JP2020016822A - Magnetic toner and image formation method - Google Patents

Abstract

To provide a magnetic toner which suppresses occurrence of a rear end offset of a high printing ratio image, and can secure durability even in a system to which a shear is applied.SOLUTION: A magnetic toner contains magnetic toner particles containing a binder resin, a magnetic substance and wax, and inorganic fine particles present on the surface of the magnetic toner particles, in a coefficient of variation in an occupancy area ratio of the magnetic substance is 40.0% or more and 80.0% or less, the inorganic fine particles contain specific inorganic oxide fine particles, 85% or more of the inorganic oxide fine particles is silica fine particles, a coverage ratio A of the surface of the magnetic toner particles with the inorganic fine particles is 45.0% or more and 80.0% or less, the wax forms a domain inside the magnetic toner particles, a number average diameter of the domain is 100 nm or more and 500 nm or less, the binder resin contains a styrenic resin, and a peak molecular weight of a main peak of the magnetic toner is 5,000 or more and 12,000 or less.SELECTED DRAWING: None

Description

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

  2. Description of the Related Art In recent years, there has been a demand for means for outputting images in a wide range of fields from offices to homes. As one of the means, there is a demand for high durability without deterioration in image quality even when outputting a large number of images in various use environments. On the other hand, in addition to the image quality, the image output device itself is required to be reduced in size and energy saving.

  As a means for reducing the size, it is effective to reduce the size of the cartridge in which the developer is stored. Therefore, a one-component development method is preferable to a two-component development method using a carrier. And a contact development system. Therefore, in order to satisfy the above performance, the one-component contact developing method is an effective means.

  However, the one-component contact development system is a development system in which a toner carrier and an electrostatic latent image carrier are arranged in contact (contact arrangement). In other words, since these carriers rotate to transport the toner, and the contact portion takes a large share, the toner must have high durability and high fluidity in order to obtain a high-quality image. Required.

  The toner having low fluidity stays in the carrier at the time of development, and is liable to be fused and heated by rubbing. In particular, when fusing in the toner carrier, "streaks" occur on the image.

  On the other hand, toner having low durability causes cracking and chipping, and contaminates the toner carrier and the electrostatic latent image carrier, resulting in deterioration of image quality. Further, the cracked or chipped toner is less likely to be charged, and may be a “fogging” component that is developed on a non-image area on the electrostatic latent image carrier.

  A magnetic toner containing a magnetic substance (hereinafter, also simply referred to as toner) has a large density difference between the resin and the magnetic substance, and when an external force is applied, the force is concentrated on the resin and displaced, whereby the resin is cut. In particular, cracking and chipping of the toner are likely to occur.

  When it is desired to output a large number of images in various use environments, a further load is applied to the toner, so that higher durability and higher fluidity are required.

  Patent Document 1 proposes a toner containing a magnetic material.

  Patent Document 2 proposes a magnetic toner in which a magnetic substance is dispersed by using an aggregation method. This manufacturing method has an aggregating step of aggregating the fine particles to the particle diameter of the toner, and a unifying step of melting the agglomerated body to unite into a toner. In this method, the shape of the toner can be easily deformed, and the fluidity can be increased.

  Patent Literature 3 discloses that it is possible to achieve both the image density in a durability test and the suppression of a decrease in density when rubbed by rubbing by specifying the presence state of a specific wax and inorganic fine particles on the toner surface. ing.

  In Patent Document 4, the total coverage of the toner base particles with the external additive is controlled to stabilize the development and transfer steps.

JP 2006-243593 A JP 201293775 A Japanese Patent No. 5361984 JP 2007-29043 A

  The toner using the manufacturing method disclosed in Patent Document 1 has a problem that it is difficult to increase the degree of circularity, and in a system such as a one-component contact developing system that has a large share, toner fusion is likely to occur. ing.

  The toner disclosed in Patent Literature 2 can absorb the shear in a system such as a one-component contact development system in which the magnetic material has a uniform interval between the magnetic materials and the magnetic materials exist at a relatively short distance. However, there is a problem that the portion is insufficient and toner deterioration is likely to occur.

  Conversely, the toner in which the magnetic material is excessively aggregated has a problem that the coloring power is reduced due to the decrease in the surface area of the magnetic material, and the density of the output image is easily reduced. Further, such a toner has a problem that the content ratio of the magnetic substance tends to be different for each toner particle, and the image density gradually decreases when outputting a large number of images.

  Certainly, the toner disclosed in Patent Document 4 achieves a certain effect by controlling the theoretical theoretical coverage of a specific toner base particle. However, the actual state of attachment of the external additive may be significantly different from the calculated value when the toner is assumed to be a perfect sphere. If not, it is not enough. As a result of the study by the present inventors, when the image output apparatus is further speeded up or applied to the above-described one-component contact developing method, it is necessary to further improve durability and responsiveness to heat during fixing.

  The present invention provides a high-quality image in various use environments even in a system such as a one-component contact developing system having a large share.

  That is, with respect to the above-mentioned patent document, there is room for improvement from the viewpoint of ensuring the durability and the responsiveness to heat at the time of fixing even in a system having a larger share.

  Focusing on the fixing process from the viewpoint of further improving the image quality, the problem that has become apparent with the diversification of the purpose of use and the use environment is that the offset ( Hereinafter, this is also referred to as a trailing end offset.).

  Generally, in a fixing process, when paper on which an unfixed image is formed by toner passes through a fixing device (particularly, a portion passing therethrough is hereinafter referred to as a fixing nip), heat and pressure are applied thereto. The toner is fixed to the paper.

  The reason why the trailing edge offset is more likely to occur in the high printing rate image than in the low printing rate image is considered to be due to the amount of heat applied to the toner layer. The higher the printing rate image becomes, the more the amount of heat from the fixing device is dispersed to more toner, so that the amount of toner that is insufficiently melted increases, and a state in which fixing failure occurs easily occurs.

  Furthermore, since the amount of heat given from the fixing nip tends to be smaller at the rear end of the image, the fixability of the rear end of the image tends to be disadvantageous.

  In particular, the trailing edge offset tends to be noticeable in paper left in a high-temperature, high-humidity environment. When a paper containing a large amount of water passes through the fixing device when left in a high-temperature and high-humidity environment, water vapor is generated from the paper by heat from the fixing device in the fixing nip. It is presumed that the trailing edge offset is caused by the water vapor pressing the toner layer on the paper toward the fixing member.

  In other words, when a sheet left in a high-temperature and high-humidity environment is used in a state where fixing failure is likely to occur at the rear end of an image with a high printing ratio, a rear end offset is likely to occur.

  Further, conventionally, improvements such as designing a softening temperature to be low have been made in order to improve the fixability of the toner. Certainly, with such a design, the heat fusibility of the part to which heat is sufficiently applied is improved. However, on the other hand, if the amount of applied heat is insufficient, such as at the trailing edge of a high-print-rate image, the melting speed of the toner cannot catch up, and it is difficult to suppress the occurrence of the trailing-end offset of the high-print-rate image. Was.

  That is, the present invention provides a magnetic toner that suppresses the occurrence of a trailing edge offset of a high printing ratio image even in a high-temperature and high-humidity environment, and that can ensure durability even in a system that requires a share, and a method using the magnetic toner. And an image forming method.

The present invention
A magnetic toner containing a binder resin, a magnetic toner particle containing a magnetic substance and a wax, and inorganic fine particles present on the surface of the magnetic toner particle,
In the cross section of the magnetic toner using a transmission electron microscope,
A coefficient of variation CV3 of the occupied area ratio of the magnetic material when the cross section of the magnetic toner is divided by a square grid having a side of 0.8 μm is 40.0% or more and 80.0% or less;
The inorganic fine particles contain at least one inorganic oxide fine particle selected from the group consisting of silica fine particles, titania fine particles, and alumina fine particles, and 85% by mass or more of the inorganic oxide fine particles are silica fine particles,
Assuming that the coverage of the surface of the magnetic toner particles with the inorganic fine particles is coverage A (%), the coverage A is 45.0% or more and 80.0% or less;
The wax forms a domain inside the magnetic toner particles, and the number average diameter of the domain is 100 nm or more and 500 nm or less,
The binder resin contains a styrene resin,
A magnetic toner characterized in that the main peak has a peak molecular weight of 5,000 or more and 12,000 or less, as measured by gel permeation chromatography of a tetrahydrofuran-soluble component of the magnetic toner.

Also, the present invention
A charging step of applying a voltage to the charging member from outside to charge the electrostatic latent image carrier,
A latent image forming step of forming an electrostatic latent image on the charged electrostatic latent image carrier,
A developing step of developing the electrostatic latent image with a toner carried on a toner carrier to form a toner image on the electrostatic latent image carrier;
A transfer step of transferring the toner image on the electrostatic latent image carrier to a transfer material with or without an intermediate transfer member, and
An image forming method including a fixing step of fixing a toner image transferred to a transfer material by heating and pressing means,
The developing step is a one-component contact developing method in which the electrostatic latent image carrier and the toner carried on the toner carrier are directly contacted to perform development,
The toner is
A magnetic toner containing a binder resin, a magnetic toner particle containing a magnetic substance and a wax, and inorganic fine particles present on the surface of the magnetic toner particle,
In the cross section of the magnetic toner using a transmission electron microscope,
A coefficient of variation CV3 of the occupied area ratio of the magnetic material when the cross section of the magnetic toner is divided by a square grid having a side of 0.8 μm is 40.0% or more and 80.0% or less;
The inorganic fine particles contain at least one inorganic oxide fine particle selected from the group consisting of silica fine particles, titania fine particles, and alumina fine particles, and 85% by mass or more of the inorganic oxide fine particles are silica fine particles,
Assuming that the coverage of the surface of the magnetic toner particles with the inorganic fine particles is coverage A (%), the coverage A is 45.0% or more and 80.0% or less;
The wax forms a domain inside the magnetic toner particles, and the number average diameter of the domain is 100 nm or more and 500 nm or less,
The binder resin contains a styrene resin,
An image forming method, wherein the main peak has a peak molecular weight of 5,000 or more and 12,000 or less as measured by gel permeation chromatography of a tetrahydrofuran-soluble component of the magnetic toner.

  According to the present invention, even in a high-temperature and high-humidity environment, the occurrence of a rear end offset of a high print ratio image is suppressed, and a magnetic toner capable of ensuring durability even in a system requiring a share, and a method using the magnetic toner Image forming method can be provided.

Schematic sectional view of the developing device Schematic sectional view of an image forming apparatus of a one-component contact developing system (A) A schematic diagram showing an example of a mixing device that can be used for externally adding and mixing inorganic fine particles, and (b) a schematic diagram showing an example of a configuration of a stirring member used in the mixing device. (A) A diagram showing an example of the relationship between the number of added silica and the coverage, and (b) a diagram showing an example of the relationship between the number of added silica and the coverage. Diagram showing an example of the relationship between the coverage and the coefficient of static friction Diagram showing an example of the relationship between ultrasonic dispersion time and coverage

  In the present invention, description of “XX or more and XX or less” or “XX to XX” representing a numerical range means a numerical range including a lower limit and an upper limit which are endpoints unless otherwise specified.

  Further, the monomer unit refers to a reacted form of a monomer substance in a polymer.

  Hereinafter, the present invention will be described in more detail with reference to embodiments, but the present invention is not limited thereto.

The magnetic toner of the present invention (hereinafter, also simply referred to as toner) is
A magnetic toner containing a binder resin, a magnetic toner particle containing a magnetic substance and a wax, and inorganic fine particles present on the surface of the magnetic toner particle,
In the cross section of the magnetic toner using a transmission electron microscope,
A coefficient of variation CV3 of the occupied area ratio of the magnetic material when the cross section of the magnetic toner is divided by a square grid having a side of 0.8 μm is 40.0% or more and 80.0% or less;
The inorganic fine particles contain at least one inorganic oxide fine particle selected from the group consisting of silica fine particles, titania fine particles, and alumina fine particles, and 85% by mass or more of the inorganic oxide fine particles are silica fine particles,
Assuming that the coverage of the surface of the magnetic toner particles with the inorganic fine particles is coverage A (%), the coverage A is 45.0% or more and 80.0% or less;
The wax forms a domain inside the magnetic toner particles, and the number average diameter of the domain is 100 nm or more and 500 nm or less,
The binder resin contains a styrene resin,
The peak molecular weight of the main peak, as measured by gel permeation chromatography of a tetrahydrofuran-soluble component of the magnetic toner, is 5,000 or more and 12,000 or less.

  In the magnetic toner, the dispersion state of the magnetic substance in the magnetic toner particles and the coating state of the inorganic fine particles present on the surface of the magnetic toner particles (hereinafter, also simply referred to as toner particles) are controlled.

  By using the toner, the image quality is excellent even in an image forming apparatus having a strong share of the toner, and it is possible to suppress the occurrence of the trailing edge offset of the high print ratio image even in a high temperature and high humidity environment. .

  The reason is not clear, but the present inventors think as follows.

  The toner fixing step is a step of promoting melting and deformation of the toner due to heat of the fixing member and fixing the toner to a medium such as paper. Therefore, when the amount of heat is reduced with the aim of fixing with energy saving, various factors are important for fixing the toner on the medium.

  It is important to quickly deform the toner particles in response to heat given from the outside and to increase the force to adhere to the medium rather than the force to adhere to the fixing member. Further, as will be described in detail later, it is also important to make the toner layer on the paper before fixing uniform. By doing so, the amount of heat can be efficiently transmitted to all the toners on the medium, sufficient fixability can be obtained even with a small amount of heat, and the occurrence of rear end offset can be effectively suppressed. Further, the toner having the above configuration is excellent in the deformability of the toner particles and the effect of extruding the wax, the releasability of the toner from the fixing member is increased, and the adhesiveness (anchoring effect) to paper is relatively increased. I guess.

  The peak molecular weight (Mp) of the main peak, measured by gel permeation chromatography (GPC) using a tetrahydrofuran (THF) soluble portion of the magnetic toner, is 5,000 or more and 12,000 or less. It is believed that by controlling the molecular weight to be relatively low, the deformability of the magnetic toner due to heat can be increased.

  Further, in the magnetic toner, when the coverage of the surface of the magnetic toner particles with the inorganic fine particles is defined as coverage A (%), the coverage A is 45.0% or more and 80.0% or less. The coverage A is preferably 50.0% or more and 80.0% or less.

  The toner on the paper after the transfer process is adhered and fixed on the paper by passing through the fixing device. At the stage before fixing, since it exists in a state of being transferred from the photoreceptor onto a medium such as paper, it is still movable in that state.

  In order to transmit the heat from the fixing device most efficiently and evenly to the toner without bias, it is necessary to increase the area where the toner on the paper comes into contact with the fixing device after the transfer process, that is, reduce the number of toners directly contacting the fixing member. It is considered effective to do as much as possible. For this purpose, it is considered effective to control the toner layer on the paper to be uniform and to make the surface in contact with the fixing device as uneven as possible.

  Since the magnetic toner has a relatively high coverage A of 45.0% or more and 80.0% or less with inorganic fine particles, it has a low van der Waals force and a low electrostatic adhesion force with a contacting member. Adhesion between them is also reduced.

  Therefore, the toner after the transfer step hardly causes aggregation due to the low adhesion between the toners, and the toner layer is more closely packed. Therefore, the toner layer is made uniform, the unevenness on the upper portion of the toner layer hardly exists, and the area in contact with the fixing device can be increased.

  This effect also makes it possible to widen the application range of media such as paper.For example, even when the paper itself has large irregularities such as rough paper and the toner layer tends to be non-uniform, the low toner adhesion is low. Thus, it is possible to obtain an effect similar to that of smooth paper.

  In addition, since the magnetic toner has a low van der Waals force and a low electrostatic adhesion to a fixing member such as a fixing film, the releasing effect from the fixing member is large, and the anchoring effect on paper is relatively small. Can promote.

The low van der Waals force and the low electrostatic adhesion force will be described in detail below. First, regarding the van der Waals force, the van der Waals force (F) generated between the flat plate and the grains is represented by the following equation.
F = H × D / (12Z ² )

  Here, H is the Hammer constant, D is the particle size of the particles, and Z is the distance between the particles and the flat plate. Regarding Z, it is generally said that an attractive force acts when the distance is long and a repulsive force acts when the distance is very short. Since Z is not related to the state of the magnetic toner surface, it is treated as a constant. From the above equation, the van der Waals force (F) is proportional to the particle size of the particles in contact with the flat plate. When this is applied to the surface of the magnetic toner, the van der Waals force (F) is smaller when the inorganic fine particles having a small particle diameter are in contact with the flat plate than when the magnetic toner particles are in contact with the flat plate. That is, the van der Waals force is smaller when the magnetic toner particles are in contact with the fixing member via the inorganic fine particles as the external additive than when they are directly in contact with the fixing member.

  Next, the electrostatic adhesion force can be translated into a reflection force. It is known that the mirroring power is generally proportional to the square of the charge (q) of a particle and inversely proportional to the square of the distance.

  When the magnetic toner is charged, it is not the inorganic fine particles but the surface of the magnetic toner particles that has the charge. Therefore, the greater the distance between the surface of the magnetic toner particles and the flat plate (here, the fixing member), the smaller the mirroring power.

  That is, on the surface of the magnetic toner, if the magnetic toner particles are in contact with the flat plate via the inorganic fine particles, the distance between the surface of the magnetic toner particle and the flat plate is increased, and the mirror power is reduced.

  As described above, the inorganic fine particles are present on the surface of the magnetic toner particles, and the magnetic toner contacts the fixing member via the inorganic fine particles, so that the Van der Waals force and the mirror force generated between the magnetic toner and the fixing member are reduced. . That is, the adhesive force between the magnetic toner and the fixing member decreases.

  Next, whether the magnetic toner particles directly contact the fixing member or via the inorganic fine particles depends on how much the inorganic fine particles cover the surface of the magnetic toner particles, that is, the coverage of the inorganic fine particles.

  When the coverage of the inorganic fine particles is high, the chance that the magnetic toner particles come into direct contact with the fixing member decreases, and it is considered that the magnetic toner hardly sticks to the fixing member.

