Method for producing toner for developing electrostatic images, and toner for developing electrostatic images

Abstract

To provide a method for manufacturing toner for electrostatic charge image development with a low surface exposure of a release agent.SOLUTION: A method for manufacturing toner for electrostatic charge image development includes: a first aggregation step of aggregating at least resin particles and release agent particles contained in a dispersion liquid to prepare a dispersion liquid A containing first aggregated particles; a second aggregation step of adding a dispersion liquid B containing resin particles for a shell to the dispersion liquid A and aggregating the resin particles for the shell to form second aggregated particles; and a fusion step of heating and fusing the second aggregated particles to form fused particles. A pH(A) that is a pH of the dispersion liquid A and a pH(B) that is a pH of the dispersion liquid B in the second aggregation step satisfy pH(A)<pH(B).SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a method for producing a toner for developing electrostatic images, and a toner for developing electrostatic images. [Background technology]

[0002] Methods for visualizing image information, such as electrophotography, are currently used in various fields. In electrophotography, an electrostatic image is formed as image information on the surface of an image carrier by charging and forming an electrostatic image. Then, a toner image is formed on the surface of the image carrier by a developer containing a toner, and the toner image is transferred to a recording medium, and then fixed to the recording medium. Through these steps, the image information is visualized as an image.

[0003] For example, Patent Document 1 discloses a toner for developing electrostatic latent images, which includes a plurality of toner particles each having a core and a shell layer covering the surface of the core, wherein the core contains a crystalline polyester resin and a release agent, the surface of the core includes a covered region covered with the shell layer and an exposed region not covered with the shell layer, the proportion of the area of ​​the covered region on the surface of the core being 60% or more and 80% or less, and the proportion of the area of ​​the exposed region having a surface adsorptive force of 25 nN or more being 8% or less. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2017-125957 A Summary of the Invention [Problem to be solved by the invention]

[0005] The object of the present invention is to provide a method for producing an electrostatic charge image developing toner with a small surface exposure rate of a release agent, compared to the case where pH(A), which is the pH of the dispersion A in the second aggregation step, and pH(B), which is the pH of the dispersion B, satisfy pH(A) ≥ pH(B). The method includes a first aggregation step of aggregating at least resin particles and release agent particles contained in a dispersion to produce a dispersion A containing first aggregated particles, a second aggregation step of adding a dispersion B containing resin particles for a shell to the dispersion A and aggregating the resin particles for the shell to form second aggregated particles, and a fusion step of heating and fusing the second aggregated particles to form fused particles.

Means for Solving the Problems

[0006] The means for solving the above problems include the following aspects. <1> A method for producing an electrostatic charge image developing toner, including a first aggregation step of aggregating at least resin particles and release agent particles contained in a dispersion to produce a dispersion A containing first aggregated particles, a second aggregation step of adding a dispersion B containing resin particles for a shell to the dispersion A and aggregating the resin particles for the shell to form second aggregated particles, and a fusion step of heating and fusing the second aggregated particles to form fused particles, wherein pH(A), which is the pH of the dispersion A in the second aggregation step, and pH(B), which is the pH of the dispersion B, satisfy pH(A) < pH(B). <2> The method for producing an electrostatic charge image developing toner according to <1>, wherein pH(A) and pH(B) in the second aggregation step satisfy 0.2 < pH(B) - pH(A) < 3.0. <3> The method for producing an electrostatic charge image developing toner according to <2>, wherein pH(A) and pH(B) in the second aggregation step satisfy 0.5 < pH(B) - pH(A) < 1.5. <4> The method for producing an electrostatic charge image developing toner according to any one of <1> to <3>, wherein temperature T(A) of the dispersion A and temperature T(B) of the dispersion B in the second aggregation step satisfy T(A) > T(B). <5> The method for producing an electrostatic charge image developing toner according to <4>, wherein the temperature T(A) of the dispersion liquid A and the temperature T(B) of the dispersion liquid B in the second aggregation step satisfy -37°C < T(B) - T(A) < -13°C. <6> The method for producing an electrostatic charge image developing toner according to <5>, wherein the temperature T(A) of the dispersion liquid A and the temperature T(B) of the dispersion liquid B in the second aggregation step satisfy -30°C < T(B) - T(A) < -20°C. <7> The method for producing an electrostatic charge image developing toner according to any one of <1> to <6>, wherein the pH(B) is 3.5 or more and 6.0 or less. <8> The method for producing an electrostatic charge image developing toner according to any one of <1> to <7>, wherein the T(B) is 15°C or more and 25°C or less. <9> The method for producing an electrostatic charge image developing toner according to any one of <1> to <8>, wherein the addition rate of the dispersion liquid B in the second aggregation step is 0.6 part by mass or more and 1.2 parts by mass or less per 100 parts by mass of the dispersion liquid A. <10> The method for producing an electrostatic charge image developing toner according to any one of <1> to <9>, wherein the resin particles aggregated in the aggregation step are polyester resin particles. <11> The method for producing an electrostatic charge image developing toner according to any one of <1> to <10>, wherein the resin particles for the shell are polyester resin particles. <12> An electrostatic charge image developing toner produced by the method for producing an electrostatic charge image developing toner according to any one of <1> to <11>.

Advantages of the Invention

[0007] <1> According to the invention, there is provided a method for producing a toner for developing electrostatic images, the method comprising: a first aggregation step of aggregating at least resin particles and release agent particles contained in a dispersion to prepare dispersion A containing first aggregated particles; a second aggregation step of adding dispersion B containing shell resin particles to dispersion A to aggregate the shell resin particles to form second aggregated particles; and a fusion step of heating and fusing the second aggregated particles to form fused particles, wherein the surface exposure rate of the release agent is smaller than when pH(A), which is the pH of dispersion A in the second aggregation step, and pH(B), which is the pH of dispersion B, satisfy pH(A)≧pH(B). <2> According to the invention, there is provided a method for producing a toner for developing electrostatic images, in which the surface exposure rate of the release agent is smaller than when the pH(A) and the pH(B) in the second aggregation step are such that the value of pH(B)-pH(A) is 0.2 or less or 3.0 or more. <3> According to the invention, there is provided a method for producing a toner for developing electrostatic images, in which the surface exposure rate of the release agent is smaller than when the pH(A) and the pH(B) in the second aggregation step are such that the value of pH(B)-pH(A) is 0.5 or less or 1.5 or more. <4> According to the invention relating to the above, there is provided a method for producing a toner for developing electrostatic images, in which the surface exposure rate of a release agent is smaller than that in the case where the temperature T(A) of the dispersion A and the temperature T(B) of the dispersion B in the second aggregation step satisfy T(A)≦T(B). <5> According to the invention relating to the above, there is provided a method for producing a toner for developing electrostatic images, in which the surface exposure rate of the release agent is smaller than when the temperature T(A) of the dispersion A and the temperature T(B) of the dispersion B in the second aggregation step are such that the value of T(B) - T(A) is -37°C or lower or -13°C or higher. <6> According to the invention relating to the above, there is provided a method for producing a toner for developing electrostatic images, in which the surface exposure rate of the release agent is smaller than when the temperature T(A) of the dispersion A and the temperature T(B) of the dispersion B in the second aggregation step are such that the value of T(B) - T(A) is -30°C or lower or -20°C or higher. <7> According to the invention related to the above, there is provided a method for producing a toner for developing electrostatic images, in which the surface exposure rate of the release agent is smaller than when the pH (B) is less than 3.5 or exceeds 6.0. <8> According to the invention related to the above, there is provided a method for producing a toner for developing electrostatic images, in which the surface exposure rate of the release agent is smaller than when T(B) is less than 15°C or more than 25°C. <9> According to the invention, there is provided a method for producing a toner for developing electrostatic images, in which the surface exposure rate of the release agent is smaller than when the addition rate of the dispersion B in the second aggregation step is less than 0.6 parts by mass per minute or more than 1.2 parts by mass per minute relative to 100 parts by mass of the dispersion A. <10> According to the present invention, there is provided a method for producing a toner for developing electrostatic images, in which the surface exposure rate of the release agent is smaller than that in the case where the resin particles aggregated in the aggregation step are styrene acrylic resin particles. <11> According to the present invention, there is provided a method for producing a toner for developing electrostatic images, in which the surface exposure rate of the release agent is smaller than that in the case where the shell resin particles are styrene acrylic resin particles. <12> According to the invention, there is provided a toner for developing electrostatic images, which includes a first aggregation step of aggregating at least resin particles and release agent particles contained in a dispersion to prepare dispersion A containing first aggregated particles, a second aggregation step of adding dispersion B containing shell resin particles to dispersion A to aggregate the shell resin particles to form second aggregated particles, and a fusion step of heating and fusing the second aggregated particles to form fused particles, wherein the toner has a smaller surface exposure rate of the release agent than when pH(A), which is the pH of dispersion A in the second aggregation step, and pH(B), which is the pH of dispersion B, satisfy pH(A)≧pH(B). [Brief description of the drawings]

[0008] [Figure 1] 1 is a schematic configuration diagram illustrating an example of an image forming apparatus according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a schematic diagram illustrating an example of a process cartridge according to the present embodiment.

Mode for Carrying Out the Invention

[0009] Hereinafter, embodiments which are examples of the present invention will be described in detail. In a numerically defined range described stepwise, an upper limit value or a lower limit value described in a certain numerical range may be replaced with an upper limit value or a lower limit value of a numerically defined range in other stepwise descriptions. Also, in a numerical range, an upper limit value or a lower limit value described in a certain numerical range may be replaced with a value shown in the examples. The amount of each component in the composition means the total amount of the plurality of substances present in the composition when there are a plurality of substances corresponding to each component in the composition, unless otherwise specified. The term "step" includes not only an independent step but also a step in which, even if it cannot be clearly distinguished from other steps, the intended purpose of the step is achieved.

[0010] (Method for Producing Toner for Electrostatic Charge Image Development) The method for producing a toner for electrostatic charge image development according to this embodiment includes a first aggregation step of aggregating at least resin particles and release agent particles contained in a dispersion to produce a dispersion A containing first aggregated particles, a second aggregation step of adding a dispersion B containing resin particles for a shell to the dispersion A and aggregating the resin particles for a shell to form second aggregated particles, and a fusion step of heating and fusing the second aggregated particles to form fused particles, wherein pH(A), which is the pH of the dispersion A in the second aggregation step, and pH(B), which is the pH of the dispersion B, satisfy pH(A) < pH(B). Also, the toner for electrostatic charge image development according to this embodiment is a toner produced by the method for producing a toner for electrostatic charge image development according to this embodiment.

