JP2022043345A - Electrostatic image developing carrier, electrostatic image developer, process cartridge, image forming device, and image forming method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrostatic image developing carrier which suppresses occurrence of fogging after repeated formation of monochromatic images with high-concentration and high-density.

SOLUTION: An electrostatic image developing carrier is provided, comprising: resin-coated magnetic particles, each comprising a magnetic particle and a resin layer covering the magnetic particle; and strontium titanate particles externally attached to the resin-coated magnetic particles, the strontium titanate particles having a half-value width of a peak of the (110) plane, as obtained by the X-ray diffraction method, in a range of 0.2° to 2.0°, inclusive.

SELECTED DRAWING: None

COPYRIGHT: (C)2022,JPO&INPIT

Description

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

As a carrier for developing an electrostatic charge image, a resin-coated carrier having a resin layer on the surface of magnetic particles is known. As the resin-coated carrier, for example, the following is disclosed.

Patent Document 1 describes a magnetic material dispersion type carrier in which a core material in which magnetic fine particles are dispersed in a binder resin is coated with a resin containing a styrene-acrylic copolymer, and is a strontium ferrite. A magnetic material-dispersed carrier containing barium ferrite or lead ferrite is disclosed.

Patent Document 2 discloses a carrier having a carrier core material made of ferrite and a resin layer covering the carrier core material and containing strontium ferrite fine particles.

Patent Document 3 describes a carrier having magnetic core particles and a coating layer covering the core particles, wherein the coating layer contains a resin and a filler, and 50 parts by mass of the filler is added to 100 parts by mass of the resin. Carriers containing up to 500 parts by mass are disclosed.

Patent Document 4 describes a magnetic carrier having a coating layer obtained by coating the surface of a magnetic carrier core containing a magnetic material with at least a binder resin and an inorganic fine powder, wherein the inorganic fine powder is at least titanium acid. Magnetic carriers containing strontium are disclosed.

Japanese Unexamined Patent Publication No. 05-323675 Japanese Unexamined Patent Publication No. 2013-120281 Japanese Unexamined Patent Publication No. 2013-057817 Japanese Unexamined Patent Publication No. 2010-014854

The first object of the present disclosure is a carrier for developing an electrostatic charge image containing resin-coated magnetic particles and strontium titanate particles, which has a cumulative total of 84% in the average circularity distribution of the primary particles of the strontium titanate particles. It is an object of the present invention to provide a carrier for static charge image development that suppresses fog that occurs after repeated formation of high-density and high-density monochromatic images as compared with a carrier for developing static charge images having a degree of 0.92 or less. ..

The second object of the present disclosure is a carrier for developing an electrostatic charge image containing resin-coated magnetic particles and strontium titanate particles, and the peak of the (110) plane obtained by the X-ray diffractometry of the strontium titanate particles. To provide a carrier for static charge image development that suppresses fog that occurs after repeated formation of high-concentration and high-density single-color images as compared with a carrier for static charge image development having a half-value width of less than 0.2 °. Is.

Specific means for solving the above-mentioned problems include the following aspects.

[1]
Resin-coated magnetic particles having magnetic particles and a resin layer covering the magnetic particles, and
Strontium titanate particles having an average circularity of 0.82 or more and 0.94 or less and a cumulative 84% circularity of more than 0.92.
Carrier for static charge image development including.

[2]
Resin-coated magnetic particles having magnetic particles and a resin layer covering the magnetic particles, and
Strontium titanate particles having a half width of the peak of the (110) plane obtained by the X-ray diffraction method of 0.2 ° or more and 2.0 ° or less, and
Carrier for static charge image development including.

[3]
The carrier for developing an electrostatic charge image according to [1] or [2], wherein the strontium titanate particles are strontium titanate particles containing a dopant.

[4]
The carrier for developing an electrostatic charge image according to any one of [1] to [3], wherein the average primary particle size of the strontium titanate particles is 10 nm or more and 100 nm or less.

[5]
The carrier for developing an electrostatic charge image according to [4], wherein the average primary particle size of the strontium titanate particles is 15 nm or more and 60 nm or less.

[6]
The item according to any one of [1] to [5], wherein the content of the strontium titanate particles is 0.01% by mass or more and 0.5% by mass or less with respect to the mass of the resin-coated magnetic particles. Carrier for static charge image development.

[7]
The carrier for developing an electrostatic charge image according to [6], wherein the content of the strontium titanate particles is 0.02% by mass or more and 0.08% by mass or less with respect to the mass of the resin-coated magnetic particles.

[8]
The carrier for static charge image development according to any one of [1] to [7], wherein the exposure ratio of the magnetic particles on the surface of the resin-coated magnetic particles is 2% or more and 20% or less.

[9]
The carrier for developing an electrostatic charge image according to any one of [1] to [8], wherein the magnetic particles are ferrite particles.

[10]
The ferrite particles contain at least one selected from calcium oxide and strontium oxide, and the total content of calcium element and strontium element is 0.1% by mass or more and 2.0% by mass or less with respect to the entire ferrite particles. The carrier for developing an electrostatic charge image according to [9].

[11]
The static charge image development according to [9], wherein the ferrite particles contain calcium oxide and the content of calcium elements is 0.2% by mass or more and 2.0% by mass or less with respect to the entire ferrite particles. Career.

[12]
The static charge image development according to [9], wherein the ferrite particles contain a strontium oxide and the content of the strontium element is 0.1% by mass or more and 1.0% by mass or less with respect to the entire ferrite particles. Career.

[13]
A static charge image developer comprising a toner for static charge image development and a carrier for static charge image development according to any one of [1] to [12].

[14]
A developing means for accommodating the electrostatic charge image developer according to [13] and developing the electrostatic charge image formed on the surface of the image holder as a toner image by the electrostatic charge image developer is provided.
A process cartridge that is attached to and detached from the image forming device.

[15]
Image holder and
A charging means for charging the surface of the image holder, and
An electrostatic charge image forming means for forming an electrostatic charge image on the surface of the charged image holder, and
A developing means that accommodates the electrostatic charge image developer according to [13] and develops the electrostatic charge image formed on the surface of the image holder as a toner image by the electrostatic charge image developer.
A transfer means for transferring a toner image formed on the surface of the image holder to the surface of a recording medium,
A fixing means for fixing the toner image transferred to the surface of the recording medium, and
An image forming apparatus.

[16]
The charging process that charges the surface of the image holder,
A static charge image forming step of forming a static charge image on the surface of the charged image holder, and
A developing step of developing an electrostatic charge image formed on the surface of the image holder as a toner image by using the electrostatic charge image developer according to [13].
A transfer step of transferring a toner image formed on the surface of the image holder to the surface of a recording medium, and
A fixing step of fixing the toner image transferred to the surface of the recording medium, and
Image forming method having.

According to the invention according to [1], [8] or [9], the circularity of the primary particles of strontium titanate particles, which is 84% cumulative in the average circularity distribution, is 0.92 or less as compared with the case where the circularity is 0.92 or less. Provided is a carrier for static charge image development that suppresses fog that occurs after repeated formation of high-density and high-density monochromatic images.

According to the invention according to [2], [8] or [9], compared with the case where the half width of the peak of the (110) plane obtained by the X-ray diffraction method of the strontium titanate particles is less than 0.2 °. Further, there is provided a carrier for static charge image development that suppresses fog that occurs after repeated formation of high-density and high-density monochromatic images.

According to the invention according to [3], as compared with the case where the strontium titanate particles do not contain a dopant, a carrier for static charge image development that suppresses fog generated after repeated formation of high-density and high-density monochromatic images. Is provided.

According to the invention according to [4] or [5], after repeated high-concentration and high-density monochromatic image formation as compared with the case where the average primary particle size of the strontium titanate particles is less than 10 nm or more than 100 nm. A carrier for developing an electrostatic charge image that suppresses the generation of fog is provided.

According to the invention according to [6] or [7], the content of the strontium titanate particles is less than 0.01% by mass or more than 0.5% by mass with respect to the mass of the resin-coated magnetic particles. Provided is a carrier for static charge image development that suppresses fog that occurs after repeated formation of high-density and high-density monochromatic images.

According to the invention according to [10], the total content of the calcium element and the strontium element is higher and higher than that in the case where the total content is less than 0.1% by mass or more than 2.0% by mass with respect to the whole ferrite particles. A carrier for static charge image development that suppresses fog that occurs after repeated formation of dense monochromatic images is provided.

According to the invention according to [11], the content of calcium element is less than 0.2% by mass or more than 2.0% by mass with respect to the whole ferrite particles, and the concentration is higher and the density is higher than that of the monochromatic color. A carrier for static charge image development that suppresses fog that occurs after repeated image formation is provided.

According to the invention according to [12], the content of the strontium element is less than 0.1% by mass or more than 1.0% by mass with respect to the whole ferrite particles, and the concentration is higher and the density is higher than that of the monochromatic color. A carrier for static charge image development that suppresses fog that occurs after repeated image formation is provided.

According to the invention according to [13], first, the circularity that is cumulative 84% in the average circularity distribution of the primary particles of strontium titanate particles is 0.92 or less, as compared with the case where the circularity is 0.92 or less. It occurs after repeated high-concentration and high-density monochromatic image formation as compared with the case where the half width of the peak of the (110) plane obtained by the X-ray diffractometry of strontium titanate particles is less than 0.2 °. An electrostatic charge image developer that suppresses fog is provided.

According to the invention according to [14], first, the circularity that is cumulative 84% in the average circularity distribution of the primary particles of strontium titanate particles is 0.92 or less, as compared with the case where the circularity is 0.92 or less. It occurs after repeated high-concentration and high-density monochromatic image formation as compared with the case where the half width of the peak of the (110) plane obtained by the X-ray diffraction method of strontium titanate particles is less than 0.2 °. A process cartridge that suppresses fog is provided.

According to the invention according to [15] or [16], first, in the average circularity distribution of the primary particles of strontium titanate particles, the cumulative circularity of 84% is 0.92 or less as compared with the case where the circularity is 0.92 or less. Secondly, high-density and high-density monochromatic image formation is repeated as compared with the case where the half width of the peak of the (110) plane obtained by the X-ray diffraction method of the strontium titanate particles is less than 0.2 °. An image forming apparatus or an image forming method for suppressing fog that occurs afterwards is provided.

