JP5020696B2 - Magnetic toner - Google Patents

Description

  The present invention relates to a magnetic toner used in an image forming method such as an electrophotographic method, an electrostatic printing method, a magnetic recording method, and a toner jet method.

  Many methods are known as electrophotographic methods. In general, a photoconductive substance is used to form an electrical latent image (electrostatic latent image) on a photoreceptor by various means, and the latent image is developed using toner, and a transfer material is used as necessary. After the toner image is transferred to the toner image, the toner image is fixed by heating, pressing, heating and pressing, or solvent vapor to obtain an object to be copied. The developer remaining without being transferred onto the photoreceptor is cleaned by various methods, and the above steps are repeated.

  Among these, the one-component development method is preferably used as the development method because the development device with a simple structure has few troubles, a long life, and easy maintenance.

  In such a developing system, the quality of the formed image is greatly influenced by the performance of the magnetic toner. A considerable amount of fine powdered magnetic iron oxide is mixed and dispersed in the magnetic toner, and a part of the magnetic iron oxide is exposed on the surface of the magnetic toner. For this reason, the type of magnetic iron oxide affects the fluidity and tribocharging properties of the magnetic toner, and as a result, affects various properties required for the magnetic toner, such as magnetic toner development characteristics and durability. For this reason, many proposals have been made regarding magnetic iron oxide contained in magnetic toners.

  As magnetic iron oxide, there is known magnetic iron oxide that contains Si, defines the Fe / Si atomic ratio of the outermost surface of magnetic iron oxide, and is further subjected to surface treatment with Al (Patent Document 1). Although such magnetic iron oxide has excellent fluidity and stable charging characteristics even at high temperatures and high humidity, it has further improved image quality such as ghosting and scattering caused by charging characteristics in high-speed development systems. There was room for improvement.

  As magnetic iron oxide, magnetic iron oxide containing Al, further hydrophobized, and defining magnetic properties is known (Patent Document 2). In these magnetic iron oxides, a part or all of trivalent iron is replaced by Al, and the saturation magnetization value is low. By using such magnetic iron oxide, it is possible to obtain a toner that has a weak magnetic cohesion between the toner particles and can reduce consumption. Further, it is possible to obtain a magnetic toner that has good storage stability even in a high temperature and high humidity environment, can maintain a sufficient image density, and further suppresses occurrence of fogging and tailing. In addition, since the amount of divalent iron and the amount of FeO in the magnetite are maintained, a magnetic toner having good blackness can be provided. However, sufficient studies have not been made on the deterioration of image quality due to non-uniform charging in the case of long-term use and the instability of image quality under low temperature and low humidity.

  Magnetic iron oxide is known which contains Si and Al elements and defines the Si and Al content ratio on the surface of magnetic iron oxide (Patent Document 3). By using such magnetic iron oxide, the charge controllability can be improved compared to the conventional one, and even in continuous image output in a low temperature and low humidity environment, the magnetic property with excellent uniformity of the coat on the toner carrier is obtained. Toner can be obtained. When such a magnetic toner is used, image defects such as blurring and wavy unevenness are suppressed even in a solid image, and a high-quality and sharp image can be obtained. However, sufficient studies have not been made on the stability of image density in a high temperature and high humidity environment.

  Also known as magnetic iron oxide is magnetic iron oxide containing one or more elements selected from the group consisting of Li, Be, B, Mg, Al, Si, P, Ge, Ti, Zr, Sn, and Zn. (Patent Document 4). Such magnetic iron oxide has excellent dispersibility in the binder resin, and can stabilize the chargeability of the toner. And in the trend of reducing the particle size of toner in recent years, even when a toner having an average particle size of 10 μm or less is used, excellent charging uniformity is obtained, toner cohesion is reduced, and high image density is obtained, It is possible to form an image having excellent developability in which fog and the like are suppressed. However, sufficient studies have not been made on the improvement of dot reproducibility, the reduction of tailing, and the improvement of environmental stability in terms of chargeability.

  As a magnetic iron oxide containing a different element, an element selected from the element group consisting of Mg, Na, K, Ca, Li, Ti, S, Al, Si, B, and C is contained outside the center portion, and 20 Magnetic iron oxide having a true specific gravity at 4 ° C. of less than 4 to 5.2 is known (Patent Document 5). Such magnetic iron oxide has a good balance of magnetic properties, a small true density, and a good mixing property with a resin. When used in a magnetic toner, it is possible to obtain a magnetic toner having a high image density, a low fog, and a small amount of magnetic iron oxide powder falling off from the toner particles. However, there is still room for improvement regarding image quality improvement and environmental stability.

  Further, it contains Al, and further contains one or more metal elements selected from the element group consisting of Co, Ni, Cu and Zn, and is contained in the content of the metal elements and magnetic iron oxide. A magnetic material that defines the ratio of the total amount of Al to the amount of Al present on the surface is known (Patent Document 6). By using such magnetic iron oxide, it is possible to obtain a magnetic toner having excellent fluidity, stable developability, and hardly causing toner fusion to the photoreceptor even in long-term use. However, there is still room for consideration in improving image quality such as ghosting and scattering.

  Further, magnetic iron oxide containing an element selected from the group consisting of Mg, Al, Si, P, S, Ca, Cu, and Zn, a hydrocarbon wax having a predetermined hydroxyl value and ester value, and styrene- There is also a document describing a technique in which magnetic iron oxide and wax are uniformly dispersed in toner particles using an acrylic copolymer in combination (Patent Document 7). With such a toner, a magnetic toner capable of suppressing deterioration and a decrease in charge and capable of forming a stable image even during long-term durability can be obtained. However, the case where a polyester resin is used as the binder resin is not taken into consideration, and the case where the particle size of the toner has been reduced has been insufficiently studied.

  Magnetic iron oxide containing an element selected from the group consisting of Al, Si, P, Ti, V, Cr, Mn, Co, Ni, Cu, Zn, Ga, Ge, Zr, Sn, and Pb and a crosslinking system A technique has also been proposed in which both the performance of the resin and the dispersibility of the magnetic iron oxide are achieved in combination with other vinyl resins (Patent Document 8). In this case, it is possible to obtain a toner having stable developability and durability while maintaining low-temperature fixability. However, sufficient studies have not been made on the problem of tailing when the particle size is reduced.

  Further, magnetic iron oxide having a main crystal structure of magnetite and containing amorphous Al almost uniformly is known (Patent Document 9). Such a magnetic iron oxide is a magnetic material having low resistance and low remanent magnetization, a high proportion of FeO, and good blackness. However, generally, electrophotographic toners require resistance values close to insulating properties, and such low-resistance magnetic iron oxides are difficult to use.

  As described above, in the magnetic iron oxide for magnetic toner, studies have been made so far to provide excellent fluidity and environmental stability of charge amount by containing different metals, but there is room for improvement of various problems. What is left is the current situation.

JP 7-175262 A Japanese Patent Laid-Open No. 7-271089 JP-A-8-272136 Japanese Patent Laid-Open No. 10-073950 JP 2000-335920 A JP 2002-169328 A JP 2003-122044 A Japanese Patent Laid-Open No. 2003-221813 JP 2005-170689 A

An object of the present invention is to provide a magnetic toner that solves the above-described problems.
That is, an object of the present invention is to provide a magnetic toner capable of obtaining an image having high image density and excellent image reproducibility.
Another object of the present invention is to provide a magnetic toner that is excellent in fluidity, charging stability, and charging uniformity even in long-term use, and can obtain an image in which fogging, ghosting, and scattering are suppressed. is there.

As a result of intensive research, the inventors have obtained a magnetic toner having at least a binder resin and a magnetic material, and the magnetic material is a magnetic iron oxide having a dielectric breakdown voltage of 160 to 1600 V / cm, Since the magnetic toner has a dielectric loss tangent (tan δ) at 100 kHz and 40 ° C. of 2.0 × 10 ^{−3 to} 1.0 × 10 ⁻² , the image density is high even in long-term use, and fogging, ghosting and scattering are caused. It has been found that a magnetic toner can be obtained which can provide a non-image.

  High developability can be maintained even during long-term use in harsh environments such as high temperature, high humidity, and low temperature and low humidity, and image problems caused by reduced charging and uneven charging such as fogging, ghosting, and scattering are suppressed. A magnetic toner capable of obtaining a high-quality image is provided.

  As a result of examining the constituent materials of the magnetic toner, the present inventors have found that the dielectric breakdown voltage of a magnetic material made of magnetic iron oxide is closely related to the developability of the magnetic toner. Further, the inventors have found that the magnetic substance is sufficiently dispersed in the magnetic toner, so that the charge adjusting ability as the magnetic toner is sufficiently exhibited.

  In the present invention, magnetic iron oxide is used as the magnetic material, and the magnetic material has a dielectric breakdown voltage of 160 to 1600 V / cm, preferably 400 to 900 V / cm, more preferably 600 to 800 V / cm. When the dielectric breakdown voltage of the magnetic material is within the above range, it is possible to balance the suppression of triboelectric charge leakage and the suppression of charge-up. Furthermore, non-uniform charging of the toner can be suppressed, and when a high printing area image is continuously developed, the density of the subsequent image is lowered and a difference in density is produced on the image. Occurrence can be suppressed. Further, even after endurance in a high temperature environment, transfer defects, scattering, and fogging can be suppressed.

  That is, in the present invention, the dielectric breakdown voltage of the magnetic material is 160 to 1600 V / cm, thereby improving nonuniform charging and charging instability caused by the leakage of triboelectric charge on the magnetic toner surface. Can do. Further, overcharging can be suppressed, and the charge amount of the magnetic toner can be maintained at an appropriate value. As a result, high image density can be maintained regardless of the environment, and phenomena such as ghost, scattering, and fog can be suppressed.