[0011] A release agent is generally used to improve releasability during fixing. Since the releasability is affected by the amount of bleeding of the release agent, it is desirable to dispose the release agent near the surface of the toner particles. However, if there is a large amount of exposure of the release agent on the surface of the toner particles, the external additives are buried due to the agitation stress in the developing machine, and the charge stability is impaired. Therefore, in the method of coating the aggregated particles containing the resin and the release agent with resin particles, if the variation range of the physical properties of the resin particles is large, unevenness occurs in the aggregation action (balance between the aggregation force and the shearing force), resulting in deteriorated coating properties, and there may be a large amount of exposure of the release agent on the surface of the toner particles. In the method for producing an electrostatic charge image developing toner according to the present embodiment, by satisfying pH(A) < pH(B), where pH(A) is the pH of the dispersion liquid A and pH(B) is the pH of the dispersion liquid B in the second aggregation step, even when the variation range of the physical properties of the resin particles is large, the aggregation action by the aggregating agent can be kept substantially constant, and by relaxing the adhesion of the resin particles, the coating property by the shell resin particles can be improved, and it is estimated that the surface exposure rate of the release agent in the toner particles is reduced.

[0012] The method for producing an electrostatic charge image developing toner according to the present embodiment is a method for producing toner particles by the aggregated particle method. Hereinafter, each step will be described in detail.

[0013] <First Aggregation Step> The method for producing an electrostatic charge image developing toner according to the present embodiment includes a first aggregation step of aggregating at least resin particles and release agent particles contained in a dispersion liquid to produce a dispersion liquid A containing first aggregated particles. The dispersion liquid in the first aggregation step contains at least resin particles and release agent particles. Further, if necessary, it may further contain colorant particles or the like. The method for preparing the dispersion liquid is not particularly limited, but it can be preferably prepared by mixing a resin particle dispersion liquid and a release agent particle dispersion liquid. Then, at least the resin particles and the release agent particles are aggregated in the dispersion liquid to produce a dispersion liquid A containing first aggregated particles.

[0014] Specifically, the aggregation is performed by, for example, adding an aggregating agent to the dispersion liquid, adjusting the pH of the dispersion liquid to be acidic (e.g., pH 2 or more and 5 or less), adding a dispersion stabilizer as necessary, and then heating to a temperature corresponding to the glass transition temperature of the resin particles (specifically, for example, glass transition temperature of the resin particles -30°C or more and glass transition temperature -10°C or less), thereby aggregating the particles dispersed in the dispersion liquid to form first aggregated particles. In the first aggregation step, for example, the dispersion may be stirred with a rotary shear homogenizer, the aggregating agent may be added at room temperature (e.g., 25°C), the pH of the dispersion may be adjusted to an acidic state (e.g., a pH of 2 or more and 5 or less), and a dispersion stabilizer may be added as necessary, followed by the heating.

[0015] Examples of the flocculant include a surfactant having a polarity opposite to that of the surfactant used as the dispersant added to the mixed dispersion, an inorganic metal salt, and a divalent or higher metal complex. In particular, when a metal complex is used as the flocculant, the amount of surfactant used is reduced and the charging characteristics are improved. If necessary, an additive that forms a complex or a similar bond with the metal ions of the flocculant may be used, and a chelating agent is preferably used as this additive.

[0016] Examples of inorganic metal salts include metal salts such as calcium chloride, calcium nitrate, barium chloride, magnesium chloride, zinc chloride, aluminum chloride, and aluminum sulfate, as well as inorganic metal salt polymers such as polyaluminum chloride, polyaluminum hydroxide, and calcium polysulfide. Among them, it is preferable to use an aluminum compound as the flocculant. The chelating agent may be a water-soluble chelating agent, such as oxycarboxylic acid (e.g., tartaric acid, citric acid, gluconic acid, etc.), iminodiacetic acid (IDA), nitrilotriacetic acid (NTA), ethylenediaminetetraacetic acid (EDTA), etc. The amount of the chelating agent added is, for example, preferably 0.01 parts by mass or more and 5.0 parts by mass or less, and more preferably 0.1 parts by mass or more and less than 3.0 parts by mass, relative to 100 parts by mass of the resin particles.

[0017] The dispersion liquid and the dispersion liquid A in the first aggregation step are preferably aqueous dispersion liquids, and more preferably aqueous dispersion liquids. Examples of the dispersion medium used in the dispersion liquid and the dispersion liquid A in the first aggregation step include an aqueous medium. Examples of the aqueous medium include water such as distilled water and ion-exchanged water, alcohols, etc. These may be used alone or in combination of two or more kinds.

[0018] The dispersion liquid in the first aggregation step preferably contains a surfactant. Examples of the surfactant include anionic surfactants such as sulfate salts, sulfonates, phosphates, and soaps; cationic surfactants such as amine salts and quaternary ammonium salts; and nonionic surfactants such as polyethylene glycols, alkylphenol ethylene oxide adducts, and polyhydric alcohols. Among these, anionic surfactants and cationic surfactants are particularly preferred. The nonionic surfactants may be used in combination with anionic surfactants or cationic surfactants. The surfactant may be used alone or in combination of two or more kinds.

[0019] The volume average particle size of the resin particles before aggregation dispersed in the dispersion liquid is preferably from 0.01 μm to 1 μm, more preferably from 0.08 μm to 0.8 μm, and even more preferably from 0.1 μm to 0.6 μm. The volume average particle size of the release agent particles before aggregation dispersed in the dispersion liquid is preferably from 0.01 μm to 1 μm, more preferably from 0.08 μm to 0.8 μm, and even more preferably from 0.1 μm to 0.6 μm. The volume average particle size of the resin particles and the release agent particles is measured by using a particle size distribution obtained by measurement with a laser diffraction particle size distribution measuring device (for example, LA-700 manufactured by Horiba, Ltd.), subtracting the cumulative distribution from the small particle size side for the volume of the divided particle size range (channel), and measuring the particle size at which the cumulative distribution is 50% of all particles as the volume average particle size D50v. The volume average particle sizes of particles in other dispersions are also measured in the same manner.

[0020] The resin particles in the first aggregation step preferably contain polyester resin particles, and more preferably are polyester resin particles, from the viewpoints of suppressing surface exposure of the release agent, heat storage stability, and image density stability. The resin particles in the first aggregation step preferably contain amorphous resin particles, and more preferably contain amorphous resin particles and crystalline resin particles. As described above, the dispersion liquid may further contain colorant particles to be used in the toner particles. The preferred volume average particle size of the colorant particles is the same as the preferred volume average particle size of the resin particles.

[0021] In the first aggregation step, the solid content concentration of the dispersion liquid is preferably 5% by mass or more and 30% by mass or less, more preferably 8% by mass or more and 25% by mass or less, and particularly preferably 11% by mass or more and 20% by mass or less, from the viewpoint of dispersibility of resin particles, release agent particles, etc.

[0022] The volume average particle size of the aggregated particles obtained in the aggregation step is not particularly limited, and can be appropriately selected depending on the volume average particle size of the desired toner particles.

[0023] The preferred embodiments of each of the components contained in the toner particles, such as the binder resin, the release agent, and the colorant, will be described below.

[0024] <Second aggregation process> The method for manufacturing a toner for electrostatic charge image development according to this embodiment includes a second aggregation step of adding a dispersion liquid B containing resin particles for a shell to the dispersion liquid A and aggregating the resin particles for a shell to form second aggregated particles, and pH(A), which is the pH of the dispersion liquid A in the second aggregation step, and pH(B), which is the pH of the dispersion liquid B, satisfy pH(A) < pH(B).

[0025] In the second aggregation step, a dispersion liquid A containing first aggregated particles and a dispersion liquid of resin particles for a shell are mixed. Then, resin particles for a shell are aggregated on the surface of the first aggregated particles to form second aggregated particles.

[0026] Specifically, in the second aggregation step, for example, after adding a dispersion stabilizer as necessary, heating is performed to a temperature equal to or lower than the glass transition temperature of the resin particles for a shell (specifically, for example, the glass transition temperature of the resin particles for a shell), and the resin particles for a shell are aggregated on the surface of the first aggregated particles to form second aggregated particles. Then, the pH of the dispersion liquid containing the second aggregated particles is adjusted to stop the progress of aggregation. In the second aggregation step, for example, after adding a dispersion stabilizer as necessary while stirring the dispersion liquid A with a rotary shear homogenizer at room temperature (for example, 25°C), the heating may be performed. In addition, a flocculant may be added in the second aggregation step, but from the viewpoint of aggregation uniformity, it is preferably not added.

[0027] pH(A), which is the pH of the dispersion liquid A in the second aggregation step, and pH(B), which is the pH of the dispersion liquid B, satisfy pH(A) < pH(B). In addition, pH(A) and pH(B) in the second aggregation step preferably satisfy 0.2 < pH(B) - pH(A) < 3.0, and more preferably satisfy 0.5 < pH(B) - pH(A) < 1.5, from the viewpoints of suppressing surface exposure of the mold release agent, heat storage stability, and image density stability.

[0028] The pH(A) in the second aggregation step is preferably 1.5 or more and 4.5 or less, more preferably 2.0 or more and 3.5 or less, and particularly preferably 2.5 or more and 3.5 or less, from the viewpoints of aggregability, suppression of surface exposure of the release agent, heat storage stability, and image density stability. The pH(B) in the second aggregation step is preferably 3.0 or more and 7.0 or less, more preferably 3.5 or more and 6.0 or less, and particularly preferably 3.7 or more and 5.5 or less, from the viewpoints of aggregability, suppression of surface exposure of the release agent, heat storage stability, and image density stability.

[0029] The temperature T(A) of the dispersion A and the temperature T(B) of the dispersion B in the second aggregation step preferably satisfy T(A)>T(B), more preferably satisfy -37°C < T(B) - T(A) < -13°C, and particularly preferably satisfy -30°C < T(B) - T(A) < -20°C, from the viewpoints of aggregation uniformity, suppression of surface exposure of the release agent, heat storage stability, and image density stability.

[0030] The T(A) in the second aggregation step is preferably 30°C or more and 65°C or less, more preferably 35°C or more and 60°C or less, and particularly preferably 40°C or more and 55°C or less, from the viewpoints of aggregation uniformity, suppression of surface exposure of the release agent, heat storage stability, and image density stability. The T(B) in the second aggregation step is preferably 5°C or more and 35°C or less, more preferably 10°C or more and 30°C or less, and particularly preferably 15°C or more and 25°C or less, from the viewpoints of aggregation uniformity, suppression of surface exposure of the release agent, heat storage stability, and image density stability.

[0031] The value of the mass ratio (M(A) / M(B)) of the mass M(A) of the first aggregation particles and the mass M(B) of the resin particles for the shell used in the second aggregation step is preferably 2 or more and 10 or less, more preferably 2.5 or more and 8 or less, and particularly preferably 3 or more and 5 or less, from the viewpoints of suppression of surface exposure of the release agent, heat storage stability, and image density stability.

[0032] In the second aggregation step, the addition rate of the dispersion B containing the shell resin particles is preferably from 0.6 parts by mass or more to 1.2 parts by mass or less per minute, and more preferably from 0.7 parts by mass or more to 1.0 parts by mass or less per minute, relative to 100 parts by mass of the dispersion A, from the viewpoints of aggregation uniformity, suppression of surface exposure of the release agent, thermal storage property, and image density stability.

