JP7195799B2 - Magnetic toner and image forming method - Google Patents

Description

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

In recent years, there has been a demand for means for outputting images in a wide range of fields, from offices to homes, and one of them is demanding high durability that does not degrade image quality even when a large number of images are output in various usage environments. On the other hand, in addition to image quality, the image output device itself is required to be smaller and energy-saving.

As a means of miniaturization, it is effective to reduce the size of the cartridge containing the developer. , the contact development system is preferred. Therefore, the one-component contact development system is an effective means for satisfying the above performance.

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). That is, the toner is transported by rotating these carriers, and the contact portion receives a large share. Therefore, in order to obtain high-quality images, the toner must have high durability and high fluidity. necessary.

Toner with low fluidity stays in the carrier during development, is heated by rubbing, and tends to be fused. In particular, when the toner is fused in the toner carrier, "streaks" occur on the image.

On the other hand, a toner with low durability causes cracks and chips, contaminates the toner carrier and the electrostatic latent image carrier, and deteriorates the image quality. In addition, cracked or chipped toner is less likely to be charged, and may become a "fogging" component that is developed in a non-image area on the electrostatic latent image carrier.

Magnetic toner containing a magnetic substance (hereinafter also simply referred to as toner) has a large difference in density between the resin and the magnetic substance. In particular, cracking and chipping of toner tend to occur.

When it is desired to output a large number of images in various usage environments, a greater load is placed on the toner, and thus higher durability and higher fluidity are required.

Patent Document 1 proposes a toner containing a magnetic material.

Japanese Patent Application Laid-Open No. 2002-201000 proposes a magnetic toner in which a magnetic material is dispersed by using an aggregation method. This manufacturing method has an aggregating step of aggregating fine particles to a toner particle size and a coalescing step of melting the aggregates to coalesce and form a toner. With this method, the shape of the toner can be easily deformed, and the fluidity can be increased.

Japanese Patent Application Laid-Open No. 2002-200000 discloses that it is possible to achieve both the image density in a durability test and the suppression of a decrease in density upon rubbing by specifying a specific wax and the state of existence of inorganic fine particles on the surface of the toner. ing.

In Japanese Patent Application Laid-Open No. 2002-100000, the total coverage of toner base particles with an external additive is controlled to stabilize the development and transfer processes.

JP 2006-243593 A JP 2012-93752 A Japanese Patent No. 5361984 Japanese Patent Application Laid-Open No. 2007-293043

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

The toner disclosed in Patent Document 2 can absorb share in a system such as a one-component contact development system that requires share when the distance between the magnetic bodies is uniform and the magnetic bodies are relatively close to each other. There is a problem that the part is insufficient and toner deterioration is likely to occur.

Conversely, a toner in which the magnetic material is excessively aggregated has a problem that the coloring power is lowered due to the decrease in the surface area of the magnetic material, and the density of the output image tends to be lowered. In addition, such a toner has a problem that the content of the magnetic material tends to vary from one toner particle to another, and the density of the image gradually decreases when a large number of images are output.

The toner disclosed in Patent Document 4 certainly achieves a certain effect by controlling the calculated theoretical coverage for certain specific toner base particles. However, the actual adhesion state of the external additive may differ greatly from the calculated value when the toner is assumed to be a true sphere. otherwise it is insufficient. As a result of studies by the present inventors, it was found necessary to further improve durability and responsiveness to heat during fixing in the case of further speeding up the image output apparatus and application to the one-component contact development system described above.

The present invention provides high-quality images in various usage environments even in a system such as the one-component contact development system, which requires a high market share.

That is, there is room for improvement in the above-mentioned patent document from the viewpoint of ensuring durability and achieving both responsiveness to heat during fixing, even in a system that requires a larger market share.

Focusing on the fixing process from the viewpoint of demanding even higher image quality, as the purpose of use and the use environment diversified, offset ( hereinafter also referred to as trailing edge offset).

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

The reason why trailing edge offset is more likely to occur in high coverage images than in low coverage images is thought to be due to the amount of heat applied to the toner layer. As the coverage rate of the image becomes higher, the amount of heat from the fixing device is distributed to more toner, so that the amount of insufficiently melted toner increases, resulting in poor fixing.

Furthermore, since the amount of heat applied from the fixing nip portion tends to decrease toward the trailing edge of the image, fixability tends to be disadvantageous at the trailing edge of the image.

In particular, the trailing edge offset tends to become noticeable in paper that has been left in a high-temperature, high-humidity environment. When paper that has been left in a high-temperature, high-humidity environment and contains a lot of moisture passes through a fixing device, the heat from the fixing device generates water vapor from the paper at the fixing nip. It is presumed that the trailing edge offset is caused by the toner layer on the paper being pressed against the fixing member side by this water vapor.

In other words, if the paper left in a high-temperature and high-humidity environment is used in a state in which poor fixation is likely to occur at the trailing edge of a high coverage image, trailing edge offset is likely to occur.

Further, conventionally, improvements such as designing the softening temperature to be low have been made in order to improve the fixability of the toner. Indeed, with such a design, the thermal fusibility of the portion to which the heat is fully applied is enhanced. However, on the other hand, when the amount of heat applied is not sufficient, such as at the trailing edge of a high coverage image, the toner melting speed cannot keep up, making it difficult to suppress the occurrence of the trailing edge offset of the high coverage image. rice field.

That is, the present invention provides a magnetic toner capable of suppressing the occurrence of trailing edge offset of high-print-rate images even in a high-temperature, high-humidity environment and ensuring durability even in a high-sharing system, and uses the magnetic toner. An image forming method is provided.

The present invention
magnetic toner particles containing a binder resin, a magnetic substance and wax;
Inorganic fine particles present on the surface of the magnetic toner particles ;
A magnetic toner containing
The magnetic toner is an emulsion aggregation magnetic toner having an average circularity of 0.960 or more,
In a 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,
When the surface coverage of the magnetic toner particles with the inorganic fine particles is defined as a coverage A (%), the coverage A is 45.0% or more and 80.0% or less,
the wax forms domains inside the magnetic toner particles, and the number average diameter of the domains is 100 nm or more and 500 nm or less;
The binder resin contains a styrene-based resin,
The main peak has a peak molecular weight of 5000 or more and 12000 or less as measured by gel permeation chromatography of the tetrahydrofuran-soluble portion of the magnetic toner.
A magnetic toner characterized by:

In addition, the present invention
a charging step of externally applying a voltage to the charging member 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 magnetic 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 bearing member to a transfer material with or without an intermediate transfer member;
a fixing step of fixing the toner image transferred to the transfer material by a heating and pressurizing means ;
An image forming method comprising
The developing step is a developing step by a one-component contact development system in which the electrostatic latent image carrier and the magnetic toner carried on the toner carrier are brought into direct contact with each other, and
The magnetic toner is
magnetic toner particles containing a binder resin, a magnetic substance and wax;
Inorganic fine particles present on the surface of the magnetic toner particles ;
and an emulsion aggregation magnetic toner having an average circularity of 0.960 or more ,
In a 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,
When the surface coverage of the magnetic toner particles with the inorganic fine particles is defined as a coverage A (%), the coverage A is 45.0% or more and 80.0% or less,
the wax forms domains inside the magnetic toner particles, and the number average diameter of the domains is 100 nm or more and 500 nm or less;
The binder resin contains a styrene-based resin,
The main peak has a peak molecular weight of 5000 or more and 12000 or less as measured by gel permeation chromatography of the tetrahydrofuran-soluble portion of the magnetic toner.
This image forming method is characterized by:

According to the present invention, there is provided a magnetic toner capable of suppressing the occurrence of trailing edge offset of an image with a high print rate even in a high-temperature and high-humidity environment and ensuring durability even in a system with high share, and the use of the magnetic toner. It is possible to provide an image forming method that has

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

In the present invention, unless otherwise specified, the descriptions of "○○ or more and XX or less" and "○○ to XX", which represent numerical ranges, mean numerical ranges including the lower and upper limits that are endpoints.

A monomeric unit also refers to the reacted form of the monomeric material in the polymer.

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

The magnetic toner of the present invention (hereinafter also simply referred to as toner) is
A magnetic toner containing magnetic toner particles containing a binder resin, a magnetic substance and wax, and inorganic fine particles present on the surfaces of the magnetic toner particles,
In a 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,
When the surface coverage of the magnetic toner particles with the inorganic fine particles is defined as a coverage A (%), the coverage A is 45.0% or more and 80.0% or less,
the wax forms domains inside the magnetic toner particles, and the number average diameter of the domains is 100 nm or more and 500 nm or less;
The binder resin contains a styrene-based resin,
A tetrahydrofuran-soluble portion of the magnetic toner has a main peak molecular weight of 5,000 or more and 12,000 or less measured by gel permeation chromatography.

In the magnetic toner, the state of dispersion of the magnetic substance in the magnetic toner particles and the state of coating of the inorganic fine particles present on the surfaces 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 where the toner is strongly sheared, and it is possible to suppress the occurrence of trailing edge offset of a high-printing rate image even in a high-temperature and high-humidity environment. .

The reason for this is not clear, but the inventors consider it as follows.

The toner fixing step is a step of accelerating the melting and deformation of the toner by the heat of the fixing member and fixing the toner to a medium such as paper. Therefore, when the amount of heat is reduced for energy-saving fixing, various factors are important for fixing the toner onto the media.

It is important to quickly deform the toner particles with respect to heat applied from the outside, and to increase the force that tends to adhere to the media rather than the force that tends to adhere to the fixing member. Furthermore, it is also important to make the toner layer uniform on the paper before fixing, which will be described later in detail. By doing so, the amount of heat can be efficiently transferred to all the toner on the medium, sufficient fixability can be obtained with a small amount of heat, and occurrence of trailing edge offset can be effectively suppressed. In addition, the toner having the above structure is excellent in toner particle deformability and wax extrusion effect, and the releasability of the toner from the fixing member is increased, and the adhesiveness to paper (anchoring effect) is relatively increased. I'm guessing.

The peak molecular weight (Mp) of the main peak measured by gel permeation chromatography (GPC) of the tetrahydrofuran (THF) soluble portion of the magnetic toner is 5000 or more and 12000 or less. By controlling the molecular weight to a relatively low value in this way, it is believed that the deformability of the magnetic toner due to heat can be increased.

Further, in the magnetic toner, the coverage A (%) is 45.0% or more and 80.0% or less when the surface coverage of the magnetic toner particles with the inorganic fine particles is defined as A (%). 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 a fixing device. In the stage before fixing, the image exists in a state in which it is transferred from the photoreceptor onto a medium such as paper, so in that state it still exists in a movable state.

In order to transfer the heat from the fixing device to the toner most efficiently and evenly, it is necessary to increase the contact area between the toner on the paper after the transfer process and the fixing device. It is considered effective to increase the number as much as possible. For this purpose, it is considered effective to control the toner layer on the paper so as to be uniform, and particularly to control the surface in contact with the fixing device as smooth as possible.

The magnetic toner has a relatively high inorganic fine particle coverage A of 45.0% or more and 80.0% or less. Adhesion between them is also reduced.

Therefore, the toner after the transfer process is less likely to aggregate due to the low adhesion between the toner particles, and the toner layer is more densely packed. As a result, the toner layer is made uniform, unevenness on the upper portion of the toner layer is less likely to exist, and the area in contact with the fixing device can be increased.

This effect also makes it possible to expand the application range of media such as paper. 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 with a fixing member such as a fixing film and a low electrostatic adhesion force, the releasing effect from the fixing member is large, and the anchoring effect to the paper is relatively small. can promote.

The van der Waals force and low electroadhesion are discussed in more detail below. First, regarding the van der Waals force, the van der Waals force (F) generated between the flat plate and the grain is expressed by the following equation.
F=H×D/(12Z ² )

Here, H is the Hamaker constant, D is the particle size of the grain, and Z is the distance between the grain and the plate. As for Z, it is generally said that an attractive force works when the distance is long and a repulsive force works when the distance is very short. From the above formula, the van der Waals force (F) is proportional to the grain size of the grain 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 size 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 the magnetic toner particles are in direct contact with the fixing member.

Next, electrostatic adhesion force can be rephrased as reflection force. It is known that the specular force is generally proportional to the square of the charge (q) of the particle and inversely proportional to the square of the distance.

When the magnetic toner is charged, it is the surface of the magnetic toner particles, not the inorganic fine particles, that carries 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 mirror force.

That is, on the surface of the magnetic toner, when the magnetic toner particles are in contact with the flat plate through the inorganic fine particles, the distance between the surface of the magnetic toner particle and the flat plate is increased, thereby reducing the mirror force.

As described above, the inorganic fine particles are present on the surface of the magnetic toner particles, and the magnetic toner comes into contact with the fixing member via the inorganic fine particles, thereby reducing the Van der Waals force and the mirror force generated between the magnetic toner and the fixing member. . That is, the adhesive force between the magnetic toner and the fixing member is lowered.

