JP2019028428A - Toner for electrostatic charge image development, electrostatic charge image developer, toner cartridge, process cartridge, image forming apparatus, and image forming method - Google Patents

Abstract

To provide a toner for electrostatic charge image development that can control fogging occurring in an image immediately after the start-up of an image forming apparatus.SOLUTION: A toner for electrostatic charge image development contains toner particles and strontium titanate particles externally added to the toner particles. The strontium titanate particles present on the surface of the toner particles has an average primary particle diameter of 30 nm or more and 100 nm or less, where primary particles have an average circularity of 0.82 or more and 0.94 or less, and the primary particles have an accumulation 84% circularity of more than 0.92.SELECTED DRAWING: None

Description

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

  Patent Document 1 discloses toner and abrasive particles having an average primary particle diameter of 30 nm to 300 nm, a cubic particle shape and / or a rectangular parallelepiped particle shape, and a perovskite crystal. A developer comprising strontium titanate particles is disclosed.

In Patent Document 2, strontium titanate having a BET specific surface area of 20 to 50 m ² / g and containing cuboid 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 developing an electrostatic charge image, in which charge adjusting particles made of strontium titanate surface-treated with silicone oil are attached and / or buried on the surface of colored particles.

  Patent Document 4 discloses a two-component developer containing 0.1 to 1.0 part 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.

JP 2011-203758 A Japanese Patent No. 5248511 JP 2011-137980 A 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 size of 30 nm to 100 nm, and the primary particles have an average circularity of 0.82 to 0.94. When the circularity at which 84% of the particles are accumulated is 0.92 or less, or the average circularity of the primary particles is from 0.82 to 0.94, and the circularity at which 84% of the primary particles are accumulated is 0. It is an object to provide a toner for developing an electrostatic charge image that can suppress fogging generated in an image immediately after start-up of an image forming apparatus as compared with a case where the average primary particle diameter is less than 30 nm while being over .92. And

The above problem is solved by the following means.
The invention according to claim 1
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 to 100 nm, an average circularity of the primary particles of 0.82 to 0.94, and a cumulative primary particle of 84 A toner for developing electrostatic images having a circularity of% exceeding 0.92.

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

The invention according to claim 4
4. The electrostatic image developing toner according to claim 1, wherein a water content of the strontium titanate particles is 1.5% or more and 10% or less. 5.
The invention according to claim 5
The electrostatic image developing toner according to claim 4, wherein the water content of the strontium titanate particles is 2% or more and 5% or less.

The invention according to claim 6
The electrostatic image developing toner according to claim 1, wherein the strontium titanate particles have a surface subjected to a hydrophobic treatment.
The invention according to claim 7 provides:
The toner for developing an electrostatic charge image according to claim 6, wherein the strontium titanate particles have a surface subjected to a hydrophobic treatment with a silicon-containing organic compound.
The invention according to claim 8 provides:
The toner for developing an electrostatic charge image according to claim 7, wherein the strontium titanate particles have the surface containing a silicon-containing organic compound in an amount of 5% by mass to 30% by mass with respect to the mass of the strontium titanate particles.
The invention according to claim 9 is:
The toner for developing an electrostatic charge image according to claim 8, wherein the strontium titanate particles have the surface containing 10% by mass or more and 25% by mass or less of a silicon-containing organic compound with respect to the mass of the strontium titanate particles.
The invention according to claim 10 is:
The electrostatic image developing toner according to claim 7, wherein the silicon-containing organic compound is at least one selected from the group consisting of an alkoxysilane compound and a silicone oil.
The invention according to claim 11 is:
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 11. The toner for developing an electrostatic charge image according to any one of Items 7 to 10.

The invention according to claim 12
12. The electrostatic image developing toner according to claim 1, wherein a 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 claim 13 is:
The electrostatic charge image developing toner according to claim 12, wherein a 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 claim 14 is:
The toner for developing an electrostatic charge image according to any one of claims 1 to 13, wherein the strontium titanate particles are strontium titanate particles doped with metal elements other than titanium and strontium.
The invention according to claim 15 is:
The electrostatic image developing toner according to claim 14, wherein the strontium titanate particles are strontium titanate particles doped with lanthanum.

The invention according to claim 16 provides:
16. The electrostatic image developing toner according to claim 1, 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 claim 17 provides:
The electrostatic image developing toner according to claim 16, wherein the strontium titanate particles present on the surface of the toner particles have an average primary particle size of 30 nm to 60 nm.

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

The invention according to claim 20 provides
The electrostatic image developing toner according to claim 1, wherein the toner particles are white toner particles.

The invention according to claim 21 is
An electrostatic charge image developer comprising the electrostatic charge image developing toner according to any one of claims 1 to 20.

The invention according to claim 22 is
An electrostatic charge image developing toner according to any one of claims 1 to 20, containing the toner,
A toner cartridge to be attached to and detached from the image forming apparatus.

The invention according to claim 23 is
A developing means for accommodating the electrostatic charge image developer according to claim 21 and developing the electrostatic charge image formed on the surface of the image holding member as a toner image by the electrostatic charge image developer,
A process cartridge attached to and detached from the image forming apparatus.

The invention according to claim 24 provides
An image carrier,
Charging means for charging the surface of the image carrier;
An electrostatic charge image forming means for forming an electrostatic charge image on the surface of the charged image carrier;
A developing unit that contains the electrostatic charge image developer according to claim 21 and that develops the electrostatic charge image formed on the surface of the image carrier as a toner image with the electrostatic charge image developer,
Transfer means for transferring a toner image formed on the surface of the image carrier to the surface of a recording medium;
Fixing means for fixing the toner image transferred to the surface of the recording medium;
An image forming apparatus comprising:

The invention according to claim 25 is
A charging step for 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 image formed on the surface of the image carrier as a toner image with the electrostatic image developer according to claim 21;
A transfer step of transferring a toner image formed on the surface of the image carrier to the surface of a recording medium;
A fixing step of fixing the toner image transferred to the surface of the recording medium;
An image forming method comprising:

  According to the invention of claim 1, 16, 17, 18, 19, or 20, in the strontium titanate particles present on the surface of the toner particles, the average primary particle size is 30 nm or more and 100 nm or less, and the average of the primary particles When the circularity is 0.82 or more and 0.94 or less but the circularity that is 84% of the accumulation of primary particles is 0.92 or less, or the average circularity of the primary particles is 0.82 or more and 0.00. It occurs in an image immediately after the start-up of the image forming apparatus as compared with the case where the average primary particle diameter is less than 30 nm while the circularity that is 94 or less and the cumulative primary particle size is 84% is more than 0.92. An electrostatic image developing toner capable of suppressing fogging is provided.

  According to the invention according to claim 2 or 3, the electrostatic charge image capable of suppressing the fog generated in the image immediately after the start-up of the image forming apparatus as compared with the case where the standard deviation of the strontium titanate particles is less than 0.04. A developing toner is provided.

  According to the invention according to claim 4 or 5, the fog generated in the image immediately after the start-up of the image forming apparatus as compared with the case where the water content of the strontium titanate particles is less than 1.5% by mass or more than 10% by mass. An electrostatic charge image developing toner capable of suppressing the above is provided.

  According to the invention of claim 6 or 10, the electrostatic charge that can suppress the fog generated in the image immediately after the start-up of the image forming apparatus, as compared with the case where the strontium titanate particles do not have a hydrophobized surface. An image developing toner is provided.

  According to the invention according to claim 7, 8, or 9, image formation is performed as compared with the case where the surface contains 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. There is provided an electrostatic image developing toner capable of suppressing fogging generated in an image immediately after starting up the apparatus.

  According to the invention of claim 11, the mass ratio (Si / Sr) of silicon (Si) and strontium (Sr) calculated from the qualitative and quantitative analysis of the fluorescent X-ray analysis of the strontium titanate particles is 0. Compared to a case where the image forming apparatus is less than 025 or exceeds 0.25, there is provided an electrostatic image developing toner capable of suppressing fogging occurring in an image immediately after the start-up of the image forming apparatus.

  According to the invention of claim 12 or 13, the fog generated in the image immediately after the start-up of the image forming apparatus is 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%. An electrostatic charge image developing toner capable of being suppressed is provided.

  According to the invention according to claim 14 or 15, the fog generated in the image immediately after the start-up of the image forming apparatus is suppressed as compared with the case where the strontium titanate particles are not doped with metal elements other than titanium and strontium. An electrostatic charge image developing toner is provided.

  According to the invention of claim 21, 22, 23, 24, or 25, the strontium titanate particles present on the surface of the toner particles have an average primary particle size of 30 nm to 100 nm, and the average circularity of the primary particles Is 0.82 or more and 0.94 or less, but the circularity that is 84% of primary particles is 0.92 or less, or the average circularity of primary particles is 0.82 or more and 0.94 or less. Yes, compared to the case where an electrostatic charge image developing toner having an average primary particle size of less than 30 nm is applied, while the circularity at which the cumulative primary particle size is 84% exceeds 0.92, immediately after the image forming apparatus is started up. There are provided an electrostatic charge image developer, a toner cartridge, a process cartridge, an image forming apparatus, or an image forming method capable of suppressing fogging in the image.