[0033] Furthermore, the stirring speed of the dispersion in the first aggregation step and the stirring speed of the dispersion A in the second aggregation step are not particularly limited and may be the same or different. However, from the viewpoints of aggregation uniformity, suppression of surface exposure of the release agent, thermal storage property, and image density stability, it is preferable that the stirring speed of the dispersion A in the second aggregation step is slower than the stirring speed of the dispersion in the first aggregation step. Furthermore, from the viewpoints of aggregation uniformity, suppression of surface exposure of the release agent, thermal storage property, and image density stability, it is preferable that the aggregation in the first aggregation step and the aggregation in the second aggregation step are performed in the same stirring device, and it is more preferable that the aggregation in the first aggregation step, the aggregation in the second aggregation step, and the fusion in the fusion step are performed in the same stirring device.

[0034] The shell resin particles in the second aggregation step preferably contain polyester resin particles, and more preferably are polyester resin particles, from the viewpoints of suppressing surface exposure of the release agent, heat storage property, and image density stability. The dispersion B in the second aggregation step is preferably an aqueous dispersion, and more preferably an aqueous dispersion.

[0035] <Fusion process> The method for producing the toner for developing electrostatic images according to this embodiment includes a fusing step of heating and fusing the second aggregate particles to form fused particles. In the fusion process, the dispersion liquid in which the second aggregated particles are dispersed is heated, for example, to a temperature equal to or higher than the glass transition temperature of the resin particles and the shell resin particles (for example, a temperature 30° C. to 50° C. higher than the glass transition temperature of the resin particles and the shell resin particles) and equal to or higher than the melting temperature of the release agent, to fuse and coalesce the second aggregated particles and form toner particles. In the fusion step, the resin and the release agent are in a fused state at a temperature equal to or higher than the glass transition temperature of the resin particles and the shell resin particles and equal to or higher than the melting temperature of the release agent.

[0036] Through the above steps, core-shell toner particles are obtained.

[0037] After the fusion step, the toner particles formed in the solution are subjected to a known washing step, a solid-liquid separation step, and a drying step to obtain toner particles in a dry state. In the washing step, it is preferable to carry out sufficient replacement washing with ion-exchanged water from the viewpoint of electrostatic charge. In addition, the solid-liquid separation step is not particularly limited, but it is preferable to carry out suction filtration, pressure filtration, etc. from the viewpoint of productivity. In addition, in the drying step, there is no particular limit to the method, but it is preferable to carry out freeze drying, air flow drying, fluidized drying, vibration type fluidized drying, etc. from the viewpoint of productivity.

[0038] The method for producing the toner for developing electrostatic images according to the present embodiment preferably includes a step of externally adding an external additive to the obtained toner particles. The external addition may be carried out, for example, by using a V blender, a Henschel mixer, a Loedige mixer, etc. Furthermore, if necessary, coarse particles of the toner may be removed using a vibration sifter, a wind sifter, etc.

[0039] <Resin particle dispersion preparation process> The method for producing the toner for developing electrostatic images according to the present embodiment preferably includes a resin particle dispersion preparation step of preparing a resin particle dispersion. In addition to the resin particle dispersion liquid in which the resin particles are dispersed, for example, the method for producing the toner for developing electrostatic images according to the present embodiment preferably includes a step of preparing a colorant particle dispersion liquid in which colorant particles are dispersed, and a step of preparing a release agent particle dispersion liquid in which release agent particles are dispersed.

[0040] The resin particle dispersion liquid is prepared, for example, by dispersing resin particles in a dispersion medium with the aid of a surfactant.

[0041] The dispersion medium used in the resin particle dispersion liquid is, for example, an aqueous medium. Examples of the aqueous medium include water such as distilled water and ion-exchanged water, alcohols, etc. These may be used alone or in combination of two or more kinds.

[0042] Examples of the surfactant include anionic surfactants such as sulfate salts, sulfonates, phosphates, and soaps; cationic surfactants such as amine salts and quaternary ammonium salts; and nonionic surfactants such as polyethylene glycols, alkylphenol ethylene oxide adducts, and polyhydric alcohols. Among these, anionic surfactants and cationic surfactants are particularly preferred. The nonionic surfactants may be used in combination with anionic surfactants or cationic surfactants. The surfactant may be used alone or in combination of two or more kinds.

[0043] In the resin particle dispersion, the resin particles are dispersed in the dispersion medium by a general dispersion method such as a rotary shear type homogenizer, a ball mill having a media, a sand mill, or a dyno mill. Depending on the type of resin particles, the resin particles may be dispersed in the dispersion medium by a phase inversion emulsification method. The phase inversion emulsification method is a method in which the resin to be dispersed is dissolved in a hydrophobic organic solvent in which the resin is soluble, a base is added to the organic continuous phase (O phase) to neutralize it, and then an aqueous medium (W phase) is added to invert the phase from W / O to O / W, thereby dispersing the resin in the aqueous medium in the form of particles.

[0044] The volume average particle size of the resin particles dispersed in the resin particle dispersion is, for example, preferably from 0.01 μm to 1 μm, more preferably from 0.08 μm to 0.8 μm, and even more preferably from 0.1 μm to 0.6 μm.

[0045] The content of the resin particles in the resin particle dispersion is preferably from 5% by mass to 50% by mass, and more preferably from 10% by mass to 40% by mass.

[0046] In the same manner as the resin particle dispersion liquid, for example, a colorant particle dispersion liquid and a release agent particle dispersion liquid are also prepared. That is, the volume average particle size, dispersion medium, dispersion method, and particle content of the particles in the resin particle dispersion liquid are the same for the colorant particles dispersed in the colorant particle dispersion liquid and the release agent particles dispersed in the release agent particle dispersion liquid.

[0047] The method for producing the toner for developing electrostatic images according to the present embodiment may include known steps other than those described above.

[0048] Each component contained in the toner for developing an electrostatic image will be described in detail below. The toner particles preferably contain a binder resin, a release agent, and, if necessary, other components, and more preferably contain a binder resin, a release agent, and a colorant.

[0049] <Binding resin> The binder resin preferably contains an amorphous resin, and more preferably contains an amorphous resin and a crystalline resin from the viewpoints of image strength and suppression of density unevenness in the obtained image. That is, in the first aggregation step, it is more preferable that the resin particles contain an amorphous resin particle and a crystalline resin particle.

[0050] Here, the term "amorphous resin" refers to a resin that, in a thermal analysis measurement using differential scanning calorimetry (DSC), has only a stepwise endothermic change rather than a clear endothermic peak, is a solid at room temperature, and is thermoplasticized at a temperature equal to or higher than the glass transition temperature. On the other hand, a crystalline resin refers to a resin that has a clear endothermic peak rather than a stepwise change in endothermic amount in differential scanning calorimetry (DSC). Specifically, for example, a crystalline resin means a resin whose half-width of an endothermic peak is within 10°C when measured at a heating rate of 10°C / min, and an amorphous resin means a resin whose half-width exceeds 10°C or a resin in which no clear endothermic peak is observed.

[0051] The amorphous resin will be described. Examples of the amorphous resin include known amorphous resins such as amorphous polyester resin, amorphous vinyl resin (e.g., styrene acrylic resin, etc.), epoxy resin, polycarbonate resin, polyurethane resin, etc. Among these, from the viewpoint of suppressing uneven density and suppressing white spots in the obtained image, amorphous polyester resin and amorphous vinyl resin (particularly styrene acrylic resin) are preferred, and amorphous polyester resin is more preferred. In addition, it is also a preferred embodiment to use an amorphous polyester resin and a styrene-acrylic resin in combination as the amorphous resin.

[0052] The amorphous polyester resin may be, for example, a condensation polymer of a polyvalent carboxylic acid and a polyhydric alcohol. As the amorphous polyester resin, a commercially available product or a synthesized product may be used.

[0053] Examples of polyvalent carboxylic acids include aliphatic dicarboxylic acids (e.g., oxalic acid, malonic acid, maleic acid, fumaric acid, citraconic acid, itaconic acid, glutaconic acid, succinic acid, alkenylsuccinic acid, adipic acid, sebacic acid, etc.), alicyclic dicarboxylic acids (e.g., cyclohexanedicarboxylic acid, etc.), aromatic dicarboxylic acids (e.g., terephthalic acid, isophthalic acid, phthalic acid, naphthalenedicarboxylic acid, etc.), anhydrides thereof, and lower alkyl esters thereof (e.g., having 1 to 5 carbon atoms). Among these, aromatic dicarboxylic acids are preferred as the polyvalent carboxylic acid. The polyvalent carboxylic acid may be a trivalent or higher carboxylic acid having a crosslinked or branched structure in combination with a dicarboxylic acid. Examples of the trivalent or higher carboxylic acid include trimellitic acid, pyromellitic acid, anhydrides thereof, and lower (e.g., carbon number 1 to 5) alkyl esters thereof. The polyvalent carboxylic acids may be used alone or in combination of two or more kinds.

[0054] Examples of polyhydric alcohols include aliphatic diols (e.g., ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, butanediol, hexanediol, neopentyl glycol, etc.), alicyclic diols (e.g., cyclohexanediol, cyclohexanedimethanol, hydrogenated bisphenol A, etc.), and aromatic diols (e.g., ethylene oxide adducts of bisphenol A, propylene oxide adducts of bisphenol A, etc.). Among these, aromatic diols and alicyclic diols are preferred as polyhydric alcohols, and aromatic diols are more preferred. As the polyhydric alcohol, a polyhydric alcohol having a crosslinked or branched structure of three or more may be used in combination with the diol. Examples of the polyhydric alcohol having a trihydric or higher valence include glycerin, trimethylolpropane, and pentaerythritol. The polyhydric alcohols may be used alone or in combination of two or more kinds.

[0055] The amorphous polyester resin is obtained by a known manufacturing method. Specifically, for example, the polymerization temperature is set to 180°C or more and 230°C or less, the reaction system is depressurized as necessary, and the reaction is carried out while removing water and alcohol generated during condensation. If the raw material monomer is not dissolved or compatible at the reaction temperature, a high-boiling point solvent may be added as a dissolution aid to dissolve it. In this case, the polycondensation reaction is carried out while distilling off the dissolution aid. If a monomer with poor compatibility is present in the copolymerization reaction, it is recommended that the monomer with poor compatibility is condensed in advance with the acid or alcohol to be polycondensed with the monomer and then polycondensed with the main component.

[0056] As the binder resin, particularly the amorphous resin, a styrene-acrylic resin can be mentioned. The styrene-acrylic resin is a copolymer obtained by copolymerizing at least a styrene-based monomer (a monomer having a styrene skeleton) and a (meth)acrylic-based monomer (a monomer having a (meth)acrylic group, preferably a monomer having a (meth)acryloxy group). The styrene-acrylic resin includes, for example, a copolymer of a styrene monomer and a (meth)acrylic acid ester monomer. The acrylic resin portion of the styrene-acrylic resin is a partial structure formed by polymerizing either an acrylic monomer or a methacrylic monomer, or both. In addition, the term "(meth)acrylic" includes both "acrylic" and "methacrylic".

