core and a resin can be obtained by filling a resin in the pores of the porous magnetic ferrite core obtained by the method of steps 1 to 6 described above. it can.

  Here, a porous magnetic ferrite core filled with a resin is called a filled core. In the present invention, this filled core may be used as it is as a magnetic carrier, but it is preferable to coat the filled core with a resin to obtain a magnetic carrier excellent in environmental stability.

Process 7 (resin filling process)
In order to obtain a filled core in which the pores of the porous magnetic ferrite core are filled with resin, first, a resin solution in which a resin to be filled and a solvent in which the resin is soluble is mixed is prepared. Thereafter, a method of adding the resin solution to the porous magnetic ferrite core and impregnating the porous magnetic ferrite core particles with the resin solution and then removing only the solvent is preferable.

  The solvent used here may be an organic solvent or water as long as the resin to be filled is soluble. Examples of the organic solvent include toluene, xylene, cellosolve butyl acetate, methyl ethyl ketone, methyl isobutyl ketone, and methanol.

  The resin solid content in the resin solution is preferably 1% by mass or more and 30% by mass or less, and more preferably 1% by mass or more and 10% by mass or less.

  When the solid content of the resin in the resin solution is in the above range, the viscosity of the resin solution becomes appropriate, which is preferable because the resin solution easily enters the pores of the porous magnetic ferrite core particles. Furthermore, since the resin that has entered the pores is easily carried in the pores, the pores of the porous magnetic ferrite core particles are easily filled uniformly with the resin, which is preferable.

  If the resin is not uniformly filled into the pores, the resin may be unevenly distributed on the surface of the porous magnetic ferrite core particles, and it may appear as if the surface is covered with the resin. In such a situation, the parameter α of the magnetic carrier obtained may become large, so it is important to uniformly fill the hole with resin.

  In addition, since the porous magnetic ferrite core particles having a small particle size tend to make it difficult for the resin solution to enter the pores, it is preferable to adjust the viscosity of the resin solution to be low by reducing the solid content of the resin in the resin solution. .

  As the resin filling the pores of the porous magnetic ferrite core, either a thermoplastic resin or a thermosetting resin can be used, but it is preferable that the resin has a high affinity for the porous magnetic ferrite core. When a resin with high affinity is used, it is easy to fill the resin in the pores of the porous magnetic ferrite core, and uniform filling is possible, resulting in excellent mechanical strength, which is preferable. .

  As the resin to be filled, examples of the thermoplastic resin include the following. Polystyrene, polymethyl methacrylate, cyclohexyl methacrylate, styrene-acrylic resin; styrene-butadiene copolymer, ethylene-vinyl acetate copolymer, polyvinyl chloride, polyvinyl acetate, polyvinylidene fluoride resin, fluorocarbon resin, perfluorocarbon resin, polyvinyl Examples include pyrrolidone, 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, and polyether ketone resin. It is done.

  Moreover, the following are mentioned as said thermosetting resin. Phenolic resin, modified phenolic resin, maleic resin, alkyd resin, epoxy resin, unsaturated polyester obtained by polycondensation of maleic anhydride, terephthalic acid and polyhydric alcohol, urea resin, melamine resin, urea-melamine resin, xylene resin , Toluene resin, guanamine resin, melamine-guanamine resin, acetoguanamine resin, gliptal resin, furan resin, silicone resin, polyimide, polyamideimide resin, polyetherimide resin, polyurethane resin.

  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 the porous magnetic ferrite core.

  Among the above resins, a thermosetting resin is preferable because of excellent mechanical strength and durability of the magnetic carrier. Among these, a modified silicone resin or a silicone resin is preferable because it can reduce the adhesion between the magnetic carrier and the toner and further improve the 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. Modification).

Step 8 (resin coating):
The method of coating the surface of the filled core particles with a resin is not particularly limited, and examples thereof include a coating method such as a dipping method, a spray method, a brush coating method, and a fluidized bed.

  The amount of the resin covering the surface of the filled core particles is within the range of 0.1 parts by weight or more and 5.0 parts by weight or less with respect to 100 parts by weight of the filled core particles. It is preferable to adjust so that it may become a range.

  As the resin for forming the covering material, either the above-described thermoplastic resin or thermosetting resin may be used. Of these, fluorine-containing resins, modified silicone resins or silicone resins, and acrylic resins having an alicyclic group are preferable from the viewpoint of preventing toner spent due to their high releasability.

  The above-described resins can be used alone or in combination of two or more. In addition, a curing agent or the like can be mixed with a thermoplastic resin and cured for use. It is preferable to use a resin having a higher releasability than the above.

  Further, the coating resin may contain conductive particles, charge controllable particles, a charge control agent, a charge control resin, and a coupling agent in order to control the triboelectric chargeability.

  As the charge control substance, particles having charge controllability or materials having charge controllability can be used. 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.

  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.

  In the present invention, after the resin is filled into the porous ferrite core and / or after the surface of the filled core particle is further coated with the resin, the mechanical stress is applied during the heat treatment in order to optimize the parameter α. It is okay to spend. By applying mechanical stress to the carrier particles, the state of the particle surface (the thickness of the resin and the degree of exposure of the core particles) can be adjusted, and the parameter α can be further controlled.

  The magnetic carrier thus obtained is preferably adjusted so as to have a desired particle size distribution by sieving with a classifier such as an air classifier or an air classifier, or a sieve.

  The magnetic carrier of the present invention preferably has a volume distribution standard 50% particle size (D50) of 25 μm or more and 70 μm or less. By being in the specific range described above, it is preferable from the viewpoints of imparting triboelectric charge to the toner, carrier adhesion, and fog prevention.

