JP2023026551A - Toner for electrostatic charge image development, electrostatic charge image developer, toner cartridge, process cartridge, image forming apparatus, and image forming method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a toner for electrostatic charge image development that can prevent fogging occurring on an image immediately after the start-up of an image forming apparatus.

SOLUTION: A toner for electrostatic charge image development includes a toner particle and strontium titanate particles externally added to the toner particle. The strontium titanate particles present in the surface of the toner particle have an average primary particle diameter of 30 nm or more and 100 nm or less, an average circularity of primary particles of 0.82 or more and 0.94 or less, and a cumulative 84% circularity of the primary particles of more than 0.92. The strontium titanate particle is a strontium titanate particle that is doped with a metal element other than titanium and strontium and has a surface on which hydrophobing treatment is executed with a silicon-containing organic compound. The water content of the strontium titanate particle is 2% or more and 5% or less.

SELECTED DRAWING: None

COPYRIGHT: (C)2023,JPO&INPIT

Description

The present invention relates to an electrostatic image developing toner, an electrostatic image developer, a toner cartridge, a process cartridge, an image forming apparatus, and an image forming method.

Patent Document 1 describes toner and abrasive particles having an average primary particle size of 30 nm or more and 300 nm or less, having a cubic particle shape and/or a rectangular parallelepiped particle shape, and having perovskite crystals. and strontium titanate particles.

In Patent Document 2, strontium titanate having a BET specific surface area of 20 to 50 m ² /g and containing rectangular parallelepiped particles as a particle shape and hydrophobic silica are mixed and added as external additives to toner particles. An electrophotographic toner is disclosed.

Patent Document 3 discloses a toner for electrostatic charge image development in which charge control particles made of strontium titanate surface-treated with silicone oil are adhered and/or embedded in the surface of colored particles.

Patent Document 4 discloses a two-component developer containing 0.1 to 1.0 parts by weight of strontium titanate having a weight average particle diameter of 30 to 75 nm with respect to 100 parts by weight of toner base particles. ing.

Japanese Unexamined Patent Application Publication No. 2011-203758 Japanese Patent No. 5248511 Japanese Unexamined Patent Application Publication No. 2011-137980 JP 2010-44113 A

In the present invention, the strontium titanate particles present on the surface of the toner particles have an average primary particle diameter of 30 nm or more and 100 nm or less and an average circularity of the primary particles of 0.82 or more and 0.94 or less. When the circularity at which the cumulative 84% of the particles is 0.92 or less, or when the average circularity of the primary particles is 0.82 or more and 0.94 or less, and the circularity at which the cumulative 84% of the primary particles is 0 An object of the present invention is to provide a toner for developing an electrostatic charge image, which has an average primary particle diameter of more than 0.92 and is capable of suppressing fogging occurring in an image immediately after the start-up of an image forming apparatus as compared with the case where the average primary particle diameter is less than 30 nm. and

The above problems are solved by the following means.
The invention according to <1> is
comprising toner particles and strontium titanate particles externally added to the toner particles;
The strontium titanate particles present on the surface of the toner particles have an average primary particle size of 30 nm or more and 100 nm or less, an average circularity of the primary particles of 0.82 or more and 0.94 or less, and a cumulative total of primary particles of 84 % circularity of more than 0.92.

The invention according to <2> is
The electrostatic image developing toner according to <1>, wherein the strontium titanate particles present on the surface of the toner particles have a standard deviation of circularity of primary particles of 0.04 or more and 2.0 or less.
The invention according to <3> is
The electrostatic image developing toner according to <2>, wherein the strontium titanate particles present on the surface of the toner particles have a standard deviation of circularity of primary particles of 0.04 or more and 1.0 or less.

The invention according to <4> is
The toner for electrostatic charge image development according to any one of <1> to <3>, wherein the water content of the strontium titanate particles is 1.5% or more and 10% or less.
The invention according to <5 is
The toner for electrostatic charge image development according to <4>, wherein the water content of the strontium titanate particles is 2% or more and 5% or less.

The invention according to <6> is
The electrostatic charge image developing toner according to any one of <1> to <5>, wherein the strontium titanate particles have a hydrophobic surface.
The invention according to <7> is
The electrostatic charge image developing toner according to <6>, wherein the strontium titanate particles have surfaces that have been subjected to hydrophobic treatment with a silicon-containing organic compound.
The invention according to <8> is
The electrostatic charge image developing toner according to <7>, wherein the strontium titanate particles have the surface containing the silicon-containing organic compound in an amount of 5% by mass or more and 30% by mass or less based on the mass of the strontium titanate particles.
The invention according to <9> is
The electrostatic charge image developing toner according to <8>, wherein the strontium titanate particles have the surface containing the silicon-containing organic compound in an amount of 10% by mass or more and 25% by mass or less based on the mass of the strontium titanate particles.
The invention according to <10> is
The toner for electrostatic charge image development according to any one of <7> to <9>, wherein the silicon-containing organic compound is at least one selected from the group consisting of alkoxysilane compounds and silicone oils.
The invention according to <11> is
The mass ratio (Si/Sr) of silicon (Si) and strontium (Sr) calculated from the qualitative and quantitative analysis of fluorescent X-ray analysis of the strontium titanate particles is 0.025 or more and 0.25 or less, <7> to <10>, the electrostatic charge image developing toner.

The invention according to <12> is
The toner for electrostatic charge image development according to any one of <1> to <11>, wherein the surface coverage of the strontium titanate particles with respect to the toner particles is 3% or more and 50% or less.
The invention according to <13> is
The toner for developing an electrostatic charge image according to <12>, wherein the surface coverage of the strontium titanate particles with respect to the toner particles is 3% or more and 30% or less.

The invention according to <14> is
The toner for electrostatic charge image development according to any one of <1> to <13>, wherein the strontium titanate particles are strontium titanate particles doped with a metal element other than titanium and strontium.
The invention according to <15> is
The electrostatic charge image developing toner according to <14>, wherein the strontium titanate particles are lanthanum-doped strontium titanate particles.

The invention according to <16> is
The toner for electrostatic charge image development according to any one of <1> to <15>, wherein the strontium titanate particles present on the surface of the toner particles have an average primary particle size of 30 nm or more and 80 nm or less.
The invention according to <17> is
The toner for electrostatic charge image development according to <16>, wherein the strontium titanate particles present on the surface of the toner particles have an average primary particle diameter of 30 nm or more and 60 nm or less.

The invention according to <18> is
The electrostatic image developing toner according to any one of <1> to <17>, wherein the toner particles have an average circularity of 0.91 or more and 0.98 or less.
The invention according to <19> is
The toner for developing an electrostatic charge image according to <18>, wherein the average circularity of the toner particles is 0.93 or more and 0.97 or less.

The invention according to <20> is
The toner for developing an electrostatic charge image according to any one of <1> to <19>, wherein the toner particles are white toner particles.

The invention according to <21> is
An electrostatic charge image developer containing the electrostatic charge image developing toner according to any one of <1> to <20>.

The invention according to <22> is
containing the electrostatic charge image developing toner according to any one of <1> to <20>,
A toner cartridge that is attached to and detached from an image forming apparatus.

The invention according to <23> is
Developing means for accommodating the electrostatic charge image developer according to <21> and developing the electrostatic charge image formed on the surface of the image carrier by the electrostatic charge image developer as a toner image,
A process cartridge that is attached to and detached from an image forming apparatus.

The invention according to <24> is
an image carrier;
charging means for charging the surface of the image carrier;
electrostatic charge image forming means for forming an electrostatic charge image on the surface of the charged image carrier;
Developing means for accommodating the electrostatic charge image developer according to <21> and developing the electrostatic charge image formed on the surface of the image carrier with the electrostatic charge image developer as a toner image;
a transfer means for transferring the toner image formed on the surface of the image carrier onto the surface of a recording medium;
fixing means for fixing the toner image transferred onto the surface of the recording medium;
An image forming apparatus comprising:

The invention according to <25> is
a charging step of charging the surface of the image carrier;
an electrostatic charge image forming step of forming an electrostatic charge image on the surface of the charged image carrier;
a developing step of developing the electrostatic charge image formed on the surface of the image carrier as a toner image with the electrostatic charge image developer according to <21>;
a transfer step of transferring the toner image formed on the surface of the image carrier onto the surface of a recording medium;
a fixing step of fixing the toner image transferred onto the surface of the recording medium;
An image forming method comprising:

According to the inventions <1>, <16>, <17>, <18>, <19>, or <20>, the strontium titanate particles present on the surface of the toner particles have an average primary particle diameter of 30 nm. 100 nm or less, and the average circularity of the primary particles is 0.82 or more and 0.94 or less, but the circularity at which the primary particles are cumulative 84% is 0.92 or less, or The average circularity is 0.82 or more and 0.94 or less, and the circularity at which the cumulative 84% of the primary particles is more than 0.92, but the average primary particle size is less than 30 nm. Provided is a toner for developing an electrostatic charge image that can suppress fogging that occurs on an image immediately after the start-up of the apparatus.

According to the invention according to <2> or <3>, compared to the case where the standard deviation of the strontium titanate particles is less than 0.04, the static electricity that can suppress the fogging occurring in the image immediately after the start-up of the image forming apparatus. A toner for developing a charge image is provided.

According to the invention according to <4> or <5>, compared to the case where the water content of the strontium titanate particles is less than 1.5% by mass or more than 10% by mass, Provided is an electrostatic charge image developing toner capable of suppressing fogging.

According to the invention pertaining to <6> or <10>, it is possible to suppress fogging occurring in an image immediately after startup of the image forming apparatus, compared to the case where the strontium titanate particles do not have a hydrophobized surface. A toner for developing electrostatic charge images is provided.

According to the invention according to <7>, <8>, or <9>, compared to the case of having a surface containing a silicon-containing organic compound of less than 5% by mass or more than 30% by mass with respect to the mass of the strontium titanate particles, Accordingly, a toner for developing an electrostatic charge image is provided that can suppress fogging that occurs on an image immediately after startup of an image forming apparatus.

According to the invention according to <11>, the mass ratio (Si/Sr) of silicon (Si) and strontium (Sr) calculated from the qualitative and quantitative analysis of fluorescent X-ray analysis of the strontium titanate particles is 0.0. Provided is an electrostatic charge image developing toner capable of suppressing fogging occurring in an image immediately after the start-up of an image forming apparatus as compared with the case where it is less than 025 or more than 0.25.

According to the invention pertaining to <12> or <13>, as compared with the case where the surface coverage of the strontium titanate particles with respect to the toner particles is less than 3% or more than 50%, the occurrence of Provided is an electrostatic charge image developing toner capable of suppressing fogging.

According to the invention according to <14> or <15>, fogging occurs in an image immediately after startup of the image forming apparatus, compared to the case where the strontium titanate particles are not doped with a metal element other than titanium and strontium. Provided is an electrostatic charge image developing toner capable of suppressing the

According to the inventions <21>, <22>, <23>, <24>, or <25>, the strontium titanate particles present on the surface of the toner particles have an average primary particle diameter of 30 nm or more and 100 nm or less. Although the average circularity of the primary particles is 0.82 or more and 0.94 or less, the circularity at which the cumulative 84% of the primary particles is 0.92 or less, or the average circularity of the primary particles is 0 .82 or more and 0.94 or less, and the circularity at which the primary particles accumulate 84% is 0.92
An electrostatic charge image developer capable of suppressing fogging occurring in an image immediately after startup of an image forming apparatus, compared to the case of using an electrostatic charge image developing toner having an average primary particle diameter of less than 30 nm, even though it is super. A toner cartridge, process cartridge, image forming apparatus, or image forming method is provided.

FIG. 4 is an SEM image of a toner externally added with SW-360 manufactured by Titan Kogyo Co., Ltd., which is an example of strontium titanate particles, and a circularity distribution graph of the strontium titanate particles obtained by analyzing the SEM image. FIG. FIG. 4 is an SEM image of a toner to which another strontium titanate particle is externally added, and a circularity distribution graph of the strontium titanate particles obtained by analyzing the SEM image; FIG. 1 is a schematic configuration diagram showing an image forming apparatus according to an embodiment; FIG. 1 is a schematic configuration diagram showing a process cartridge according to an embodiment; FIG.

Embodiments of the invention are described below. These descriptions and examples are illustrative of embodiments and do not limit the scope of the invention.

When referring to the amount of each component in the composition in the present disclosure, when there are multiple types of substances corresponding to each component in the composition, unless otherwise specified, the multiple types of substances present in the composition It means the total amount of substance.