[0057] Specific examples of styrene-based monomers include styrene, alkyl-substituted styrenes (e.g., α-methylstyrene, 2-methylstyrene, 3-methylstyrene, 4-methylstyrene, 2-ethylstyrene, 3-ethylstyrene, 4-ethylstyrene, etc.), halogen-substituted styrenes (e.g., 2-chlorostyrene, 3-chlorostyrene, 4-chlorostyrene, etc.), vinylnaphthalene, etc. The styrene-based monomers may be used alone or in combination of two or more. Of these, as the styrene-based monomer, styrene is preferred from the viewpoints of ease of reaction, ease of reaction control, and availability.

[0058] Specific examples of the (meth)acrylic monomer include (meth)acrylic acid and (meth)acrylic acid esters. Examples of the (meth)acrylic acid esters include (meth)acrylic acid alkyl esters (e.g., methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, n-butyl (meth)acrylate, n-pentyl (meth)acrylate, n-hexyl acrylate, n-heptyl (meth)acrylate, n-octyl (meth)acrylate, n-decyl (meth)acrylate, n-dodecyl (meth)acrylate, n-lauryl (meth)acrylate, n-tetradecyl (meth)acrylate, n-hexadecyl (meth)acrylate, n-octadecyl (meth)acrylate, isopropyl (meth)acrylate, isobutyl (meth)acrylate, t-butyl (meth)acrylate, isopentyl (meth)acrylate, amyl (meth)acrylate, and (meth) Examples of the (meth)acrylic acid monomer include neopentyl acrylate, isohexyl (meth)acrylate, isoheptyl (meth)acrylate, isooctyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, cyclohexyl (meth)acrylate, t-butylcyclohexyl (meth)acrylate, etc.), aryl (meth)acrylate esters (e.g., phenyl (meth)acrylate, biphenyl (meth)acrylate, diphenylethyl (meth)acrylate, t-butylphenyl (meth)acrylate, terphenyl (meth)acrylate, etc.), dimethylaminoethyl (meth)acrylate, diethylaminoethyl (meth)acrylate, methoxyethyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, β-carboxyethyl (meth)acrylate, and (meth)acrylamide. The (meth)acrylic acid monomer may be used alone or in combination of two or more. Among these (meth)acrylic esters among the (meth)acrylic monomers, from the viewpoint of fixation, (meth)acrylic acid esters having an alkyl group having 2 to 14 carbon atoms (preferably 2 to 10 carbon atoms, more preferably 3 to 8 carbon atoms) are preferred. Of these, n-butyl (meth)acrylate is preferred, and n-butyl acrylate is particularly preferred.

[0059] The copolymerization ratio of the styrene monomer to the (meth)acrylic monomer (mass basis, styrene monomer / (meth)acrylic monomer) is not particularly limited, but is preferably 85 / 15 to 70 / 30.

[0060] The styrene-acrylic resin may have a crosslinked structure. A preferred example of the styrene-acrylic resin having a crosslinked structure is a copolymer of at least a styrene-based monomer, a (meth)acrylic acid-based monomer, and a crosslinkable monomer.

[0061] The crosslinkable monomer may, for example, be a bifunctional or higher functional crosslinking agent. Examples of bifunctional crosslinking agents include divinylbenzene, divinylnaphthalene, di(meth)acrylate compounds (e.g., diethylene glycol di(meth)acrylate, methylene bis(meth)acrylamide, decanediol diacrylate, glycidyl (meth)acrylate, etc.), polyester type di(meth)acrylate, 2-([1'-methylpropylideneamino]carboxyamino)ethyl methacrylate, etc. Examples of polyfunctional crosslinking agents include tri(meth)acrylate compounds (e.g., pentaerythritol tri(meth)acrylate, trimethylolethane tri(meth)acrylate, trimethylolpropane tri(meth)acrylate, etc.), tetra(meth)acrylate compounds (e.g., pentaerythritol tetra(meth)acrylate, oligoester (meth)acrylate, etc.), 2,2-bis(4-methacryloxy, polyethoxyphenyl)propane, diallyl phthalate, triallyl cyanurate, triallyl isocyanurate, triallyl trimellitate, diaryl chlorendate, etc. Among these, as the crosslinkable monomer, from the viewpoints of suppressing the occurrence of a decrease in image density and suppressing the occurrence of uneven image density, and of fixability, a bifunctional or higher (meth)acrylate compound is preferred, a bifunctional (meth)acrylate compound is more preferred, a bifunctional (meth)acrylate compound having an alkylene group having 6 to 20 carbon atoms is even more preferred, and a bifunctional (meth)acrylate compound having a linear alkylene group having 6 to 20 carbon atoms is particularly preferred.

[0062] The copolymerization ratio of the crosslinkable monomer to the total monomers (mass basis, crosslinkable monomer / total monomers) is not particularly limited, but is preferably 2 / 1,000 to 20 / 1,000.

[0063] The method for producing the styrene-acrylic resin is not particularly limited, and various polymerization methods (e.g., solution polymerization, precipitation polymerization, suspension polymerization, bulk polymerization, emulsion polymerization, etc.) are applied. In addition, the polymerization reaction is carried out by a known operation (e.g., batchwise, semi-continuous, continuous, etc.).

[0064] The proportion of the styrene-acrylic resin in the total binder resin is preferably from 0% to 20% by mass, more preferably from 1% to 15% by mass, and even more preferably from 2% to 10% by mass.

[0065] The proportion of the amorphous resin in the total binder resin is preferably 60% by mass or more and 98% by mass or less, more preferably 65% ​​by mass or more and 95% by mass or less, and even more preferably 70% by mass or more and 90% by mass or less.

[0066] The characteristics of the amorphous resin will be described. The glass transition temperature (Tg) of the amorphous 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 determined from a DSC curve obtained by differential scanning calorimetry (DSC), more specifically, from the "extrapolated glass transition onset temperature" described in the method for determining glass transition temperature in JIS K 7121-1987 "Method for measuring transition temperature of plastics."

[0067] The weight average molecular weight (Mw) of the amorphous 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 amorphous resin is preferably 2,000 or more and 100,000 or less. The molecular weight distribution Mw / Mn of the amorphous resin is preferably 1.5 or more and 100 or less, and more preferably 2 or more and 60 or less. The weight average molecular weight and number average molecular weight are measured by gel permeation chromatography (GPC). The molecular weight measurement by GPC is performed using a Tosoh GPC HLC-8120GPC as the measuring device, a Tosoh TSKgel SuperHM-M (15 cm) column, and THF solvent. The weight average molecular weight and number average molecular weight are calculated from the measurement results using a molecular weight calibration curve created with a monodisperse polystyrene standard sample.

[0068] The crystalline resin will now be described. Examples of the crystalline resin include known crystalline resins such as crystalline polyester resins and crystalline vinyl resins (e.g., polyalkylene resins, long-chain alkyl (meth)acrylate resins, etc.). Among these, crystalline polyester resins are preferred from the viewpoint of suppressing uneven density and white spots in the resulting image.

[0069] The crystalline polyester resin may be, for example, a polycondensate of a polyvalent carboxylic acid and a polyhydric alcohol. As the crystalline polyester resin, a commercially available product or a synthesized product may be used. Since the crystalline polyester resin easily forms a crystalline structure, a polycondensation product using a straight-chain aliphatic polymerizable monomer is preferable to a polymerizable monomer having an aromatic ring.

[0070] Examples of polyvalent carboxylic acids include aliphatic dicarboxylic acids (e.g., oxalic acid, succinic acid, glutaric acid, adipic acid, suberic acid, azelaic acid, sebacic acid, 1,9-nonanedicarboxylic acid, 1,10-decanedicarboxylic acid, 1,12-dodecanedicarboxylic acid, 1,14-tetradecanedicarboxylic acid, 1,18-octadecanedicarboxylic acid, etc.), aromatic dicarboxylic acids (e.g., dibasic acids such as phthalic acid, isophthalic acid, terephthalic acid, naphthalene-2,6-dicarboxylic acid, etc.), anhydrides thereof, and lower alkyl esters thereof (e.g., having 1 to 5 carbon atoms). The polyvalent carboxylic acid may be a trivalent or higher carboxylic acid having a crosslinked or branched structure in combination with a dicarboxylic acid. Examples of the trivalent carboxylic acid include aromatic carboxylic acids (e.g., 1,2,3-benzenetricarboxylic acid, 1,2,4-benzenetricarboxylic acid, 1,2,4-naphthalenetricarboxylic acid, etc.), their anhydrides, and their lower (e.g., carbon number 1 to 5) alkyl esters. As the polyvalent carboxylic acid, a dicarboxylic acid having a sulfonic acid group and a dicarboxylic acid having an ethylenic double bond may be used in combination with these dicarboxylic acids. The polyvalent carboxylic acids may be used alone or in combination of two or more kinds.

[0071] Examples of polyhydric alcohols include aliphatic diols (for example, straight-chain aliphatic diols having 7 to 20 carbon atoms in the main chain). Examples of aliphatic diols include ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 1,11-undecanediol, 1,12-dodecanediol, 1,13-tridecanediol, 1,14-tetradecanediol, 1,18-octadecanediol, and 1,14-eicosanedecanediol. Among these, 1,8-octanediol, 1,9-nonanediol, and 1,10-decanediol are preferred as aliphatic diols. The polyhydric alcohol may be a trihydric or higher alcohol having a crosslinked or branched structure in combination with the diol. Examples of the trihydric or higher alcohol include glycerin, trimethylolethane, trimethylolpropane, and pentaerythritol. The polyhydric alcohols may be used alone or in combination of two or more kinds.

[0072] The polyhydric alcohol may have an aliphatic diol content of 80 mol % or more, and preferably 90 mol % or more.

[0073] The melting temperature of the crystalline polyester resin is preferably 50°C or higher and 100°C or lower, more preferably 55°C or higher and 90°C or lower, and even more preferably 60°C or higher and 85°C or lower. The melting temperature of the crystalline polyester resin is determined from a DSC curve obtained by differential scanning calorimetry (DSC) based on the "melting peak temperature" described in the method for determining melting temperature in JIS K7121:1987 "Method for measuring transition temperature of plastics."

[0074] The weight average molecular weight (Mw) of the crystalline polyester resin is preferably 6,000 or more and 35,000 or less.

[0075] The crystalline polyester resin can be obtained, for example, by a known production method, like the amorphous polyester resin.

[0076] As the crystalline polyester resin, a polymer of an α,ω-linear aliphatic dicarboxylic acid and an α,ω-linear aliphatic diol is preferred from the viewpoint of easily forming a crystal structure and having good compatibility with the amorphous polyester resin, thereby improving the fixability of the image.