The dielectric breakdown voltage of the magnetic material is measured by the following method according to JIS C 2161.
Weigh 2 g of the magnetic material, apply a pressure of 13720 kPa (140 kg / cm ² ) using a tablet molding machine with an inner diameter of 1.3 cm, and apply a pressure sample with an area of 1.33 cm ² and a thickness of 0.50 to 0.60 cm. Make it. Place the pressure sample on the stainless steel electrode plate. At that time, the stainless steel electrodes are completely separated from the outside by a fluororesin holder. A predetermined voltage is applied in the range of 10 V to 1000 V using a resistance measuring device (manufactured by YOKOGAWA-HEWLETT-PACKARD: 4329A HIGH RESISTANCE METER) to measure the resistance value R of the pressurized sample. The measurement is started from a place where the applied voltage is low, and when the applied voltage becomes high to some extent, dielectric breakdown occurs and the resistance value R becomes impossible to measure. The maximum applied voltage value before this breakdown occurs is the breakdown voltage. The measurement is performed in an environment of 23 ° C. and 50% RH, and the pressurized sample is used after being conditioned and humidity-controlled for 24 hours in the same environment.

  The dielectric breakdown voltage of the magnetic material can be controlled by incorporating a different metal such as Al, Mn, and Zn into the magnetic material. In particular, a wide range of control is possible by forming a coating layer of metal oxide such as Al, Mn, Zn or metal hydrate on the surface of the magnetic particles. In order to develop a very high breakdown voltage while maintaining the desired magnetic characteristics, it is most preferable to contain Al.

  The magnetic body preferably contains 0.5 to 5.0% by mass of Al, more preferably 1.0 to 3.0% by mass, and still more preferably 1.0 to 2.0% by mass. . When the Al content is in the above range, the surface of the magnetic material can be appropriately covered with Al, and it is possible to achieve a good balance between suppression of triboelectric charge leakage and suppression of charge-up. become able to. Also, good fluidity can be obtained.

In addition, the magnetic substance contains the following formula: Al dissolution rate (S1) (%) = {(Amount of Al dissolved when the magnetic substance is washed with a 1 mol / liter sodium hydroxide aqueous solution) / (contained in the magnetic substance) Total Al amount)} × 100
Is preferably 40 to 60% by mass, and more preferably 45 to 60% by mass. When the Al dissolution rate (S1) is within this range, the effect of controlling the triboelectric charge amount is particularly enhanced.
Since a 1 mol / liter sodium hydroxide aqueous solution does not penetrate into the inside of the magnetic material, the Al dissolved by the aqueous solution is only Al present in the vicinity of the surface of the magnetic material. Therefore, the Al dissolution rate (S1) represents the proportion of Al present in the vicinity of the magnetic surface.

  Moreover, it is preferable that a magnetic body has a coating layer containing Al on the surface while containing Al inside. In this case, the coating layer containing Al on the surface of the magnetic material becomes denser, the electric resistance value of the magnetic toner increases, and a stable charge amount can be maintained even in an environment of high temperature and high humidity or low temperature and low humidity. Can do. Moreover, since such a magnetic body is excellent in fluidity | liquidity, generation | occurrence | production can also be suppressed regarding the particle aggregation which is a problem in the magnetic body of a small particle diameter.

Furthermore, in the process of dissolving the magnetic substance in a 1 mol / liter hydrochloric acid aqueous solution, the magnetic substance has an Al content relative to the total amount of Al contained in the magnetic substance when the Fe dissolution rate (iron dissolution rate) is 20% by mass. The dissolution rate (S2) is preferably 60 to 85% by mass. And it is preferable that Al dissolution rate (S3) with respect to the total amount of Al contained in this magnetic body is 80 to 95 mass% when the Fe dissolution ratio is 60 mass%. Furthermore, when the Fe dissolution rate is 80% by mass, the Al dissolution rate (S4) with respect to the total amount of Al contained in the magnetic material is preferably 95 to 99% by mass. The Al dissolution rate (S2) is more preferably 70 to 85% by mass, and the Al dissolution rate (S3) is more preferably 90 to 95% by mass.
The aluminum dissolution rates (S2) to (S4) are represented by the following formulas.
Aluminum dissolution rate (S2) (%) = {(in the process of dissolving the magnetic material in 1 mol / liter hydrochloric acid aqueous solution, the amount of dissolved Al when the Fe dissolution rate is 20% by mass) / (contained in the magnetic material) Total Al amount)} × 100
Aluminum dissolution rate (S3) (%) = {(In the process of dissolving the magnetic material in 1 mol / liter hydrochloric acid aqueous solution, the amount of dissolved Al when the Fe dissolution rate is 60% by mass) / (contained in the magnetic material) Total Al amount)} × 100
Aluminum dissolution rate (S4) (%) = {(in the process of dissolving the magnetic material in 1 mol / liter hydrochloric acid aqueous solution, the amount of dissolved Al when the Fe dissolution rate is 80% by mass) / (contained in the magnetic material) Total Al amount)} × 100
Note that the Fe dissolution rate in the above equation is represented by the following equation.
Fe dissolution rate (%) = {(Amount of Fe dissolved at a certain point in the process of dissolving the magnetic substance with 1 mol / liter of hydrochloric acid aqueous solution) / (Total amount of Fe contained in the magnetic substance)} × 100
“When the Fe dissolution rate reaches 20% by mass” means that a magnetic substance is put into a 1 mol / liter hydrochloric acid aqueous solution and begins to dissolve from the surface. It is the time of dissolution, and substantially corresponds to the time of dissolution of 20% by mass from the surface of the magnetic material. And "Al dissolution rate (S2) with respect to the total amount of Al contained in the magnetic material when the Fe dissolution rate is 20% by mass" means Al contained in a region of 20% by mass from the surface of the magnetic material. Is equivalent to

  In order for the magnetic material to exhibit good electrical characteristics, and particularly to exhibit a sufficient effect when used in a magnetic toner having a small particle diameter, the total content of Al, the surface abundance, and the presence state of the above-described It is preferable to satisfy the regulations. Further, in this case, the magnetic characteristics are also good. In addition, when Al is present in the above-described state, the adhesion of the coating layer containing Al to the magnetic mother particles is improved by the influence of Al contained in the magnetic substance, and the denser It becomes easy to form a coating layer.

The magnetic material preferably has a magnetite crystal structure. And about Al contained in the inside of a magnetic body, it is preferable not to be taken in in a magnetite crystal but to exist in magnetite in an amorphous state.
Furthermore, the magnetic material preferably contains at least one of group 2 metals (Mg, Ca, Sr, Ba) in addition to Al, and preferably contains Mg. When a Group 2 metal is used, the coating layer is formed more densely, and a breakdown voltage within the range specified by the present invention is easily obtained. . Although the detailed mechanism has not been elucidated, the inventors have coordinated magnetite with Mg ²⁺ with coordination selectivity in the crystal lattice, and MgAl ₂ having the same crystal structure as magnetite. Since O ₄ can be formed, it is considered that a dense coating layer as described above is formed.

  However, when the present inventors confirmed by X-ray diffraction, the diffraction peak of the magnetic material used in the present invention is dominated by the strong diffraction peak of magnetite, and most of the diffraction peaks derived from other crystal structures are observed. Was not. That is, in the magnetic material, the Al component exists as a compound in an amorphous form.

  The content of Al and other dissimilar elements in the magnetic material is determined using a fluorescent X-ray analyzer SYSTEM 3080 (manufactured by Rigaku Denki Kogyo Co., Ltd.) according to JIS K 0119 “General rules for fluorescent X-ray analysis”. Measure by performing quantitative analysis.

  The crystal structure of magnetic iron oxide can be analyzed by measuring the lattice constant with an X-ray diffractometer.

  Further, the Al dissolution rate and Fe dissolution rate, which indicate the distribution of Al in the magnetic material, can be obtained by the following method.

  First, about 3 liters of deionized water is put into a 5 liter beaker and heated in a water bath to 45 to 50 ° C. 25 g of the magnetic material is made into a slurry with 400 ml of deionized water, and the slurry is further washed with 300 ml of deionized water while being added to a heated 5 liter beaker to prepare a magnetic material dispersion.

1) Washing of magnetic substance using aqueous sodium hydroxide solution When washing magnetic substance with aqueous sodium hydroxide solution, the temperature of the magnetic substance dispersion in a 5 liter beaker is kept at about 50 ° C. while stirring at 200 rpm. Deionized water and special grade sodium hydroxide are added so that the magnetic substance concentration is 5 g / liter and the sodium hydroxide aqueous solution concentration is 1 mol / liter. Thereafter, dissolution of metals other than Fe on the surface of the magnetic particles is started. After standing for 30 minutes, the solution is filtered through a 0.1 μm membrane filter, and 20 ml of the filtrate is collected. Then, the concentration of Al in the collected filtrate is quantified by a plasma emission spectroscopy (ICP) measurement device.

2) Dissolution of magnetic substance with aqueous hydrochloric acid When dissolving in acid, the magnetic substance concentration in the 5 liter beaker is 5 g / liter, and the concentration of aqueous hydrochloric acid is 1 mol / liter. Deionized water and special grade hydrochloric acid are added, the temperature is maintained at about 50 ° C., and dissolution is performed while stirring at 200 rpm. When the total amount of the magnetic material is dissolved, a mixed acid may be added, and the concentration may be about 3 mol / liter.

  Collect the dissolved solution at 10-minute intervals until all the magnetic materials are dissolved and become transparent, filter the dissolved solution through a 0.1 μm membrane filter, and collect about 20 ml of the filtrate. Then, the concentration of Al and Fe in the collected filtrate is quantified by a plasma emission spectroscopy (ICP) measuring device.

  From the obtained results, the Al dissolution rate and the Fe dissolution rate in each sample collected at 10-minute intervals were obtained, the Al dissolution rate was plotted against the Fe dissolution rate, and the results were smoothly tied to the Al dissolution rate relative to the Fe dissolution rate. Get the curve.