It is an SEM image of the resin particle externally attached SW-360 manufactured by Titan Kogyo Co., Ltd. which is an example of the strontium titanate particle, and the circularity distribution graph of the strontium titanate particle obtained by analyzing the SEM image. It is the SEM image of the resin particle externally attached with another strontium titanate particle, and the circularity distribution graph of the strontium titanate particle obtained by analyzing the SEM image. It is a schematic block diagram which shows an example of the image forming apparatus which concerns on this embodiment. It is a schematic block diagram which shows an example of the process cartridge attached to and detached from the image forming apparatus which concerns on this embodiment.

Hereinafter, embodiments of the invention will be described. These explanations and examples are illustrative of embodiments and do not limit the scope of the invention.

When referring to the amount of each component in the composition in the present disclosure, if a plurality of substances corresponding to each component are present in the composition, unless otherwise specified, the plurality of species present in the composition. It means the total amount of substances.

The numerical range indicated by using "-" in the present disclosure indicates a range including the numerical values before and after "-" as the minimum value and the maximum value, respectively.

In the present disclosure, the term "process" is included in this term not only as an independent process but also as long as the intended purpose of the process is achieved even if it cannot be clearly distinguished from other processes.

In the present disclosure, the "carrier for static charge image development" is also referred to as "carrier", the "toner for static charge image development" is also referred to as "toner", and the "static charge image developer" is also referred to as "developer".

<Carrier for static charge image development>
The carrier according to the first embodiment includes magnetic particles, resin-coated magnetic particles having a resin layer covering the magnetic particles, and strontium titanate particles.
In the carrier according to the first embodiment, the strontium titanate particles have an average circularity of 0.82 or more and 0.94 or less and a cumulative circularity of more than 0.92, which is 84%.
In the first embodiment, the circularity of the primary particles of the strontium titanate particles means that the shape of the strontium titanate particles is rounded (details will be described later).

The carrier according to the second embodiment includes magnetic particles, resin-coated magnetic particles having a resin layer covering the magnetic particles, and strontium titanate particles.
In the carrier according to the second embodiment, the strontium titanate particles have a half width of the peak of the (110) plane obtained by the X-ray diffraction method of 0.2 ° or more and 2.0 ° or less.
In the second embodiment, the fact that the peak of the (110) plane of the strontium titanate particle has the above half width means that the shape of the strontium titanate particle has a rounded shape (details will be described later). do.).

Hereinafter, matters common to the first embodiment and the second embodiment will be collectively referred to as the present embodiments.

The carrier according to the present embodiment suppresses fog that occurs after repeated high-concentration and high-density monochromatic image formation because the strontium titanate particles contained in the carrier have a rounded shape. The mechanism is not always clear, but it is speculated as follows.

After repeating the formation of a monochromatic image having a high print area ratio (for example, a monochromatic image having an image area of 20% or more with respect to the printing paper area), an image having the same color and a low density (for example, a thin line such as a character) is imaged. When formed, fog (a phenomenon in which toner adheres to a portion of an image holder without an electrostatic charge image and an unintended image appears on a recording medium) may occur. This is because when a single color image with a high print area ratio is repeatedly formed, a large amount of toner in the developer is consumed, so that the amount of toner replenished increases, and the toner is not sufficiently charged in the developer, resulting in low charge. By becoming.

By the way, conventionally, carriers containing strontium titanate particles are known. The crystal structure of strontium titanate particles is a perovskite structure, and the particle shape is usually a cube or a rectangular parallelepiped. In a carrier in which cubic or rectangular parallelepiped strontium titanate particles are added to the resin-coated magnetic particles, the strontium titanate particles adhere to the resin layer with their corners pierced, so it is presumed that they are highly uniform and difficult to disperse.
On the other hand, it is presumed that the strontium titanate particles having a rounded shape easily move on the surface of the resin-coated magnetic particles and are dispersed with high uniformity. It is presumed that the strontium titanate particles dispersed on the surface of the resin-coated magnetic particles have high uniformity, and the carrier surface is highly uniform, and the electrical characteristics of the strontium titanate particles charge the particles relatively high. According to this carrier, it is presumed that the low charge of the toner in the developing device is suppressed, and as a result, the fog is suppressed.

Hereinafter, the configuration of the carrier according to the present embodiment will be described in detail.

[Resin-coated magnetic particles]
The resin-coated magnetic particles have a magnetic particle and a resin layer that coats the magnetic particle.

[Magnetic particles]
The magnetic particles are not particularly limited, and known magnetic particles used as the core material of the carrier are applied. Specific examples of the magnetic particles include particles of a magnetic metal such as iron, nickel, and cobalt; particles of a magnetic oxide such as ferrite and magnetite; resin-impregnated magnetic particles obtained by impregnating a porous magnetic powder with a resin; in a resin. Examples thereof include magnetic powder-dispersed resin particles in which magnetic powder is dispersed and blended.

Ferrite particles are suitable as the magnetic particles in this embodiment.
In the present embodiment, the ferrite particles preferably contain at least one selected from calcium oxide and strontium oxide. Calcium oxide and strontium oxide are likely to be contained on the surface of ferrite particles, and when calcium element or strontium element is present on the surface of ferrite particles, the carrier surface is relatively high by suppressing charge leakage from the ferrite particles. It is presumed to be charged. According to this carrier, the low charge of the toner in the developer is suppressed, and as a result, the fog is further suppressed and the fine line reproducibility is improved (for example, the thin line thickening, crushing or blurring is suppressed. Ru). This effect is remarkable when a low-density image of the same color is formed after repeating high-density and high-density single-color image formation at a higher speed.

In the present embodiment, the ferrite particles contain at least one selected from calcium oxide and strontium oxide, and the total content of the calcium element and the strontium element is 0.1% by mass or more with respect to the total mass of the ferrite particles. It is preferably 0% by mass or less. When the total content of the calcium element and the strontium element is 0.1% by mass or more with respect to the entire ferrite particles, charge leakage from the ferrite particles is efficiently suppressed. When the total content of the calcium element and the strontium element is 2.0% by mass or less with respect to the entire ferrite particles, the crystal structure of the ferrite particles is arranged, and the resistance value and the magnetic susceptibility are in an appropriate range. As a result, fog is further suppressed, and fine line reproducibility is improved (for example, thin line thickening, crushing, or blurring is suppressed).
From the above viewpoint, the total content of the calcium element and the strontium element is preferably 0.1% by mass or more and 2.0% by mass or less, and 0.2% by mass or more and 1.5% by mass or less with respect to the entire ferrite particles. Is more preferable, and 0.5% by mass or more and 1.2% by mass or less is further preferable.

In the present embodiment, the ferrite particles contain calcium oxide, and the content of calcium element is preferably 0.2% by mass or more and 2.0% by mass or less with respect to the total mass of the ferrite particles. When the content of the calcium element is 0.2% by mass or more with respect to the entire ferrite particles, charge leakage from the ferrite particles is efficiently suppressed. When the content of the calcium element is 2.0% by mass or less with respect to the entire ferrite particles, the crystal structure of the ferrite particles is arranged, and the resistance value and the magnetic susceptibility are in appropriate ranges. As a result, fog is further suppressed, and fine line reproducibility is improved (for example, thin line thickening, crushing, or blurring is suppressed).
From the above viewpoint, the content of the calcium element is preferably 0.2% by mass or more and 2.0% by mass or less, more preferably 0.5% by mass or more and 1.5% by mass or less, based on the whole ferrite particles. More preferably, it is 0.5% by mass or more and 1.0% by mass or less.

In the present embodiment, the ferrite particles contain strontium oxide, and the content of the strontium element is preferably 0.1% by mass or more and 1.0% by mass or less with respect to the total mass of the ferrite particles. When the content of the strontium element is 0.1% by mass or more with respect to the entire ferrite particles, charge leakage from the ferrite particles is efficiently suppressed. When the content of the strontium element is 1.0% by mass or less with respect to the entire ferrite particles, the crystal structure of the ferrite particles is arranged, and the resistance value and the magnetic susceptibility are in appropriate ranges. As a result, fog is further suppressed, and fine line reproducibility is improved (for example, thin line thickening, crushing, or blurring is suppressed).
From the above viewpoint, the content of the strontium element is preferably 0.1% by mass or more and 1.0% by mass or less, and more preferably 0.4% by mass or more and 1.0% by mass or less with respect to the entire ferrite particles. More preferably, it is 0.5% by mass or more and 0.8% by mass or less.

The content of calcium element and strontium element contained in the ferrite particles is measured by fluorescent X-ray analysis. Fluorescent X-ray analysis of ferrite particles is performed by the following method.
Using a fluorescent X-ray analyzer (XRF1500, manufactured by Shimadzu Corporation), qualitative and quantitative analysis is performed under the conditions of X-ray output: 40V / 70mA, measurement area: diameter 10mm, and measurement time: 15 minutes. The elements to be analyzed are selected based on the elements detected by qualitative analysis. Mainly, iron (Fe), manganese (Mn), magnesium (Mg), calcium (Ca), strontium (Sr), oxygen (O), and carbon (C) are selected. The mass ratio (%) of each element is calculated with reference to the calibration curve data prepared separately.

The volume average particle size of the magnetic particles is, for example, 10 μm or more and 500 μm or less, preferably 20 μm or more and 180 μm or less, and more preferably 25 μm or more and 60 μm or less.

As for the magnetic force of the magnetic particles, the saturation magnetization in a magnetic field of 3000 oersted is, for example, 50 emu / g or more, preferably 60 emu / g or more. The saturation magnetization is measured using a vibration sample type magnetic measuring device VSMP10-15 (manufactured by Toei Kogyo Co., Ltd.). The measurement sample is packed in a cell having an inner diameter of 7 mm and a height of 5 mm and set in the device. The measurement is performed by applying an applied magnetic field and sweeping up to 3000 oersted. Next, the applied magnetic field is reduced to create a hysteresis curve on the recording paper. Saturation magnetization, residual magnetization, and holding force are obtained from the curve data.