[0077] The α,ω-linear aliphatic dicarboxylic acid is preferably an α,ω-linear aliphatic dicarboxylic acid in which the alkylene group connecting the two carboxy groups has 3 or more and 14 or less carbon atoms, more preferably the alkylene group has 4 or more and 12 or less carbon atoms, and even more preferably the alkylene group has 6 or more and 10 or less carbon atoms. Examples of α,ω-linear aliphatic dicarboxylic acids include succinic acid, glutaric acid, adipic acid, 1,6-hexanedicarboxylic acid (commonly known as suberic acid), 1,7-heptanedicarboxylic acid (commonly known as azelaic acid), 1,8-octanedicarboxylic acid (commonly known as sebacic acid), 1,9-nonanedicarboxylic acid, 1,10-decanedicarboxylic acid, 1,12-dodecanedicarboxylic acid, 1,14-tetradecanedicarboxylic acid, and 1,18-octadecanedicarboxylic acid. Of these, 1,6-hexanedicarboxylic acid, 1,7-heptanedicarboxylic acid, 1,8-octanedicarboxylic acid, and 1,10-decanedicarboxylic acid are preferred. The α,ω-linear aliphatic dicarboxylic acids may be used alone or in combination of two or more kinds.

[0078] The α,ω-linear aliphatic diol is preferably an α,ω-linear aliphatic diol in which the alkylene group connecting the two hydroxy groups has 3 to 14 carbon atoms, more preferably the alkylene group has 4 to 12 carbon atoms, and further preferably the alkylene group has 6 to 10 carbon atoms. Examples of the α,ω-linear aliphatic diol include ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 1,12-dodecanediol, 1,14-tetradecanediol, and 1,18-octadecanediol. Of these, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, and 1,10-decanediol are preferred. The α,ω-linear aliphatic diols may be used alone or in combination of two or more kinds.

[0079] As the polymer of an α,ω-linear aliphatic dicarboxylic acid and an α,ω-linear aliphatic diol, from the viewpoint of easily forming a crystal structure and having good compatibility with an amorphous polyester resin, thereby improving the fixability of an image, a polymer of at least one selected from the group consisting of 1,6-hexanedicarboxylic acid, 1,7-heptanedicarboxylic acid, 1,8-octanedicarboxylic acid, 1,9-nonanedicarboxylic acid, and 1,10-decanedicarboxylic acid and at least one selected from the group consisting of 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, and 1,10-decanediol is preferred, and among these, a polymer of 1,10-decanedicarboxylic acid and 1,6-hexanediol is more preferred.

[0080] The proportion of the crystalline resin in the total binder resin is preferably from 1% by mass to 20% by mass, more preferably from 2% by mass to 15% by mass, and even more preferably from 3% by mass to 10% by mass.

[0081] Other binder resins Examples of the binder resin include homopolymers of monomers such as ethylenically unsaturated nitriles (e.g., acrylonitrile, methacrylonitrile, etc.), vinyl ethers (e.g., vinyl methyl ether, vinyl isobutyl ether, etc.), vinyl ketones (e.g., vinyl methyl ketone, vinyl ethyl ketone, vinyl isopropenyl ketone, etc.) and olefins (e.g., ethylene, propylene, butadiene, etc.), and copolymers of two or more of these monomers. Other examples of the binder resin include non-vinyl resins such as epoxy resins, polyurethane resins, polyamide resins, cellulose resins, polyether resins, and modified rosin, mixtures of these with the vinyl resins, and graft polymers obtained by polymerizing vinyl monomers in the coexistence of these. These binder resins may be used alone or in combination of two or more kinds.

[0082] The content of the binder resin is preferably from 40% by mass to 95% by mass, more preferably from 50% by mass to 90% by mass, and even more preferably from 60% by mass to 85% by mass, based on the total mass of the toner particles.

[0083] -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, and ester waxes such as fatty acid esters and montan acid esters. The release agent is not limited to these.

[0084] As the release agent, from the viewpoints of suppressing uneven density and white voids in the obtained image and having good compatibility with the amorphous polyester resin, thereby improving the fixability of the image, an ester wax is preferred, and an ester wax of a higher fatty acid having from 10 to 30 carbon atoms and a monovalent or polyvalent alcohol component having from 1 to 30 carbon atoms is more preferred.

[0085] The ester wax is a wax having an ester bond. The ester wax may be any of a monoester, diester, triester, and tetraester, and any known natural or synthetic ester wax can be used. Examples of ester waxes include ester compounds of higher fatty acids (such as fatty acids having 10 or more carbon atoms) and monohydric or polyhydric aliphatic alcohols (such as aliphatic alcohols having 8 or more carbon atoms), and have a melting temperature of 60°C or higher and 110°C or lower (preferably 65°C or higher and 100°C or lower, more preferably 70°C or higher and 95°C or lower). Examples of ester waxes include ester compounds of higher fatty acids (caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, arachidic acid, behenic acid, oleic acid, etc.) and alcohols (monohydric alcohols such as methanol, ethanol, propanol, isopropanol, butanol, capryl alcohol, lauryl alcohol, myristyl alcohol, cetyl alcohol, stearyl alcohol, oleyl alcohol, etc.; polyhydric alcohols such as glycerin, ethylene glycol, propylene glycol, sorbitol, pentaerythritol, etc.). Specific examples include carnauba wax, rice wax, candelilla wax, jojoba oil, Japan wax, beeswax, privet wax, lanolin, and montanic acid ester wax.

[0086] 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 of the release agent is determined from a DSC curve obtained by differential scanning calorimetry (DSC) based on the "melting peak temperature" described in the method for determining melting temperature in JIS K7121:1987 "Method for measuring transition temperature of plastics."

[0087] The content of the release agent is preferably from 1% by mass to 20% by mass, and more preferably from 5% by mass to 15% by mass, based on the total mass of the toner particles.

[0088] -Coloring agent- In the first aggregation step, the dispersion liquid preferably further contains colorant particles. Examples of colorants include carbon black, chrome yellow, Hansa Yellow, benzidine yellow, threne yellow, quinoline yellow, pigment yellow, permanent orange GTR, pyrazolone orange, Balkan orange, watch young red, permanent red, brilliant carmine 3B, brilliant carmine 6B, DuPont oil red, pyrazolone red, lithol red, rhodamine B lake, lake red C, pigment red, rose bengal, aniline blue, ultramarine blue, and tetrahydrofuran. Examples of the dyes include various pigments such as phosphorus blue, chalcoil blue, methylene blue chloride, phthalocyanine blue, pigment blue, phthalocyanine green, and malachite green oxalate, and various dyes such as acridine-based, xanthene-based, azo-based, benzoquinone-based, azine-based, anthraquinone-based, thioindigo-based, dioxazine-based, thiazine-based, azomethine-based, indigo-based, phthalocyanine-based, aniline black-based, polymethine-based, triphenylmethane-based, diphenylmethane-based, and thiazole-based dyes. The colorant may be used alone or in combination of two or more kinds.

[0089] The colorant may be surface-treated as necessary, or may be used in combination with a dispersant. In addition, a plurality of types of colorants may be used in combination.

[0090] The content of the colorant is, for example, preferably from 1% by mass to 30% by mass, and more preferably from 3% by mass to 15% by mass, based on the total mass of the toner particles.

[0091] -Other additives- Examples of other additives include well-known additives such as magnetic materials, charge control agents, inorganic powders, etc. These additives are contained in the toner particles as internal additives.

[0092] -Characteristics of toner particles, etc.- The toner particles may be toner particles having a single layer structure, or may be toner particles having a so-called core-shell structure (core-shell type particles) composed of a core (core particle) and a coating layer (shell layer) that coats the core. The toner particles having a core-shell structure are composed of, for example, a core containing a binder resin and, if necessary, a colorant and a release agent, and the like, and a coating layer containing a binder resin. Among these, the toner particles are preferably core-shell type particles from the viewpoints of low-temperature fixability and suppression of color streaks.

[0093] Toner volume average particle size (D 50v ) is preferably from 2 μm to 10 μm, and more preferably from 4 μm to 8 μm.

[0094] The volume average particle size of the toner is measured using a Coulter Multisizer II (manufactured by Beckman Coulter, Inc.), and the electrolyte is measured using an ISOTON-II (manufactured by Beckman Coulter, Inc.). For the measurement, 0.5 mg to 50 mg of the measurement sample is added to 2 mL of a 5 mass % aqueous solution of a surfactant (preferably sodium alkylbenzene sulfonate) as a dispersant, and this is then added to 100 mL to 150 mL of the electrolyte. The electrolyte with the sample suspended in it is dispersed for 1 minute using an ultrasonic disperser, and the particle size of each particle in the range of 2 μm to 60 μm is measured using a Coulter Multisizer II with an aperture of 100 μm in diameter. The number of particles sampled is 50,000. For the measured particle size, a cumulative distribution based on volume is drawn from the small diameter side, and the particle size at which the cumulative 50% occurs is called the volume average particle size D 50v It is defined as:

[0095] In this embodiment, the average circularity of the toner particles is not particularly limited, but from the viewpoint of improving the cleaning properties of the toner from the image carrier, it is preferably 0.91 or more and 0.98 or less, more preferably 0.94 or more and 0.98 or less, and even more preferably 0.95 or more and 0.97 or less.

[0096] In this embodiment, the circularity of a toner particle is the perimeter of a circle having the same area as the projected image of the particle divided by the perimeter of the projected image of the particle, and the average circularity of a toner particle is the cumulative circularity of 50% from the smallest side in the distribution of circularity. The average circularity of a toner particle is determined by analyzing at least 3,000 toner particles using a flow-type particle image analyzer.

[0097] The average circularity of the toner particles can be controlled, for example, by adjusting the stirring speed of the dispersion, the temperature of the dispersion, or the retention time in the fusing step.

[0098] <External additives> The toner produced by the method for producing a toner for developing electrostatic images according to the present embodiment may contain an external additive, if necessary. The toner produced by the method for producing a toner for developing electrostatic images according to this embodiment may be toner particles that do not contain an external additive, or toner particles to which an external additive has been added. Examples of the external additive include inorganic particles. Examples of the inorganic particles include SiO2, TiO2, Al2O3, CuO, ZnO, SnO2, CeO2, Fe2O3, MgO, BaO, CaO, K2O, Na2O, ZrO2, CaO·SiO2, and K2O·(TiO2). n , Al2O3·2SiO2, CaCO3, MgCO3, BaSO4, MgSO4, etc.

[0099] The surface of the inorganic particles as an external additive may be subjected to a hydrophobic treatment. The hydrophobic treatment may be performed, for example, by immersing the inorganic particles in a hydrophobic treatment agent. The hydrophobic treatment agent is not particularly limited, and examples thereof include silane coupling agents, silicone oils, titanate coupling agents, and aluminum coupling agents. These may be used alone or in combination of two or more. The amount of the hydrophobizing agent is preferably, for example, 1 part by mass or more and 10 parts by mass or less with respect to 100 parts by mass of the inorganic particles.

[0100] Examples of external additives include resin particles (resin particles such as polystyrene, polymethyl methacrylate (PMMA), and melamine resin), cleaning agents (for example, metal salts of higher fatty acids such as zinc stearate, and fluorine-based polymer particles).

[0101] The amount of the external additive added is, for example, preferably from 0.01% by mass to 10% by mass, and more preferably from 0.01% by mass to 6% by mass, based on the toner particles.

[0102] <Electrostatic image developer> The electrostatic image developer according to this embodiment contains at least the toner produced by the method for producing a toner for developing electrostatic images according to this embodiment. The electrostatic image developer according to the present embodiment may be a one-component developer containing only the toner produced by the method for producing a toner for developing electrostatic images according to the present embodiment, or may be a two-component developer in which the toner is mixed with a carrier.