Next, whether the magnetic toner particles come into direct contact with the fixing member or through the inorganic fine particles depends on how much the inorganic fine particles cover the surfaces of the magnetic toner particles, that is, the coverage of the inorganic fine particles.

It is considered that when the coverage of the inorganic fine particles is high, the chances of the magnetic toner particles coming into direct contact with the fixing member are reduced, making it difficult for the magnetic toner to adhere to the fixing member.

Furthermore, when the surface coverage of the magnetic toner particles is relatively high, the hardness of the surface is increased, so that the magnetic toner particles are resistant to shear from the outside. It is presumed that this is because the inorganic fine particles present on the surface of the magnetic toner particles cause the surface properties of the magnetic toner particles to approach the properties of the inorganic fine particles rather than the binder resin.

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

In the cross section of the magnetic toner using a transmission electron microscope (TEM), the variation in the occupied area ratio of the magnetic material when the cross section of the magnetic toner is divided by a square grid with one side of 0.8 μm. 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 coefficient of variation 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 in a square grid having a side of 0.8 μm by the division method on the cross section of the magnetic toner.

The fact that the CV3 is within the above range means that the magnetic material is locally unevenly distributed in the magnetic toner particles. That is, by unevenly distributing the magnetic material in the magnetic toner particles, it is possible to appropriately provide a portion where the magnetic material does not exist (hereinafter also referred to as a binder portion between the magnetic materials), and this portion absorbs the share from the outside. It is possible to

For example, in a system such as the above one-component contact development system that requires a large share, the magnetic bodies are locally unevenly distributed compared to the case where the distance between the magnetic bodies is uniform and relatively short, and the binder between the magnetic bodies is used. By providing the portion, the durability of the toner is improved.

As described above, the easiness of deformation of the magnetic toner particles is important, and the deformation of the toner particles is promoted by providing the binder portion between the magnetic bodies. The reason for this is presumed to be that the filler effect of the magnetic material is reduced.

That is, it is speculated that the binder between the magnetic bodies absorbs the share from the outside at the temperature near the developing device during printing, and plays an important role in the deformation of the toner particles during fixing.

When the CV3 is in the above range, cracking of the toner can be easily suppressed when shear is applied from the outside. Therefore, in systems with high market share, such as the one-component contact development method, there are no image defects such as a decrease in image density or development streaks when a large number of images are output, and good images with suppressed fogging can be produced. Obtainable.

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

In this case, the connections between the binder resins become thinner, the brittleness of the magnetic toner particles tends to decrease, and in a system such as a one-component contact development system that requires a high share of the toner, the toner tends to crack and fog due to charging failure. is likely to occur.

In addition, the filler effect of the magnetic material tends to increase, and toner particle deformation tends to be delayed when heat is applied during fixing.

On the other hand, when the CV3 exceeds 80.0%, the magnetic material is excessively localized in the toner. In this case, the magnetic substances aggregate with each other, the surface area is reduced, the coloring strength is lowered, and the image density is lowered.

Examples of methods for adjusting the CV3 within the above range include controlling the hydrophilicity and hydrophobicity 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, in the case of using an emulsion aggregation method, a method of preliminarily aggregating the magnetic material and introducing it into the toner particles, or adding a chelating agent and/or adjusting the pH in the coalescing step can adjust the degree of agglomeration of the magnetic material. methods of adjustment, and the like.

In the cross section of the magnetic toner using a transmission electron microscope (TEM), the magnetic toner is divided by a square grid with a side of 0.8 μm. The average value is preferably 10.0% or more and 40.0% or less. More preferably, it is 15.0% or more and 30.0% or less.

When the average value of the occupied area ratio is within the above range, the state of dispersion of the magnetic material in the toner particles is appropriate, and a decrease in coloring power due to excessive aggregation can be suppressed.

Further, even in a system such as a one-component contact development system in which a high share is applied to the toner, cracking of the toner can be easily suppressed. As a result, fog is less likely to occur, and good images 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 be lowered due to the lowering of the coloring power. On the other hand, when the occupied area ratio exceeds 40.0%, the content of the magnetic material is high, and depending on the dispersion state of the magnetic material, the brittleness of the toner tends to decrease, the toner tends to crack, and fogging tends to occur. .

Methods for controlling the average value of the occupied area ratio of the magnetic substance within the above range include controlling the hydrophilicity and hydrophobicity of the surface of the magnetic substance, and controlling the degree of agglomeration of the magnetic substance during the production of the toner particles. etc.

Generally, in a toner containing a magnetic substance, it is preferable that the magnetic substance is more uniformly contained among toner particles. If there are toner particles with different magnetic substance contents, the chargeability and magnetic performance will be different. In that case, especially in a system with magnetic transport or a system in which development is performed by controlling the chargeability and magnetic performance of the toner, there is a possibility that the behavior during development will differ depending on the toner, resulting in image defects such as a decrease in density. can cause

Further, the brightness of the toner is an index representing the degree of light scattering of the toner, and the brightness of the toner decreases when a substance such as a coloring agent or a magnetic substance that absorbs light is contained.

On the other hand, the luminance dispersion value of toner is an index for determining how much luminance is uneven among toner particles in the measurement of luminance. Therefore, the coefficient of variation of the brightness variance value is an index of how much the brightness varies among toner particles.

The inventors of the present invention have investigated controlling the content ratio of the magnetic substance between the magnetic toner particles. found that it is possible to obtain

Dn (μm) is the number average particle diameter of the magnetic toner,
CV1 (%) is the coefficient of variation of the brightness dispersion value of the magnetic toner in the range of Dn−0.500 or more and Dn+0.500 or less,
When CV2 (%) is the coefficient of variation of the luminance dispersion value of the magnetic toner in the range of Dn-1.500 or more and Dn-0.500 or less,
Said CV1 and said CV2 preferably satisfy the relationship of the following formula (1).
CV2/CV1≤1.00 (1)
The CV2/CV1 is more preferably 0.70 or more and 0.95 or less.

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

The CV2/CV1 can be adjusted by the particle size of the magnetic material and the production conditions in the production of the toner.

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

When CV1 is within the above range, there is little difference in the state of existence of the magnetic material between the toner particles, the image density after continuous image formation is less likely to change, and good images 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 luminance of the magnetic toner at the Dn 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 within the above range, the content of the magnetic material is appropriate, and at the same time good coloring power is exhibited, cracking of the toner can be easily prevented, and the occurrence of fogging can be further suppressed.

The average brightness can be adjusted within the above range by adjusting the content of the magnetic material.

As described above, the adhesive force to the member can be reduced by setting the coverage A of the magnetic toner particle surfaces with the inorganic fine particles within a specific range. Therefore, the coating ratio of the inorganic fine particles and the adhesion to the member were verified.

The relationship between the magnetic toner coverage and the adhesive force to the member was indirectly estimated by measuring the static friction coefficient between the spherical polystyrene particles with different silica fine particle coverage and the aluminum substrate. Specifically, using spherical polystyrene particles (weight average particle diameter (D4) = 7.5 μm) with different silica fine particle coverage (coverage obtained from scanning electron microscope observation), the coverage and static friction A coefficient relationship was obtained.

More specifically, spherical polystyrene particles containing fine silica particles are pressed onto an aluminum substrate. The static friction coefficient was calculated from the stress at that time by moving the substrate left and right while changing the pressure. This is done 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 acting between the spherical polystyrene particles and the substrate and the reflection force. As is clear from the graph, the coefficient of static friction decreases when the coating ratio of the inorganic fine particles is high. This suggests that the magnetic toner with a high coverage has a small adhesive force to the member.

Here, if the coverage A is greater than 80.0%, the action of the wax is likely to be inhibited even in the configuration of the magnetic toner particles, and trailing edge offset is likely to occur.

When the coverage of the inorganic fine particles fixed to the surfaces of the magnetic toner particles is defined as a coverage B (%), the ratio of the coverage B to the coverage A (hereinafter also referred to as B/A) is 0. It is preferably 0.50 or more and 0.85 or less. More preferably, it is 0.55 or more and 0.80 or less.

The coverage A is the coverage including inorganic fine particles that can be easily liberated, and the coverage B indicates the inorganic fine particles adhered to the surface of the magnetic toner particles that are not liberated by the later-described liberation operation. The inorganic fine particles represented by the coverage B are fixed to the surfaces of the magnetic toner particles in a semi-buried state, and do not move on the developing sleeve or on 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 fixed inorganic fine particles and inorganic fine particles present in the upper layer and having a relatively high degree of freedom.

The effect of lowering the van der Waals force and the electrostatic adhesion force as described above is influenced by inorganic fine particles that may exist between the magnetic toner and between the magnetic toner and each member. is considered to be particularly important in this effect.

The fact that the B/A is in the above range means that the inorganic fine particles fixed to the surface of the magnetic toner exist to some extent, and furthermore, the inorganic fine particles are in a state in which they can be easily liberated (a state in which they can move apart from the magnetic toner particles). ), which means that it exists in an appropriate amount. Presumably, the releasable inorganic fine particles slide on the fixed inorganic fine particles, exhibiting an effect like a bearing, and the cohesive force between the magnetic toner particles is greatly reduced.

As a result of studies by the present inventors, the adhesion force reduction effect and the bearing effect described above 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. found to be obtained. Therefore, when calculating the coverage A and the coverage B, attention was focused on inorganic fine particles of 50 nm or less.

By setting the coverage ratio A and B/A within specific ranges, the magnetic toner can reduce the adhesive force between the magnetic toner and each member, and greatly reduce the cohesive force between the magnetic toner. .

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

In addition, by combining the effect of exuding the wax by optimizing the composition of the binder resin and the wax, an efficient anchoring effect to the media can be obtained, and the above effect can be exhibited. As a result, it is possible to greatly reduce the occurrence of toner with insufficient heat conduction even in a configuration where the heat conduction efficiency tends to be low, such as a combination of light pressure fixing using a fixing film and rough paper. can.

The coverage A, the coverage B, and the ratio [B/A] of the coverage B to the coverage A can be obtained by methods described later.

Also, 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. The uniform coverage improves the uniformity of charging of the toner, and even when a large number of images are output, the developability such as image density tends to be stable. In addition, since the surface of the magnetic toner is evenly covered, the cohesive force between the magnetic toner particles can be easily reduced.

The technique for reducing the coefficient of variation to 10.0% or less is not particularly limited. It is good to adjust using the method.

Regarding the coverage ratio of the inorganic fine particles as the external additive, it is possible to derive the coverage by the calculation formula described in Patent Document 4, etc., assuming that the inorganic fine particles and the magnetic toner are spherical. However, there are many cases where the inorganic fine particles and the magnetic toner are not perfectly spherical, and the inorganic fine particles may exist in an aggregated state on the surface of the magnetic toner particles. Not relevant.

Therefore, the present inventors observed the surface of the magnetic toner with a scanning electron microscope (SEM), and determined the coverage ratio at which the inorganic fine particles actually cover the surface of the magnetic toner particles.

As an example, 100 parts by mass of magnetic toner particles (content of magnetic substance: 43.5% by mass) produced by a pulverization method having a volume average particle diameter (Dv) of 8.0 μm is added with an amount of silica fine particles (the number of silica particles added). Theoretical coverage and the actual coverage of the mixed materials were obtained (Figs. 4(a) and 4(b)). As the silica fine particles, silica fine particles having a volume average particle diameter (Dv) of 15 nm were used. Further, when calculating the theoretical coverage, the true specific gravity of the silica fine particles is 2.2 g/cm ³ and the true specific gravity of the magnetic toner is 1.65 g/cm ³ . The particles were monodispersed with a diameter of 15 nm and 8.0 μm.

As is clear from FIG. 4(a), the theoretical coverage exceeds 100% as the number of parts added with silica is increased. On the other hand, the coverage obtained by actual observation varies with the number of parts of silica added, but does not exceed 100%. This is largely due to the fact that the silica fine particles partially exist as aggregates on the surface of the magnetic toner, or that the silica fine particles are not true spheres.

Further, according to the study of the present inventors, it was found that even if the amount of silica fine particles added is the same, the coverage varies depending on the method of external addition. In other words, it is impossible to determine the coverage unequivocally from the amount of inorganic fine particles added (see FIG. 4(b)). In addition, the external addition condition A is obtained by mixing under the conditions of 1.0 W/g and a processing time of 5 minutes using the apparatus shown in FIG. External addition condition B is to mix at 4000 rpm for 2 minutes using an FM mixer FM10C (manufactured by Nippon Coke Kogyo Co., Ltd.).

For this reason, the present inventors used the inorganic fine particle coverage obtained by SEM observation of the magnetic toner surface.