The volumetric electrical resistance (volume resistivity) of the magnetic particles is, for example, ¹⁰⁵ Ω · cm or more and ¹⁰⁹ Ω · cm or less, preferably ¹⁰⁷ Ω · cm or more and ¹⁰⁹ Ω · cm or less.
The volumetric electrical resistance (Ω · cm) of the magnetic particles is measured as follows. A layer is formed by placing the object to be measured flat on the surface of a circular jig on which a 20 cm ² electrode plate is arranged so as to have a thickness of 1 mm or more and 3 mm or less. The 20 cm ² electrode plate is placed on this and the layer is sandwiched. In order to eliminate the voids between the objects to be measured, a load of 4 kg is applied on the electrode plate arranged on the layer, and then the thickness (cm) of the layer is measured. Both electrodes above and below the layer are connected to an electrometer and a high voltage power generator. A high voltage is applied to both electrodes so that the electric field becomes 103.8 V / cm, and the current value (A) flowing at this time is read. The measurement environment is a temperature of 20 ° C. and a humidity of 50% RH. The formula for calculating the volumetric electrical resistance (Ω · cm) of the object to be measured is as shown in the following formula.
R = E × 20 / (I-I ₀ ) / L
In the above formula, R is the volumetric electrical resistance (Ω · cm) of the object to be measured, E is the applied voltage (V), I is the current value (A), I ₀ is the current value (A) at the applied voltage 0V, and L is. Represents the thickness (cm) of each layer. The coefficient 20 represents the area of the electrode plate (cm ² ).

[Resin layer covering magnetic particles]
Resins constituting the resin layer include styrene / acrylic acid copolymers; polyolefin resins such as polyethylene and polypropylene; polystyrene, acrylic resins, polyacrylonitrile, polyvinyl acetate, polyvinyl alcohol, polyvinyl butyral, polyvinyl chloride, polyvinyl carbazole, and the like. Polyvinyl-based or polyvinylidene-based resins such as polyvinyl ether and polyvinyl ketone; vinyl chloride / vinyl acetate copolymer; straight silicone resin composed of organosiloxane bonds or modified products thereof; polytetrafluoroethylene, polyvinyl fluoride, polyvinylidene fluoride, Fluororesin such as polychlorotrifluoroethylene; polyester; polyurethane; polycarbonate; amino resin such as urea / formaldehyde resin; epoxy resin; and the like can be mentioned.

The resin layer may contain inorganic particles for the purpose of controlling charge and resistance. Examples of the inorganic particles include carbon black; metals such as gold, silver, and copper; barium sulfate, aluminum borate, potassium titanate, titanium oxide, zinc oxide, tin oxide, antimony-doped tin oxide, and tin-doped. Examples thereof include metal compounds such as indium oxide and zinc oxide doped with aluminum; resin particles coated with metal; and the like.

Examples of the method for forming the resin layer on the surface of the magnetic particles include a wet manufacturing method and a dry manufacturing method. The wet manufacturing method is a manufacturing method using a solvent that dissolves or disperses the resin constituting the resin layer. On the other hand, the dry manufacturing method is a manufacturing method that does not use the above solvent.

As the wet manufacturing method, for example, a dipping method in which magnetic particles are dipped in a resin liquid for forming a resin layer to coat the resin; a spray method in which the resin liquid for forming a resin layer is sprayed on the surface of the magnetic particles; Examples thereof include a fluidized bed method in which a resin liquid for forming a resin layer is sprayed in a state of being converted; a kneader coater method in which magnetic particles and a resin liquid for forming a resin layer are mixed in a kneader coater and a solvent is removed.
The resin liquid for forming a resin layer used in the wet production method is prepared by dissolving or dispersing the resin and other components in a solvent. The solvent is not particularly limited as long as it dissolves or disperses the resin, and examples thereof include aromatic hydrocarbons such as toluene and xylene; ketones such as acetone and methyl ethyl ketone; and ethers such as tetrahydrofuran and dioxane. used.

Examples of the dry method include a method of heating a mixture of magnetic particles and a resin for forming a resin layer in a dry state to form a resin layer. Specifically, for example, magnetic particles and a resin for forming a resin layer are mixed in a gas phase and heated and melted to form a resin layer.

The thickness of the resin layer is preferably 0.1 μm or more and 10 μm or less, and more preferably 0.3 μm or more and 5 μm or less.

The exposure ratio of the magnetic particles on the surface of the resin-coated magnetic particles is preferably 2% or more and 20% or less, more preferably 2% or more and 10% or less, and further preferably 3% or more and 8% or less. preferable.

The exposure ratio of the magnetic particles on the surface of the resin-coated magnetic particles is determined by the following method by X-ray photoelectron spectroscopy (XPS).
Prepare the target resin-coated magnetic particles and the magnetic particles obtained by removing the resin layer from the target resin-coated magnetic particles. Examples of the method of removing the resin layer from the resin-coated magnetic particles include a method of dissolving the resin component with an organic solvent to remove the resin layer, a method of removing the resin component by heating at about 800 ° C., and the like to remove the resin layer. Can be mentioned. Using the resin-coated magnetic particles and the magnetic particles excluding the resin layer as measurement samples, Fe (atomic%) was quantified by XPS, and (Fe of the resin-coated magnetic particles) ÷ (Fe of the magnetic particles) × 100. Calculated and used as the exposure ratio (%) of magnetic particles.

The exposure ratio of the magnetic particles on the surface of the resin-coated magnetic particles can be controlled by the amount of the resin used to form the resin layer, and the larger the amount of the resin with respect to the amount of the magnetic particles, the smaller the exposure ratio.

[Characteristics of carrier]
The volume average particle size of the carrier is preferably 15 μm or more and 510 μm or less, more preferably 20 μm or more and 180 μm or less, and further preferably 25 μm or more and 60 μm or less.

As for the magnetic force of the carrier, the saturation magnetization in a magnetic field of 1000 oersted is, for example, 40 emu / g or more, and preferably 50 emu / g or more. The measurement of the saturation magnetization is performed in the same manner as the measurement of the saturation magnetization of the magnetic particles, provided that the maximum amount of oersted is 1000.

The volumetric electrical resistance (25 ° C.) of the carrier is, for example, 1 × 10 ⁷ Ω · cm or more and 1 × 10 ¹⁵ Ω · cm or less, preferably 1 × 10 ⁸ Ω · cm or more and 1 × 10 ¹⁴ Ω · cm or less. More preferably, it is 1 × 10 ⁸ Ω · cm or more and 1 × 10 ¹³ Ω · cm or less. The measurement of the volumetric electrical resistance of the carrier is performed in the same manner as the measurement of the volumetric electrical resistance of the magnetic particles.

[Strontium titanate particles]
In the present embodiment, the strontium titanate particles preferably have an average primary particle size of 10 nm or more and 100 nm or less. When the average primary particle size of the strontium titanate particles is 10 nm or more, the embedding of the resin-coated magnetic particles in the resin layer is suppressed, and the particles are easily dispersed on the surface of the resin-coated magnetic particles with high uniformity. When the average primary particle size of the strontium titanate particles is 100 nm or less, the release from the resin-coated magnetic particles is suppressed, and the carrier surface is charged relatively high due to the electrical characteristics of the strontium titanate particles.

From the above viewpoint, the average primary particle size of the strontium titanate particles is preferably 10 nm or more and 100 nm or less, more preferably 20 nm or more and 90 nm or less, further preferably 30 nm or more and 80 nm or less, and further preferably 30 nm or more and 60 nm or less.

In the present embodiment, the primary particle size of the strontium titanate particles is the diameter of a circle having the same area as the primary particle image (so-called circle equivalent diameter), and the average primary particle size of the strontium titanate particles is the primary particle size. The particle size is 50% cumulative from the small diameter side in the distribution based on the number of particles. The primary particle size of the strontium titanate particles is determined by image analysis of at least 300 strontium titanate particles.

The average primary particle size of the strontium titanate particles can be controlled, for example, by various conditions when the strontium titanate particles are produced by a wet method.

In the present embodiment, the shape of the strontium titanate particles is not a cube or a rectangular parallelepiped but a rounded shape from the viewpoint of suppressing the generation of fog.

In the present embodiment, the strontium titanate particles preferably have an average circularity of 0.82 or more and 0.94 or less, and a circularity of more than 0.92, which is 84% of the cumulative primary particles. ..
In the present embodiment, the circularity of the primary particles of the strontium titanate particles is 4π × (area of the primary particle image) ÷ (peripheral length of the primary particle image) ² , and the average circularity of the primary particles is circularity. The circularity having a cumulative total of 50% from the small side in the distribution of the circularity, and the circularity having a cumulative total of 84% of the primary particles is the circularity having a cumulative total of 84% from the small side in the distribution of the circularity. The circularity of the strontium titanate particles is determined by image analysis of at least 300 strontium titanate particles.

For strontium titanate particles, the circularity, which is the cumulative 84% of the primary particles, is one of the indicators of the rounded shape. The circularity (hereinafter, also referred to as cumulative 84% circularity) in which the cumulative number of primary particles is 84% will be described.

FIG. 1A is an SEM image of resin particles externally attached with SW-360 manufactured by Titan Kogyo Co., Ltd., which is an example of strontium titanate particles, and a graph of the circularity distribution of strontium titanate particles obtained by analyzing the SEM image. be. As shown in the SEM image, SW-360 had a cubic main particle shape, and was a mixture of rectangular parallelepiped particles and spherical particles having a relatively small particle size. The circularity distribution of SW-360 in this example was concentrated between 0.84 and 0.92, with an average circularity of 0.888 and a cumulative 84% circularity of 0.916. This is
(A) The main particle shape of SW-360 is a cube.
(B) The projected image of the cube has a regular hexagon (circularity about 0.907), a flat hexagon, a square (circularity about 0.785), and a rectangle in order of proximity to a circle.
(C) The cubic strontium titanate particles are attached to the resin particles at an angle, and the projected image is mainly hexagonal.
It is considered to be a reflection of.
Given that the actual circularity distribution of SW-360 is as described above and the theoretical circularity of the three-dimensional projected image, cubic or rectangular parallelepiped strontium titanate particles have a cumulative 84% circularity of the primary particles. It can be estimated to be less than 0.92.
On the other hand, FIG. 1B is a graph of an SEM image of resin particles externally supplemented with another strontium titanate particle and a circularity distribution of the strontium titanate particle obtained by analyzing the SEM image. As the SEM image shows, the strontium titanate particles of this example had a rounded shape. The strontium titanate particles of this example had an average circularity of 0.883 and a cumulative 84% circularity of 0.935.
From the above, regarding the strontium titanate particles, the cumulative 84% circularity of the primary particles is one of the indexes of the rounded shape, and it can be said that the rounded shape is more than 0.92.