  Further, when the coverage of the surface of the magnetic toner particles is relatively high, the hardness of the surface is increased, so that the magnetic toner particles are more resistant to external shares. It is presumed that this is because the properties of the surface of the magnetic toner particles are closer to those of the inorganic fine particles than the binder resin due to the inorganic fine particles present on the surface of the magnetic toner particles.

  As a result, in a system with a large share, even if a large number of images are output, a decrease in image density is suppressed.

  In the magnetic toner, when the cross section of the magnetic toner is sectioned by a square grid of 0.8 μm on a cross section of the magnetic toner using a transmission electron microscope (TEM), a change in the occupied area ratio of the magnetic material is obtained. The coefficient CV3 is 40.0% or more and 80.0% or less. The CV3 is preferably 50.0% or more and 70.0% or less.

  The variation coefficient CV3 of the occupied area ratio of the magnetic material is obtained from the frequency histogram of the occupied area ratio of the magnetic material on a square grid having a side of 0.8 μm by the partitioning method in the cross section of the magnetic toner.

  The fact that the CV3 is within the above range means that the magnetic material is locally localized in the magnetic toner particles. That is, by unevenly distributing the magnetic material in the magnetic toner particles, a portion where the magnetic material does not exist (hereinafter, also referred to as a binder portion between the magnetic materials) can be appropriately provided, and the portion absorbs an external shear. It is possible to do.

  For example, in a system such as the above-described one-component contact developing method, in which the magnetic material is locally unevenly distributed and the binder between the magnetic materials is compared with the case where the distance between the magnetic materials is uniform and relatively short. By providing the portion, the durability of the toner is improved.

  Further, as described above, the ease with which the magnetic toner particles are deformed is important, but the deformation of the toner particles is promoted by providing the binder between the magnetic materials. The reason is presumed to be that the filler effect due to the magnetic material is reduced.

  In other words, it is presumed that the binder between the magnetic materials absorbs an external shear at the temperature near the developing device during printing and plays an important role in the deformation of the toner particles at the time of fixing.

  When the CV3 is in the above range, it is easy to suppress cracking of the toner when external shear is applied. Therefore, in a system having a high share such as a one-component contact developing method, there is no image problem such as a decrease in image density or a development streak when a large number of images are output, and a good image in which generation of fog is suppressed is suppressed. Obtainable.

  When the CV3 is less than 40.0%, the difference in the occupied area ratio of the magnetic material is small between grids dividing the cross section of the magnetic toner, and the amount of the binder portion between the magnetic materials may decrease. is there.

  In this case, the connection between the binder resins becomes thinner, and the brittleness of the magnetic toner particles is apt to be reduced. Is easy to occur.

  Further, the filler effect of the magnetic material tends to be large, and the deformation of the toner particles when heat is applied during fixing tends to be slow.

  On the other hand, when the CV3 exceeds 80.0%, the magnetic substance is excessively localized in the toner. In this case, the magnetic substances are aggregated with each other, and the coloring power is reduced due to the decrease in the surface area, and the image density is reduced.

  Methods for adjusting the CV3 to the above range include controlling the hydrophilic / hydrophobic property of the surface of the magnetic material, controlling the degree of aggregation of the magnetic material during the production of the toner particles, and the like.

  For example, when the emulsion aggregation method is used, the degree of aggregation of the magnetic substance is reduced by adding a chelating agent and / or adjusting the pH in a coalescing step in which the magnetic substance is previously aggregated and introduced into the toner particles. Adjustment methods and the like can be mentioned.

  The magnetic toner has a ratio of an occupied area ratio of the magnetic material when a cross section of the magnetic toner is divided by a square grid having a side of 0.8 μm in a cross section of the magnetic toner using a transmission electron microscope (TEM). The average value is preferably from 10.0% to 40.0%. More preferably, it is 15.0% or more and 30.0% or less.

  When the average value of the occupied area ratio is in the above range, the dispersion state of the magnetic substance in the toner particles is in an appropriate state, and it is possible to suppress a decrease in coloring power due to an excessive aggregation state.

  Further, even in a system such as a one-component contact developing system in which a high share is applied to the toner, it is easy to suppress the occurrence of toner cracking. As a result, fog hardly occurs and a good image can be obtained.

  When the occupied area ratio is less than 10.0%, the content of the magnetic substance is low, and the image density tends to decrease due to a decrease in coloring power. On the other hand, when the occupied area ratio exceeds 40.0%, the content of the magnetic substance is high, and depending on the dispersion state of the magnetic substance, the brittleness of the toner is easily reduced, the toner is easily broken, and fog is easily generated. .

  The average value of the occupied area ratio of the magnetic material is controlled in the above range by controlling the hydrophilic / hydrophobic property of the surface of the magnetic material and controlling the degree of aggregation of the magnetic material during the production of toner particles. And the like.

  Generally, in a toner containing a magnetic substance, it is preferable that the magnetic substance is more uniformly contained between the toner particles. When toner particles having different contents of the magnetic substance are present, the chargeability and the magnetic performance are different. In such a case, especially in a system having a magnetic conveyance or a system in which development is performed by controlling the charging property and magnetic performance of the toner, there is a possibility that a difference occurs in development behavior for each toner, and as a result, image defects such as a decrease in density are caused. May cause

  Further, the brightness of the toner is an index indicating the degree of scattering of light of the toner, and the brightness of the toner is reduced by containing a substance such as a colorant or a magnetic material that absorbs light.

  On the other hand, the luminance dispersion value of the toner is an index for measuring how much the luminance is biased in one toner particle in the luminance measurement. For this reason, the variation coefficient of the luminance dispersion value is an index for checking how much the luminance varies among the toner particles.

  The present inventors considered controlling the content ratio of the magnetic substance among the magnetic toner particles, and by setting the variation coefficient of the luminance and the luminance dispersion value to an appropriate value, it was possible to obtain a good image without a decrease in density. Was found to be able to be obtained.

The number average particle diameter of the magnetic toner is Dn (μm),
A coefficient of variation of a luminance dispersion value of the magnetic toner in a range of Dn−0.500 or more and Dn + 0.500 or less is CV1 (%),
When the variation coefficient of the luminance dispersion value of the magnetic toner in the range of Dn-1.500 to Dn-0.500 is CV2 (%),
It is preferable that the CV1 and the CV2 satisfy the relationship of the following formula (1).
CV2 / CV1 ≦ 1.00 (1)
The ratio CV2 / CV1 is more preferably 0.70 or more and 0.95 or less.

  When CV2 / CV1 is in the above range, the content of the magnetic substance in the magnetic toner particles becomes less dependent on the particle diameter of the toner particles. As a result, uneven charging of the toner particles and uneven magnetic characteristics are easily suppressed, and even when a large number of images are output, the developability tends to be good.

  The ratio CV2 / CV1 can be adjusted according to the particle size of the magnetic material and the production conditions in producing the toner.

  The CV1 is preferably 4.00% or less, more preferably 3.50% or less.

  When CV1 is in the above range, there is little difference in the presence state of the magnetic substance between the toner particles, and the image density after continuous image formation is hardly changed, and a good image can be obtained.

  The CV1 can be adjusted by controlling the dispersion state of the magnetic material during the production of the toner particles.

  The average brightness at Dn of the magnetic toner is preferably 30.0 or more and 60.0 or less, more preferably 35.0 or more and 50.0 or less.

  When the average luminance is in the above range, the content of the magnetic substance is appropriate, and a good coloring power is exhibited. At the same time, cracking of the toner is easily prevented, and generation of fog can be further suppressed.

  The average luminance can be adjusted to the above range by adjusting the content of the magnetic substance.

  As described above, by setting the coverage A of the surface of the magnetic toner particles by the inorganic fine particles in a specific range, the adhesive force to the member can be reduced. Then, the coverage of the inorganic fine particles and the adhesive force with the member were verified.

  The relationship between the coverage of the magnetic toner and the adhesive force between the members was indirectly estimated by measuring the coefficient of static friction between the spherical polystyrene particles having varied coverage by the silica fine particles and the aluminum substrate. Specifically, spherical polystyrene particles (weight average particle size (D4) = 7.5 μm) with different coverage by silica fine particles (coverage determined by observation with a scanning electron microscope) were used. The relationship between the coefficients was determined.

  More specifically, spherical polystyrene particles to which silica fine particles are added are pressed on an aluminum substrate. The substrate was moved right and left while changing the pressure, and the static friction coefficient was calculated from the stress at that time. This is performed for each spherical polystyrene particle having a different coverage, and the relationship between the obtained coverage and the coefficient of static friction is shown in FIG.

  The coefficient of static friction determined by such a method is considered to correlate with the sum of the Van der Waals force and the mirror force acting between the spherical polystyrene particles and the substrate. As is clear from the graph, the higher the coverage of the inorganic fine particles, the lower the static friction coefficient. This suggests that a magnetic toner having a high coverage has a small adhesive force to a member.

  Here, when the coverage A is larger than 80.0%, the action of the wax tends to be hindered and the rear end offset is likely to occur even in the configuration of the magnetic toner particles.

  When the coverage by the inorganic fine particles fixed to the surface of the magnetic toner particles is defined as coverage B (%), the ratio of the coverage B to the coverage A (hereinafter, also referred to as B / A) is 0. It is preferable that it is .50 or more and 0.85 or less. More preferably, it is 0.55 or more and 0.80 or less.

  The coverage A is a coverage including inorganic fine particles which can be easily released, and the coverage B is based on inorganic fine particles fixed on the surface of the magnetic toner particles, which are not released by a releasing operation described later. The inorganic fine particles represented by the coverage B are fixed to the surface of the magnetic toner particles in a semi-buried state, and move on the developing sleeve or the electrostatic latent image carrier even if the magnetic toner receives a share. It is thought that there is no.

  On the other hand, the inorganic fine particles represented by the coverage A include the above-mentioned fixed inorganic fine particles and the inorganic fine particles having a relatively high degree of freedom existing in the upper layer.

  As described above, the effect of reducing the van der Waals force and the electrostatic adhesion force is affected by the inorganic fine particles that can be present between the magnetic toner and between the magnetic toner and each member, and the coverage A is increased. Is considered to be particularly important in terms of this effect.

  When the B / A is within the above range, it means that the inorganic fine particles fixed to the surface of the magnetic toner are present to some extent, and the inorganic fine particles can be easily liberated thereon (the state where the inorganic fine particles can behave apart from the magnetic toner particles). ) Means that an appropriate amount is present. Probably, the free inorganic fine particles slide on the fixed inorganic fine particles, thereby exerting an effect like a bearing, and the cohesive force between the magnetic toners is greatly reduced.

  As a result of the study by the present inventors, the above-described adhesive force reducing effect and bearing effect are maximized when the inorganic fine particles are relatively small inorganic fine particles having a number average primary particle diameter (D1) of about 50 nm or less. It turned out to be obtained. Therefore, when calculating the coverage A and the coverage B, attention was paid to inorganic fine particles of 50 nm or less.

  By setting the coverage A and B / A in a specific range, the magnetic toner can reduce the adhesive force between the magnetic toner and each member and greatly reduce the cohesive force between the magnetic toners. .

  As a result, the contact area between the toner and the fixing member can be increased by making the magnetic toner layer uniform by the closest packing of the magnetic toner layer when passing through the fixing device.

  In addition, by combining with the effect of exuding the wax by optimizing the composition of the binder resin and the wax, an efficient anchoring effect on the medium can be obtained, and the above effect can be exhibited. Thereby, even in a configuration in which the heat conduction efficiency tends to be low, for example, in a case where the rough paper is combined with the light pressure fixing using the fixing film, it is possible to greatly reduce the generation of the toner having insufficient heat conduction. it can.

  The coverage A, the coverage B, and the ratio [B / A] of the coverage B to the coverage A can be determined by a method described below.

  Further, the coefficient of variation of the coverage A is preferably 10.0% or less, more preferably 8.0% or less.

  A coefficient of variation of 10.0% or less means that the coverage A between the magnetic toner particles and within the magnetic toner particles is extremely uniform. When the coverage is uniform, the uniformity of charging of the toner is improved, and even when a large number of images are output, developability such as image density is easily stabilized. Further, since the covering state of the surface of the magnetic toner is uniform, the cohesive force between the magnetic toners is easily reduced.

  The method for reducing the coefficient of variation to 10.0% or less is not particularly limited, but an external addition device such as described below, which can highly diffuse inorganic oxide fine particles such as silica fine particles on the surface of the magnetic toner particles, It may be adjusted using a technique.

  As for the coverage of the inorganic fine particles as the external additive, assuming that the inorganic fine particles and the magnetic toner are spherical, it can be derived by the calculation formula described in Patent Document 4 and the like. However, in many cases, the inorganic fine particles and the magnetic toner are not truly spherical, and the inorganic fine particles may be present in an aggregated state on the surface of the magnetic toner particles. Not relevant.

  Therefore, the present inventors performed a scanning electron microscope (SEM) observation of the surface of the magnetic toner, and determined a covering ratio at which the inorganic fine particles actually covered the surface of the magnetic toner particles.

As an example, 100 parts by mass of magnetic toner particles (the content of the magnetic substance is 43.5% by mass) obtained by a pulverization method having a volume average particle diameter (Dv) of 8.0 μm is added with the addition amount of silica fine particles (the number of silica addition parts). The theoretical coverage and the actual coverage of the mixed mixture were determined (FIGS. 4A and 4B). In addition, as the silica fine particles, silica fine particles having a volume average particle diameter (Dv) of 15 nm were used. Also, when calculating the theoretical coverage, a true specific gravity of the silica fine particles 2.2 g / cm ^3, the true specific gravity of the magnetic toner and 1.65 g / cm ^3, with respect to the silica fine particles and the magnetic toner particles, each particle Monodispersed particles having a diameter of 15 nm and 8.0 μm were obtained.

  As is clear from FIG. 4A, the theoretical coverage exceeds 100% as the number of added silica is increased. On the other hand, the coverage obtained by actual observation varies with the number of added silica, but does not exceed 100%. This is because silica fine particles partially exist on the surface of the magnetic toner as aggregates, or the silica fine particles are not perfectly spherical.

  In addition, according to the study by the present inventors, it was found that the covering ratio changes by the external addition method even when the addition amount of the silica fine particles is the same. That is, it is impossible to determine the covering rate uniquely from the amount of the added inorganic fine particles (see FIG. 4B). The external addition condition A was obtained by mixing under the conditions of 1.0 W / g and a processing time of 5 minutes using the apparatus of FIG. The external addition condition B was obtained by mixing using an FM mixer FM10C (manufactured by Nippon Coke Industry Co., Ltd.) under the conditions of 4000 rpm and a processing time of 2 minutes.

  For these reasons, the present inventors used the coverage of inorganic fine particles obtained by SEM observation of the surface of the magnetic toner.

  A known material may be used as the wax. Specific examples of the wax include the following.

  Aliphatic hydrocarbon waxes such as low molecular weight polyethylene, low molecular weight polypropylene, microcrystalline wax, Fischer-Tropsch wax, paraffin wax; oxides of aliphatic hydrocarbon waxes such as oxidized polyethylene wax, or block copolymers thereof A wax mainly containing a fatty acid ester such as carnauba wax and montanic acid ester wax, and a partially or totally deoxidized fatty acid ester such as deoxidized carnauba wax; palmitic acid, stearic acid, montanic acid, etc. Unsaturated fatty acids such as brassic acid, eleostearic acid, and parinaric acid; stearyl alcohol, aralkyl alcohol, behenyl alcohol, carnaubyl alcohol, seryl alcohol, merisil Saturated alcohols such as alcohol; polyhydric alcohols such as sorbitol; fatty acid amides such as linoleic acid amide, oleic acid amide, lauric acid amide; methylene bisstearic acid amide, ethylenebiscapric acid amide, ethylenebislauric acid amide; Saturated fatty acid bisamides such as hexamethylenebisstearic acid amide; unsaturated fatty acids such as ethylenebisoleic acid amide, hexamethylenebisoleic acid amide, N, N 'dioleyl adipamide, N, N' dioleyl sebacic amide Amides; aromatic bisamides such as m-xylene bisstearic acid amide and N, N 'distearylisophthalic acid amide; fats such as calcium stearate, calcium laurate, zinc stearate and magnesium stearate Metal salts (commonly referred to as metal soaps); waxes obtained by grafting aliphatic hydrocarbon waxes with vinyl monomers such as styrene and acrylic acid; fatty acids such as behenic acid monoglyceride and polyhydric alcohols Partially esterified products; methyl ester compounds having a hydroxy group obtained by hydrogenation of vegetable oils and the like.

  Among them, hydrocarbon waxes such as paraffin wax and Fischer-Tropsch wax are preferred. When the wax contains a hydrocarbon wax, it becomes relatively easy to suppress compatibility with the binder resin. As a result, the releasing effect on the fixing member is improved, and the rear end offset is easily suppressed.

  The content of the wax is preferably from 1.0 part by mass to 30.0 parts by mass, and more preferably from 3.0 parts by mass to 25.0 parts by mass with respect to 100 parts by mass of the binder resin. Is more preferred.

  Further, the content ratio of the hydrocarbon wax to the total amount of the wax is preferably 35% by mass or more and 100% by mass or less.

  By adjusting the content of the wax in the above range, the releasability of the toner particles can be further improved.

  The peak temperature of the maximum endothermic peak measured by differential scanning calorimetry (DSC) of the wax is preferably from 60 ° C to 120 ° C, more preferably from 60 ° C to 90 ° C.

  The wax forms a domain inside the magnetic toner particles, and the number average diameter of the domain is 100 nm or more and 500 nm or less. The number average diameter of the domains is preferably 200 nm or more and 500 nm or less.

  The number average diameter of the domains is determined by randomly selecting 30 wax domains having a major axis of 20 nm or more in the cross section of magnetic toner particles using a transmission electron microscope (TEM), and averaging the major axis and the minor axis. Was defined as the domain diameter, and the average value of 30 domains was defined as the number average diameter of the domains. Note that the selection of the domain may not be in the same toner particle.