[0103] The carrier is not particularly limited, and may be any known carrier, such as a coated carrier in which the surface of a core material made of magnetic powder is coated with a coating resin, a magnetic powder dispersion type carrier in which magnetic powder is dispersed and mixed in a matrix resin, or a resin impregnated type carrier in which porous magnetic powder is impregnated with a resin. The magnetic powder dispersion type carrier and the resin impregnated type carrier may be a carrier in which the constituent particles of the carrier are used as a core material and are coated with a coating resin.

[0104] Examples of the magnetic powder include magnetic metals such as iron, nickel, and cobalt, and magnetic oxides such as ferrite and magnetite.

[0105] Examples of the coating resin and matrix resin include polyethylene, polypropylene, polystyrene, polyvinyl acetate, polyvinyl alcohol, polyvinyl butyral, polyvinyl chloride, polyvinyl ether, polyvinyl ketone, vinyl chloride-vinyl acetate copolymer, styrene-acrylic acid ester copolymer, straight silicone resin containing an organosiloxane bond or a modified product thereof, fluororesin, polyester, polycarbonate, phenolic resin, and epoxy resin. The coating resin and the matrix resin may contain other additives such as conductive particles. Examples of the conductive particles include particles of metals such as gold, silver, and copper, carbon black, titanium oxide, zinc oxide, tin oxide, barium sulfate, aluminum borate, and potassium titanate.

[0106] Here, in order to coat the surface of the core material with a coating resin, a method of coating with a coating layer forming solution in which the coating resin and, if necessary, various additives are dissolved in an appropriate solvent can be mentioned. The solvent is not particularly limited and may be selected taking into consideration the coating resin to be used, the suitability for application, etc. Specific resin coating methods include an immersion method in which the core material is immersed in a solution for forming a coating layer, a spray method in which the solution for forming a coating layer is sprayed onto the surface of the core material, a fluidized bed method in which the solution for forming a coating layer is sprayed onto the core material while it is suspended in flowing air, and a kneader coater method in which the core material of a carrier and the solution for forming a coating layer are mixed in a kneader coater and the solvent is removed.

[0107] In the two-component developer, the mixture 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.

[0108] <Image forming device / image forming method> An image forming apparatus / image forming method according to this embodiment will be described. The image forming apparatus according to the present embodiment includes an image carrier, a charging means for charging the surface of the image carrier, an electrostatic image forming means for forming an electrostatic image on the surface of the charged image carrier, a developing means for containing an electrostatic image developer and developing the electrostatic image formed on the surface of the image carrier as a toner image with the electrostatic image developer, a transfer means for transferring the toner image formed on the surface of the image carrier to the surface of a recording medium, and a fixing means for fixing the toner image transferred to the surface of the recording medium. The electrostatic image developer according to the present embodiment is used as the electrostatic image developer.

[0109] In the image forming apparatus according to this embodiment, an image forming method (the image forming method according to this embodiment) is carried out, which includes a charging step of charging the surface of an image carrier, an electrostatic image forming step of forming an electrostatic image on the surface of the charged image carrier, a developing step of developing the electrostatic image formed on the surface of the image carrier as a toner image using the electrostatic image developer according to this embodiment, a transfer step of transferring the toner image formed on the surface of the image carrier to the surface of a recording medium, and a fixing step of fixing the toner image transferred to the surface of the recording medium.

[0110] The image forming apparatus according to the present embodiment may be any of known image forming apparatuses, such as a direct transfer type apparatus in which a toner image formed on the surface of an image holder is directly transferred to a recording medium; an intermediate transfer type apparatus in which a toner image formed on the surface of an image holder is primarily transferred to the surface of an intermediate transfer body, and the toner image transferred to the surface of the intermediate transfer body is then secondarily transferred to the surface of a recording medium; an apparatus equipped with a cleaning means for cleaning the surface of the image holder before charging after the transfer of the toner image; and an apparatus equipped with a discharging means for irradiating the surface of the image holder with discharging light to discharge it before charging after the transfer of the toner image. Among them, an image forming apparatus equipped with a cleaning means for cleaning the surface of the image carrier is preferable, and a cleaning blade is preferable as the cleaning means. In the case of an intermediate transfer type device, the transfer means has, for example, an intermediate transfer body onto whose surface a toner image is transferred, a primary transfer means which primarily transfers the toner image formed on the surface of the image carrier onto the surface of the intermediate transfer body, and a secondary transfer means which secondarily transfers the toner image transferred onto the surface of the intermediate transfer body onto the surface of a recording medium.

[0111] In the image forming apparatus according to the present embodiment, for example, a portion including the developing means may have a cartridge structure (process cartridge) that is detachably attached to the image forming apparatus. As the process cartridge, for example, a process cartridge including a developing means that contains the electrostatic image developer according to the present embodiment is preferably used.

[0112] An example of an image forming apparatus according to the present embodiment will be described below, but the present invention is not limited to this. Note that only the main parts shown in the drawings will be described, and descriptions of the rest will be omitted.

[0113] FIG. 1 is a schematic diagram showing the configuration of an image forming apparatus according to the present embodiment. The image forming apparatus shown in Fig. 1 includes first to fourth electrophotographic image forming units 10Y, 10M, 10C, and 10K (image forming means) that output images of each color of yellow (Y), magenta (M), cyan (C), and black (K) based on color-separated image data. These image forming units (hereinafter sometimes simply referred to as "units") 10Y, 10M, 10C, and 10K are arranged in parallel at predetermined distances from each other in the horizontal direction. These units 10Y, 10M, 10C, and 10K may be process cartridges that are detachable from the image forming apparatus.

[0114] Above each of the units 10Y, 10M, 10C, and 10K in the drawing, an intermediate transfer belt 20 is provided as an intermediate transfer body extending through each unit. The intermediate transfer belt 20 is provided wound around a drive roll 22 and a support roll 24 that are arranged from left to right in the drawing at a distance from each other and contact the inner surface of the intermediate transfer belt 20, and is adapted to run in a direction from the first unit 10Y to the fourth unit 10K. Note that 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 them. In addition, an intermediate transfer body cleaning device 30 is provided on the image carrier side of the intermediate transfer belt 20, facing the drive roll 22. Further, the developing devices (developing means) 4Y, 4M, 4C, and 4K of the units 10Y, 10M, 10C, and 10K are supplied with toner including four colors of toner, yellow, magenta, cyan, and black, contained in toner cartridges 8Y, 8M, 8C, and 8K, respectively.

[0115] Since the first to fourth units 10Y, 10M, 10C, and 10K have the same configuration, the first unit 10Y that forms a yellow image and is disposed upstream in the direction in which the intermediate transfer belt travels will be described here as a representative example. Note that by assigning reference numerals of magenta (M), cyan (C), and black (K) instead of yellow (Y) to parts equivalent to those of the first unit 10Y, descriptions of the second to fourth units 10M, 10C, and 10K will be omitted.

[0116] The first unit 10Y has a photoconductor 1Y that acts as an image carrier. Around the photoconductor 1Y, a charging roll (an example of a charging means) 2Y that charges the surface of the photoconductor 1Y to a predetermined potential, an exposure device (an example of an electrostatic image forming means) 3 that exposes the charged surface to a laser beam 3Y based on a color-separated image signal to form an electrostatic image, a developing device (an example of a developing means) 4Y that supplies charged toner to the electrostatic image to develop it, a primary transfer roll 5Y (an example of a primary transfer means) that transfers the developed 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 this order. The primary transfer roll 5Y is disposed inside the intermediate transfer belt 20 and is provided at a position facing the photoconductor 1Y. Furthermore, a bias power supply (not shown) that applies a primary transfer bias is connected to each of the primary transfer rolls 5Y, 5M, 5C, and 5K. Each bias power supply varies the transfer bias applied to each primary transfer roll under the control of a control unit (not shown).

[0117] Hereinafter, an operation of forming a yellow image in first unit 10Y will be described. First, prior to operation, the surface of the photoconductor 1Y is charged to a potential of −600V to −800V by the charging roll 2Y. The photoconductor 1Y has a conductivity (for example, a volume resistivity at 20° C. of 1×10 -6 The photosensitive layer is formed by laminating a photosensitive layer on a substrate having a resistivity of Ωcm or less. This photosensitive layer is usually highly resistive (the resistance of ordinary resins), but when irradiated with a laser beam 3Y, the resistivity of the portion irradiated with the laser beam changes. A laser beam 3Y is output to the charged surface of the photoreceptor 1Y via an exposure device 3 in accordance with image data for yellow sent from a control unit (not shown). The laser beam 3Y is irradiated onto the photosensitive layer on the surface of the photoreceptor 1Y, and an electrostatic charge image of a yellow image pattern is formed on the surface of the photoreceptor 1Y.

[0118] An electrostatic image is an image formed on the surface of the photoconductor 1Y by electrostatic charging. The laser beam 3Y reduces the resistivity of the irradiated parts of the photosensitive layer, causing the charged charges on the surface of the photoconductor 1Y to flow, while the charges remain in the parts not irradiated by the laser beam 3Y. This is a so-called negative latent image. The electrostatic image formed on the photoconductor 1Y is rotated to a predetermined developing position as the photoconductor 1Y travels. Then, at this developing position, the electrostatic image on the photoconductor 1Y is made visible as a toner image (developed image) by the developing device 4Y.

[0119] The developing device 4Y contains an electrostatic image developer including at least yellow toner and a carrier, for example. The yellow toner is triboelectrically charged by being stirred inside the developing device 4Y, and is held on a developer roll (an example of a developer holder) with a charge of the same polarity (negative polarity) as the charge on the photoconductor 1Y. As the surface of the photoconductor 1Y passes through the developing device 4Y, the yellow toner electrostatically adheres to the discharged latent image portion on the surface of the photoconductor 1Y, and the latent image is developed with the yellow toner. The photoconductor 1Y on which the yellow toner image has been formed continues to travel at a predetermined speed, and the toner image developed on the photoconductor 1Y is transported to a predetermined primary transfer position.

[0120] When the yellow toner image on the photoreceptor 1Y is transported to the primary transfer, a primary transfer bias is applied to the primary transfer roll 5Y, and an electrostatic force from the photoreceptor 1Y toward the primary transfer roll 5Y acts on the toner image, and the toner image on the photoreceptor 1Y is transferred onto the intermediate transfer belt 20. The transfer bias applied at this time has a polarity (+) opposite to the polarity (-) of the toner, and in the first unit 10Y, for example, it is controlled to +10 μA by a control unit (not shown). On the other hand, the toner remaining on the photoconductor 1Y is removed and collected by the photoconductor cleaning device 6Y.

[0121] Further, the primary transfer bias applied to the primary transfer rolls 5M, 5C, and 5K subsequent to the second unit 10M is also controlled in accordance with the first unit. In this manner, the intermediate transfer belt 20 onto which the yellow toner image has been transferred by the first unit 10Y is conveyed successively through the second to fourth units 10M, 10C, and 10K, where the toner images of the respective colors are transferred in a superimposed manner.