It is the SEM image of the toner which externally added SW-360 by the titanium industry company which is an example of the strontium titanate particle, and the circularity distribution graph of the strontium titanate particle calculated | required by analyzing this SEM image. FIG. 5 is an SEM image of a toner externally added with another strontium titanate particle and a circularity distribution graph of the strontium titanate particle obtained by analyzing the SEM image. 1 is a schematic configuration diagram illustrating an image forming apparatus according to an exemplary embodiment. It is a schematic block diagram which shows the process cartridge which concerns on this embodiment.

  Embodiments of the invention will be described below. These descriptions and examples illustrate embodiments and do not limit the scope of the invention.

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

  In the present disclosure, numerical ranges indicated using “to” indicate ranges including numerical values described before and after “to” as the minimum value and the maximum value, respectively.

  In the present disclosure, “electrostatic image developing toner” is also simply referred to as “toner”, and “electrostatic image developer” is also simply referred to as “developer”.

<Toner for electrostatic 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 present embodiment includes toner particles and strontium titanate particles that are external additives.
In the toner according to the exemplary embodiment, the average primary particle size of the strontium titanate particles present on the surface of the toner particles is 30 nm to 100 nm, and the average circularity of the primary particles is 0.82 to 0.94. And the circularity, which is 84% of the accumulation of primary particles, is more than 0.92.
Hereinafter, the average primary particle size 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 that is 84% of the accumulation of primary particles is more than 0.92. The strontium titanate particles present on the surface of the toner particles are referred to as “specific strontium titanate particles”.

Strontium titanate particles have a charging behavior close to that of titanium oxide due to their elemental composition. In particular, since the strontium element has an effect of suppressing charging under low humidity, the strontium titanate particles containing the strontium element can be said to be a material with less difference due to the humidity environment as compared with titanium oxide.
On the other hand, since strontium titanate particles have a perovskite crystal structure and are cubic or rectangular parallelepiped, they have poor dispersibility in toner particles when externally added to toner particles. Further, since strontium titanate particles that are cubic or rectangular parallelepiped are present on the surface of the toner particles in a state where the corners pierce, when the charge is concentrated on the corners of the exposed strontium titanate particles during friction charging. As a result, the toner charge rises worse. In particular, when a low-density image is output under low temperature and low humidity (for example, 10 ° C. and 15% RH), the rising of charging of the toner tends to deteriorate. As a result, fog occurred in the image immediately after the start-up of the image forming apparatus.
On the other hand, even if the shape of the cube or the rectangular parallelepiped is broken, if the particle diameter is small, fogging occurs because the particles are easily embedded in the toner particles.

As a result of intensive studies, the present inventors have found that the strontium titanate particles present on the surface of the toner particles have an average primary particle size, an average circularity of the primary particles, and a circularity of 3 which is 84% of the cumulative primary particles. It has been found that the occurrence of fog is suppressed by paying attention to the shape characteristics and controlling them.
According to the above three shape characteristics, it is shown that the strontium titanate particles are present on the surface of the toner particles in a state of excellent dispersibility, and are present in a state of few corners. Because it can.
From the 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 where the corner portions are less exposed and have excellent dispersibility. It is considered that fogging that occurs in an image immediately after startup can be suppressed.

[Specific strontium titanate particles]
-Average primary particle size The average primary particle size of the specific strontium titanate particles is 30 nm to 100 nm, preferably 30 nm to 80 nm, and preferably 30 nm to 60 nm.
When the average primary particle size of the specific strontium titanate particles is 30 nm or more, the embedding of the specific strontium titanate particles in the toner particles is suppressed, and fog generated in an image immediately after the start-up of the image forming apparatus is easily suppressed. . In addition, since the average primary particle size of the specific strontium titanate particles is 100 nm or less, it is easy to increase the surface coverage with respect to the toner particles, and it is easy to suppress fogging that occurs in the image immediately after the start-up of the image forming apparatus.

  When the average primary particle size of the specific strontium titanate particles is in the above range, it can be said that the strontium titanate particles used as an external additive are also small in diameter. For this reason, the average primary particle size being in the above range means that small-diameter strontium titanate particles are present on the surface of the toner particles in an excellent dispersibility state.

The primary particle size of specific strontium titanate particles is the diameter of a circle having the same area as the primary particle image (so-called equivalent circle diameter). The average primary particle size of specific strontium titanate particles is the number of primary particle sizes. In the standard distribution, the particle size is 50% cumulative from the small diameter side.
The primary particle size of the specific strontium titanate particles is obtained by taking an SEM image of a toner to which strontium titanate particles are externally added and analyzing the image of at least 300 strontium titanate particles on the toner particles in the SEM image. A specific measurement method is described in [Example] described later.
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 an excellent dispersibility state.

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

The specific strontium titanate particles have an average primary particle circularity of 0.82 or more and 0.94 or less, and a circularity of 84% cumulative primary particles is more than 0.92.
Hereinafter, regarding the strontium titanate particles, the average circularity of primary particles may be referred to as “average circularity”, and the circularity that is 84% of primary particles may be referred to as “cumulative 84% circularity”.
When the average circularity and the cumulative 84% circularity are in 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 will be described later). For this reason, it is considered that fogging is suppressed in an image immediately after the start-up of the image forming apparatus, which is caused by the concentration of charges at the corners of the strontium titanate particles.

  The average circularity and cumulative 84% circularity of the specific strontium titanate particles are in the above range, which means that the strontium titanate particles used as an external additive also have a rounded shape. Therefore, strontium titanate particles with rounded corners are present on the surface of the toner particles in a highly dispersible state as compared to the case of using cubic or cuboid strontium titanate particles as an external additive. It can be said that.

In the present embodiment, the circularity of primary particles of strontium titanate particles is 4π × (area of primary particle image) ÷ (peripheral length of primary particle image) ² , and the average circularity of primary particles is circular The degree of circularity is 50% cumulative from the smaller side in the degree distribution, and the degree of circularity of 84% cumulative primary particles is the degree of circularity of 84% cumulative from the smaller side in the circularity distribution.
The circularity of the specific strontium titanate particles is determined by taking an SEM image of a toner to which strontium titanate particles are externally added and analyzing the image of at least 300 strontium titanate particles on the toner particles in the SEM image. A specific measurement method is described in [Example] described later.

  The cumulative 84% circularity in specific strontium titanate particles is one of the indicators of a rounded shape. The cumulative 84% circularity will be described.

FIG. 1A is a graph of a SEM image of a toner externally added with SW-360 manufactured by Titanium Industry, an example of strontium titanate particles, and a circularity distribution of strontium titanate particles obtained by analyzing the SEM image. . As shown in the SEM image, SW-360 had a cubic main particle shape, and was mixed with cuboid particles and spherical particles having a relatively small particle size. The circularity distribution of SW-360 in this example is concentrated between 0.84 and 0.92, the average circularity is 0.888, and the cumulative 84% circularity is 0.916. This is because the main particle shape of SW-360 is a cube, and the projected image of the cube is a regular hexagon (circularity of about 0.907), a flat hexagon, and a square (circularity of about 0.00). 785), the presence of a rectangle, and the fact that cubic strontium titanate particles are attached to toner particles at an angle and the projected image is mainly hexagonal.
From the fact that the actual circularity distribution of SW-360 is as described above and the theoretical circularity of the three-dimensional projection image, the cubic or cuboid strontium titanate particles have a cumulative primary particle 84% circularity. It can be estimated that it is below 0.92.
On the other hand, FIG. 1B shows two SEM images of toner externally added with other strontium titanate particles (two different magnifications, and the lower SEM image in FIG. 1B is a higher magnification SEM image. And a circularity distribution graph of the strontium titanate particles obtained by analyzing the SEM image. As shown by the two SEM images (particularly the lower SEM image of FIG. 1B), the strontium titanate particles of this example were rounded. 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, regarding the specific strontium titanate particles, the cumulative 84% circularity becomes one of the indicators of the rounded shape, and it can be said that it is a rounded shape when it exceeds 0.92.

  The average circularity of the specific strontium titanate particles is 0.82 or more and 0.94 or less, and 0.84 or more and 0.94 or less from the viewpoint of suppressing the fog generated in the image immediately after starting up the image forming apparatus. 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.
Further, the average circularity and cumulative 84% circularity of strontium titanate particles used as an external additive are, for example, various conditions when producing strontium titanate particles by a wet process, and doped metals of metal elements other than titanium and strontium It can be controlled by the element and its doping amount.

Standard deviation In this embodiment, the strontium titanate particles present on the surface of the toner particles preferably have a standard deviation of the circularity of the primary particles of 0.04 or more and 2.0 or less. 0 or less is preferable, and 0.04 to 0.50 is more preferable.
Cubic or cuboid strontium titanate particles tend to have a narrow circularity distribution due to their shape. Therefore, the strontium titanate particles having a standard deviation of the circularity of the primary particles within the above range is an index indicating that the strontium titanate particles contain many cubes or cuboids.
Therefore, strontium titanate particles whose standard deviation of the circularity of the primary particles is in the above range are present in the state where the corners are few on the surface of the toner particles, and electric charges are concentrated on the corners of the strontium titanate particles. As a result, fog is easily suppressed in an image immediately after the image forming apparatus is started up.