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 and paraffin wax; oxides of aliphatic hydrocarbon waxes such as oxidized polyethylene wax, or block copolymers thereof Waxes mainly composed of fatty acid esters such as carnauba wax and montan acid ester wax, and partially or wholly deoxidized fatty acid esters such as deoxidized carnauba wax; Palmitic acid, stearic acid, montanic acid, etc. unsaturated fatty acids such as brassic acid, eleostearic acid and parinaric acid; saturated alcohols such as stearyl alcohol, aralkyl alcohol, behenyl alcohol, carnauvyl alcohol, ceryl alcohol and mericyl alcohol; sorbitol polyhydric alcohols such as; fatty acid amides such as linoleic acid amide, oleic acid amide, and lauric acid amide; Saturated fatty acid bisamides; unsaturated fatty acid amides such as ethylenebisoleic acid amide, hexamethylenebisoleic acid amide, N,N'dioleyladipic acid amide, N,N'dioleylsebacic acid amide; m-xylene bisstearin aromatic bisamides such as acid amides and N,N' distearyl isophthalic acid amides; aliphatic metal salts such as calcium stearate, calcium laurate, zinc stearate and magnesium stearate (generally called metal soaps); Waxes obtained by grafting vinylic monomers such as styrene and acrylic acid to aliphatic hydrocarbon waxes; partially esterified products of fatty acids and polyhydric alcohols such as behenic acid monoglyceride; obtained by hydrogenating vegetable oils and fats. Such as a methyl ester compound having a hydroxy group that can be

Among these, 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 release effect on the fixing member is improved, and it is easy to suppress trailing edge offset.

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

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

By adjusting the wax content within 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 60°C or higher and 120°C or lower, more preferably 60°C or higher and 90°C or lower.

The wax forms domains inside the magnetic toner particles, and the number average diameter of the domains is 100 nm or more and 500 nm or less. Moreover, 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 long axis of 20 nm or more in the cross section of the magnetic toner particles using a transmission electron microscope (TEM), and measuring the average of the long and short axes. was taken as the domain diameter, and the average value of 30 was taken as the number average diameter of the domain. It should be noted that the selection of domains need not be in the same toner particle.

One factor for effectively suppressing the occurrence of trailing edge offset in the toner fixing step is to reduce the adhesive force to the fixing member.

As a result of studies by the present inventors, it has been found that when the toner particles are deformed, the number-average domain diameter of the domains is within the above range, thereby maximizing the effect of extruding the wax.

When the number average diameter of the domains is less than 100 nm, the crystal structure of the wax becomes fragile. In particular, in a system such as a one-component contact development system in which a high shear is required, the crystal structure of a part of the wax collapses due to long-term shearing of the toner, and the wax is melted. As a result, the wax seeps out onto the surface of the toner particles, causing image defects such as development streaks.

On the other hand, when the number average diameter of the domains exceeds 500 nm, the extruding speed of the wax tends to decrease when the toner is deformed, making it difficult to obtain the release effect from the fixing member.

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

The number average diameter of the domains can be adjusted by the amount of wax added, the diameter of the wax particles in the wax dispersion when the emulsion aggregation method is used as the toner production method, the retention time in the coalescence step, and the like. .

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

Ws is 1.5% or more and 18.0%, where Ws is the area percentage occupied by the wax in a region within 1.0 μm from the contour of the cross section of the magnetic toner particles observed with a transmission electron microscope. The following are preferable. More preferably, it is 2.0% or more and 15.0% or less.

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

As a result, in a system such as a one-component contact development system that requires a high share of toner, it is possible to further suppress fog due to toner cracking and development streaks due to exudation of wax.

The Ws can be adjusted by the amount of wax added and the heat treatment time and heat treatment temperature in the toner manufacturing process. Further, when the emulsion aggregation method is used as the toner production method, it is preferable to control the aggregation speed of the wax and the timing of mixing with other materials.

In the cross section of the magnetic toner particles observed with a transmission electron microscope, the ratio of Wc to Ws (Wc /Ws) is preferably 2.0 or more and 10.0 or less. More preferably, it is 3.0 or more and 8.0 or less.

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

As a result, in a system such as a one-component contact development system that requires a high share of toner, it is possible to further suppress fogging due to toner cracking and development streaks caused by wax seepage, and obtain good images over a long period of time. be able to.

The Wc/Ws can be adjusted by the amount of wax added and the heat treatment time and heat treatment temperature in the toner manufacturing process. Further, when the emulsion aggregation method is used as the toner production method, it is preferable to control the aggregation speed of the wax and the timing of mixing with other materials.

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

Further, the peak molecular weight (Mp) of the main peak measured by gel permeation chromatography (GPC) of the tetrahydrofuran (THF) soluble portion of the magnetic toner is 5000 or more and 12000 or less. Moreover, the peak molecular weight (Mp) of the main peak is preferably 6,000 or more and 11,000 or less.

By setting the resin structure and the peak molecular weight (Mp) in the above range, the deformability of the resin and the exuding effect of the wax can be significantly improved. As a result, the releasability of the magnetic toner from the fixing member is improved, and the adhesiveness to paper (anchoring effect) is relatively increased, thereby suppressing the occurrence of trailing edge offset.

By controlling the peak molecular weight (Mp) to a relatively low molecular weight of 5,000 or more and 12,000 or less, the thermal deformability of the magnetic toner can be increased.

The peak molecular weight (Mp) can be controlled within the above range by appropriately selecting the type of monomer forming the styrene resin described below and by appropriately adjusting the amount of the polymerization initiator.

The styrenic resin is a resin having a styrene-derived monomer unit in the polymer. Examples include styrene and other monomers and copolymers.

Monomers that can be used for the production of styrenic resins include the following monomers in addition to styrene.

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

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

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

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

vinyl esters such as 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 acrylates and alkyl methacrylates (methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, propyl acrylate) having an alkyl group (linear or branched) having 1 to 22 carbon atoms , propyl methacrylate, butyl acrylate, butyl methacrylate, 2-ethylhexyl 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 fumarate (dialkyl fumarate, the two alkyl groups are linear, branched or alicyclic groups having 2 to 8 carbon atoms.) , dialkyl maleate (dialkyl maleate, two alkyl groups are linear, branched or alicyclic groups having 2 to 8 carbon atoms), polyaryloxyalkanes (diaryl oxyethane, triaryloxyethane, tetraallyloxyethane, tetraallyloxypropane, tetraallyloxybutane, tetramethallyloxyethane), vinyl-based monomers having a polyalkylene glycol chain (polyethylene glycol (molecular weight 300) monoacrylate, polyethylene Glycol (molecular weight 300) monomethacrylate, polypropylene glycol (molecular weight 500) monoacrylate, polypropylene glycol (molecular weight 500) monomethacrylate, methyl alcohol ethylene oxide (ethylene oxide is hereinafter abbreviated as EO) 10 mol adduct acrylate, methyl alcohol ethylene Oxide 10 mol adduct methacrylate, Lauryl alcohol EO 30 mol adduct acrylate, Lauryl alcohol EO 30 mol adduct methacrylate rate), polyacrylates and polymethacrylates (polyacrylates and polymethacrylates of polyhydric alcohols: ethylene glycol diacrylate, ethylene glycol dimethacrylate, propylene glycol diacrylate, propylene glycol dimethacrylate, neopentyl glycol diacrylate, neopentyl 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 preferred.

Carboxy group-containing vinyl esters: for example, carboxyalkyl acrylate having an alkyl chain of 3 to 20 carbon atoms and carboxyalkyl methacrylate having an alkyl chain of 3 to 20 carbon atoms can also be used.

Among these, β-carboxyethyl acrylate is preferred.

The styrenic resin may be used singly or in combination of two or more. When two or more types are used together, they may be in the form of a composite resin that is chemically bonded.

The peak molecular weight of the styrene resin is preferably from 5,000 to 12,000, more preferably from 7,000 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 70% by mass or more and 100% by mass or less, more preferably 85% by mass or more and 100% by mass or less.

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

The magnetic material includes iron oxides such as magnetite, maghemite, and ferrite; metals such as iron, cobalt, and nickel; or these metals together with aluminum, copper, magnesium, tin, zinc, beryllium, calcium, manganese, selenium, and titanium. , alloys of metals such as tungsten, vanadium, and mixtures thereof.

The number average particle size 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 material 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 mixture is cured in an atmosphere at a temperature of 40° C. for 2 days to obtain a cured product. The obtained cured product is treated with a microtome as a flaky sample, and an image is taken with a transmission electron microscope (TEM) at a magnification of 10,000 to 40,000 times. Measure the projected area. The equivalent diameter of a circle equal to the projected area is taken as the particle size of the primary particles of the magnetic material, and the average value of the 100 particles is taken as the number average particle size of the primary particles of the magnetic material.

It is preferable that the coercive force (Hc) is 1.6 to 12.0 kA/m as the magnetic properties of the magnetic material when 795.8 kA/m is applied. Also, the magnetization strength (σs) is preferably 50 to 200 Am ² /kg, more preferably 50 to 100 Am 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 35% by mass or more and 50% by mass or less, more preferably 40% by mass or more and 50% by mass or less.

If the content of the magnetic material is within the above range, the magnetic attractive force with the magnet roll in the developing sleeve will be appropriate.

The content of the magnetic substance in the magnetic toner can be measured using a thermal analyzer TGA Q5000IR manufactured by PerkinElmer. The measurement method is to heat the magnetic toner from room temperature to 900°C at a temperature rising rate of 25°C/min in a nitrogen atmosphere, and take the weight loss from 100 to 750°C as the weight of the components of the magnetic toner excluding the magnetic material, and the residual weight. is the amount of magnetic material.

The magnetic material can be produced, 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 equal to or greater than that of the iron component to the ferrous salt aqueous solution. While maintaining the pH of the prepared aqueous solution at 7 or higher, air is blown into the aqueous solution, and the ferrous hydroxide is oxidized while the aqueous solution is heated to 70°C or higher to generate seed crystals that will serve as the core of the magnetic iron oxide. .

Next, an aqueous solution containing about 1 equivalent of ferrous sulfate, based on the amount of alkali added previously, is added to the slurry containing the seed crystals. The pH of the mixed solution is maintained at 5 to 10, and the reaction of ferrous hydroxide is promoted while air is blown into the mixture to grow magnetic iron oxide with the seed crystal as the core. At this time, it is possible to control the shape and magnetic properties of the magnetic material by selecting arbitrary pH, reaction temperature, and stirring conditions. As the oxidation reaction progresses, the pH of the mixed solution shifts to the acidic side, but it is better not to make the pH of the mixed solution less than 5. A magnetic material can be obtained by filtering, washing, and drying the magnetic material thus obtained by a conventional method.

Moreover, the magnetic material may be subjected to a known surface treatment as necessary.

The magnetic toner particles may contain charge control agents. The magnetic toner is preferably negatively charged toner.

As charge control agents for negative charging, organometallic complex compounds and chelate compounds are effective, examples of which include monoazo metal complex compounds, acetylacetone metal complex compounds, and aromatic hydroxycarboxylic acid or aromatic dicarboxylic acid metal complex compounds. be done.

Specific examples of commercially available products include Spilon 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 agent can be used alone or in combination of two or more.

The content of the charge control agent is preferably 0.1 parts by mass or more and 10.0 parts by mass or less with respect to 100 parts by mass of the binder resin from the viewpoint of the charge amount. .0 parts by mass or less is more preferable.

The method for producing the magnetic toner is not particularly limited, and any of a dry method (e.g., kneading pulverization method, etc.) and a wet method (e.g., emulsion aggregation method, suspension polymerization method, dissolution suspension method, etc.) may 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 domains, 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 specific examples.
The emulsion aggregation method is roughly divided into 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 melting and coalescence, and (d) a washing and drying step.

(a) Step of Preparing Fine Particle Dispersion Liquid The fine particle dispersion liquid is obtained by dispersing fine particles in an aqueous medium.
Examples of aqueous media include water such as distilled water and ion-exchanged water, and alcohols. These may be used individually by 1 type, and may use 2 or more types together.
Auxiliary agents for dispersing fine particles in an aqueous medium may be used, and examples of such auxiliary agents include surfactants.
Surfactants include anionic surfactants, cationic surfactants, amphoteric surfactants, and nonionic surfactants.

Specifically, anionic surfactants such as alkylbenzene sulfonates, α-olefin sulfonates, and phosphate esters; alkylamine salts, aminoalcohol fatty acid derivatives, polyamine fatty acid derivatives, amine salt types such as imidazoline, alkyl Quaternary ammonium salt type cationic surfactants such as trimethylammonium salts, dialkyldimethylammonium salts, alkyldimethylbenzylammonium salts, pyridinium salts, alkylisoquinolinium salts, and benzethonium chloride; fatty acid amide derivatives, polyhydric alcohol derivatives amphoteric surfactants such as alanine, dodecyldi(aminoethyl)glycine, di(octylaminoethyl)glycine and N-alkyl-N,N-dimethylammonium betaine.
Surfactants may be used singly or in combination of two or more.
The method for preparing the fine particle dispersion can be appropriately selected according to the type of dispersoid.