In the present disclosure, a numerical range indicated using "to" indicates a range including the numerical values before and after "to" as the minimum and maximum values, respectively.

In the present disclosure, "toner for developing an electrostatic charge image" may be simply referred to as "toner", and "electrostatic charge image developer" may simply be referred to as "developer".

<Toner for electrostatic charge image development>
The toner according to the exemplary embodiment includes toner particles and strontium titanate particles externally added to the toner particles. That is, the toner according to the exemplary embodiment includes toner particles and strontium titanate particles as an external additive.
In the toner according to the exemplary embodiment, the strontium titanate particles present on the surface of the toner particles have an average primary particle size of 30 nm or more and 100 nm or less, and an average circularity of the primary particles of 0.82 or more and 0.94 or less. and the circularity at which the primary particles accumulate 84% is greater than 0.92.
Hereinafter, the average primary particle diameter is 30 nm or more and 100 nm or less, the average circularity of the primary particles is 0.82 or more and 0.94 or less, and the circularity at which the cumulative 84% of the primary particles is greater than 0.92. The strontium titanate particles present on the surface of the toner particles are referred to as "specific strontium titanate particles".

Due to its elemental composition, strontium titanate particles have a charging behavior close to that of titanium oxide. In particular, since the strontium element has an antistatic effect under low humidity conditions, the strontium titanate particles containing the strontium element can be said to be a material with less difference depending on the humidity environment than titanium oxide.
On the other hand, strontium titanate particles have a perovskite crystal structure and are cubic or rectangular parallelepiped, and thus are poorly dispersed in toner particles when externally added to the toner particles. Further, since the cubic or rectangular parallelepiped strontium titanate particles are present on the surface of the toner particles in a state where the corners are pierced, if charges are concentrated on the exposed corners of the strontium titanate particles during triboelectrification, It is presumed that the charging rise of the toner deteriorates. In particular, when a low-density image is output at a low temperature and low humidity (for example, 10° C. and 15% RH), the charge rise of the toner tends to be poor. As a result, fog occurred in the image immediately after the image forming apparatus was started up.
On the other hand, even if the cubic or rectangular parallelepiped shape is broken, if the particle diameter is small, it is likely to be buried in the toner particles, resulting in fogging.

As a result of intensive studies by the present inventors, the average primary particle diameter, the average circularity of the primary particles, and the circularity at which the cumulative 84% of the primary particles is the cumulative 84% of the strontium titanate particles present on the surface of the toner particles. Focusing on the shape characteristics, the inventors have found that the occurrence of fog can be suppressed by controlling these characteristics.
The above three shape characteristics indicate that the strontium titanate particles are present on the surface of the toner particles in a state of excellent dispersibility and in a state of few corners. because it can
As described above, in the toner according to the present embodiment, the strontium titanate particles are present on the surface of the toner particles in a state in which the corners are less exposed and are excellent in dispersibility. It is considered possible to suppress the fog that occurs in the image immediately after startup.

[Specific strontium titanate particles]
- Average primary particle size The average primary particle size of the specific strontium titanate particles is 30 nm or more and 100 nm or less, preferably 30 nm or more and 80 nm or less, and preferably 30 nm or more and 60 nm or less.
When the average primary particle diameter of the specific strontium titanate particles is 30 nm or more, the specific strontium titanate particles are suppressed from being embedded in the toner particles, and fogging that occurs in images immediately after starting up the image forming apparatus can be easily suppressed. . Further, when the average primary particle size of the specific strontium titanate particles is 100 nm or less, the surface coverage of the toner particles can be easily increased, and the fog that occurs in the image immediately after starting up the image forming apparatus can be easily suppressed.

When the average primary particle diameter of the specific strontium titanate particles is within the above range, it can be said that the strontium titanate particles used as an external additive also have a small diameter. Therefore, it can be said that the fact that the average primary particle diameter is within the above range means that the small-diameter strontium titanate particles are present on the surface of the toner particles in a state of excellent dispersibility.

The primary particle size of the specific strontium titanate particles is the diameter of a circle having the same area as the primary particle image (so-called circle equivalent diameter), and the average primary particle size of the specific strontium titanate particles is the number of primary particle sizes. It is the particle size that is cumulatively 50% from the small diameter side in the standard distribution.
The primary particle size of the specific strontium titanate particles is obtained by taking an SEM image of the toner to which the strontium titanate particles are externally added and analyzing at least 300 strontium titanate particles on the toner particles in the SEM image. A specific measuring method will be described in [Examples] below.
It can also be confirmed from this SEM image that the specific strontium titanate particles are present on the surface of the toner particles in a state of excellent dispersibility.

The average primary particle size of the specific strontium titanate particles can be controlled by adjusting the average primary particle size of the strontium titanate particles used as the external additive.
Also, the average primary particle size of the strontium titanate particles used as an external additive can be controlled, for example, by various conditions when the strontium titanate particles are produced by a wet process.

The specific strontium titanate particles have an average circularity of the primary particles of 0.82 or more and 0.94 or less, and the circularity of the primary particles that is cumulative 84% is more than 0.92.
Hereinafter, the average circularity of the primary particles of the strontium titanate particles is referred to as "average circularity".
, the circularity at which the primary particles are cumulatively 84% is sometimes referred to as "cumulative 84% circularity".
When the average circularity and the cumulative 84% circularity are within the above ranges, it can be said that the strontium titanate particles are present on the surface of the toner particles with few corners (the reason for this will be described later). Therefore, it is considered that fogging in the image immediately after starting up the image forming apparatus, which is caused by concentration of electric charges on the corners of the strontium titanate particles, is suppressed.

Moreover, since the average circularity and cumulative 84% circularity of the specific strontium titanate particles are within the above ranges, it can be said that the strontium titanate particles used as an external additive also have rounded corners. Therefore, the strontium titanate particles with rounded corners are present on the surface of the toner particles in a state of being excellent in dispersibility, compared to the case of using cubic or rectangular parallelepiped strontium titanate particles as an external additive. It can be said that there is

In the present embodiment, the circularity of the primary particles of the strontium titanate particles is 4π×(area of the primary particle image)÷(peripheral length of the primary particle image) ² , and the average circularity of the primary particles is circular. The cumulative circularity of primary particles is 50% from the small side in the distribution of degrees of circularity, and the cumulative circularity of primary particles is 84% from the small side in the distribution of circularity.
The circularity of the specific strontium titanate particles is obtained by taking an SEM image of the toner to which the strontium titanate particles are externally added and analyzing at least 300 strontium titanate particles on the toner particles in the SEM image. A specific measuring method will be described in [Examples] below.

The cumulative 84% circularity of the specific strontium titanate particles is one of the indicators of the rounded shape. This cumulative 84% circularity will be explained.

FIG. 1A is an SEM image of a toner externally added with SW-360 manufactured by Titan Kogyo Co., Ltd., which is an example of strontium titanate particles, and a graph of the circularity distribution of the strontium titanate particles obtained by analyzing the SEM image. . As shown by the SEM image, SW-360 had a predominant particle shape of cubic, mixed with rectangular particles and relatively small spherical particles. The circularity distribution of SW-360 of this example was centered between 0.84 and 0.92, with an average circularity of 0.888 and a cumulative 84% circularity of 0.916. This indicates that the main particle shape of SW-360 is a cube, and that the projected image of the cube has regular hexagons (circularity of about 0.907), flat hexagons, and squares (circularity of about 0.907) in order from the closest to a circle. 785), and that the cubic strontium titanate particles adhere to the toner particles at an angle, and the projected image is mainly hexagonal.
Judging from the fact that the actual circularity distribution of SW-360 is as described above and the theoretical circularity of the projected stereoscopic image, the cubic or rectangular parallelepiped strontium titanate particles have a cumulative 84% circularity of the primary particles. It can be estimated to be less than 0.92.
On the other hand, FIG. 1B shows two SEM images (two at different magnifications) of a toner to which another strontium titanate particle is externally added, and the lower SEM image in FIG. ) and a graph of the circularity distribution of the strontium titanate particles obtained by analyzing the SEM image. As shown by the two SEM images (particularly the bottom SEM image of FIG. 1B), the strontium titanate particles of this example had a rounded shape. The strontium titanate particles of this example had an average circularity of 0.883 and a cumulative 84% circularity of 0.935.
From the above, it can be said that the specific strontium titanate particles have a rounded shape when the cumulative 84% circularity is one index of the rounded shape, and a value exceeding 0.92 indicates a rounded shape.

The average circularity of the specific strontium titanate particles is 0.82 or more and 0.94 or less, preferably 0.84 or more and 0.94 or less, from the viewpoint of suppressing fog that occurs in images immediately after the image forming apparatus is started up. More preferably, it is 0.86 or more and 0.92 or less.

The average circularity and cumulative 84% circularity of the specific strontium titanate particles can be controlled by adjusting the average circularity and cumulative 84% circularity of the strontium titanate particles used as the external additive.
In addition, the average circularity and cumulative 84% circularity of the strontium titanate particles used as an external additive are determined by, for example, various conditions when producing the strontium titanate particles by a wet process, and doping metals of metal elements other than titanium and strontium. It can be controlled by the element and its doping amount.

Standard deviation In the present embodiment, the strontium titanate particles present on the surface of the toner particles preferably have a standard deviation of circularity of the primary particles of 0.04 or more and 2.0 or less, more preferably 0.04 or more and 1.0. 0 or less is preferable, and 0.04 or more and 0.50 or less is more preferable.
Cubic or rectangular parallelepiped strontium titanate particles tend to have a narrow circularity distribution due to their shape. Therefore, the strontium titanate particles having the standard deviation of the circularity of the primary particles within the above range serve as an index indicating that they are not strontium titanate particles containing many cubes or rectangular parallelepipeds.
Therefore, the strontium titanate particles having the standard deviation of the circularity of the primary particles within the above range exist on the surface of the toner particles with few corners, and the charge is concentrated on the corners of the strontium titanate particles. It is easy to suppress fogging in an image immediately after startup of the image forming apparatus, which is caused by the image forming apparatus.

Here, the standard deviation of the circularity of the primary particles is the standard deviation of the circularity of at least 300 strontium titanate particles on the toner particles, which is image-analyzed when obtaining the circularity described above.
The measurement of the standard deviation of the circularity of the primary particles can be performed simultaneously with the measurement of the average circularity and cumulative 84% circularity described above.
When calculating the standard deviation of circularity, strontium titanate particles with a primary particle size of 20 nm or less are excluded from the analysis.

-Surface Coverage In the present embodiment, the surface coverage of the strontium titanate particles present on the surface of the toner particles is preferably 3% or more and 50% or less, more preferably 3% or more and 30% or less. preferable.
When the surface coverage of the strontium titanate particles with respect to the toner particles is 5% or more, the action of the strontium titanate particles is effectively exhibited, and the fogging of the image immediately after the start-up of the image forming apparatus is easily suppressed. When the surface coverage of the strontium titanate particles with respect to the toner particles is 50% or less, the charge leakage of the toner becomes noticeable under high temperature and high humidity conditions, and fogging occurs due to the inability to secure a sufficient charge amount of the toner. can be suppressed.

The surface coverage of the strontium titanate particles with respect to the toner particles was determined using the SEM images used to measure the above-mentioned average circularity and cumulative 84% circularity. ) using the area analysis tool.

[Strontium titanate particles]
The strontium titanate particles used as the external additive are described below.
In order to satisfy the average primary particle size of the specific strontium titanate particles described above, the strontium titanate particles used as an external additive preferably have an average primary particle size of 30 nm or more and 100 nm, more preferably 30 nm or more and 80 nm or less. Preferably, 30 nm or more and 60 nm
It is more preferably m or less.
When the average primary particle diameter is 30 nm or more, burial in the toner particles is suppressed, and when it is 100 nm or less, the surface coverage of the toner particles can be easily increased.

In order to satisfy the above-mentioned average circularity and cumulative 84% circularity of the specific strontium titanate particles, it is preferable to use rounded strontium titanate particles as the external additive.
For example, the strontium titanate particles used as the external additive preferably have an average circularity of 0.82 or more and 0.94 or less, more preferably 0.84 or more and 0.94 or less, and 0.86 or more and 0.92. More preferred are:
When the average circularity is 0.82 or more, the dispersibility in the toner particles can be easily improved.