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

-Surface coverage In this 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, and 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 expressed, and fog is easily suppressed in the image immediately after the start-up of the image forming apparatus. When the surface coverage of the strontium titanate particles with respect to the toner particles is 50% or less, leakage of the toner charge becomes remarkable under high temperature and high humidity, and a sufficient charge amount of the toner cannot be secured and fogging occurs. Can be suppressed.

  As the surface coverage of the strontium titanate particles with respect to the toner particles, the SEM image used for the measurement of the average circularity and the cumulative 84% circularity described above was used. For this SEM image, image processing analysis software WinROOF (manufactured by Mitani Corporation) ) Area analysis tool.

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

Moreover, in order to satisfy the average circularity and cumulative 84% circularity of the specific strontium titanate particles described above, it is preferable to use rounded strontium titanate particles as the strontium titanate particles used as the external additive.
For example, the strontium titanate particles used as the external additive preferably have an average circularity of 0.82 to 0.94, more preferably 0.84 to 0.94, and 0.86 to 0.92. The following is more preferable.
When the average circularity is 0.82 or more, the dispersibility to the toner particles is easily improved, and when it is 0.94 or less, the mobility on the surface of the toner particles is lowered and the uniform dispersibility of the surface is easily improved.

The strontium titanate particles used as the external additive preferably have a (110) plane peak half-value width of 0.2 ° or more and 2.0 ° or less obtained by the X-ray diffraction method.
The peak of the (110) plane obtained by the X-ray diffraction method of strontium titanate particles is a peak that appears in the vicinity of the diffraction angle 2θ = 32 °. This peak corresponds to the peak of the (110) plane of the perovskite crystal.
Strontium titanate particles having a cubic or cuboid particle shape have high crystallinity of perovskite crystals, and the (110) plane peak half-value width is usually less than 0.2 °. For example, when SW-350 (strontium titanate particles whose main particle shape is cubic) manufactured by Titanium Industry Co., Ltd. was analyzed, the half width of the peak on the (110) plane was 0.15 °.
On the other hand, rounded strontium titanate particles have relatively low crystallinity of the perovskite crystal, and the full width at half maximum of the (110) plane peak is increased.
The strontium titanate particles used as the external additive preferably have a rounded shape. As one of the rounded shape indexes, the half-value width of the peak on the (110) plane is 0.2 ° or more 2 0.0 ° 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 more preferable.

  X-ray diffraction of strontium titanate particles is performed using an X-ray diffractometer (for example, RINT Ultimate-III, manufactured by Rigaku Corporation). Measurement settings are: source CuKα, voltage 40 kV, current 40 mA, sample rotation speed: no rotation, divergence slit: 1.00 mm, divergence longitudinal limit slit: 10 mm, scattering slit: open, light receiving slit: open, scanning mode: FT Counting time: 2.0 seconds, step width: 0.0050 °, operation axis: 10.0000 ° to 70.0000 °. In the present disclosure, the half width of the peak in the X-ray diffraction pattern is the full width at half maximum.

  The strontium titanate particles used as the external additive are preferably doped with a metal element other than titanium and strontium (hereinafter also referred to as a dopant). By containing a dopant, the strontium titanate particles have a rounded shape due to a decrease in crystallinity of the perovskite structure.

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

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

As a 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 preventing the strontium titanate particles from being excessively negatively charged. . The electronegativity in this embodiment is that of all red locomotive.
A suitable metal element having an electronegativity of 2.0 or less is shown below together with the electronegativity. Examples of metal elements having an electronegativity of 2.0 or less include lanthanum (1.08), magnesium (1.23), aluminum (1.47), silica (1.74), calcium (1.04), and 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 a range in which the dopant is 0.1 mol% or more and 20 mol% or less with respect to strontium from the viewpoint of a round shape while having a perovskite crystal structure. Is preferable, the range of 0.1 mol% to 15 mol% is more preferable, and the range of 0.1 mol% to 10 mol% is more preferable.

The strontium titanate particles used as an external additive preferably have a moisture 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 becomes an appropriate range, and the generation of fog is further suppressed.
The water content of the strontium titanate particles can be achieved within the above range by producing strontium titanate particles by a wet process and adjusting the conditions (temperature and time) of the drying treatment.
Further, when the surface of the strontium titanate particles is subjected to a hydrophobic treatment, the above range may be realized by adjusting the conditions of the drying treatment after the hydrophobic treatment.

The water content of the strontium titanate particles is measured as follows.
20 mg of a measurement sample was allowed to stand in a chamber at a temperature of 22 ° C./55% relative humidity for 17 hours to adjust the humidity, and then a thermobalance (TGA-50 manufactured by Shimadzu Corporation) in a room at a temperature of 22 ° C./55% relative humidity. Is heated from 30 ° C. to 250 ° C. at a temperature increase rate of 30 ° C./min in a nitrogen gas atmosphere, and the loss on heating (mass lost by heating) is measured.
And based on the measured heating loss, a moisture content is computed with the following formula | equation.
Moisture content (mass%) = (heat loss from 30 ° C. to 250 ° C.) ÷ (mass after humidity control and before heating) × 100

The strontium titanate particles used as an external additive are preferably strontium titanate particles having a hydrophobized surface from the viewpoint of improving the action of the strontium titanate particles, and are hydrophobized with a silicon-containing organic compound. More preferably, the particles are strontium titanate particles having a modified surface.
Examples of the silicon-containing organic compound include alkoxysilane compounds, silazane compounds, and silicone oils. Among these, at least one selected from the group consisting of alkoxysilane compounds and silicone oils is preferable.
The silicon-containing organic compound will be described in detail in the column of 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) with respect to the mass of the strontium titanate particles. It is preferable to have a surface containing a silicon-containing organic compound of not more than mass%, more preferably not less than 10 mass% and not more than 25 mass%.
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 with respect to the mass of strontium titanate particles. More preferably, it is more preferably 10% by mass or more and 25% by mass or less.
When the amount of hydrophobic treatment is 1% by mass or more, the charge amount of the toner can be secured even under high temperature and high humidity, and the occurrence of fog is easily suppressed. Further, when the hydrophobic 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, and the occurrence of fog is easily suppressed. Moreover, when the hydrophobization 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 surface of the strontium titanate particles is composed of silicon (Si) and strontium (Sr) 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, and 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, using a fluorescent X-ray analyzer (XRF1500, manufactured by Shimadzu Corporation), qualitative and quantitative analysis measurements are performed under conditions of an X-ray output of 40 V, 70 mA, a measurement area of 10 mmφ, and a measurement time of 15 minutes. Here, the elements to be analyzed are oxygen (O), silicon (Si), titanium (Ti), strontium (Sr), and metal elements (Me) other than titanium and strontium, and from the total of the measured elements. Then, the mass ratio (%) of each element is calculated with reference to calibration curve data or the like that can quantify each element created separately.
The mass ratio (Si / Sr) is calculated based on the silicon (Si) mass ratio value and the strontium (Sr) mass ratio value 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 the common logarithmic value logR1 from the viewpoint of improving the chargeability of the toner and further suppressing the generation of fog. Or less, more preferably 11 or more and 13 or less, and still more preferably 12 or more and 13 or less.

The volume resistivity R1 of strontium titanate particles is measured as follows.
On the lower electrode plate of the measuring jig, which is a pair of 20 cm ² circular electrode plates (made of steel) connected to an electrometer (KEYTHLEY, KEITHLEY 610C) and a high-voltage power supply (FLUKE, FLUKE 415B) Strontium particles are introduced so as to form a flat layer having a thickness in the range of 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 is placed on the strontium titanate particle layer which has been conditioned, and 4 kg of the upper electrode plate is removed to remove voids in the strontium titanate particle layer. A weight is placed, and the thickness of the strontium titanate particle layer is measured in that state. Next, a voltage of 1000 V is applied to the bipolar plates, the current value is measured, and the volume resistivity R1 is calculated from the following formula (1).
Formula (1): Volume resistivity R1 (Ω · cm) = V × S ÷ (A1−A0) ÷ d
In the formula (1), V is an applied voltage 1000 (V), S is an electrode plate area 20 (cm ² ), A1 is a measured current value (A), A0 is an initial current value (A) when the applied voltage is 0 V, d is the thickness (cm) of the strontium titanate particle layer.

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

  The volume specific resistivity R2 of the strontium titanate particles before the hydrophobization treatment is preferably 6 or more and 10 or less, more preferably 7 or more and 9 or less in the common logarithmic value logR2. In other words, the inside of the hydrophobized surface of the strontium titanate particles has the above resistance, and the strontium titanate particle has a low resistance inside, and the surface is a high resistance particle by the hydrophobizing treatment. Become. This improves the chargeability of the toner. In the present embodiment, the difference between the common logarithmic value logR1 of the volume specific resistivity R1 and the common logarithmic value logR2 of the volume specific resistivity R2 (logR1−logR2) is a viewpoint that improves the chargeability of the toner and ensures 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 volume resistivity R2 of the strontium titanate particles before the hydrophobized 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 volume specific resistivity R2 of the strontium titanate particles before being hydrophobized is measured by the same method as the volume specific resistivity R1.