  In the fixing step of the toner, one factor for effectively suppressing the occurrence of the trailing end offset is to reduce the adhesive force to the fixing member.

  As a result of the study by the present inventors, it has been found that when the toner particles are deformed, when the number average diameter of the domains is in the above range, the effect of extruding the wax can be exerted to the maximum.

  When the number average diameter of the domains is less than 100 nm, the crystal structure of the wax becomes weak. In particular, in a system having a high share such as a one-component contact development system, a long-term share of the toner causes a part of the crystal structure of the wax to collapse and the wax to be in a molten state. As a result, the wax oozes out on the surface of the toner particles, and an image defect such as a development streak occurs.

  On the other hand, if the number average diameter of the domains exceeds 500 nm, the extrusion speed of the wax at the time of toner deformation tends to decrease, and it is difficult to obtain a releasing effect on the fixing member.

  That is, by setting the number average diameter of the domains to the above range, it is possible to suppress the exudation of the wax when the shear is applied, and to promote the extrusion of the wax when the toner is deformed due to the heat. Can be.

  The number average diameter of the domains can be adjusted by the amount of wax added, when the emulsion aggregation method is used as a method for producing the toner, the diameter of the wax particles in the wax dispersion, the holding time in the coalescing step, and the like. .

  When the CV3 is adjusted to 40.0% or more and 80.0% or less, it becomes easy to adjust the number average diameter of the domain to the above range.

  In a cross section of the magnetic toner particles using a transmission electron microscope, when the area occupied by the wax in a region within 1.0 μm from the contour of the cross section is Ws, the Ws is 1.5% to 18.0%. The following is preferred. More preferably, it is 2.0% or more and 15.0% or less.

  When Ws is in the above range, the amount of wax in the vicinity of the surface layer of the toner particles becomes appropriate, and localization of the magnetic substance and uneven distribution of the wax on the surface of the toner particles can be prevented.

  As a result, in a system such as a one-component contact developing system in which a high share is applied to the toner, it is possible to further suppress development fog caused by cracking of the toner and development streaks caused by exudation of wax.

  The value of Ws can be adjusted by the amount of wax added, the heat treatment time and the heat treatment temperature in the toner production process. When an emulsion aggregation method is used as a method for producing the toner, the aggregation speed of the wax may be controlled or the timing of mixing with another material may be controlled.

  In a cross section of the magnetic toner particles using a transmission electron microscope, assuming that the occupied area percentage of the wax in an inner region inside of 1.0 μm from the contour of the cross section is Wc, a ratio of the Wc to the Ws (Wc / Ws) is preferably 2.0 or more and 10.0 or less. More preferably, it is more preferably 3.0 or more and 8.0 or less.

  When the Wc / Ws is within the above range, the wax can be in a state not localized in the surface layer of the toner particles. As a result, the amount of wax in the vicinity of the surface layer of the toner particles becomes appropriate, and localization of the magnetic material and uneven distribution of the wax on the surface of the toner particles can be prevented.

  As a result, in a system in which the toner has a high share such as a one-component contact developing system, fog due to toner cracking and development streaks caused by exudation of wax can be further suppressed, and a good image can be obtained over a long period of time. be able to.

  The Wc / Ws can be adjusted by the amount of the wax added, the heat treatment time and the heat treatment temperature in the toner production process. When an emulsion aggregation method is used as a method for producing the toner, the aggregation speed of the wax may be controlled or the timing of mixing with another material may be controlled.

  The binder resin of the magnetic toner contains a styrene resin.

  In addition, the peak molecular weight (Mp) of the main peak, measured by gel permeation chromatography (GPC) using a tetrahydrofuran (THF) soluble portion of the magnetic toner, is 5,000 or more and 12,000 or less. Further, the peak molecular weight (Mp) of the main peak is preferably from 6,000 to 11,000.

  By adopting the resin composition and setting the peak molecular weight (Mp) within the above range, the deformability of the resin and the effect of exuding the wax can be significantly improved. As a result, the releasability of the magnetic toner from the fixing member is improved, and the adhesion (anchoring effect) to the paper is relatively increased, so that the occurrence of the rear end offset can be suppressed.

  By controlling the peak molecular weight (Mp) to a relatively low molecular weight of 5000 or more and 12000 or less, the deformability of the magnetic toner due to heat can be increased.

  The peak molecular weight (Mp) can be controlled in the above range by appropriately selecting the type of a monomer that forms the following styrene resin or appropriately adjusting the amount of the polymerization initiator.

  The styrene resin is a resin having a monomer unit derived from styrene in a polymer. For example, a copolymer of styrene with another monomer may be mentioned.

  The monomers that can be used for the production of the styrene resin include the following monomers in addition to styrene.

Aliphatic vinyl hydrocarbons: alkenes such as ethylene, propylene, butene, isobutylene, pentene, heptene, diisobutylene, octene, dodecene, octadecene, and other α-olefins;
Alkadienes such as butadiene, isoprene, 1,4-pentadiene, 1,6-hexadiene and 1,7-octadiene.

Alicyclic vinyl hydrocarbons: mono- or di-cycloalkenes and alkadienes, such as cyclohexene, cyclopentadiene, vinylcyclohexene, ethylidene bicycloheptene;
Terpenes such as pinene, limonene, indene.

  Aromatic vinyl hydrocarbon: Hydrocarbyl (alkyl, cycloalkyl, aralkyl and / or alkenyl) -substituted styrene, for example, α-methylstyrene, vinyltoluene, 2,4-dimethylstyrene, ethylstyrene, isopropylstyrene, butyl Styrene, phenylstyrene, cyclohexylstyrene, benzylstyrene, crotylbenzene, divinylbenzene, divinyltoluene, divinylxylene, trivinylbenzene; and vinylnaphthalene.

  Carboxy group-containing vinyl monomers and metal salts thereof: unsaturated monocarboxylic acids and unsaturated dicarboxylic acids having 3 to 30 carbon atoms, and anhydrides and monoalkyl (1 to 27 carbon atoms) esters thereof. For example, acrylic acid, methacrylic acid, maleic acid, maleic anhydride, monoalkyl maleate, fumaric acid, monoalkyl fumarate, crotonic acid, itaconic acid, monoalkyl itaconate, glycol monoether itaconate, citraconic acid , Carboxy group-containing vinyl monomers of citraconic acid monoalkyl ester and cinnamic acid.

  Vinyl esters, for example, vinyl acetate, vinyl butyrate, vinyl propionate, vinyl butyrate, diallyl phthalate, diallyl adipate, isopropenyl acetate, vinyl methacrylate, methyl 4-vinyl benzoate, cyclohexyl methacrylate, benzyl methacrylate, phenyl acrylate, phenyl methacrylate, Vinyl methoxy acetate, vinyl benzoate, ethyl α-ethoxy acrylate, alkyl acrylate having alkyl group having 1 to 22 carbon atoms (linear or branched) and alkyl methacrylate (methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, propyl acrylate) , Propyl methacrylate, butyl acrylate, butyl methacrylate, 2- Tylhexyl acrylate, 2-ethylhexyl methacrylate, lauryl acrylate, lauryl methacrylate, myristyl acrylate, myristyl methacrylate, cetyl acrylate, cetyl methacrylate, stearyl acrylate, stearyl methacrylate, eicosyl acrylate, eicosyl methacrylate, behenyl acrylate, behenyl methacrylate, etc.), dialkyl fuma Rate (a dialkyl fumarate, two alkyl groups are a linear, branched or alicyclic group having 2 to 8 carbon atoms), dialkyl maleate (a dialkyl maleate, 2 Are straight-chain, branched-chain or alicyclic groups having 2 to 8 carbon atoms), polyallyloxyalkanes (diaryloxyethane, triaryl Roxyethane, tetraallyloxyethane, tetraallyloxypropane, tetraallyloxybutane, tetramethallyloxyethane), vinyl monomers having a polyalkylene glycol chain (polyethylene glycol (molecular weight 300) monoacrylate, polyethylene glycol (molecular weight 300) mono) Methacrylate, polypropylene glycol (molecular weight 500) monoacrylate, polypropylene glycol (molecular weight 500) monomethacrylate, methyl alcohol ethylene oxide (ethylene oxide is abbreviated as EO hereinafter), 10 mol adduct acrylate, 10 mol adduct methyl alcohol ethylene oxide methacrylate Acrylate, 30 mol adduct of lauryl alcohol EO, methacryl adduct of 30 mol lauryl alcohol EO Polyacrylates and polymethacrylates (polyacrylates and polymethacrylates of polyhydric alcohols: ethylene glycol diacrylate, ethylene glycol dimethacrylate, propylene glycol diacrylate, propylene glycol dimethacrylate, neopentyl glycol diacrylate, neo Pentyl glycol dimethacrylate, trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, polyethylene glycol diacrylate, polyethylene glycol dimethacrylate).

  Among these, methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, propyl acrylate, propyl methacrylate, butyl acrylate, butyl methacrylate, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, and the like are preferable.

  Further, a carboxy group-containing vinyl ester: for example, carboxyalkyl acrylate having an alkyl chain having 3 to 20 carbon atoms and carboxyalkyl methacrylate having an alkyl chain having 3 to 20 carbon atoms can also be used.

  Among these, β-carboxyethyl acrylate is preferred.

  The styrene resin may be used alone or in combination of two or more. When two or more types are used in combination, they may be in the form of a chemically bonded composite resin.

  The peak molecular weight of the styrene resin is preferably from 5,000 to 12,000, more preferably from 7000 to 10,000.

  The binder resin may contain a known toner resin in addition to the styrene resin.

  The content of the styrene resin in the binder resin is preferably from 70% by mass to 100% by mass, and more preferably from 85% by mass to 100% by mass.

  The glass transition temperature (Tg) of the binder resin is preferably from 40.0 ° C. to 120.0 ° C. from the viewpoint of fixability.

  Examples of the magnetic substance include iron oxides such as magnetite, maghemite, and ferrite; metals such as iron, cobalt, and nickel; or these metals and aluminum, copper, magnesium, tin, zinc, beryllium, calcium, manganese, selenium, and titanium. , Tungsten, and alloys of metals such as vanadium and mixtures thereof.

  The number average particle diameter of the primary particles of the magnetic material is preferably 0.50 μm or less, more preferably 0.05 μm or more and 0.30 μm or less.

  The number average particle diameter of the primary particles of the magnetic substance present in the toner particles can be measured using a transmission electron microscope.

  Specifically, after sufficiently dispersing the toner particles to be observed in the epoxy resin, the epoxy resin is cured in an atmosphere at a temperature of 40 ° C. for 2 days to obtain a cured product. Using the obtained cured product as a flaky sample with a microtome, an image at a magnification of 10,000 to 40,000 times was taken with a transmission electron microscope (TEM), and 100 primary particles of the magnetic material in the image were taken. Measure the projected area. The equivalent diameter of a circle equal to the projected area is defined as the particle diameter of the primary particles of the magnetic substance, and the average value of the 100 particles is defined as the number average particle diameter of the primary particles of the magnetic substance.

As the magnetic properties of the magnetic material when 795.8 kA / m is applied, the coercive force (Hc) is preferably 1.6 to 12.0 kA / m. Moreover, strength of magnetization ([sigma] s) is preferably 50~200Am ² / kg, more preferably 50~100Am ² / kg. On the other hand, the residual magnetization (σr) is preferably ^{2 to 20} Am ² / kg.

  The content of the magnetic substance in the magnetic toner is preferably from 35% by mass to 50% by mass, more preferably from 40% by mass to 50% by mass.

  When the content of the magnetic material is within the above range, the magnetic attraction with the magnet roll in the developing sleeve becomes appropriate.

  The content of the magnetic substance in the magnetic toner can be measured using a thermal analyzer TGA Q5000IR manufactured by Perkin Elmer. The measuring method is as follows: a magnetic toner is heated from room temperature to 900 ° C. at a temperature rising rate of 25 ° C./min under a nitrogen atmosphere, a weight loss of 100 to 750 ° C. is taken as a mass of a component obtained by removing a magnetic substance from the magnetic toner, and a residual mass is measured. Is the amount of the magnetic material.

  The magnetic material can be manufactured, for example, by the following method.

  An aqueous solution containing ferrous hydroxide is prepared by adding an alkali such as sodium hydroxide in an amount equivalent to or more than the iron component to the aqueous ferrous salt solution. Air is blown in while maintaining the pH of the prepared aqueous solution at 7 or more, and an oxidation reaction of ferrous hydroxide is performed while heating the aqueous solution to 70 ° C. or more, to first generate a seed crystal serving as a core of magnetic iron oxide. .

  Next, an aqueous solution containing about 1 equivalent of ferrous sulfate is added to the slurry liquid containing the seed crystals based on the amount of the alkali previously added. The pH of the mixture is maintained at 5 to 10, the reaction of ferrous hydroxide is advanced while blowing air, and magnetic iron oxide is grown around the seed crystal. At this time, the shape and magnetic properties of the magnetic material can be controlled by selecting an arbitrary pH, reaction temperature, and stirring conditions. As the oxidation reaction proceeds, the pH of the mixed solution shifts to the acidic side, but the pH of the mixed solution is preferably not less than 5. The magnetic material can be obtained by filtering, washing and drying the magnetic material thus obtained by a conventional method.

  The magnetic material may be subjected to a known surface treatment as necessary.

  The magnetic toner particles may contain a charge control agent. The magnetic toner is preferably a negatively chargeable toner.

  As the charge control agent for negative charging, an organic metal complex compound and a chelate compound are effective, and a monoazo metal complex compound; an acetylacetone metal complex compound; a metal complex compound of an aromatic hydroxycarboxylic acid or an aromatic dicarboxylic acid is exemplified. Is done.

  Specific examples of commercially available products include Spiron Black TRH, T-77, T-95 (Hodogaya Chemical Industry Co., Ltd.), BONTRON (registered trademark) S-34, S-44, S-54, E-84, E -88 and E-89 (Orient Chemical Industry Co., Ltd.).

  The charge control agents can be used alone or in combination of two or more.

  From the viewpoint of the charge amount, the content of the charge control agent is preferably from 0.1 to 10.0 parts by mass, and more preferably from 0.1 to 5 parts by mass, per 100 parts by mass of the binder resin. It is more preferable that the amount is not more than 0.0 parts by mass.

  The method for producing the magnetic toner is not particularly limited, and any of a dry production method (for example, a kneading and pulverizing method) and a wet production method (for example, an emulsion aggregation method, a suspension polymerization method, and a solution suspension method) can be used. Good. Among these, it is preferable to use the emulsion aggregation method.

  When the emulsion aggregation method is used, the coefficient of variation of the occupied area ratio of the magnetic substance, the number average diameter of the wax domain, and the like can be easily controlled within the above ranges.

A method for producing toner particles using the emulsion aggregation method will be described with reference to specific examples.
The emulsion aggregation method roughly includes the following four steps.
(A) a step of preparing a fine particle dispersion, (b) an aggregation step of forming aggregated particles, (c) a coalescence step of forming toner particles by fusion and coalescence, and (d) a washing and drying step.

(A) Step of preparing fine particle dispersion The fine particle dispersion is obtained by dispersing fine particles in an aqueous medium.
Examples of the aqueous medium include water such as distilled water and ion-exchanged water, and alcohols. These may be used alone or in combination of two or more.
An auxiliary agent for dispersing the fine particles in the aqueous medium may be used, and examples of the auxiliary agent include a surfactant.
Examples of the surfactant include an anionic surfactant, a cationic surfactant, an amphoteric surfactant, and a nonionic surfactant.

Specifically, anionic surfactants such as alkyl benzene sulfonate, α-olefin sulfonate, phosphate ester; amine salt type such as alkylamine salt, amino alcohol fatty acid derivative, polyamine fatty acid derivative, imidazoline, alkyl Quaternary ammonium salt type cationic surfactants such as trimethylammonium salt, dialkyldimethylammonium salt, alkyldimethylbenzylammonium salt, pyridinium salt, alkylisoquinolinium salt, benzethonium chloride; fatty acid amide derivatives, polyhydric alcohol derivatives And amphoteric surfactants such as alanine, dodecyldi (aminoethyl) glycine, di (octylaminoethyl) glycine and N-alkyl-N, N-dimethylammonium betaine. .
One type of surfactant may be used alone, or two or more types may be used in combination.
The method for preparing the fine particle dispersion can be appropriately selected depending on the type of the dispersoid.

  For example, a method of dispersing the dispersoid using a rotary shearing homogenizer or a general dispersing machine such as a ball mill, a sand mill, and a dyno mill having a medium may be used. In the case of a dispersoid dissolved in an organic solvent, the dispersoid may be dispersed in an aqueous medium using a phase inversion emulsification method. In the phase inversion emulsification method, a material to be dispersed is dissolved in an organic solvent in which the material is soluble to neutralize an organic continuous phase (O phase). Thereafter, by introducing an aqueous medium (W phase), conversion of the resin from W / O to O / W (so-called phase inversion) is performed to form a discontinuous phase, which is dispersed in the aqueous medium into particles. Is the way.

  The solvent used in the phase inversion emulsification method is not particularly limited as long as the solvent dissolves the resin, but it is preferable to use a hydrophobic or amphiphilic organic solvent for the purpose of forming droplets.

  It is also possible to prepare a fine particle dispersion by performing polymerization after forming droplets in an aqueous medium as in emulsion polymerization. Emulsion polymerization is a method in which a precursor of a material to be dispersed, an aqueous medium, and a polymerization initiator are mixed and then stirred or sheared to obtain a fine particle dispersion in which the material is dispersed in an aqueous medium. At this time, an organic solvent or a surfactant may be used as an emulsifying aid. In addition, as a device for stirring or shearing, a general device may be used, and a general disperser such as a rotary shearing homogenizer may be used.

  The number average particle diameter of the dispersoid of the fine particle dispersion is preferably 0.01 μm or more and 1 μm or less from the viewpoint of controlling the aggregation rate and simplifying coalescence. More preferably, it is 0.08 μm or more and 0.8 μm or less, and still more preferably 0.1 μm or more and 0.6 μm or less.