The strontium titanate particles used as the external additive preferably have a peak half width of 0.2° or more and 2.0° or less of the (110) plane obtained by X-ray diffraction.
The peak of the (110) plane obtained by the X-ray diffraction method of strontium titanate particles is a peak appearing near the diffraction angle 2θ=32°. This peak corresponds to the peak of the (110) face of the perovskite crystal.
Strontium titanate particles having a cubic or rectangular parallelepiped particle shape have high crystallinity of perovskite crystals, and the half width of the (110) plane peak is usually less than 0.2°. For example, when SW-350 (strontium titanate particles whose main particle shape is cubic) manufactured by Titan Kogyo Co., Ltd. was analyzed, the half width of the peak of the (110) plane was 0.15°.
On the other hand, round-shaped strontium titanate particles have relatively low perovskite crystallinity, and the half width of the peak of the (110) plane is widened.
The strontium titanate particles used as the external additive preferably have a rounded shape. 0° or less is preferable, 0.2° or more and 1.0° or less is more preferable, and 0.2° or more and 0.5° or less is still more preferable.

The X-ray diffraction of the strontium titanate particles is performed using an X-ray diffractometer (eg RINT Ultima-III, trade name, manufactured by Rigaku Corporation). Measurement settings are source CuKα, voltage 4
0 kV, current 40 mA, sample rotation speed: no rotation, divergence slit: 1.00 mm, divergence longitudinal limiting slit: 10 mm, scattering slit: open, receiving slit: open, scanning mode: FT, counting time: 2.0 seconds, step Width: 0.0050°, Operation axis: 10.0000° to 70.0000°. The half width of a peak in an X-ray diffraction pattern in this disclosure is the full width at half maximum.

Strontium titanate particles used as an external additive are preferably doped with a metal element (hereinafter also referred to as a dopant) other than titanium and strontium. Since the strontium titanate particles contain a dopant, the crystallinity of the perovskite structure is lowered and the particles have a rounded shape.

The dopant for the strontium titanate particles is not particularly limited as long as it is a metallic element other than titanium and strontium. A metal element that, when ionized, has an ionic radius capable of entering the crystal structure constituting the strontium titanate particles is preferred. From this point of view, the dopant for the strontium titanate particles is preferably a metal element having an ionic radius of 40 pm or more and 200 pm or less when ionized, more preferably a metal element having an ion radius of 60 pm or more and 150 pm or less.

Specific examples of dopants for strontium titanate particles include lanthanides, silica, aluminum, magnesium, calcium, barium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, zinc, gallium, niobium, molybdenum, ruthenium, Palladium, indium, antimony, tantalum, tungsten, rhenium, iridium, platinum, bismuth, yttrium, zirconium, niobium, silver and tin. As lanthanoids, lanthanum and cerium are preferred. Among these, lanthanum is preferable from the viewpoint of easy doping and easy control of the shape of the strontium titanate particles.

As the dopant for the strontium titanate particles, a metal element having an electronegativity of 2.0 or less is preferable, and a metal element having an electronegativity of 1.3 or less is more preferable, from the viewpoint of not excessively negatively charging the strontium titanate particles. . The electronegativity in this embodiment is the Allred-Rokow electronegativity.
Preferred metal elements having an electronegativity of 2.0 or less are shown below together with their electronegativities.
Metal elements with an electronegativity of 2.0 or less include lanthanum (1.08), magnesium (1.23), aluminum (1.47), silica (1.74), calcium (1.04), vanadium (1.45), chromium (1.56), manganese (1.60), iron (1.64), cobalt (1.70), nickel (1.75), copper (1.75), zinc ( 1.66), gallium (1.82), yttrium (1.11), zirconium (1.22), niobium (1.23), silver (1.42), indium (1.49), tin (1 .72), barium (0.97), tantalum (1.33), rhenium (1.46), cerium (1.06), and the like.

The amount of the dopant in the strontium titanate particles is in the range of 0.1 mol % or more and 20 mol % or less with respect to strontium, from the viewpoint of obtaining a rounded shape while having a perovskite crystal structure. is preferred, the range of 0.1 mol % to 15 mol % is more preferred, and the range of 0.1 mol % to 10 mol % is even more preferred.

The strontium titanate particles used as an external additive preferably have a water content of 1.5% by mass or more and 10% by mass or less. When the water content is 1.5% by mass or more and 10% by mass or less (more preferably 2% by mass or more and 5% by mass or less), the resistance of the strontium titanate particles is in an appropriate range, and the occurrence of fogging is further suppressed.
The water content of the strontium titanate particles can be achieved within the above range by producing the strontium titanate particles by a wet process and adjusting the drying treatment conditions (temperature and time).
Further, when the surface of the strontium titanate particles is hydrophobized, the above range may be achieved by adjusting the drying conditions after the hydrophobization treatment.

The water content of strontium titanate particles is measured as follows.
After 20 mg of the measurement sample was left to stand for 17 hours in a chamber at a temperature of 22° C./relative humidity of 55% and the humidity was adjusted, a thermobalance (TGA-50 model manufactured by Shimadzu Corporation) was placed in a room at a temperature of 22° C./relative humidity of 55%. is heated from 30° C. to 250° C. at a rate of temperature increase of 30° C./min in a nitrogen gas atmosphere, and the weight loss on heating (mass lost due to heating) is measured.
Then, based on the measured weight loss on heating, the moisture content is calculated by the following formula.
Moisture content (mass%) = (loss on heating from 30°C to 250°C)/(mass before heating after humidity adjustment) x 100

The strontium titanate particles used as an external additive are preferably strontium titanate particles having a hydrophobically treated surface from the viewpoint of improving the action of the strontium titanate particles, and are hydrophobized with a silicon-containing organic compound. Strontium titanate particles having a smoothed surface are more preferred.
Examples of silicon-containing organic compounds include alkoxysilane compounds, silazane compounds, silicone oils, etc. Among them, at least one compound selected from the group consisting of alkoxysilane compounds and silicone oils is preferred.
The silicon-containing organic compound will be described in detail in the section on the method for producing strontium titanate particles.

The strontium titanate particles used as an external additive are 1% by mass or more and 50% by mass or less (preferably 5% by mass or more and 40% by mass or less, more preferably 5% by mass or more and 30% by mass or less) of the mass of the strontium titanate particles. % or less, more preferably 10% or more and 25% or less by weight) of the silicon-containing organic compound.
That is, the amount of hydrophobic treatment by the silicon-containing organic compound is preferably 1% by mass or more and 50% by mass or less, more preferably 5% by mass or more and 40% by mass or less, and more preferably 5% by mass or more and 30% by mass or more, based on the mass of the strontium titanate particles. % by mass or less is more preferable, and 10% by mass or more and 25% by mass or less is particularly preferable.
When the hydrophobization treatment amount is 1% by mass or more, the charge amount of the toner can be secured even under high temperature and high humidity conditions, and the occurrence of fogging can be easily suppressed. Further, when the hydrophobization treatment amount is 50% by mass or less, the saturated charge amount of the toner does not become too large even under low temperature and low humidity conditions, and the occurrence of fogging can be easily suppressed. Further, when the hydrophobization treatment amount is 30% by mass or less, it is easy to suppress the generation of aggregates due to the hydrophobized surface.

From the viewpoint of improving the action of the strontium titanate particles, the hydrophobized surfaces of the strontium titanate particles have silicon (Si) and strontium (Sr) ratios calculated from qualitative and quantitative analysis of fluorescent X-ray analysis. The mass ratio (Si/Sr) is preferably 0.025 or more and 0.25 or less, more preferably 0.05 or more and 0.20 or less.

Here, the fluorescent X-ray analysis of the hydrophobized surface of the strontium titanate particles is performed by the following method.
That is, qualitative and quantitative analysis measurements are performed using an X-ray fluorescence analyzer (Shimadzu Corporation, XRF1500) under conditions of X-ray output of 40 V, 70 mA, measurement area of 10 mmφ, and measurement time of 15 minutes. Here, the elements to be analyzed are oxygen (O), silicon (Si), titanium (Ti), strontium (Sr), and metal elements other than titanium and strontium (Me). , the mass ratio (%) of each element is calculated by referring to separately prepared calibration curve data that can be quantified for each element.
The mass ratio (Si/Sr) is calculated based on the mass ratio of silicon (Si) and the mass ratio of strontium (Sr) obtained by this measurement.

The strontium titanate particles used as an external additive have a volume resistivity R1 (Ω·cm) of 11 or more and 14 in common logarithmic value logR1 from the viewpoint of improving the chargeability of the toner and further suppressing the occurrence of fogging. or less, more preferably 11 or more and 13 or less, and even more preferably 12 or more and 13 or less.

The specific volume resistivity R1 of the strontium titanate particles is measured as follows.
On the lower plate of the measuring jig, which is a pair of 20 cm ² circular plates (made of steel) connected to an electrometer (KEYTHLEY, KEITHLEY610C) and a high-voltage power supply (FLUKE, FLUKE415B), titanic acid was applied. The strontium particles are introduced so as to form a flat layer with a thickness ranging from 1 mm to 2 mm.
Thereafter, the formed strontium titanate particle layer is conditioned at 22° C. and 55% RH for 24 hours.
Next, in an environment of 22° C. and 55% RH, an upper electrode plate was placed on the humidity-controlled strontium titanate particle layer, and 4 k was applied to the upper electrode plate to eliminate voids in the strontium titanate particle layer.
A weight of g is put on it, and the thickness of the strontium titanate particle layer is measured in that state. Next, a voltage of 1000 V is applied to the two electrode plates, the current value is measured, and the specific volume resistivity R1 is calculated from the following formula (1).
Formula (1): Volume specific resistivity R1 (Ω cm) = V × S ÷ (A1 - A0) ÷ d
In formula (1), V is the applied voltage of 1000 (V), S is the electrode plate area of 20 (cm ² ), A1 is the measured current value (A), A0 is the initial current value (A) when the applied voltage is 0 V, d is the thickness (cm) of the strontium titanate particle layer.

The specific volume resistivity R1 of the strontium titanate particles used as the external additive is, for example, the specific volume resistivity R2 of the strontium titanate particles before being hydrophobized (R2 is the water content, the type of dopant, the amount of dopant, etc. can be controlled by the type of hydrophobizing agent, hydrophobizing treatment amount, drying temperature and drying time after hydrophobizing treatment, and the like. The specific volume resistivity R1 is preferably controlled by at least one of the water content of the strontium titanate particles before hydrophobization and the amount of hydrophobization treatment.

The volume resistivity R2 of the strontium titanate particles before hydrophobization treatment is preferably 6 or more and 10 or less, more preferably 7 or more and 9 or less, in terms of common logarithm value logR2. In other words, the inside of the hydrophobic treated surface of the strontium titanate particle has the above resistance, and the strontium titanate particle has a low resistance inside and a high resistance surface due to the hydrophobic treatment. Become. This improves the chargeability of the toner. In the present embodiment, the difference (logR1−logR2) between the common logarithmic value logR1 of the volume specific resistivity R1 and the common logarithmic value logR2 of the volume specific resistivity R2 is from the viewpoint of improving the charging property of the toner and ensuring the image density. Therefore, 2 or more and 7 or less are preferable, and 3 or more and 5 or less are more preferable.

The specific volume resistivity R2 of the strontium titanate particles before the hydrophobic treatment surface is formed can be controlled by, for example, the water content of the strontium titanate particles, the type of dopant, the amount of dopant, and the like.
The specific volume resistivity R2 of the strontium titanate particles before hydrophobization treatment is measured by the same method as the specific volume resistivity R1.

-Method for producing strontium titanate particles-
The strontium titanate particles used as an external additive are produced by producing strontium titanate particles and, if necessary, subjecting the surface to hydrophobic treatment.
The method for producing the strontium titanate particles is not particularly limited, but from the viewpoint of controlling the particle size and shape, a wet production method is preferred.

- Production of Strontium Titanate Particles The wet production method of strontium titanate particles is, for example, a production method in which a mixed solution of a titanium oxide source and a strontium source is reacted while adding an alkaline aqueous solution, followed by an acid treatment. In this production method, the particle size of the strontium titanate particles is controlled by the mixing ratio of the titanium oxide source and the strontium source, the concentration of the titanium oxide source at the initial stage of the reaction, the temperature and addition rate when adding the alkaline aqueous solution, and the like.

The titanium oxide source is preferably a mineral peptization product of a hydrolyzate of a titanium compound. Strontium sources include strontium nitrate and strontium chloride.

The mixing ratio of the titanium oxide source and the strontium source is preferably 0.9 or more and 1.4 or less, more preferably 1.05 or more and 1.20 or less, in SrO/TiO ₂ molar ratio. The titanium oxide source concentration at the initial stage of the reaction is preferably 0.05 mol/L or more and 1.3 mol/L or less as TiO ₂ .
5 mol/L or more and 1.0 mol/L or less is more preferable.