-Method for producing strontium titanate particles-
The strontium titanate particles used as the external additive are produced by producing strontium titanate particles and then hydrophobizing the surface as necessary.
The method for producing strontium titanate particles is not particularly limited, but is preferably a wet production method from the viewpoint of controlling the particle size and shape.

-Manufacture of strontium titanate particles The wet manufacturing method of strontium titanate particles is a manufacturing method which makes it react, for example, adding an alkaline aqueous solution to the liquid mixture of a titanium oxide source and a strontium source, and then performs an acid treatment. In this production method, the particle diameter of the strontium titanate particles is controlled by the mixing ratio of the titanium oxide source and the strontium source, the titanium oxide source concentration at the initial stage of the reaction, the temperature when adding the alkaline aqueous solution, the addition rate, and the like.

  As the titanium oxide source, a mineral acid peptized product of a hydrolyzate of a titanium compound is preferable. Examples of the strontium source 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, and more preferably 1.05 or more and 1.20 or less in terms of 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, more preferably 0.5 mol / L or more and 1.0 mol / L or less as TiO ₂ .

  In order to adjust the resistance of the strontium titanate particles, it is preferable to add a dopant source to the mixed liquid of the titanium oxide source and the strontium source. Examples of the dopant source include oxides of metals other than titanium and strontium. The metal oxide as the dopant source is added, for example, as a solution dissolved in nitric acid, hydrochloric acid, sulfuric acid or the like. The addition amount of the dopant source is preferably an amount such that the metal as a dopant is 0.1 mol or more and 10 mol or less, and more preferably 0.5 mol or more and 10 mol or less with respect to 100 mol of strontium.

  The dopant source may be added when an aqueous alkali solution is added to the mixed liquid of the titanium oxide source and the strontium source. At that time, the metal oxide of the dopant source may be added as a solution dissolved in nitric acid, hydrochloric acid, or sulfuric acid.

As the alkaline aqueous solution, an aqueous sodium hydroxide solution is preferred. The higher the temperature at which the aqueous alkali solution is added, the more crystallinity strontium titanate particles tend to be obtained. In the present embodiment, the temperature is preferably 60 ° C. or higher and 100 ° C. or lower.
As the addition rate of the alkaline aqueous solution, the slower the addition rate, the larger the particle size of strontium titanate particles, and the faster the addition rate, the smaller the particle size of strontium titanate particles. The addition rate of the alkaline aqueous solution is, for example, 0.001 equivalent / h or more and 1.2 equivalent / h or less, and 0.002 equivalent / h or more and 1.1 equivalent / h or less is appropriate with respect to the charged raw material.

After adding the alkaline aqueous solution, acid treatment is performed for the purpose of removing the unreacted strontium source. In 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 solution is subjected to solid-liquid separation, and the solid content is dried to obtain strontium titanate particles.
The water content of the strontium titanate particles is controlled by adjusting the conditions for the solids drying treatment.
Moreover, when hydrophobizing the surface of strontium titanate particles, the water content may be controlled by adjusting the conditions of the drying process after the hydrophobizing process.
Here, the drying conditions for controlling the moisture content are preferably, for example, a drying temperature of 90 ° C. to 300 ° C. (preferably 100 ° C. to 150 ° C.), and a drying time of 1 hour to 15 hours (preferably 5 hours to 10 hours).

-Hydrophobization treatment Hydrophobization treatment on the surface of strontium titanate particles is prepared, for example, by preparing a treatment liquid obtained by mixing a silicon-containing organic compound as a hydrophobization treatment agent and a solvent, and stirring the strontium titanate particles. It is carried out by mixing 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 the silicon-containing organic compound that is a hydrophobizing agent include alkoxysilane compounds, silazane compounds, and silicone oils.

  Examples of the alkoxysilane compound that is a hydrophobizing agent 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, methyl vinyl dimethoxy silane, methyl vinyl diethoxy silane, diphenyl dimethoxy silane, diphenyl diethoxy silane; trimethylmethoxysilane, trimethylethoxysilane; and the like.

  Examples of the silazane compound that is a hydrophobizing agent include dimethyldisilazane, trimethyldisilazane, tetramethyldisilazane, pentamethyldisilazane, hexamethyldisilazane, and the like.

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

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

  The solvent used for the preparation of the treatment liquid is preferably an alcohol (for example, methanol, ethanol, propanol, butanol) when the silicon-containing organic compound is an alkoxysilane compound or a silazane compound, and the silicon-containing organic compound is silicone oil. In this case, hydrocarbons (for example, benzene, toluene, normal hexane, normal heptane) are preferable.

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

  As described above, the amount of the silicon-containing organic compound used for the hydrophobization 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, based on the mass of the strontium titanate particles. 5 mass% or more and 30 mass% or less are still more preferable, and 10 mass% or more and 25 mass% or less are especially preferable.

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

External addition amount The external addition 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. More preferred is 0.7 part by mass or more and 2 parts by mass or less.

[Particles other than strontium titanate particles]
The toner according to the exemplary embodiment may include particles other than the above-described strontium titanate as an external additive.
Other particles include other inorganic particles other than strontium titanate particles.
Other inorganic _{particles, SiO 2, TiO 2, Al} 2 O 3, CuO, ZnO, SnO 2, CeO 2, Fe 2 O 3, MgO, BaO, CaO, K 2 O, Na 2 O, ZrO 2, CaO _{· SiO 2, K 2 O ·} (TiO 2) n, Al 2 O 3 · 2SiO 2, CaCO 3, MgCO 3, BaSO 4, MgSO 4 , and the like.

The surface of the inorganic particles as an external additive is preferably subjected to a hydrophobic treatment. The hydrophobic treatment is performed, for example, by immersing inorganic particles in a hydrophobic treatment 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.

  Examples of the other particles include resin particles (resin particles such as polystyrene, polymethyl methacrylate, and melamine resin), cleaning activators (for example, particles of a fluorine-based high molecular weight substance), 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% by mass or less, and preferably 3% by mass or more and 10% by mass. The content is more preferably 4% by mass or more and 8% by mass or less.

[Toner particles]
The toner particles include, for example, a binder resin and, if necessary, 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, white toner particles, transparent toner particles, and glitter toner particles. There is no limit.

-Binder resin-
Examples of the binder resin 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 (for example, acrylonitrile, Methacrylonitrile, etc.), vinyl ethers (eg, vinyl methyl ether, vinyl isobutyl ether, etc.), vinyl ketones (eg, vinyl methyl ketone, vinyl ethyl ketone, vinyl isopropenyl ketone, etc.), olefins (eg, ethylene, Propylene, a homopolymer of a monomer such as butadiene) and the like, or a vinyl-based resin composed of these monomers with two or more combinations copolymer.
As the binder resin, for example, epoxy resin, polyester resin, polyurethane resin, polyamide resin, cellulose resin, polyether resin, non-vinyl resin such as modified rosin, a mixture of these with the vinyl resin, or these Examples also include a graft polymer obtained by polymerizing a vinyl monomer in the coexistence.
These binder resins may be used individually by 1 type, and may use 2 or more types together.

  A polyester resin is suitable as the binder resin. As a polyester resin, the condensation polymer of polyhydric carboxylic acid and polyhydric alcohol is mentioned, for example.

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

Examples of the polyhydric alcohol include aliphatic diols (for example, ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, butanediol, hexanediol, neopentyl glycol, etc.), alicyclic diols (for example, cyclohexanediol, cyclohexanedimethanol, Hydrogenated bisphenol A, etc.) and aromatic diols (for example, ethylene oxide adducts of bisphenol A, propylene oxide adducts of bisphenol A, etc.). Among these, as the polyhydric alcohol, for example, aromatic diols and alicyclic diols are preferable, and aromatic diols are more preferable.
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 the trihydric or higher polyhydric alcohol include glycerin, trimethylolpropane, and pentaerythritol.
A polyhydric alcohol may be used individually by 1 type, and may use 2 or more types together.

The glass transition temperature (Tg) of the polyester resin is preferably 50 ° C. or higher and 80 ° C. or lower, and 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), and more specifically, it is described in “Supplement” described in the method for obtaining the glass transition temperature in JIS K7121-1987 “Method for measuring glass transition temperature”. It is determined by “outer glass transition start temperature”.

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

The 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 reaction system is decompressed as necessary, and the reaction is performed while removing water and alcohol generated during the condensation.
When the raw material monomer is not dissolved or compatible at the reaction temperature, a solvent having a high boiling point may be added as a solubilizer and dissolved. In this case, the polycondensation reaction is performed while distilling off the solubilizer. If there is a monomer with poor compatibility, it is preferable to condense the monomer with poor compatibility with the monomer and the acid or alcohol to be polycondensed in advance before polycondensing with the main component. .