  Next, the toner used in the present invention will be described.

  As the toner, toner having toner particles containing a binder resin, a colorant, and, if necessary, wax is used.

  The binder resin that can be used in the present invention has a peak molecular weight (Mp) of 2000 or more in the molecular weight distribution measured by gel permeation chromatography (GPC) in order to achieve both storage stability and low-temperature fixability of the toner. It is preferable that the number average molecular weight (Mn) is 1500 or more and 30000 or less, the weight average molecular weight (Mw) is 2000 or more and 1000000 or less, and the glass transition point (Tg) is 40 ° C. or more and 80 ° C. or less.

  The wax is preferably used in an amount of 0.5 to 20 parts by mass per 100 parts by mass of the binder resin. The peak temperature of the maximum endothermic peak of the wax is preferably 45 ° C. or higher and 140 ° C. or lower. It is preferable because both the storage stability of the toner and the hot offset resistance can be achieved.

  Examples of the wax include the following. Low molecular weight polyethylene, low molecular weight polypropylene, alkylene copolymer, hydrocarbon wax such as microcrystalline wax, paraffin wax, Fischer-Tropsch wax; oxide of hydrocarbon wax such as oxidized polyethylene wax or block copolymer thereof; Waxes based on fatty acid esters such as carnauba wax, behenic acid behenate wax, and montanic acid ester wax. In addition, fatty acid esters such as deoxidized carnauba wax may be partially or wholly deoxidized.

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

  The toner may contain a charge control agent as necessary. As the charge control agent contained in the toner, known ones can be used. In particular, a metal compound of an aromatic carboxylic acid that is colorless, has a high toner charging speed, and can stably maintain a constant charge amount is preferable.

  Negative charge control agents include salicylic acid metal compounds, naphthoic acid metal compounds, dicarboxylic acid metal compounds, sulfonic acid or polymer compounds having carboxylic acid in the side chain, sulfonates or sulfonated products in the side chain. Examples thereof include a polymer compound having a carboxylate or a carboxylate ester compound in the side chain, a boron compound, a urea compound, a silicon compound, and a calixarene.

  The charge control agent may be added internally or externally to the toner particles. The addition amount of the charge control agent is preferably 0.2 parts by mass or more and 10.0 parts by mass or less with respect to 100.0 parts by mass of the binder resin.

  It is preferable that an external additive is added to the toner in order to improve fluidity. As the external additive, inorganic fine powders such as silica, titanium oxide and aluminum oxide are preferable. The inorganic fine powder is preferably hydrophobized with a hydrophobizing agent such as a silane compound, silicone oil or a mixture thereof. The external additive is preferably used in an amount of 0.1 to 5.0 parts by mass with respect to 100.0 parts by mass of the toner particles. For mixing the toner particles and the external additive, a known mixer such as a Henschel mixer can be used.

  Examples of the method for producing toner particles include 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 are dissolved or dispersed in a solvent. Suspension granulation method in which toner particles are obtained by introducing the solution into an aqueous medium, suspending granulation, and removing the solvent; dispersing and stabilizing a monomer composition in which a colorant is uniformly dissolved or dispersed in the monomer Suspension polymerization method in which toner particles are prepared by dispersing in a continuous layer (for example, an aqueous phase) containing an agent and carrying out a polymerization reaction; monomers and aqueous systems that are soluble in monomers but become insoluble when a polymer is formed Direct dispersion in the presence of a water-soluble polar polymerization initiator using a water-based organic solvent that is soluble in the monomer that directly produces toner particles using an organic solvent and is insoluble in the resulting polymer; Toner particles An emulsion polymerization method to be produced; an emulsion aggregation method obtained by aggregating at least polymer fine particles and colorant fine particles to form a fine particle aggregate, and an aging step for causing fusion between the fine particles in the fine particle aggregate; There is.

  A procedure for producing toner by the pulverization method will be described.

  In the raw material mixing step, as a material constituting the toner particles, for example, a predetermined amount of other components such as a binder resin, a colorant and a wax, and a charge control agent as necessary are mixed and mixed. Examples of the mixing apparatus include a double-con mixer, a V-type mixer, a drum-type mixer, a super mixer, a Henschel mixer, a Nauta mixer, and a mechano hybrid (manufactured by Mitsui Mining Co., Ltd.).

  Next, the mixed material is melt-kneaded to disperse the colorant and the like in the binder resin. In the melt-kneading process, a batch kneader such as a pressure kneader or a Banbury mixer or a continuous kneader can be used, and a single-screw or twin-screw extruder has become the mainstream because of the advantage of continuous production. ing. For example, KTK type twin screw extruder (manufactured by Kobe Steel Co., Ltd.), TEM type twin screw extruder (manufactured by Toshiba Machine Co., Ltd.), PCM kneader (manufactured by Ikekai Tekko), twin screw extruder (manufactured by K.C.K. ), Ko Kneader (Bus), Needex (Mitsui Mining).

  Furthermore, the colored resin composition obtained by melt-kneading may be rolled with two rolls or the like and cooled with water in the cooling step.

  Next, the cooled product of the resin composition is pulverized to a desired particle size in the pulverization step. In the pulverization step, for example, after coarse pulverization with a pulverizer such as a crusher, a hammer mill, or a feather mill, for example, a kryptron system (manufactured by Kawasaki Heavy Industries), a super rotor (manufactured by Nisshin Engineering), a turbo mill Finely pulverize with a turbomill (made by Turbo Industries) or air jet type fine pulverizer.