In order to adjust the resistance of the strontium titanate particles, it is preferable to add a dopant source to the mixture of the titanium oxide source and the strontium source. Dopant sources include oxides of metals other than titanium and strontium. A metal oxide as a dopant source is added as a solution dissolved in, for example, nitric acid, hydrochloric acid, sulfuric acid, or the like. The amount of the dopant source added is preferably 0.1 mol or more and 10 mol or less, more preferably 0.5 mol or more and 10 mol or less, of the dopant metal per 100 mol of strontium.

Also, the dopant source may be added at the time of adding the alkaline aqueous solution to the mixed solution of the titanium oxide source and the strontium source. Also in this case, the dopant source metal oxide may be added as a solution dissolved in nitric acid, hydrochloric acid, or sulfuric acid.

As the alkaline aqueous solution, a sodium hydroxide aqueous solution is preferred. Strontium titanate particles with better crystallinity tend to be obtained as the temperature at which the alkaline aqueous solution is added increases.
Regarding the addition rate of the alkaline aqueous solution, the slower the addition rate, the larger the strontium titanate particles obtained, and the faster the addition rate, the smaller the strontium titanate particles obtained. The addition rate of the alkaline aqueous solution is, for example, 0.001 equivalents/h or more and 1.2 equivalents/h or less, preferably 0.002 equivalents/h or more and 1.1 equivalents/h or less, relative to the feedstock.

After adding the alkaline aqueous solution, an acid treatment is carried out for the purpose of removing the unreacted strontium source. For the acid treatment, for example, hydrochloric acid is used to adjust the pH of the reaction solution to 2.5 to 7.0, more preferably 4.5 to 6.0.
After the acid treatment, the reaction liquid is subjected to solid-liquid separation, and the solid content is dried to obtain strontium titanate particles.
The moisture content of the strontium titanate particles is controlled by adjusting the conditions for drying the solid content.
Further, when the surface of the strontium titanate particles is hydrophobized, the water content may be controlled by adjusting the drying conditions after the hydrophobization treatment.
Here, the drying conditions for controlling the moisture content are preferably, for example, a drying temperature of 90° C. or higher and 300° C. or lower (preferably 100° C. or higher and 150° C. or lower) and a drying time of 1 hour or longer and 15 hours or shorter (preferably 5 hours or more and 10 hours or less).

-Hydrophobic treatment The surface of the strontium titanate particles is hydrophobized by, for example, preparing a treatment liquid by mixing a silicon-containing organic compound as a hydrophobizing agent and a solvent, and stirring the mixture with the strontium titanate particles. It is carried out by mixing with the treatment liquid and continuing stirring.
After the surface treatment, a drying treatment is performed for the purpose of removing the solvent of the treatment liquid.

Examples of silicon-containing organic compounds used as hydrophobizing agents include alkoxysilane compounds, silazane compounds, and silicone oils.

Examples of alkoxysilane compounds used as hydrophobizing agents include tetramethoxysilane, tetraethoxysilane; methyltrimethoxysilane, ethyltrimethoxysilane, propyltrimethoxysilane, butyltrimethoxysilane, hexyltrimethoxysilane, and n-octyl. trimethoxysilane, decyltrimethoxysilane, dodecyltrimethoxysilane, vinyltriethoxysilane, methyltriethoxysilane, ethyltriethoxysilane, butyltriethoxysilane, hexyltriethoxysilane, decyltriethoxysilane, dodecyltriethoxysilane, phenyl trimethoxysilane, o-methylphenyltrimethoxysilane, p-methylphenyltrimethoxysilane, phenyltriethoxysilane, benzyltriethoxysilane; dimethyldimethoxysilane, dimethyldiethoxysilane, methylvinyldimethoxysilane, methylvinyldiethoxysilane, diphenyldimethoxysilane, diphenyldiethoxysilane; trimethylmethoxysilane, trimethylethoxysilane;

Examples of silazane compounds that are hydrophobizing agents include dimethyldisilazane, trimethyldisilazane, tetramethyldisilazane, pentamethyldisilazane, and hexamethyldisilazane.

Examples of silicone oils used as hydrophobizing agents include silicone oils such as dimethylpolysiloxane, diphenylpolysiloxane, and phenylmethylpolysiloxane; amino-modified polysiloxane, epoxy-modified polysiloxane, carboxyl-modified polysiloxane, and carbinol-modified polysiloxane. , fluorine-modified polysiloxane, methacryl-modified polysiloxane, mercapto-modified polysiloxane, phenol-modified polysiloxane, and other reactive silicone oils;

Among these, as the hydrophobizing agent, an alkoxysilane compound is preferably used from the viewpoint of improving the charging environment difference and fluidity, and butyltrimethoxysilane is particularly preferable from the viewpoint of fluidity improvement.

As the solvent used for preparing the treatment liquid, when the silicon-containing organic compound is an alkoxysilane compound or a silazane compound, alcohol (e.g., methanol, ethanol, propanol, butanol) is preferable, and the silicon-containing organic compound is silicone oil. In some cases, hydrocarbons (eg, benzene, toluene, normal hexane, normal heptane) are preferred.

In the treatment liquid, the concentration of the silicon-containing organic compound is preferably 1% by mass or more and 50% by mass or less, more preferably 5% by mass or more and 40% by mass or less, and even more preferably 10% by mass or more and 30% by mass or less.

As described above, the amount of the silicon-containing organic compound used for the hydrophobic treatment is preferably 1% by mass or more and 50% by mass or less, more preferably 5% by mass or more and 40% by mass or less, relative to the mass of the strontium titanate particles. It is more preferably 5% by mass or more and 30% by mass or less, and particularly preferably 10% by mass or more and 25% by mass or less.

As described above, strontium titanate particles having a hydrophobized surface are obtained.

Externally added amount The externally added amount of the strontium titanate particles is preferably 0.1 parts by mass or more and 5 parts by mass or less, more preferably 0.5 parts by mass or more and 3 parts by mass or less, with respect to 100 parts by mass of the toner particles. 0.7 parts by mass or more and 2 parts by mass or less is more preferable.

[Particles other than strontium titanate particles]
The toner according to the present embodiment may contain particles other than the above-described strontium titanate as an external additive.
Other particles include inorganic particles other than strontium titanate particles.
Other _inorganic particles include _SiO2 , _TiO2 , _Al2O3 , CuO, ZnO, _SnO2 , _CeO2 , _Fe2O3 , _MgO , BaO, CaO, _K2O , _Na2O , _ZrO2 , CaO * _SiO2 , _K2O *( _TiO2 )n, _{Al2O3 * 2SiO2} , _CaCO3 , _MgCO3 , _BaSO4 , _MgSO4 etc. are mentioned.

The surfaces of the inorganic particles used as the external additive are preferably subjected to a hydrophobic treatment. The hydrophobizing treatment is performed, for example, by immersing the inorganic particles in a hydrophobizing agent. The hydrophobizing agent is not particularly limited, and examples thereof include silane coupling agents, silicone oils, titanate coupling agents, aluminum coupling agents and the like. These may be used individually by 1 type, and may use 2 or more types together.
The amount of the hydrophobizing agent is usually 1 part by mass or more and 10 parts by mass or less with respect to 100 parts by mass of the inorganic particles.

Other particles include resin particles (resin particles of polystyrene, polymethyl methacrylate, melamine resin, etc.), cleaning active agents (for example, fluorine-based high molecular weight particles), and the like.

When the additive in the present embodiment contains particles other than strontium titanate particles, the content of particles other than strontium titanate particles in all particles is preferably 15 mass % or less, and 3 mass % or more and 10 mass %. It is more preferably 4% by mass or more and 8% by mass or less.

[Toner particles]
The toner particles contain, for example, a binder resin, and optionally a colorant, a release agent, and other additives.
In the present embodiment, the toner particles may be, for example, toner particles such as yellow toner, magenta toner, cyan toner, and black toner, as well as white toner particles, transparent toner particles, glitter toner particles, and the like. There are no restrictions.

- Binder resin -
Examples of binder resins include styrenes (eg, styrene, parachlorostyrene, α-methylstyrene, etc.), (meth)acrylic acid esters (eg, methyl acrylate, ethyl acrylate, n-propyl acrylate, acrylic acid n-butyl, lauryl acrylate, 2-ethylhexyl acrylate, methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, lauryl methacrylate, 2-ethylhexyl methacrylate, etc.), ethylenically unsaturated nitriles (e.g. acrylonitrile, methacrylonitrile, etc.), vinyl ethers (e.g., vinyl methyl ether, vinyl isobutyl ether, etc.), vinyl ketones (e.g., vinyl methyl ketone, vinyl ethyl ketone, vinyl isopropenyl ketone, etc.), olefins (e.g., ethylene, propylene, butadiene, etc.) or a copolymer of two or more of these monomers in combination.
Examples of the binder resin include non-vinyl resins such as epoxy resins, polyester resins, polyurethane resins, polyamide resins, cellulose resins, polyether resins, modified rosin, mixtures of these with the vinyl resins, or A graft polymer obtained by polymerizing a vinyl-based monomer in the coexistence thereof may also be used.
One of these binder resins may be used alone, or two or more thereof may be used in combination.

A polyester resin is suitable as the binder resin. Examples of polyester resins include condensation polymers of polyhydric carboxylic acids and polyhydric alcohols.

Examples of polyvalent carboxylic acids include aliphatic dicarboxylic acids (e.g. oxalic acid, malonic acid,
maleic acid, fumaric acid, citraconic acid, itaconic acid, glutaconic acid, succinic acid, alkenylsuccinic acid, adipic acid, sebacic acid, etc.), alicyclic dicarboxylic acids (e.g., cyclohexanedicarboxylic acid, etc.), aromatic dicarboxylic acids (e.g., terephthalic acid) acid, isophthalic acid, phthalic acid, naphthalenedicarboxylic acid, etc.), anhydrides thereof, or lower alkyl esters thereof (for example, having 1 to 5 carbon atoms). Among these, for example, aromatic dicarboxylic acids are preferred as polyvalent carboxylic acids.
As the polycarboxylic acid, a dicarboxylic acid and a tricarboxylic or higher carboxylic acid having a crosslinked or branched structure may be used in combination. Examples of trivalent or higher carboxylic acids include trimellitic acid, pyromellitic acid, anhydrides thereof, and lower (for example, 1 to 5 carbon atoms) alkyl esters thereof.
Polyvalent carboxylic acid may be used individually by 1 type, and may use 2 or more types together.

Polyhydric alcohols include, for example, aliphatic diols (eg, ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, butanediol, hexanediol, neopentyl glycol, etc.), alicyclic diols (eg, cyclohexanediol, cyclohexanedimethanol, hydrogenated bisphenol A, etc.), aromatic diols (eg, ethylene oxide adduct of bisphenol A, propylene oxide adduct of bisphenol A, etc.). Among these, as the polyhydric alcohol, for example, aromatic diols and alicyclic diols are preferred, and aromatic diols are more preferred.
As the polyhydric alcohol, a trihydric or higher polyhydric alcohol having a crosslinked structure or a branched structure may be used together with the diol. Examples of trihydric or higher polyhydric alcohols include glycerin, trimethylolpropane, and pentaerythritol.
One type of polyhydric alcohol may be used alone, or two or more types may be used in combination.

The glass transition temperature (Tg) of the polyester resin is preferably 50°C or higher and 80°C or lower, more preferably 50°C or higher and 65°C or lower.
The glass transition temperature is obtained from a DSC curve obtained by differential scanning calorimetry (DSC). outer glass transition start temperature".

The weight average molecular weight (Mw) of the polyester resin is preferably from 5,000 to 1,000,000, more preferably from 7,000 to 500,000. The number average molecular weight (Mn) of the polyester resin is preferably 2,000 or more and 100,000 or less. The molecular weight distribution Mw/Mn of the polyester resin is preferably from 1.5 to 100, more preferably from 2 to 60.
The weight average molecular weight and number average molecular weight of the polyester resin are measured by gel permeation chromatography (GPC). Molecular weight measurement by GPC is performed using Tosoh's GPC HLC-8120GPC as a measuring apparatus, using a Tosoh column TSKgel SuperHM-M (15 cm), and using THF solvent. The weight average molecular weight and number average molecular weight are calculated from these measurement results using a molecular weight calibration curve prepared from monodisperse polystyrene standard samples.