In the present embodiment, the average circularity of the primary particles of the strontium titanate particles is preferably 0.82 or more and 0.94 or less, more preferably 0.84 or more and 0.94 or less, and 0. It is more preferably .86 or more and 0.92 or less.

In the present embodiment, the strontium titanate particles preferably have a standard deviation of the circularity of the primary particles of 0.04 or more and 2.0 or less, more preferably 0.04 or more and 1.0 or less, and 0. It is more preferably 04 or more and 0.50 or less.
Cubic or rectangular parallelepiped strontium titanate particles tend to have a narrower circularity distribution due to their shape. Therefore, the standard deviation of the circularity of the primary particles in the above range is an index indicating that the particles are not strontium titanate particles containing a large amount of cubes or rectangular parallelepipeds.

In the present embodiment, the strontium titanate particles preferably have a half width of the peak of the (110) plane obtained by the X-ray diffraction method of 0.2 ° or more and 2.0 ° or less, and 0.2 ° or more and 1. It is more preferably 0 ° or less.
The peak of the (110) plane obtained by the X-ray diffraction method of the strontium titanate particles is a peak appearing in the vicinity of the diffraction angle 2θ = 32 °. This peak corresponds to the peak on the (110) plane of the perovskite crystal.
Strontium titanate particles having a cubic or rectangular parallelepiped shape have high crystallinity of perovskite crystals, and the half width of the peak of the (110) plane is usually less than 0.2 °. For example, when SW-350 (strontium titanate particles whose main particle shape is a cube) manufactured by Titan Kogyo Co., Ltd. was analyzed, the half width of the peak of the (110) plane was 0.15 °.
On the other hand, in the strontium titanate particles having a rounded shape, the crystallinity of the perovskite crystals is relatively low, and the half width of the peak of the (110) plane is widened.
In the present embodiment, the strontium titanate particles preferably have a rounded shape, and as one of the indexes of the rounded shape, the half width of the peak of the (110) plane is 0.2 ° or more. 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 further preferable.

The X-ray diffraction of the strontium titanate particles is measured using an X-ray diffractometer (for example, manufactured by Rigaku Corporation, trade name: RINT Ultima-III). The measurement settings are source CuKα, voltage: 40 kV, current: 40 mA, sample rotation speed: no rotation, divergence slit: 1.00 mm, divergence vertical limiting slit: 10 mm, scattering slit: open, light receiving slit: open, scanning mode. : FT, counting time: 2.0 seconds, step width: 0.0050 °, operating axis: 10.000 ° 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.

In the present embodiment, the strontium titanate particles are preferably doped with a metal element other than titanium and strontium (hereinafter, also referred to as a dopant). The strontium titanate particles contain a dopant, so that the crystallinity of the perovskite structure is reduced and the particles have a rounded shape.

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 viewpoint, the dopant of the strontium titanate particles is preferably a metal element having an ionic radius of 40 pm or more and 200 pm or less, and more preferably 60 pm or more and 150 pm or less.

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

As the dopant of the strontium titanate particles, a metal element having an electronegativity of 2.0 or less is preferable, and a metal element having an electronegativity of 1.3 or less is more preferable from the viewpoint of not excessively negatively charging the strontium titanate particles. .. In this embodiment, the electronegativity is the electronegativity of all-red locomotive. Examples of metal elements having an electronegativity of 2.0 or less include lanthanum (electronegativity 1.08), magnesium (1.23), aluminum (1.47), silica (1.74), and calcium (1.04). ), Vanadium (1.45), chromium (1.56), manganese (1.60), iron (1.64), cobalt (1.70), nickel (1.75), copper (1.75). , Zinc (1.66), gallium (1.82), ittrium (1.11), zirconium (1.22), niobium (1.23), silver (1.42), indium (1.49), Examples thereof include tin (1.72), barium (0.97), tantalum (1.33), renium (1.46), cerium (1.06) and the like.

The amount of the dopant in the strontium titanate particles is preferably in the range of 0.1 mol% or more and 20 mol% or less of the dopant with respect to strontium from the viewpoint of having a perovskite-type crystal structure and a rounded shape. , 0.1 mol% or more and 15 mol% or less is more preferable, and 0.1 mol% or more and 10 mol% or less is further preferable.

In the present embodiment, the strontium titanate particles are preferably strontium titanate particles having a hydrophobically treated surface from the viewpoint of improving the action of the strontium titanate particles. It is presumed that the strontium titanate particles that have been hydrophobized repel each other on the resin-coated magnetic particles and are highly uniform and easy to disperse.

In the present embodiment, the strontium titanate particles are more preferably strontium titanate particles having a surface hydrophobized with a silicon-containing organic compound. Strontium titanate particles hydrophobized with a silicon-containing organic compound have a higher non-image area on the photoconductor than strontium titanate particles hydrophobized with a highly positively charged treatment agent such as a fatty acid metal salt. It is difficult to release and causes less image defects.

The strontium titanate particles are 1% by mass or more and 50% by mass or less (preferably 5% by mass or more and 40% by mass or less, more preferably 5% by mass or more and 30% by mass or less, still more preferably 10% by mass) with respect to the mass thereof. It is preferable to have a surface containing a silicon-containing organic compound (25% by mass or less).
That is, the amount of the hydrophobic treatment with 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 5% by mass or more with respect to the mass of the strontium titanate particles. It is more preferably 30% by mass or less, further preferably 10% by mass or more and 25% by mass or less.
When the amount of hydrophobizing treatment is within the above range, it is easy to suppress the occurrence of fog. When the hydrophobizing treatment amount is 30% by mass or less, the generation of aggregates caused by the hydrophobized surface is suppressed.

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

Fluorescent X-ray analysis of the hydrophobized surface of strontium titanate particles is performed by the following method.
Using a fluorescent X-ray analyzer (XRF1500, manufactured by Shimadzu Corporation), qualitative and quantitative analysis is performed under the conditions of X-ray output: 40V / 70mA, measurement area: diameter 10mm, and measurement time: 15 minutes. The elements to be analyzed are oxygen (O), silicon (Si), titanium (Ti), strontium (Sr), and other metal elements (Me). %) Is calculated. The mass ratio Si / Sr is calculated from the mass ratio (%) of silicon (Si) and the mass ratio (%) of strontium (Sr) obtained in this measurement.

In the present embodiment, the volume resistivity R (Ω · cm) of the strontium titanate particles is preferably 11 or more and 14 or less, more preferably 11 or more and 13 or less, still more preferably 12 or more and 13 or less in the common logarithmic value logR. ..

The volume resistivity R of the strontium titanate particles can be controlled, for example, by the type of dopant, the amount of dopant, the type of hydrophobizing agent, the amount of hydrophobizing treatment, the drying temperature and drying time after hydrophobizing treatment, and the like.

The volume resistivity R of the strontium titanate particles is measured as follows.
Titanium acid on the lower plate of a measuring jig, which is a pair of 20 cm ² circular plates (steel) connected to an electrometer (KEYTHLEY, KEYTHLEY 610C) and a high-voltage power supply (FLUKE, FLUKE415B). Strontium particles are placed so as to form a flat layer having a thickness of 1 mm or more and 2 mm or less. Next, the humidity is adjusted for 24 hours in an environment of a temperature of 22 ° C. and a relative humidity of 55%. Next, in an environment of a temperature of 22 ° C. and a relative humidity of 55%, an upper plate was placed on the strontium titanate particle layer, and a weight of 4 kg was placed on the upper plate to remove voids in the strontium titanate particle layer. And measure the thickness of the strontium titanate particle layer in that state. Next, a voltage of 1000 V is applied to both electrode plates to measure the current value, and the volume resistivity R is calculated from the following equation (1).
Equation (1): Volume resistivity R (Ω · cm) = V × S ÷ (A1-A0) ÷ d
In the formula (1), V is the applied voltage 1000 (V), S is the plate area 20 (cm ² ), A1 is the measured current value (A), and A0 is the initial current value (A) when the applied voltage is 0 V. d is the thickness (cm) of the strontium titanate particle layer.

In the present embodiment, the strontium titanate particles preferably have a water content of 1.5% by mass or more and 10% by mass or less. When the water content is 1.5% by mass or more and 10% by mass or less (more preferably 2% by mass or more and 5% by mass or less), the resistance of the strontium titanate particles is controlled within an appropriate range, and the strontium titanate particles have a water content of 1.5% by mass or more and 10% by mass or less. Excellent in suppressing uneven distribution due to electrostatic repulsion. The water content of the strontium titanate particles can be controlled, for example, by producing the strontium titanate particles by a wet method and adjusting the temperature and time of the drying treatment. When the strontium titanate particles are hydrophobized, the water content of the strontium titanate particles can be controlled by adjusting the temperature and time of the drying treatment after the hydrophobizing treatment.

The water content of the strontium titanate particles is measured as follows.
20 mg of the measurement sample was allowed to stand in a chamber with a temperature of 22 ° C. and a relative humidity of 55% for 17 hours to control the humidity, and then a heat balance (TGA-50 type manufactured by Shimadzu Corporation) in a room with a temperature of 22 ° C. and a relative humidity of 55%. Heat from 30 ° C. to 250 ° C. at a temperature rise rate of 30 ° C./min in a nitrogen gas atmosphere, and measure the heat loss (mass lost by heating). Based on the measured heat loss, the water content is calculated by the following formula.
Moisture content (% by mass) = (weight loss by heating from 30 ° C to 250 ° C) ÷ (mass after humidity control and before heating) x 100

The content of the strontium titanate particles contained in the carrier according to the present embodiment is preferably 0.01% by mass or more and 0.8% by mass or less, and 0.01% by mass or more and 0. 5% by mass or less is more preferable, 0.02% by mass or more and 0.08% by mass or less is further preferable, and 0.04% by mass or more and 0.05% by mass or less is further preferable.