[0122] The intermediate transfer belt 20 onto which the four color toner images have been transferred in multiple layers through the first to fourth units reaches a secondary transfer section that is composed of the intermediate transfer belt 20, a support roll 24 that contacts the inner surface of the intermediate transfer belt, and a secondary transfer roll (an example of a secondary transfer means) 26 arranged on the image bearing surface side of the intermediate transfer belt 20. Meanwhile, a recording paper (an example of a recording medium) P is fed at a predetermined timing into the gap between the secondary transfer roll 26 and the intermediate transfer belt 20 via a supply mechanism, and a secondary transfer bias is applied to the support roll 24. The transfer bias applied at this time has a (-) polarity that is the same as the (-) polarity of the toner, and an electrostatic force from the intermediate transfer belt 20 toward the recording paper P acts on the toner image, so that the toner image on the intermediate transfer belt 20 is transferred onto the recording paper P. The secondary transfer bias at this time is determined according to the resistance detected by a resistance detection means (not shown) that detects the resistance of the secondary transfer section, and is voltage-controlled.

[0123] Thereafter, the recording paper P is sent to a pressure contact portion (nip portion) of a pair of fixing rolls in a fixing device (one example of a fixing means) 28, where the toner image is fixed onto the recording paper P, forming a fixed image.

[0124] The recording paper P onto which the toner image is transferred can be, for example, plain paper used in electrophotographic copying machines, printers, etc. In addition to the recording paper P, other examples of the recording medium include overhead projector sheets, etc. 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 ordinary paper is coated with resin or the like, art paper for printing, etc. are preferably used.

[0125] After the color image has been fixed, the recording paper P is conveyed toward the discharge section, and the series of color image forming operations is completed.

[0126] <Process cartridge / toner cartridge> The process cartridge according to this embodiment will be described. The process cartridge according to this embodiment is a process cartridge that contains the electrostatic image developer according to this embodiment, is equipped with a developing means that develops an electrostatic image formed on the surface of an image carrier using the electrostatic image developer into a toner image, and is detachably attached to an image forming apparatus.

[0127] In addition, the process cartridge according to this embodiment is not limited to the above configuration, and may be configured to include a developing device and, as necessary, at least one other means selected from an image carrier, a charging means, an electrostatic image forming means, and a transfer means.

[0128] An example of a process cartridge according to the present embodiment will be described below, but the present invention is not limited to this example. Note that only the main parts shown in the drawings will be described, and descriptions of the rest will be omitted.

[0129] FIG. 2 is a schematic diagram showing the process cartridge according to the present embodiment. The process cartridge 200 shown in FIG. 2 is configured by, for example, a housing 117 having a mounting rail 116 and an opening 118 for exposure, and integrally combining and holding a photoconductor 107 (an example of an image carrier), a charging roll 108 (an example of a charging means) provided around the photoconductor 107, a developing device 111 (an example of a developing means), and a photoconductor cleaning device 113 (an example of a cleaning means), which are assembled into a cartridge. In FIG. 2, 109 denotes an exposure device (an example of an electrostatic image forming means), 112 denotes a transfer device (an example of a transfer means), 115 denotes a fixing device (an example of a fixing means), and 300 denotes recording paper (an example of a recording medium).

[0130] Next, the toner cartridge according to this embodiment will be described. The toner cartridge according to the present embodiment is a toner cartridge that contains the toner according to the present embodiment and is detachably attached to an image forming apparatus. The toner cartridge contains replenishment toner to be supplied to a developing unit provided in the image forming apparatus.

[0131] 1 is an image forming apparatus having a configuration in which toner cartridges 8Y, 8M, 8C, and 8K can be attached and detached, and the developing devices 4Y, 4M, 4C, and 4K are connected to the toner cartridges corresponding to the respective developing devices (colors) through toner supply pipes (not shown). When the toner contained in the toner cartridge becomes low, the toner cartridge is replaced. EXAMPLES

[0132] Hereinafter, the present embodiment will be described in more detail with reference to examples and comparative examples, but the present embodiment is not limited to these examples. Note that "parts" and "%" indicating amounts are based on mass unless otherwise specified.

[0133] [Synthesis of polyester resin] In a reaction vessel equipped with a stirrer, a thermometer, a condenser and a nitrogen gas inlet tube, 80 mol parts of polyoxypropylene (2,2)-2,2-bis (4-hydroxyphenyl) propane, 10 mol parts of ethylene glycol, 10 mol parts of cyclohexanediol, 80 mol parts of terephthalic acid, 10 mol parts of isophthalic acid and 10 mol parts of n-dodecenyl succinic acid were charged, and the reaction vessel was replaced with dry nitrogen gas. Then, 0.25 mass parts of titanium tetrabutoxide was charged as a catalyst with respect to 100 mass parts of the monomer component. After stirring and reacting for 3 hours at 170°C under a nitrogen gas flow, the temperature was further raised to 210°C over 1 hour, the pressure in the reaction vessel was reduced to 3 kPa, and the reaction was stirred and reacted under reduced pressure for 13 hours to obtain a polyester resin. The glass transition temperature of the obtained resin was measured using a differential scanning calorimeter (DSC) and found to be 58°C.

[0134] [Preparation of Polyester Resin Particle Dispersion] The polyester resin: 100 parts by weight Ethyl acetate: 70 parts by weight Isopropyl alcohol: 15 parts by weight The mixed solvent of ethyl acetate and isopropyl alcohol was put into a jacketed stainless steel vessel, and the polyester resin was gradually put therein and completely dissolved while stirring to obtain an oil phase. A 10% by mass aqueous ammonia solution was gradually dripped into the stirred oil phase by a pump so that the total amount was 3 parts by mass, and 230 parts by mass of ion-exchanged water was gradually dripped at a rate of 10 L / min to cause phase inversion emulsification. After that, a polyester resin particle dispersion (solid concentration: 40% by mass) was obtained by performing distillation under reduced pressure. The solid concentration was measured using a moisture meter MA35 (manufactured by Sartorius Mechatronics Japan Co., Ltd.). The solid concentration of each sample below was measured in the same manner. The volume average particle diameter (D50v) of the polyester resin particles in the obtained polyester resin particle dispersion was 180 nm. The volume average particle diameter of the polyester resin particles was measured using a laser diffraction particle size distribution measuring device (LA-700: manufactured by Horiba, Ltd.). The measurement method was to adjust the sample in the state of a dispersion liquid to about 2 g in solid content, add ion-exchanged water to this to make it about 40 mL, put this into a cell until the appropriate concentration was reached, wait for 2 minutes, and measure when the concentration in the cell became almost stable. The volume average particle diameters obtained for each particle size range (channel) were accumulated from the smallest volume average particle diameter, and the volume average particle diameter (D50v) was determined as the point where the accumulation reached 50%.

[0135] [Preparation of styrene acrylic resin particle dispersion] Styrene: 77 parts n-Butyl acrylate: 23 parts 1,10-Decanediol diacrylate: 0.4 parts Dodecanethiol: 0.7 parts The above materials were mixed and dissolved, and a solution of 1.0 part of anionic surfactant (Dowfax manufactured by Dow Chemical Co.) dissolved in 60 parts of ion-exchanged water was added, and the mixture was dispersed and emulsified in a flask to prepare an emulsion of monomers. Next, 2.0 parts of anionic surfactant (Dowfax manufactured by Dow Chemical Co.) was dissolved in 90 parts of ion-exchanged water, to which 2.0 parts of the above emulsion of monomers was added, and further, 10 parts of ion-exchanged water in which 1.0 part of ammonium persulfate was dissolved was added. Then, the remaining part of the emulsion of monomers was added over 3 hours, and after nitrogen replacement in the flask, the solution in the flask was heated to 75°C in an oil bath while stirring, and emulsion polymerization was continued for 5 hours, to obtain a styrene-acrylic resin particle dispersion. The solid content of the styrene-acrylic resin particle dispersion was adjusted to 40% by adding ion-exchanged water. The volume average particle size of the particles in the styrene-acrylic resin particle dispersion was (D50v) 160 nm.

[0136] [Preparation of Release Agent Particle Dispersion 1] Paraffin wax (manufactured by Nippon Seiro Co., Ltd., FNP92, endothermic peak onset 81°C): 45 parts Anionic surfactant (manufactured by Daiichi Kogyo Seiyaku Co., Ltd., Neogen RK): 5 parts - Ion-exchanged water: 200 parts The above was mixed and heated to 95°C, and dispersed using a homogenizer (IKA Ultra Turrax T50). After that, it was dispersed using a Manton-Gaulin high pressure homogenizer (Gaulin) to prepare a release agent particle dispersion (solid content concentration: 20%) in which the release agent was dispersed. The volume average particle size of the release agent particles was 0.19 μm.

[0137] [Preparation of Release Agent Particle Dispersion 2] Except for changing the paraffin wax to carnauba wax (RC160 manufactured by Toa Chemical Industries, Ltd., endothermic peak onset 85° C.), the same preparation method as for the release agent particle dispersion 1 was used to obtain release agent particle dispersion 2. The volume average particle size of the obtained release agent particles was 0.21 μm.

[0138] [Preparation of Colorant Particle Dispersion] Cyan pigment (Dainichi Seikagaku Kogyo Co., Ltd., Pigment Blue 15:3 (copper phthalocyanine)): 98 parts Anionic surfactant (Daiichi Kogyo Seiyaku Co., Ltd., Neogen R): 2 parts - Ion-exchanged water: 400 parts The above ingredients were mixed and dissolved, and dispersed for 10 minutes using a homogenizer (IKA Ultra Turrax), to obtain a colorant particle dispersion having a median particle size of 0.16 μm and a solid content of 20%.

[0139] Example 1 [Preparation of Toner Particle 1] Polyester resin particle dispersion: 450 parts Release agent particle dispersion 1:50 parts Colorant particle dispersion: 45 parts - Ion-exchanged water: 600 parts Anionic surfactant (Dowfax2A1, manufactured by The Dow Chemical Company): 2.2 parts The above components were mixed and dispersed in a reaction vessel equipped with a thermometer, a pH meter, and a stirrer at a temperature of 25°C using a stirrer and a homogenizer (Ultra Turrax T50 manufactured by IKA Co., Ltd.), while 100 parts of an aqueous aluminum sulfate solution with a concentration of 1.0% was added as a flocculant and continued for 10 minutes. Next, 1.0% nitric acid was added to adjust the pH in the system to 3.0, and a mantle heater was installed in the reaction vessel, and the mixture was heated while adjusting the rotation speed of the stirrer so as to sufficiently stir the mixture, and a dispersion A was obtained by holding the mixture at 45°C for 60 minutes. The tip peripheral speed of the stirrer was set to 1.2 m / s, and 250 parts by mass of a polyester resin particle dispersion (dispersion B) adjusted to a pH of 4.2 and a temperature of 18°C ​​was slowly added at a rate of 0.87 parts by mass per minute per 100 parts by mass of dispersion A. After 30 minutes of holding, 8 parts of 20% EDTA (ethylenediaminetetraacetic acid) solution was added to the reaction vessel, followed by the addition of 1 mol / L aqueous sodium hydroxide solution to control the pH of the system to 9.0. After that, the vessel was heated to 90°C at a temperature increase rate of 1°C / min and held for 2 hours. After the heating and holding was completed, the vessel was cooled to 30°C over 5 minutes while cooling with cooling water, and the cooled slurry was passed through a nylon mesh with a mesh size of 15 μm to remove coarse powder, and then washed with ion-exchanged water until the electrical conductivity of the filtrate was 10 μS / cm or less while separating the solid and liquid by Nutsche suction filtration. The washed solid content was finely crushed with a wet-dry type granulator (Comil) and vacuum freeze-dried for 24 hours to obtain toner particles 1.