  The Al dissolution rate (S1) can be calculated from the Al concentration when the magnetic material is washed with an aqueous sodium hydroxide solution and the Al concentration when the magnetic material is completely dissolved with an aqueous hydrochloric acid solution. Moreover, Al dissolution rate (S2)-(S4) can be calculated | required from the curve of Al dissolution rate with respect to said Fe dissolution rate.

  The magnetic material preferably has an isoelectric point of pH 7.0 or more and 10.0 or less, more preferably pH 8.0 or more and 10.0 or less, and still more preferably pH 9.0 or more and 10.0 or less. The isoelectric point of magnetite is about pH 6.5. In general, the isoelectric point is affected by the amount of different elements added and the state of existence of different elements on the surface of the magnetic material. When the isoelectric point is within the above range, it is considered that the surface of the magnetic material is sufficiently covered with Al, and good fluidity is obtained. As the magnetic toner, nearly uniform chargeability can be obtained, and ghost and image density reduction can be suppressed.

The isoelectric point of the magnetic material is measured by the following method.
First, the magnetic material is dispersed in ion exchange water at 25 ° C., and the sample concentration is adjusted to 1.8% by mass. Using an ultrasonic zeta potential measuring device DT-1200 (manufactured by Dispersion Technology), titration with 1 mol / liter hydrochloric acid aqueous solution or sodium hydroxide aqueous solution is performed to measure the zeta potential. The isoelectric point is the pH when the zeta potential is 0 mV.

In addition, the magnetic substance preferably has a volume resistance of 1 × 10 ^{7 to} 1 × 10 ⁹ Ω · cm measured in an environment of 23 ° C. and 50% RH. In general, when a different kind of metal is contained, the volume resistance of the magnetic material tends to decrease, but it is preferable that the toner has a relatively high volume resistance in the above range from the viewpoint of firmly holding the charge.

  In order to adjust the volume resistance of the magnetic material as described above, it is possible to adjust the content of different metals such as Al and the coating amount, and also by adjusting the coating layer of different metals. Is possible. In particular, a Group 2 metal (Mg, Ca, Sr, Ba) is preferably used, and Mg is more preferably used. By using a dissimilar metal such as Mg, the final Al coating layer can be formed more densely.

  The magnetic body is preferably a magnetic body mainly composed of spherical particles formed of a curved surface having no plate-like surface and containing almost no octahedral particles.

  In addition, the magnetic material preferably has a number average particle diameter (D1) of 0.08 to 0.25 μm from the viewpoints of dispersibility of the magnetic material in the binder resin, blackness, magnetic properties, and the like.

  The number average particle diameter of the magnetic material is measured by the following method. Using a transmission electron micrograph (magnification: 30,000 times) of a magnetic material, randomly select 100 particles on the photograph, measure the maximum length of each particle, and calculate the number average particle diameter with the arithmetic average value. To do.

The magnetic material has a magnetic property under a magnetic field of 795.8 kA / m (10 k Oersted), σ _10k is 10 to 200 Am ² / kg, remanent magnetization σr is 1 to 100 Am ² / kg, and coercive force Hc is 1 to 30 kA / m. Are preferably used. More preferably, σ _10k is 70 to 90 Am ² / kg; residual magnetization σr is ² to 20 Am ² / kg; and coercive force Hc is 2 to 15 kA / m. By having such magnetic characteristics, good developability as a magnetic toner can be obtained. The magnetic properties of the magnetic material are measured under an external magnetic field of 795.8 kA / m using a “vibrating sample magnetometer VSM-3S-15” (manufactured by Toei Kogyo Co., Ltd.).

  Hereinafter, specific materials used for the magnetic material and the manufacturing method thereof will be described. In the following description, in a magnetic body having a coating layer, a portion inside the coating layer is called a base magnetic body, and a base body coated with a base layer is called a magnetic body.

  As the magnetic material, any of magnetic iron oxides such as magnetite, maghemite, ferrite and the like containing different elements and mixtures thereof can be used. Preferably, the main component is magnetite having a high FeO content. Magnetite particles are generally obtained by oxidizing a ferrous hydroxide slurry obtained by neutralizing and mixing a ferrous salt aqueous solution and an alkaline solution.

  Further, as one method for obtaining a magnetic material having a dielectric breakdown voltage as defined in the present invention, there is a method of controlling the presence state of Al in the magnetic material. For example, in the manufacturing process of the base magnetic body, there is a method in which a large amount of Al is present on the surface of the base magnetic body and a coating layer containing Al is provided thereon. By containing a large amount of Al on the surface of the base magnetic body, the adhesion between the surface of the base magnetic body and the coating layer can be improved, and a dense coating layer can be formed.

  Specifically, an Al component equivalent to 4000 to 6000 ppm relative to the iron component and an alkali such as sodium hydroxide or potassium hydroxide equivalent to or greater than the iron component are added to the ferrous sulfate aqueous solution, Prepare ferrous solution. At this time, it is preferable to add a predetermined amount of one or more metal salts selected from Group 2 metal elements (Mg, Ca, Sr, Ba). While maintaining the pH of the prepared ferrous hydroxide aqueous solution at 7 or higher (preferably pH 8 to 10 or pH 11 or higher when adding a Group 2 metal element), air was blown into the aqueous solution and heated to 70 ° C. or higher. Then, an oxidation reaction is performed to generate base magnetic particles that become the core of the magnetic particles.

  Next, an Al component equivalent to 4000 to 6000 ppm is added to the slurry-like liquid containing the base magnetic material, and the mixture is stirred at 75 to 85 ° C. and adjusted to a pH of 11 or more, and then a Group 2 metal element (Mg, An aqueous solution containing at least one metal salt selected from Ca, Sr, Ba) containing a Group 2 metal element in an amount of 100 to 2000 ppm based on the entire magnetic material is added and mixed for at least 10 minutes. Thereafter, an acidic aqueous solution is added, and the pH is once adjusted to 8 to 10 and stirred for 5 minutes or more. The acidic aqueous solution is added again to gradually lower the pH, and finally the pH is 6.5 to 7.5. To. Then, the slurry is washed, filtered, and dried to obtain magnetic particles. Furthermore, in order to adjust the average particle diameter, smoothness, and specific surface area to a preferable range, the mixture may be compacted, sheared and spatulated using a mix muller or a rake.

  Examples of the Al component used for introducing Al into the magnetic material include aluminum sulfate, sodium aluminate, aluminum chloride, and aluminum nitrate.

  In addition, as ferrous salts, iron sulfate by-produced in the production of general sulfuric acid method titanium and iron sulfate by-produced by cleaning the surface of the steel sheet can be used, and iron chloride is also used. it can.

  Moreover, it is preferable that a magnetic body has few total content of P, S, Cr, Mn, Co, Ni, Cu, and Zn. These elements are often contained as inevitable components derived from raw materials during the production of magnetic iron oxide, but considering the blackness and magnetic properties, the total content of the above components is preferably low, and it is 1% by mass or less. Preferably there is.

  Further, in the magnetic toner, the magnetic material is preferably contained in an amount of 50 to 150 parts by mass, more preferably 60 to 120 parts by mass with respect to 100 parts by mass of the binder resin. When the content of the magnetic substance is within the above range, the occurrence of fogging and scattering can be suppressed, and sufficient coloring power can be obtained. Further, the flying from the toner carrier can be performed without any problem.

Further, the magnetic toner of the present invention has a dielectric loss tangent (loss rate of dielectric loss: tan δ) measured at a frequency of 100 kHz and 40 ° C. of 2.0 × 10 ^{−3 to} 1.0 × 10 ⁻² . The value of dielectric loss tangent in the magnetic toner can be used as an indicator of the dispersion state of the magnetic material. The dispersion state of the magnetic substance affects the charge retention ability of the toner, and can be considered as an index of the toner charge retention ability. In the magnetic toner, when the dielectric loss tangent is in the above range, the dispersion state of the magnetic material is in an appropriate state, and the balance between charge holding and discharge is in a suitable state.

  The dispersion state of the magnetic material in the toner can be controlled by adjusting the melt-kneading conditions such as temperature and mixing state, the amount of magnetic material added, and the particle size and particle size distribution of the magnetic material. It can also be controlled by performing a mechanical treatment after the synthesis of the magnetic material to suppress the magnetic cohesiveness or to modify the surface of the magnetic material.

The dielectric loss tangent of the magnetic toner is measured by the following method.
A dielectric constant is measured using a 4284A precision LCR meter (manufactured by Hewlett-Packard Company) calibrated at frequencies of 1 kHz and 1 MHz, and a dielectric loss tangent is calculated from the measured value.

Specifically, 1 g of magnetic toner is weighed, and a disk-shaped measurement having a diameter of 25 mm and a thickness of 1 mm or less (preferably 0.5 to 0.9 mm) is performed over a period of 2 minutes under a load of 19600 kPa (200 kg / cm ² ). Mold into a sample. This measurement sample is attached to ARES (manufactured by Rheometric Scientific F.E.) equipped with a dielectric constant measurement jig (electrode) having a diameter of 25 mm, and fixed by heating. At this time, fixing is performed at a temperature as low as possible so that the dispersion state of the magnetic substance in the toner does not change. In the examples described later, the temperature was fixed at 80 ° C. Then, it is cooled to a temperature of 40 ° C., and a frequency range of 500 to ⁵ × 10 ⁵ Hz is measured using a 4284A Precision LCR meter (manufactured by Hewlett-Packard Company) with a load of 1.47 N (150 g) applied. As a result, the dielectric constant of the toner at 100 kHz is measured.

  Here, the reason why the frequency is set to 100 kHz as a reference for measuring the dielectric loss tangent (tan δ) is that the frequency is suitable for verifying the dispersion state of the magnetic substance.