  Then, if necessary, classification such as inertial class elbow jet (manufactured by Nippon Steel & Mining Co., Ltd.), centrifugal classification turboplex (manufactured by Hosokawa Micron), TSP separator (manufactured by Hosokawa Micron), Faculty (manufactured by Hosokawa Micron) The toner particles are obtained by classification using a machine or a sieving machine.

  In addition, if necessary, after pulverization, a hybridization system (manufactured by Nara Machinery Co., Ltd.), mechano-fusion system (manufactured by Hosokawa Micron Co., Ltd.), Faculty (manufactured by Hosokawa Micron Co., Ltd.), Meteorbomb MR Type (manufactured by Nippon Pneumatic Co., Ltd.) is used. Thus, the surface modification treatment of the toner particles such as spheroidization treatment can also be performed.

  When the emulsion aggregation method is used as the toner production method, the toner can be produced by the following production method.

  The emulsion aggregation method may be fine particles emulsified and dispersed in an aqueous solvent. For example, emulsified fine particles obtained by emulsion polymerization of known monomers, and emulsified fine particles obtained by adding a prepolymerized polymer together with a stabilizer into a solution in which the polymer does not dissolve, and mechanically mixing and dispersing are preferred. Used.

  These emulsified fine particles can be agglomerated by adding an aggregating agent such as an electrolyte to the emulsified dispersion with stirring, if necessary, and further heating to form fine particle aggregates.

The electrolyte used may be either an organic salt or an inorganic salt, but preferably a monovalent or divalent or higher polyvalent metal salt is used. Specific examples of such salts include NaCl, KCl, LiCl, Na ₂ SO ₄ , K ₂ SO ₄ , Li ₂ SO ₄ , MgCl ₂ , CaCl ₂ , MgSO ₄ , CaSO ₄ , ZnSO ₄ , Al ₂ (SO ₄ ) ₃ , Fe ₂ (SO ₄ ) _{3 and the} like.

  In adding the electrolyte, the temperature of the mixed dispersion is preferably kept at 40 ° C. or lower. When an electrolyte is added under conditions where the temperature exceeds 40 ° C., rapid aggregation occurs, and particle size control becomes difficult, and the bulk density of the obtained particles may be low.

  Thereafter, the mixture is heated to produce aggregated particles. The aggregated particle formation temperature may be any temperature according to the aggregated form of the particles. Stirring may be performed in a reaction tank having a normal known stirring device such as a paddle blade, squid blade, three retreat blades, Max blend blade, full zone blade, double helical, etc., homogenizer, homomixer, Henschel mixer, etc. Can also be used.

  The particle size growth by the aggregation process is carried out until particles having substantially the same size as the toner particles are obtained, but can be controlled relatively easily by adjusting the pH and temperature of the dispersion. The pH value varies depending on the type and amount of emulsifier used and the target particle size of the toner, so it cannot be uniquely defined. However, when an anionic surfactant is mainly used, the pH is usually 2 to 6, and the cationic surface activity. When an agent is used, a pH of about 8 to 12 is usually used.

  After the step of forming the fine particle aggregate, it can be obtained through an aging step for causing fusion between the fine particles in the fine particle aggregate.

  In order to increase the stability of the fine particle aggregate obtained in the aggregation step, the fine particle aggregate is held for a predetermined time at a temperature higher than the glass transition temperature (Tg) of the polymer primary particle, thereby fusing the aggregated particles. Wake up. The aging step can be performed using a stirrer similar to the stirrer used in the aggregation step.

  The toner particles obtained through each of the above steps are obtained by solid-liquid separation according to a known method, collecting the toner particles, and then washing and drying the toner particles as necessary.

  These toners may be classified to control the particle size distribution, and as a method therefor, a multi-division classifier using inertial force is preferably used.

  The magnetic carrier of the present invention can be used as a two-component developer containing toner, magnetic carrier and toner.

  The two-component developer can be used as a developer used for development by being carried on a developer carrier accommodated in a developing device.

  When used as a developer, the mixing ratio is preferably 2 to 20 parts by mass, more preferably 4 to 15 parts by mass with respect to 100 parts by mass of the magnetic carrier. By setting it within the above range, high image density can be achieved and toner scattering can be reduced.

  The magnetic carrier of the present invention is used as a replenishing developer used in a two-component developing method for mixing with a replenishing toner to replenish the developing unit, and discharging at least the excess magnetic carrier inside the developing unit from the developing unit. It can also be used.

  When used as a replenishing developer, the mixing ratio is preferably 2 parts by mass or more and 50 parts by mass or less of toner with respect to 1 part by mass of the magnetic carrier from the viewpoint of enhancing the durability of the developer.

  A method for measuring various physical properties of the magnetic carrier and toner will be described below.

<Method of measuring parameter α of magnetic carrier>
(Weighing sample)
First, a sample to be measured is sealed in a sample holder having a cylindrical electrode (diameter 2.5 cm) having an electrode area of 4.9 cm ² . The sample was weighed so that the thickness L of the sample enclosed when a pressing pressure of 100 N was applied between the electrodes was in the range of 0.95 mm to 1.05 mm.

(Explanation of measurement circuit)
Wiring is performed between the electrodes of the sample holder as shown in FIG. 1, and the AC impedance measurement of the carrier or core particles enclosed in the sample holder is performed in a state where a pressure of 100 N is applied between the electrodes of the sample holder. went.