[Manufacturing method of strontium titanate particles]
The strontium titanate particles may be the strontium titanate particles themselves, or may be particles in which the surface of the strontium titanate particles (sometimes referred to as mother particles) is hydrophobized. The method for producing strontium titanate particles (mother particles) is not particularly limited, but a wet production method is preferable from the viewpoint of controlling the particle size and shape.

The wet method for producing strontium titanate particles is, for example, a production method in which a mixture of a titanium oxide source and a strontium source is reacted while adding an alkaline aqueous solution, and then acid treatment is performed. In this production method, the particle size of the strontium titanate particles is controlled by the mixing ratio of the titanium oxide source and the strontium source, the concentration of the titanium oxide source at the initial stage of the reaction, the temperature at which the alkaline aqueous solution is added, the addition rate, and the like.

As the titanium oxide source, a mineral acid defoliated 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 the 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, and more preferably 0.5 mol / L or more and 1.0 mol / L or less as TiO ₂ .

From the viewpoint of making the shape of the strontium titanate particles into a rounded shape rather than a cube or a rectangular parallelepiped, it is preferable to add a dopant source to the mixture of the titanium oxide source and the strontium source. Dopant sources include oxides of metals other than titanium and strontium. The metal oxide as a dopant source is added, for example, as a solution dissolved in nitric acid, hydrochloric acid or sulfuric acid. The amount of the dopant source added is preferably 0.1 mol or more and 20 mol or less, and 0.5 mol or more and 10 mol or less, with respect to 100 mol of strontium contained in the strontium source. The amount is more preferred.

As the alkaline aqueous solution, a sodium hydroxide aqueous solution is preferable. The higher the temperature of the reaction solution when the alkaline aqueous solution is added, the better the crystallinity of strontium titanate particles can be obtained. The temperature of the reaction solution when the alkaline aqueous solution is added is preferably in the range of 60 ° C. or higher and 100 ° C. or lower from the viewpoint of having a perovskite-type crystal structure and a rounded shape. As for the addition rate of the alkaline aqueous solution, the slower the addition rate, the larger the strontium titanate particles can be obtained, and the faster the addition rate, the smaller the strontium titanate particles can be obtained. The addition rate of the alkaline aqueous solution is, for example, 0.001 equivalent / h or more and 1.2 equivalents / h or less, and 0.002 equivalents / h or more and 1.1 equivalents / 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. The acid treatment adjusts the pH of the reaction solution to 2.5 to 7.0, more preferably 4.5 to 6.0, using, for example, hydrochloric acid. After the acid treatment, the reaction solution is solid-liquid separated, and the solid content is dried to obtain strontium titanate particles.

For the surface treatment of strontium titanate particles, for example, a treatment liquid prepared by mixing a silicon-containing organic compound which is a hydrophobic treatment agent and a solvent is prepared, and the strontium titanate particles and the treatment liquid are mixed under stirring. This is done by 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 used for the surface treatment of strontium titanate particles include an alkoxysilane compound, a silazane compound, and silicone oil.

Examples of the alkoxysilane compound used for the surface treatment of strontium titanate particles include tetramethoxysilane and tetraethoxysilane; methyltrimethoxysilane, ethyltrimethoxysilane, propyltrimethoxysilane, butyltrimethoxysilane, and hexyltrimethoxysilane. n-octyltrimethoxysilane, decyltrimethoxysilane, dodecyltrimethoxysilane, vinyltriethoxysilane, methyltriethoxysilane, ethyltriethoxysilane, butyltriethoxysilane, hexyltriethoxysilane, decyltriethoxysilane, dodecyltriethoxysilane Silane, phenyltrimethoxysilane, o-methylphenyltrimethoxysilane, p-methylphenyltrimethoxysilane, phenyltriethoxysilane, benzyltriethoxysilane; dimethyldimethoxysilane, dimethyldiethoxysilane, methylvinyldimethoxysilane, methylvinyldi Ethoxysilane, diphenyldimethoxysilane, diphenyldiethoxysilane; trimethylmethoxysilane, trimethylethoxysilane; can be mentioned.

Examples of the silazane compound used for the surface treatment of strontium titanate particles include dimethyldisilazane, trimethyldisilazane, tetramethyldisilazane, pentamethyldisilazane, hexamethyldisilazane and the like.

Examples of the silicone oil used for the surface treatment of strontium titanate particles include silicone oils such as dimethylpolysiloxane, diphenylpolysiloxane, and phenylmethylpolysiloxane; amino-modified polysiloxane, epoxy-modified polysiloxane, carboxyl-modified polysiloxane, and carbinol. Reactive silicone oils such as modified polysiloxane, fluorine-modified polysiloxane, methacrylic-modified polysiloxane, mercapto-modified polysiloxane, and phenol-modified polysiloxane; and the like.

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

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

The amount of the silicon-containing organic compound used for the surface treatment is preferably 1 part by mass or more and 50 parts by mass or less, more preferably 5 parts by mass or more and 40 parts by mass or less, and 5 parts by mass or more with respect to 100 parts by mass of the strontium titanate particles. More preferably, it is 30 parts by mass or less.

<Static charge image developer>
The developer according to the present embodiment includes a toner and a carrier according to the present embodiment.

The developer according to the present embodiment is prepared by mixing the toner and the carrier according to the present embodiment in an appropriate blending ratio. The mixing ratio (mass ratio) of the toner and the carrier is preferably toner: carrier = 1: 100 to 30: 100, and more preferably 3: 100 to 20: 100.

[Toner for developing static charge image]
The toner is not particularly limited, and a known toner is used. For example, a colored toner containing toner particles containing a binder resin and a colorant can be mentioned, and an infrared absorbing toner using an infrared absorber instead of the colorant can also be mentioned. The toner may contain a mold release agent, various internal additives, external additives and the like.

-Bound resin-
Examples of the binder resin include styrenes (for example, styrene, parachlorostyrene, α-methylstyrene, etc.) and (meth) acrylic acid esters (for example, 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 (eg, acrylonitrile, etc.) Polymers (eg, methacrylnitrile, etc.), vinyl ethers (eg, vinylmethyl ether, vinylisobutyl ether, etc.), vinyl ketones (eg, vinylmethylketone, vinylethylketone, vinylisopropenylketone, etc.), olefins (eg, ethylene, propylene, butadiene, etc.) Examples thereof include a homopolymer of the above-mentioned monomers, or a vinyl-based resin composed of a copolymer obtained by combining two or more kinds of these monomers.
Examples of the binder resin include non-vinyl resins such as epoxy resins, polyester resins, polyurethane resins, polyamide resins, cellulose resins, polyether resins, and modified rosins, mixtures of these with the vinyl resins, or these. Examples thereof include a graft polymer obtained by polymerizing a vinyl-based monomer in the coexistence.
These binder resins may be used alone or in combination of two or more.

As the binder resin, a polyester resin is suitable. Examples of the polyester resin include known polyester resins.

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 the DSC curve obtained by differential scanning calorimetry (DSC), and more specifically, described in "Supplementary" described in JIS K7121-1987 "Method for measuring transition temperature of plastics". It is obtained by "outer glass transition start temperature".

The weight average molecular weight (Mw) of the polyester resin is preferably 5,000 or more and 1,000,000 or less, and more preferably 7,000 or more and 500,000 or less. The number average molecular weight (Mn) of the polyester resin is preferably 2000 or more and 100,000 or less. 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 the number average molecular weight are measured by gel permeation chromatography (GPC). The molecular weight measurement by GPC is performed by using Tosoh's GPC / HLC-8120GPC as a measuring device, using Tosoh's column / TSKgel SuperHM-M (15 cm), and using a THF solvent. The weight average molecular weight and the number average molecular weight are calculated from this measurement result using a molecular weight calibration curve prepared from a monodisperse polystyrene standard sample.

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

-Colorant-
Examples of colorants include carbon black, chrome yellow, Hansa yellow, benzine yellow, slene yellow, quinoline yellow, pigment yellow, permanent orange GTR, pyrazolon orange, vulcan orange, watch young red, permanent red, brilliant carmine 3B, and brilliant. Carmin 6B, Dupont Oil Red, Pyrazolon Red, Lissole Red, Rhodamin B Lake, Lake Red C, Pigment Red, Rose Bengal, Aniline Blue, Ultra Marine Blue, Calco Oil Blue, Methylene Blue Chloride, Phthalocyanine Blue, Pigment Blue, Phthalocyanine Green, Pigments such as malakite green oxalate; aclysin-based, xanthene-based, azo-based, benzoquinone-based, azine-based, anthraquinone-based, thioindico-based, dioxazine-based, thiazine-based, azomethine-based, indico-based, phthalocyanine-based, aniline black-based, polymethine-based , Triphenylmethane-based, diphenylmethane-based, thiazole-based dyes; and the like.
The colorant may be used alone or in combination of two or more.

As the colorant, a surface-treated colorant may be used or may be used in combination with a dispersant, if necessary. Further, a plurality of kinds of colorants may be used in combination.

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.

-Release agent-
Examples of the release agent include hydrocarbon waxes; natural waxes such as carnauba wax, rice wax and candelilla wax; synthetic or mineral / petroleum waxes such as montan wax; ester waxes such as fatty acid esters and 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) by the "melting peak temperature" described in the method for determining the melting temperature in JIS K7121-1987 "Method for measuring the transition 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 magnetic materials, charge control agents, and inorganic powders. These additives are contained in the toner particles as an internal additive.

-Characteristics of toner particles-
The toner particles may be toner particles having a single layer structure, or may be toner particles having a so-called core-shell structure composed of a core portion (core particles) and a coating layer (shell layer) covering the core portion. You may. The toner particles having a core-shell structure are composed of, for example, a core portion composed of a binder resin and, if necessary, other additives such as a colorant and a mold release agent, and a binder resin. It may be composed of a coating layer and.

The volume average particle size (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 size (D50v) of the toner particles is measured using Coulter Multisizer II (manufactured by Beckman Coulter), and the electrolytic solution is measured using ISOTON-II (manufactured by Beckman Coulter). At the time of measurement, 0.5 mg or more and 50 mg or less of the measurement sample is added to 2 ml of a 5% by mass aqueous solution of a surfactant (preferably sodium alkylbenzene sulfonate) as a dispersant. This is added to 100 ml or more and 150 ml or less of the electrolytic solution. The electrolytic solution in which the sample is suspended is dispersed for 1 minute with an ultrasonic disperser, and the particle size distribution of particles having a particle size in the range of 2 μm or more and 60 μm or less is measured by using an aperture with an aperture diameter of 100 μm using a Coulter Multisizer II. do. The number of particles to be sampled is 50,000.