The magnetic toner of the present invention contains at least a binder resin in addition to the magnetic material. As the binder resin, various resin compounds conventionally known as binder resins can be used. For example, vinyl resin, phenol resin, natural resin modified phenolic resin, natural resin modified maleic acid resin, acrylic resin, methacrylic resin, polyvinyl acetate, silicone resin, polyester resin, polyurethane, polyamide resin, furan resin, epoxy resin, xylene Examples thereof include resins, polyvinyl butyral, terpene resins, coumaroindene resins, and petroleum resins.
In particular, the binder resin is preferably a resin having at least a polyester unit. The resin having a polyester unit is a polyester resin itself or a hybrid resin in which a polyester resin and a vinyl resin are chemically bonded.

  Since the resin having a polyester unit obtained from an acid component and an alcohol component has many ester bonds, when a magnetic material containing Al is used, the affinity for Al on the surface of the magnetic material is high. Thus, the mixing with the magnetic material is excellent, and the magnetic material is less likely to be detached.

  Moreover, in the polyester unit part of resin which has a polyester unit, it is preferable that 45-55 mol% is an alcohol component and 55-45 mol% is an acid component in all the components.

（式中、Ｒはエチレン又はプロピレン基を示し、ｘ及びｙはそれぞれ１以上の整数であり、且つｘ＋ｙの平均値は２〜１０である。）

Examples of alcohol components include ethylene glycol, propylene glycol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, diethylene glycol, triethylene glycol, 1,5-pentanediol, and 1,6- Xanthdiol, neopentyl glycol, 2-ethyl-1,3-hexanediol, hydrogenated bisphenol A, bisphenol derivatives represented by the following formula (B), diols represented by the following formula (C), glycerin, sorbit And polyhydric alcohols such as sorbitan.

(In the formula, R represents an ethylene or propylene group, x and y are each an integer of 1 or more, and the average value of x + y is 2 to 10.)

（式中、Ｒはエチレン基又はプロピレン基であり、ｘは０以上の整数であり、ｙ１〜ｙ３は０以上の同一又は異なった整数であり、ｘが２以上であるとき、それぞれのｙ２は同じ値でも良いし異なる値でも良い。） Examples of the trihydric or higher polyhydric alcohol component include sorbitol, 1,2,3,6-hexanetetrol, 1,4-sorbitan, pentaerythritol, dipentaerythritol, tripentaerythritol, 1,2,4. -Butanetriol, 1,2,5-pentanetriol, glycerol, 2-methylpropanetriol, 2-methyl-1,2,4-butanetriol, trimethylolethane, trimethylolpropane, 1,3,5-trihydroxy Benzene is mentioned. A particularly preferable trihydric or higher polyhydric alcohol component is an oxyalkylene ether of a novolac type phenol resin represented by the following formula (D).

(In the formula, R is an ethylene group or a propylene group, x is an integer of 0 or more, y1 to y3 are 0 or more of the same or different integers, and when x is 2 or more, each y2 is (It can be the same value or different values.)

  Moreover, a carboxylic acid can preferably be illustrated as an acid component. Divalent carboxylic acids include benzene dicarboxylic acids such as phthalic acid, terephthalic acid, isophthalic acid, and phthalic anhydride, or anhydrides thereof; alkyldicarboxylic acids such as succinic acid, adipic acid, sebacic acid, and azelaic acid, or anhydrides thereof. ; Unsaturated dicarboxylic acids such as fumaric acid, maleic acid, citraconic acid, itaconic acid or anhydrides thereof; and trivalent or higher carboxylic acids such as trimellitic acid, pyromellitic acid, benzophenone tetracarboxylic acid, The anhydride etc. are mentioned.

  A particularly preferred alcohol component of the polyester unit is a bisphenol derivative represented by the above formula (B), and examples of the acid component include phthalic acid, terephthalic acid, isophthalic acid or its anhydride, succinic acid, n-dodecenyl succinic acid, or the like. Examples thereof include dicarboxylic acids such as anhydride, fumaric acid, maleic acid, and maleic anhydride; trimellitic acid or tricarboxylic acid of anhydride thereof. A magnetic toner using a resin having a polyester unit obtained from these acid components and alcohol components as a binder resin has good dispersion of the magnetic material, excellent developability, good fixability, and offset resistance. Excellent.

  As described above, the binder resin may be a hybrid resin in which a polyester unit and a vinyl resin unit are chemically bonded. As a resin constituting the vinyl resin unit at that time, the following resin may be used. Such vinyl resin can be used. The following vinyl resins may be used alone, or may be blended with other resins.

  Examples of vinyl resins include styrene; o-methylstyrene, m-methylstyrene, p-methylenestyrene, p-methoxystyrene, p-phenylstyrene, p-chlorostyrene, 3,4-dichlorostyrene, p-ethyl. Styrene, 2,4-dimethylstyrene, pn-butylstyrene, p-tert-butylstyrene, pn-hexylstyrene, pn-octylstyrene, pn-nonylstyrene, pn-decylstyrene , Styrene derivatives such as pn-dodecylstyrene; ethylene unsaturated monoolefins such as ethylene, propylene, butylene and isobutylene; unsaturated polyenes such as butadiene; vinyl chloride, vinylidene chloride, vinyl bromide, vinyl fluoride, etc. Of vinyl halides; vinyl acetate, vinyl propionate, benzo Vinyl esters such as vinyl acid; methyl methacrylate, ethyl methacrylate, propyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, n-octyl methacrylate, dodecyl methacrylate, 2-ethylhexyl methacrylate, stearyl methacrylate, Α-methylene aliphatic monocarboxylic acid esters such as phenyl methacrylate, dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate; methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, propyl acrylate, acrylic Acrylic acid esters such as n-octyl acid, dodecyl acrylate, 2-ethylhexyl acrylate, stearyl acrylate, 2-chloroethyl acrylate, phenyl acrylate; vinylmethyl Vinyl ethers such as ether, vinyl ethyl ether and vinyl isobutyl ether; Vinyl ketones such as vinyl methyl ketone, vinyl hexyl ketone and methyl isopropenyl ketone; N-vinyl pyrrole, N-vinyl carbazole, N-vinyl indole, N-vinyl pyrrolidone N-vinyl compounds such as; vinyl naphthalenes; acrylic acid or methacrylic acid derivatives such as acrylonitrile, methacrylonitrile, acrylamide; esters of α, β-unsaturated acids, diesters of dibasic acids; acrylic acid, methacrylic acid, Acrylic acid such as α-ethylacrylic acid, crotonic acid, cinnamic acid, vinyl acetic acid, isocrotonic acid, angelic acid and α- or β-alkyl derivatives thereof; fumaric acid, maleic acid, citraconic acid, alkenyl succinic acid, itaconic acid And polymers using vinyl monomers such as unsaturated dicarboxylic acids such as mesaconic acid, dimethylmaleic acid and dimethylfumaric acid, and monoester derivatives or anhydrides thereof. In the vinyl resin, vinyl monomers as described above are used alone or in combination of two or more. Among these, a combination of monomers that becomes a styrene copolymer or a styrene-acrylic copolymer is preferable.

  The method for synthesizing a binder resin composed of a vinyl-based homopolymer or copolymer is not particularly limited, and various conventionally known production methods can be used. For example, a bulk polymerization method, a solution polymerization method, Polymerization methods such as suspension polymerization and emulsion polymerization can be used. When a carboxylic acid monomer or an acid anhydride monomer is used, it is preferable to use a bulk polymerization method or a solution polymerization method because of the properties of the monomer.

  In addition, the binder resin used in the present invention may be a polymer or copolymer cross-linked with a cross-linkable monomer as exemplified below if necessary. As the crosslinkable monomer, a monomer having at least two crosslinkable unsaturated bonds can be used.

  Examples of the crosslinkable monomer include divinylbenzene and divinylnaphthalene as aromatic divinyl compounds; diacrylate compounds linked with an alkyl chain such as ethylene glycol diacrylate, 1,3-butylene glycol diacrylate, 1 , 4-butanediol diacrylate, 1,5-pentanediol diacrylate, 1,6-hexanediol diacrylate, neopentyl glycol diacrylate, and those obtained by replacing acrylates of the above compounds with methacrylates; Examples of diacrylate compounds linked with an alkyl chain include diethylene glycol diacrylate, triethylene glycol diacrylate, tetraethylene glycol diacrylate, and polyethylene glycol. Coal # 400 diacrylate, polyethylene glycol # 600 diacrylate, dipropylene glycol diacrylate and the above compounds in which the acrylate is replaced with methacrylate; diacrylate compounds linked by a chain containing an aromatic group and an ether bond For example, polyoxyethylene (2) -2,2-bis (4-hydroxyphenyl) propane diacrylate, polyoxyethylene (4) -2,2-bis (4-hydroxyphenyl) propane diacrylate and the above The thing which replaced the acrylate of the compound with the methacrylate is mentioned; As a polyester type diacrylate, a brand name MANDA (Nippon Kayaku) etc. are mentioned, for example.

  Polyfunctional cross-linking agents include pentaerythritol triacrylate, trimethylol ethane triacrylate, trimethylol propane triacrylate, tetramethylol methane tetraacrylate, oligoester acrylate, and acrylates of the above compounds replaced with methacrylate; triallylcia Examples thereof include nurate and triallyl trimellitate.

  Among the above crosslinkable monomers, aromatic divinyl compounds (especially divinylbenzene), aromatic groups and ether bonds are used as binder resins that are suitable from the viewpoint of the fixability and offset resistance of the obtained magnetic toner. Examples include diacrylate compounds linked by a chain.

  The amount of the crosslinking agent is preferably adjusted according to the type of monomer and the physical properties required of the binder resin, but generally 0.01 to 100 parts by mass with respect to 100 parts by mass of other monomer components constituting the binder resin. 10 parts by mass (more preferably 0.03 to 5 parts by mass) can be used.