  The dispersoid in the fine particle dispersion is preferably from 5% by mass to 50% by mass, and more preferably from 10% by mass to 40% by mass, based on the total amount of the dispersion, from the viewpoint of controlling the aggregation rate. More preferred.

(B) Aggregation Step After preparing the fine particle dispersion, one kind of fine particle dispersion or two or more kinds of fine particle dispersions are mixed to prepare an aggregated particle dispersion in which aggregated particles obtained by aggregating fine particles are dispersed.
The mixing method is not particularly limited, and mixing can be performed using a general stirrer.
Aggregation is controlled by the temperature, pH, coagulant, etc. of the aggregated particle dispersion, and any method may be used.
Regarding the temperature at which the aggregated particles are formed, the glass transition temperature of the binder resin is preferably −30 ° C. or higher and is lower than the glass transition temperature.

Examples of the aggregating agent include inorganic metal salts and divalent or higher valent metal complexes. When a surfactant is used as an auxiliary agent in the fine particle dispersion, it is also effective to use a surfactant having a reverse polarity. In particular, when a metal complex is used as the aggregating agent, the amount of the surfactant used is reduced, and the charging characteristics are improved. As the inorganic metal salt, for example,
Metal salts such as calcium chloride, calcium nitrate, barium chloride, magnesium chloride, zinc chloride, aluminum chloride, aluminum sulfate, and
Examples thereof include inorganic metal salt polymers such as polyaluminum chloride, polyaluminum hydroxide, and calcium polysulfide.

  As the chelating agent, a water-soluble chelating agent may be used. Specific examples of the chelating agent include, for example, oxycarboxylic acids such as tartaric acid, citric acid, and gluconic acid, iminodiic acid (IDA), nitrilotriacetic acid (NTA), and ethylenediaminetetraacetic acid (EDTA). The addition amount of the chelating agent is, for example, preferably from 0.01 to 5.0 parts by mass, and more preferably from 0.1 to 3.0 parts by mass, per 100 parts by mass of the resin particles. More preferably, there is.

The timing of mixing of the fine particle dispersion is not particularly limited, and the fine particle dispersion may be added and aggregated after once forming the aggregated particle dispersion or during the formation.
By controlling the addition timing of the fine particle dispersion, the structure in the toner can be controlled.
It is preferable to stop the aggregation when the aggregated particles reach the target particle size.

  Termination of aggregation includes dilution, temperature control, pH control, addition of a chelating agent, addition of a surfactant, and the like, and the addition of a chelating agent is preferable from the viewpoint of production. Further, it is more preferable to stop the aggregation by adding a chelating agent and adjusting the pH. When the addition of the chelating agent and the adjustment of the pH are used in combination, it is possible to form toner particles in which the magnetic material is slightly aggregated after the subsequent coalescing step.

(C) Coalescing Step The toner particles are formed by melting and coalescing by heating after forming the aggregated particles.
The heating temperature is preferably equal to or higher than the glass transition temperature of the binder resin.
Further, after the aggregated particles are heated and coalesced, a fine particle dispersant is mixed, and further, (b) a step of forming aggregated particles, and (c) a melting and coalescing step to form toner particles having a core / shell structure. May be.

(D) Washing and drying steps Known washing methods, solid-liquid separation methods, and drying methods may be used, and are not particularly limited.
However, in the washing step, it is preferable to sufficiently perform replacement washing with ion-exchanged water from the viewpoint of chargeability. In the solid-liquid separation step, suction filtration, pressure filtration, or the like is preferably performed from the viewpoint of productivity. In the drying step, freeze drying, flash jet drying, fluidized drying, vibration type fluidized drying, and the like are preferably performed from the viewpoint of productivity.

The magnetic toner contains inorganic fine particles present on the surface of the magnetic toner particles.
Examples of the inorganic fine particles include silica fine particles, titania fine particles, and alumina fine particles, and those obtained by subjecting the surface of these fine particles to a hydrophobic treatment can also be suitably used.

  Further, the inorganic fine particles contain at least one inorganic oxide fine particle selected from the group consisting of silica fine particles, titania fine particles, and alumina fine particles, and 85% by mass or more of the inorganic oxide fine particles are silica fine particles. . Further, it is preferable that 90% by mass or more of the inorganic oxide fine particles are silica fine particles.

  This is because silica particles are not only the most excellent in terms of imparting chargeability and fluidity, but also excellent in reducing the cohesive force between toner particles.

  It is not clear why silica fine particles are excellent in terms of reducing the cohesive force between toner particles, but it is presumed that the above-mentioned bearing effect largely acts on the slipperiness between silica fine particles. are doing.

  On the other hand, the inorganic fine particles fixed on the surface of the magnetic toner particles preferably contain silica fine particles as a main component. Specifically, the inorganic fine particles fixed on the surface of the magnetic toner particles contain at least one inorganic oxide fine particle selected from the group consisting of silica fine particles, titania fine particles, and alumina fine particles. Of the silica fine particles is preferably 80% by mass or more. More preferably, 90% by mass or more is silica fine particles.

  This is presumed to be the same reason as described above, and silica fine particles are the most excellent in terms of imparting chargeability and fluidity, whereby the magnetic toner is quickly charged. As a result, a high image density can be obtained.

Here, in order to make 85% by mass or more of the inorganic oxide fine particles present on the surface of the magnetic toner particles into silica fine particles, and to make 80% by mass or more of the inorganic oxide particles fixed on the surface of the magnetic toner particles into the silica fine particles. The amount and timing of the addition of the inorganic fine particles may be adjusted.
Further, the amount of the inorganic fine particles can be confirmed by a method for quantifying the inorganic fine particles described below.

  The number average particle diameter of the primary particles of the inorganic fine particles is preferably from 5 nm to 50 nm, more preferably from 10 nm to 35 nm.

  When the number average particle size of the primary particles of the inorganic fine particles is in the above range, the coverage A, B / A, and the variation coefficient of the coverage A can be easily controlled to the appropriate ranges, and the above-described adhesive force reduction and bearing The effect is easily obtained.

  The inorganic fine particles are preferably subjected to a hydrophobic treatment, and are subjected to a hydrophobic treatment so that the degree of hydrophobicity measured by a methanol titration test is 40% or more, more preferably 50% or more. It is.

  Examples of the method of the hydrophobizing treatment include a method of treating with an organosilicon compound, silicone oil, a long-chain fatty acid, or the like.

  Examples of the organosilicon compound include hexamethyldisilazane, trimethylsilane, trimethylethoxysilane, isobutyltrimethoxysilane, trimethylchlorosilane, dimethyldichlorosilane, methyltrichlorosilane, dimethylethoxysilane, dimethyldimethoxysilane, diphenyldiethoxysilane, and hexamethyl Disiloxane and the like. These are used in one kind or in a mixture of two or more kinds.

  Examples of the silicone oil include dimethyl silicone oil, methylphenyl silicone oil, α-methylstyrene-modified silicone oil, chlorophenyl silicone oil, and fluorine-modified silicone oil.

  As the long-chain fatty acid, a fatty acid having 10 to 22 carbon atoms can be suitably used, and may be a straight-chain fatty acid or a branched fatty acid. Further, both saturated fatty acids and unsaturated fatty acids can be used.

  Among them, straight-chain saturated fatty acids having 10 to 22 carbon atoms are preferable because they can easily treat the surface of the inorganic fine particles uniformly.

  Examples of the linear saturated fatty acid include capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, arachidic acid, and behenic acid.

  Among the inorganic fine particles, those obtained by treating silica fine particles with silicone oil are preferable, and those obtained by treating silica fine particles with an organosilicon compound and silicone oil are preferable because the degree of hydrophobicity can be suitably controlled.

  As a method of treating silica fine particles with silicone oil, for example, a method of directly mixing inorganic fine particles treated with an organosilicon compound and silicone oil using a mixer such as an FM mixer, or spraying silicone oil on inorganic fine particles Method. Alternatively, a method of dissolving or dispersing a silicone oil in a suitable solvent, adding inorganic fine particles, mixing, and removing the solvent may be used.

  In order to obtain good hydrophobicity, the treatment amount of the silicone oil is preferably from 1 part by mass to 40 parts by mass, and more preferably from 3 parts by mass to 35 parts by mass with respect to 100 parts by mass of the silica fine particles. Is more preferred.

From the viewpoint of imparting good fluidity to the magnetic toner, the specific surface area (BET specific surface area) of the inorganic fine particles measured by a BET method by nitrogen adsorption is preferably from 20 m ² / g to 350 m ² / g. . More preferably, it is 25 m ² / g or more and 300 m ² / g or less.

  The specific surface area (BET specific surface area) measured by the BET method by nitrogen adsorption may be measured according to JIS Z8830 (2001).

  As the measuring device, an "automatic specific surface area / pore distribution measuring device TriStar 3000 (manufactured by Shimadzu Corporation)" employing a gas adsorption method by a constant volume method as a measuring method is used.

  Here, the addition amount of the silica fine particles is preferably 1.5 parts by mass or more and 3.0 parts by mass or less based on 100 parts by mass of the magnetic toner particles. More preferably, it is 1.5 parts by mass to 2.6 parts by mass, and still more preferably 1.8 parts by mass to 2.6 parts by mass.

  When the addition amount of the silica fine particles is within the above range, the coverage A and B / A can be easily controlled appropriately, and it is also preferable in terms of image density and fog.

  As a mixing apparatus for externally adding and mixing the inorganic fine particles, a known mixing apparatus can be used. However, the coating rate A, B / A, and the coefficient of variation of the coating rate A can be easily controlled. An apparatus as shown in (a) is preferred.

  FIG. 3A is a schematic diagram illustrating an example of a mixing apparatus that can be used when externally adding and mixing inorganic fine particles.

  Since the mixing apparatus has a configuration in which the magnetic toner particles and the inorganic fine particles are shared in the narrow clearance portion, the inorganic fine particles are easily fixed to the surface of the magnetic toner particles.

  Further, as will be described later, the coverage ratios A, B / A, and the coverage ratio are such that the magnetic toner particles and the inorganic fine particles are likely to circulate in the axial direction of the rotating body and to be sufficiently uniformly mixed before fixation proceeds. It is easy to control the variation coefficient of A within the above range.

  On the other hand, FIG. 3B is a schematic diagram illustrating an example of a configuration of a stirring member used in the mixing apparatus.

  Hereinafter, the step of externally adding and mixing the inorganic fine particles will be described with reference to FIGS. 3 (a) and 3 (b).

  A mixing apparatus for externally adding and mixing inorganic fine particles is provided with a rotating body 2 on which at least a plurality of stirring members 3 are installed on the surface, a driving unit 8 for rotating the rotating body, and a gap with the stirring member 3. Main body casing 1 provided.

  The gap (clearance) between the inner peripheral portion of the main body casing 1 and the stirring member 3 is kept constant and small so as to give a uniform share to the magnetic toner particles and to easily fix the inorganic fine particles on the surface of the magnetic toner particles. Good.

  In this device, the diameter of the inner peripheral portion of the main body casing 1 is twice or less the diameter of the outer peripheral portion of the rotating body 2. In FIG. 3A, an example in which the diameter of the inner peripheral portion of the main body casing 1 is 1.7 times the diameter of the outer peripheral portion of the rotating body 2 (the diameter of the body portion excluding the stirring member 3 from the rotating body 2). Is shown. When the diameter of the inner peripheral portion of the main body casing 1 is not more than twice the diameter of the outer peripheral portion of the rotating body 2, the processing space in which force acts on the magnetic toner particles is appropriately limited, so that the magnetic toner particles have a sufficient diameter. Impact force is applied to

  Further, the clearance may be adjusted according to the size of the main body casing. When the diameter of the inner peripheral portion of the main casing 1 is about 1% or more and 5% or less, a sufficient share can be applied to the magnetic toner particles. Specifically, when the diameter of the inner peripheral part of the main casing 1 is about 130 mm, the clearance is set to about 2 mm or more and about 5 mm or less. When the diameter of the inner peripheral part of the main casing 1 is about 800 mm, the clearance is 10 mm or more and 30 mm or less. It should be about the degree.

  In the externally adding and mixing step of the inorganic fine particles, the mixing unit is used to rotate the rotating body 2 by the drive unit 8 to stir and mix the magnetic toner particles and the inorganic fine particles put into the mixing processing unit. The surface of the particles is externally mixed with inorganic fine particles.

  As shown in FIG. 3 (b), at least a part of the plurality of stirring members 3 sends the magnetic toner particles and the inorganic fine particles in one axial direction of the rotating body with the rotation of the rotating body 2. It is formed as a member 3a. Further, at least a part of the plurality of stirring members 3 is formed as a return stirring member 3b for returning the magnetic toner particles and the inorganic fine particles to the other direction in the axial direction of the rotating body with the rotation of the rotating body 2. .

  Here, as shown in FIG. 3A, when the raw material inlet 5 and the product outlet 6 are provided at both ends of the main body casing 1, a direction from the raw material inlet 5 to the product outlet 6 ( 3A) is referred to as a “feed direction”.

  That is, as shown in FIG. 3B, the plate surface of the feed stirring member 3a is inclined so as to feed the magnetic toner particles in the feed direction (13). On the other hand, the plate surface of the stirring member 3b is inclined so as to send the magnetic toner particles and the inorganic fine particles in the return direction (12).

  Thus, the external addition and mixing process of the inorganic fine particles is performed on the surface of the magnetic toner particles while repeatedly performing the feed (13) in the “feed direction” and the feed (12) in the “return direction”.

  The stirring members 3a and 3b are a set of a plurality of members arranged at intervals in the circumferential direction of the rotating body 2. In the example shown in FIG. 3B, the stirring members 3a and 3b form a set of two members at an interval of 180 degrees with respect to the rotating body 2, but three members at an interval of 120 degrees or 90 degrees. A large number of members may be formed as one set, such as four sheets at intervals of.

  In the example shown in FIG. 3B, a total of 12 stirring members 3a and 3b are formed at equal intervals. Further, in FIG. 3B, D indicates the width of the stirring member, and d indicates the interval indicating the overlapping portion of the stirring member. From the viewpoint of efficiently sending the magnetic toner particles and the inorganic fine particles in the feed direction and the return direction, the width D is about 20% or more and about 30% or less with respect to the length of the rotating body 2 in FIG. Is preferred. FIG. 3B shows an example of 23%. Furthermore, when the stirring members 3a and 3b are vertically extended from the end positions of the stirring members 3a, it is preferable that the stirring members 3a and 3b have an overlapping portion d of the stirring members 3b and 3a to some extent. Thereby, it is possible to efficiently share the magnetic toner particles and the inorganic fine particles. It is preferable that d with respect to D be 10% or more and 30% or less in terms of applying a share.

  Regarding the shape of the blade, the magnetic toner particles and the inorganic fine particles can be sent in the sending direction and the returning direction other than the shape shown in FIG. As long as the clearance can be maintained, a paddle structure in which a shape having a curved surface or a tip blade portion is connected to the rotating body 2 by a rod-shaped arm may be used.

Hereinafter, a more detailed description will be given with reference to the schematic views of the apparatus shown in FIGS. 3 (a) and 3 (b). The apparatus shown in FIG. 3A includes a rotating body 2 on which at least a plurality of stirring members 3 are installed,
A driving unit 8 that rotationally drives the rotating body 2,
A main body casing 1 provided with a gap with the stirring member 3,
A jacket 4 on the inside of the main body casing 1 and on the side surface 10 of the end of the rotating body through which a cooling medium can flow.
have.

Further, the device shown in FIG.
In order to introduce magnetic toner particles and inorganic fine particles, a raw material inlet 5 formed in the upper part of the main body casing 1 and a lower part of the main body casing 1 in order to discharge the externally mixed magnetic toner from the main body casing 1 to the outside. Product outlet 6 formed in
have.

  Further, in the apparatus shown in FIG. 3A, a raw material inlet inner piece 16 is inserted into the raw material inlet 5, and a product outlet inner piece 17 is inserted into the product outlet 6. I have.

  First, the inner piece 16 for the raw material inlet is taken out from the raw material inlet 5 and the magnetic toner particles are injected into the processing space 9 from the raw material inlet 5. Next, the inorganic fine particles are charged into the processing space 9 from the raw material inlet 5, and the inner piece 16 for the raw material inlet is inserted. Next, the rotator 2 is rotated by the drive unit 8 (11 indicates the direction of rotation), and the magnetic toner particles and the inorganic fine particles input above are stirred by the plurality of stirring members 3 provided on the surface of the rotator 2. And externally mixing while mixing.

  The order of charging may be such that the inorganic fine particles are charged first through the raw material charging port 5 and then the magnetic toner particles are charged through the raw material charging port 5. Alternatively, after mixing the magnetic toner particles and the inorganic fine particles in advance with a mixer such as a Henschel mixer, the mixture may be charged from the raw material charging port 5 of the apparatus shown in FIG.

  More specifically, controlling the power of the driving unit 8 to be 0.2 W / g or more and 2.0 W / g or less as the external addition and mixing processing conditions is equivalent to the coverage A, the B / A, and the coverage A. Is preferable from the viewpoint of adjusting the variation coefficient of the above to the above range. Further, it is more preferable to control the power of the driving unit 8 to be 0.6 W / g or more and 1.6 W / g or less.

  The processing time is not particularly limited, but is preferably 3 minutes or more and 10 minutes or less.

The number of rotations of the stirring member at the time of external mixing is not particularly limited. In the apparatus shown in FIG. 3A in which the volume of the processing space 9 is 2.0 × 10 ⁻³ m ³ , the rotation speed of the stirring member 3 when the shape of the stirring member 3 is that of FIG. Is preferably 1000 rpm or more and 3000 rpm or less. By adjusting the number of rotations in this range, the coverage A, B / A, and the variation coefficient of the coverage A can be easily adjusted to the above ranges.

  Further, a pre-mixing step may be provided before the external addition mixing operation. By including the pre-mixing step, the inorganic fine particles are highly uniformly dispersed on the surface of the magnetic toner particles, so that the coverage A can be adjusted higher and the variation coefficient of the coverage A can be more easily reduced.