-External agent-
Examples of the external additive include inorganic particles. As the 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. Examples thereof include SiO ₂ , K ₂ O · (TIO ₂ ) n, Al ₂ O _{3.2SiO 2} , CaCO ₃ , MgCO ₃ , BaSO ₄ , and _Л4 .

The surface of the inorganic particles as an external additive should be hydrophobized. The hydrophobizing treatment is performed, for example, by immersing the inorganic particles in the hydrophobizing agent. The hydrophobizing agent is not particularly limited, and examples thereof include a silane-based coupling agent, a silicone oil, a titanate-based coupling agent, and an aluminum-based coupling agent. These may be used alone or in combination of two or more.
The amount of the hydrophobizing agent is usually, for example, 1 part by mass or more and 10 parts by mass with respect to 100 parts by mass of the inorganic particles.

Examples of the external additive include resin particles (resin particles such as polystyrene, polymethylmethacrylate, and melamine resin), cleaning active agents (for example, metal salts of higher fatty acids typified by zinc stearate, particles of fluoropolymer). And so on.

The amount of the external additive added is preferably 0.01% by mass or more and 5% by mass or less, and more preferably 0.01% by mass or more and 2.0% by mass or less with respect to the toner particles.

-Toner manufacturing method-
Toner can be obtained by externally adding an external additive to the toner particles after manufacturing the toner particles. The toner particles may be produced by any of a dry production method (for example, a kneading and pulverizing method, etc.) and a wet production method (for example, an agglomeration coalescence method, a suspension polymerization method, a dissolution suspension method, etc.). There are no particular restrictions on these manufacturing methods, and known manufacturing methods are adopted. Among these, it is preferable to obtain toner particles by the aggregation and coalescence method.

<Image forming device, image forming method>
An image forming apparatus and an image forming method according to the present embodiment will be described.
The image forming apparatus according to the present embodiment includes an image holder, a charging means for charging the surface of the image holder, a static charge image forming means for forming an electrostatic charge image on the surface of the charged image holder, and an electrostatic charge. A developing means that accommodates an image developer and develops a static charge image formed on the surface of the image holder as a toner image by the static charge image developer, and a recording medium that records the toner image formed on the surface of the image holder. It is provided with a transfer means for transferring to the surface of the recording medium and a fixing means for fixing the toner image transferred to the surface of the recording medium. Then, as the static charge image developer, the static charge image developer according to the present embodiment is applied.

In the image forming apparatus according to the present embodiment, a charging step of charging the surface of the image holder, a static charge image forming step of forming an electrostatic charge image on the surface of the charged image holder, and an electrostatic charge according to the present embodiment. A development step of developing an electrostatic charge image formed on the surface of an image holder as a toner image with an image developer, and a transfer step of transferring a toner image formed on the surface of the image holder to the surface of a recording medium. An image forming method (image forming method according to the present embodiment) having a fixing step of fixing a toner image transferred to the surface of a recording medium is carried out.

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

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

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

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

Above each unit 10Y, 10M, 10C, and 10K, an intermediate transfer belt (an example of an intermediate transfer body) 20 is extended through each unit. The intermediate transfer belt 20 is provided so as to be wound around the drive roll 22 and the support roll 24 so as to travel in the direction from the first unit 10Y to the fourth unit 10K. 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 body cleaning device 30 is provided on the side surface of the image holder of the intermediate transfer belt 20 so as to face the drive roll 22.
Developing equipment for each unit 10Y, 10M, 10C, 10K (an example of developing means) Yellow, magenta, cyan, and black contained in toner cartridges 8Y, 8M, 8C, and 8K for each of 4Y, 4M, 4C, and 4K. Each toner is supplied.

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

The first unit 10Y has a photoconductor 1Y that acts as an image holder. Around the photoconductor 1Y, a charging roll (an example of charging means) 2Y that charges the surface of the photoconductor 1Y to a predetermined potential, and a laser beam 3Y based on a color-decomposed image signal expose the charged surface. An exposure device (an example of a static charge image forming means) 3 for forming an electrostatic charge image, and a developing device (an example of a developing means) 4Y for developing a static charge image by supplying a charged toner to the static charge image. A primary transfer roll 5Y (an example of a primary transfer means) that transfers a toner image onto an intermediate transfer belt 20, and a photoconductor cleaning device (an example of a cleaning means) 6Y that removes toner remaining on the surface of the photoconductor 1Y after the primary transfer. Are arranged in order.
The primary transfer roll 5Y is arranged inside the intermediate transfer belt 20 and is provided at a position facing the photoconductor 1Y. A bias power supply (not shown) for applying a primary transfer bias is connected to each of the primary transfer rolls 5Y, 5M, 5C, and 5K of each unit. Each bias power supply changes the value of the transfer bias applied to each primary transfer roll by control by a control unit (not shown).

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

The static charge image is an image formed on the surface of the photoconductor 1Y by charging. The laser beam 3Y reduces the resistivity of the irradiated portion of the photosensitive layer, and the charged charge on the surface of the photoconductor 1Y flows. On the other hand, it is a so-called negative latent image formed by the residual charge of the portion not irradiated with the laser beam 3Y.
The electrostatic charge image formed on the photoconductor 1Y rotates to a predetermined development position as the photoconductor 1Y runs. Then, at this developing position, the electrostatic charge image on the photoconductor 1Y is developed and visualized as a toner image by the developing device 4Y.

In the developing apparatus 4Y, for example, a static charge image developing agent containing at least a yellow toner and a carrier is housed. The yellow toner is triboelectrically charged by being agitated inside the developing apparatus 4Y, and has a charge having the same polarity (negative electrode property) as the charged charge on the photoconductor 1Y, and is a developer roll (developer holder). Example) It is held on. Then, as the surface of the photoconductor 1Y passes through the developing device 4Y, the yellow toner is electrostatically adhered to the statically eliminated latent image portion on the surface of the photoconductor 1Y, and the latent image is developed by the yellow toner. Toner. The photoconductor 1Y on which the yellow toner image is formed is continuously traveled at a predetermined speed, and the toner image developed on the photoconductor 1Y is conveyed to a predetermined primary transfer position.

When the yellow toner image on the photoconductor 1Y is conveyed to the primary transfer position, a primary transfer bias is applied to the primary transfer roll 5Y, and an electrostatic force from the photoconductor 1Y toward the primary transfer roll 5Y acts on the toner image to be photosensitive. The toner image on the body 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 a control unit (not shown) in the first unit 10Y.
On the other hand, the toner remaining on the photoconductor 1Y is removed by the photoconductor cleaning device 6Y and recovered.

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 on which the yellow toner image is transferred by the first unit 10Y is sequentially conveyed through the second to fourth units 10M, 10C, and 10K, and the toner images of each color are superimposed and multiple transfer. Will be done.

The intermediate transfer belt 20 to which the toner images of four colors are multiplex-transferred through the first to fourth units includes the intermediate transfer belt 20, the support roll 24 in contact with the inner surface of the intermediate transfer belt, and the image holding surface of the intermediate transfer belt 20. It leads to a secondary transfer unit composed of a secondary transfer roll (an example of the secondary transfer means) 26 arranged on the side. On the other hand, the recording paper (an example of the recording medium) P is fed to the gap where the secondary transfer roll 26 and the intermediate transfer belt 20 are in contact with each other via the supply mechanism at a predetermined timing, and the secondary transfer bias is supported by the support roll. It is applied to 24. The transfer bias applied at this time has the same polarity (-) as the toner polarity (-), and the 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 of is transferred onto the recording paper P. The secondary transfer bias at this time is determined according to the resistance detected by the resistance detecting means (not shown) for detecting the resistance of the secondary transfer unit, and is voltage controlled.

After that, the recording paper P is sent to the pressure contact portion (nip portion) of the pair of fixing rolls in the fixing device (an example of the fixing means) 28, the toner image is fixed on the recording paper P, and the fixing image is formed. ..

Examples of the recording paper P for transferring the toner image include plain paper used in electrophotographic copying machines, printers, and the like. Examples of the recording medium include an OHP sheet and the like in addition to the recording paper P.
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 or the like, art paper for printing, or the like is used. It is preferably used.

The recording paper P for which the fixing of the color image is completed is carried out toward the ejection unit, and a series of color image forming operations is completed.

<Process cartridge>
The process cartridge according to this embodiment will be described.
The process cartridge according to the present embodiment contains the electrostatic charge image developer according to the present embodiment, and is a developing means for developing the electrostatic charge image formed on the surface of the image holder as a toner image by the electrostatic charge image developer. It is a process cartridge that is attached to and detached from the image forming apparatus.

The process cartridge according to the present embodiment is not limited to the above configuration, and can be selected from developing means and other means such as an image holder, a charging means, an electrostatic charge image forming means, and a transfer means, if necessary. It may be configured to include at least one of the above.

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

FIG. 3 is a schematic configuration diagram showing a process cartridge according to the present embodiment.
The process cartridge 200 shown in FIG. 3 is provided around the photoconductor 107 (an example of an image holder) and the periphery of the photoconductor 107 by, for example, a housing 117 provided with a mounting rail 116 and an opening 118 for exposure. The charged roll 108 (an example of the charging means), the developing device 111 (an example of the developing means), and the photoconductor cleaning device 113 (an example of the cleaning means) are integrally combined and held and configured to form a cartridge. There is.
In FIG. 3, 109 is an exposure device (an example of an electrostatic charge image forming means), 112 is a transfer device (an example of a transfer means), 115 is a fixing device (an example of a fixing means), and 300 is a recording paper (an example of a recording medium). Is shown.

Hereinafter, embodiments of the invention will be described in detail with reference to Examples, but the embodiments of the invention are not limited to these Examples. In the following description, unless otherwise specified, "parts" and "%" are all based on mass.