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

-Colorant-
Examples of the colorant include carbon black, chrome yellow, hansa yellow, benzidine yellow, sren yellow, quinoline yellow, pigment yellow, permanent orange GTR, pyrazolone orange, vulcan orange, watch young red, permanent red, brilliant carmine 3B, and brilliant. Carmine 6B, Dupont Oil Red, Pyrazolone Red, Resol 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, Malachite green oxalate, titanium oxide, zinc oxide, calcium carbonate, basic lead carbonate, Pigments such as zinc fluoride-barium sulfate mixture, zinc sulfide, silicon dioxide, aluminum oxide; acridine, xanthene, azo, benzoquinone, azine, anthraquinone, thioindico, dioxazine, thiazine, azomethine, indico , Phthalocyanine, aniline black, polymethine, triphenylmethane, diphenylmethane, and thiazole dyes.

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

  A coloring agent may be used individually by 1 type, and may use 2 or more types together.

  As the colorant, a surface-treated colorant may be used as necessary, or it may be used in combination with a dispersant.

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

-Release agent-
Examples of mold release agents include hydrocarbon waxes; natural waxes such as carnauba wax, rice wax, and candelilla wax; synthetic or mineral / petroleum waxes such as montan wax; and ester waxes such as fatty acid esters and montanic acid esters. And so on. The release agent is not limited to this.

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

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

-Other additives-
Examples of other additives include known additives such as a magnetic material, a charge control agent, and inorganic powder. 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 (core particle) and a coating layer (shell layer) covering the core. May be. The toner particles having a core / shell structure include, for example, a binder resin, a core portion containing 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, and 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), and the electrolyte is measured using ISOTON-II (manufactured by Beckman Coulter).
In the measurement, 0.5 mg to 50 mg of a measurement sample is added to 2 ml of a 5% by mass aqueous solution of a surfactant (preferably sodium alkylbenzenesulfonate) 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 is suspended is subjected to a dispersion treatment for 1 minute by an ultrasonic disperser, and each particle having a particle diameter in the range of 2 μm to 60 μm using an aperture having an aperture diameter of 100 μm is measured with a Coulter Multisizer II. Measure the diameter. The number of particles to be sampled is 50,000.
With respect to the measured particle size, a cumulative distribution based on the volume is drawn from the small diameter side, and the particle size that becomes 50% cumulative is defined as the volume average particle size D50v.

In this embodiment, the average circularity of the toner particles is not particularly limited, but is preferably 0.91 or more and 0.98 or less, and preferably 0.94 or more from the viewpoint of improving the cleaning property of the toner 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 round shape described above can be dispersed without uneven distribution of the strontium titanate particles on the surface of the toner particles. This is the same even when the irregularly shaped toner particles as described above are used, and uneven distribution in fine concave portions does not occur, and the strontium titanate particles are dispersed in a nearly uniform state on the surface of the toner particles. it can.
That is, even when such irregularly shaped toner particles are used, the toner configuration according to the present embodiment can be obtained, and fogging that occurs in an image 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 toner configuration according to the present embodiment is obtained, and the fog generated in the image immediately after the start-up of the image forming apparatus is obtained. Can be suppressed.

  In this embodiment, the circularity of the toner particles is (peripheral length of a circle having the same area as the particle projection image) / (peripheral length of the particle projection image), and the average circularity of the toner particles is the circularity The circularity is 50% cumulative from the small side in the distribution. The average circularity of the toner particles is obtained by analyzing at least 3000 toner particles with a flow type particle image analyzer. A specific measurement method is described in [Example] described later.

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

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

  The toner particles may be produced by any of a dry production method (for example, a kneading pulverization method) and a wet production method (for example, an aggregation coalescence method, a suspension polymerization method, a dissolution suspension method, etc.). There is no restriction | limiting in particular in these manufacturing methods, A well-known manufacturing method is employ | adopted. Among these, it is preferable to obtain toner particles by an aggregation and 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), and a resin particle dispersion (after mixing other particle dispersions as necessary) In the dispersion), agglomerating the resin particles (other particles as required) to form aggregated particles (aggregated particle forming step), and heating the aggregated particle dispersion in which the aggregated particles are dispersed to aggregate The toner particles are manufactured through a step of fusing and coalescing the particles to form toner particles (fusing and coalescing 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 will be described. The colorant and the release agent are used as necessary. Of course, you may use other additives other than a coloring agent and a mold release agent.

-Preparation step of resin particle dispersion-
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 serving 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 exchange water, and alcohols. These may be used individually by 1 type and may use 2 or more types together.

Examples of the surfactant include anionic surfactants such as sulfate ester, sulfonate, phosphate, and soap; cationic surfactants such as amine salt type and quaternary ammonium salt type; polyethylene glycol And nonionic surfactants such as polyphenols, alkylphenol ethylene oxide adducts, and polyhydric alcohols. Among these, an anionic surfactant and a cationic surfactant are particularly mentioned. The nonionic surfactant may be used in combination with an anionic surfactant or a cationic surfactant.
Surfactant may be used individually by 1 type and may use 2 or more types together.

  Examples of the method for dispersing the resin particles in the dispersion medium in the resin particle dispersion include a general dispersion method such as a rotary shear homogenizer, a ball mill having media, a sand mill, and a dyno mill. Depending on the type of resin particles, the resin particles may be dispersed in the dispersion medium by a phase inversion emulsification method. The phase inversion emulsification method is a method in which a resin to be dispersed is dissolved in a hydrophobic organic solvent in which the resin is soluble, neutralized by adding a base to the organic continuous phase (O phase), and then an aqueous medium (W phase). ) Is applied to perform phase inversion from W / O to O / W, and the resin is dispersed in the form of particles in the aqueous medium.

The volume average particle size of the resin particles dispersed in the resin particle dispersion is preferably 0.01 μm or more and 1 μm or less, more preferably 0.08 μm or more and 0.8 μm or less, further 0.1 μm or more and 0.6 μm or less. preferable.
The volume average particle size of the resin particles is a volume with respect to a divided particle size range (channel) using a particle size distribution obtained by measurement with a laser diffraction particle size distribution measuring apparatus (for example, LA-700 manufactured by HORIBA, Ltd.). The cumulative distribution is subtracted from the small particle diameter side, and the particle diameter that is 50% cumulative with respect to all particles is measured as the volume average particle diameter D50v. The volume average particle size of the particles in the other dispersion is also measured in the same manner.

  5 mass% or more and 50 mass% or less are preferable, and, as for content of the resin particle contained in the resin particle dispersion liquid, 10 mass% or more and 40 mass% or less are more preferable.

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

-Aggregated particle formation process-
Next, the resin particle dispersion, the colorant particle dispersion, and the release agent particle dispersion are mixed. Then, in the mixed dispersion, resin particles, colorant particles, and release agent particles are hetero-aggregated to have resin particles, colorant particles, and release agent particles having a diameter close to the diameter of the target toner particles. Aggregated particles are formed.

Specifically, for example, a flocculant is added to the mixed dispersion, and the pH of the mixed dispersion is adjusted to acidic (for example, pH 2 to 5), and a dispersion stabilizer is added as necessary. To a temperature close to the glass transition temperature (specifically, for example, the glass transition temperature of the resin particles −30 ° C. or more and the glass transition temperature −10 ° C. or less), the particles dispersed in the mixed dispersion liquid are aggregated, Agglomerated particles are formed.
In the agglomerated particle forming step, for example, the agglomerating agent is added at room temperature (for example, 25 ° C.) while stirring the mixed dispersion with a rotary shearing homogenizer, and the pH of the mixed dispersion is adjusted to be acidic (for example, pH 2 to 5). In addition, heating may be performed after adding a dispersion stabilizer as necessary.

Examples of the flocculant 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-valent metal complex. When a metal complex is used as the aggregating agent, the amount of the surfactant used is reduced and the charging characteristics are improved.
If necessary, an additive that forms a complex or a similar bond with the metal ion of the flocculant may be used together with the flocculant. As this additive, a chelating agent is preferably used.

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 the chelating agent 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 addition amount of the chelating agent is preferably 0.01 parts by mass or more and 5.0 parts by mass or less, and more preferably 0.1 parts by mass or more and less than 3.0 parts by mass with respect to 100 parts by mass of the resin particles.

-Fusion / unification process-
Next, the agglomerated particle dispersion in which the agglomerated particles are dispersed is heated to, for example, a glass transition temperature or higher of the resin particles (for example, a temperature of 10 ° C. to 30 ° C. higher than the glass transition temperature of the resin particles). Fusing and coalescing to form toner particles.

Through the above steps, toner particles are obtained.
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 surface of the aggregated particles. The second agglomerated particles are agglomerated to form a second agglomerated particle, and the second agglomerated particle dispersion is heated to fuse and coalesce the second agglomerated particles. The toner particles may be manufactured through a step of forming toner particles having a shell structure.

  After completion of the coalescence / union process, the toner particles formed in the solution are subjected to a known washing process, solid-liquid separation process, and drying process to obtain dried toner particles. In the washing step, it is preferable to sufficiently perform substitution washing with ion exchange water from the viewpoint of chargeability. In the solid-liquid separation step, suction filtration, pressure filtration, or the like is preferably performed from the viewpoint of productivity. From the viewpoint of productivity, the drying step is preferably performed by freeze drying, air flow drying, fluidized drying, vibration fluidized drying, or the like.