A polyester resin is obtained by a known production method. Specifically, for example, the polymerization temperature is set to 180° C. or higher and 230° C. or lower, and the pressure in the reaction system is reduced as necessary to remove water and alcohol generated during condensation while the reaction is performed.
If the raw material monomers do not dissolve or are not compatible with each other at the reaction temperature, a solvent with a high boiling point may be added as a dissolution aid to dissolve them. In this case, the polycondensation reaction is carried out while distilling off the solubilizing agent. If a monomer with poor compatibility is present, it is preferable to first condense the monomer with poor compatibility, the monomer and the acid or alcohol to be polycondensed, and then polycondense with the main component. .

The content of the binder resin is preferably 40% by mass or more and 95% by mass or less, more preferably 50% by mass or more and 90% by mass or less, and even more preferably 60% by mass or more and 85% by mass or less with respect to the entire toner particles.
Further, when the toner particles are white toner particles, the content of the binder resin is preferably 30% by mass or more and 85% by mass or less, more preferably 40% by mass or more and 60% by mass or less, with respect to the entire white toner particles. .

-coloring agent-
Examples of colorants include carbon black, chrome yellow, Hansa yellow, benzidine yellow, thren yellow, quinoline yellow, pigment yellow, permanent orange GTR, pyrazolone orange, vulcan orange, watch young red, permanent red, brilliant carmine 3B, brilliant Carmine 6B, Dupont Oil Red, Pyrazolone Red, Lithol Red, Rhodamine B Lake, Lake Red C, Pigment Red, Rose Bengal, Aniline Blue, Ultramarine Blue, Calco Oil Blue, Methylene Blue Chloride, Phthalocyanine Blue, Pigment Blue, Phthalocyanine Green, Pigments such as malachite green oxalate, titanium oxide, zinc oxide, calcium carbonate, basic lead carbonate, zinc sulfide-barium sulfate mixture, zinc sulfide, silicon dioxide, aluminum oxide; acridine, xanthene, azo, benzoquinone, azine-based, anthraquinone-based, thioindico-based, dioxazine-based, thiazine-based, azomethine-based, indico-based, phthalocyanine-based, aniline black-based, polymethine-based, triphenylmethane-based, diphenylmethane-based, thiazole-based dyes;

When the toner particles are white toner particles, a white pigment may be used as the colorant.
As the white pigment, titanium oxide and zinc oxide are preferred, and titanium oxide is more preferred.

The colorants may be used singly or in combination of two or more.

As for the coloring agent, a surface-treated coloring agent may be used as necessary, and a dispersing agent may be used in combination.

The content of the colorant is preferably 1% by mass or more and 30% by mass or less, more preferably 3% by mass or more and 15% by mass or less, relative to the entire toner particles.
When the toner particles are white toner particles, the content of the white pigment is preferably 15% by mass or more and 70% by mass or less, more preferably 20% by mass or more and 60% by mass or less, with respect to the entire white toner particles.

-Release agent-
Release agents include, for example, hydrocarbon waxes; natural waxes such as carnauba wax, rice wax and candelilla wax; synthetic or mineral/petroleum waxes such as montan wax; ester waxes such as fatty acid esters and montan acid esters. ; and the like. The release agent is not limited to this.

The melting temperature of the releasing agent is preferably 50° C. or higher and 110° C. or lower, more preferably 60° C. or higher and 100° C. or lower.
The melting temperature is determined from a DSC curve obtained by differential scanning calorimetry (DSC), according to the "melting peak temperature" described in JIS K7121-1987 "Method for measuring transition temperature of plastics".

The content of the release agent is preferably 1% by mass or more and 20% by mass or less, more preferably 5% by mass or more and 15% by mass or less, relative to the entire toner particles.

-Other additives-
Other additives include, for example, known additives such as magnetic substances, charge control agents, and inorganic powders. These additives are contained in the toner particles as internal additives.

[Characteristics of Toner Particles]
The toner particles may be toner particles having a single-layer structure, or toner particles having a so-called core-shell structure composed of a core portion (core particle) and a coating layer (shell layer) covering the core portion. may The toner particles having a core-shell structure are composed of, for example, a core containing a binder resin, a colorant and a release agent if necessary, and a coating layer containing the binder resin.

The volume average particle diameter (D50v) of the toner particles is preferably 2 μm or more and 10 μm or less, more preferably 4 μm or more and 8 μm or less.

The volume average particle diameter of the toner particles is measured using COULTER MULTISIZER II (manufactured by Beckman Coulter, Inc.) and ISOTON-II (manufactured by Beckman Coulter, Inc.) as an electrolytic solution.
In the measurement, 0.5 mg or more and 50 mg or less of the measurement sample is added to 2 ml of a 5 mass % aqueous solution of a surfactant (preferably sodium alkylbenzene sulfonate) as a dispersant. This is added to 100 ml or more and 150 ml or less of the electrolytic solution.
The electrolytic solution in which the sample was suspended was subjected to dispersion treatment for 1 minute with an ultrasonic disperser, and particles having a particle size in the range of 2 μm or more and 60 μm or less were separated from each particle by Coulter Multisizer II using an aperture with an aperture diameter of 100 μm. Measure the diameter. The number of particles sampled is 50,000.
Regarding the measured particle diameters, a volume-based cumulative distribution is drawn from the small diameter side, and the particle diameter at which the cumulative 50% is obtained is defined as the volume average particle diameter D50v.

In the present embodiment, the average circularity of the toner particles is not particularly limited, but is preferably 0.91 or more and 0.98 or less, more preferably 0.94 or more, from the viewpoint of improving the toner cleanability from the image carrier. 0.98 or less is more preferable, and 0.95 or more and 0.97 or less is still more preferable.
The strontium titanate particles having a small diameter and a rounded shape as described above can be dispersed on the surface of the toner particles without uneven distribution of the strontium titanate particles. This is the same even in the case of using toner particles with an irregular shape as described above, and the strontium titanate particles are not unevenly distributed in fine concave portions, and the strontium titanate particles are dispersed in a nearly uniform state on the surface of the toner particles. can.
In other words, even when toner particles having such an irregular shape are used, the configuration of the toner according to the present embodiment can be obtained, and fogging that occurs in images immediately after startup of the image forming apparatus can be suppressed.
Of course, even when spherical toner particles having an average circularity exceeding 0.98 are used, the configuration of the toner according to the present embodiment can be obtained, and fog that occurs in images immediately after startup of the image forming apparatus can be eliminated. can be suppressed.

In the present embodiment, the circularity of the toner particles is (the perimeter of a circle having the same area as the projected particle image)÷(the perimeter of the projected particle image), and the average circularity of the toner particles is the circularity of the toner particles. It is the degree of circularity at which cumulative 50% is obtained from the small side in the distribution. The average circularity of toner particles is obtained by analyzing at least 3000 toner particles with a flow type particle image analyzer. A specific measuring method will be described in [Examples] below.

The average circularity of the toner particles can be controlled, for example, by adjusting the stirring speed of the dispersion liquid, the temperature of the dispersion liquid, or the holding time of the dispersion liquid in the fusion/coalescence process when the toner particles are produced by the aggregation coalescence method. .

[Toner manufacturing method]
Next, a method for manufacturing the toner according to this embodiment will be described.
The toner according to the exemplary embodiment is obtained by externally adding an external additive to the toner particles after manufacturing the toner particles.

The toner particles may be produced by either a dry method (eg, kneading pulverization method, etc.) or a wet method (eg, aggregation coalescence method, suspension polymerization method, dissolution suspension method, etc.). These manufacturing methods are not particularly limited, and known manufacturing methods are employed. Among these, it is preferable to obtain toner particles by the aggregation coalescence method.

Specifically, for example, when toner particles are produced by an aggregation coalescence method,
A step of preparing a resin particle dispersion in which resin particles to be a binder resin are dispersed (resin particle dispersion preparation step); dispersion liquid), resin particles (other particles as necessary) are aggregated to form aggregated particles (aggregated particle forming step), and the aggregated particle dispersion in which the aggregated particles are dispersed is heated to aggregate. Toner particles are manufactured through a step of fusing and uniting particles to form toner particles (fusing and uniting step).

Details of each step will be described below.
In the following description, a method for obtaining toner particles containing a colorant and a release agent is described, and the colorant and release agent are used as necessary. Needless to say, additives other than colorants and release agents may be used.

-Resin particle dispersion preparation step-
For example, a colorant particle dispersion in which colorant particles are dispersed and a release agent particle dispersion in which release agent particles are dispersed are prepared together with a resin particle dispersion in which resin particles that serve as a binder resin are dispersed.

The resin particle dispersion is prepared, for example, by dispersing resin particles in a dispersion medium using a surfactant.

Examples of the dispersion medium used for the resin particle dispersion include an aqueous medium.
Examples of the aqueous medium 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.

Examples of surfactants include anionic surfactants such as sulfate-based, sulfonate-based, phosphate-based, and soap-based surfactants; cationic surfactants such as amine salt-type and quaternary ammonium salt-type; polyethylene glycol. nonionic surfactants such as surfactants, alkylphenol ethylene oxide adducts, and polyhydric alcohols. Among these, anionic surfactants and cationic surfactants are particularly exemplified. Nonionic surfactants may be used in combination with anionic surfactants or cationic surfactants.
Surfactants may be used singly or in combination of two or more.

As a method for dispersing the resin particles in the dispersion medium in the resin particle dispersion, for example, general dispersing methods such as a rotary shearing homogenizer, a ball mill having media, a sand mill, and a dyno mill can be used. Moreover, depending on the type of resin particles, the resin particles may be dispersed in the dispersion medium by a phase inversion emulsification method. In the phase inversion emulsification method, the resin to be dispersed is dissolved in a hydrophobic organic solvent in which the resin is soluble, and after neutralization by adding a base to the organic continuous phase (O phase), an aqueous medium (W phase ) to effect a phase inversion from W/O to O/W and disperse the resin in the form of particles in the aqueous medium.

The volume average particle diameter of the resin particles dispersed in the resin particle dispersion liquid is, for example, preferably 0.01 μm or more and 1 μm or less, more preferably 0.08 μm or more and 0.8 μm or less, and further preferably 0.1 μm or more and 0.6 μm or less. preferable.
The volume average particle diameter of the resin particles is determined by using a particle size distribution obtained by measurement with a laser diffraction particle size distribution analyzer (for example, LA-700, manufactured by Horiba, Ltd.). , the cumulative distribution is drawn from the small particle size side, and the particle size at which the cumulative 50% of all particles is obtained is measured as the volume average particle size D50v. The volume average particle size of particles in other dispersions is similarly measured.

The content of the resin particles contained in the resin particle dispersion is preferably 5% by mass or more and 50% by mass or less, more preferably 10% by mass or more and 40% by mass or less.

For example, a colorant particle dispersion and a release agent particle dispersion are also prepared in the same manner as the resin particle dispersion. In other words, regarding the volume average particle size, dispersion medium, dispersion method, and content of particles in the resin particle dispersion, the colorant particles dispersed in the colorant particle dispersion and the release agent particle dispersion The same applies to dispersed release agent particles.

-Agglomerated particle formation step-
Next, the resin particle dispersion, the colorant particle dispersion, and the releasing agent particle dispersion are mixed. Then, in the mixed dispersion, the resin particles, the colorant particles, and the release agent particles are heteroaggregated to form resin particles, colorant particles, and release agent particles having a diameter close to the diameter of the target toner particles. form agglomerated particles containing

Specifically, for example, a flocculant is added to the mixed dispersion, the pH of the mixed dispersion is adjusted to be acidic (for example, pH 2 or more and 5 or less), a dispersion stabilizer is added as necessary, and then the resin particles are mixed. (Specifically, for example, the glass transition temperature of the resin particles -30 ° C. or more and the glass transition temperature of -10 ° C. or less) is heated to agglomerate the particles dispersed in the mixed dispersion, form agglomerated particles.
In the aggregated particle forming step, for example, the mixed dispersion is stirred with a rotary shear homogenizer, and a flocculant is added at room temperature (for example, 25° C.) to adjust the pH of the mixed dispersion to acidic (for example, pH 2 or more and 5 or less). Then, heating may be performed after adding a dispersion stabilizer as necessary.

Examples of the aggregating agent include a surfactant having a polarity opposite to that of the surfactant contained in the mixed dispersion, an inorganic metal salt, and a bivalent or higher metal complex. When a metal complex is used as the aggregating agent, the amount of surfactant used is reduced, and charging characteristics are improved.
Additives that form complexes or similar bonds with the metal ions of the flocculant may optionally be used together with the flocculant. A chelating agent is preferably used as this additive.