  More specifically, as the pre-mixing processing conditions, the power of the driving unit 8 is set to 0.06 W / g or more and 0.20 W / g or less, and the processing time is set to 0.5 minutes or more and 1.5 minutes or less. preferable.

  After completion of the external additive mixing process, the inner piece 17 for the product discharge port in the product discharge port 6 is taken out, and the rotating body 2 is rotated by the drive unit 8 to discharge the magnetic toner from the product discharge port 6. It is preferable to separate the obtained magnetic toner with a sieve such as a circular vibrating sieve if necessary to obtain a magnetic toner.

  Particles having a number average particle diameter of primary particles of 80 nm or more and 3 μm or less may be added to the magnetic toner in addition to the inorganic fine particles as long as the effects of the present invention are not affected. Examples of the particles include lubricants such as fluororesin powder, zinc stearate powder, and polyvinylidene fluoride powder; and abrasives such as cerium oxide powder, silicon carbide powder, and strontium titanate powder.

  The volume average particle diameter (Dv) of the magnetic toner is preferably 3.0 μm or more and 8.0 μm or less, more preferably 5.0 μm or more and 7.0 μm or less.

  When the volume average particle diameter (Dv) of the toner is in the above range, it is possible to sufficiently satisfy the dot reproducibility while improving the handleability of the toner.

  The ratio (volume average particle diameter / number average particle diameter) of the volume average particle diameter (Dv) to the number average particle diameter of the magnetic toner is preferably less than 1.25.

  The average circularity of the magnetic toner is preferably 0.960 or more and 1.000 or less, more preferably 0.970 or more and 1.000 or less.

  When the average circularity is in the above range, even in a system having a high share such as a one-component contact developing system, the toner is hardly densified, and the fluidity of the toner is easily maintained. As a result, when outputting a large number of images, it is possible to further suppress the reduction in image density and the occurrence of development streaks in the latter half.

  The average circularity may be controlled by a commonly used method during the production of the toner. For example, in the case of the emulsion aggregation method, the time of the coalescing step and the amount of the surfactant added may be controlled.

The image forming method of the present invention comprises:
A charging step of applying a voltage to the charging member from outside to charge the electrostatic latent image carrier,
A latent image forming step of forming an electrostatic latent image on the charged electrostatic latent image carrier,
A developing step of developing the electrostatic latent image with a toner carried on a toner carrier to form a toner image on the electrostatic latent image carrier;
A transfer step of transferring the toner image on the electrostatic latent image carrier to a transfer material with or without an intermediate transfer member, and
An image forming method including a fixing step of fixing a toner image transferred to a transfer material by heating and pressing means,
The developing step is a one-component contact developing method in which the electrostatic latent image carrier and the toner carried on the toner carrier are directly contacted to perform development,
The toner is
A magnetic toner containing a binder resin, a magnetic toner particle containing a magnetic substance and a wax, and inorganic fine particles present on the surface of the magnetic toner particle,
In the cross section of the magnetic toner using a transmission electron microscope,
A coefficient of variation CV3 of the occupied area ratio of the magnetic material when the cross section of the magnetic toner is divided by a square grid having a side of 0.8 μm is 40.0% or more and 80.0% or less;
The inorganic fine particles contain at least one inorganic oxide fine particle selected from the group consisting of silica fine particles, titania fine particles, and alumina fine particles, and 85% by mass or more of the inorganic oxide fine particles are silica fine particles,
Assuming that the coverage of the surface of the magnetic toner particles with the inorganic fine particles is coverage A (%), the coverage A is 45.0% or more and 80.0% or less;
The wax forms a domain inside the magnetic toner particles, and the number average diameter of the domain is 100 nm or more and 500 nm or less,
The binder resin contains a styrene resin,
The peak molecular weight of the main peak, as measured by gel permeation chromatography of a tetrahydrofuran-soluble component of the magnetic toner, is 5,000 or more and 12,000 or less.

  The one-component contact developing method is a developing method in which a toner carrier and an electrostatic latent image carrier are arranged in contact (contact arrangement), and these carriers rotate to convey toner. A large share is applied to the contact portion between the toner carrier and the electrostatic latent image carrier. Therefore, in order to obtain a high-quality image, the toner preferably has high durability and high fluidity.

  On the other hand, the one-component developing system can reduce the size of the cartridge in which the developer is stored, as compared with the two-component developing system using a carrier.

  In addition, the contact developing system can obtain a high quality image with less scattering of toner. That is, the one-component contact developing system having both of them can achieve both the miniaturization of the developing device and the improvement of image quality.

  Hereinafter, the one-component contact developing method will be described in detail with reference to the drawings.

  FIG. 1 is a schematic sectional view showing an example of the developing device. FIG. 2 is a schematic sectional view showing an example of an image forming apparatus of a one-component contact developing system.

  1 or 2, the electrostatic latent image carrier 45 on which the electrostatic latent image is formed is rotated in the direction of arrow R1. By rotating the toner carrier 47 in the direction of arrow R2, the toner 57 is transported to a development area where the toner carrier 47 and the electrostatic latent image carrier 45 face each other. A toner supply member 48 is in contact with the toner carrier 47, and supplies toner 57 to the surface of the toner carrier 47 by rotating in the direction of arrow R3. Further, the toner 57 is stirred by the stirring member 58.

  Around the electrostatic latent image carrier 45, a charging member (charging roller) 46, a transfer member (transfer roller) 50, a cleaner container 43, a cleaning blade 44, a fixing device 51, a pickup roller 52, and the like are provided. The electrostatic latent image carrier 45 is charged by a charging roller 46. Then, exposure is performed by irradiating the electrostatic latent image carrier 45 with laser light by the laser generator 54, and an electrostatic latent image corresponding to a target image is formed. The electrostatic latent image on the electrostatic latent image carrier 45 is developed with the toner 57 in the developing device 49 to obtain a toner image. The toner image is transferred onto a transfer material (paper) 53 by a transfer member (transfer roller) 50 in contact with the electrostatic latent image carrier 45 via the transfer material. The transfer of the toner image to the transfer material may be performed via an intermediate transfer member. The transfer material (paper) 53 carrying the toner image is carried to the fixing device 51 and fixed on the transfer material (paper) 53. The toner 57 partially left on the electrostatic latent image carrier 45 is scraped off by the cleaning blade 44 and stored in the cleaner container 43.

  Further, it is preferable that the toner regulating member (reference numeral 55 in FIG. 1) contacts the toner carrier via the toner to regulate the thickness of the toner layer on the toner carrier. This makes it possible to obtain high image quality without any regulation failure. A regulating blade is generally used as a toner regulating member that contacts the toner carrier.

  The base on the upper side of the regulating blade is fixedly held on the developing device side, and the lower side is bent in the forward or reverse direction of the toner carrier against the elastic force of the blade, and the surface of the toner carrier is It is good to make contact with a suitable elastic pressing force.

  For example, to fix the toner regulating member 55 to the developing device, as shown in FIG. 1, one free end of the toner regulating member 55 is sandwiched between two fixing members (for example, a metal elastic body, reference numeral 56 in FIG. 1), and a screw is formed. It is good to fix with a clasp.

  Hereinafter, the method for measuring each physical property value according to the present invention will be described.

<Quantitative method of inorganic fine particles>
(1) Determination of silica content in magnetic toner (standard addition method)
3 g of the magnetic toner is placed in an aluminum ring having a diameter of 30 mm, and a pellet is produced under a pressure of 10 tons. Then, the intensity of silicon (Si) is obtained by wavelength-dispersive X-ray fluorescence analysis (XRF) (Si intensity-1). Note that the measurement conditions may be those optimized for the XRF device to be used, but a series of intensity measurements are all performed under the same conditions. Silica fine particles having a primary particle number average particle diameter of 12 nm are added to the magnetic toner by 1.0% by mass based on the magnetic toner, and mixed by a coffee mill.

  At this time, as long as the silica fine particles to be mixed have a number average particle diameter of the primary particles of 5 nm or more and 50 nm or less, the silica fine particles can be used without affecting the quantitative determination.

  After mixing, pelletization is performed in the same manner as described above, and the strength of Si is determined in the same manner as described above (Si strength-2). The same operation is performed to determine the strength of Si (Si strength-3, Si strength-4) also in a sample in which silica fine particles are added and mixed at 2.0% by mass and 3.0% by mass with respect to the magnetic toner. The silica content (% by mass) in the magnetic toner is calculated by the standard addition method using the Si strength-1 to the Si strength-4.

  The titania content (% by mass) and the alumina content (% by mass) in the magnetic toner are determined by the standard addition method in the same manner as the above-described determination of the silica content. That is, the titania content (% by mass) can be quantified by adding and mixing titania fine particles having a number average particle diameter of primary particles of 5 nm or more and 50 nm or less and determining the titanium (Ti) strength. The alumina content (% by mass) can be quantified by adding and mixing alumina fine particles having a number average particle diameter of primary particles of 5 nm or more and 50 nm or less, and determining the aluminum (Al) strength.

(2) Separation of Inorganic Fine Particles from Magnetic Toner 5 g of magnetic toner is weighed into a 200 mL polycup with a lid using a precision balance, 100 mL of methanol is added, and the mixture is dispersed with an ultrasonic disperser for 5 minutes. The magnetic toner is attracted by the neodymium magnet, and the supernatant is discarded. The operation of dispersing in methanol and discarding the supernatant is repeated three times. Thereafter, 100 mL of 10% NaOH and 10% by mass aqueous solution of "Contaminone N" (a neutral detergent for cleaning a precision measuring instrument composed of a nonionic surfactant, an anionic surfactant and an organic builder having a pH of 7 and comprising Wako Pure Chemical Industries, Ltd.) (Manufactured by Kogyo Co., Ltd.) and mix gently. Then, it is left still for 24 hours. Thereafter, separation is again performed using a neodymium magnet. In this case, rinse with distilled water repeatedly so that NaOH does not remain. The collected particles are sufficiently dried by a vacuum dryer to obtain particles A. By the above operation, the externally added silica fine particles are dissolved and removed. Since titania fine particles and alumina fine particles are hardly soluble in 10% NaOH, they may remain in the particles A.

(3) Measurement of Si intensity in particles A 3 g of particles A were placed in an aluminum ring having a diameter of 30 mm, pellets were produced at a pressure of 10 tons, and the intensity of Si was determined by wavelength dispersive X-ray fluorescence analysis (XRF). (Si strength-5). The silica content (% by mass) in the particle A is calculated using the Si intensity-5 and the Si intensity-1 to Si intensity-4 used in the determination of the silica content in the magnetic toner.

(4) Separation of the magnetic substance from the magnetic toner 100 mL of tetrahydrofuran is added to 5 g of the particles A, and after mixing well, ultrasonic dispersion is performed for 10 minutes. The magnetic particles are attracted by the magnet and the supernatant is discarded. This operation is repeated five times to obtain particles B. By this operation, organic components such as resin other than the magnetic substance can be almost removed. However, since there is a possibility that the tetrahydrofuran insoluble content in the resin may remain, it is preferable to heat the particles B obtained by the above operation to 800 ° C. to burn the remaining organic components, and to obtain the particles C obtained after heating. Can be approximated to the magnetic substance contained in the magnetic toner.

By measuring the mass of the particles C, the magnetic substance content W (% by mass) in the magnetic toner can be determined. At this time, the mass of the particle C is multiplied by 0.9666 (Fe ₂ O ₃ → Fe ₃ O ₄ ) in order to correct the increased amount of oxidation of the magnetic material.

(5) Measurement of Ti intensity and Al intensity in the separated magnetic material Ti and Al may be contained in the magnetic material as impurities or additives. The amounts of Ti and Al caused by the magnetic substance can be detected by the FP quantification method of wavelength dispersive X-ray fluorescence spectrometry (XRF). The content of titania and alumina in the magnetic material is calculated by converting the detected Ti content and Al content into titania and alumina.

  By substituting each quantitative value obtained by the above method into the following equation, the amount of externally added silica fine particles, the amount of externally added titania fine particles, and the amount of externally added alumina fine particles are calculated.

Externally added silica fine particle amount (% by mass) = silica content in magnetic toner (% by mass) −silica content in particle A (% by mass)
Amount of externally added titania fine particles (% by mass) = Titania content in magnetic toner (% by mass) − {Titania content of magnetic material (% by mass) × magnetic material content W / 100}
Amount of externally added alumina fine particles (% by mass) = Alumina content in magnetic toner (% by mass) − {Alumina content of magnetic material (% by mass) × magnetic material content W / 100}
(6) Calculation of the ratio of the silica fine particles in the inorganic oxide fine particles selected from the group consisting of silica fine particles, titania fine particles, and alumina fine particles in the inorganic fine particles fixed on the surface of the magnetic toner particles.

  In the below-described method of calculating the coverage B, the same operation as in the above methods (1) to (5) is performed after drying the toner after performing the operation of “removing inorganic fine particles that are not fixed”. Thereby, the ratio of the silica fine particles in the inorganic oxide fine particles can be calculated.

<Method of Measuring Volume Average Particle Size (Dv) and Number Average Particle Size (Dn) of Magnetic Toner>
The volume average particle diameter (Dv) and number average particle diameter (Dn) of the magnetic toner are calculated as follows.

  As a measuring device, a precise particle size distribution measuring device “Coulter Counter Multisizer 3” (registered trademark, manufactured by Beckman Coulter, Inc.) equipped with a 100 μm aperture tube by a pore electric resistance method is used. For setting the measurement conditions and analyzing the measurement data, the attached dedicated software “Beckman Coulter Multisizer 3 Version 3.51” (manufactured by Beckman Coulter) is used. The measurement is performed with 25,000 effective measurement channels.

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

  Before performing the measurement and analysis, the dedicated software is set as follows.

  In the “Change standard measurement method (SOM) screen” of the dedicated software, the total count number in the control mode is set to 50,000 particles, the number of measurements is set to 1, and the Kd value is “standard particles 10.0 μm” (Beckman Coulter, Inc.) Set the value obtained using By pressing the “threshold / noise level measurement button”, the threshold and the noise level are automatically set. Also, the current is set to 1600 μA, the gain is set to 2, and the electrolytic aqueous solution is set to ISOTON II, and a check is made in “Flush aperture tube after measurement”.

  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 from 2 μm to 60 μm.

  The specific measuring method is as follows.

  (1) About 200 mL of the aqueous electrolytic solution is placed in a glass 250 mL round bottom beaker dedicated to Multisizer 3, set on a sample stand, and the stirrer rod is stirred counterclockwise at 24 revolutions / second. Then, the dirt and air bubbles in the aperture tube are removed by the “flash aperture tube” function of the dedicated software.

  (2) About 30 mL of the electrolytic aqueous solution is placed in a 100 mL flat bottom glass beaker. A 10% by mass aqueous solution of a neutral detergent for cleaning a precision measuring instrument having a pH of 7 comprising a nonionic surfactant, an anionic surfactant, and an organic builder as a dispersant is used as a dispersant therein, manufactured by Wako Pure Chemical Industries, Ltd. ) Was diluted about 3 times by mass with ion-exchanged water, and about 0.3 mL of a diluent was added.

  (3) An ultrasonic disperser “Ultrasonic Dispersion System Tetra 150” (manufactured by Nikkaki Bios Co., Ltd.) having two oscillators having an oscillation frequency of 50 kHz and having a phase shifted by 180 ° and having an electrical output of 120 W is prepared. About 3.3 L of ion-exchanged water is put into the water tank of the ultrasonic disperser, and about 2 mL of 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. Then, the height position of the beaker is adjusted so that the state of resonance of the electrolytic solution in the beaker becomes maximum.

  (5) About 10 mg of the toner is added little by little to the aqueous electrolytic solution in the beaker of the above (4) in a state where the aqueous electrolytic solution is irradiated with ultrasonic waves, and dispersed. Then, the ultrasonic dispersion processing is continued for another 60 seconds. In addition, about ultrasonic dispersion, it adjusts suitably so that the water temperature of a water tank may be set to 10 to 40 degreeC.

  (6) The electrolytic aqueous solution of (5) in which the toner is dispersed is dropped into the round bottom beaker of (1) installed in the sample stand using a pipette, and the measured concentration is adjusted to about 5%. . Then, measurement is performed until the number of particles to be measured reaches 50,000.

  (7) The measurement data is analyzed by the dedicated software attached to the apparatus, and the volume average particle diameter (Dv) and the number average particle diameter (Dn) are calculated. The “50% D diameter” on the “analysis / volume statistics (arithmetic average)” screen when the graph / volume% was set by the dedicated software was defined as the volume average particle diameter (Dv). The “arithmetic diameter” on the “analysis / number statistical value (arithmetic average)” screen when the graph / number% was set by the dedicated software was defined as the number average particle diameter (Dn).

<Method of Measuring Average Luminance, Luminance Dispersion Value, Coefficient of Variation, and Average Circularity of Magnetic Toner>
The average brightness, the brightness variance, the variation coefficient, and the average circularity of the magnetic toner are measured using a flow-type particle image measurement device “FPIA-3000” (manufactured by Sysmex Corporation) under the measurement and analysis conditions during the calibration work.

  The specific measuring method is as follows.

  First, about 20 mL of ion-exchanged water from which impurity solids and the like have been removed in advance is placed in a glass container. A 10% by mass aqueous solution of a neutral detergent for cleaning a precision measuring instrument having a pH of 7 comprising a nonionic surfactant, an anionic surfactant, and an organic builder as a dispersant is used as a dispersant therein, manufactured by Wako Pure Chemical Industries, Ltd. ) Was diluted about 3 times by mass with ion-exchanged water, and about 0.2 mL of a diluent was added. Further, about 0.02 g of a measurement sample is added, and a dispersion treatment is performed for 2 minutes using an ultrasonic disperser to obtain a dispersion for measurement. At that time, the dispersion is appropriately cooled so that the temperature of the dispersion is 10 ° C. or more and 40 ° C. or less. As the ultrasonic disperser, a desktop ultrasonic cleaner “VS-150” (manufactured by Vervocreer) having an oscillation frequency of 50 kHz and an electric output of 150 W was used, and a predetermined amount of ion-exchanged water was put in the water tank. Then, about 2 mL of the contaminone N is added to the water tank.