For example, there is a method of dispersing the dispersoid using a general dispersing machine such as a rotary shearing homogenizer, a ball mill having media, a sand mill, or a dyno mill. In the case of a dispersoid that dissolves in an organic solvent, a phase inversion emulsification method may be used to disperse the dispersoid in an aqueous medium. In the phase inversion emulsification method, the material to be dispersed is dissolved in an organic solvent in which the material is soluble, and the organic continuous phase (O phase) is neutralized. After that, by adding an aqueous medium (W phase), the resin is converted from W/O to O/W (so-called phase inversion) to form a discontinuous phase and dispersed in the aqueous medium in the form of particles. The method.

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

It is also possible to prepare a fine particle dispersion by forming droplets in an aqueous medium and then polymerizing them, as in emulsion polymerization. Emulsion polymerization is a method of mixing a precursor of a material to be dispersed, an aqueous medium, and a polymerization initiator, followed by stirring or shearing to obtain a fine particle dispersion in which the material is dispersed in the aqueous medium. At this time, an organic solvent or a surfactant may be used as an emulsifying aid. Moreover, a general device may be used as a device for stirring or shearing, and a general dispersing machine such as a rotary shearing homogenizer may be used.

The number average particle diameter of the dispersoids of the fine particle dispersion is preferably 0.01 μm or more and 1 μm or less from the viewpoint of control of aggregation rate and simplicity of coalescence. It is more preferably 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.

From the viewpoint of controlling the aggregation speed, the dispersoid in the fine particle dispersion is preferably 5% by mass or more and 50% by mass or less, and preferably 10% by mass or more and 40% by mass or less. 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 are dispersed.
The mixing method is not particularly limited, and mixing can be performed using a general stirrer.
Aggregation is controlled by temperature, pH, aggregating agent, etc. of the aggregated particle dispersion, and any method may be used.
Regarding the temperature for forming aggregated particles, it is preferable that the glass transition temperature of the binder resin is −30° C. or more and the glass transition temperature or less.

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

A water-soluble chelating agent may be used as the chelating agent. Specific examples of chelating agents include oxycarboxylic acids such as tartaric acid, citric acid and gluconic acid, iminodiacid (IDA), nitrilotriacetic acid (NTA), and ethylenediaminetetraacetic acid (EDTA). The amount of the chelating agent added is, for example, preferably 0.01 parts by mass or more and 5.0 parts by mass or less, and 0.1 parts by mass or more and 3.0 parts by mass or less with respect to 100 parts by mass of the resin particles. It is more preferable to have

The timing of mixing the fine particle dispersion is not particularly limited, and the fine particle dispersion may be further added after or during formation of the aggregated particle dispersion to cause aggregation.
By controlling the addition timing of the fine particle dispersion, it is possible to control the structure in the toner.
Aggregation is preferably stopped when the aggregated particles reach the target particle size.

Aggregation can be stopped by dilution, temperature control, pH control, addition of a chelating agent, addition of a surfactant, etc. Addition of a chelating agent is preferred from the standpoint of production. A more preferable method is 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 together, toner particles in which the magnetic material is slightly aggregated can be formed after the subsequent coalescence step.

(c) Coalescing Process After the aggregated particles are formed, they are heated to melt and coalesce to form toner particles.
The heating temperature is preferably 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 then (b) a step of forming aggregated particles, and (c) a melting and coalescing step are performed to form toner particles having a core/shell structure. You may let

(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, from the viewpoint of electrification, it is preferable to sufficiently perform displacement washing with ion-exchanged water. From the viewpoint of productivity, the solid-liquid separation step may be performed by suction filtration, pressure filtration, or the like. In addition, from the viewpoint of productivity, the drying step may be performed by freeze drying, flash jet drying, fluidized drying, vibrating fluidized drying, or the like.

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 fine particles 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. . Moreover, it is preferable that 90% by mass or more of the inorganic oxide fine particles are silica fine particles.

This is because silica fine particles not only have the best balance in terms of imparting chargeability and fluidity, but also excel in terms of reducing the cohesive force between toner particles.

It is not clear why silica fine particles are superior in terms of reducing the cohesive force between toner particles, but it is presumed that the above-mentioned bearing effect has a large effect on the slippage between silica fine particles. doing.

On the other hand, it is preferable that the inorganic fine particles adhered to the surfaces of the magnetic toner particles are mainly composed of silica fine particles. Specifically, the inorganic fine particles fixed to the surfaces 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. 80% by mass or more of is preferably silica fine particles. More preferably, 90% by mass or more is fine silica particles.

The reason for this is presumed to be the same as the above. Silica fine particles are the most excellent in terms of imparting chargeability and fluidity, which makes the charging of the magnetic toner quicker. As a result, high image density can be obtained.

Here, in order to make 85 mass % or more of the inorganic oxide fine particles present on the magnetic toner particle surfaces to be the silica fine particles and 80 mass % or more of the inorganic oxide particles fixed to the magnetic toner particle surfaces be the silica fine particles. , the amount and timing of addition of the inorganic fine particles may be adjusted.
In addition, it is possible to confirm the amount of existence by the method of quantifying the inorganic fine particles, which will be described later.

The number average particle size of the primary particles of the inorganic fine particles is preferably 5 nm or more and 50 nm or less, more preferably 10 nm or more and 35 nm or less.

When the number average particle diameter of the primary particles of the inorganic fine particles is within the above range, the coverage ratios A, B/A, and the coefficient of variation of the coverage ratio A can be easily controlled within the above appropriate ranges. Easier to get the effect.

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

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

Examples of the organosilicon compound include hexamethyldisilazane, trimethylsilane, trimethylethoxysilane, isobutyltrimethoxysilane, trimethylchlorosilane, dimethyldichlorosilane, methyltrichlorosilane, dimethylethoxysilane, dimethyldimethoxysilane, diphenyldiethoxysilane, hexamethyl and disiloxane. These are used singly or as a mixture of two or more.

Examples of the silicone oil include dimethylsilicone oil, methylphenylsilicone oil, α-methylstyrene-modified silicone oil, chlorophenylsilicone oil, and fluorine-modified silicone oil.

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

Among these, straight-chain saturated fatty acids having 10 to 22 carbon atoms are preferable because they facilitate uniform treatment of the surfaces of inorganic fine particles.

The linear saturated fatty acids include capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, arachidic acid, and behenic acid.

Among the inorganic fine particles, silica fine particles are preferably treated with silicone oil, and more preferably silica fine particles are treated with an organic silicon compound and silicone oil because the degree of hydrophobicity can be suitably controlled.

Examples of the method of treating silica fine particles with silicone oil include a method of directly mixing inorganic fine particles treated with an organic silicon compound and silicone oil using a mixer such as an FM mixer, and a method of spraying silicone oil onto inorganic fine particles. method. Alternatively, a method of dissolving or dispersing the silicone oil in a suitable solvent, adding and mixing the inorganic fine particles, and removing the solvent may also be used.

In order to obtain good hydrophobicity, the treatment amount of silicone oil is preferably 1 part by mass or more and 40 parts by mass or less, and 3 parts by mass or more and 35 parts by mass or less with respect to 100 parts by mass of 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 the BET method by nitrogen adsorption is preferably 20 m ² /g or more and 350 m ² /g or less. . 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 is preferably measured according to JIS Z8830 (2001).

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

Here, the amount of silica fine particles to be added is preferably 1.5 parts by mass or more and 3.0 parts by mass or less with respect to 100 parts by mass of the magnetic toner particles. It is more preferably 1.5 parts by mass or more and 2.6 parts by mass or less, and still more preferably 1.8 parts by mass or more and 2.6 parts by mass or less.

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

As a mixing processing device for externally adding and mixing the inorganic fine particles, a known mixing processing device can be used. A device as shown in (a) is preferred.

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

Since the mixing processing apparatus is configured such that the magnetic toner particles and the inorganic fine particles are sheared in the narrow clearance portion, the inorganic fine particles are easily adhered to the surfaces of the magnetic toner particles.

Furthermore, as will be described later, the magnetic toner particles and the inorganic fine particles are easily circulated in the axial direction of the rotating body, and are easily mixed sufficiently and uniformly before adhesion proceeds. It is easy to control the coefficient of variation of A within the above range.

On the other hand, FIG. 3(b) is a schematic diagram showing an example of the configuration of a stirring member used in the mixing processing apparatus.

The step of externally adding and mixing the inorganic fine particles will be described below with reference to FIGS.

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

The gap (clearance) between the inner peripheral portion of the main casing 1 and the stirring member 3 is kept constant and small in order to give a uniform share to the magnetic toner particles and to facilitate the adhesion of the inorganic fine particles to the surfaces of the magnetic toner particles. Good.

Further, in this device, 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 rotor 2 . In FIG. 3A, 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 of the rotating body 2 excluding the stirring member 3). indicates 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 the force acts on the magnetic toner particles is appropriately limited. impact force is applied to

Also, the clearance may be adjusted according to the size of the main body casing. If the diameter is about 1% or more and 5% or less of the diameter of the inner peripheral portion of the main body casing 1, the magnetic toner particles can be sufficiently sheared. Specifically, when the diameter of the inner peripheral portion of the main body casing 1 is about 130 mm, the clearance is set to about 2 mm or more and 5 mm or less, and when the diameter of the inner peripheral portion of the main body casing 1 is about 800 mm, the clearance is set to 10 mm or more and 30 mm or less. It should be to some extent.

In the step of externally adding and mixing the inorganic fine particles, the magnetic toner particles and the inorganic fine particles put into the mixing processing device are stirred and mixed by rotating the rotating body 2 by the driving unit 8 using the mixing processing device. Inorganic fine particles are externally added and mixed on the surface of the particles.

As shown in FIG. 3(b), at least some of the plurality of stirring members 3 are stirring for feeding that feeds magnetic toner particles and inorganic fine particles in one direction along the axial direction of the rotating body 2 as the rotating body 2 rotates. It is formed as member 3a. At least some of the plurality of stirring members 3 are formed as return stirring members 3b that return the magnetic toner particles and inorganic fine particles in the other axial direction of the rotating body as the rotating body 2 rotates. .

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 casing 1, the direction from the raw material inlet 5 to the product outlet 6 ( The rightward direction in FIG. 3(a) is referred to as the "feed direction".

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

As a result, while repeating feeding (13) in the "feeding direction" and feeding (12) in the "returning direction", the surfaces of the magnetic toner particles are externally added and mixed with the inorganic fine particles.

Further, 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. As shown in FIG. In the example shown in FIG. 3(b), the stirring members 3a and 3b are arranged on the rotating body 2 at an interval of 180 degrees to form a set of two members. A large number of members may be set as one set, such as four members at intervals of .

In the example shown in FIG. 3B, a total of 12 stirring members 3a and 3b are formed at regular intervals. Furthermore, in FIG. 3(b), 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 feeding the magnetic toner particles and the inorganic fine particles in the feed direction and the return direction, D should be about 20% or more and 30% or less of the length of the rotating body 2 in FIG. 3B. is preferred. FIG. 3B shows an example of 23%. Further, 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 when an extension line is drawn in the vertical direction from the end position of the stirring member 3a. Thereby, it is possible to efficiently apply shear to the magnetic toner particles and the inorganic fine particles. It is preferable that d with respect to D is 10% or more and 30% or less in order to increase the share.

As for the shape of the blade, it is possible to send the magnetic toner particles and the inorganic fine particles in the feed direction and the return direction in addition to the shape shown in FIG. 3(b). As long as the clearance can be maintained, a shape having a curved surface or a paddle structure in which the tip blade portion is coupled to the rotating body 2 with a rod-like arm may be used.

A more detailed description will be given below with reference to the schematic diagrams of the apparatus shown in FIGS. 3(a) and 3(b). The apparatus shown in FIG. 3(a) includes a rotating body 2 having at least a plurality of stirring members 3 installed on its surface,
a drive unit 8 that rotationally drives the rotating body 2;
a main body casing 1 provided with a gap from the stirring member 3;
A jacket 4 which is located inside the main body casing 1 and on the end side 10 of the rotating body and which allows a cooling medium to flow.
have.

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

Further, in the apparatus shown in FIG. 3(a), an inner piece 16 for raw material inlet is inserted into raw material inlet 5, and an inner piece 17 for product outlet is inserted into product outlet 6. there is

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

As for the order of charging, the inorganic fine particles may be charged from the raw material charging port 5 first, and then the magnetic toner particles may be charged from the raw material charging port 5 . Alternatively, the magnetic toner particles and the inorganic fine particles may be mixed in advance with a mixer such as a Henschel mixer, and then the mixture may be introduced through the raw material inlet 5 of the apparatus shown in FIG. 3(a).