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; inorganic metal salts such as polyaluminum chloride, polyaluminum hydroxide, and calcium polysulfide. polymer; and the like.
A water-soluble chelating agent may be used as the chelating agent. Examples of chelating agents include oxycarboxylic acids such as tartaric acid, citric acid, and gluconic acid; aminocarboxylic acids such as iminodiacetic acid (IDA), nitrilotriacetic acid (NTA), and ethylenediaminetetraacetic acid (EDTA); .
The amount of the chelating agent to be added is preferably 0.01 parts by mass or more and 5.0 parts by mass or less, more preferably 0.1 parts by mass or more and less than 3.0 parts by mass, based on 100 parts by mass of the resin particles.

－Fusion/union process－
Next, the aggregated particle dispersion in which the aggregated particles are dispersed is heated, for example, to a temperature higher than the glass transition temperature of the resin particles (for example, a temperature higher than the glass transition temperature of the resin particles by 10°C to 30°C) to remove the aggregated particles. They fuse and coalesce to form toner particles.

Toner particles are obtained through the above steps.
After obtaining the aggregated particle dispersion in which the aggregated particles are dispersed, the aggregated particle dispersion and the resin particle dispersion in which the resin particles are dispersed are further mixed to further adhere the resin particles to the surfaces of the aggregated particles. and heating the second aggregated particle dispersion in which the second aggregated particles are dispersed to fuse and coalesce the second aggregated particles to form a core The toner particles may be produced through a step of forming toner particles having a shell structure.

After the fusion/unification step, the toner particles formed in the solution are subjected to a known washing step, solid-liquid separation step, and drying step to obtain dry toner particles. 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. From the viewpoint of productivity, the drying step may be freeze drying, flash drying, fluidized drying, vibrating fluidized drying, or the like.

Then, the toner according to the exemplary embodiment is produced, for example, by adding an external additive to the obtained dry toner particles and mixing them. Mixing may be carried out using, for example, a V blender, a Henschel mixer, a Loedige mixer, or the like. Further, if necessary, a vibration sieving machine, an air sieving machine, or the like may be used to remove coarse toner particles.

<Electrostatic charge image developer>
The electrostatic charge image developer according to the exemplary embodiment contains at least the toner according to the exemplary embodiment. The electrostatic image developer according to this embodiment may be a one-component developer containing only the toner according to this embodiment, or may be a two-component developer in which the toner and carrier are mixed.

The carrier is not particularly limited and includes known carriers. Examples of carriers include coated carriers in which the surface of a core material made of magnetic powder is coated with a resin; magnetic powder-dispersed carriers in which magnetic powder is dispersed in a matrix resin; and porous magnetic powder impregnated with resin. resin-impregnated carrier; The magnetic powder-dispersed carrier and the resin-impregnated carrier may be carriers in which constituent particles of the carrier are used as a core material and the surface of the core material is coated with a resin.

Magnetic powders include, for example, magnetic metals such as iron, nickel and cobalt; magnetic oxides such as ferrite and magnetite; and the like.

Coating resins and matrix resins include, for example, polyethylene, polypropylene, polystyrene, polyvinyl acetate, polyvinyl alcohol, polyvinyl butyral, polyvinyl chloride, polyvinyl ether, polyvinyl ketone, vinyl chloride-vinyl acetate copolymer, styrene-acrylic acid. Ester copolymers, straight silicone resins containing organosiloxane bonds or modified products thereof, fluororesins, polyesters, polycarbonates, phenolic resins, epoxy resins and the like can be mentioned. The coating resin and matrix resin may contain additives such as conductive particles. Examples of conductive particles include particles of metals such as gold, silver, and copper, and particles of carbon black, titanium oxide, zinc oxide, tin oxide, barium sulfate, aluminum borate, potassium titanate, and the like.

In order to coat the surface of the core material with a resin, a method of coating with a coating layer forming solution in which a coating resin and various additives (used as necessary) are dissolved in an appropriate solvent can be used. The solvent is not particularly limited, and may be selected in consideration of the type of resin to be used, coating suitability, and the like. Specific resin coating methods include an immersion method in which the core material is immersed in the solution for forming the coating layer; a spray method in which the solution for forming the coating layer is sprayed onto the surface of the core material; A fluidized bed method in which a coating layer forming solution is sprayed; a kneader coater method in which a core material of a carrier and a coating layer forming solution are mixed in a kneader coater and then the solvent is removed;

The mixing ratio (mass ratio) of toner and carrier in the two-component developer is preferably toner:carrier=1:100 to 30:100, more preferably 3:100 to 20:100.

<Image forming apparatus, image forming method>
An image forming apparatus/image forming method according to the present embodiment will be described.
The image forming apparatus according to the present embodiment includes an image carrier, charging means for charging the surface of the image carrier, electrostatic image forming means for forming an electrostatic charge image on the surface of the charged image carrier, and electrostatic charging. developing means for storing an image developer and developing an electrostatic charge image formed on the surface of the image carrier with the electrostatic charge image developer as a toner image; and a recording medium for transferring the toner image formed on the surface of the image carrier. and a fixing means for fixing the toner image transferred to the surface of the recording medium. As the electrostatic charge image developer, the electrostatic charge image developer according to the exemplary embodiment is applied.

In the image forming apparatus according to the present embodiment, the charging process of charging the surface of the image carrier, the electrostatic charge image forming process of forming an electrostatic charge image on the surface of the charged image carrier, and the electrostatic charging process according to the present embodiment. a developing step of developing an electrostatic charge image formed on the surface of the image carrier as a toner image with an image developer; a transfer step of transferring the toner image formed on the surface of the image carrier to the surface of a recording medium; and a fixing step of fixing the toner image transferred onto the surface of the recording medium (image forming method according to the present embodiment).

The image forming apparatus according to the present embodiment is a direct transfer type apparatus for directly transferring a toner image formed on the surface of an image carrier onto a recording medium; An intermediate transfer type device that primarily transfers the toner image transferred onto the surface of the intermediate transfer body and then secondarily transfers the toner image onto the surface of the recording medium; after the toner image is transferred, the surface of the image carrier before charging is cleaned. A known image forming apparatus such as an apparatus equipped with a cleaning means; an apparatus equipped with a static elimination means for irradiating the surface of the image carrier with static elimination light to eliminate static before charging after the transfer of the toner image;
When the image forming apparatus according to the present embodiment is an intermediate transfer type apparatus, the transfer means includes, for example, an intermediate transfer body on which a toner image is transferred and a toner image formed on the surface of the image carrier. A configuration having primary transfer means for primary transfer onto the surface of the body and secondary transfer means for secondary transfer of the toner image transferred onto the surface of the intermediate transfer body onto the surface of the recording medium is applied.

In the image forming apparatus according to the present embodiment, for example, the portion including the developing means may have a cartridge structure (process cartridge) detachable from the image forming apparatus. As the process cartridge, for example, a process cartridge including developing means containing the electrostatic image developer according to the present embodiment is preferably used.

An example of the image forming apparatus according to the present embodiment will be described below, but the present invention is not limited to this. In the following description, the main parts shown in the drawings will be described, and the description of the other parts will be omitted.

FIG. 2 is a schematic configuration diagram showing an image forming apparatus according to this embodiment.
The image forming apparatus shown in FIG. 2 is a first electrophotographic system that outputs yellow (Y), magenta (M), cyan (C), and black (K) images based on color-separated image data. to fourth image forming units 10Y, 10M, 10C, and 10K (image forming means). These image forming units (hereinafter also simply referred to as "units") 10Y, 10M, 10C, and 10K are arranged side by side with a predetermined distance from each other in the horizontal direction. These units 10Y, 10M, 10C, and 10K may be process cartridges that are detachable from the image forming apparatus.

Above each unit 10Y, 10M, 10C, and 10K, an intermediate transfer belt (an example of an intermediate transfer member) 20 extends through each unit. The intermediate transfer belt 20 is wound around a drive roll 22 and a support roll 24 that are in contact with the inner surface of the intermediate transfer belt 20, and runs in the direction from the first unit 10Y to the fourth unit 10K. there is A force is applied to the support roll 24 in a direction away from the drive roll 22 by a spring or the like (not shown), and tension is applied to the intermediate transfer belt 20 wound around both. An intermediate transfer belt cleaning device 30 is provided on the image holding surface side of the intermediate transfer belt 20 so as to face the drive roll 22 .

Developing devices (an example of developing means) 4Y, 4M, 4C, and 4K of the units 10Y, 10M, 10C, and 10K each contain yellow, magenta, cyan, and black toner cartridges 8Y, 8M, 8C, and 8K. are supplied.

Since the first to fourth units 10Y, 10M, 10C, and 10K have the same configuration and operation, here the first unit for forming a yellow image arranged on the upstream side in the running direction of the intermediate transfer belt is used. 1 unit 10Y will be described as a representative.

The first unit 10Y has a photoreceptor 1Y acting as an image carrier. Around the photoreceptor 1Y, there is a charging roll (an example of a charging unit) 2Y that charges the surface of the photoreceptor 1Y to a predetermined potential, and the charged surface is exposed to a laser beam 3Y based on color-separated image signals. An exposure device (an example of an electrostatic charge image forming means) 3 for forming an electrostatic charge image by applying toner, a developing device (an example of a developing means) 4Y for supplying charged toner to the electrostatic charge image to develop the electrostatic charge image, and a developing device 4Y for developing the electrostatic charge image. A primary transfer roll (an example of primary transfer means) 5Y that transfers the toner image onto the intermediate transfer belt 20, and a photoreceptor cleaning device (image carrier cleaning means) that removes toner remaining on the surface of the photoreceptor 1Y after the primary transfer. Example) 6Y are arranged in order.

The primary transfer roll 5Y is arranged inside the intermediate transfer belt 20 and provided at a position facing the photoreceptor 1Y. A bias power source (not shown) that applies a primary transfer bias is connected to the primary transfer rolls 5Y, 5M, 5C, and 5K of each unit. Each bias power supply changes the value of the transfer bias applied to each primary transfer roll under the control of a controller (not shown).

The operation of forming a yellow image in the first unit 10Y will be described below.
First, prior to operation, the surface of the photoreceptor 1Y is charged to a potential of -600V to -800V by the charging roll 2Y.
The photoreceptor 1Y is formed by stacking a photoreceptor layer on a conductive substrate (for example, a volume resistivity of 1×10 ⁻⁶ Ωcm or less at 20° C.). This photosensitive layer normally has a high resistance (resistivity of general resin), but has the property of changing the specific resistance of the portion irradiated with the laser beam when irradiated with the laser beam. Therefore, the surface of the charged photoreceptor 1Y is irradiated with the laser beam 3Y from the exposure device 3 according to the image data for yellow sent from the controller (not shown). Thereby, an electrostatic charge image of a yellow image pattern is formed on the surface of the photoreceptor 1Y.

An electrostatic charge image is an image formed on the surface of the photoreceptor 1Y by charging.
As a result, the resistivity of the irradiated portion of the photosensitive layer decreases, and the charged charge on the surface of the photoreceptor 1Y flows, while the charge remains on the portion not irradiated with the laser beam 3Y. It is a negative latent image.
The electrostatic image formed on the photoreceptor 1Y rotates to a predetermined development position as the photoreceptor 1Y travels. At this development position, the electrostatic charge image on the photoreceptor 1Y is developed as a toner image by the developing device 4Y and visualized.

The developing device 4Y contains, for example, an electrostatic charge image developer containing at least yellow toner and carrier. The yellow toner is triboelectrically charged by being agitated inside the developing device 4Y, and has the same polarity (negative polarity) as the charged charge on the photoreceptor 1Y. One example) is held above. As the surface of the photoreceptor 1Y passes through the developing device 4Y, the yellow toner is electrostatically adhered to the static-eliminated latent image portion on the surface of the photoreceptor 1Y, and the latent image is developed with the yellow toner. be. The photoreceptor 1Y on which the yellow toner image is formed continues to run at a predetermined speed, and the toner image developed on the photoreceptor 1Y is conveyed to a predetermined primary transfer position.

When the yellow toner image on the photoreceptor 1Y is conveyed to the primary transfer position, the primary transfer bias is applied to the primary transfer roll 5Y, and the electrostatic force directed from the photoreceptor 1Y to the primary transfer roll 5Y acts on the toner image. The toner image on the photoreceptor 1Y is transferred onto the intermediate transfer belt 20. As shown in FIG. The transfer bias applied at this time has a (+) polarity opposite to the polarity (-) of the toner, and is controlled to +10 μA, for example, by a controller (not shown) in the first unit 10Y. The toner remaining on the photoreceptor 1Y is removed and collected by the photoreceptor cleaning device 6Y.