  For the measurement, the above-mentioned flow type particle image measuring apparatus equipped with "LUCPFLN" (magnification: 20 times, numerical aperture: 0.40) as an objective lens was used, and a particle sheath "PSE-900A" (manufactured by Sysmex Corporation) was used as a sheath liquid. Use The dispersion prepared according to the above procedure is introduced into the flow type particle image measuring device, and 2,000 magnetic toners are measured in an HPF measurement mode and a total count mode. From the result, the average brightness, the brightness variance, the variation coefficient, and the average circularity of the magnetic toner are calculated.

  The average brightness at Dn of the magnetic toner is determined by setting the equivalent circle diameter of the present flow type particle image analyzer to Dn−0.500 (μm) or more with respect to the result of the number average particle diameter (Dn) of the magnetic toner. It is a value obtained by limiting the range to 500 (μm) or less and calculating the average luminance.

  CV1 indicates that the circle equivalent diameter of the present flow type particle image measuring device is Dn−0.500 (μm) or more with respect to the result of the number average particle diameter (Dn) of the magnetic toner in the measurement result of the luminance dispersion value. Dn + 0.500 (μm) or less. It is a value obtained by calculating the variation coefficient of the luminance variance value.

  CV2 indicates that the circle equivalent diameter of the present flow type particle image measuring device is Dn-1.500 (μm) or more with respect to the result of the number average particle diameter (Dn) of the magnetic toner in the measurement result of the luminance dispersion value. Dn-0.500 (μm) or less. It is a value obtained by calculating the variation coefficient of the luminance variance value.

  In the measurement, automatic focusing is performed using standard latex particles ("RESEARCH AND TEST PARTICLES Latex Microsphere Suspensions 5100A" manufactured by Duke Scientific) diluted with ion-exchanged water before the start of the measurement. Thereafter, it is preferable to perform the focus adjustment every two hours from the start of the measurement.

  In this case, a flow type particle image analyzer that has been calibrated by Sysmex Corporation and has been issued a calibration certificate issued by Sysmex Corporation will be used.

  Except that the analysis particle diameter is limited to the circle equivalent diameter of 1.977 μm or more and less than 39.54 μm, the measurement is performed under the measurement and analysis conditions when the calibration certificate is received.

<Measurement method of melting point>
The melting point of the resin or wax is measured using a differential scanning calorimeter (DSC) Q2000 (manufactured by TA Instruments) under the following conditions.

Heating rate: 10 ° C / min
Measurement start temperature: 20 ° C
Measurement end temperature: 180 ° C
The temperature correction of the device detection unit uses the melting points of indium and zinc, and the heat quantity correction uses the heat of fusion of indium.

  Specifically, about 5 mg of a sample is precisely weighed, placed in an aluminum pan, and measured once. An empty pan made of aluminum is used as a reference. The peak temperature of the maximum endothermic peak at that time is defined as the melting point.

<Method of measuring glass transition temperature (Tg)>
The glass transition temperature of the resin, etc., in the reversing heat flow curve at the time of temperature increase obtained by the differential scanning calorimetry of the melting point, the vertical axis direction from a straight line extending the baseline before and after the specific heat change appears Is the temperature (° C.) at the point where the straight line at the same distance and the curve of the step change portion of the glass transition in the reversing heat flow curve intersect.

<Method of measuring number average molecular weight (Mn), weight average molecular weight (Mw), and peak molecular weight (Mp) of resin and the like>
The number average molecular weight (Mn), the weight average molecular weight (Mw), and the peak molecular weight (Mp) of the resin and other materials are measured using gel permeation chromatography (GPC) as follows.

(1) Preparation of measurement sample A sample and tetrahydrofuran (THF) were mixed at a concentration of 5.0 mg / mL, allowed to stand at room temperature for 5 to 6 hours, shaken sufficiently, and THF and the sample were removed. Mix well until there is no more unity. Furthermore, it is left still at room temperature for 12 hours or more. At this time, the time from the start of the mixing of the sample and THF to the end of the standing is set to be 72 hours or more, and a tetrahydrofuran (THF) soluble content of the sample is obtained.

  Then, the sample solution is obtained by filtration through a solvent-resistant membrane filter (pore size: 0.45 to 0.50 μm, Meishori Disc H-25-2 [manufactured by Tosoh Corporation]).

(2) Measurement of sample The sample solution is measured under the following conditions.

Equipment: High-speed GPC equipment LC-GPC 150C (manufactured by Waters)
Column: Seven columns of Shodex GPC KF-801, 802, 803, 804, 805, 806, 807 (manufactured by Showa Denko KK) Mobile phase: THF
Flow rate: 1.0 mL / min
Column temperature: 40 ° C
Sample injection volume: 100 μL
Detector: RI (Refractive Index) Detector In measuring the molecular weight of a sample, the molecular weight distribution of the sample is calculated from the relationship between the logarithmic value of a calibration curve prepared from several monodisperse polystyrene standard samples and the count number.

As a standard polystyrene sample for preparing a calibration curve, Pressure Chemical Co. Or Toyo Soda Kogyo Co., Ltd. having a molecular weight of 6.0 × 10 ² , 2.1 × 10 ³ , 4.0 × 10 ³ , 1.75 × 10 ⁴ , 5.1 × 10 ⁴ , 1.1 × 10 ⁵ , 3.9 × 10 ⁵ , 8.6 × 10 ⁵ , 2.0 × 10 ⁶ , and 4.48 × 10 ⁶ are used. Note that the peak molecular weight of the main peak means that the largest peak in the obtained molecular weight distribution is the main peak.

<Method for Measuring Particle Size of Dispersion in Fine Particle Dispersion>
The particle size of the dispersion of each fine particle dispersion is measured using a laser diffraction / scattering type particle size distribution analyzer. Specifically, it is measured according to JIS Z8825-1 (2001).

  As a measuring device, a laser diffraction / scattering type particle size distribution measuring device “LA-920” (manufactured by Horiba, Ltd.) is used.

  The setting of the measurement conditions and the analysis of the measurement data use dedicated software “HORIBA LA-920 for Windows (registered trademark) WET (LA-920) Ver. 2.02” attached to the LA-920. In addition, as the measurement solvent, ion-exchanged water from which impurity solids and the like have been removed in advance is used. The measurement procedure is as follows.

(1) Attach the batch type cell holder to LA-920.
(2) A predetermined amount of ion-exchanged water is put into a batch-type cell, and the batch-type cell is set in a batch-type cell holder.
(3) Stir the inside of the batch type cell using a dedicated stirrer chip.
(4) Press the "refractive index" button on the "display condition setting" screen to set the relative refractive index to a value corresponding to the fine particles.
(5) On the "display condition setting" screen, the particle size standard is set as the volume standard.
(6) After performing the warm-up operation for one hour or more, the adjustment of the optical axis, the fine adjustment of the optical axis, and the blank measurement are performed.
(7) 3 mL of the fine particle dispersion is placed in a glass 100 mL flat bottom beaker. Further, 57 mL of ion exchange water is added to dilute the resin fine particle dispersion. As a dispersing agent, "Contaminone N" (a 10% by mass aqueous solution of a neutral detergent for cleaning a precision measuring instrument having a pH of 7 comprising a nonionic surfactant, an anionic surfactant and an organic builder, manufactured by Wako Pure Chemical Industries, Ltd.) Was diluted 3 times with ion-exchanged water.
(8) An ultrasonic disperser “Ultrasonic Dispersion System Tetra 150” (manufactured by Nikkaki Bios Co., Ltd.) having two oscillators having an oscillation frequency of 50 kHz and having a phase difference of 180 ° and having an electrical output of 120 W is prepared. 3.3 L of ion-exchanged water is placed in the water tank of the ultrasonic disperser, and 2 mL of contaminone N is added to the water tank.
(9) The beaker of (7) is set in the beaker fixing hole of the ultrasonic disperser, and the ultrasonic disperser is operated. Then, the height position of the beaker is adjusted so that the resonance state of the liquid surface of the aqueous solution in the beaker is maximized.
(10) The ultrasonic dispersion processing is continued for 60 seconds. In addition, the ultrasonic dispersion is appropriately adjusted so that the water temperature of the water tank is 10 ° C. or more and 40 ° C. or less.
(11) The fine particle dispersion prepared in the above (10) is immediately added little by little to the batch type cell while taking care not to introduce air bubbles, so that the transmittance of the tungsten lamp becomes 90% to 95%. adjust. Then, the particle size distribution is measured. The particle size of the dispersion in the fine particle dispersion is calculated based on the obtained volume-based particle size distribution data.

<Method for Observing Cross Section of Magnetic Toner Particles Using Transmission Electron Microscope (TEM)>
Observation of the cross section of the magnetic toner particles using a transmission electron microscope (TEM) is performed as follows.

  The magnetic toner is embedded in a visible light curable embedding resin (D-800, manufactured by Nissin EM Co., Ltd.), cut to a thickness of 60 nm by an ultrasonic ultramicrotome (EM5, manufactured by Leica), and vacuum stained by a vacuum dyeing apparatus (Filgen). Ru staining).

  Thereafter, the cross section of the obtained magnetic toner particles is observed at an accelerating voltage of 120 kV using a transmission electron microscope (H7500, manufactured by Hitachi High-Technologies Corporation).

  As for the cross section of the magnetic toner particles to be observed, ten cross-sectional images are obtained by selecting ten magnetic toner particles having a size within ± 2.0 μm from the number average particle diameter of the magnetic toner particles.

  Note that, compared to an amorphous resin, a material having crystallinity such as wax does not stain with Ru, and looks white in the cross-sectional image by TEM.

<Calculation method of number average diameter of wax domain>
In the cross-sectional image, the number average diameter of the wax domain is randomly selected from 30 wax domains having a major axis of 20 nm or more, the average value of the major axis and the minor axis is defined as the domain diameter, and the average value of the 30 domains is calculated. The number average diameter of domains. The domains need not be selected in the same magnetic toner particle.

<Method for calculating Ws and Wc>
The distribution state of the wax in the magnetic toner is evaluated by calculating Ws and Wc from the area of the domain of the wax in the cross-sectional image, and using an average value of 10 arbitrarily selected magnetic toners. The image processing software (Photoshop 5.0, manufactured by Adobe) is used to perform “two-tone” processing in “color tone correction” on the cross-sectional image.

  The threshold value is set as an offset gradation on the lower gradation side of the gradation peak indicating the binder resin in the gradation distribution of 255 gradations of the image. An image in which the distinction between the wax domain and the binder resin region is clarified by this two-gradation processing.

  Further, in the cross-sectional image, masking is performed while leaving a region within 1.0 μm (including a boundary of 1.0 μm) from the contour of the cross-section. Then, the occupied area percentage of the domain of the wax whose major axis is 20 nm or more in the obtained area within 1.0 μm is calculated as the occupied area percentage of the wax, and this is defined as Ws.

  On the other hand, the percentage of the occupied area of the domain of the wax whose major axis is 20 nm or more in the inner region inside of 1.0 μm from the contour of the cross section is calculated as the percentage of the occupied area of the wax, and is defined as Wc.

<Calculation method of occupied area ratio of magnetic material in magnetic toner and coefficient of variation (CV3) thereof>
The occupied area ratio of the magnetic substance in the magnetic toner and the coefficient of variation (CV3) thereof are calculated as follows.

  First, an image of a cross section of the magnetic toner is acquired using a transmission electron microscope (TEM). A frequency histogram of the occupied area ratio of the magnetic material in each section grid is obtained from the obtained sectional images based on the section method.

  Further, the variation coefficient of the occupied area ratio of each of the obtained divided grids is obtained and set as the variation coefficient of the occupied area ratio (CV3).

  Specifically, first, a magnetic toner is compression-formed into a tablet. A tablet forming machine having a diameter of 8 mm is filled with 100 mg of the magnetic toner, and the tablet is obtained by applying a force of 35 kN and allowing to stand for 1 minute.

  The obtained tablet is cut by an ultrasonic ultramicrotome (Leica, UC7) to obtain a 250 nm-thick slice sample.

  A STEM image of the obtained thin section sample is taken using a transmission electron microscope (JEOL, JEM2800).

  The probe size used for capturing a STEM image is 1.0 nm, and the image size is 1024 × 1024 pixels. At this time, by adjusting the Contrast of the Detector Control panel of the bright-field image to 1425, the Brightness to 3750, the Contrast of the Image Control panel to 0.0, the Brightness to 0.5, and the Gamma to 1.00, only the magnetic part is adjusted. Can be taken dark. With this setting, a STEM image suitable for image processing is obtained.

  The obtained STEM image is digitized using an image processing device (NIRECO, LUZEX AP).

  Specifically, a frequency histogram of the occupied area ratio of the magnetic material in a square grid having a side of 0.8 μm is obtained by the partitioning method. At this time, the class interval of the histogram is 5%.

  Further, a variation coefficient is obtained from the obtained occupied area ratio of each section grid, and is set as a variation coefficient CV3 of the occupied area ratio. The average value of the occupied area ratios is obtained by averaging the occupied area ratios of the division grids.

<Method of calculating coverage A>
The coverage A is obtained by using a magnetic ultra-high resolution field emission scanning electron microscope S-4800 (Hitachi High-Technologies Corporation) to image a magnetic toner surface image using image analysis software Image-Pro Plus ver. It is calculated by analyzing with 5.0 (Nihon Roper Co., Ltd.). The image shooting conditions of S-4800 are as follows.

(1) Sample preparation A conductive paste is thinly applied to a sample stage (aluminum sample stage 15 mm x 6 mm), and a magnetic toner is sprayed thereon. Further, air blow is performed to remove excess magnetic toner from the sample table and sufficiently dry. The sample stage is set on the sample holder, and the height of the sample stage is adjusted to 36 mm by the sample height gauge.

(2) S-4800 Observation Condition Setting The calculation of the coverage A is performed using an image obtained by the backscattered electron image observation of S-4800. Since the backscattered electron image has less charge-up of the inorganic fine particles than the secondary electron image, the coverage A can be measured with high accuracy.

  Inject the liquid nitrogen into the anti-contamination trap attached to the housing of S-4800 until it overflows, and leave it for 30 minutes. The “PC-SEM” of S-4800 is activated to perform flushing (cleaning of the FE chip as an electron source). Click the acceleration voltage display area on the control panel on the screen and press the [Flushing] button to open the flushing execution dialog. Confirm that the flushing intensity is 2 and execute. Confirm that the emission current due to flushing is 20 to 40 μA. Insert the sample holder into the sample chamber of the S-4800 housing. Press [Origin] on the control panel and move the sample holder to the observation position.

  Click the acceleration voltage display section to open the HV setting dialog, and set the acceleration voltage to [0.8 kV] and the emission current to [20 μA]. In the [Basic] tab of the operation panel, set the signal selection to [SE], set the SE detector to [Upper (U)] and [+ BSE], and select [+ BSE] in the selection box to the right of [+ BSE]. L. A. 100] to set a mode for observing with a backscattered electron image. Similarly, in the [Basic] tab of the operation panel, the probe current of the electron optical system condition block is set to [Normal], the focus mode is set to [UHR], and the WD is set to [3.0 mm]. Press the [ON] button on the acceleration voltage display section of the control panel to apply the acceleration voltage.

(3) Calculation of Number Average Particle Diameter of Magnetic Toner Drag inside the magnification display section of the control panel to set the magnification to 5000 (5k) times. The focus knob [COARSE] on the operation panel is rotated, and the aperture alignment is adjusted when the focus is reached to some extent. Click [Align] on the control panel to display the alignment dialog, and select [Beam]. By rotating the STIGMA / ALIGNMENT knobs (X, Y) on the operation panel, the displayed beam is moved to the center of the concentric circle. Next, "Aperture" is selected, and the STIGMA / ALIGNMENT knobs (X, Y) are turned one by one to stop the movement of the image or adjust the image to the minimum movement. Close the aperture dialog and focus with auto focus. This operation is repeated twice more to focus.

  Thereafter, the particle diameter of 300 magnetic toner particles is measured to determine the number average particle diameter. The number average particle diameter is obtained by measuring the maximum diameter when observing the magnetic toner particles and arithmetically averaging the maximum diameter.

(4) Focus adjustment For the particles having a number average particle size of ± 0.1 μm obtained in (3), drag the inside of the magnification display section of the control panel with the midpoint of the maximum diameter aligned with the center of the measurement screen. The magnification is set to 10000 (10k) times. The focus knob [COARSE] on the operation panel is rotated, and the aperture alignment is adjusted when the focus is reached to some extent. Click [Align] on the control panel to display the alignment dialog, and select [Beam]. By rotating the STIGMA / ALIGNMENT knobs (X, Y) on the operation panel, the displayed beam is moved to the center of the concentric circle. Next, "Aperture" is selected, and the STIGMA / ALIGNMENT knobs (X, Y) are turned one by one to stop the movement of the image or adjust the image to the minimum movement. Close the aperture dialog and focus with auto focus. After that, the magnification is set to 50,000 (50k), the focus is adjusted by using the focus knob and the STIGMA / ALIGNMENT knob in the same manner as described above, and the focus is again adjusted by auto focus. This operation is repeated again to focus. Here, if the angle of inclination of the observation surface is large, the measurement accuracy of the coverage ratio tends to be low.Therefore, when the focus is adjusted, select the one that simultaneously focuses on the entire observation surface, and select the one that has the least inclination of the surface And analyze.

(5) Image storage Brightness adjustment is performed in the ABC mode, and a photograph is taken and stored in a size of 1280 × 960 pixels. The following analysis is performed using this image file. One photograph is taken for each magnetic toner particle, and an image is obtained for at least 30 or more magnetic toner particles.

(6) Image analysis The coverage A is calculated by binarizing the image obtained by the above-described method using the following analysis software. At this time, the screen is divided into 12 squares and analyzed. However, when inorganic fine particles having a particle size exceeding 50 nm enter into the divided section, the calculation of the coverage A is not performed in that section.