  The toner according to the exemplary embodiment is manufactured, for example, by adding an external additive to the obtained dry toner particles and mixing them. Mixing may be performed by, for example, a V blender, a Henschel mixer, a Laedige mixer, or the like. Further, if necessary, coarse toner particles may be removed using a vibration sieving machine, a wind sieving machine, or the like.

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

  There is no restriction | limiting in particular as a carrier, A well-known carrier is mentioned. Examples of carriers include a coated carrier in which the surface of a core made of magnetic powder is coated with a resin; a magnetic powder-dispersed carrier in which magnetic powder is dispersed in a matrix resin; and a porous magnetic powder impregnated with resin. Resin impregnated type carriers; and the like. The magnetic powder-dispersed carrier and the resin-impregnated carrier may be carriers in which the constituent particles of the carrier are used as a core and the surface is coated with a resin.

  Examples of the magnetic powder include magnetic metals such as iron, nickel, and cobalt; magnetic oxides such as ferrite and magnetite.

  Examples of the coating resin and matrix resin include polyethylene, polypropylene, polystyrene, polyvinyl acetate, polyvinyl alcohol, polyvinyl butyral, polyvinyl chloride, polyvinyl ether, polyvinyl ketone, vinyl chloride-vinyl acetate copolymer, styrene-acrylic acid. Examples thereof include an ester copolymer, a straight silicone resin containing an organosiloxane bond or a modified product thereof, a fluororesin, a polyester, a polycarbonate, a phenol resin, and an epoxy resin. The coating resin and the matrix resin may contain additives such as conductive particles. Examples of the conductive particles include particles of metals such as gold, silver, and copper, carbon black, titanium oxide, zinc oxide, tin oxide, barium sulfate, aluminum borate, and potassium titanate.

  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 may be mentioned. The solvent is not particularly limited, and may be selected in consideration of the type of resin used, application suitability, and the like. Specific resin coating methods include a dipping method in which a core material is immersed in a coating layer forming solution; a spray method in which the coating layer forming solution is sprayed on 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 carrier core material and a coating layer forming solution are mixed in a kneader coater, and then the solvent is removed;

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

<Image forming apparatus and image forming method>
The 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, a charging unit that charges the surface of the image carrier, an electrostatic image forming unit that forms an electrostatic image on the surface of the charged image carrier, and an electrostatic charge. Development means for containing an image developer and developing the electrostatic image formed on the surface of the image carrier as a toner image with the electrostatic image developer, and the toner image formed on the surface of the image carrier as a recording medium Transfer means for transferring to the surface of the recording medium, and fixing means for fixing the toner image transferred to the surface of the recording medium. The electrostatic charge image developer according to this embodiment is applied as the electrostatic charge image developer.

  In the image forming apparatus according to this embodiment, a charging process for charging the surface of the image carrier, an electrostatic charge image forming process for forming an electrostatic image on the surface of the charged image carrier, and an electrostatic charge according to this 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 the recording medium; An image forming method (an image forming method according to the present embodiment) including a fixing step of fixing the toner image transferred onto the surface of the recording medium is performed.

The image forming apparatus according to the present embodiment is a direct transfer type apparatus that directly transfers a toner image formed on the surface of an image carrier to a recording medium; the toner image formed on the surface of the image carrier is transferred to an intermediate transfer member An intermediate transfer type apparatus that primarily transfers the toner image transferred to the surface of the intermediate transfer body and then secondary transfer the toner image to 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 provided with cleaning means; an apparatus provided with charge eliminating means for irradiating the surface of the image carrier with charge removing light after the toner image is transferred and before charging is applied.
In the case where the image forming apparatus according to this embodiment is an intermediate transfer type apparatus, for example, the transfer unit intermediately transfers an intermediate transfer body on which a toner image is transferred onto the surface and a toner image formed on the surface of the image holding body. 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 part including the developing unit may have a cartridge structure (process cartridge) that can be attached to and detached from the image forming apparatus. As the process cartridge, for example, a process cartridge including a developing unit containing the electrostatic charge image developer according to the present embodiment is preferably used.

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

FIG. 2 is a schematic configuration diagram illustrating the image forming apparatus according to the present embodiment.
The image forming apparatus shown in FIG. 2 is a first electrophotographic system that outputs an image of each color of yellow (Y), magenta (M), cyan (C), and black (K) 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 in parallel at a predetermined distance from each other in the horizontal direction. These units 10Y, 10M, 10C, and 10K may be process cartridges that can be attached to and detached from the image forming apparatus.

  Above each unit 10Y, 10M, 10C, 10K, an intermediate transfer belt (an example of an intermediate transfer member) 20 is extended through each unit. The intermediate transfer belt 20 is provided 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 travels in a direction from the first unit 10Y to the fourth unit 10K. Yes. 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 the support roll 24. 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.

  Each unit 10Y, 10M, 10C, 10K developing device (an example of developing means) 4Y, 4M, 4C, 4K has yellow, magenta, cyan, black in toner cartridges 8Y, 8M, 8C, 8K, respectively. Each toner is supplied.

  Since the first to fourth units 10Y, 10M, 10C, and 10K have the same configuration and operation, the first image forming the yellow image disposed upstream in the traveling direction of the intermediate transfer belt is formed here. One unit 10Y will be described as a representative.

  The first unit 10Y includes a photoreceptor 1Y that functions as an image holding member. Around the photoreceptor 1Y, 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 by a laser beam 3Y based on the color-separated image signal. Then, an exposure device (an example of an electrostatic image forming unit) 3 that forms an electrostatic image, and a developing device (an example of a developing unit) 4Y that develops the electrostatic image by supplying toner charged to the electrostatic image, developed A primary transfer roll (an example of a primary transfer unit) 5Y that transfers the toner image onto the intermediate transfer belt 20, and a photoconductor cleaning device (of the image carrier cleaning unit) that removes toner remaining on the surface of the photoconductor 1Y after the primary transfer. Example) 6Y are arranged in order.

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

Hereinafter, an operation of forming a yellow image in the first unit 10Y will be described.
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 laminating a photosensitive layer on a conductive base (for example, a volume resistivity of 1 × 10 ⁻⁶ Ωcm or less at 20 ° C.). This photosensitive layer usually has a high resistance (general resin resistance), but has a property of changing the specific resistance of the portion irradiated with the laser beam when irradiated with the laser beam. Therefore, the laser beam 3Y is irradiated from the exposure device 3 on the surface of the charged photoreceptor 1Y in accordance with yellow image data sent from a control unit (not shown). Thereby, an electrostatic charge image of a yellow image pattern is formed on the surface of the photoreceptor 1Y.

The electrostatic charge image is an image formed on the surface of the photoreceptor 1Y by charging, and the specific resistance of the irradiated portion of the photosensitive layer is lowered by the laser beam 3Y, and the charged charge on the surface of the photoreceptor 1Y flows. On the other hand, this is a so-called negative latent image formed by the charge remaining in the portion not irradiated with the laser beam 3Y.
The electrostatic charge 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 and visualized as a toner image by the developing device 4Y.

  In the developing device 4Y, for example, an electrostatic charge image developer containing at least yellow toner and a carrier is accommodated. The yellow toner is triboelectrically charged by being agitated inside the developing device 4Y, has a charge of the same polarity (negative polarity) as the charged electric charge on the photoreceptor 1Y, and has a developer roll (of the developer holder). Example) is held on. Then, as the surface of the photoreceptor 1Y passes through the developing device 4Y, the yellow toner is electrostatically attached to the latent image portion on the surface of the photoreceptor 1Y, and the latent image is developed with the yellow toner. The 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 transported to the primary transfer position, a primary transfer bias is applied to the primary transfer roll 5Y, and electrostatic force from the photoreceptor 1Y toward 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. The transfer bias applied at this time has a (+) polarity opposite to the polarity (−) of the toner, and is controlled to, for example, +10 μA by the control unit (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 bias applied to the primary transfer rolls 5M, 5C, and 5K after the second unit 10M is 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 to perform multiple transfer. Is done.

  The intermediate transfer belt 20 onto which the four color toner images have been transferred in multiple ways through the first to fourth units includes the intermediate transfer belt 20, a support roll 24 in contact with the inner surface of the intermediate transfer belt, and an image holding surface of the intermediate transfer belt 20. To a secondary transfer portion composed of a secondary transfer roll (an example of secondary transfer means) 26 arranged on the side. On the other hand, recording paper (an example of a recording medium) P is fed at a predetermined timing into a gap where the secondary transfer roll 26 and the intermediate transfer belt 20 are in contact with each other via a supply mechanism, and the secondary transfer bias is supplied to the support roll. 24. The transfer bias applied at this time is a (−) polarity that is the same polarity as the polarity (−) of the toner, and an electrostatic force from the intermediate transfer belt 20 toward the recording paper P acts on the toner image, and the transfer bias is applied to the intermediate transfer belt 20. The toner image is transferred onto the recording paper P. The secondary transfer bias at this time is determined according to the resistance detected by a resistance detecting means (not shown) for detecting the resistance of the secondary transfer portion, and is voltage-controlled.