More specifically, as the external additive mixing treatment condition, the power of the drive unit 8 is controlled to 0.2 W/g or more and 2.0 W/g or less. is preferable from the viewpoint of adjusting the coefficient of variation of to the above range. Further, it is more preferable to control the power of the drive unit 8 to be 0.6 W/g or more and 1.6 W/g or less.

Although the treatment time is not particularly limited, it is preferably 3 minutes or more and 10 minutes or less.

The rotational speed of the stirring member during external mixing is not particularly limited. In the device shown in FIG. 3(a), the volume of the processing space 9 is 2.0×10 ⁻³ m ³ , and the rotation speed of the stirring member when the shape of the stirring member 3 is as shown in FIG. 3(b). is preferably 1000 rpm or more and 3000 rpm or less. By adjusting the rotational speed within this range, it becomes easier to adjust the coverage ratios A, B/A, and the coefficient of variation of the coverage ratio A within the ranges described above.

Furthermore, a pre-mixing step may be provided before the external addition mixing treatment 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 coefficient of variation of the coverage A can be more easily reduced.

More specifically, as pre-mixing processing conditions, the power of the drive 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 is taken out from the product discharge port 6 , and the rotating body 2 is rotated by the drive unit 8 to discharge the magnetic toner from the product discharge port 6 . Coarse particles and the like may be separated from the obtained magnetic toner by a sieving machine such as a circular vibrating sieving machine, if necessary, to obtain a magnetic toner.

In addition to the inorganic fine particles, particles having a primary particle number average particle size of 80 nm or more and 3 μm or less may be added to the magnetic toner as long as the effect of the present invention is not affected. Examples of the particles include lubricants such as fluororesin powder, zinc stearate powder and polyvinylidene fluoride powder; 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 within the above range, it is possible to sufficiently satisfy the reproducibility of dots while improving the handleability of the toner.

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

The average circularity of the magnetic toner is preferably from 0.960 to 1.000, more preferably from 0.970 to 1.000.

When the average circularity is within the above range, even in a system requiring a high share such as a one-component contact development system, the toner is less likely to be densified and the fluidity of the toner is easily maintained. As a result, when a large number of images are output, it is possible to further suppress the decrease in image density and the occurrence of development streaks in the latter half.

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

The image forming method of the present invention comprises
a charging step of externally applying a voltage to the charging member 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 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 bearing member to a transfer material with or without an intermediate transfer member;
An image forming method including a fixing step of fixing a toner image transferred to a transfer material by heating and pressurizing means,
The developing step is a one-component contact development system in which the electrostatic latent image bearing member and the toner carried on the toner bearing member are brought into direct contact with each other for development,
the toner is
A magnetic toner containing magnetic toner particles containing a binder resin, a magnetic substance and wax, and inorganic fine particles present on the surfaces of the magnetic toner particles,
In a 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,
When the surface coverage of the magnetic toner particles with the inorganic fine particles is defined as a coverage A (%), the coverage A is 45.0% or more and 80.0% or less,
the wax forms domains inside the magnetic toner particles, and the number average diameter of the domains is 100 nm or more and 500 nm or less;
The binder resin contains a styrene-based resin,
A tetrahydrofuran-soluble portion of the magnetic toner has a main peak molecular weight of 5,000 or more and 12,000 or less measured by gel permeation chromatography.

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 (abutting arrangement), and these carriers transport toner by rotating. A large share is applied to the contact portion between the toner carrier and the electrostatic latent image carrier. Therefore, in order to obtain high-quality images, the toner preferably has high durability and high fluidity.

On the other hand, as a developing method, the one-component developing method allows a smaller cartridge containing the developer than the two-component developing method using a carrier.

Further, the contact development method can obtain high-quality images with less toner scattering. In other words, the one-component contact developing system, which has both of the above, can achieve both the miniaturization of the developing device and the improvement of image quality.

The one-component contact development system will be described in detail below with reference to the drawings.

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

In FIG. 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 the arrow R2, the toner 57 is conveyed to the 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 .

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 around the electrostatic latent image carrier 45 . The electrostatic latent image carrier 45 is charged by a charging roller 46 . Then, the electrostatic latent image carrier 45 is exposed by irradiating the electrostatic latent image carrier 45 with laser light from the laser generator 54 to form an electrostatic latent image corresponding to the desired image. The electrostatic latent image on the electrostatic latent image carrier 45 is developed with 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. Transfer of the toner image to the transfer material may occur via an intermediate transfer member. A transfer material (paper) 53 carrying a toner image is carried to a fixing device 51 and fixed on the transfer material (paper) 53 . A portion of the toner 57 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 through the toner to regulate the thickness of the toner layer on the toner carrier. By doing so, it is possible to obtain a high image quality without defective regulation. A regulating blade is generally used as the toner regulating member that contacts the toner carrier.

The upper side of the regulating blade is fixed to the developing device, and the lower side of the regulating blade is bent in the forward or reverse direction of the toner carrier against the elastic force of the blade. should be brought into contact with an appropriate elastic pressing force.

For example, as shown in FIG. 1, one free end of the toner regulating member 55 is sandwiched between two fixing members (for example, metal elastic bodies, reference numeral 56 in FIG. 1) to fix the toner regulating member 55 to the developing device. It should be fixed with fasteners.

Methods for measuring each physical property value according to the present invention are described below.

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

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

After mixing, the mixture is pelletized in the same manner as above, and the strength of Si is determined in the same manner as above (Si strength-2). A similar operation is performed to obtain the strength of Si (Si strength-3, Si strength-4) for samples in which 2.0% by mass and 3.0% by mass of silica fine particles are added and mixed with respect to the magnetic toner. Using Si intensity-1 to Si intensity-4, the silica content (% by mass) in the magnetic toner is calculated by the standard addition method.

The titania content (% by mass) and the alumina content (% by mass) in the magnetic toner are quantified by the standard addition method in the same manner as the above quantification of the silica content. That is, the titania content (% by mass) can be quantified by adding and mixing fine titania particles having a primary particle number average particle size 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 fine alumina particles having a primary particle number average particle size 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 plastic cup with a lid using a precision balance, 100 mL of methanol is added, and dispersed for 5 minutes with an ultrasonic disperser. Magnetic toner is attracted by a neodymium magnet and the supernatant liquid is discarded. The operation of dispersing with methanol and discarding the supernatant is repeated three times. After that, add 100 mL of 10% NaOH and "Contaminon N" (a 10% by mass aqueous solution of a neutral detergent for cleaning precision measuring instruments at pH 7 consisting of a nonionic surfactant, an anionic surfactant, and an organic builder, Wako Pure Chemical Industries, Ltd. (manufactured by Kogyo Co., Ltd.) and mix gently. It is then left to stand for 24 hours. After that, they are separated again using a neodymium magnet. In addition, at this time, rinsing with distilled water is repeated so that NaOH does not remain. The collected particles are sufficiently dried with 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 are placed in an aluminum ring with a diameter of 30 mm, pellets are produced under a pressure of 10 tons, and the intensity of Si is determined by wavelength dispersive X-ray fluorescence analysis (XRF). (Si intensity -5). Using Si intensity-5 and Si intensity-1 to Si intensity-4 used in the determination of the silica content in the magnetic toner, the silica content (% by mass) in the particles A is calculated.

(4) Separation of Magnetic Substance from Magnetic Toner To 5 g of particles A, 100 mL of tetrahydrofuran is added, mixed well, and then ultrasonically dispersed for 10 minutes. Attract the magnetic particles with a magnet and discard the supernatant. Particles B are obtained by repeating this operation five times. By this operation, almost all organic components such as resins other than the magnetic material can be removed. However, since tetrahydrofuran-insoluble matter 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 the particles C obtained after heating can be approximated to the magnetic material 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 oxidized increase of the magnetic material.

(5) Measurement of Ti Intensity and Al Intensity in Separated Magnetic Substance A magnetic substance may contain Ti and Al as impurities or additives. The amount of Ti and Al derived from the magnetic material can be detected by the FP quantification method of wavelength dispersive X-ray fluorescence spectroscopy (XRF). The detected Ti amount and Al amount are converted into titania and alumina to calculate the titania and alumina contents in the magnetic material.

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 by substituting each quantitative value obtained by the above method into the following equations.

Amount of external silica fine particles (% by mass) = Silica content in magnetic toner (% by mass) - Silica content in particles 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) Calculating the proportion of silica fine particles in inorganic oxide fine particles selected from the group consisting of silica fine particles, titania fine particles, and alumina fine particles, among the inorganic fine particles fixed to the surfaces of the magnetic toner particles.

In the method for calculating the coverage rate B, which will be described later, after drying the toner after performing the “removal of unfixed inorganic fine particles” operation, the same operations as in the above methods (1) to (5) are performed. It is possible to calculate the proportion of silica fine particles in the inorganic oxide fine particles.

<Method for Measuring Volume Average Particle Diameter (Dv) and Number Average Particle Diameter (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 precision particle size distribution measuring device "Coulter Counter Multisizer 3" (registered trademark, manufactured by Beckman Coulter, Inc.) using a pore electrical resistance method equipped with a 100 μm aperture tube is used. The attached dedicated software "Beckman Coulter Multisizer 3 Version 3.51" (manufactured by Beckman Coulter, Inc.) is used for setting the measurement conditions and analyzing the measurement data. The measurement is performed with 25,000 effective measurement channels.

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

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

In the "change standard measurement method (SOM) screen" of the dedicated software, set the total number of counts in control mode to 50000 particles, set the number of measurements to 1, and set the Kd value to "standard particle 10.0 μm" (Beckman Coulter Co., Ltd. (manufactured) to set the value obtained using By pressing the "threshold/noise level measurement button", the threshold and noise level are automatically set. Also, set the current to 1600 μA, the gain to 2, the electrolytic aqueous solution to ISOTON II, and put a check in the “Flush aperture tube after measurement” box.

In the "pulse-to-particle size conversion setting screen" of the dedicated software, set the bin interval to logarithmic particle size, the particle size bin to 256 particle size bins, and the particle size range from 2 μm to 60 μm.

A specific measuring method is as follows.

(1) About 200 mL of the electrolytic aqueous solution is placed in a 250 mL glass round-bottomed beaker exclusively for Multisizer 3, set on a sample stand, and stirred counterclockwise at 24 rpm with a stirrer rod. Then, remove the dirt and air bubbles inside the aperture tube using the dedicated software's "Flush Aperture Tube" function.

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

(3) Prepare an ultrasonic disperser "Ultrasonic Dispersion System Tetora 150" (manufactured by Nikkaki Bios Co., Ltd.) having an electrical output of 120 W and incorporating two oscillators with an oscillation frequency of 50 kHz with a phase shift of 180°. About 3.3 L of ion-exchanged water is placed in the water tank of the ultrasonic disperser, and about 2 mL of Contaminon 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 resonance state of the liquid surface of the electrolytic aqueous solution in the beaker is maximized.

(5) While the electrolytic aqueous solution in the beaker in (4) above is being irradiated with ultrasonic waves, about 10 mg of toner is added little by little to the electrolytic aqueous solution and dispersed. Then, the ultrasonic dispersion treatment is continued for another 60 seconds. The ultrasonic dispersion is appropriately adjusted so that the temperature of the water in the water tank is 10°C or higher and 40°C or lower.

(6) The electrolytic aqueous solution of (5) above, in which the toner is dispersed, is dropped into the round-bottomed beaker of (1) above set in the sample stand, and adjusted so that the measured concentration is about 5%. . The measurement is continued until the number of measured particles reaches 50,000.

(7) Analyze the measurement data with the dedicated software attached to the apparatus, and calculate the volume average particle size (Dv) and the number average particle size (Dn). The "50% D diameter" on the "analysis/volume statistical value (arithmetic mean)" screen when graph/volume % was set using the dedicated software was taken as the volume average particle diameter (Dv). The "arithmetic diameter" on the "analysis/number statistical value (arithmetic mean)" screen when graph/number % was set on the dedicated software was taken as the number average particle diameter (Dn).

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

A specific measuring method is as follows.

First, about 20 mL of ion-exchanged water, from which solid impurities have been removed in advance, is placed in a glass container. As a dispersant, "Contaminon N" (a 10% by mass aqueous solution of a neutral detergent for cleaning precision measuring instruments at pH 7 consisting of a nonionic surfactant, an anionic surfactant, and an organic builder, manufactured by Wako Pure Chemical Industries, Ltd.) was used as a dispersant. ) is diluted with ion-exchanged water to about 3 times the mass, and about 0.2 mL of the diluted solution is added. Further, about 0.02 g of a measurement sample is added, and dispersion treatment is performed for 2 minutes using an ultrasonic disperser to obtain a dispersion liquid for measurement. At that time, the temperature of the dispersion liquid is appropriately cooled to 10° C. or higher and 40° C. or lower. As the ultrasonic disperser, a desktop ultrasonic cleaner "VS-150" (manufactured by Vervoclea) with an oscillation frequency of 50 kHz and an electrical output of 150 W was used, and a predetermined amount of ion-exchanged water was placed in the water tank. , add about 2 mL of the contaminon N into this water bath.