The primary transfer biases applied to the primary transfer rolls 5M, 5C, and 5K after the second unit 10M are also controlled according to the first unit.
In this way, the intermediate transfer belt 20 onto which the yellow toner image has been transferred by the first unit 10Y is sequentially conveyed through the second to fourth units 10M, 10C, and 10K, and the toner images of the respective colors are superimposed for multiple transfer. be done.

The intermediate transfer belt 20, on which the four-color toner images are multiple-transferred through the first to fourth units, consists of the intermediate transfer belt 20, the support roll 24 in contact with the inner surface of the intermediate transfer belt, and the image holding surface of the intermediate transfer belt 20. A secondary transfer portion is formed by a secondary transfer roll (an example of a secondary transfer means) 26 arranged on the side. On the other hand, a recording paper (an example of a recording medium) P is fed through a supply mechanism into the gap between the secondary transfer roll 26 and the intermediate transfer belt 20 at a predetermined timing, and the secondary transfer bias is applied to the support roll. 24. The transfer bias applied at this time has the same (-) polarity as the polarity (-) of the toner. is transferred onto the recording paper P. The secondary transfer bias at this time is determined according to the resistance detected by resistance detection means (not shown) for detecting the resistance of the secondary transfer portion, and is voltage-controlled.

The recording paper P to which the toner image has been transferred is sent to a pressure contact portion (nip portion) between a pair of fixing rolls in a fixing device (an example of fixing means) 28, and the toner image is fixed onto the recording paper P, and the fixed image is formed. It is formed. The recording paper P on which the fixing of the color image has been completed is carried out toward the discharge section, and a series of color image forming operations is completed.

Examples of the recording paper P onto which the toner image is transferred include plain paper used in electrophotographic copiers, printers, and the like. In addition to the recording paper P, an OHP sheet or the like can also be used as the recording medium. In order to further improve the smoothness of the image surface after fixing, it is preferable that the surface of the recording paper P is also smooth. preferably used.

<Process Cartridge, Toner Cartridge>
The process cartridge according to the present embodiment contains the electrostatic charge image developer according to the present embodiment, and develops the electrostatic charge image formed on the surface of the image carrier as a toner image with the electrostatic charge image developer. and is detachable from the image forming apparatus.

The process cartridge according to the present embodiment includes developing means and, if necessary, at least one selected from other means such as an image carrier, charging means, electrostatic image forming means, and transfer means. It may be a configuration.

An example of the process cartridge according to the present embodiment will be shown below, but the present invention is not limited to this. In the following description, the main parts shown in the drawings will be described, and the description of the other parts will be omitted.

FIG. 3 is a schematic configuration diagram showing an example of the process cartridge according to this embodiment.
The process cartridge 200 shown in FIG. 3 includes, for example, a photoreceptor 107 (an example of an image carrier) and a periphery of the photoreceptor 107 by means of a housing 117 having mounting rails 116 and an opening 118 for exposure. A charging roll 108 (an example of charging means), a developing device 111 (an example of developing means), and a photoreceptor cleaning device 113 (an example of cleaning means) are integrally combined and held, and formed into a cartridge. there is
In FIG. 3, 109 is an exposure device (an example of electrostatic image forming means), 112 is a transfer device (an example of transfer means), 115 is a fixing device (an example of fixing means), and 300 is recording paper (an example of a recording medium). is shown.

Next, the toner cartridge according to this embodiment will be described.
A toner cartridge according to the present embodiment is a toner cartridge that accommodates the toner according to the present embodiment and is detachable from an image forming apparatus. The toner cartridge accommodates replenishment toner to be supplied to developing means provided in the image forming apparatus.

The image forming apparatus shown in FIG. 2 is an image forming apparatus having a configuration in which toner cartridges 8Y, 8M, 8C, and 8K are detachable. Developing devices 4Y, 4M, 4C, and 4K include toner cartridges corresponding to respective colors. and are connected by a toner supply pipe (not shown). When the toner contained in the toner cartridge runs out, the toner cartridge is replaced.

The embodiments of the invention will be described in detail below with reference to examples, but the embodiments of the invention are not limited to these examples. In the following description, "parts" are based on mass unless otherwise specified.

<Production of strontium titanate particles>
[Strontium titanate particles (1)]
0.7 mol of metatitanic acid, which is the source of desulfurized and peptized titanium, was taken as TiO ₂ and put into a reaction vessel. Then, 0.77 mol of an aqueous strontium chloride solution was added to the reactor so that the SrO/TiO ₂ molar ratio was 1.1. Next, a solution of lanthanum oxide dissolved in nitric acid was added to the reactor in an amount of 5 mol of lanthanum per 100 mol of strontium. The initial TiO ₂ concentration in the mixture of the three materials was made to be 0.75 mol/L.
Then, the mixture is stirred, heated to 90 ° C., and while stirring while maintaining the liquid temperature at 90 ° C., 153 mL of a 10 N sodium hydroxide aqueous solution is added over 3.8 hours. Stirring was continued for 1 hour while maintaining the temperature at 90°C. Then, the reaction solution was cooled to 40° C., hydrochloric acid was added until the pH reached 5.5, and the solution was stirred for 1 hour. The precipitate was then washed by repeated decantation and dispersion in water. Hydrochloric acid was added to the washed slurry containing the precipitate to adjust the pH to 6.5, and solid-liquid separation was performed by filtration.
Subsequently, an alcohol solution of i-butyltrimethoxysilane was added to the obtained solid content (strontium titanate particles) in an amount of 20 parts of i-butyltrimethoxysilane per 100 parts of the solid content. Stirring was carried out for 1 hour.
Thereafter, solid-liquid separation was performed by filtration, and the solid content was dried in the air at 110° C. for 5 hours to obtain strontium titanate particles (1).

[Strontium titanate particles (2) to (14), (16)]
Amount of metatitanic acid used as TiO ₂ [mol], Amount of strontium chloride aqueous solution added (amount of SrO) [mol], SrO/TiO ₂ molar ratio, Amount of lanthanum added to 100 mol of strontium [mol], 10N hydroxide Addition amount [mL] of sodium aqueous solution, addition time [hours] of 10N sodium hydroxide aqueous solution, type of hydrophobizing agent and treatment amount [part] per 100 parts of solid content, and amount of strontium titanate particles after hydrophobization treatment. Strontium titanate particles (2) to (14) were prepared in the same manner as the strontium titanate particles (1), except that the drying temperature [°C] and the drying time were appropriately changed as shown in Table 1 below. was made.

[Strontium titanate particles (15)]
Strontium titanate particles ( 15) was produced.

<Preparation of Toner Particles>
[Toner particles (1)]
-Preparation of resin particle dispersion (1)-
・Terephthalic acid: 30 mol parts ・Fumaric acid: 70 mol parts ・Bisphenol A ethylene oxide adduct: 5 mol parts ・Bisphenol A propylene oxide adduct: 95 mol parts The above materials were placed in the equipped flask, the temperature was raised to 220° C. over 1 hour, and 1 part of titanium tetraethoxide was added to 100 parts of the above materials. The temperature was raised to 230° C. over 30 minutes while distilling off the generated water, and after continuing the dehydration condensation reaction at this temperature for 1 hour, the reactant was cooled. Thus, a polyester resin having a weight average molecular weight of 18,000 and a glass transition temperature of 60°C was obtained.

40 parts of ethyl acetate and 25 parts of 2-butanol were added to a container equipped with a temperature control means and a nitrogen substitution means to form a mixed solvent, and then 100 parts of a polyester resin was gradually added to dissolve the mixed solvent. % ammonia aqueous solution (equivalent to 3 times the molar acid value of the resin) was added and stirred for 30 minutes. Then, the inside of the container was replaced with dry nitrogen, the temperature was maintained at 40° C., and 400 parts of ion-exchanged water was added dropwise at a rate of 2 parts/minute while stirring the mixed solution. After completion of dropping, the temperature was returned to room temperature (20° C. to 25° C.), and dry nitrogen was bubbled for 48 hours while stirring to obtain a resin particle dispersion in which ethyl acetate and 2-butanol were reduced to 1000 ppm or less. Ion-exchanged water was added to the resin particle dispersion to adjust the solid content to 20 mass % to obtain a resin particle dispersion (1).

-Preparation of colorant particle dispersion (1)-
・Regal 330 (carbon black manufactured by Cabot Corporation): 70 parts ・Anionic surfactant (Daiichi Kogyo Seiyaku Co., Ltd., Neogen RK): 5 parts ・Ion-exchanged water: 200 parts Dispersed for 10 minutes using the name Ultra Turrax T50). Ion-exchanged water was added so that the solid content in the dispersion liquid was 20% by mass, to obtain a colorant particle dispersion liquid (1) in which colorant particles having a volume average particle diameter of 170 nm were dispersed.

-Preparation of Release Agent Particle Dispersion (1)-
・ Paraffin wax (Nippon Seiro, HNP-9): 100 parts ・ Anionic surfactant (Daiichi Kogyo Seiyaku, Neogen RK): 1 part ・ Ion-exchanged water: 350 parts Mix the above materials and heat to 100 ° C. After heating and dispersing using a homogenizer (IKA, trade name Ultra Turrax T50), dispersion treatment is performed with a Manton-Gaulin high-pressure homogenizer (Golin) to release release agent particles having a volume average particle diameter of 200 nm dispersed. A template particle dispersion (1) (solid content: 20% by mass) was obtained.

-Preparation of Toner Particles (1)-
- Resin particle dispersion (1): 403 parts - Colorant particle dispersion (1): 12 parts - Release agent particle dispersion (1): 50 parts - Anionic surfactant (TaycaPower): 2 Parts The above materials were placed in a round stainless steel flask, 0.1N nitric acid was added to adjust the pH to 3.5, and then 30 parts of an aqueous nitric acid solution having a polyaluminum chloride concentration of 10% by mass was added. Then, after dispersing at a liquid temperature of 30° C. using a homogenizer (IKA, trade name Ultra Turrax T50), the mixture was heated to 45° C. in a heating oil bath and held for 30 minutes. After that, 100 parts of resin particle dispersion (1) was added and held for 1 hour. After adjusting the pH to 8.0 by adding 0.1N aqueous sodium hydroxide solution, the mixture was heated to 84°C and held for 2.5 hours. bottom. Next, the mixture was cooled to 20° C. at a rate of 20° C./min, filtered, thoroughly washed with deionized water, and dried to obtain toner particles (1).
The obtained toner particles (1) had a volume average particle diameter of 5.7 μm and an average circularity of 0.95.

[Toner particles (2)]
100 parts of the resin particle dispersion (1) was added and held for 1 hour, and after adjusting the pH to 8.0 by adding a 0.1N sodium hydroxide aqueous solution, the mixture was heated to 84° C. and held for 2.0 hours. prepared toner particles (2) in the same manner as toner particles (1).
The obtained toner particles (2) had a volume average particle diameter of 5.7 μm and an average circularity of 0.93.

[Toner particles (3)]
-Preparation of colorant particle dispersion (W)-
・Titanium oxide particles (manufactured by Ishihara Sangyo Co., Ltd., product name: CR-60-2): 210 parts ・Anionic surfactant (Neogen RK manufactured by Daiichi Kogyo Seiyaku Co., Ltd.): 10 parts ・Ion-exchanged water: 480 parts or more The ingredients are mixed and stirred for 30 minutes using a homogenizer (IKA, trade name Ultra Turrax T50), and then dispersed for 1 hour using a high-pressure impact disperser Ultimizer (HJP30006: manufactured by Sugino Machine Co., Ltd.). , a white pigment particle dispersion (W) (solid content: 30% by mass) in which a white pigment having a volume average particle diameter of 210 nm was dispersed was obtained.

-Preparation of toner particles (3)-
Ion-exchanged water: 600 parts Resin particle dispersion (1): 400 parts Colorant particle dispersion (W): 325 parts Release agent particle dispersion (1): 78 parts Anionic interface Activator (TaycaPower): 8 parts Put the above materials in a round stainless steel flask, add 0.1 N nitric acid to adjust the pH to 3.5, and then add a nitric acid aqueous solution with a polyaluminum chloride concentration of 10% by mass. 13 parts were added. Then, after dispersion at a liquid temperature of 30° C. using a homogenizer (IKA, trade name Ultra Turrax T50), the mixture was heated to 45° C. in a heating oil bath and held for 60 minutes. Then, 100 parts of the resin particle dispersion (1) was added and the mixture was held for 1 hour, and after adjusting the pH to 8.5 by adding a 0.1N sodium hydroxide aqueous solution, the mixture was heated to 85° C. and held for 5 hours. Next, the mixture was cooled to 20° C. at a rate of 20° C./min, filtered, thoroughly washed with deionized water, and dried to obtain toner particles (3) which are white toner particles.
The obtained toner particles (3) had a volume average particle diameter of 7.5 μm and an average circularity of 0.95.