Image analysis software Image-Pro Plus ver. The analysis conditions of 5.0 are as follows.
Soft Image-ProPlus 5.1J

Select “Measure” from the toolbar, select “Count / Size”, and then “Option”, and set the binarization condition. Select 8 concatenations in the object extraction option and set the smoothing to 0. In addition, selection, filling of holes, and inclusion lines are not selected in advance, and “exclude boundary lines” is “none”. Select "measurement items" from the "selection" of the tool bar, type 2-10 ⁷ to screen the range of the area.

  The calculation of the coverage is performed around a square area. At this time, the area (C) of the region is set to 24000 to 26000 pixels. "Processing" A value of 0 or more and 255 or less when binarization is automatically performed by binarization is noted. Next, the area value noted above is input by “select range” on the toolbar, and binarization is performed by “count”.

Then, the total sum (D) of the area of the region without silica is calculated. Further, the coverage a is determined by the following equation from the area C of the square area and the total area D of the area without silica.
Coverage a (%) = 100− (D / C × 100)

  As described above, the coverage a is calculated for 30 or more particles of the magnetic toner in each of 10 or more selected ranges, and the average value of the coverage a for a total of 300 or more is defined as the coverage A. .

<Coefficient of variation of coverage A>
The coefficient of variation of the coverage A is determined as follows. Assuming that the standard deviation of all the coverage data used in the calculation of the coverage A is σ (A), the variation coefficient of the coverage A is obtained by the following equation.
Coefficient of variation (%) = {σ (A) / A} × 100

<Calculation of coverage B>
The coverage B is calculated by first removing inorganic fine particles that are not fixed on the surface of the magnetic toner, and then performing the same operation as the calculation of the coverage A.

(1) Removal of non-fixed inorganic fine particles The removal of non-fixed inorganic fine particles is performed as follows. The removal conditions were determined and examined by the present inventors in order to sufficiently remove the inorganic particles other than the particles embedded in the toner surface.

  As an example, using a NOB-130 (manufactured by Hosokawa Micron Co., Ltd.), the ultrasonic dispersion time and the coverage calculated after the ultrasonic dispersion for a magnetic toner having a coverage A of 46% with three kinds of externally applied strength. 6 is shown in FIG. FIG. 6 was prepared by removing the inorganic fine particles by ultrasonic dispersion according to the following method, and then calculating the coverage of the dried magnetic toner in the same manner as in the calculation of the coverage A.

  From FIG. 6, it can be seen that the coverage decreases as the inorganic fine particles are removed by ultrasonic dispersion, and the coverage becomes substantially constant by ultrasonic dispersion for 20 minutes at any externally applied strength. Based on this, it was assumed that the particles other than the inorganic fine particles buried in the toner surface could be sufficiently removed by ultrasonic dispersion for 30 minutes, and the coverage obtained at that time was defined as coverage B.

  More specifically, 16.0 g of water and 4.0 g of Contaminone N (a neutral detergent manufactured by Wako Pure Chemical Industries, Ltd., product No. 037-10361) are charged into a 30 mL glass vial and mixed well. 1.50 g of the magnetic toner is put into the prepared solution, the magnet is approached from the bottom, and all the magnetic toner is submerged. Thereafter, the magnet is moved to remove bubbles and to adjust the magnetic toner to the solution.

  The ultrasonic vibrator UH-50 (made by SMT Co., Ltd., using a titanium alloy tip with a diameter of 6 mm) is set so that the tip is the center of the vial and at a height of 5 mm from the bottom of the vial. The inorganic fine particles are removed by ultrasonic dispersion. After applying ultrasonic waves for 30 minutes, the entire amount of the magnetic toner is taken out and dried. At this time, heat is applied as little as possible, and vacuum drying is performed at 30 ° C. or less.

(2) Calculation of Coverage B Coverage B is obtained by calculating the coverage of the dried magnetic toner in the same manner as the coverage A described above.

<Method of measuring number average particle diameter of primary particles of inorganic fine particles>
The number average particle diameter of the primary particles of the inorganic fine particles is calculated from an inorganic fine particle image of the surface of the magnetic toner taken with a Hitachi ultra-high resolution field emission scanning electron microscope S-4800 (Hitachi High-Technologies Corporation). The image shooting conditions of S-4800 are as follows.

  The operations (1) to (3) were performed in the same manner as in the “calculation of the coverage A” described above, and the focus was adjusted on the surface of the magnetic toner at a magnification of 50,000 (50 k) as in (4). Thereafter, brightness adjustment is performed in the ABC mode. Then, after setting the magnification to 100,000 (100k), focus adjustment is performed using the focus knob and the STIMMA / ALIGNMENT knob in the same manner as in (4), and the focus is adjusted by auto focus. The operation of the focus adjustment is repeated again, and the focus is adjusted at 100000 (100k) times.

  Thereafter, the particle diameter of at least 300 inorganic fine particles on the surface of the magnetic toner is measured, and the number average particle diameter is determined. Here, since some inorganic fine particles exist as agglomerates, the maximum diameter of those that can be identified as primary particles is determined, and the obtained maximum diameter is arithmetically averaged to obtain the number average particle diameter of the primary particles.

  Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited thereto. Unless otherwise specified, all parts and percentages in Examples and Comparative Examples are based on mass.

<Production Example of Resin 1>
・ Styrene 75.0 parts ・ Butyl acrylate 25.0 parts ・ β-carboxyethyl acrylate 2.0 parts ・ Toluene 150.0 parts ・ Polymerization initiator: azobisisobutyronitrile (AIBN) 0.22 parts Stirrer and The above was charged into a reaction vessel equipped with a thermometer while purging with nitrogen. After heating to 70 ° C., polymerization was carried out for 5 hours, and dried under reduced pressure to obtain Resin 1. The peak molecular weight (Mp) of the resin 1 was 8,500.

<Preparation Example of Resin Particle Dispersion 1>
After dissolving 100.0 parts of Resin 1 in 150.0 parts of toluene, put into 300 parts of ion-exchanged water, and add 1.0 part of an anionic surfactant (Neogen RK, Daiichi Kogyo Seiyaku Co., Ltd.). And a homogenizer (Ultra Turrax T50, manufactured by IKA). Thereafter, toluene was separated by distillation to obtain a resin particle dispersion 1. The solid content concentration in the resin particle dispersion 1 was adjusted to 25.0% by mass by adding ion-exchanged water. Table 1 shows the formulation and physical properties of the resin particle dispersion 1.

<Preparation Examples of Resin Particle Dispersions 2 to 7>
Resin particle dispersions 2 to 7 were obtained in the same manner as in the preparation example of resin particle dispersion 1, except that the formulation was changed as shown in Table 1. Table 1 shows the formulations and physical properties of the resin particle dispersions 2 to 7.

<Example of preparation of wax dispersion 1>
・ 50.0 parts of paraffin wax (HNP-9, manufactured by Nippon Seiro Co., Ltd.)
・ 0.3 parts of anionic surfactant (Daiichi Kogyo Seiyaku Co., Ltd., Neogen RK)
-150.0 parts of ion-exchanged water The above was mixed, heated to 95 ° C, and dispersed using a homogenizer (Ultra Turrax T50, manufactured by IKA). Thereafter, dispersion treatment was performed with a Manton-Gaulin high-pressure homogenizer (manufactured by Gorin Co., Ltd.) to prepare a wax dispersion 1 (solid content concentration: 25% by mass) in which wax particles were dispersed. The volume average particle diameter of the obtained wax particles was 0.20 μm.

<Example of preparation of wax dispersion 2>
A wax dispersion 2 was obtained in the same manner as in the preparation example of the wax dispersion 1, except that behenyl behenate (melting point: 73 ° C.) was used instead of paraffin wax. The volume average particle diameter of the obtained wax particles was 0.22 μm.

<Preparation Examples of Wax Dispersions 3 to 5>
In the preparation example of the wax dispersion 1, the addition amount of the surfactant and the conditions of the homogenizer were adjusted to obtain wax dispersions 3 to 5 having physical properties shown in Table 2.

<Example of manufacturing magnetic body 1>
55 liters of a 4.0 mol / L aqueous sodium hydroxide solution was mixed and stirred with 50 liters of an aqueous first aqueous solution of iron sulfate containing 2.0 mol / L of Fe ^2+, and an aqueous ferrous salt solution containing a ferrous hydroxide colloid was stirred. Obtained. This aqueous solution was maintained at 85 ° C., and an oxidation reaction was performed while blowing air at 20 L / min to obtain a slurry containing core particles.

  After filtering and washing the obtained slurry with a filter press, the core particles were dispersed again in water. To the obtained reslurry solution, sodium silicate in an amount of 0.20 mass% in terms of silicon per 100 parts of core particles is added, the pH of the slurry solution is adjusted to 6.0, and the silicon-rich surface is obtained by stirring. Magnetic iron oxide particles were obtained.

  The obtained slurry was filtered and washed with a filter press, and further reslurried with ion-exchanged water. 500 parts (10% by mass based on magnetic iron oxide) of ion exchange resin SK110 (manufactured by Mitsubishi Chemical Corporation) was added to this reslurry liquid (solid content 50 parts / L), and the mixture was stirred for 2 hours to perform ion exchange. Thereafter, the ion-exchange resin was removed by filtration through a mesh, filtered and washed with a filter press, dried and crushed to obtain a magnetic material 1 having a primary particle number average particle size of 0.21 μm.

<Example of manufacturing magnetic body 2>
A magnetic material 2 having a primary particle number average particle size of 0.30 μm was obtained in the same manner as the magnetic material 1 except that the amount of air blown and the oxidation reaction time were adjusted. Was.

<Preparation example of magnetic substance dispersion liquid 1>
-Magnetic substance 1 25.0 parts-Ion exchange water 75.0 parts The above materials were mixed and dispersed using a homogenizer (Ultra Turrax T50, manufactured by IKA). The volume average particle diameter of the magnetic substance in the obtained magnetic substance dispersion liquid 1 was 0.23 μm.

<Example of preparation of magnetic substance dispersion liquid 2>
A magnetic substance dispersion liquid 2 was produced in the same manner as in the preparation example of the magnetic substance dispersion liquid 1, except that the magnetic substance 1 was changed to the magnetic substance 2. The volume average particle diameter of the magnetic substance in the magnetic substance dispersion liquid 2 was 0.35 μm.

<Production Example of Magnetic Toner Particle 1>
-Resin particle dispersion liquid 1 (solid content 25.0 mass%) 150.0 parts-Wax dispersion liquid 1 (solid content 25.0 mass%) 15.0 parts-Magnetic substance dispersion liquid 1 (solid content 25.0 mass%) %) 105.0 parts The above materials were charged into a beaker, adjusted to have a total number of water of 250 parts, and then temperature-controlled to 30.0 ° C. Thereafter, the mixture was mixed by stirring at 5000 rpm for 1 minute using a homogenizer (Ultra Turrax T50 manufactured by IKA).
Furthermore, 10.0 parts of a 2.0 mass% aqueous solution of magnesium sulfate was gradually added as a coagulant.

  The raw material dispersion was transferred to a polymerization vessel equipped with a stirrer and a thermometer, heated to 50.0 ° C. with a mantle heater and stirred to promote the growth of aggregated particles.

  After a lapse of 60 minutes, 200.0 parts of a 5.0% by mass aqueous solution of ethylenediaminetetraacetic acid (EDTA) was added to prepare an aggregated particle dispersion 1.

  Subsequently, the pH of the aggregated particle dispersion 1 was adjusted to 8.0 using an aqueous 0.1 mol / L sodium hydroxide solution, and then the aggregated particle dispersion 1 was heated to 80.0 ° C. and left for 180 minutes. Agglomerated particles were coalesced.

  After a lapse of 180 minutes, a toner particle dispersion 1 in which the toner particles were dispersed was obtained. After cooling at a temperature lowering rate of 1.0 ° C./min, the toner particle dispersion liquid 1 was filtered and washed with ion-exchanged water, and when the conductivity of the filtrate became 50 mS or less, it became a cake. The toner particles were taken out. Next, the caked toner particles are put into ion-exchanged water 20 times the mass of the toner particles, and stirred by a three-one motor. When the toner particles are sufficiently loosened, filtration, water washing, and solidification are performed again. The liquid was separated. The obtained caked toner particles were crushed by a sample mill and dried in an oven at 40 ° C. for 24 hours. Further, after the obtained powder was crushed by a sample mill, additional vacuum drying was performed in an oven at 40 ° C. for 5 hours to obtain magnetic toner particles 1.

<Production Example of Magnetic Toner 1>
The magnetic toner particles 1 were externally mixed with inorganic fine particles using the apparatus shown in FIG.

In this embodiment, a device (NOB-130; manufactured by Hosokawa Micron Co., Ltd.) whose processing space 9 has a volume of 2.0 × 10 ⁻³ m ^{3 in} the device shown in FIG. The power was 5.5 kW, and the shape of the stirring member 3 was as shown in FIG. Then, the overlapping width d of the stirring member 3a and the stirring member 3b in FIG. 3B is set to 0.25D with respect to the maximum width D of the stirring member 3, and the minimum gap between the stirring member 3 and the inner periphery of the main body casing 1 is set to 3. 0.0 mm.

100 parts of magnetic toner particles 1 and 1.0 part of silica fine particles 1 were charged into the apparatus. Silica fine particles 1 were obtained by treating 100 parts of silica fine particles having a BET specific surface area of 200 m ² / g and a number average primary particle diameter of 11 nm with 20 parts of hexamethyldisilazane, and then with 10 parts of dimethyl silicone oil. It is.

  After charging the magnetic toner particles and the silica fine particles 1, pre-mixing was performed to uniformly mix the magnetic toner particles and the silica fine particles 1.

  The pre-mixing conditions were as follows: the power of the driving unit 8 was 0.1 W / g (the number of rotations of the driving unit 8 was 150 rpm), and the processing time was 1 minute.

  After the completion of the premixing, an external addition mixing process was performed. The external mixing process conditions are such that the peripheral speed of the outermost end of the stirring member 3 is adjusted so that the power of the driving unit 8 is constant at 1.0 W / g (the rotation speed of the driving unit 8 is 1800 rpm), and the processing time For 5 minutes. Table 4 shows the conditions of the external mixing treatment.

  After the external addition and mixing treatment, coarse particles and the like were removed with a circular vibrating sieve equipped with a screen having a diameter of 500 mm and a mesh size of 75 μm, to obtain Magnetic Toner 1. The magnetic toner 1 was enlarged and observed with a scanning electron microscope, and the number average particle diameter of primary particles of silica fine particles on the surface of the magnetic toner was measured to be 13 nm.

  Table 4 shows the external addition conditions and physical properties of the obtained magnetic toner 1. Table 5 shows the results of the magnetic toner 1 obtained below.

  Volume average particle diameter (Dv), number average particle diameter (Dn), average luminance in Dn [In the table, simply referred to as average luminance. ], CV1, CV2 / CV1, and the average value of the occupied area ratio of the magnetic material [A is represented in the table. ], Average circularity, number average diameter of wax domains [in the table, denoted by B]. ], The peak molecular weight of the main peak measured using GPC of the tetrahydrofuran-soluble component of the magnetic toner [In the table, it is expressed as Mp. ].

<Example 1>
(Image forming device)
LaserJet Pro M12 (manufactured by Hewlett Packard) of a one-component contact developing system was used after being modified to 200 mm / sec, which is faster than the original process speed.

The device modified as described above was charged with 100 g of the magnetic toner 1, and the following evaluation was performed. As a recording material, a bussess 4200 (manufactured by Xerox) having a basis weight of 75 g / m ² was used.

  Table 6 shows the evaluation results. The evaluation method and evaluation criteria in each evaluation are as follows.

<Evaluation of image density>
Using the above-described modified machine, a durability test was performed in a low-temperature and low-humidity environment (15.0 ° C./10.0% RH) to print 3000 horizontal lines with a printing rate of 2% in an intermittent mode.

  For the image density, a solid image portion was formed at the beginning of the durability test and after the durability test, and the density of the solid image was measured with a Macbeth reflection densitometer (manufactured by Macbeth).

  With the magnetic toner 1, a good solid black image having a high image density was obtained before and after the durability test. The evaluation criteria for the image density are as follows.

(Evaluation criteria for solid image density at the beginning of durability (described as "initial density" in Table 6))
A: 1.45 or more B: 1.40 or more and less than 1.45 C: 1.35 or more and less than 1.40 D: less than 1.35 Judgment was made based on the difference in solid image density after the test (described as "density difference" in Table 6). The smaller the density difference, the better.

(Evaluation criteria)
A: 0.05 or less B: More than 0.05, 0.10 or less C: More than 0.10, 0.15 or less D: More than 0.15

<Evaluation of fog>
Fog was evaluated after the durability test at the above image density. By evaluating fog in a low-temperature and low-humidity environment, it is possible to strictly evaluate fog caused by cracking or chipping of the toner, which is affected by the brittleness of the toner. After the endurance test, a white image was output, and the reflectance was measured using REFLECMETER MODEL TC-6DS manufactured by Tokyo Denshoku Co., Ltd. On the other hand, the reflectance of the transfer paper (standard paper) before white image formation was measured in the same manner. A green filter was used as the filter. Fog was calculated from the reflectance before and after outputting the white image using the following equation. Fog (reflectance) (%) = reflectance of standard paper (%)-reflectance of white image sample (%)
With Magnetic Toner 1, a good image with suppressed fog was obtained before and after the durability test. The criteria for fogging are as follows.

A: Less than 1.2% B: 1.2% or more and less than 2.0% C: 2.0% or more and less than 3.0% D: 3.0% or more

<Evaluation of development streak>
The development streak was evaluated by filling the remodeled machine with 100 g of the magnetic toner 1 and performing a durability test under a high temperature and high humidity environment (32.5 ° C./80% RH), similarly to the image density. An endurance test was performed on 3000 horizontal lines with a printing rate of 2% in an intermittent mode, and the presence or absence of vertical streaks due to fusion of the toner to the regulating member, so-called development streaks, was evaluated during the endurance test. , A solid black image was output and visually confirmed.

  By performing the treatment in a high-temperature and high-humidity environment, the fusion of the toner to the regulating member is easily promoted, and the development streak can be strictly evaluated.