  In addition, homopolymers or copolymers of vinyl monomers other than those described above, polyester, polyurethane, epoxy resin, polyvinyl butyral, rosin, modified rosin, terpene resin, phenol resin, aliphatic or alicyclic hydrocarbon resin, aromatic A petroleum-based petroleum resin or the like can be mixed with the above-described binder resin as necessary. When two or more kinds of resins are mixed and used as the binder resin, it is more preferable to mix those having different molecular weights at an appropriate ratio.

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

  The glass transition temperature of the binder resin is generally described in the publication Polymer Handbook 2nd edition III-P. 139 to 192 (manufactured by John Wiley & Sons) can be adjusted by selecting the constituent material (polymerizable monomer) of the binder resin so that the theoretical glass transition temperature is 45 to 80 ° C. it can. The glass transition temperature of the binder resin can be measured according to ASTM D3418-82 using a differential scanning calorimeter, for example, DSC-7 manufactured by PerkinElmer or DSC2920 manufactured by TA Instruments Japan. If the glass transition temperature of the binder resin is within the above range, both storage stability and fixability can be satisfactorily achieved.

  The magnetic toner may further contain a wax.

  Examples of the wax include the following. For example, low molecular weight polyethylene, low molecular weight polypropylene, polyolefin copolymer, polyolefin wax, microcrystalline wax, paraffin wax, Fischer-Tropsch wax and other aliphatic hydrocarbon waxes; oxides of aliphatic hydrocarbon waxes such as oxidized polyethylene wax Or block copolymers thereof; plant waxes such as candelilla wax, carnauba wax, wood wax, jojoba wax; animal waxes such as beeswax, lanolin, whale wax; mineral systems such as ozokerite, ceresin, petrolactam, etc. Waxes; waxes mainly composed of aliphatic esters such as montanic acid ester wax and caster wax; those obtained by partially or entirely deoxidizing aliphatic esters such as deoxidized carnauba wax . Further, saturated linear fatty acids such as palmitic acid, stearic acid, montanic acid, or long-chain alkyl carboxylic acids having a long-chain alkyl group; unsaturated fatty acids such as brassic acid, eleostearic acid, and valinalic acid; stearyl alcohol Saturated alcohols such as eicosyl alcohol, behenyl alcohol, kaunavir alcohol, seryl alcohol, melyl alcohol, or alkyl alcohol having a long chain alkyl group; polyhydric alcohols such as sorbitol; linoleic acid amide, oleic acid amide, lauric acid Aliphatic amides such as acid amides; saturated aliphatic bisamides such as methylene bisstearic acid amide, ethylene biscapric acid amide, ethylene bislauric acid amide, hexamethylene bisstearic acid amide; Unsaturated fatty acid amides such as acid amide, hexamethylenebisoleic acid amide, N, N′-dioleyl adipic acid amide, N, N′-dioleyl sebacic acid amide; m-xylene bisstearic acid amide, N, N Aromatic bisamides such as' -distearylisophthalic acid amide; Aliphatic metal salts such as calcium stearate, calcium laurate, zinc stearate, magnesium stearate (generally called metal soap); Aliphatic hydrocarbon wax Wax grafted with vinyl monomers such as styrene and acrylic acid; partially esterified products of fatty acid and polyhydric alcohol such as behenic acid monoglyceride; methyl having hydroxyl group obtained by hydrogenating vegetable oil Ester compounds That.

  In addition, these waxes have a sharp molecular weight distribution using a press perspiration method, a solvent method, a recrystallization method, a vacuum distillation method, a supercritical gas extraction method or a melt liquid crystal deposition method, a low molecular weight solid fatty acid, a low A molecular weight solid alcohol, a low molecular weight solid compound, or other impurities are preferably used.

  The wax has a melting point of 60 to 120 ° C, more preferably 70 to 110 ° C. By using a wax having a melting point in the above range, the dispersibility of the magnetic substance in the binder resin can be improved.

［式中、Ｍは配位中心金属を表し、Ｃｒ，Ｃｏ，Ｎｉ，Ｍｎ，Ｆｅ，Ｔｉ又はＡｌを示す。Ａｒは、フェニル基，ナフチル基などのアリール基であり、置換基を有してもよい。この場合の置換基としては、ニトロ基，ハロゲン基，カルボキシル基，アニリド基及び炭素数１〜１８のアルキル基，炭素数１〜１８のアルコキシ基がある。Ｘ，Ｘ’，Ｙ，Ｙ’は−Ｏ−，−ＣＯ−，−ＮＨ−，−ＮＲ−（Ｒは炭素数１〜４のアルキル基）である。Ａ^＋は水素イオン，ナトリウムイオン，カリウムイオン，アンモニウムイオン又は脂肪族アンモニウムイオン、或いはそれらの混合イオンを示す。］

〔式中、Ｍは配位中心金属を表し、Ｃｒ，Ｃｏ，Ｎｉ，Ｍｎ，Ｆｅ，Ｔｉ，Ｚｒ，Ｚｎ，Ｓｉ，Ｂ又はＡｌを示す。
（Ｂ）は、アルキル基、ハロゲン原子、ニトロ基を置換基として有していても良い芳香族系化合物であり、例えば、フェニレン、ナフチレンを表す。
Ａ'^＋は、水素イオン、ナトリウムイオン、カリウムイオン、アンモニウムイオン、脂肪族アンモニウムイオン、或いは、それらの混合イオンを示す。
Ｚは、−Ｏ−、或いは、−ＣＯＯ−を示す。〕 Further, it is preferable to add a charge control agent to the toner, and various known charge control agents can be used. Examples of the negative charge control agent include monoazo compounds described in, for example, Japanese Patent Publication No. 41-20153, Japanese Patent Publication No. 42-27596, Japanese Patent Publication No. 44-6397, Japanese Patent Publication No. 45-26478, and the like. Nitrohumic acid and its salts described in JP-A-50-133838 or C.I. I. Dyes and pigments such as 14645; salicylic acid, naphthoic acid, dicarboxylic acid described in JP-B-55-42752, JP-B-58-41508, JP-B-58-7384, JP-B-59-7385, etc. Metal complexes of acids such as Zn, Al, Co, Cr, Fe, Zr; sulfonated copper phthalocyanine pigments; styrene oligomers introduced with nitro groups and halogens; chlorinated paraffins and the like. In particular, an azo metal complex represented by the following general formula (I) or the following general formula (II), which is excellent in dispersibility in a magnetic toner and is effective in reducing image density stability and fogging. Basic organic acid metal complexes are preferred.

[Wherein M represents a coordination center metal and represents Cr, Co, Ni, Mn, Fe, Ti, or Al. Ar is an aryl group such as a phenyl group or a naphthyl group, and may have a substituent. In this case, examples of the substituent include a nitro group, a halogen group, a carboxyl group, an anilide group, an alkyl group having 1 to 18 carbon atoms, and an alkoxy group having 1 to 18 carbon atoms. X, X ′, Y, Y ′ are —O—, —CO—, —NH—, —NR— (R is an alkyl group having 1 to 4 carbon atoms). A ⁺ represents a hydrogen ion, a sodium ion, a potassium ion, an ammonium ion, an aliphatic ammonium ion, or a mixed ion thereof. ]

[Wherein, M represents a coordination center metal, and represents Cr, Co, Ni, Mn, Fe, Ti, Zr, Zn, Si, B, or Al.
(B) is an aromatic compound which may have an alkyl group, a halogen atom or a nitro group as a substituent, and represents, for example, phenylene or naphthylene.
A ′ ⁺ represents a hydrogen ion, a sodium ion, a potassium ion, an ammonium ion, an aliphatic ammonium ion, or a mixed ion thereof.
Z represents —O— or —COO—. ]

  Among these, the azo metal complex represented by the above formula (I) is more preferable, and the azo iron complex whose central metal is Fe is most preferable.

  These charge control agents can be used alone or in combination of two or more. The amount of these charge control agents used is preferably 0.1 to 5.0 parts by mass per 100 parts by mass of the binder resin from the viewpoint of the charge amount of the magnetic toner.

  Among the negative charge control agents as described above, commercially available products include, for example, SPILON BLACK TRH, T-77, T-95 (Hodogaya Chemical Co., Ltd.), BONTRON (registered trademark) S-34, S-44, S-54, E-84, E-88, E-89 (Orient Chemical Co., Ltd.) and the like.

  On the other hand, the following substances can be cited as examples of controlling the toner to be positively charged. Modified products with nigrosine and fatty acid metal salts; oniums such as quaternary ammonium salts such as tributylbenzylammonium-1-hydroxy-4-naphthosulfonate, tetrabutylammonium tetrafluoroborate, and phosphonium salts which are analogs thereof Salts and their lake pigments; triphenylmethane dyes and their lake pigments (the rake agents include phosphotungstic acid, phosphomolybdic acid, phosphotungsten molybdic acid, tannic acid, lauric acid, gallic acid, ferricyanide, Russian salts, etc.); metal salts of higher fatty acids; diorganotin oxides such as dibutyltin oxide, dioctyltin oxide, dicyclohexyltin oxide; dibutyltin borate, dioctyltin borate, dicyclohexyl Diorgano tin borate such as Suzuboreto; they can be used alone or in combinations of two or more.

  Among the positive charge control agents as described above, preferred as commercially available products are, for example, TP-302, TP-415 (Hodogaya Chemical Co., Ltd.), BONTRON (registered trademark) N-01, N-04, N-07, P-51 (Orient Chemical Co., Ltd.), Copy Blue PR (Clariant Inc.) and the like.

  Further, an inorganic fine powder is preferably externally added as an external additive to the surface of the toner base particles, and the inorganic fine powder is preferably used after being hydrophobized. For example, silica fine powder can be used as the inorganic fine powder.