For the measurement, the above-mentioned flow-type particle image measuring apparatus equipped with "LUCPLFLN" (magnification 20 times, numerical aperture 0.40) was used as the objective lens, and particle sheath "PSE-900A" (manufactured by Sysmex Corporation) was used as the sheath liquid. to use. The dispersion liquid prepared according to the above procedure is introduced into the flow type particle image measuring apparatus, and 2000 magnetic toner particles are measured in the HPF measurement mode and the total count mode. From the results, the average brightness of the magnetic toner, the brightness dispersion value and its coefficient of variation, and the average circularity are calculated.

The average brightness at Dn of the magnetic toner is obtained by dividing the equivalent circle diameter of the flow type particle image analyzer by Dn-0.500 (μm) or more and Dn+0. It is a value obtained by calculating the average luminance limited to the range of 500 (μm) or less.

CV1 is obtained by measuring the number average particle diameter (Dn) of the magnetic toner in the measurement result of the luminance dispersion value, and the circle equivalent diameter of the flow type particle image measuring device is Dn-0.500 (μm) or more. The range is limited to Dn+0.500 (μm) or less. Then, it is a value obtained by calculating the variation coefficient of the brightness variance value.

CV2 is obtained by measuring the number average particle diameter (Dn) of the magnetic toner in the measurement result of the luminance dispersion value, and the circle equivalent diameter of the flow type particle image measuring device is Dn-1.500 (μm) or more. Limited to Dn-0.500 (μm) or less. Then, it is a value obtained by calculating the variation coefficient of the brightness variance value.

In the measurement, automatic focus adjustment is performed using standard latex particles (“RESEARCH AND TEST PARTICLES Latex Microsphere Suspensions 5100A” manufactured by Duke Scientific, diluted with deionized water) before starting the measurement. After that, it is preferable to perform focus adjustment every two hours from the start of measurement.

In this case, we use a flow-type particle image analyzer that has been calibrated by Sysmex and has received a calibration certificate issued by Sysmex.

Except for limiting the analyzed particle diameter to a 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 was received.

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

Heating rate: 10°C/min
Measurement start temperature: 20°C
Measurement end temperature: 180°C
The melting points of indium and zinc are used to correct the temperature of the device detector, and the heat of fusion of indium is used to correct the amount of heat.

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

<Method for measuring glass transition temperature (Tg)>
The glass transition temperature of a resin or the like is measured in the vertical axis direction from a straight line obtained by extending the baseline before and after the change in specific heat in the reversing heat flow curve during temperature rise obtained by differential scanning calorimetry of the melting point. is the temperature (° C.) at the intersection of a straight line equidistant to , and the curve of the step change portion of the glass transition in the reversing heat flow curve.

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

(1) Preparation of measurement sample A sample and tetrahydrofuran (THF) are mixed at a concentration of 5.0 mg/mL, left at room temperature for 5 to 6 hours, and then shaken sufficiently to combine THF and the sample. Mix well until there are no lumps. Furthermore, it is allowed to stand at room temperature for 12 hours or more. At this time, the tetrahydrofuran (THF)-soluble portion of the sample is obtained by setting the time from the start of mixing of the sample and THF to the end of standing to be 72 hours or longer.

Then, it is filtered through a solvent-resistant membrane filter (pore size: 0.45 to 0.50 μm, Myshoridisc H-25-2 [manufactured by Tosoh Corporation]) to obtain a sample solution.

(2) Measurement of sample Using the obtained sample solution, measure under the following conditions.

Apparatus: High-speed GPC apparatus LC-GPC 150C (manufactured by Waters)
Column: 7 columns of Shodex GPC KF-801, 802, 803, 804, 805, 806, 807 (manufactured by Showa Denko) 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 types of monodisperse polystyrene standard samples and the number of counts.

As a standard polystyrene sample for preparing a calibration curve, Pressure Chemical Co. or Toyo Soda Kogyo Co., Ltd., molecular weights 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. The peak molecular weight of the main peak refers to the maximum peak in the obtained molecular weight distribution.

<Method for measuring the particle diameter of the dispersion in the fine particle dispersion>
The particle size of each fine particle dispersion liquid is measured using a laser diffraction/scattering particle size distribution analyzer. Specifically, it is measured according to JIS Z 8825-1 (2001).

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

Dedicated software "HORIBA LA-920 for Windows (registered trademark) WET (LA-920) Ver.2.02" attached to LA-920 is used for setting measurement conditions and analyzing measurement data. As the measurement solvent, ion-exchanged water from which impure solids and the like have been previously removed is used. The measurement procedure is as follows.

(1) Attach the batch type cell holder to LA-920.
(2) Put a predetermined amount of ion-exchanged water in a batch-type cell, and set the batch-type cell in a batch-type cell holder.
(3) Stir the inside of the batch-type cell using a dedicated stirrer tip.
(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 to the volume standard.
(6) After performing warm-up operation for 1 hour or longer, perform optical axis adjustment, fine adjustment of the optical axis, and blank measurement.
(7) Put 3 mL of the fine particle dispersion into a 100 mL flat-bottom glass beaker. Further, 57 mL of ion-exchanged water is added to dilute the fine resin particle dispersion. As a dispersant, "Contaminon N" (a 10% by mass aqueous solution of a neutral detergent for cleaning precision measuring instruments at pH 7 consisting of a nonionic surfactant, an anionic surfactant, and an organic builder, Wako Pure Chemical Industries, Ltd.) was used as a dispersant. ) is diluted with ion-exchanged water to 3 times the mass, and 0.3 mL of the diluted solution is added.
(8) Prepare an ultrasonic disperser "Ultrasonic Dispersion System Tetora 150" (manufactured by Nikkaki Bios Co., Ltd.) with an electrical output of 120 W and two oscillators with an oscillation frequency of 50 kHz built in with a phase shift of 180 degrees. 3.3 L of deionized water is placed in the water tank of the ultrasonic disperser, and 2 mL of Contaminon N is added to this 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) Continue the ultrasonic dispersion treatment for 60 seconds. Also, in ultrasonic dispersion, the temperature of the water in the water tank is appropriately adjusted to 10° C. or higher and 40° C. or lower.
(11) The fine particle dispersion liquid prepared in (10) above is immediately added to the batch-type cell little by little while taking care not to introduce air bubbles so that the transmittance of the tungsten lamp is 90% to 95%. adjust. Then, the particle size distribution is measured. Based on the obtained volume-based particle size distribution data, the particle size of the dispersion in the fine particle dispersion is calculated.

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

The magnetic toner was embedded in a visible light curable embedding resin (D-800, manufactured by Nisshin EM), cut to a thickness of 60 nm with an ultrasonic ultramicrotome (EM5, manufactured by Leica), and subjected to a vacuum dyeing apparatus (Filgen). company) for Ru staining.

After that, using a transmission electron microscope (H7500, manufactured by Hitachi High-Technology Co., Ltd.), the cross section of the obtained magnetic toner particles is observed at an accelerating voltage of 120 kV.

Ten magnetic toner particles within ±2.0 μm from the number-average particle size of the magnetic toner particles are selected and photographed to obtain a cross-sectional image.

A crystalline material such as wax is less dyed with Ru than an amorphous resin, and appears white in the TEM cross-sectional image.

<Method for calculating number average diameter of domains of wax>
The number average diameter of the wax domains is obtained by randomly selecting 30 wax domains having a major axis of 20 nm or more in the cross-sectional image, and taking the average value of the major and minor axes as the domain diameter, and calculating the average value of the 30 domains. It is the number-average diameter of domains. It should be noted that the selection of domains need not be in the same magnetic toner particle.

<How to calculate Ws and Wc>
The wax distribution state in the magnetic toner is evaluated by calculating Ws and Wc from the area of the wax domain in the cross-sectional image, and averaging 10 arbitrarily selected magnetic toners. Using image processing software (Photoshop 5.0, manufactured by Adobe), the cross-sectional image is subjected to “two-gradation” processing in “color tone correction”.

The threshold is set to an offset gradation on the low gradation side of the gradation peak indicating the binder resin in the gradation distribution of 255 gradations of the image. This two-gradation processing provides an image in which the wax domain and the binder resin region are clearly distinguished.

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

On the other hand, the occupied area percentage of wax domains having a major axis of 20 nm or more in the internal region more than 1.0 μm from the contour of the cross section is calculated as the wax occupied area percentage, and this is defined as Wc.

<Method for Calculating Occupied Area Ratio of Magnetic Substance in Magnetic Toner and Its Variation Coefficient (CV3)>
The occupied area ratio of the magnetic substance in the magnetic toner and its coefficient of variation (CV3) are calculated as follows.

First, a cross-sectional image 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 based on the division method for the obtained cross-sectional image.

Furthermore, the variation coefficient of the occupied area ratio of each division grid obtained is calculated and set as the occupied area ratio variation coefficient (CV3).

Specifically, first, the magnetic toner is compression-formed into a tablet. A tablet forming machine with a diameter of 8 mm is filled with 100 mg of magnetic toner, and a force of 35 kN is applied to it and allowed to stand still for 1 minute to obtain tablets.

The resulting tablet is cut with an ultrasonic ultramicrotome (Leica, UC7) to obtain a slice sample with a film thickness of 250 nm.

An STEM image is taken of the obtained flake sample using a transmission electron microscope (JEOL, JEM2800).

Assume that the probe size used for photographing the 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, Brightness to 3750, Contrast of the Image Control panel to 0.0, Brightness to 0.5, and Gammma to 1.00, only the magnetic material portion can be shot in the dark. With this setting, a STEM image suitable for image processing can be obtained.

The obtained STEM image is digitized using an image processing apparatus (Nireco Corporation, LUZEX AP).

Specifically, a frequency histogram of the occupied area ratio of the magnetic material on a square grid with one side of 0.8 μm is obtained by the division method. At this time, the class interval of the histogram is set to 5%.

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

<Method for calculating coverage A>
The coverage A was obtained by analyzing a magnetic toner surface image taken with a Hitachi ultra-high-resolution field emission scanning electron microscope S-4800 (Hitachi High-Technologies Corporation) using image analysis software Image-Pro Plus ver. 5.0 (Nippon Roper Co., Ltd.). The imaging conditions for the S-4800 are as follows.

(1) Sample Preparation A sample stage (aluminum sample stage 15 mm×6 mm) is thinly coated with conductive paste, and magnetic toner is sprayed thereon. Further, air blowing is performed to remove excess magnetic toner from the sample table, and the sample table is sufficiently dried. A sample stage is set on the sample holder, and the height of the sample stage is adjusted to 36 mm using the sample height gauge.

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

The anti-contamination trap attached to the S-4800 housing is flooded with liquid nitrogen and left for 30 minutes. Start the "PC-SEM" of the S-4800 and perform flushing (cleaning of the FE chip, which is the electron source). Click the acceleration voltage display part of 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 flashing is 20 to 40 μA. Insert the sample holder into the sample chamber of the S-4800 housing. Press [Origin] on the control panel to move the sample holder to the observation position.

Click the acceleration voltage display 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], select [Upper (U)] and [+BSE] for the SE detector, and select [ L. A. 100] to set the mode for observing backscattered electron images. Similarly, in the [Basic] tab of the operation panel, set the probe current in the electron optical system condition block to [Normal], the focus mode to [UHR], and the WD 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 Size of Magnetic Toner Drag the inside of the magnification display section of the control panel to set the magnification to 5000 (5k) times. Rotate the focus knob [COARSE] on the operation panel, and adjust the aperture alignment when the focus is achieved to some extent. Click [Align] in the control panel to display the alignment dialog and select [Beam]. Rotate the STIGMA/ALIGNMENT knobs (X, Y) on the operation panel to move the displayed beam to the center of the concentric circle. Next, select [Aperture] and turn the STIGMA/ALIGNMENT knobs (X, Y) one by one to stop or minimize the movement of the image. Close the aperture dialog and focus with autofocus. Repeat this operation twice more to adjust the focus.

After that, the particle size of 300 magnetic toner particles is measured to obtain the number average particle size. The number average particle diameter is obtained by measuring the maximum diameter of the observed magnetic toner particles and calculating the arithmetic mean of the maximum diameter.