[0140] [Preparation of Toner 1] 100 parts by mass of the obtained toner particles 1 were mixed and blended with the external additives shown in Table 1 in the amounts shown in Table 1 and 1.5 parts by mass of hydrophobic silica (manufactured by Nippon Aerosil Co., Ltd., RY50, number average particle size 140 nm) using a sample mill at 10,000 rpm for 30 seconds. The mixture was then sieved using a vibrating sieve with a mesh size of 45 μm to prepare toner 1 (toner for developing electrostatic images). The volume average particle size of the obtained toner 1 was 5.5 μm.

[0141] [Preparation of Carrier] After thoroughly stirring 500 parts of spherical magnetite powder particles (volume average particle diameter: 0.55 μm) with a Henschel mixer, 5.0 parts of a titanate coupling agent was added, the mixture was heated to 100° C., and mixed and stirred for 30 minutes to obtain spherical magnetite particles coated with a titanate coupling agent. Next, 6.25 parts of phenol, 9.25 parts of 35% formalin, 500 parts of the magnetite particles, 6.25 parts of 25% ammonia water, and 425 parts of water were mixed and stirred in a four-neck flask. Next, the mixture was reacted at 85°C for 120 minutes while stirring, cooled to 25°C, and 500 parts of water were added, after which the supernatant liquid was removed and the precipitate was washed with water. This was dried under reduced pressure at 150°C to 180°C to obtain a carrier with an average particle size of 35 μm.

[0142] [Preparation of electrostatic image developer 1] The obtained carrier and toner 1 were placed in a V blender in a ratio of toner:carrier=5:95 (mass ratio), and stirred for 20 minutes to obtain electrostatic image developer 1.

[0143] (Examples 2 and 9, and Comparative Example 1) A toner and an electrostatic image developer were prepared in the same manner as in Example 1, except that the pH and temperature of the dispersion A and the pH and temperature of the dispersion B were changed as shown in Table 1.

[0144] (Examples 10 and 11) A toner and an electrostatic image developer were prepared in the same manner as in Example 1, except that the rate at which Dispersion B was added was set as shown below, and the pH and temperature of Dispersion A and the pH and temperature of Dispersion B were changed as shown in Table 1. Example 10: Dispersion B was added at a rate of 0.65 parts by mass per minute relative to 100 parts by mass of dispersion A. Example 11 Dispersion B was added at a rate of 1.1 parts by mass per minute relative to 100 parts by mass of dispersion A.

[0145] Example 12 A toner and an electrostatic image developer were prepared in the same manner as in Example 1, except that the polyester resin particle dispersion used in Dispersion A was changed to a styrene-acrylic resin particle dispersion, and the pH and temperature of Dispersion A and the pH and temperature of Dispersion B were changed as shown in Table 1.

[0146] Example 13 A toner and an electrostatic image developer were prepared in the same manner as in Example 1, except that the release agent particle dispersion 1 used in dispersion A was changed to release agent particle dispersion 2, and the pH and temperature of dispersion A and the pH and temperature of dispersion B were changed as shown in Table 1.

[0147] Example 14 A toner and an electrostatic image developer were prepared in the same manner as in Example 1, except that the tip peripheral speed of the stirrer was set to 2.4 m / s before adding Dispersion B, and the pH and temperature of Dispersion A and the pH and temperature of Dispersion B were changed as shown in Table 1.

[0148] <Measurement of surface exposure rate of release agent on toner particles> The surface exposure rate of the release agent is a value measured by XPS (X-ray photoelectron spectroscopy). XPS (X-ray photoelectron spectroscopy) measurement was performed using toner particles as a measurement sample. JPS-9000MX manufactured by JEOL Ltd. was used as the XPS measurement device, and the measurement was performed using MgKα rays as the X-ray source, with the acceleration voltage set to 10 kV and the emission current set to 30 mA. Here, the amount of release agent on the surface of the toner particles was quantified by the peak separation method of the C1s spectrum. In the peak separation method, the measured C1s spectrum is separated into each component using curve fitting by the least squares method. Among the separated peaks, the exposure rate (area %) was calculated from the peak area and composition ratio derived from the release agent. For the component spectrum that is the basis of the separation, the C1s spectrum obtained by measuring the release agent and resin used in the preparation of the toner particles separately was used. Since the toner was made by adding external additives, the toner was dispersed in ion-exchanged water to which a dispersant such as a surfactant was added, and the external additives and toner particles were separated by applying ultrasonic waves using an ultrasonic homogenizer (US-300T: manufactured by Nippon Seiki Seisakusho Co., Ltd.). After that, the toner particles from which the external additives had been separated were extracted by drying and recovery after filtration and washing, and these toner particles were used as the measurement sample.

[0149] <Heat storage evaluation> 2 g of the obtained toner for developing electrostatic images was stored in an environment of 55° C. and 50% RH for 10 hours, and the state after storage was visually observed and evaluated according to the following evaluation criteria. A: Almost no agglomerates are observed. Excellent heat storage properties. B: A small amount of agglomeration was observed, and the heat storage stability was slightly inferior to that of A. C: The toner aggregates and does not have heat storage stability. A or B is preferred.

[0150] <Image density stability evaluation> The resulting electrostatic image developer was placed in a modified DocuCenter Color 400 (manufactured by Fuji Xerox Co., Ltd.) and the modified machine was left in a low temperature and low humidity environment of 10°C and 15% relative humidity for 24 hours. In an environment of 10°C temperature and 15% relative humidity, 50,000 sheets of test charts with an image density of 5% were continuously printed on A4 size plain paper. Using a spectrophotometer (X-Rite Ci62, manufactured by X-Rite Co., Ltd.), the L values ​​were measured at three points on the 1,000th and 50,000th images, respectively. * Value, a * value and b * The values ​​were measured, and the color difference ΔE was calculated based on the following formula, and the color difference ΔE was evaluated according to the following evaluation criteria. A: In the 1,000th and 50,000th images, the color difference ΔE is 1 or less, and the density difference is small. B: In the 1,000th and 50,000th images, the color difference ΔE is greater than 1 and is equal to or less than 3. There is a slight difference in density. C: In the 1,000th and 50,000th images, the color difference ΔE is greater than 3 and equal to or less than 5. There is a density difference, but it is within the allowable range. D: In the 1,000th and 50,000th images, the color difference ΔE exceeds 5. There is a density difference, which is at a problematic level. A, B or C is preferred.

[0151]

number

[0152] The evaluation results are summarized in Table 1.

[0153] [Table 1]

[0154] From the above results, it is understood that in this embodiment, a toner for developing electrostatic images having a smaller surface exposure rate of the release agent can be obtained as compared with the comparative example. Moreover, it is apparent from the above results that this embodiment provides a toner for developing electrostatic images which is excellent in thermal storage stability and image density stability. [Explanation of symbols]

[0155] 1Y, 1M, 1C, 1K Photoconductor (an example of an image carrier) 2Y, 2M, 2C, 2K Charging roll (an example of a charging means) 3 Exposure device (an example of an electrostatic 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 a primary transfer means) 6Y, 6M, 6C, 6K Photoconductor cleaning device (an example of a cleaning means) 8Y, 8M, 8C, 8K toner cartridges 10Y, 10M, 10C, 10K Image forming units 20 Intermediate transfer belt (an example of an intermediate transfer body) 22 Driving Roll 24 Support roll 26 Secondary transfer roll (an example of a secondary transfer means) 30 Intermediate transfer body cleaning device 107 Photoconductor (an example of an image carrier) 108 Charging roll (an example of charging means) 109 Exposure device (an example of electrostatic image forming means) 111 Developing device (an example of developing means) 112 Transfer device (an example of a transfer means) 113 Photoconductor cleaning device (an example of a cleaning means) 115 Fixing device (an example of fixing means) 116 Mounting Rail 118 Exposure Aperture 117 Cabinet 200 Process Cartridge 300 Recording paper (an example of a recording medium) P Recording paper (an example of a recording medium)

Claims

1. a first aggregation step of aggregating at least the resin particles and the release agent particles contained in the dispersion to prepare a dispersion A containing first aggregated particles; a second aggregation step of adding a dispersion B containing shell resin particles to the dispersion A to aggregate the shell resin particles to form second aggregated particles; and heating and fusing the second aggregate particles to form fused particles. a pH value of the dispersion A, which is a pH (A), and a pH value of the dispersion B, which is a pH (B), in the second aggregation step satisfy pH (A) < pH (B); The addition rate of the dispersion B in the second aggregation step is 0.6 parts by mass or more and 1.2 parts by mass or less per minute with respect to 100 parts by mass of the dispersion A. A method for producing a toner for developing electrostatic images.

2. 2. The method for producing a toner for developing an electrostatic image according to claim 1, wherein the pH(A) and the pH(B) in the second aggregation step satisfy 0.2<pH(B)-pH(A)<3.

0.

3. 3. The method for producing a toner for developing an electrostatic image according to claim 2, wherein the pH(A) and the pH(B) in the second aggregation step satisfy 0.5<pH(B)-pH(A)<1.

5.

4. 4. The method for producing a toner for developing an electrostatic image according to claim 1, wherein a temperature T(A) of the dispersion A and a temperature T(B) of the dispersion B in the second aggregation step satisfy T(A)>T(B).

5. 5. The method for producing a toner for developing an electrostatic image according to claim 4, wherein a temperature T(A) of the dispersion A and a temperature T(B) of the dispersion B in the second aggregation step satisfy −37° C.<T(B)−T(A)<−13° C.

6. 6. The method for producing a toner for developing electrostatic images according to claim 5, wherein a temperature T(A) of the dispersion A and a temperature T(B) of the dispersion B in the second aggregation step satisfy −30° C.<T(B)−T(A)<−20° C.

7. 7. The method for producing a toner for developing an electrostatic image according to claim 1, wherein the pH (B) is from 3.5 to 6.

0.

8. A method for producing a toner for developing electrostatic images according to any one of claims 1 to 7, wherein a temperature T(B) of the dispersion B in the second aggregation step is 15°C or higher and 25°C or lower.

9. 9. The method for producing a toner for developing an electrostatic image according to claim 1, wherein the resin particles aggregated in the aggregation step are polyester resin particles.

10. The method for producing a toner for developing an electrostatic image according to any one of claims 1 to 9, wherein the shell resin particles are polyester resin particles.

Images