  As the silica fine powder, both a so-called dry process produced by vapor phase oxidation of a silicon halogen compound or dry silica called fumed silica, and so-called wet silica produced from water glass or the like can be used. Among them, dry silica is preferable because it has few silanol groups on the surface and inside and no production residue.

  In addition, when hydrophobizing silica fine powder, the method of hydrophobizing treatment includes treating the silica fine powder with an organosilicon compound that reacts with the silica fine powder or is physically adsorbed on the silica fine powder. The method of doing is mentioned. Preferable methods include a method in which a dry silica fine powder produced by vapor phase oxidation of a silicon halogen compound is treated with a silane compound or with a silane compound and simultaneously with an organosilicon compound such as silicone oil.

  Examples of the silane compound used for the hydrophobizing treatment include hexamethyldisilazane, trimethylsilane, trimethylchlorosilane, trimethylethoxysilane, dimethyldichlorosilane, methyltrichlorosilane, allyldimethylchlorosilane, allylphenyldichlorosilane, and benzyl. Dimethylchlorosilane, bromomethyldimethylchlorosilane, α-chloroethyltrichlorosilane, β-chloroethyltrichlorosilane, chloromethyldimethylchlorosilane, triorganosilane mercaptan, trimethylsilyl mercaptan, triorganosilyl acrylate, vinyldimethylacetoxysilane, dimethylethoxy Silane, dimethyldimethoxysilane, diphenyldiethoxysilane, hexamethyldisiloxane, 1,3-divinyltetramethyl Examples include tildisiloxane and 1,3-diphenyltetramethyldisiloxane.

Examples of the organosilicon compound include silicone oil. Preferred silicone oils are those having a viscosity at 25 ° C. of about 3 × 10 ⁻⁵ to 1 × 10 ⁻³ m ² / s, such as dimethyl silicone oil, methyl hydrogen silicone oil, methyl phenyl silicone oil, α -Methylstyrene modified silicone oil, chlorophenyl silicone oil, fluorine modified silicone oil and the like are preferable.

  The inorganic fine powder is preferably used in an amount of 0.1 to 5 parts by mass (more preferably 0.1 to 3 parts by mass) with respect to 100 parts by mass of the magnetic toner base particles.

  If necessary, an external additive other than silica fine powder may be added to the toner. For example, resin fine particles and inorganic fine particles that function as a charge auxiliary agent, conductivity imparting agent, fluidity imparting agent, anti-caking agent, lubricant, abrasive, and the like. Specific examples include lubricants such as polyvinyl fluoride, zinc stearate, and polyvinylidene fluoride. Among these, polyvinylidene fluoride is preferable. Or abrasive | polishing agents, such as a cerium oxide, silicon carbide, and strontium titanate, are mentioned, Among these, strontium titanate is preferable. Alternatively, fluidity imparting agents such as titanium oxide and aluminum oxide can be used, and among them, hydrophobic ones are particularly preferable. In addition, an anti-caking agent; for example, a conductivity imparting agent such as carbon black, zinc oxide, antimony oxide, tin oxide; and a small amount of white and black fine particles having opposite polarity can be used as a developing improver.

  The toner preferably has a weight average particle diameter (D4) of 4.0 to 9.0 μm, and more preferably 5.0 to 8.0 μm. When the weight average particle diameter is in the above range, both good developability and fine line reproducibility can be achieved.

  The weight average particle diameter of the toner is measured using a Coulter Counter TA-II type or Coulter Multisizer (manufactured by Beckman Coulter). As the electrolytic solution, a 1% NaCl aqueous solution is prepared using first grade sodium chloride. For example, ISOTON R-II (manufactured by Beckman Coulter) can be used. As a measurement method, 0.1 to 5 ml of a surfactant as a dispersant is added to 100 to 150 ml of the electrolytic aqueous solution, and 2 to 20 mg of a measurement sample is further added. The electrolytic solution in which the sample is suspended is subjected to a dispersion treatment with an ultrasonic disperser for about 1 to 3 minutes, and the measurement device is used to measure the volume and number of toners of 2 μm or more using a 100 μm aperture as the aperture. The distribution and the number distribution were calculated, and the weight average particle diameter (D4) was determined from them.

  The method for producing the magnetic toner of the present invention is not particularly limited, but it is preferably produced by a pulverization method. Binder resin and magnetic material, and if necessary, mix materials such as wax sufficiently with a mixer such as a Henschel mixer or a ball mill, and then melt and knead them using a thermal kneader such as a roll, kneader or extruder. The magnetic substance is dispersed in the resins that are compatible with each other. Then, after solidifying by cooling, pulverization and classification can be performed to obtain magnetic toner base particles. Then, if necessary, silica fine powder and / or other external additives are externally mixed with the obtained magnetic toner base particles.

  In the kneading process, the magnetic material is oxidized due to the increase in the kneading temperature, which may cause the color of the magnetic toner to become reddish. However, a magnetic material whose surface is densely coated with Al is used. If this occurs, this phenomenon can be suppressed. Also, by using a wax having a lower melting point, the kneading temperature can be lowered, the oxidation of the magnetic particles can be suppressed, and the redness of the magnetic toner can be suppressed.

  Examples of the mixer used in the production of the magnetic toner include Henschel mixer (manufactured by Mitsui Mining); Super mixer (manufactured by Kawata); Ribocorn (manufactured by Okawara Seisakusho); Nauter mixer, turbulizer, cyclomix (Hosokawa Micron) Spiral pin mixer (manufactured by Taiheiyo Kiko Co., Ltd.); Ladige mixer (manufactured by Matsubo Co., Ltd.), and KRC kneader (manufactured by Kurimoto Iron Works Co.); TEM type extruder (manufactured by Toshiba Machine Co., Ltd.); TEX twin-screw kneader (manufactured by Nippon Steel Works); PCM kneader (manufactured by Ikegai Iron Works Co., Ltd.); triple roll mill, mixing roll mill, kneader (Inoue Manufacturing Co., Ltd.) ); Kneedex (Mitsui Mining Co., Ltd.); MS pressure kneader, Nider Ruder (Moriyama Seisakusho); Banbury Kiser (manufactured by Kobe Steel Co., Ltd.) can be mentioned, and as the pulverizer, counter jet mill, micron jet, inomizer (manufactured by Hosokawa Micron); IDS type mill, PJM jet pulverizer (manufactured by Nippon Pneumatic Industrial Co., Ltd.); cross jet Mill (manufactured by Kurimoto Iron Works); Urmax (manufactured by Nisso Engineering); SK Jet O Mill (manufactured by Seishin Enterprise); Kryptron (manufactured by Kawasaki Heavy Industries); Turbo mill (manufactured by Turbo Industry); Super Rotor (Nisshin Engineering) is listed, and classifiers include: Classy, Micron Classifier, Spedic Classifier (manufactured by Seishin Enterprise); Turbo Classifier (manufactured by Nisshin Engineering); Micron Separator, Turboplex ( ATP), TSP separator Hosokawa Micron Co., Ltd.); Elbow Jet (Nittetsu Mining Co., Ltd.), Dispersion Separator (Nihon Pneumatic Kogyo Co., Ltd.); YM Micro Cut (Yaskawa Shoji Co., Ltd.), and the like are used to screen coarse particles. As the sieving device, Ultrasonic (manufactured by Sakae Sangyo Co., Ltd.); Resonant Sheave, Gyroshifter (manufactured by Deoksugakusho Co., Ltd.); Vibrasonic System (manufactured by Dalton Co., Ltd.); A turbo shifter); a micro shifter (manufactured by Hadano Sangyo Co., Ltd.); and a circular vibrating sieve.

  Hereinafter, the present invention will be described based on examples. However, this does not limit the present invention. In addition, the number of parts in an Example is a mass part.

≪Example 1 of manufacturing magnetic material≫
Aluminum sulfate is added to the aqueous ferrous sulfate solution so that the Al content in the magnetic material is 0.60% by mass, and the magnesium hydroxide is adjusted so that the Mg content in the magnetic material is 500 ppm. Was added. Thereafter, an aqueous solution of sodium hydroxide is mixed to prepare an aqueous solution containing ferrous hydroxide. Air was blown in while adjusting the pH of the aqueous solution to 11 or more, and an oxidation reaction was performed at 90 ° C. to obtain a slurry containing the base magnetic material.

  Next, aluminum sulfate is added to the slurry containing the base magnetic body so that the amount of Al contained in the coating layer is 0.50 mass% (based on the magnetic body), and the mixture is stirred at 80 ° C. to adjust the pH to 11 Adjusted to above. Thereafter, magnesium hydroxide was added so that the amount of Mg contained in the coating layer was 900 ppm (based on the magnetic material), and the mixture was stirred for at least 15 minutes. Thereafter, an aqueous sulfuric acid solution was added to adjust the pH to 8 to 10 and stirred for 5 minutes. The aqueous sulfuric acid solution was added again to gradually lower the pH, and finally to pH 7.1. This slurry was washed, filtered, and dried to obtain a magnetic body 1 in which a coating layer made of Al and Mg was formed on the surface of a base magnetic body containing Al and Mg. The obtained magnetic body 1 was composed of magnetic iron oxide having a number average particle diameter (D1) of 0.16 μm, containing Al and Mg, and having a crystal structure of magnetite. Table 1 shows the physical properties of the magnetic body 1.

≪Example 2 of manufacturing magnetic material≫
In Production Example 1 of the magnetic material, the amount of aluminum sulfate and the amount of magnesium hydroxide were adjusted so that the Al content in the parent magnetic material was 1.20% by mass and the Mg content was 100 ppm in the production step of the parent magnetic material. Was changed respectively. Further, in the coating layer forming step, the aluminum sulfate content and the magnesium hydroxide content were changed so that the Al content in the coating layer was 1.50 mass% and the Mg content was 650 ppm. A magnetic body was manufactured under the conditions where these points were changed, and a magnetic body 2 was obtained. The magnetic body 2 was made of magnetic iron oxide having a number average particle diameter (D1) of 0.17 μm, containing Al and Mg, and having a crystal structure of magnetite. Table 1 shows the physical properties of the magnetic body 2.