<Making toner>
[Preparation of resin particle dispersion liquid (1)]
・ Ethylene glycol (Wako Pure Chemical Industries) 37 parts ・ Neopentyl glycol (Wako Pure Chemical Industries) 65 parts ・ 1,9-nonandiol (Wako Pure Chemical Industries) 32 parts ・ Terephthalic acid (Wako Pure Chemical Industries) 96 parts The material of No. 1 was charged in a flask, the temperature was raised to 200 ° C. over 1 hour, and after confirming that the inside of the reaction system was uniformly stirred, 1.2 parts of dibutyltin oxide was added. The temperature was raised to 240 ° C. over 6 hours while distilling off the generated water, and stirring was continued at 240 ° C. for 4 hours. Polyester resin (acid value 9.4 mgKOH / g, weight average molecular weight 13,000, glass transition temperature) 62 ° C.) was obtained. The polyester resin was transferred to an emulsification disperser (Cavitron CD1010, Eurotech Co., Ltd.) in a molten state at a rate of 100 g / min. Separately, dilute the reagent ammonia water with ion-exchanged water and dilute 0.37% concentration of dilute ammonia water is put in a tank, and it is emulsified at the same time as the polyester resin at a rate of 0.1 liter per minute while heating at 120 ° C. with a heat exchanger. Transferred to a disperser. The emulsification disperser was operated under the conditions of a rotor rotation speed of 60 Hz and a pressure of 5 kg / cm ² , to obtain a resin particle dispersion liquid (1) having a volume average particle size of 160 nm and a solid content of 30%.

[Preparation of resin particle dispersion liquid (2)]
・ Decandic acid (Tokyo Chemical Industry) 81 parts ・ Hexanediol (Wako Pure Chemical Industries) 47 parts The above materials are placed in a flask and the temperature is raised to 160 ° C over 1 hour, and the inside of the reaction system is uniformly stirred. After confirming that, 0.03 part of dibutyltin oxide was added. The temperature was raised to 200 ° C. over 6 hours while distilling off the generated water, and stirring was continued at 200 ° C. for 4 hours. Next, the reaction solution was cooled, solid-liquid separation was performed, and the solid substance was dried at a temperature of 40 ° C./reduced pressure to obtain a polyester resin (C1) (melting point 64 ° C., weight average molecular weight 15,000).

-Polyester resin (C1) 50 parts-Anionic surfactant (Neogen SC, Dai-ichi Kogyo Seiyaku) 2 parts-Ion-exchanged water 200 parts Homogenizer (Ultratalax T50, IKA) by heating the above material to 120 ° C. After sufficient dispersion with a pressure discharge homogenizer, the dispersion treatment was performed with a pressure discharge homogenizer. When the volume average particle size reached 180 nm, the particles were recovered to obtain a resin particle dispersion liquid (2) having a solid content of 20%.

[Preparation of colorant particle dispersion liquid (1)]
・ Cyan pigment (Particle15: 3, Dainichiseika Kogyo) 10 parts ・ Anionic surfactant (Neogen SC, Daiichi Kogyo Seiyaku) 2 parts ・ Ion exchange water 80 parts Mix the above materials and use a high pressure impact disperser. (Ultimizer HJP30006, Sugino Machine Limited) was used for dispersion for 1 hour to obtain a colorant particle dispersion liquid (1) having a volume average particle size of 180 nm and a solid content of 20%.

[Preparation of release agent particle dispersion liquid (1)]
・ Paraffin wax (HNP-9, Nippon Seiwa) 50 parts ・ Anionic surfactant (Neogen SC, Daiichi Kogyo Seiyaku) 2 parts ・ Ion exchange water 200 parts Heat the above material to 120 ° C and homogenizer ( After sufficient dispersion with Ultratarax T50, IKA), dispersion treatment was performed with a pressure discharge homogenizer. When the volume average particle size reached 200 nm, the particles were collected to obtain a release agent particle dispersion liquid (1) having a solid content of 20%.

[Preparation of toner (1)]
・ Resin particle dispersion (1) 150 parts ・ Resin particle dispersion (2) 50 parts ・ Colorant particle dispersion (1) 25 parts ・ Release agent particle dispersion (1) 35 parts ・ Polyaluminum chloride 0.4 Part ・ 100 parts of ion-exchanged water Put the above materials into a round stainless steel flask, mix and disperse them sufficiently using a homogenizer (Ultratalax T50, IKA), and then stir the inside of the flask to heat the oil bath. Was heated to 48 ° C. After holding the inside of the reaction system at 48 ° C. for 60 minutes, 70 parts of the resin particle dispersion liquid (1) was slowly added. Then, the pH was adjusted to 8.0 using a 0.5 mol / L sodium hydroxide aqueous solution, the flask was sealed, the seal of the stirring shaft was magnetically sealed, and the mixture was heated to 90 ° C. for 30 minutes while continuing stirring. Retained. Then, the mixture was cooled at a temperature lowering rate of 5 ° C./min, solid-liquid separated, and thoroughly washed with ion-exchanged water. Then, solid-liquid separation was performed, the mixture was redistributed in ion-exchanged water at 30 ° C., and the mixture was stirred and washed at a rotation speed of 300 rpm for 15 minutes. This washing operation was repeated 6 more times, and when the pH of the filtrate became 7.54 and the electric conductivity became 6.5 μS / cm, solid-liquid separation was performed, vacuum drying was continued for 24 hours, and the volume average particle size was 5. 7 μm toner particles were obtained.

100 parts of the above toner particles and 2.5 parts of silica particles (surface hydrophobic treated with hexamethyldisilazane and having an average primary particle size of 40 nm) were mixed with a Henschel mixer to obtain toner (1).

<Making magnetic particles>
[Ferrite particles (1)]
1597 parts of Fe ₂ O ₃ , 712 parts of Mn (OH) ₂ , 116 parts of Mg (OH) ₂ , 20 parts of SrCO ₃ and 30 parts of CaCO ₃ are mixed, dispersant, water and zirconia with a diameter of 1 mm. Beads were added, and the mixture was crushed and mixed using a sand mill. The zirconia beads were filtered off, the filtrate was dried, and then calcined using a rotary kiln under the conditions of a rotation speed of 20 rpm / a temperature of 970 ° C./2 hours. A dispersant and water were added to the obtained calcined product, 8 parts of polyvinyl alcohol was further added, and pulverization and mixing was carried out for 5 hours using a wet ball mill. The volume average particle size of the obtained pulverized product was 1.2 μm. Then, using a spray dryer, granulation was performed so that the particle size was 40 μm. The obtained granulated product was main-baked using an electric furnace in an oxygen-nitrogen mixed atmosphere having an oxygen concentration of 1% by volume under the condition of a temperature of 1400 ° C./4 hours. The obtained fired product was crushed and classified to obtain ferrite particles (1). The volume average particle size of the ferrite particles (1) was 35 μm.

[Ferrite particles (2) to (17)]
Ferrite particles (2) to (17) were produced in the same manner as in the production of the ferrite particles (1) except that the amount of SrCO ₃ and the amount of CaCO ₃ were changed as shown in Table 1.

Using each of the ferrite particles (1) to (17) as a sample, the contents of the calcium element and the strontium element were analyzed by the above-mentioned method.

<Manufacturing of resin-coated magnetic particles>
・ Cyclohexyl acrylate resin (weight average molecular weight 50,000) 30 parts ・ Polyisocyanate (Coronate L, Tosoh) 6 parts ・ Carbon black (VXC72, Cabot) 4 parts ・ Toluene 250 parts ・ Methanol 50 parts The above materials and glass beads (diameter) 1 mm (1 mm, the same amount as toluene) was put into a sand mill (Kansai Paint Co., Ltd.) and stirred at a rotation speed of 1200 rpm for 30 minutes to prepare a coating liquid (1) having a solid content of 11%.

Put 200 parts of ferrite particles (1) to (17) in a vacuum degassing type kneader, add 36 parts of coating liquid (1), raise and lower the pressure while stirring, and create an atmosphere of 90 ° C / -720 mHg. It was stirred underneath for 30 minutes and dried. Then, sieving was performed with a sieving network of 75 μm mesh to obtain resin-coated ferrite particles (1) to (17).

Using each of the resin-coated ferrite particles (1) to (17) as a sample, the exposure ratio of the ferrite particles was analyzed by the above-mentioned method.

Table 1 shows the compositions of the resin-coated ferrite particles (1) to (17). In Table 1, "D50v" means the volume average particle size.

<Preparation of strontium titanate particles>
[Strontium titanate particles (1)]
0.7 mol of metatitanium acid, which is a source of desulfurized and deflated titanium, was collected as TiO ₂ and placed in a reaction vessel. Next, 0.77 mol of an aqueous solution of strontium chloride was added to the reaction vessel so that the SrO / TiO ₂ mol ratio was 1.1. Then, a solution of lanthanum oxide dissolved in nitric acid was added to the reaction vessel in an amount of 2.5 mol of lanthanum with respect to 100 mol of strontium. The initial TiO ₂ concentration in the mixture of the three materials was adjusted to 0.75 mol / L. Next, the mixed solution was stirred, the mixed solution was heated to 90 ° C., the liquid temperature was maintained at 90 ° C., and 153 mL of a 10N sodium hydroxide aqueous solution was added over 4 hours while stirring, and the liquid temperature was further increased to 90. Stirring was continued for 1 hour while maintaining the temperature at ° C. Then, the reaction solution was cooled to 40 ° C., hydrochloric acid was added until the pH reached 5.5, and the mixture was stirred for 1 hour. The precipitate was then washed by repeating decantation and redispersion in water. Hydrochloric acid was added to the slurry containing the washed precipitate to adjust the pH to 6.5, and the solid content was filtered off and dried. An ethanol solution of i-butyltrimethoxysilane (i-BTMS) was added to the dried solid content in an amount of 20 parts of i-BTMS with respect to 100 parts of the solid content, and the mixture was stirred for 1 hour. The solid content was filtered off, and the solid content was dried in the air at 130 ° C. for 7 hours to obtain strontium titanate particles (1).

[Strontium titanate particles (2)]
Strontium titanate particles (2) were produced in the same manner as in the production of strontium titanate particles (1), except that the time required for dropping the 10N sodium hydroxide aqueous solution was changed to 1 hour.