  In this measurement, in order to obtain α under a desired electric field, AC impedance measurement is performed with a DC voltage applied. For this reason, as shown in FIG. 1, an alternating bias obtained by superimposing the DC voltage Vo on the sine wave voltage Vac is applied between the electrodes of the sample holder. Further, only the AC component of the response current flowing between the electrodes at this time was taken out and analyzed to measure the impedance under a DC electric field.

  As the impedance measuring apparatus, a 1260 type frequency response analyzer (FRA) manufactured by Solartron and a 1296 type dielectric constant measuring interface manufactured by the same company were used.

  The DC voltage Vo used for the alternating bias was obtained by amplifying a DC voltage signal output from a waveform oscillator with a PZD2000 type high voltage power source manufactured by Trek. The sine wave voltage Vac is output from the SAMPLE-HI terminal of the 1296 type dielectric constant measurement interface. Further, as shown in FIG. 1, by arranging the capacitor C1 (66 μF) and the Zener diode ZD1 (5 V) in the measurement system, the alternating bias was obtained by superimposing the DC voltage Vo on the sine wave voltage Vac.

  Further, the response current can be separated into a DC component and an AC component by using a shunt circuit using the resistor R2 (10 kΩ), the capacitor C2 (33 μF), and the Zener diode ZD2 (5 V) in FIG. it can. At this time, only the AC component flowing to the capacitor C2 side is input to the INPUT-V1-LO terminal of the 1260 type impedance analyzer and the SAMPLE-LO terminal of the 1296 type dielectric constant measurement interface, the response current waveform is analyzed, and the impedance is calculated. It was measured.

  Note that the resistor R1 (10 kΩ) in FIG. 1 is a protective resistor, and limits the maximum amount of current flowing through the measurement system.

(Measurement of complex impedance)
In this example, automatic impedance measurement was performed using impedance measurement software SMaRT manufactured by Solartron. In SMaRT, the complex impedance Z (ω) = Re [Z (ω)] + ilm [Z (ω)] with respect to the frequency f is calculated from the sine wave voltage of the predetermined frequency f and the response current to the sine wave voltage.
Can be measured. However, Re [Z] is the real part of the impedance, and Im [Z] is the imaginary part of the impedance. Further, ω is an angular frequency, and there is a relationship of ω = 2πf with the frequency f.

  In order to measure the frequency characteristics of impedance, impedance measurement was performed at a plurality of frequencies from 1 Hz to 1 MHz as the frequency f (Hz) of the sine wave voltage. The amplitude of the sine wave voltage is 1V in terms of effective value.

  As described above, a so-called Cole-Cole plot (Nyquist diagram) was created by plotting the complex impedance Z measured at a plurality of frequencies in a frequency range of 1 Hz to 1 MHz in a complex plane.

(Fitting by equivalent circuit)
Next, a method for obtaining α from complex impedance measurement data obtained by AC impedance measurement will be specifically described.

  The created Cole-Cole plot uses the Instant Fit function of the analysis software ZView2 manufactured by Solartron. Fitting was performed in correspondence with the complex impedance of the equivalent circuit shown in FIG. 2, and α was obtained as a fitting parameter of impedance measurement data.

Here, in FIG. 2, Rs and R are resistors, CPE is a circuit element called a constant phase element (constant phase element), and the frequency characteristic of the complex impedance Z _CPE of the _CPE is expressed by the following equation (3). .

Here, ω is an angular frequency of impedance measurement, and i is an imaginary unit. Α is a real number parameter from 0 to 1, and when the value of α is 1, it has the same form as the impedance Z _{C of the} capacitor expressed by the following equation (4).

  At this time, T corresponds to the capacitance C of the capacitor and has a dimension of F (farad).

The impedance of the entire equivalent circuit in FIG. 2 is expressed by the following formula, and finally by the following formula (1).
Z (ω) = Rs + (1 / R + 1 / Z _CFE ) ⁻¹
= Rs + (1 / R + 1 / ((iω) ^α T) ⁻¹ ) ⁻¹

  Note that Rs is a virtual resistance introduced into the fitting circuit in order to improve the fitting accuracy, and therefore may take a negative value.

FIG. 3 is a circuit diagram of FIG. 2 where Rs = 0Ω and R = 1 × 10 ⁵ Ω, T = 2 × 10 ⁻¹⁰ F ^α · Ω ^α-1 , α = 1.0, α = 0.9, Cole-Cole plots are shown at α = 0.8 and α = 0.7. As understood from the shape of the Cole-Cole plot, α in the above equation (4) is a parameter corresponding to the distortion of the arc drawn by the Cole-Cole plot.

  In the measurement system of this measurement, as shown in the circuit diagram of FIG. 1, when attention is paid to the path of the AC component of the response current, capacitors C1 and C2 are connected in series to the sample. For this reason, when the impedance measurement frequency is relatively low, the ratio of the impedances of the capacitors C1 and C2 may be larger than the impedance of the sample. At this time, as shown in FIG. 4, the shape of the Cole-Cole plot may greatly deviate from the arc in the frequency region II on the low frequency side. In this case, in the frequency range I on the high frequency side where the Cole-Cole plot draws an arc, fitting is performed with the equivalent circuit of FIG. 2 to obtain the value of α.

(Α under electric field)
The parameter α of the present invention under an electric field of 10 ³ V / cm was determined as follows.