(4) Focus adjustment For the particles with a number average particle diameter of ±0.1 μm obtained in (3), drag inside the magnification display part of the control panel with the middle point of the maximum diameter aligned with the center of the measurement screen, Set the magnification to 10000 (10k) times. Rotate the focus knob [COARSE] on the operation panel, and adjust the aperture alignment when the focus is achieved to some extent. Click [Align] in the control panel to display the alignment dialog and select [Beam]. Rotate the STIGMA/ALIGNMENT knobs (X, Y) on the operation panel to move the displayed beam to the center of the concentric circle. Next, select [Aperture] and turn the STIGMA/ALIGNMENT knobs (X, Y) one by one to stop or minimize the movement of the image. Close the aperture dialog and focus with autofocus. After that, the magnification is set to 50,000 (50k) times, the focus is adjusted using the focus knob and the STIGMA/ALIGNMENT knob in the same manner as above, and the focus is adjusted by autofocus again. Repeat this operation again to adjust the focus. Here, if the tilt angle of the observation surface is large, the measurement accuracy of the coverage tends to be low, so when adjusting the focus, select a surface that has the entire observation surface in focus at the same time. and analyze.

(5) Save image Adjust the brightness in ABC mode, take a picture with a size of 1280 x 960 pixels, and save it. 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 magnetic toner particles.

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

Image analysis software Image-Pro Plus ver. 5.0 analysis conditions are as follows.
Software Image-ProPlus5.1J

Select "Measurement" from the toolbar, then "Count/Size" and then "Options" to set the binarization conditions. Select the 8-connected object extraction option and set the smoothing to 0. In addition, preselect, fill holes, do not select comprehensive lines, and set "exclude border" to "none". Select “Measurement item” from “Select” on the toolbar, and enter 2 to ¹⁰⁷ in the area sorting range.

The calculation of coverage is performed by enclosing a square area. At this time, the area (C) of the region is set to 24000 to 26000 pixels. "Processing" - Make a note of the numerical values from 0 to 255 when automatic binarization is performed. Next, input the area value noted above with "Select Range" on the toolbar, and binarize with "Count".

Then, the total sum (D) of the area of the regions without silica is calculated. Further, from the area C of the square regions and the total sum D of the areas of the silica-free regions, the coverage a is obtained by the following formula.
Coverage a (%) = 100-(D/C x 100)

As described above, the coverage a is calculated for 30 or more magnetic toner particles in each of 10 or more selected ranges. .

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

<Calculation of Coverage B>
The coverage B is calculated by first removing unfixed inorganic fine particles on the surface of the magnetic toner, and then performing the same operation as in the calculation of the coverage A. FIG.

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

As an example, NOB-130 (manufactured by Hosokawa Micron Co., Ltd.) was used for magnetic toner with a coverage A of 46% with three types of external addition strength, and the ultrasonic dispersion time and the coverage calculated after ultrasonic dispersion. is shown in FIG. FIG. 6 was prepared by calculating the coverage ratio of the magnetic toner dried after removing the inorganic fine particles by ultrasonic dispersion by the following method in the same manner as the coverage ratio A described above.

From FIG. 6, it can be seen that the coverage decreases as the inorganic fine particles are removed by ultrasonic dispersion, and that the coverage becomes almost constant after 20 minutes of ultrasonic dispersion regardless of the strength of external addition. From this, it was assumed that particles other than the inorganic fine particles embedded 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 Contaminon N (Neutral detergent manufactured by Wako Pure Chemical Industries, Product No. 037-10361) are put into a 30 mL glass vial and thoroughly mixed. 1.50 g of the magnetic toner is put into the prepared solution, and the magnet is brought close to the bottom to completely sink the magnetic toner. After that, the magnet is moved to remove air bubbles and the magnetic toner is made to fit into the solution.

Set so that the tip of the ultrasonic vibrator UH-50 (manufactured by SMT Co., Ltd., using a titanium alloy tip with a diameter of 6 mm at the tip) is at the center of the vial and at a height of 5 mm from the bottom of the vial, Inorganic fine particles are removed by ultrasonic dispersion. After applying ultrasonic waves for 30 minutes, all 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 for 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 imaging conditions for the S-4800 are as follows.

The operations (1) to (3) were performed in the same manner as in the above-described "calculation of coverage A", and the surface of the magnetic toner was focused at a magnification of 50000 (50k) in the same manner as in (4). After that, the brightness is adjusted in the ABC mode. After that, after increasing the magnification to 100,000 (100k) times, the focus is adjusted using the focus knob and the STIGMA/ALIGNMENT knob in the same manner as in (4), and the focus is adjusted by autofocus. The focus adjustment operation is repeated again, and the focus is adjusted at a magnification of 100000 (100k).

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

EXAMPLES The present invention will be described in more detail below with reference to Examples and Comparative Examples, but the present invention is not limited to these. All parts and percentages in Examples and Comparative Examples are based on mass unless otherwise specified. Moreover, Example 16 is a reference example.

<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 introduced into a reaction vessel equipped with a thermometer while replacing with nitrogen. After heating to 70° C., polymerization was performed over 5 hours, and resin 1 was obtained by drying under reduced pressure. The peak molecular weight (Mp) of 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 it in 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 (manufactured by IKA: Ultra Turrax T50). Thereafter, toluene was separated by distillation to obtain a resin particle dispersion liquid 1. The solid content concentration in 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 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 resin particle dispersions 2 to 7.

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

<Preparation Example of Wax Dispersion Liquid 2>
Wax Dispersion Liquid 2 was obtained in the same manner as in Preparation Example of Wax Dispersion Liquid 1, except that paraffin wax was replaced with behenyl behenate (melting point: 73° C.). 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 Wax Dispersion 1, the amount of surfactant added and the conditions of the homogenizer were adjusted to obtain Wax Dispersions 3 to 5 having physical properties shown in Table 2.

<Manufacturing Example of Magnetic Body 1>
50 liters of an aqueous solution of ferrous sulfate containing 2.0 mol/L of Fe ²⁺ was mixed with 55 liters of an aqueous solution of 4.0 mol/L sodium hydroxide, and a ferrous salt aqueous solution containing ferrous hydroxide colloid was obtained. Obtained. This aqueous solution was kept at 85° C. and an oxidation reaction was carried out while blowing air at 20 L/min to obtain a slurry containing core particles.

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

The resulting slurry liquid was filtered with a filter press, washed, and reslurried with deionized water. To this reslurry liquid (solid content: 50 parts/L), 500 parts (10% by mass relative to the magnetic iron oxide) of ion exchange resin SK110 (manufactured by Mitsubishi Chemical) was added and 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 pulverized to obtain a magnetic substance 1 having primary particles with a number average particle diameter of 0.21 μm.

<Manufacturing Example of Magnetic Body 2>
Magnetic substance 2 having primary particles with a number average particle size of 0.30 μm was obtained in the same manner as in Magnetic substance 1, except that the amount of air blown in and the oxidation reaction time were adjusted. rice field.

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

<Preparation Example of Magnetic Dispersion Liquid 2>
Magnetic Dispersion 2 was prepared in the same manner as in Preparation Example of Magnetic Dispersion 1, except that Magnetic Substance 1 was changed to 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 Particles 1>
・Resin particle dispersion 1 (solid content: 25.0% by mass) 150.0 parts ・Wax dispersion 1 (solid content: 25.0% by mass) 15.0 parts ・Magnetic material dispersion 1 (solid content: 25.0% by mass) %) 105.0 parts The above materials were put into a beaker, and after adjusting the total number of parts of water to 250 parts, the temperature was adjusted to 30.0°C. After that, using a homogenizer (manufactured by IKA, Ultra Turrax T50), they were mixed by stirring at 5000 rpm for 1 minute.
Further, 10.0 parts of a 2.0% by mass aqueous solution of magnesium sulfate was gradually added as a flocculating agent.

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

Subsequently, after adjusting the aggregated particle dispersion liquid 1 to pH 8.0 using a 0.1 mol/L sodium hydroxide aqueous solution, the aggregated particle dispersion liquid 1 was heated to 80.0° C. and allowed to stand for 180 minutes. Coalescence of agglomerated particles was carried out.

After 180 minutes, a toner particle dispersion liquid 1 in which toner particles are dispersed is obtained. After cooling at a cooling rate of 1.0° C./min, the toner particle dispersion liquid 1 was filtered and washed with ion-exchanged water. Toner particles were removed. Next, the cake-like toner particles are put into ion-exchanged water of 20 times the mass of the toner particles, stirred with a three-one motor, and when the toner particles are sufficiently loosened, they are filtered again, washed with water, and solidified. Liquid separation occurred. The resulting caked toner particles were pulverized with a sample mill and dried in an oven at 40° C. for 24 hours. Further, the obtained powder was pulverized with a sample mill and then additionally vacuum-dried in an oven at 40° C. for 5 hours to obtain magnetic toner particles 1 .

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

In this example, an apparatus (NOB-130; manufactured by Hosokawa Micron Corporation) having a volume of 2.0×10 ⁻³ m ³ in the processing space 9 of the apparatus shown in FIG. The power was set at 5.5 kW, and the shape of the stirring member 3 was set as shown in FIG. 3(b). The overlap width d of the stirring member 3a and the stirring member 3b in FIG. 0 mm.

100 parts of magnetic toner particles 1 and 1.0 parts of fine silica particles 1 were put into the apparatus. Silica fine particles 1 are 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 dimethylsilicone oil. is.

After the magnetic toner particles and silica fine particles 1 were added, pre-mixing was carried out in order to uniformly mix the magnetic toner particles and silica fine particles 1 .

The conditions for pre-mixing were that the power of the drive unit 8 was 0.1 W/g (the number of revolutions of the drive unit 8 was 150 rpm), and the processing time was 1 minute.

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

After the external addition and mixing treatment, coarse particles and the like were removed by a circular vibrating sieve equipped with a screen having a diameter of 500 mm and an opening of 75 μm, and magnetic toner 1 was obtained. Magnetic toner 1 was magnified and observed with a scanning electron microscope, and the number average particle diameter of the primary particles of the 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 magnetic toner 1 obtained. Table 5 shows the following results of Magnetic Toner 1 obtained.

Volume-average particle size (Dv), number-average particle size (Dn), average brightness at Dn [In the table, simply referred to as average brightness. ], CV1, CV2/CV1, the average value of the occupied area ratio of the magnetic material [indicated as A in the table. ], average circularity, number average diameter of wax domains [indicated as B in the table. ], the peak molecular weight of the main peak measured by GPC of the tetrahydrofuran-soluble portion of the magnetic toner [denoted as Mp in the table. ].

<Example 1>
(Image forming device)
A one-component contact development type LaserJet Pro M12 (manufactured by Hewlett-Packard Co.) was modified to 200 mm/sec, which is faster than the original process speed, and used.

100 g of the magnetic toner 1 was filled into the apparatus modified as described above, and the following evaluations were carried out. As the recording material, business 4200 (manufactured by Xerox) having a basis weight of 75 g/m ² was used.

In addition, Table 6 shows the evaluation results. In addition, the evaluation method and evaluation criteria in each evaluation are as follows.

<Evaluation of Image Density>
Using the above-mentioned modified machine, a durability test was conducted in which a horizontal line printing rate of 2% was printed on 3,000 sheets in an intermittent mode under a low-temperature, low-humidity environment (15.0° C./10.0% RH).

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

With magnetic toner 1, good solid black images with high image density were obtained before and after the endurance test. Evaluation criteria for image density are as follows.

(Evaluation Criteria for Solid Image Density at the Initial Stage 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 (denoted as "Density difference" in Table 6), and the smaller the density difference, the better.

(Evaluation criteria)
A: 0.05 or less B: greater than 0.05 and 0.10 or less C: greater than 0.10 and 0.15 or less D: greater than 0.15

<Evaluation of Fog>
Fog was evaluated after the endurance test at the above image density. By evaluating fogging in a low-temperature, low-humidity environment, it is possible to strictly evaluate fogging caused by toner cracking and chipping, which are affected by toner brittleness. After the endurance test, a white image was output and its reflectance was measured using a REFLECTMETER MODEL TC-6DS manufactured by Tokyo Denshoku. On the other hand, the reflectance of the transfer paper (standard paper) before white image formation was similarly measured. A green filter was used as the filter. The fog was calculated using the following formula from the reflectance before and after white image output. Fog (reflectance) (%) = reflectance (%) of standard paper - reflectance (%) of white image sample
With magnetic toner 1, good images with suppressed fogging were obtained before and after the endurance test. The judgment 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 Streaks>
Development streaks were evaluated by filling 100 g of Magnetic Toner 1 in the remodeled machine and conducting a durability test in a high-temperature and high-humidity environment (32.5° C./80% RH) in the same manner as the image density. An endurance test was performed on 3,000 sheets of horizontal lines with a print rate of 2% in an intermittent mode. A solid black image was output on , and confirmed visually.