[Strontium titanate particles (3)]
Strontium titanate particles (3) were produced in the same manner as in the production of strontium titanate particles (1), except that the time required for dropping the 10N sodium hydroxide aqueous solution was changed to 2.8 hours.

[Strontium titanate particles (4)]
Strontium titanate particles (4) were produced in the same manner as in the production of strontium titanate particles (1), except that the time required for dropping the 10N sodium hydroxide aqueous solution was changed to 11 hours.

[Strontium titanate particles (5)]
Strontium titanate particles (5) were produced in the same manner as in the production of strontium titanate particles (1), except that the time required for dropping the 10N sodium hydroxide aqueous solution was changed to 14.5 hours.

[Strontium titanate particles (6)]
Strontium titanate particles (6) were produced in the same manner as in the production of strontium titanate particles (1), except that the time required for dropping the 10N sodium hydroxide aqueous solution was changed to 17 hours.

[Strontium titanate particles (7)]
Commercially available strontium titanate particles (SW-360 manufactured by Titanium Industry Co., Ltd.) were prepared and subjected to the same surface treatment as the i-BTMS treatment in the production of the strontium titanate particles (1), and the strontium titanate particles (7) were subjected to the same surface treatment. ) Was produced. SW-360 manufactured by Titan Kogyo Co., Ltd. is strontium titanate particles whose surface is untreated without being doped with metal elements.

[Measurement of shape of strontium titanate particles]
The separately prepared resin particles and any of the strontium titanate particles (1) to (7) were mixed for 15 minutes at a stirring peripheral speed of 30 m / sec using a Henschel mixer. Then, the particles were sieved using a vibrating sieve having an opening of 45 μm, and the strontium titanate particles were attached to the resin particles.
Images of the resin particles to which the strontium titanate particles were attached were taken at a magnification of 40,000 times using a scanning electron microscope (SEM) (Hitachi High-Technologies Corporation, S-4700). Image information of 300 randomly selected strontium titanate particles was analyzed by image processing analysis software WinRof (Mitani Shoji Co., Ltd.) via an interface, and the equivalent circle diameter, area, and perimeter of each primary particle image were obtained. Was obtained, and further, circularity = 4π × (area) ÷ (peripheral length) ² . Then, the circle equivalent diameter that is cumulatively 50% from the small diameter side in the distribution of the circle equivalent diameter is defined as the average primary particle size, and the circularity that is cumulatively 50% from the small diameter side in the circularity distribution is defined as the average circularity. The circularity with a cumulative total of 84% from the smaller side in the distribution was defined as the cumulative 84% circularity.

[X-ray diffraction of strontium titanate particles]
Using each of the strontium titanate particles (1) to (7) as a sample, a crystal structure analysis was performed using an X-ray diffractometer (manufactured by Rigaku Co., Ltd., trade name: RINT Ultima-III) under the above-mentioned condition settings. The strontium titanate particles (1) to (7) had a peak corresponding to the peak of the (110) plane of the perovskite crystal near the diffraction angle 2θ = 32 °.

[Volume intrinsic resistivity R of strontium titanate particles]
Using each of the strontium titanate particles (1) to (7) as a sample, the volume resistivity R was measured by the measurement method described above.

[Water content of strontium titanate particles]
Using each of the strontium titanate particles (1) to (7) as a sample, the water content was measured by the above-mentioned measuring method.

Table 2 shows the characteristics of the strontium titanate particles (1) to (7).

<Manufacturing of carrier and developer>
[Example 1]
100 parts of the resin-coated ferrite particles (1) and 0.05 part of strontium titanate (1) were charged in a V-blender, and the mixture was stirred and mixed for 20 minutes to obtain a carrier (1).

100 parts of the carrier (1) and 6 parts of the toner (1) were charged in the V blender and stirred for 20 minutes. Then, it was sieved with a sieve having an opening of 212 μm to obtain a cyan-colored developer.

[Examples 2 to 80, Comparative Examples 1 to 12]
In the same manner as in Example 1, however, as shown in Tables 3 to 4, the type of the resin-coated ferrite particles and the type or external addition amount of the strontium titanate particles (mass% with respect to the mass of the resin-coated ferrite particles) are set. Each carrier and developer were prepared by modification.

<Performance evaluation>
A developer was charged in an image forming apparatus (a modified machine of DocuCentre Color 400) and left for 12 hours in an environment of a temperature of 30 ° C. and a relative humidity of 88%. After being left to stand, images were continuously formed on 1000 sheets of A4 size paper. As for the image, a 20 cm × 25 cm density 100% image was formed on the upper part in the vertical direction of the paper, and Roman letters from A to Z were formed on the lower part in MS Gothic / 14 points / half-width. The state of the 1000th character was visually confirmed and classified as follows.

-Cover-
A (◎): No toner fog is observed around the characters.
B (○): Toner fog is slightly observed around the characters (to the extent that it can be confirmed with a magnifying glass 5 times), but it is not a problem.
C (Δ): Toner fog is slightly observed around the characters, but it is slight and does not affect practical use.
D (Δ- ⁾ : Toner fog is visually observed around the characters, but it is slight and does not affect practical use.
E (x): Toner fog is observed around the characters, which is not suitable for practical use.

-Reproducibility of thin lines-
A (◎): No thickening, crushing or blurring of lines is observed.
B (○): Thickness, crushing, or blurring of lines is slightly observed, but it is not a problem.
C (Δ): Thickness, crushing, or blurring of the line is observed, but it is slight and does not interfere with practical use. D (x): Line thickening, crushing or blurring is observed, which is unsuitable for practical use.

The composition and performance evaluation results of Examples 1 to 80 and Comparative Examples 1 to 12 are shown in Tables 3 to 4.

1Y, 1M, 1C, 1K Photoreceptor (Example of image holder)
2Y, 2M, 2C, 2K Charging roll (an example of charging means)
3 Exposure device (an example of static charge image forming means)
3Y, 3M, 3C, 3K laser beam 4Y, 4M, 4C, 4K developing device (an example of developing means)
5Y, 5M, 5C, 5K primary transfer roll (an example of primary transfer means)
6Y, 6M, 6C, 6K Photoreceptor cleaning device (an example of cleaning means)
8Y, 8M, 8C, 8K Toner Cartridge 10Y, 10M, 10C, 10K Image Forming Unit 20 Intermediate Transfer Belt (Example of Intermediate Transfer)
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 element cleaning device P Recording paper (an example of recording medium)

107 Photoreceptor (an example of image holder)
108 Charging roll (an example of charging means)
109 Exposure device (an example of static charge image forming means)
111 Developing equipment (an example of developing means)
112 Transfer device (an example of transfer means)
113 Photoreceptor cleaning device (an example of cleaning means)
115 Fixing device (an example of fixing means)
116 Mounting rail 117 Housing 118 Opening for exposure 200 Process cartridge 300 Recording paper (an example of recording medium)

Claims (16)

Resin-coated magnetic particles having magnetic particles and a resin layer covering the magnetic particles, and
Strontium titanate particles having a half-value width of the peak of the (110) plane obtained by the X-ray diffraction method externally attached to the resin-coated magnetic particles of 0.2 ° or more and 2.0 ° or less, and the strontium titanate particles.
Carrier for static charge image development including. The carrier for developing an electrostatic charge image according to claim 1, wherein the strontium titanate particles are strontium titanate particles containing a dopant. The carrier for developing an electrostatic charge image according to claim 2, wherein the dopant contains a lantern. The carrier for developing an electrostatic charge image according to any one of claims 1 to 3, wherein the strontium titanate particles have an average primary particle size of 10 nm or more and 100 nm or less. The carrier for developing an electrostatic charge image according to claim 4, wherein the strontium titanate particles have an average primary particle size of 15 nm or more and 60 nm or less. The invention according to any one of claims 1 to 5, wherein the content of the strontium titanate particles is 0.01% by mass or more and 0.5% by mass or less with respect to the mass of the resin-coated magnetic particles. Carrier for static charge image development. The carrier for static charge image development according to claim 6, wherein the content of the strontium titanate particles is 0.02% by mass or more and 0.08% by mass or less with respect to the mass of the resin-coated magnetic particles. The carrier for static charge image development according to any one of claims 1 to 7, wherein the exposure ratio of the magnetic particles on the surface of the resin-coated magnetic particles is 2% or more and 20% or less. The carrier for developing an electrostatic charge image according to any one of claims 1 to 8, wherein the magnetic particles are ferrite particles. The ferrite particles contain at least one selected from calcium oxide and strontium oxide, and the total content of calcium element and strontium element is 0.1% by mass or more and 2.0% by mass or less with respect to the entire ferrite particles. The carrier for developing an electrostatic charge image according to claim 9. The static charge image development according to claim 9, wherein the ferrite particles contain calcium oxide and the content of calcium element is 0.2% by mass or more and 2.0% by mass or less with respect to the entire ferrite particles. Career. The static charge image development according to claim 9, wherein the ferrite particles contain a strontium oxide and the content of the strontium element is 0.1% by mass or more and 1.0% by mass or less with respect to the entire ferrite particles. Career. A static charge image developer comprising a toner for static charge image development and a carrier for static charge image development according to any one of claims 1 to 12. A developing means for accommodating the electrostatic charge image developer according to claim 13 and developing the electrostatic charge image formed on the surface of the image holder as a toner image by the electrostatic charge image developer is provided.
A process cartridge that is attached to and detached from the image forming device. Image holder and
A charging means for charging the surface of the image holder, and
An electrostatic charge image forming means for forming an electrostatic charge image on the surface of the charged image holder, and
A developing means for accommodating the electrostatic charge image developer according to claim 13 and developing the electrostatic charge image formed on the surface of the image holder as a toner image by the electrostatic charge image developer.
A transfer means for transferring a toner image formed on the surface of the image holder to the surface of a recording medium,
A fixing means for fixing the toner image transferred to the surface of the recording medium, and
An image forming apparatus. The charging process that charges the surface of the image holder,
A static charge image forming step of forming a static charge image on the surface of the charged image holder, and
A developing step of developing an electrostatic charge image formed on the surface of the image holder as a toner image by using the electrostatic charge image developer according to claim 13.
A transfer step of transferring a toner image formed on the surface of the image holder to the surface of a recording medium, and
A fixing step of fixing the toner image transferred to the surface of the recording medium, and
Image forming method having.

Images