<Production of carrier>
A carrier prepared as follows was used.
・Ferrite particles (volume average particle diameter: 36 μm) 100 parts ・Toluene 14 parts ・Styrene-methyl methacrylate copolymer 2 parts (Component ratio: 90/10, Mw = 80000)
Carbon black (R330: manufactured by Cabot Corporation) 0.2 parts First, the above components except ferrite particles were stirred with a stirrer for 10 minutes to prepare a dispersed coating liquid, and then this coating liquid and ferrite particles were mixed. The mixture was placed in a vacuum degassing kneader, stirred at 60° C. for 30 minutes, degassed under reduced pressure while being heated, and dried to obtain a carrier.

[Preparation of Toner and Developer: Example 1]
To 100 parts of toner particles (1), 0.95 parts of strontium titanate particles (1) were added as an external additive, and mixed with a Henschel mixer at a peripheral speed of 30 m/sec for 15 minutes to obtain a toner.

Then, each toner and carrier thus obtained were placed in a V blender at a ratio of toner:carrier=8:92 (mass ratio) and stirred for 20 minutes to obtain a developer.

[Preparation of Toner and Developer: Examples 2 to 11, 13, Comparative Examples 1 to 4]
A toner and a developer were produced in the same manner as in Example 1, except that the strontium titanate particles (1) were changed to the strontium titanate particles shown in Table 2 below.

[Preparation of Toner and Developer: Example 12]
A toner and a developer were prepared in the same manner as in Example 1, except that toner particles (1) were changed to toner particles (2).

[Preparation of Toner and Developer: Example 14]
A toner and a developer were prepared in the same manner as in Example 1, except that toner particles (1) were changed to toner particles (3).

<Various analyses>
[Shape characteristics of strontium titanate particles]
Images of the toner were taken at a magnification of 40,000 times using a scanning electron microscope (SEM) (Hitachi High-Technologies Corporation, S-4800) equipped with an EDX device (Horiba Corporation, EMAX Evolution X-Max80 mm ² ). . EDX analysis identified more than 300 primary particles of strontium titanate within one field of view based on the presence of Ti and Sr. The SEM was observed at an acceleration voltage of 15 kV, an emission current of 20 μA, and a WD of 15 mm, and the EDX analysis was performed under the same conditions with a detection time of 60 minutes.
The specified strontium titanate particles are analyzed with image processing analysis software WinRoof (Mitani Shoji Co., Ltd.) to obtain the equivalent circle diameter, area, and perimeter of each primary particle image. (Perimeter) ² was obtained. Then, in the equivalent circle diameter distribution, the equivalent circle diameter that is cumulatively 50% from the small diameter side is defined as the average primary particle diameter, and the circularity that is cumulatively 50% from the small side in the circularity distribution is defined as the average circularity. The cumulative 84% circularity was defined as the cumulative 84% circularity from the smaller side of the distribution. The standard deviation was also obtained from the circularity distribution.
Table 2 summarizes the obtained values.

[Surface coverage]
For the toner, the surface coverage was measured under the measurement conditions described above.
Table 2 shows the results.

[X-ray diffraction of strontium titanate particles]
Using each of the strontium titanate particles before being externally added to the toner particles as a sample, crystal structure analysis was performed by the X-ray diffraction method under the measurement conditions described above.
The strontium titanate particles (1) to (10) have a peak corresponding to the peak of the (110) plane of the perovskite crystal near the diffraction angle 2θ=32°, and the half-value width of each peak is 0.5. It was in the range of 2° or more and 0.5° or less.

[Water content of strontium titanate particles]
Using each of the strontium titanate particles before being externally added to the toner particles as a sample, the moisture content was measured by the measurement method described above.
Table 1 shows the measurement results.

[Mass ratio of strontium titanate particles (Si/Sr)]
Using each of the strontium titanate particles before being externally added to the toner particles as a sample, the mass ratio (Si/Sr) was measured by the measurement method described above.
Table 1 shows the measurement results.

[Average Circularity of Toner Particles]
Toner particles before external addition of external additives are analyzed with a flow type particle image analyzer (manufactured by Sysmex, FPIA-3000). (peripheral length of the projected image of the particles) was obtained, and the average circularity of the toner particles was defined as the cumulative 50% circularity from the small side in the circularity distribution of 3000 toner particles.

When the external additive is externally added to the toner particles, the above measurement is performed after removing the external additive having a relatively large particle size (for example, the external additive having a primary particle size of 100 nm or more). The operation for removing the external additive is as follows.
In a 200 mL glass bottle, 0.2 wt% Triton X-100 aqueous solution (Acros Or
ganics) and 2 g of toner are added and dispersed by stirring 500 times. Next, while maintaining the liquid temperature of the dispersion at 20° C.±0.5° C., ultrasonic waves are applied using an ultrasonic homogenizer (manufactured by Nippon Seiki Seisakusho, US-300AT). The ultrasonic waves are applied for a duration of 300 seconds, an output of 75 W, an amplitude of 180 μm, and a distance of 10 mm between the ultrasonic transducer and the bottom of the container. Then, the dispersion is centrifuged at 3000 rpm for 2 minutes at a cooling temperature of 0 ° C. using a small high-speed refrigerated centrifuge (manufactured by Sakuma Seisakusho, M201-IVD), the supernatant is removed, and the remaining slurry is filtered with filter paper (manufactured by Advantech , qualitative filter paper No. 5C, 110 nm). The residue on the filter paper is washed twice with deionized water and dried to obtain a measurement sample.

<Evaluation>
The obtained developer of each example was accommodated in a developing device of a remodeled image forming apparatus "ApeosPort-IV C5575 (manufactured by Fuji Xerox Co., Ltd.)" (a remodeled machine in which an automatic density control sensor for environmental fluctuations was turned off).
Using this remodeled image forming apparatus, the power supply of the image forming apparatus can be changed under a high temperature and high humidity environment (under 28°C/85% RH environment) and under a low temperature and low humidity environment (under 10°C/15% RH environment). Immediately after the addition of the toner, fog evaluation was carried out when images having an image density of 1% were continuously output on 30 sheets of A4 paper. Table 2 shows the evaluation results.
Evaluation criteria are as follows.
G1: No fog is observed on all 30 sheets.
G2: Fog is slightly observed on one sheet, but within a practically acceptable range.
G3: Slight fogging is observed on a plurality of sheets, but within a practically acceptable range.
G4: Obvious fogging is observed on a plurality of sheets, not suitable for practical use.
G5: Fog is observed on all 30 sheets.

1Y, 1M, 1C, 1K photoreceptors (examples of image carriers)
2Y, 2M, 2C, 2K charging roll (an example of charging means)
3 Exposure device (an example of electrostatic charge image forming means)
3Y, 3M, 3C, 3K laser beams 4Y, 4M, 4C, 4K developing device (an example of developing means)
5Y, 5M, 5C, 5K primary transfer roll (an example of primary transfer means)
6Y, 6M, 6C, 6K Photoreceptor cleaning device (an example of image carrier cleaning means) 8Y, 8M, 8C, 8K Toner cartridge 10Y, 10M, 10C, 10K Image forming unit 20 Intermediate transfer belt (an example of intermediate transfer member)
22 drive roll
24 support roll 26 secondary transfer roll (an example of secondary transfer means)
28 fixing device (an example of fixing means)
30 intermediate transfer belt cleaning device (an example of intermediate transfer member cleaning means)
P recording paper (an example of a recording medium)

107 photoreceptor (an example of an image carrier)
108 charging roll (an example of charging means)
109 exposure device (an example of electrostatic charge image forming means)
111 developing device (an example of developing means)
112 transfer device (an example of transfer means)
113 photoreceptor cleaning device (an example of image carrier cleaning means)
115 fixing device (an example of fixing means)
116 mounting rail 117 housing 118 opening 200 for exposure process cartridge 300 recording paper (an example of a recording medium)

Claims (20)

comprising toner particles and strontium titanate particles externally added to the toner particles;
The strontium titanate particles present on the surface of the toner particles have an average primary particle size of 30 nm or more and 100 nm or less, an average circularity of the primary particles of 0.82 or more and 0.94 or less, and a cumulative total of primary particles of 84 % circularity is more than 0.92,
The strontium titanate particles are strontium titanate particles doped with a metal element other than titanium and strontium and having a surface subjected to a hydrophobic treatment with a silicon-containing organic compound,
A toner for electrostatic charge image development, wherein the water content of the strontium titanate particles is 2% or more and 5% or less. The mass ratio (Si/Sr) of silicon (Si) and strontium (Sr) calculated from qualitative and quantitative analysis of fluorescent X-ray analysis of the strontium titanate particles is 0.025 or more and 0.25 or less. Item 2. The toner for electrostatic charge image development according to item 1. 3. The toner for electrostatic charge image development according to claim 1, wherein the strontium titanate particles present on the surfaces of the toner particles have a standard deviation of circularity of primary particles of 0.04 or more and 2.0 or less. toner. 4. The toner for electrostatic charge image development according to claim 3, wherein the strontium titanate particles present on the surface of the toner particles have a standard deviation of circularity of primary particles of 0.04 or more and 1.0 or less. 5. The strontium titanate particles according to any one of claims 1 to 4, wherein the surface contains a silicon-containing organic compound in an amount of 5% by mass or more and 30% by mass or less relative to the mass of the strontium titanate particles. toner for developing electrostatic charge images. 6. The toner for electrostatic charge image development according to claim 5, wherein the strontium titanate particles have the surface containing the silicon-containing organic compound in an amount of 10% by mass or more and 25% by mass or less relative to the mass of the strontium titanate particles. The toner for electrostatic image development according to any one of claims 1 to 6, wherein the silicon-containing organic compound is at least one selected from the group consisting of alkoxysilane compounds and silicone oils. 8. The toner for electrostatic charge image development according to claim 1, wherein the surface coverage of the strontium titanate particles with respect to the toner particles is 3% or more and 50% or less. 9. The toner for electrostatic charge image development according to claim 8, wherein the surface coverage of the strontium titanate particles with respect to the toner particles is 5% or more and 30% or less. The toner for electrostatic charge image development according to any one of claims 1 to 9, wherein the strontium titanate particles are lanthanum-doped strontium titanate particles. The toner according to any one of claims 1 to 10, wherein the strontium titanate particles present on the surface of the toner particles have an average primary particle diameter of 30 nm or more and 80 nm or less. 12. The toner for electrostatic charge image development according to claim 11, wherein the strontium titanate particles present on the surface of the toner particles have an average primary particle size of 30 nm or more and 60 nm or less. 13. The toner for electrostatic charge image development according to claim 1, wherein the toner particles have an average circularity of 0.91 or more and 0.98 or less. 14. The toner for electrostatic charge image development according to claim 13, wherein the toner particles have an average circularity of 0.93 or more and 0.97 or less. The toner for electrostatic image development according to any one of claims 1 to 14, wherein the toner particles are white toner particles. An electrostatic charge image developer containing the electrostatic charge image developing toner according to any one of claims 1 to 15. containing the electrostatic charge image developing toner according to any one of claims 1 to 15,
A toner cartridge that is attached to and detached from an image forming apparatus. 17. A developing means for accommodating the electrostatic charge image developer according to claim 16 and developing the electrostatic charge image formed on the surface of the image carrier by the electrostatic charge image developer as a toner image,
A process cartridge that is attached to and detached from an image forming apparatus. an image carrier;
charging means for charging the surface of the image carrier;
electrostatic charge image forming means for forming an electrostatic charge image on the surface of the charged image carrier;
17. Developing means for accommodating the electrostatic charge image developer according to claim 16 and developing the electrostatic charge image formed on the surface of the image carrier by the electrostatic charge image developer as a toner image;
a transfer means for transferring the toner image formed on the surface of the image carrier onto the surface of a recording medium;
fixing means for fixing the toner image transferred onto the surface of the recording medium;
An image forming apparatus comprising: a charging step of charging the surface of the image carrier;
an electrostatic charge image forming step of forming an electrostatic charge image on the surface of the charged image carrier;
a developing step of developing the electrostatic charge image formed on the surface of the image carrier as a toner image with the electrostatic charge image developer according to claim 16;
a transfer step of transferring the toner image formed on the surface of the image carrier onto the surface of a recording medium;
a fixing step of fixing the toner image transferred onto the surface of the recording medium;
An image forming method comprising:

Images