≪Magnetic substance production example 3≫
In Production Example 1 of the magnetic material, the amount of aluminum sulfate was changed so that the Al content in the parent magnetic material was 1.00% by mass, and magnesium hydroxide was not used in the production step of the parent magnetic material. It was changed as follows. The pH of the aqueous solution was changed to 10.5. Further, in the coating layer forming step, the aluminum sulfate amount and the magnesium hydroxide amount were changed so that the Al content in the coating layer was 1.20% by mass and the Mg content was 150 ppm. A magnetic body was manufactured under the conditions in which these points were changed, and a magnetic body 3 was obtained. The magnetic body 3 was made of magnetic iron oxide having a number average particle diameter (D1) of 0.15 μm, containing Al and Mg, and having a crystal structure of magnetite. Table 1 shows the physical properties of the magnetic body 3.

≪Example 4 of manufacturing magnetic material≫
In Production Example 1 of the magnetic material, the amount of aluminum sulfate was changed so that the Al content in the parent magnetic material was 0.50% by mass, and magnesium hydroxide was not used. It was changed as follows. The pH of the aqueous solution was changed to 10.5. Further, in the coating layer forming step, the aluminum sulfate amount and the magnesium hydroxide amount were changed so that the Al content in the coating layer was 0.40 mass% and the Mg content was 100 ppm. A magnetic body was manufactured under the conditions in which these points were changed, and a magnetic body 4 was obtained. The magnetic body 4 was made of magnetic iron oxide having a number average particle diameter (D1) of 0.20 μm, containing Al and Mg, and having a crystal structure of magnetite. Table 1 shows the physical properties of the magnetic body 4.

≪Example 5 of manufacturing magnetic material≫
In Production Example 1 of the magnetic material, the amount of aluminum sulfate and the amount of magnesium hydroxide were adjusted so that the Al content in the parent magnetic material was 0.20% by mass and the Mg content was 100 ppm at the production stage of the parent magnetic material. Was changed respectively. Furthermore, in the coating layer forming step, the aluminum sulfate content was changed so that the Al content in the coating layer was 0.30% by mass, and further, magnesium hydroxide was not used. A magnetic body was manufactured under the conditions in which these points were changed, and a magnetic body 5 was obtained. The magnetic body 5 was made of magnetic iron oxide having a number average particle diameter (D1) of 0.18 μm, containing Al and Mg, and having a crystal structure of magnetite. Table 1 shows the physical properties of the magnetic body 5.

≪Example 6 of manufacturing magnetic material≫
In Production Example 1 of the magnetic material, the amount of aluminum sulfate was changed so that the Al content in the parent magnetic material was 2.20% by mass, and magnesium hydroxide was not used in the production step of the parent magnetic material. It was changed as follows. In addition, the pH of the aqueous solution was changed to 10.5 to reduce the stirring speed. Furthermore, in the coating layer forming step, the amount of aluminum sulfate was changed so that the Al content in the coating layer was 2.80% by mass, and further, magnesium hydroxide was not used. A magnetic body was manufactured under the conditions where these points were changed, and a magnetic body 6 was obtained. The magnetic body 6 was made of magnetic iron oxide having a number average particle diameter (D1) of 0.30 μm, containing Al, and having a crystal structure of magnetite. Table 1 shows the physical properties of the magnetic body 6.

≪Example 7 of manufacturing magnetic material≫
In Production Example 1 of the magnetic material, the amount of aluminum sulfate was changed so that the Al content in the parent magnetic material was 0.30% by mass in the production step of the parent magnetic material, and magnesium hydroxide was not used. It was changed as follows. The pH of the aqueous solution was changed to 10.5. Furthermore, in the coating layer forming step, the aluminum sulfate content was changed so that the Al content in the coating layer was 0.20% by mass, and further, magnesium hydroxide was not used. A magnetic body was manufactured under the conditions where these points were changed, and a magnetic body 7 was obtained. The magnetic body 7 was made of magnetic iron oxide having a number average particle diameter (D1) of 0.15 μm, containing Al, and having a crystal structure of magnetite. The physical properties of the magnetic body 7 are shown in Table 1.

≪Example 8 of manufacturing magnetic material≫
In Magnetic Material Production Example 1, magnetic material 8 was obtained without adding Al or Mg. However, the pH was adjusted to obtain magnetic iron oxide having an octahedral shape. Table 1 shows the physical properties of the magnetic body 8.

≪Example 9 of manufacturing magnetic material≫
In Production Example 1 of the magnetic material, the amount of aluminum sulfate was changed so that the Al content in the parent magnetic material was 2.00% by mass, and magnesium hydroxide was not used in the production step of the parent magnetic material. It was changed as follows. In addition, the pH of the aqueous solution was changed to 10.5 to reduce the stirring speed. Furthermore, in the coating layer forming step, the aluminum sulfate content was changed so that the Al content in the coating layer was 3.30% by mass, and further, magnesium hydroxide was not used. A magnetic body was manufactured under the conditions where these points were changed, and a magnetic body 9 was obtained. The magnetic body 9 was made of magnetic iron oxide having a number average particle diameter (D1) of 0.22 μm, containing Al, and having a crystal structure of magnetite. Table 1 shows the physical properties of the magnetic body 9.

≪Magnetic material production example 10≫
In Production Example 1 of the magnetic material, the amount of aluminum sulfate and the amount of magnesium hydroxide were adjusted so that the Al content in the parent magnetic material was 0.40% by mass and the Mg content was 70 ppm in the production process of the parent magnetic material. Was changed respectively. In addition, the reaction temperature in the oxidation reaction was changed to 80 ° C. Furthermore, in the step of forming the coating layer, the aluminum sulfate amount and the magnesium hydroxide amount were respectively changed and stirred so that the Al content in the coating layer was 0.60% by mass and the Mg content was 50 ppm. The time was changed to 10 minutes. Furthermore, after stirring, it changed so that pH might be dropped to 7.1, without stirring at pH 8-10 for 5 minutes. A magnetic body was manufactured under the conditions in which these points were changed, and a magnetic body 10 was obtained. The magnetic body 10 was made of magnetic iron oxide having a number average particle diameter (D1) of 0.16 μm, containing Al and Mg, and having a crystal structure of magnetite. Table 1 shows the physical properties of the magnetic body 10.

≪Binder resin production example 1≫
(Polyester resin A)
-Bisphenol derivative represented by formula (B): 39 parts (R: propylene group, average value of x + y: 2.2)
-Bisphenol derivative represented by formula (B): 18 parts (R: ethylene group, average value of x + y: 2.2)
-Terephthalic acid: 20 parts-isophthalic acid: 11 parts-fumaric acid: 0.2 parts Thus, a low molecular weight unsaturated polyester resin A (Tg: 59 ° C., peak molecular weight (Mp): 7,800) free from THF-insoluble matter was obtained.

  The obtained low molecular weight unsaturated polyester resin A: 75 parts is heated and dissolved in methyl ethyl ketone: 75 parts, and after cooling, styrene: 19 parts, butyl acrylate: 6 parts, Parkadox 12-XL25 (chemical agent) as a polymerization initiator Manufactured by Akzo): 0.125 part was mixed. The monomer mixed polyester solution was added to 150 parts of a 0.2% by weight aqueous polyvinyl alcohol solution prepared in advance with stirring and dispersed to obtain a suspension.

  The suspension was heated under a nitrogen stream, and the temperature was raised while returning methyl ethyl ketone. The temperature inside the flask was kept at 85 ° C., and polymerization was carried out for 20 hours while distilling off methyl ethyl ketone, followed by cooling. The obtained suspension slurry was dehydrated and dried to obtain a hybrid resin (Tg: 59 ° C., THF insoluble matter 40%, Mp: 7,700, Mn: 3,500, Mw: 26,000, acid value: 18 mgKOH / g , Hydroxyl value: 35 mgKOH / g). This is designated as binder resin 1.

≪Binder resin production example 2≫
(Polyester resin B)
・ Terephthalic acid: 25 parts ・ Trimellitic anhydride: 3 parts ・ Bisphenol derivative represented by formula (B): 72 parts (R: propylene group, x + y average value: 2.2)
Dibutyltin oxide: 0.5 part was added to these as a catalyst and subjected to condensation polymerization at 220 ° C., and low molecular weight polyester resin B (Tg: 55 ° C., THF insoluble content: 0% by mass, Mp: 7,600, Mn: 4,000, Mw: 9,200, acid value: 11 mgKOH / g, hydroxyl value: 35 mgKOH / g).

(Polyester resin C)
-Terephthalic acid: 18 parts-Isophthalic acid: 3 parts-Trimellitic anhydride: 7 parts-Bisphenol derivative represented by the formula (B): 72 parts (R: Propylene group, x + y average value: 2.2)
-An oxyalkylene ether of a novolak-type phenol resin represented by the formula (D)
2 parts (R = ethylene group, average value of x = 2.6, average value of y1 to y3 = 1.0)
0.5 parts by mass of dibutyltin oxide as a catalyst was added to these raw materials and subjected to condensation polymerization at 240 ° C. to form a crosslinked polyester resin C (Tg: 56 ° C., THF-insoluble matter: 39% by mass, Mp: 8,600, Mn: 5,300, Mw: 110,000, acid value: 25 mgKOH / g, hydroxyl value: 21 mgKOH / g).