  When measuring the impedance, the average electric field strength Essample applied to the sample is expressed by Vsample / L using the DC component Vsample of the voltage shared by the sample between the electrodes and the interelectrode distance L during the impedance measurement. . The value of Vsample can be measured by the difference between the potential at point a and the potential at point b shown in the circuit diagram of FIG. In this measurement, the potential at points a and b was measured using a high voltage probe P6015A manufactured by Tktronix, and the shared voltage Vsample between the electrodes of the sample holder was measured based on the difference between these potentials. Further, the value of Vsample was adjusted by changing the voltage of the DC voltage Vo output from the high voltage power supply.

In this way, impedance measurement was performed at a plurality of electric field strengths E, α under each electric field strength was obtained, and plotted on a graph to obtain carrier α under an electric field of 10 ³ V / cm.

<Measurement of resistivity of porous ferrite core particles and magnetic carrier>
The specific resistance of the porous ferrite core particles and the magnetic carrier is measured by using a measuring apparatus schematically shown in FIG.

The resistance measuring cell A includes a cylindrical PTFE resin container 21 having a hole with a cross-sectional area of 2.4 cm ² , a lower electrode (made of stainless steel) 22, a support base (made of PTFE resin) 23, and an upper electrode (made of stainless steel) 24. Composed. The cylindrical PTFE resin container 1 is placed on the support pedestal 23, the sample 25 is filled in a range of about 0.5 to 1.3 g, the upper electrode 4 is placed on the filled sample 25, and the thickness of the sample is measured. . If the thickness when there is no sample in advance is d1 (blank), and the thickness d2 (sample) when a sample of about 0.5 to 1.3 g is filled, the actual thickness d of the sample can be expressed by the following equation.
d = d2 (sample) −d1 (blank)

  At this time, it is important to appropriately change the amount of the sample so that the thickness of the sample becomes 0.95 mm or more and 1.04 mm.

  The specific resistance of the sample can be obtained by applying a voltage between the electrodes and measuring the current flowing at that time. For the measurement, an electrometer 26 (Kesley 6517A manufactured by Kesley) and a computer 27 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 inputted so that the contact area S of the sample and the electrode is S = 2.4 cm ² and the thickness of the sample is 0.95 mm or more and 1.04 mm or less. The upper electrode load is 120 g and the maximum applied voltage is 1000 V.

The voltage application condition uses the IEEE-488 interface for control between the control computer and the electrometer, and utilizes the electrometer automatic range function. Specifically, screening is performed in which voltages of 1V, 2V, 4V, 8V, 16V, 32V, 64V, 128V, 256V, 512V, and 1000V are applied for 1 second each. At that time, the electrometer determines whether it is possible to apply up to 1000 V (the electric field strength is about 10000 V / cm), and when the overcurrent flows, “VOLTAGE SOURCE OPARATE” 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, the voltage is applied in the order of 200 V, 400 V, 600 V, 800 V, 1000 V, 1000 V, 800 V, 600 V, 400 V, 200 V and 200 V increments and then decreasing. At each step, the resistance value is measured from the current value after holding for 30 seconds. Further, for example, the maximum applied voltage is 66.0 V, 13.2 V, 26.4 V, 39.6 V, 52.8 V, 66.0 V, 66.0 V, 52.8 V, 39.6 V, 26.4 V, Apply in the order of 13.2V. The current value obtained there is processed by a computer, and the electric field strength and specific resistance are calculated from the sample thickness and 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 OPARATE” blinks, and when an overcurrent flows, the resistance value is displayed as 0 for measurement. This phenomenon is defined as 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)

<Measuring method of average grain diameter of porous ferrite core particles>
The average grain diameter of the porous ferrite core particles was measured using a scanning electron microscope (SEM) and S-4800 (manufactured by Hitachi High-Technologies Corporation) under the following conditions. 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 average grain diameter of the porous ferrite core particles is calculated by the following procedure using the image analysis software Image-ProPlus 5.1J (manufactured by Media Cybernetics) for the obtained gray-scale SEM reflected electron image.

  First, the porous ferrite core particles used as a sample are porous ferrite core particles satisfying D50 × 0.9 ≦ Dmax ≦ D50 × 1.1, where Dmax is the maximum diameter of each sample. Further, in the SEM reflected electron image of the porous ferrite core particle, the horizontal ferret diameter of the particle to be measured is measured. Further, the same measurement is performed on 20 porous ferrite core particles, and the average value is used.

<Volume distribution standard 50% particle size (D50) of magnetic carrier and porous ferrite core>
The volume distribution standard 50% particle size (D50) of the magnetic carrier and the porous ferrite core is measured using a laser diffraction / scattering type particle size distribution measuring apparatus “Microtrack MT3300EX” (manufactured by Nikkiso Co., Ltd.) The measurement was performed by mounting a sample feeder “One-shot dry type sample conditioner Turbotrac” (manufactured by Nikkiso Co., Ltd.). 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: Approx. 23 ° C / 50% RH

<Weight average particle diameter of toner (D4)>
The weight average particle diameter (D4) of the toner is determined based on the precise particle size distribution measuring apparatus “Coulter Counter Multisizer 3” (registered trademark, manufactured by Beckman Coulter, Inc.) having a 100 μm aperture tube. Using the attached dedicated software “Beckman Coulter Multisizer 3 Version 3.51” (manufactured by Beckman Coulter, Inc.) for setting and analyzing the measurement data, the measurement data is measured with 25,000 effective channels. Analysis was performed and calculated.

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

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

  In the “Standard measurement method (SOM) change screen” of the dedicated software, set the total count in the control mode to 50000 particles, the number of measurements is 1 and the Kd value is “standard particles 10.0 μm” (Beckman Coulter Set the value obtained using The threshold and noise level are automatically set by pressing the threshold / noise level measurement button. Also, the current is set to 1600 μA, the gain is set to 2, the electrolyte is set to ISOTON II, and the aperture tube flash after measurement is checked.

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

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

<Measurement method of peak molecular weight (Mp), number average molecular weight (Mn), and weight average molecular weight (Mw) of resin or toner>
The peak molecular weight (Mp), number average molecular weight (Mn), and weight average molecular weight (Mw) are 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.

<Peak temperature of maximum endothermic peak of wax, glass transition temperature Tg of binder resin>
The peak temperature of the maximum endothermic peak of the wax is measured according to ASTM D3418-82 using a differential scanning calorimeter “Q1000” (manufactured by TA Instruments).

  The temperature correction of the device detection unit uses the melting points of indium and zinc, and the correction of heat uses the heat of fusion of indium.

  Specifically, about 10 mg of wax is precisely weighed, put in an aluminum pan, and an empty aluminum pan is used as a reference. Measurement is performed at 10 ° C./min. In the measurement, the temperature is once raised to 200 ° C., subsequently lowered to 30 ° C., and then the temperature is raised again. The maximum endothermic peak of the DSC curve in the temperature range of 30 ° C. to 200 ° C. in the second temperature raising process is defined as the maximum endothermic peak of the wax of the present invention.

  Further, the glass transition temperature (Tg) of the binder resin is measured by precisely weighing about 10 mg of the binder resin or toner in the same manner as the peak temperature measurement of the maximum endothermic peak of the wax. Then, a specific heat change is obtained in the temperature range of 40 ° C to 100 ° C. At this time, the intersection of the intermediate point line of the baseline before the specific heat change and after the specific heat change and the differential heat curve is defined as the glass transition temperature Tg of the binder resin.

  Specific examples of the present invention will be described below, but the present invention is not limited to these examples.

<Example of production of porous ferrite core particle 1>
Process 1 (weighing / mixing process):
Fe ₂ O ₃ 88.7 mass%
MnCO ₃ 4.6% by mass
Li ₂ CO ₃ 6.7% by mass
The ferrite raw material was weighed so that Thereafter, the mixture was pulverized and mixed for 2 hours in a dry ball mill using zirconia (φ10 mm) balls.

Step 2 (temporary firing step):
After pulverization and mixing, firing was performed in the atmosphere at 900 ° C. for 2 hours using a burner-type firing furnace to prepare calcined ferrite. The composition of ferrite is as follows.
(Li ₂ O) _a (MnO) _b (Fe ₂ O ₃ ) _c
In the above formula, a = 0.132, b = 0.588, c = 0.810

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 (φ10 mm) ball, and pulverized with a wet ball mill for 1 hour. The slurry was pulverized for 1 hour by a wet bead mill using zirconia beads (φ1.0 mm) to obtain a ferrite slurry (calcined ferrite finely pulverized product).

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, firing was performed at 1100 ° C. for 4 hours in a nitrogen atmosphere (oxygen concentration: 0.0 vol%) in an electric furnace.

Process 6 (screening process):
After the aggregated particles were crushed, the coarse particles were removed by sieving with a sieve having an opening of 250 μm to obtain porous ferrite core particles 1 having a volume distribution standard 50% particle size (D50) of 36 μm. Table 1 shows the ferrite composition and the obtained physical properties.

<Production Example of Porous Ferrite Core Particles 2 to 12>
In the production example of the porous ferrite core particle 1, the porous ferrite core particles 2 to 2 are manufactured in the same manner as in the production example of the porous ferrite core particle 1 except that the weighing value of the material is changed so as to have the ferrite composition shown in Table 1. 12 was obtained. The obtained physical properties are shown in Table 1.

<Example of production of porous ferrite core particle 13>
In the production example of the porous ferrite core particle 1,
Fe ₂ O ₃ 64.4% by mass
Mg (OH) ₂ 5.8 mass%
Li ₂ CO ₃ 29.8% by mass
The weighed value of the ferrite material was changed so that Furthermore, 0.75 part by mass of Mn ₃ O ₄ was added to 100 parts by mass of the ferrite material. Moreover, the porous ferrite core particle 13 was obtained in the same manner as in the production example of the porous ferrite core particle 1 except that the pre-baking temperature was changed to 800 ° C. and the addition amount of polyvinyl alcohol was changed to 1.0 part by mass. . The obtained physical properties are shown in Table 1.

<Production example of ferrite core particle 14>
In the production example of the porous ferrite core particle 1, the weight value of the material was changed so that the ferrite composition shown in Table 1 was obtained. Further, the ferrite core particles were made in the same manner as in the production example of the porous ferrite core particles 1 except that the pulverization time in the wet ball mill using the stainless balls in step 3 was changed to 6 hours and the firing temperature in step 5 was changed to 1300 ° C. 14 was obtained. The obtained physical properties are shown in Table 1.

  Next, an example of manufacturing a magnetic carrier will be described.

  First, a resin solution used in the present invention was obtained as follows.

<Preparation of resin liquid 1>
Straight silicone (SR2411, manufactured by Toray Dow Corning Co., Ltd.) 20.0 parts by mass in terms of solid content, 1.0 part by mass of γ-aminopropyltriethoxysilane, and 200.0 parts by mass of toluene are ball mills (soda glass balls φ10 mm ) For 1 hour to obtain a resin liquid 1.