  In the evaluation results of Magnetic Toner 1, no development streak occurred during the durability test. The criteria for the development streak are as follows.

A: No occurrence at 3,000 sheets B: Occurs at more than 2,000 sheets and 3,000 sheets or less C: Occurs at more than 1,000 sheets at 2,000 sheets or less D: Occurs at 1,000 sheets or less

<Evaluation of rear end offset>
Using the above modified machine, the settings of the fixing device were changed so that the temperature control of the fixing device was further reduced by 10 ° C. In a high-temperature and high-humidity environment (32.5 ° C./80% RH), the following evaluation was performed with the fixing device removed during the evaluation and the fixing device cooled sufficiently using a fan or the like.

  By sufficiently cooling the fixing device after the evaluation, the temperature of the fixing nip that has risen after the image is output is cooled, so that the toner fixing property can be strictly evaluated and the reproducibility can be evaluated.

When evaluating the trailing edge offset, a recording material was used in which A4 Oced Red Label paper (basis weight: 80 g / m ² ) manufactured by Canon was left in the high-temperature, high-humidity environment for 48 hours or more.

  By using a paper that is relatively heavy and has a large surface roughness, and further using a paper that has been left in a high-temperature and high-humidity environment (an abandoned paper), the trailing edge offset can be strictly evaluated.

Using the magnetic toner 1, a solid black image was output on the aged paper while the fixing device was sufficiently cooled. At this time, the amount of toner applied on the paper was adjusted to 9 g / m ² . In the evaluation result of the magnetic toner 1, a favorable solid black image without rear end offset was obtained.

  As a criterion for determining the rear end offset, the level of the offset was visually evaluated for the solid black image output in the above procedure. The criteria are as follows.

A: No offset at all B: Offset is slightly seen when viewed closely C: Offset is seen but not noticeable D: Offset is noticeable

<Production Example of Magnetic Toner Particle 2>
(Pre-aggregation step)
-Magnetic substance dispersion liquid 1 (solid content: 25.0% by mass) 105.0 parts The above materials were charged into a beaker, and the temperature was adjusted to 30.0 ° C. Then, a homogenizer (Ultra Turrax T50, manufactured by IKA) was added. The mixture was stirred at 5000 rpm for 1 minute, and 1.0 part of a 2.0 mass% aqueous solution of magnesium sulfate was gradually added as a coagulant, followed by stirring for 1 minute.

(Aggregation step)
-Resin particle dispersion liquid 1 (solid content: 25.0 mass%) 150.0 parts-Wax dispersion liquid 1 (solid content: 25.0 mass%) 15.0 parts The material was charged into the above beaker, and the total number of parts of water was measured. Was adjusted to 250 parts, and then mixed by stirring at 5000 rpm for 1 minute.

  Further, as a coagulant, 9.0 parts of a 2.0 mass% aqueous solution of magnesium sulfate was gradually added.

  The raw material dispersion was transferred to a polymerization vessel equipped with a stirrer and a thermometer, heated to 50.0 ° C. with a mantle heater and stirred to promote the growth of aggregated particles.

  After a lapse of 59 minutes, 200.0 parts of a 5.0% by mass aqueous solution of ethylenediaminetetraacetic acid (EDTA) was added to prepare an aggregated particle dispersion 2.

  Subsequently, the pH of the aggregated particle dispersion liquid 2 was adjusted to 8.0 using a 0.1 mol / L aqueous sodium hydroxide solution, and then the aggregated particle dispersion liquid 2 was heated to 80.0 ° C and left for 180 minutes. Agglomerated particles were coalesced.

  After a lapse of 180 minutes, a toner particle dispersion liquid 2 in which the toner particles were dispersed was obtained. After cooling at a cooling rate of 1.0 ° C./min, the toner particle dispersion liquid 2 was filtered and washed with ion-exchanged water, and when the conductivity of the filtrate became 50 mS or less, it became a cake. The toner particles were taken out. Next, the caked toner particles are put into ion-exchanged water 20 times the mass of the toner particles, and stirred by a three-one motor. When the toner particles are sufficiently loosened, filtration, water washing, and solidification are performed again. The liquid was separated. The obtained caked toner particles were crushed by a sample mill and dried in an oven at 40 ° C. for 24 hours. Further, the obtained powder was pulverized by a sample mill, and further subjected to additional vacuum drying in an oven at 40 ° C. for 5 hours to obtain magnetic toner particles 2.

<Production Examples of Magnetic Toner Particles 3 to 17>
Magnetic toner particles 3 to 17 were obtained in the same manner as in the production example of magnetic toner particles 1 except that the conditions described in Table 3 were changed.

  In the production example of the magnetic toner particles 3, in the first coagulation step, 0.2 part of a surfactant (Neugen TDS-200, Daiichi Kogyo Seiyaku Co., Ltd.) was added, and then the coagulant was added.

  Further, in the production examples of the magnetic toner particles 14 and 15, after the first aggregation step of promoting the growth of the aggregated particles at 50.0 ° C., the dispersion described in Table 3 was added. A second aggregation step was performed to promote the growth of aggregated particles.

<Production Example of Magnetic Toner Particles 18>
-Resin 1 100.0 parts-Paraffin wax 4.0 parts (NNP-9, HNP-9)
-Magnetic substance 1 65.0 parts-Charge control agent 1.0 part (azo iron compound; T-77, Hodogaya Chemical Industry Co., Ltd.)
The raw materials were premixed for 2 minutes at 2500 rpm using an FM mixer (FM10C, manufactured by Nippon Coke Industry Co., Ltd.). Thereafter, the set temperature was adjusted by a twin-screw kneading extruder (PCM-30: manufactured by Ikegai Iron Works) set at 200 rpm so that the temperature of the kneaded material near the outlet of the kneaded material was 150 ° C., and kneading was performed. .

  After cooling the obtained melt-kneaded material and coarsely pulverizing the cooled melt-kneaded material with a cutter mill, the obtained coarsely-kneaded material is fed to a turbo mill T-250 (manufactured by Turbo Kogyo Co., Ltd.) to adjust the feed amount. The air was adjusted to 20 kg / hr, and the air temperature was adjusted so that the exhaust temperature became 38 ° C., and pulverization was performed. Further, the particles were classified using a multi-part classifier utilizing the Coanda effect to obtain magnetic toner particles 18 having a weight average particle size of 7.58 μm.

<Production Example of Magnetic Toner Particle 19>
-Resin particle dispersion liquid 2 (solid content 25.0 mass%) 150.0 parts-Wax dispersion liquid 1 (solid content 25.0 mass%) 15.0 parts-Magnetic substance dispersion liquid 1 (solid content 25.0 mass%) %) 105.0 parts The above materials were charged into a beaker, adjusted to have a total number of water of 250 parts, and then temperature-controlled to 30.0 ° C. Thereafter, the mixture was mixed by stirring at 8000 rpm for 10 minutes using a homogenizer (Ultra Turrax T50, manufactured by IKA).

  Further, 0.1 mol / L hydrochloric acid was gradually added to adjust the pH to 5.0, and the mixture was further stirred at 8000 rpm for 20 minutes.

  The raw material dispersion liquid was transferred to a polymerization vessel equipped with a stirrer and a thermometer, heated to 50.0 ° C. with a mantle heater, and 0.1 mol / L hydrochloric acid was gradually added to adjust the pH to 3.0, followed by stirring. By doing so, the growth of aggregated particles was promoted.

  After a lapse of 60 minutes, the pH of the aggregated particle dispersion 19 is adjusted to 6.8 using a 0.1 mol / L aqueous sodium hydroxide solution, and then the aggregated particle dispersion 19 is heated to 90.0 ° C. The aggregated particles were coalesced by being left for 180 minutes.

  After a lapse of 180 minutes, a toner particle dispersion liquid 19 in which the toner particles were dispersed was obtained. After cooling at a temperature lowering rate of 1.0 ° C./min, the toner particle dispersion liquid 19 was filtered and washed by passing ion-exchanged water. When the conductivity of the filtrate became 50 mS or less, it became a cake. The toner particles were taken out.

  Next, the caked toner particles are put into ion-exchanged water 20 times the mass of the toner particles, and stirred by a three-one motor. When the toner particles are sufficiently loosened, filtration, water washing, and solidification are performed again. The liquid was separated. The obtained caked toner particles were crushed by a sample mill and dried in an oven at 40 ° C. for 24 hours. Further, the obtained powder was pulverized by a sample mill, and further subjected to additional vacuum drying in an oven at 40 ° C. for 5 hours to obtain magnetic toner particles 19.

<Production Example of Magnetic Toner Particle 20>
(Pre-aggregation step)
-Magnetic substance dispersion liquid 1 (solid content: 25.0% by mass) 105.0 parts The above materials were charged into a beaker, and the temperature was adjusted to 30.0 ° C. Then, a homogenizer (Ultra Turrax T50, manufactured by IKA) was added. The mixture was stirred at 8000 rpm for 10 minutes, and 1.0 part of a 2.0 mass% aqueous solution of magnesium sulfate was gradually added as a coagulant, followed by stirring for 10 minutes.

(Aggregation step)
-Resin particle dispersion liquid 1 (solid content: 25.0 mass%) 150.0 parts-Wax dispersion liquid 1 (solid content: 25.0 mass%) 15.0 parts The material was charged into the above beaker, and the total number of parts of water was measured. Was adjusted to 250 parts, and then mixed by stirring at 8000 rpm for 1 minute.

  Further, as a coagulant, 9.0 parts of a 2.0 mass% aqueous solution of magnesium sulfate was gradually added.

  The raw material dispersion was transferred to a polymerization vessel equipped with a stirrer and a thermometer, heated to 50.0 ° C. with a mantle heater and stirred to promote the growth of aggregated particles.

  After a lapse of 50 minutes, 200.0 parts of a 5.0% by mass aqueous solution of ethylenediaminetetraacetic acid (EDTA) was added to prepare an aggregated particle dispersion liquid 20.

  Subsequently, the pH of the aggregated particle dispersion 20 was adjusted to 8.0 using an aqueous 0.1 mol / L sodium hydroxide solution, and then the aggregated particle dispersion 20 was heated to 80.0 ° C. and left for 180 minutes. Agglomerated particles were coalesced.

  After a lapse of 180 minutes, a toner particle dispersion liquid 20 in which the toner particles were dispersed was obtained. After cooling at a temperature lowering rate of 1.0 ° C./min, the toner particle dispersion liquid 20 was filtered and washed with ion-exchanged water, and when the conductivity of the filtrate became 50 mS or less, it became a cake. The toner particles were taken out.

  Next, the caked toner particles are put into ion-exchanged water 20 times the mass of the toner particles, and stirred by a three-one motor. When the toner particles are sufficiently loosened, filtration, water washing, and solidification are performed again. The liquid was separated. The obtained caked toner particles were crushed by a sample mill and dried in an oven at 40 ° C. for 24 hours. Further, after the obtained powder was crushed by a sample mill, additional vacuum drying was performed in an oven at 40 ° C. for 5 hours to obtain magnetic toner particles 20.

<Production Example of Magnetic Toner Particles 21>
The magnetic toner particles 2 and the magnetic toner particles 3 were mixed well by the same amount to obtain magnetic toner particles 21.

<Production Examples of Magnetic Toners 2 to 31>
In the production example of the magnetic toner 1, the magnetic toner particles No. Magnetic toners 2 to 31 were obtained in the same manner, except that the external addition prescription, the external addition device, the external addition conditions, and the processing time were changed as shown in Table 4. Table 4 shows the physical properties of the obtained magnetic toners 2 to 31.

  In addition, Table 5 shows the following results of the magnetic toners 2 to 31.

  Volume average particle diameter (Dv), number average particle diameter (Dn), average luminance in Dn [In the table, simply referred to as average luminance. ], CV1, CV2 / CV1, and the average value of the occupied area ratio of the magnetic material [A is represented in the table. ], Average circularity, number average diameter of wax domains [in the table, denoted by B]. ], The peak molecular weight of the main peak measured using GPC of the tetrahydrofuran-soluble component of the magnetic toner [In the table, it is expressed as Mp. ]. Table 6 shows the evaluation results of the magnetic toners 2 to 31.

As the titania fine particles described in Table 4, anatase-type titanium oxide fine particles [BET specific surface area: 80 m ² / g, number average particle diameter of primary particles: 15 nm, treated with 12% by mass of isobutyltrimethoxysilane] were used.

  For the magnetic toners 10 and 11, and the magnetic toners 13 to 31, the external addition was immediately performed after the magnetic toner particles and the inorganic fine particles were charged without performing pre-mixing.

In Table 4,
"A" in the external additive device represents "NOB-130" (manufactured by Hosokawa Micron Corporation), and "B" represents "FM mixer FM10C" (manufactured by Nippon Coke Industry Co., Ltd.).

<Examples 2 to 23 and Comparative Examples 1 to 8>
The same evaluation as in Example 1 was performed using the magnetic toners 2 to 31. Table 6 shows the results.

DESCRIPTION OF SYMBOLS 1 Main body casing 2 Rotating body 3, 3a, 3b Stirring member 4 Jacket 5 Raw material input port 6 Product discharge port 7 Center axis 8 Drive unit 9 Processing space 10 Rotating body end side surface 11 Rotation direction 12 Return direction 13 Feed direction 16 Raw material input Inner piece for mouth 17 Inner piece for product outlet d Spacing indicating overlapping portion of stirring member D Width of stirring member 43 Cleaner container 44 Cleaning blade 45 Electrostatic latent image carrier 46 Charging roller 47 Toner carrier 48 Toner supply member 49 Developing device 50 Transfer member (transfer roller)
51 fixing device 52 pickup roller 53 transfer material (paper)
54 Laser generator 55 Toner regulating member 56 Fixing member 57 Toner 58 Stirring member R1, R2 and R3 Rotation direction

Claims (9)

A magnetic toner containing a binder resin, a magnetic toner particle containing a magnetic substance and a wax, and inorganic fine particles present on the surface of the magnetic toner particle,
In the cross section of the magnetic toner using a transmission electron microscope,
A coefficient of variation CV3 of the occupied area ratio of the magnetic material when the cross section of the magnetic toner is divided by a square grid having a side of 0.8 μm is 40.0% or more and 80.0% or less;
The inorganic fine particles contain at least one inorganic oxide fine particle selected from the group consisting of silica fine particles, titania fine particles, and alumina fine particles, and 85% by mass or more of the inorganic oxide fine particles are silica fine particles,
Assuming that the coverage of the surface of the magnetic toner particles with the inorganic fine particles is coverage A (%), the coverage A is 45.0% or more and 80.0% or less;
The wax forms a domain inside the magnetic toner particles, and the number average diameter of the domain is 100 nm or more and 500 nm or less,
The binder resin contains a styrene resin,
A magnetic toner characterized in that a peak molecular weight of a main peak measured by gel permeation chromatography of a tetrahydrofuran-soluble component of the magnetic toner is 5,000 or more and 12,000 or less. The number average particle diameter of the magnetic toner is Dn (μm),
A coefficient of variation of a luminance dispersion value of the magnetic toner in a range of Dn−0.500 or more and Dn + 0.500 or less is CV1 (%),
When the variation coefficient of the luminance dispersion value of the magnetic toner in the range of Dn-1.500 to Dn-0.500 is CV2 (%),
The CV1 and the CV2 satisfy the relationship of the following formula (1),
The magnetic toner according to claim 1, wherein the average brightness of the magnetic toner at the Dn is 30.0 or more and 60.0 or less.
CV2 / CV1 ≦ 1.00 (1) In the cross section of the magnetic toner using a transmission electron microscope,
The average value of the occupied area ratio of the magnetic material when the cross section of the magnetic toner is divided by a square grid having a side of 0.8 μm is 10.0% or more and 40.0% or less. 3. The magnetic toner according to item 1.   The magnetic toner according to claim 2, wherein the CV1 is 4.00% or less.   When the coverage by the inorganic fine particles fixed to the surface of the magnetic toner particles is defined as coverage B (%), the ratio of the coverage B to the coverage A is 0.50 or more and 0.85 or less. The magnetic toner according to claim 1.   The magnetic toner according to claim 1, wherein a coefficient of variation of the coverage A is 10.0% or less.   The magnetic toner according to claim 1, wherein the average circularity of the magnetic toner is 0.960 or more.   The magnetic toner according to claim 1, wherein the wax contains a hydrocarbon wax. A charging step of applying a voltage to the charging member from outside to charge the electrostatic latent image carrier,
A latent image forming step of forming an electrostatic latent image on the charged electrostatic latent image carrier,
A developing step of developing the electrostatic latent image with a toner carried on a toner carrier to form a toner image on the electrostatic latent image carrier;
A transfer step of transferring the toner image on the electrostatic latent image carrier to a transfer material with or without an intermediate transfer member, and
An image forming method including a fixing step of fixing a toner image transferred to a transfer material by heating and pressing means,
The developing step is a one-component contact developing method in which the electrostatic latent image carrier and the toner carried on the toner carrier are directly contacted to perform development,
The toner is
Binder resin, magnetic toner particles containing a magnetic substance and wax, and a magnetic toner containing inorganic fine particles present on the surface of the magnetic toner particles,
In the cross section of the magnetic toner using a transmission electron microscope,
A coefficient of variation CV3 of the occupied area ratio of the magnetic material when the cross section of the magnetic toner is divided by a square grid having a side of 0.8 μm is 40.0% or more and 80.0% or less;
The inorganic fine particles contain at least one inorganic oxide fine particle selected from the group consisting of silica fine particles, titania fine particles, and alumina fine particles, and 85% by mass or more of the inorganic oxide fine particles are silica fine particles,
Assuming that the coverage of the surface of the magnetic toner particles by the inorganic fine particles is coverage A (%), the coverage A is 45.0% or more and 80.0% or less;
The wax forms a domain inside the magnetic toner particles, and the number average diameter of the domain is 100 nm or more and 500 nm or less,
The binder resin contains a styrene resin,
An image forming method, wherein a peak molecular weight of a main peak measured by gel permeation chromatography of a tetrahydrofuran-soluble component of the magnetic toner is 5,000 or more and 12,000 or less.

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