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

  Examples of the recording paper P to which the toner image is transferred include plain paper used in electrophotographic copying machines, printers, and the like. As the recording medium, in addition to the recording paper P, an OHP sheet and the like are also included. 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. For example, coated paper in which the surface of plain paper is coated with resin, art paper for printing, etc. Preferably used.

<Process cartridge, toner cartridge>
The process cartridge according to the present embodiment accommodates the electrostatic image developer according to the present embodiment, and develops the electrostatic image formed on the surface of the image carrier as a toner image by the electrostatic image developer. And a process cartridge that can be attached to and detached from the image forming apparatus.

  The process cartridge according to this embodiment includes a developing unit and, if necessary, at least one selected from other units such as an image holding member, a charging unit, an electrostatic charge image forming unit, and a transfer unit. It may be a configuration.

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

FIG. 3 is a schematic configuration diagram illustrating an example of a process cartridge according to the present embodiment.
The process cartridge 200 shown in FIG. 3 is provided around the photosensitive member 107 and the photosensitive member 107 by, for example, a housing 117 provided with an attachment rail 116 and an opening 118 for exposure. A charging roller 108 (an example of a charging unit), a developing device 111 (an example of a developing unit), and a photoconductor cleaning device 113 (an example of a cleaning unit) are integrally combined and held to form a cartridge. Yes.
In FIG. 3, 109 is an exposure device (an example of an electrostatic charge image forming unit), 112 is a transfer device (an example of a transfer unit), 115 is a fixing device (an example of a fixing unit), and 300 is a recording paper (an example of a recording medium). Is shown.

Next, the toner cartridge according to this embodiment will be described.
The toner cartridge according to the present exemplary embodiment is a toner cartridge that accommodates the toner according to the present exemplary embodiment and is detachable from the image forming apparatus. The toner cartridge contains toner for replenishment to be supplied to the 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 attached and detached. The developing devices 4Y, 4M, 4C, and 4K are toner cartridges corresponding to the respective colors. And a toner supply pipe (not shown). When the amount of toner stored in the toner cartridge becomes low, this toner cartridge is replaced.

  Hereinafter, embodiments of the present invention will be described in detail by way of examples, but the embodiments of the present invention are not limited to these examples. In the following description, “part” is based on mass unless otherwise specified.

<Preparation of strontium titanate particles>
[Strontium titanate particles (1)]
0.7 mol of metatitanic acid, which is a desulfurized and peptized titanium source, was collected as TiO ₂ and placed in a reaction vessel. Next, 0.77 mol of an aqueous strontium chloride solution was added to the reaction vessel so that the SrO / TiO ₂ molar ratio was 1.1. Next, a solution in which lanthanum oxide was dissolved in nitric acid was added to the reaction vessel in such an amount that lanthanum was 5 moles with respect to 100 moles of strontium. The initial TiO ₂ concentration in the mixed solution of the three materials was adjusted to 0.75 mol / L.
Next, the mixed liquid was stirred, and the mixed liquid was heated to 90 ° C. While maintaining the liquid temperature at 90 ° C. with stirring, 153 mL of 10N aqueous sodium hydroxide solution was added over 3.8 hours. Was maintained at 90 ° C. for 1 hour. Next, the reaction solution was cooled to 40 ° C., hydrochloric acid was added until pH 5.5, and the mixture was stirred for 1 hour. The precipitate was then washed by repeating decantation and water dispersion. Hydrochloric acid was added to the slurry containing the washed 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 such an amount that 20 parts of i-butyltrimethoxysilane was added to 100 parts of the solid content. Stir for 1 hour.
Thereafter, solid-liquid separation was performed by filtration, and the solid content was dried in the atmosphere at 110 ° C. for 5 hours to obtain strontium titanate particles (1).

[Strontium titanate particles (2) to (14), (16)]
Use amount of metatitanic acid as TiO ₂ [mol], addition amount of strontium chloride aqueous solution (amount of SrO) [mol], SrO / TiO ₂ molar ratio, addition amount of lanthanum with respect to 100 mol of strontium [mol], 10N hydroxylation Addition amount of sodium aqueous solution [mL], addition time of 10N sodium hydroxide aqueous solution [hour], type of hydrophobic treatment agent and treatment amount [parts] for 100 parts of solid content, and strontium titanate particles after hydrophobization treatment Strontium titanate particles (2) to (14) in the same manner as the preparation of 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)]
Except for changing the alcohol solution of i-butyltrimethoxysilane to silicone oil (KF-96-100CS, manufactured by Shin-Etsu Chemical Co., Ltd.), strontium titanate particles ( 15) was produced.

<Production of toner particles>
[Toner particles (1)]
-Preparation of resin particle dispersion (1)-
・ Terephthalic acid: 30 mol part ・ Fumaric acid: 70 mol part ・ Bisphenol A ethylene oxide adduct: 5 mol part ・ Bisphenol A propylene oxide adduct: 95 mol part A stirrer, nitrogen introduction tube, temperature sensor and rectifying tower The above-mentioned material was charged into 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 material. While the generated water was distilled off, the temperature was raised to 230 ° C. over 30 minutes, and after the dehydration condensation reaction was continued at the temperature for 1 hour, the reaction product 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 are put into a container equipped with a temperature control means and a nitrogen replacement means to make a mixed solvent, and then 100 parts of a polyester resin is gradually added and dissolved therein. % Aqueous ammonia solution (corresponding to 3 times the molar ratio of the acid value of the resin) was added and stirred for 30 minutes. Next, the inside of the container was replaced with dry nitrogen, the temperature was kept 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 the dropping, the temperature was returned to room temperature (20 ° C. to 25 ° C.), and bubbling was performed with dry nitrogen while stirring for 48 hours to obtain a resin particle dispersion in which ethyl acetate and 2-butanol were reduced to 1000 ppm or less. Ion exchange water was added to the resin particle dispersion to adjust the solid content to 20% by mass to obtain a resin particle dispersion (1).

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

-Preparation of release agent particle dispersion (1)-
-Paraffin wax (Nippon Seiwa, HNP-9): 100 parts-Anionic surfactant (Daiichi Kogyo Seiyaku, Neogen RK): 1 part-Ion-exchanged water: 350 parts After heating and dispersing using a homogenizer (IKA, trade name Ultra Tarrax T50), the dispersion was dispersed using a Menton Gorin high-pressure homogenizer (Gorin), and the release agent particles having a volume average particle diameter of 200 nm were dispersed. A mold particle dispersion (1) (solid content 20% by mass) was obtained.

-Production 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 Part The above material was 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 a nitric acid aqueous solution having a polyaluminum chloride concentration of 10% by mass was added. Subsequently, the mixture was dispersed at a liquid temperature of 30 ° C. using a homogenizer (IKA, trade name Ultra Turrax T50), and then heated to 45 ° C. in a heating oil bath and held for 30 minutes. Thereafter, 100 parts of the resin particle dispersion (1) was added and held for 1 hour, and the pH was adjusted to 8.0 by adding a 0.1N aqueous sodium hydroxide solution, then heated to 84 ° C. and held for 2.5 hours. did. Subsequently, it was cooled to 20 ° C. at a rate of 20 ° C./min, filtered, thoroughly washed with ion exchange water, and dried to obtain toner particles (1).
The obtained toner particles (1) had a volume average particle size of 5.7 μm and an average circularity of 0.95.

[Toner particles (2)]
Add 100 parts of resin particle dispersion (1) and hold for 1 hour, add 0.1N sodium hydroxide aqueous solution to adjust pH to 8.0, then heat to 84 ° C. and hold for 2.0 hours Produced toner particles (2) in the same manner as in the preparation of toner particles (1).
The obtained toner particles (2) had a volume average particle size 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 components were mixed and stirred for 30 minutes using a homogenizer (IKA, trade name Ultra Tarrax T50), and then dispersed for 1 hour using a high-pressure impact disperser ultimateizer (HJP30006: manufactured by Sugino Machine Co., Ltd.). A white pigment particle dispersion liquid (W) (solid content ratio of 30% by mass) in which a white pigment having a volume average particle diameter of 210 nm was dispersed was obtained.

-Production of toner particles (3)-
-Ion exchange 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 The above material is put into a round stainless steel flask, 0.1N nitric acid is added to adjust the pH to 3.5, and then a nitric acid aqueous solution having a polyaluminum chloride concentration of 10% by mass. 13 parts were added. Subsequently, the mixture was dispersed at a liquid temperature of 30 ° C. using a homogenizer (IKA, trade name Ultra Turrax T50), then heated to 45 ° C. in a heating oil bath and held for 60 minutes. Thereafter, 100 parts of the resin particle dispersion (1) was added and held for 1 hour, and the pH was adjusted to 8.5 by adding a 0.1N sodium hydroxide aqueous solution, and then heated to 85 ° C. and held for 5 hours. Subsequently, it was cooled to 20 ° C. at a rate of 20 ° C./min, filtered, sufficiently washed with ion exchange water, and dried to obtain toner particles (3) as 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.