<Preparation of resin liquid 2>
Straight silicone (SR2410, manufactured by Toray Dow Corning Co., Ltd.) in terms of solid content is 100.0 parts by mass, γ-aminopropyltriethoxysilane 8.0 parts by mass, toluene 300.0 parts by mass in a ball mill (soda glass ball φ10 mm ) Was used for 2 hours to obtain a resin liquid 2.

<Preparation of resin liquid 3>
Cyclohexyl methacrylate (Mw = 35000) in terms of solid content is 100.0 parts by mass, 6.0 parts by mass of γ-aminopropyltriethoxysilane, and 300.0 parts by mass of toluene using a ball mill (soda glass ball φ10 mm) for 2 hours. By mixing, a resin liquid 3 was obtained.

  Subsequently, the magnetic carrier was manufactured as follows.

<Manufacture example 1 of a magnetic carrier>
Step 1 (resin filling step):
100.0 parts by mass of the porous magnetic core particles 1 were placed in a stirring vessel of a mixing stirrer (universal stirrer NDMV type manufactured by Dalton). While maintaining the temperature in the stirring vessel at 30 ° C., nitrogen was introduced while reducing the pressure, and the resin liquid 1 was added dropwise to the porous magnetic core particles 1 under reduced pressure so as to be 11.4 parts by mass as a resin component. Stirring was continued for 2 hours after completion. Thereafter, the temperature was raised to 70 ° C., the solvent was removed under reduced pressure, and the silicone resin composition having the silicone resin obtained from the resin liquid 1 was filled into the core particles of the porous magnetic core 1. After cooling, the obtained magnetic carrier particles were transferred to a Julia mixer (Tokuju workshop), heat-treated at a temperature of 200 ° C. for 2 hours in a nitrogen atmosphere, and then classified with a sieve having an opening of 70 μm to obtain filled core particles 1.

Process 2 (resin coating process):
Put 100.0 parts by mass of packed core particles 1 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 supply air temperature to The temperature was 80 ° 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. Coating was performed until the amount of the coating resin reached 0.8 parts by mass with respect to 100.0 parts by mass of the filled core particles 1 to obtain a magnetic carrier.

  Thereafter, the magnetic carrier coated with the silicone resin was transferred to a mixer (drum mixer UD-AT type manufactured by Sugiyama Heavy Industries Co., Ltd.) having spiral blades in a rotatable mixing container. The mixture container was heat-treated at a temperature of 200 ° C. for 2 hours under a nitrogen atmosphere while stirring at 10 rotations per minute. By stirring, the resin thickness state of the surface of the magnetic carrier particles was controlled. The obtained magnetic carrier was passed through a sieve having an opening of 70 μm to obtain a magnetic carrier 1. The parameter α of the obtained magnetic carrier 1 was 0.76.

  Table 2 shows the type, amount, and physical properties of the resin in the resin filling step and the resin coating step of the magnetic carrier 1.

<Example of production of magnetic carriers 2 to 14>
Magnetic carriers 2 to 14 were obtained by changing the type and amount of the filled resin in the resin filling step and the type and amount of the resin in the resin coating step as shown in Table 2. The obtained physical properties are shown in Table 2.

  Next, an example of toner production will be described.

<Example of toner production>
The following materials were weighed in a reaction vessel equipped with a cooling tube, a stirrer, and a nitrogen introducing tube.
Terephthalic acid 288 parts by mass polyoxypropylene (2.2) -2,2-bis (4-hydroxyphenyl) propane
880 parts by mass Titanium dihydroxybis (triethanolamate) 1 part by mass Thereafter, the mixture was heated to 190 ° C. and reacted for 10 hours while removing water produced while introducing nitrogen. Further, 61 parts by mass of trimellitic anhydride was added, heated to 170 ° C., and reacted for 2.5 hours to synthesize Resin 1.

  The molecular weight of the resin 1 determined by GPC was a weight average molecular weight (Mw) of 64000, a number average molecular weight (Mn) of 5500, a peak molecular weight (Mp) of 10100, and a glass transition point (Tg) of 60 ° C.

Resin 1 100.0 parts by mass Purified normal paraffin (DSC maximum endothermic peak 65 ° C.) 5.0 parts by mass C.I. I. Pigment Blue 15: 3 5.0 parts by mass After the above materials were thoroughly mixed with a Henschel mixer (FM-75 type, manufactured by Mitsui Miike Chemical Co., Ltd.), a twin-screw kneader (PCM-30 set at a temperature of 120 ° C.) Melt kneaded into a mold, manufactured by Ikekai Tekko Co., Ltd. The obtained kneaded product was cooled and coarsely pulverized to 1 mm or less with a hammer mill to obtain a coarsely pulverized product 1.

  Next, the obtained coarsely pulverized product 1 was produced using a turbo mill (T-250: RSS rotor / SNB liner) manufactured by Turbo Industry Co., Ltd. to produce a finely pulverized product 1 having a size of about 5 μm.

  Next, the finely pulverized product 1 obtained was classified using a rotary classifier (200TSP, manufactured by Hosokawa Micron Corporation) to obtain toner particles. The obtained toner particles had a weight average particle diameter (D4) of 5.6 μm.

  To 100.0 parts by mass of the obtained toner particles, 1.0 part by mass of titanium oxide (STT-30A; manufactured by Titanium Industry Co., Ltd.) and 1.0 part by mass of silica (AEROSIL R972; manufactured by Nippon Aerosil Co., Ltd.) were externally added. The toner was obtained by mixing.

[Example 1]
Next, a two-component developer was prepared with the magnetic carrier 1 and the toner thus prepared. 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.