  Next, 50 parts of the obtained polyester resin B and 50 parts of the polyester resin C are premixed with a Henschel mixer (mixer, manufactured by Mitsui Miike Chemical Co., Ltd.), and then KRC kneader S1 (kneader, manufactured by Kurimoto Ironworks Co., Ltd.). , Kneading is carried out under the condition that the temperature of the discharged resin is 150 ° C., and binder resin 2 (Tg: 56 ° C., THF insoluble matter 22% by mass, Mp: 8,800, Mn: 5,600, Mw: 130,000, acid value: 16 mgKOH / g, hydroxyl value: 27 mgKOH / g).

≪Binder resin production example 3≫
Tg: 58 ° C., peak molecular weight (Mp): 7,800, number average molecular weight (Mn): 5,000, weight average molecular weight (Mw): 9,700, acid value: 21 mgKOH / g, hydroxyl value: 2 mgKOH / g The binder resin 3 was a styrene-acrylic resin (styrene / n-butyl acrylate / maleic anhydride = 50/45/5 on a molar basis).

Example 1
・ Binder resin 1: 100 parts ・ Magnetic material 1: 90 parts ・ Fischer-Tropsch wax (melting point: 108 ° C.): 4 parts ・ Charge control agent T-77 (azo iron compound, Hodogaya Chemical Co., Ltd.): 2 parts The mixture is melt-kneaded with a biaxial extruder heated to 140 ° C., the cooled kneaded product is coarsely pulverized with a hammer mill, the coarsely pulverized product is finely pulverized with a jet mill, and the obtained finely pulverized powder is fixed-wall type The primary classification powder was produced by classification with an air classifier. Furthermore, the obtained primary classified powder is treated with a multi-division classifying device (Elbow Jet Classifier manufactured by Nittetsu Mining Co., Ltd.) using the Coanda effect, so that ultrafine powder and coarse powder are simultaneously strictly classified and removed. Negatively chargeable magnetic toner particles having an average particle diameter (D4) of 5.7 μm were obtained. To 100 parts of the obtained magnetic toner particles, 1.2 parts of hydrophobic silica fine powder having a BET specific surface area of 120 m ² / g subjected to a hydrophobic treatment was externally added and mixed to prepare magnetic toner 1.

  A commercially available LBP printer (HP LaserJet 4250, manufactured by Hewlett Packard) was used as an image output test machine for evaluation of the magnetic toner 1. Specifically, the process speed was modified to 120 mm / sec (20 sheets / min. On the side of A4), and further modified so that the peripheral speeds of the developing sleeve and the electrostatic latent image carrier were the same. Further, among the toner stirring members installed in the cartridge, the stirring member installed at a position away from the developing sleeve was removed. Using this tester, 20,000 print tests were conducted in an environment of 30 ° C. and 80% RH (high temperature and high humidity) and 15 ° C. and 10% RH (low temperature and low humidity). went. The evaluation results are shown in Table 3.

(1) Image Density Under each environment of high temperature and high humidity and low temperature and low humidity, 20,000 sheets were printed on ordinary copying machine plain paper (75 g / m ² ), and the image density at the end was evaluated. The image density is a relative density with respect to a printout image of a white background portion (that is, plain paper for a copier before image formation) having a document density of 0.00 using an SPI filter with a Macbeth densitometer (manufactured by Macbeth). Was measured. The image density of the first printout image was also evaluated after leaving it in a high temperature and high humidity environment for 2 weeks.

(2) Sleeve negative ghost Under a low-temperature and low-humidity environment, 20,000 sheets were printed on ordinary copying machine plain paper (75 g / m ² ), and sleeve negative ghosts were evaluated every 5,000 sheets. In the image evaluation regarding the ghost, a solid black belt-shaped image was output for one round of the sleeve, and then a halftone image was output. Of a printed image, in a portion corresponding to the second turn of the sleeve, a place where a black image is formed in the first turn (solid black print portion) and a place where a black image is not formed in the first turn (non-printing) The difference in reflection density measured with a Macbeth densitometer was calculated using the following formula.
Reflection density difference = reflection density (place where no image is formed) −reflection density (place where an image is formed)

Note that the smaller the reflection density difference, the better the occurrence of ghosts. The obtained reflection density difference was evaluated in the following four stages of A, B, C, and D, and the worst evaluation result among the evaluations for every 5,000 sheets was evaluated.
A: Reflection density difference less than 0.02 B: Reflection density difference between 0.02 and less than 0.04 C: Reflection density difference between 0.04 and less than 0.06 D: Reflection density difference between 0.06 and more

(3) Fog Fog is set to 1.8 kV (default is 1.6 kV) at the end of 10,000 sheets during the endurance test in a low temperature and low humidity environment. Two sheets were printed, and the fog was measured on the second sheet by the following method.

  Using a reflection densitometer (reflectometer model TC-6DS manufactured by Tokyo Denshoku Co., Ltd.), the transfer material before and after the image formation is measured, and the reflection density worst value after the image formation is Ds, and the reflection average density of the transfer material before the image formation. Was taken as Dr, Ds-Dr was determined, and this was evaluated as the amount of fogging. Smaller numbers indicate less fog.

The evaluation standard of fog is shown below.
A: Less than 1.0 B: 1.0 or more and less than 2.0 C: 2.0 or more and less than 3.5 D: 3.5 or more

(4) Scattering Scattering was evaluated using the following criteria, using an original containing lines and letters, and visually or magnifying the image after the durability test in a low-temperature, low-humidity environment.
A: Both character images and line images are faithfully reproduced in detail.
B: Although some disturbance or scattering has occurred in the details, it is a level at which there is no problem with visual observation.
C: It is a level where disturbance and scattering can be seen even visually.
D: Many disturbances and scattering occur, and the original is not reproduced.

Examples 2-6
Magnetic toners 2 to 6 were produced in the same manner as in Example 1 except that the magnetic material, binder resin and wax were changed as shown in Table 2 in the formulation of the magnetic toner.
Further, the same evaluation as in Example 1 was performed using each of the obtained magnetic toners. The evaluation results are shown in Table 3.

Comparative Example 1
Magnetic toner 7 was produced in the same manner as in Example 1 except that the formulation of the magnetic toner was changed as shown in Table 2.
The same evaluation as in Example 1 was performed using the magnetic toner 7. The evaluation results are shown in Table 3.

Comparative Example 2
Magnetic toner 8 was produced in the same manner as in Example 1 except that the formulation of the magnetic toner was changed as shown in Table 2 and the kneading temperature during melt kneading was changed to 100 ° C.
In addition, the same evaluation as in Example 1 was performed using the magnetic toner 8. The evaluation results are shown in Table 3.

Comparative Example 3
Magnetic toner 9 was produced in the same manner as in Example 1 except that the formulation of the magnetic toner was changed as shown in Table 2, and the amount of magnetic material was changed to 50 parts.
The same evaluation as in Example 1 was performed using the magnetic toner 9. The evaluation results are shown in Table 3.

Comparative Example 4
The formulation of the magnetic toner was changed as shown in Table 2, and the amount of magnetic substance added was changed from 90 parts to 120 parts. Further, the magnetic toner 10 was produced in the same manner as in Example 1 except that the kneading temperature at the time of melt kneading was changed from 140 ° C. to 160 ° C.
In addition, the same evaluation as in Example 1 was performed using the magnetic toner 10. The evaluation results are shown in Table 3.

Comparative Example 5
The formulation of the magnetic toner was changed as shown in Table 2, and the amount of magnetic substance added was changed from 90 parts to 60 parts. Further, in Example 1, the magnetic toner 11 was produced in the same manner except that the kneading temperature at the time of melt kneading was changed from 140 ° C. to 120 ° C.
The same evaluation as in Example 1 was performed using the magnetic toner 11. The evaluation results are shown in Table 3.

Comparative Example 6
A magnetic toner 12 was produced in the same manner as in Example 1 except that the formulation of the magnetic toner was changed as shown in Table 2.
The same evaluation as in Example 1 was performed using the magnetic toner 12. The evaluation results are shown in Table 3.

Comparative Example 7
A magnetic toner 13 was produced in the same manner as in Example 1 except that the formulation of the magnetic toner was changed as shown in Table 2.
The same evaluation as in Example 1 was performed using the magnetic toner 13. The evaluation results are shown in Table 3.

Claims (4)

A magnetic toner having at least a binder resin and a magnetic material,
The magnetic material is magnetic iron oxide having a breakdown voltage of 160 to 1600 V / cm,
A magnetic toner having a dielectric loss tangent (tan δ) at 100 kHz and 40 ° C. of 2.0 × 10 ^{−3 to} 1.0 × 10 ⁻² of the magnetic toner. The magnetic body contains 0.5 to 5.0% by mass of aluminum (Al),
When the magnetic material is washed with a 1 mol / liter sodium hydroxide aqueous solution, the aluminum dissolution rate relative to the total amount of Al of the magnetic material is 40 to 60% by mass,
When the magnetic substance is dissolved in a 1 mol / liter hydrochloric acid aqueous solution, when the iron dissolution rate relative to the total Fe amount of the magnetic substance is 20% by mass, the aluminum dissolution rate relative to the total Al amount of the magnetic substance is 60 to 85% by mass,
When the magnetic material is dissolved in a 1 mol / liter hydrochloric acid aqueous solution, when the iron dissolution rate relative to the total Fe amount of the magnetic material is 60% by mass, the aluminum dissolution rate relative to the total Al amount of the magnetic material is 80 To 95% by mass,
When the magnetic substance is dissolved in a 1 mol / liter hydrochloric acid aqueous solution, when the iron dissolution rate relative to the total Fe amount of the magnetic substance is 80% by mass, the aluminum dissolution rate relative to the total Al amount of the magnetic substance is 95. The magnetic toner according to claim 1, wherein the magnetic toner is 99 to 99% by mass.   The magnetic toner according to claim 1, wherein an isoelectric point of the magnetic material is pH 7.0 or higher and 10.0 or lower.   The magnetic toner according to claim 1, wherein the binder resin is a resin having at least a polyester unit.