By performing the evaluation under the high-temperature and high-humidity environment, the fusion of the toner to the regulating member is facilitated, and development streaks can be evaluated strictly.

In the evaluation results of Magnetic Toner 1, development streaks did not occur throughout the durability test. Criteria for judging development streaks are as follows.

A: No problem even after 3,000 sheets B: More than 2,000 sheets and less than 3,000 sheets C: More than 1,000 sheets and less than 2,000 sheets D: Less than 1,000 sheets

<Evaluation of rear end offset>
Using the modified machine, the setting of the fixing device was changed so that the temperature control of the fixing device was lowered by 10°C. In a high-temperature and high-humidity environment (32.5° C./80% RH), the fixing device was removed between evaluations, and the following evaluation was performed in a state in which the fixing device was sufficiently cooled using an electric fan or the like.

By sufficiently cooling the fixing device after evaluation, the temperature of the fixing nip portion, which has risen after image output, is cooled down, making it possible to evaluate the toner fixability strictly and with good reproducibility.

When evaluating the trailing edge offset, A4 size OceRedLabel paper (basis weight: 80 g/m ² ) manufactured by Canon Inc. was left in the high temperature and high humidity environment for 48 hours or more as the recording material.

By using paper that is relatively heavy and has a large surface roughness, and also using paper that has been left in a high-temperature and high-humidity environment (left paper), it is possible to strictly evaluate trailing edge offset.

Using the magnetic toner 1, a solid black image was output on the left 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 Magnetic Toner 1, a good solid black image without trailing edge offset was obtained.

As a criterion for determining the trailing edge offset, the offset level was visually evaluated for the solid black image output in the above procedure. In addition, the judgment criteria are as follows.

A: No offset at all B: Some offset can be seen if you look closely C: Offset is seen but not noticeable D: Offset is noticeable

<Production Example of Magnetic Toner Particles 2>
(Pre-coagulation step)
・Magnetic material dispersion liquid 1 (solid content: 25.0% by mass) 105.0 parts The above materials were placed in a beaker, the temperature was adjusted to 30.0°C, and then a homogenizer (Ultra Turrax T50, manufactured by IKA) was used. The mixture was stirred at 5000 rpm for 1 minute, and 1.0 part of a 2.0% by mass magnesium sulfate aqueous solution was gradually added as a flocculating agent and stirred for 1 minute.

(aggregation process)
・Resin particle dispersion 1 (solid content: 25.0% by mass) 150.0 parts ・Wax dispersion 1 (solid content: 25.0% by mass) 15.0 parts was adjusted to 250 parts, and mixed by stirring at 5000 rpm for 1 minute.

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

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

Subsequently, after adjusting the aggregated particle dispersion liquid 2 to pH 8.0 using a 0.1 mol/L sodium hydroxide aqueous solution, the aggregated particle dispersion liquid 2 was heated to 80.0° C. and allowed to stand for 180 minutes. Coalescence of agglomerated particles was carried out.

After 180 minutes, a toner particle dispersion liquid 2 in which toner particles are dispersed is 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. Toner particles were removed. Next, the cake-like toner particles are put into ion-exchanged water of 20 times the mass of the toner particles, stirred with a three-one motor, and when the toner particles are sufficiently loosened, they are filtered again, washed with water, and solidified. Liquid separation occurred. The resulting caked toner particles were pulverized with a sample mill and dried in an oven at 40° C. for 24 hours. Further, the obtained powder was pulverized with a sample mill and then additionally vacuum-dried 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 manufacturing example of magnetic toner particles 1, except that the conditions were changed to those shown in Table 3.

In the manufacturing example of the magnetic toner particles 3, in the first aggregation step, after adding 0.2 part of a surfactant (Noigen TDS-200, Daiichi Kogyo Seiyaku Co., Ltd.), the aggregating agent was added.

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

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

The obtained melt-kneaded product is cooled, and the cooled melt-kneaded product is coarsely pulverized with a cutter mill. The air temperature was adjusted to 20 kg/hr and the exhaust temperature was adjusted to 38° C., and pulverization was carried out. Further, the magnetic toner particles 18 having a weight-average particle size of 7.58 μm were obtained by classifying using a multi-division classifier utilizing the Coanda effect.

<Production Example of Magnetic Toner Particles 19>
・Resin particle dispersion 2 (solid content: 25.0% by mass) 150.0 parts ・Wax dispersion 1 (solid content: 25.0% by mass) 15.0 parts ・Magnetic substance dispersion 1 (solid content: 25.0% by mass) %) 105.0 parts The above materials were put into a beaker, and after adjusting the total number of parts of water to 250 parts, the temperature was adjusted to 30.0°C. Then, using a homogenizer (manufactured by IKA, Ultra Turrax T50), they were mixed by stirring at 8000 rpm for 10 minutes.

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.

Transfer the raw material dispersion to a polymerization vessel equipped with a stirring device and a thermometer, heat to 50.0° C. with a mantle heater, gradually add 0.1 mol/L hydrochloric acid to adjust the pH to 3.0, and stir. This promoted the growth of aggregated particles.

After 60 minutes have passed, the pH of the aggregated particle dispersion 19 is adjusted to 6.8 using a 0.1 mol/L sodium hydroxide aqueous solution, and then the aggregated particle dispersion 19 is heated to 90.0°C. It was allowed to stand for 180 minutes to coalesce the aggregated particles.

After 180 minutes, a toner particle dispersion liquid 19 in which toner particles are dispersed is obtained. After cooling at a cooling rate of 1.0° C./min, the toner particle dispersion liquid 19 was filtered and washed with ion-exchanged water. Toner particles were removed.

Next, the cake-like toner particles are put into ion-exchanged water of 20 times the mass of the toner particles, stirred with a three-one motor, and when the toner particles are sufficiently loosened, they are filtered again, washed with water, and solidified. Liquid separation occurred. The resulting caked toner particles were pulverized with a sample mill and dried in an oven at 40° C. for 24 hours. Further, the obtained powder was pulverized with a sample mill and then additionally vacuum-dried in an oven at 40° C. for 5 hours to obtain magnetic toner particles 19 .

<Production Example of Magnetic Toner Particles 20>
(Pre-coagulation step)
・Magnetic material dispersion liquid 1 (solid content: 25.0% by mass) 105.0 parts The above materials were placed in a beaker, the temperature was adjusted to 30.0°C, and then a homogenizer (Ultra Turrax T50, manufactured by IKA) was used. The mixture was stirred at 8000 rpm for 10 minutes, and 1.0 part of a 2.0% by mass magnesium sulfate aqueous solution was gradually added as a flocculating agent and stirred for 10 minutes.

(aggregation process)
・Resin particle dispersion 1 (solid content: 25.0% by mass) 150.0 parts ・Wax dispersion 1 (solid content: 25.0% by mass) 15.0 parts was adjusted to 250 parts, and mixed by stirring at 8000 rpm for 1 minute.

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

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 50 minutes had passed, 200.0 parts of a 5.0 mass % aqueous solution of ethylenediaminetetraacetic acid (EDTA) was added to prepare aggregated particle dispersion 20 .

Subsequently, after adjusting the pH of the aggregated particle dispersion 20 to 8.0 using a 0.1 mol/L aqueous sodium hydroxide solution, the aggregated particle dispersion 20 is heated to 80.0° C. and allowed to stand for 180 minutes. Coalescence of agglomerated particles was carried out.

After 180 minutes, a toner particle dispersion liquid 20 in which toner particles are dispersed is obtained. After cooling at a cooling rate of 1.0° C./min, the toner particle dispersion 20 was filtered and washed with ion-exchanged water. Toner particles were removed.

Next, the caked toner particles are put into ion-exchanged water of 20 times the mass of the toner particles, and stirred with a three-one motor. Liquid separation occurred. The resulting caked toner particles were pulverized with a sample mill and dried in an oven at 40° C. for 24 hours. Further, the obtained powder was pulverized with a sample mill and then additionally vacuum-dried in an oven at 40° C. for 5 hours to obtain magnetic toner particles 20 .

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

<Manufacturing Examples of Magnetic Toners 2 to 31>
In the production example of magnetic toner 1, magnetic toner particles No. , external additive formulation, external additive device, external additive conditions, and treatment time were changed as shown in Table 4 to obtain magnetic toners 2 to 31 in the same manner. Table 4 shows the physical properties of the magnetic toners 2 to 31 obtained.

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

Volume-average particle size (Dv), number-average particle size (Dn), average brightness at Dn [In the table, simply referred to as average brightness. ], CV1, CV2/CV1, the average value of the occupied area ratio of the magnetic material [indicated as A in the table. ], average circularity, number average diameter of wax domains [indicated as B in the table. ], the peak molecular weight of the main peak measured by GPC of the tetrahydrofuran-soluble portion of the magnetic toner [indicated as Mp in the table. ]. Further, Table 6 shows the evaluation results of magnetic toners 2 to 31.

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

Magnetic Toners 10 and 11 and Magnetic Toners 13 to 31 were not subjected to pre-mixing, but were subjected to external additive mixing immediately after the magnetic toner particles and inorganic fine particles were added.

In Table 4,
"A" in the external addition 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 magnetic toners 2 to 31. Table 6 shows the results.

REFERENCE SIGNS LIST 1 body casing 2 rotating body 3, 3a, 3b stirring member 4 jacket 5 raw material inlet 6 product outlet 7 central shaft 8 driving unit 9 processing space 10 rotating body end side surface 11 rotation direction 12 return direction 13 feed direction 16 raw material introduction Inner piece for outlet 17 Inner piece for product outlet d Space indicating overlapped 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 Fixed member 57 Toner 58 Stirring member R1, R2 and R3 Direction of rotation

Claims (8)

magnetic toner particles containing a binder resin, a magnetic substance and wax;
Inorganic fine particles present on the surface of the magnetic toner particles ;
A magnetic toner containing
The magnetic toner is an emulsion aggregation magnetic toner having an average circularity of 0.960 or more,
In a 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,
When the surface coverage of the magnetic toner particles with the inorganic fine particles is defined as a coverage A (%), the coverage A is 45.0% or more and 80.0% or less,
the wax forms domains inside the magnetic toner particles, and the number average diameter of the domains is 100 nm or more and 500 nm or less;
The binder resin contains a styrene-based resin,
The main peak has a peak molecular weight of 5000 or more and 12000 or less as measured by gel permeation chromatography of the tetrahydrofuran-soluble portion of the magnetic toner.
A magnetic toner characterized by: Let Dn (μm) be the number average particle diameter of the magnetic toner,
CV1 (%) is the coefficient of variation of the brightness dispersion value of the magnetic toner in the range of Dn−0.500 or more and Dn+0.500 or less,
When CV2 (%) is the coefficient of variation of the luminance dispersion value of the magnetic toner in the range of Dn-1.500 or more and Dn-0.500 or less,
The CV1 and the CV2 satisfy the relationship of the following formula (1),
The magnetic toner has an average luminance of 30.0 or more and 60.0 or less at the Dn.
The magnetic toner according to claim 1.
CV2/CV1≤1.00 (1) In a cross section of the magnetic toner using a transmission electron microscope,
The average value of the occupied area ratio of the magnetic material is 10.0% or more and 40.0% or less when the cross section of the magnetic toner is divided by a square grid with one side of 0.8 μm.
The magnetic toner according to claim 1 or 2. 3. The magnetic toner according to claim 2 , wherein the CV1 is 4.00% or less. 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 any one of claims 1 to 4. The magnetic toner according to any one of claims 1 to 5, wherein the coefficient of variation of the coverage A is 10.0% or less. The magnetic toner according to any one of claims 1 to 6 , wherein the wax contains a hydrocarbon wax. a charging step of externally applying a voltage to the charging member 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 magnetic 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 bearing member to a transfer material with or without an intermediate transfer member;
a fixing step of fixing the toner image transferred to the transfer material by a heating and pressurizing means ;
An image forming method comprising
The developing step is a developing step by a one-component contact development system in which the electrostatic latent image carrier and the magnetic toner carried on the toner carrier are brought into direct contact with each other, and
The magnetic toner is
magnetic toner particles containing a binder resin, a magnetic substance and wax;
Inorganic fine particles present on the surface of the magnetic toner particles ;
and an emulsion aggregation magnetic toner having an average circularity of 0.960 or more ,
In a 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,
When the surface coverage of the magnetic toner particles with the inorganic fine particles is defined as a coverage A (%), the coverage A is 45.0% or more and 80.0% or less,
the wax forms domains inside the magnetic toner particles, and the number average diameter of the domains is 100 nm or more and 500 nm or less;
The binder resin contains a styrene-based resin,
The main peak has a peak molecular weight of 5000 or more and 12000 or less as measured by gel permeation chromatography of the tetrahydrofuran-soluble portion of the magnetic toner.
An image forming method characterized by:

Images