<Developability evaluation>
A Canon digital commercial printing printer imagePRESSC1 was used as an image forming apparatus, and the above two-component developer was put in a developing device at a cyan position 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 1.8 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 of the FFh image (solid image) was 0.45 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 50000 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 60% RH (hereinafter “N / N”)
High-temperature and high-humidity environment: Temperature 30 ° C / Humidity 80% RH (hereinafter “H / H”)
Normal temperature and low humidity environment: Temperature 23 ° C / Humidity 5% RH (hereinafter "N / L")
Paper Copy paper CS-814 (basis weight 81.4g / m ² )
(Sold from Canon Marketing Japan Inc.)

  Evaluation is based on the following evaluation methods, and the results are shown in Table 3.

[Evaluation methods and standards]
1) Change in image density after endurance The change in image density before and after endurance in each environment was evaluated.

In each environment, the development voltage was initially adjusted so that the applied amount of toner on the FFh image was 0.45 mg / cm ² . Using an X-Rite color reflection densitometer (500 series: manufactured by X-Rite), three FFh images each having a size of 5 cm × 5 cm were output, and the image density of the third sheet was measured. The difference in image density between the initial durability and after the durability was evaluated according to the following criteria.
A: 0.00 or more and less than 0.05 (very good)
B: 0.05 or more and less than 0.10 (good)
C: 0.10 or more and less than 0.20 (Acceptable level in the present invention)
D: 0.20 or more (not acceptable in the present invention)

2) Dot reproducibility (assessment of roughness)
The dot reproducibility before and after endurance in N / N and H / H was evaluated.
A dot image (FFh image) in which one pixel is formed by one dot was created. The spot diameter of the laser beam was adjusted so that the area per dot on the paper was 20000 μm ² or more and 25000 μm ² or less. The area of 1000 dots was measured using a digital microscope VHX-500 (lens wide range zoom lens VH-Z100, manufactured by Keyence Corporation). The number average (S) of dot areas and the standard deviation (σ) of dot areas were calculated, and the dot reproducibility index was calculated by the following formula.
Dot reproducibility index (I) = σ / S × 100
A: I is less than 4.0 (very good)
B: I is 4.0 or more and less than 6.0 (good)
C: I is 6.0 or more and less than 8.0 (Acceptable level in the present invention)
D: I is 8.0 or more (not acceptable in the present invention)

3) White spot evaluation White spots before and after endurance in N / N and N / L were evaluated.

A chart in which halftone horizontal bands (30H width 10 mm) and solid black horizontal bands (FFH width 10 mm) are alternately arranged in the transfer paper conveyance direction is output. The image is read by a scanner and binarized. The luminance distribution (256 gradations) of a certain line in the carrying direction of the binarized image is taken. Draw a tangent line to the brightness of the halftone at that time, and the brightness area (area: sum of brightness numbers) that deviates from the tangent at the rear end of the halftone part until it intersects with the solid part brightness. Based on the evaluation.
A: Less than 50 (very good)
B: 50 or more and less than 200 (good)
C: 200 or more and less than 400 (Acceptable level in the present invention)
D: 400 or more (not acceptable in the present invention)

4) Fog The fog before and after durability in N / N and H / H was evaluated.

  Ten 00h images were output in each environment, and the average reflectance Dr (%) on the tenth sheet of paper was measured with a reflectometer (“REFLECTOMETER MODEL TC-6DS” manufactured by Tokyo Denshoku Co., Ltd.).

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% (very good)
B: 0.5% or more and less than 1.0% (good)
C: 1.0% or more and less than 2.0% (Acceptable level in the present invention)
D: 2.0% or more (not acceptable in the present invention)

5) Carrier adhesion The carrier adhesion before and after endurance in N / N was evaluated.

A halftone image (30h image) was printed, and the number of magnetic carriers present in an area of 1 cm ² on the halftone image was counted with an optical microscope to calculate the number of adhered carrier particles per 1 cm ² .
A: Less than 5 (very good)
B: 5 or more and less than 10 (good)
C: 11 or more and less than 20 (Acceptable level in the present invention)
D: 20 or more is not acceptable in the present invention)

[Examples 2 to 9 and Comparative Examples 1 to 5]
Evaluation was performed in the same manner as in Example 1 except that the combination of the magnetic carrier and the toner was changed. The evaluation results are shown in Table 3.

  D: SD gap, Z: Dielectric constant measuring device, 21: Resin container, 22: Lower electrode, 23: Support base, 24: Upper electrode, 25: Sample, 26: Electron meter, 27: Processing computer, A: Resistance measurement Cell, d: sample height, d1 (blank): height without sample, d2 (sample): height with sample

Claims (2)

A magnetic carrier having magnetic carrier particles containing at least porous ferrite core particles and a resin,
The porous ferrite core particles contain ferrite containing at least Li and Mn, and the average grain diameter is 2.0 μm or more and 5.0 μm or less,
The magnetic carrier contains at least 5.0% by mass to 20.0% by mass of resin,
When the frequency dependent characteristic of the impedance Z obtained by the AC impedance measurement is fitted by a fitting function represented by the following equation (1), the parameter α of the magnetic carrier is 0. A magnetic carrier characterized by being 70 or more and 0.90 or less.

However, i is an imaginary unit ω is an AC impedance measurement angular frequency Rs and R is a resistance dimension. A real parameter α is a value of 0 or more and 1 or less. A dimensionless real parameter T is (RT) ^{1 / α} is time. Real parameters with dimensions   A two-component developer containing at least a magnetic carrier and a toner, wherein the magnetic carrier is the magnetic carrier according to claim 1.

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