<Creation of carrier>
The carrier produced as follows was used.
Ferrite particles (volume average particle size: 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 part First, the above components excluding ferrite particles are stirred with a stirrer for 10 minutes to prepare a dispersed coating solution, and then the coating solution and ferrite particles are combined. After putting in a vacuum degassing type kneader and stirring at 60 ° C. for 30 minutes, the carrier was obtained by further depressurizing while heating and degassing and drying.

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

  Each obtained toner and carrier were put in a V blender at a ratio of toner: carrier = 8: 92 (mass ratio) and stirred for 20 minutes to obtain a developer.

[Production of Toner and Developer: Examples 2 to 11, 13 and Comparative Examples 1 to 4]
A toner and a developer were prepared 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.

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

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

<Various analyzes>
[Shape characteristics of strontium titanate particles]
The toner was imaged at a magnification of 40,000 times using a scanning electron microscope (SEM) (S-4800, manufactured by Hitachi High-Technologies Corporation) equipped with an EDX device (manufactured by Horiba, EMAX Evolution X-Max80mm ² ). . By EDX analysis, 300 or more primary particles of strontium titanate were identified from one field of view based on the presence of Ti and Sr. SEM was observed at an acceleration voltage of 15 kV, an emission current of 20 μA, and a WD of 15 mm, and EDX analysis was performed under the same conditions with a detection time of 60 minutes.
The identified strontium titanate particles are analyzed by image processing analysis software WinRoof (Mitani Corporation) to determine the equivalent circle diameter, area and perimeter of each primary particle image, and circularity = 4π × (area) ÷ (Ambient length) ² was determined. Then, the equivalent circle diameter that is 50% cumulative from the smaller diameter side in the distribution of equivalent circle diameters is the average primary particle diameter, the circularity that is cumulative 50% from the smaller side in the circularity distribution is the average circularity, and the circularity The circularity that is 84% cumulative from the smaller side in the distribution was defined as the cumulative 84% circularity. The standard deviation was also obtained from the circularity distribution.
The obtained values are summarized in Table 2.

[Surface coverage]
The surface coverage of the toner was measured under the measurement conditions described above.
The results are shown in Table 2.

[X-ray diffraction of strontium titanate particles]
Using each strontium titanate particle before being externally added to the toner particle as a sample, the 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 at a diffraction angle of 2θ = 32 °, and the half-value width of each peak is 0.00. It was in the range of 2 ° to 0.5 °.

[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 water content was measured by the measurement method described above.
The measurement results are shown in Table 1.

[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.
The measurement results are shown in Table 1.

[Average circularity of toner particles]
The toner particles before external addition are analyzed by a flow type particle image analyzer (manufactured by Sysmex Corporation, FPIA-3000), and circularity = (peripheral length of a circle having the same area as the particle projection image) ÷ (The perimeter of the projected particle image) was determined, and the circularity that accumulated 50% from the small side in the circularity distribution of 3000 toner particles was defined as the average circularity of the toner particles.

When an external additive is externally added to the toner particles, the above measurement is performed after removing an external additive having a relatively large particle size (for example, an 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, 40 mL of 0.2 mass% Triton X-100 aqueous solution (manufactured by Acros Organics) and 2 g of toner are placed 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 (Nippon Seiki Seisakusho, US-300AT). The application of ultrasonic waves is as follows: application time: continuous for 300 seconds, output: 75 W, amplitude: 180 μm, distance between the ultrasonic transducer and the bottom of the container: 10 mm. Next, the dispersion was centrifuged at 3000 rpm for 2 minutes at a cooling temperature of 0 ° C. using a small high-speed cooling centrifuge (manufactured by Sakuma Seisakusho, M201-IVD), the supernatant was removed, and the remaining slurry was filtered (advantech). , Qualitative filter paper No. 5C, 110 nm). The residue on the filter paper is washed twice with ion exchange water and dried to obtain a measurement sample.

<Evaluation>
The obtained developer of each example was accommodated in a developing device of a remodeling machine (a remodeling machine in which the density automatic control sensor in an environmental change was turned off) of an image forming apparatus “Apeos Port-IV C5575 (manufactured by Fuji Xerox Co., Ltd.)”.
Using this image forming apparatus remodeling machine, the power source of the image forming apparatus is used in a high temperature and high humidity environment (28 ° C./85% RH environment) and in a low temperature and low humidity environment (10 ° C./15% RH environment). Immediately after putting in, fog evaluation was performed when 30 images having an image density of 1% were continuously output on A4 paper. The evaluation results are shown in Table 2.
The evaluation criteria are as follows.
G1: No fog is observed on all 30 sheets.
G2: Slight fogging is observed on one sheet, but this is a practically acceptable range.
G3: Slight fogging is observed on a plurality of sheets, but this is a practically acceptable range.
G4: Obvious fogging is observed on a plurality of sheets, which is not suitable for practical use.
G5: Full fog is observed on all 30 sheets.

1Y, 1M, 1C, 1K photoconductor (an example of an image carrier)
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 Photoconductor 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 an 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 photoconductor (an example of an image carrier)
108 Charging roll (an example of charging means)
109 Exposure apparatus (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 photoconductor 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 (25)

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 to 100 nm, an average circularity of the primary particles of 0.82 to 0.94, and a cumulative primary particle of 84 A toner for developing electrostatic images having a circularity of% exceeding 0.92.   The electrostatic image developing toner according to claim 1, wherein the strontium titanate particles present on the surface of the toner particles have a standard deviation of the circularity of primary particles of 0.04 or more and 2.0 or less.   The electrostatic image developing toner according to claim 2, wherein the strontium titanate particles present on the surface of the toner particles have a standard deviation of the circularity of primary particles of 0.04 or more and 1.0 or less.   4. The electrostatic image developing toner according to claim 1, wherein a water content of the strontium titanate particles is 1.5% or more and 10% or less. 5.   The electrostatic image developing toner according to claim 4, wherein the water content of the strontium titanate particles is 2% or more and 5% or less.   The electrostatic image developing toner according to claim 1, wherein the strontium titanate particles have a surface subjected to a hydrophobic treatment.   The toner for developing an electrostatic charge image according to claim 6, wherein the strontium titanate particles have a surface subjected to a hydrophobic treatment with a silicon-containing organic compound.   The toner for developing an electrostatic charge image according to claim 7, wherein the strontium titanate particles have the surface containing a silicon-containing organic compound in an amount of 5% by mass to 30% by mass with respect to the mass of the strontium titanate particles.   The toner for developing an electrostatic charge image according to claim 8, wherein the strontium titanate particles have the surface containing 10% by mass or more and 25% by mass or less of a silicon-containing organic compound with respect to the mass of the strontium titanate particles.   The electrostatic image developing toner according to claim 7, wherein the silicon-containing organic compound is at least one selected from the group consisting of an alkoxysilane compound and a silicone oil.   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 11. The toner for developing an electrostatic charge image according to any one of Items 7 to 10.   12. The electrostatic image developing toner according to claim 1, wherein a surface coverage of the strontium titanate particles with respect to the toner particles is 3% or more and 50% or less.   The electrostatic charge image developing toner according to claim 12, 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 developing an electrostatic charge image according to any one of claims 1 to 13, wherein the strontium titanate particles are strontium titanate particles doped with metal elements other than titanium and strontium.   The electrostatic image developing toner according to claim 14, wherein the strontium titanate particles are strontium titanate particles doped with lanthanum.   16. The electrostatic image developing toner according to claim 1, 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 electrostatic image developing toner according to claim 16, wherein the strontium titanate particles present on the surface of the toner particles have an average primary particle size of 30 nm to 60 nm.   The toner for developing an electrostatic charge image according to claim 1, wherein the toner particles have an average circularity of 0.91 or more and 0.98 or less.   The electrostatic charge image developing toner according to claim 18, wherein the toner particles have an average circularity of 0.93 or more and 0.97 or less.   The electrostatic image developing toner according to claim 1, wherein the toner particles are white toner particles.   An electrostatic charge image developer comprising the electrostatic charge image developing toner according to any one of claims 1 to 20. An electrostatic charge image developing toner according to any one of claims 1 to 20, containing the toner,
A toner cartridge to be attached to and detached from the image forming apparatus. A developing means for accommodating the electrostatic charge image developer according to claim 21 and developing the electrostatic charge image formed on the surface of the image holding member as a toner image by the electrostatic charge image developer,
A process cartridge attached to and detached from the image forming apparatus. An image carrier,
Charging means for charging the surface of the image carrier;
An electrostatic charge image forming means for forming an electrostatic charge image on the surface of the charged image carrier;
A developing unit that contains the electrostatic charge image developer according to claim 21 and that develops the electrostatic charge image formed on the surface of the image carrier as a toner image with the electrostatic charge image developer,
Transfer means for transferring a toner image formed on the surface of the image carrier to the surface of a recording medium;
Fixing means for fixing the toner image transferred to the surface of the recording medium;
An image forming apparatus comprising: A charging step for 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 image formed on the surface of the image carrier as a toner image with the electrostatic image developer according to claim 21;
A transfer step of transferring a toner image formed on the surface of the image carrier to the surface of a recording medium;
A fixing step of fixing the toner image transferred to the surface of the recording medium;
An image forming method comprising: