Method for producing toner for developing electrostatic images

Abstract

To provide a method for manufacturing a toner for electrostatic charge image development which can obtain a toner for electrostatic charge image development that continuously forms images under high-temperature and high-humidity environment, then stops an image formation device for a fixed period of time, and suppresses occurrence of uneven glossiness when an image of high image density is formed.SOLUTION: A method for manufacturing a toner for electrostatic charge image development includes a first step of aggregating polyester resin particles and a flat coloring material, and preparing a first aggregated particle dispersion for dispersing first aggregated particles having a number average particle diameter of 1 μm or more, a second step of adding an amorphous resin particle dispersion for dispersing amorphous resin particles to the first aggregated particle dispersion, bonding the amorphous resin particles to the first aggregated particles, and obtaining second aggregated particles, and a third step of heating the second aggregated particle dispersion for dispersing the second aggregated particles, and fusing and uniting the second aggregated particles, wherein the amorphous resin particle dispersion satisfies formulae (1) to (3).SELECTED DRAWING: None

Description

[Technical Field]

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

[0002] Patent Document 1 proposes "a toner for developing electrostatic latent images, comprising a plurality of toner particles each having a core containing a binder resin and a release agent, and a multilayered shell layer partially covering the surface of the core, wherein the multilayered shell layer comprises a first shell layer containing a first polymer containing a repeating unit having an oxazoline group, a second shell layer containing a second polymer containing a repeating unit having a carboxyl group, and a third shell layer containing a third polymer containing a repeating unit having an oxazoline group, wherein the first shell layer, the second shell layer, and the third shell layer have a laminated structure in the order of the first shell layer, the second shell layer, and the third shell layer from the core side, and the second shell layer is in contact with an area of ​​the surface region of the core that is not covered by the first shell layer." [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2018-097052 Summary of the Invention [Problem to be solved by the invention]

[0004] An object of the present invention is to provide a method for producing a toner for developing electrostatic images, the method comprising: a first step of aggregating polyester resin particles and a flat colorant to prepare a first aggregate particle dispersion in which first aggregate particles having a number-average particle size of 1 μm or more are dispersed; a second step of adding an amorphous resin particle dispersion in which amorphous resin particles are dispersed to the first aggregate particle dispersion to cause the amorphous resin particles to adhere to the first aggregate particles to obtain second aggregate particles; and a third step of heating the second aggregate particle dispersion in which the second aggregate particles are dispersed to fuse and coalesce the second aggregate particles. The object of the present invention is to provide a method for producing a toner for developing electrostatic images, the method comprising: a first step of aggregating polyester resin particles and a flat colorant to prepare a first aggregate particle dispersion in which first aggregate particles having a number-average particle size of 1 μm or more are dispersed; a second step of adding an amorphous resin particle dispersion in which amorphous resin particles are dispersed to the first aggregate particle dispersion to cause the amorphous resin particles to adhere to the first aggregate particles to obtain second aggregate particles; and a third step of heating the second aggregate particle dispersion in which the second aggregate particles are dispersed to fuse and coalesce the second aggregate particles. Equation (C1) - 0.01 x A - 0.25 x B + 9.2 > pH, or pH > -0.01 x A - 0.25 x B + 10.0 Formula (C2): 100 nm > A, or A > 250 nm Formula (C3): 5 mg KOH / g > B, or B > 20 mg KOH / g (In the formulas (1) to (3), A is the particle size of the amorphous resin particles, B is the acid value of the amorphous resin, and pH is the pH of the amorphous resin particle dispersion liquid.) [Means for solving the problem]

[0005] The above problems are solved by the following means: <1> a first step of aggregating polyester resin particles and a flat colorant to prepare a first aggregate particle dispersion liquid in which first aggregate particles having a number average particle size of 1 μm or more are dispersed; a second step of adding an amorphous resin particle dispersion liquid in which amorphous resin particles are dispersed to the first aggregated particle dispersion liquid, and causing the amorphous resin particles to adhere to the first aggregated particles, thereby obtaining second aggregated particles; a third step of heating the second aggregated particle dispersion liquid in which the second aggregated particles are dispersed to fuse and coalesce the second aggregated particles, A method for manufacturing an electrostatic charge image developing toner, wherein the amorphous resin particle dispersion satisfies the following formulas (1) to (3). Formula (1): -0.01×A - 0.25×B + 9.2 ≤ pH ≤ -0.01×A - 0.25×B + 10.0 Formula (2): 100 nm ≤ A ≤ 250 nm Formula (3): 5 mgKOH / g ≤ B ≤ 20 mgKOH / g (In Formulas (1) to (3), A is the particle size of the amorphous resin particles, B is the acid value of the amorphous resin, and pH is the pH of the amorphous resin particle dispersion) <2> A first step of aggregating polyester resin particles and flat colorants to prepare a first aggregated particle dispersion in which first aggregated particles having a number average particle size of 1 μm or more are dispersed; A second step of adding an amorphous resin particle dispersion in which amorphous resin particles are dispersed to the first aggregated particle dispersion and attaching the amorphous resin particles to the first aggregated particles to obtain second aggregated particles; A third step of heating a second aggregated particle dispersion in which the second aggregated particles are dispersed to fuse and unite the second aggregated particles, and having: A method for manufacturing an electrostatic charge image developing toner, wherein the pH of the amorphous resin particle dispersion is 3.0 or more and 6.5 or less. <3> The method for manufacturing an electrostatic charge image developing toner according to <1> or <2>, wherein in the first step, before aggregating the polyester resin particles and the flat colorants, the dispersion in which the polyester resin particles and the flat colorants are dispersed is stirred with a stirring blade. <4> The method for manufacturing an electrostatic charge image developing toner according to any one of <1> to <3>, wherein in the second step, the amorphous resin particle dispersion is added to the first aggregated particle dispersion two or more times. <5> The method for manufacturing an electrostatic charge image developing toner according to <4>, wherein the solid content concentration of the amorphous resin particle dispersion satisfies the following formula (4). Formula (4): The solid content concentration of the amorphous resin particle dispersion added at the nth time < the solid content concentration of the amorphous resin particle dispersion added at the (n + 1)th time (In Formula (4), n is an integer of 1 or more) <6> The solid content concentration of the amorphous resin particle dispersion liquid satisfies the following formula (5): <5> 10. A method for producing the toner for developing electrostatic images according to claim 9. Formula (5): 2 mass%≦(solid content concentration of the amorphous resin particle dispersion liquid added for the (n+1)th time)−(solid content concentration of the amorphous resin particle dispersion liquid added for the (n)th time)≦20 mass% (In formula (5), n is an integer of 1 or more.) <7> The pH of the first aggregated particle dispersion is lower than the pH of the amorphous resin particle dispersion. <1> ~ <6> 10. A method for producing the toner for developing electrostatic images according to any one of claims 1 to 9. <8> the third step is carried out in a stirring tank having an opening and containing the second aggregate particle dispersion, 5 L / (min m) per unit amount of the second aggregate particle dispersion in the stirring tank 3 ) or more of the gas is blown into the second aggregated particles, and the second aggregated particles are fused and coalesced. <1> ~ <7> 10. A method for producing the toner for developing electrostatic images according to any one of claims 1 to 9. <9> The air flow rate is 5 L / (min m) per unit amount of the second aggregate particle dispersion liquid in the stirring tank. 3 ) or more 150L / (min m 3 ) or less <8> 10. A method for producing the toner for developing electrostatic images according to claim 9. <10> Before the first step, a step of stirring a flat colorant, a surfactant, and a dispersion medium to obtain a colorant dispersion liquid is included. <1> ~ <9> 10. A method for producing the toner for developing electrostatic images according to any one of claims 1 to 9. [Effects of the Invention]

[0006] <1> According to the invention, there is provided a method for producing a toner for developing electrostatic images, the method comprising: a first step of aggregating polyester resin particles and a flat colorant to prepare a first aggregate particle dispersion in which first aggregate particles having a number average particle size of 1 μm or more are dispersed; a second step of adding an amorphous resin particle dispersion in which amorphous resin particles are dispersed to the first aggregate particle dispersion to cause the amorphous resin particles to adhere to the first aggregate particles to obtain second aggregate particles; and a third step of heating the second aggregate particle dispersion in which the second aggregate particles are dispersed to fuse and coalesce the second aggregate particles. This method provides a toner for developing electrostatic images that is less susceptible to uneven gloss when forming high-density images by stopping an image forming apparatus after successively forming images in a high-temperature, high-humidity environment, compared to when the following formula (C1), (C2), or (C3) is satisfied: Equation (C1) - 0.01 x A - 0.25 x B + 9.2 > pH, or pH > -0.01 x A - 0.25 x B + 10.0 Formula (C2): 100 nm > A, or A > 250 nm Formula (C3): 5 mg KOH / g > B, or B > 20 mg KOH / g (In the formulas (1) to (3), A is the particle size of the amorphous resin particles, B is the acid value of the amorphous resin, and pH is the pH of the amorphous resin particle dispersion liquid.)

[0007] <2> According to the invention, there is provided a method for producing a toner for developing electrostatic images, the method comprising: a first step of aggregating polyester resin particles and a flat colorant to prepare a first aggregate particle dispersion in which first aggregate particles having a number average particle size of 1 μm or more are dispersed; a second step of adding an amorphous resin particle dispersion in which amorphous resin particles are dispersed to the first aggregate particle dispersion to cause the amorphous resin particles to adhere to the first aggregate particles to obtain second aggregate particles; and a third step of heating the second aggregate particle dispersion in which the second aggregate particles are dispersed to fuse and coalesce the second aggregate particles. In this method, an electrostatic image developing toner is obtained that is less susceptible to uneven gloss when forming high-density images by stopping an image forming apparatus for a certain period of time after successively forming images under a high-temperature, high-humidity environment than when the pH of the amorphous resin particle dispersion is less than 3.0 or more than 6.5.

[0008] <3> According to the invention, there is provided a method for producing a toner for developing electrostatic images, which can produce a toner for developing electrostatic images that suppresses the occurrence of uneven gloss when forming high-density images by continuously forming images in a high-temperature, high-humidity environment and then stopping the image forming apparatus for a certain period of time, compared to when the dispersion liquid in which the polyester resin particles and the flat colorant are dispersed is not stirred with a stirring blade before aggregating the polyester resin particles and the flat colorant in the first step. <4> According to the invention, there is provided a method for producing a toner for developing electrostatic images, which can produce a toner for developing electrostatic images that suppresses the occurrence of uneven gloss when forming high-density images by continuously forming images under a high-temperature, high-humidity environment and then stopping the image forming apparatus for a certain period of time, compared to when an amorphous resin particle dispersion is added to a first aggregate particle dispersion only once in the second step. <5> According to the invention related to (1), there is provided a method for producing a toner for developing electrostatic images, which can produce a toner for developing electrostatic images that suppresses the occurrence of uneven gloss when forming high-density images by stopping an image forming apparatus for a certain period of time after continuously forming images in a high-temperature, high-humidity environment, compared to when the solids concentration of the amorphous resin particle dispersion satisfies the following formula (C4): Formula (C4): Solid content concentration of the amorphous resin particle dispersion liquid added for the nth time ≧ Solid content concentration of the amorphous resin particle dispersion liquid added for the n+1th time (In formula (C4), n is an integer of 1 or more.)

[0009] <6> According to the invention related to (1), there is provided a method for producing a toner for developing electrostatic images, which can produce a toner for developing electrostatic images that suppresses the occurrence of uneven gloss when forming high-density images by stopping an image forming apparatus for a certain period of time after continuously forming images in a high-temperature, high-humidity environment, compared to when the solids concentration of the amorphous resin particle dispersion satisfies the following formula (C5): Formula (C5): 2% by mass > (solids concentration of the amorphous resin particle dispersion liquid added for the (n+1)th time) - (solids concentration of the amorphous resin particle dispersion liquid added for the (n+1)th time), or (solids concentration of the amorphous resin particle dispersion liquid added for the (n+1)th time) - (solids concentration of the amorphous resin particle dispersion liquid added for the (n)th time) > 20% by mass (In formula (C5), n is an integer of 1 or more.)

[0010] <7> According to the invention, there is provided a method for producing a toner for developing electrostatic images, which can suppress the occurrence of uneven gloss when forming high-density images by stopping the image forming apparatus for a certain period of time after continuously forming images under a high-temperature, high-humidity environment, compared to when the pH of the first aggregate particle dispersion is higher than the pH of the amorphous resin particle dispersion. <8> According to the invention, the third step is carried out in a stirring tank having an opening and containing the second aggregated particle dispersion, and the second aggregated particle dispersion in the stirring tank is supplied with a flow rate of 5 L / (min m) per unit amount of the second aggregated particle dispersion. 3 In comparison with a process for fusing and coalescing the second aggregated particles in a state where an air volume of less than 1000 psi is blown in, the method provides a method for producing a toner for developing electrostatic images, which can suppress the occurrence of uneven gloss when forming high-density images by continuously forming images in a high-temperature, high-humidity environment and then stopping the image forming apparatus for a certain period of time. <9> According to the invention, the air flow rate is 5 L / (min m) per unit amount of the second aggregate particle dispersion liquid in the stirring tank. 3 ) or less than 150L / (min·m 3 The present invention provides a method for producing a toner for developing electrostatic images, which can suppress the occurrence of uneven gloss when forming high-density images by stopping the image forming apparatus for a certain period of time after continuously forming images in a high-temperature, high-humidity environment, compared to when the temperature exceeds 100°C. <10> According to the invention, there is provided a method for producing a toner for developing electrostatic images, which, compared to a method that does not include a step of stirring a flat colorant, a surfactant, and a dispersion medium to obtain a colorant dispersion liquid before the first step, can produce a toner for developing electrostatic images by continuously forming images in a high-temperature, high-humidity environment, stopping the image forming apparatus for a certain period of time, and thereby suppressing the occurrence of uneven gloss when forming images with high image density. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a schematic configuration diagram illustrating an image forming apparatus according to an embodiment of the present invention. [Figure 2] FIG. 2 is a schematic diagram illustrating the configuration of a process cartridge according to the present embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, an embodiment of the present invention will be described. These descriptions and examples are intended to illustrate the embodiment and are not intended to limit the scope of the invention. In the present specification, the upper or lower limit of one numerical range may be replaced with the upper or lower limit of another numerical range. In addition, in the present specification, the upper or lower limit of a numerical range may be replaced with a value shown in the examples.

[0013] Each component may contain multiple types of the corresponding substance. When referring to the amount of each component in a composition, if there are multiple substances corresponding to each component in the composition, the amount refers to the total amount of those multiple substances present in the composition, unless otherwise specified. In this specification, the term "process" includes not only an independent process but also a process that cannot be clearly distinguished from other processes, as long as the intended purpose of the process is achieved. Each component may contain multiple types of the corresponding substance.

[0014] <Method of manufacturing toner for developing electrostatic images> A method for producing a toner for developing electrostatic images (hereinafter also simply referred to as "toner") according to a first embodiment includes: a first step of aggregating polyester resin particles and a flat colorant to prepare a first aggregate particle dispersion in which first aggregate particles having a number average particle size of 1 μm or more are dispersed; a second step of adding an amorphous resin particle dispersion in which amorphous resin particles are dispersed to the first aggregate particle dispersion to cause the amorphous resin particles to adhere to the first aggregate particles to obtain second aggregate particles; and a third step of heating the second aggregate particle dispersion in which the second aggregate particles are dispersed to fuse and coalesce the second aggregate particles, wherein the amorphous resin particle dispersion satisfies the following formulas (1) to (3): Formula (1): -0.01×A-0.25×B+9.2≦pH≦-0.01×A-0.25×B+10.0 Formula (2): 100nm≦A≦250nm Formula (3): 5mgKOH / g≦B≦20mgKOH / g (In the formulas (1) to (3), A is the particle size of the amorphous resin particles, B is the acid value of the amorphous resin, and pH is the pH of the amorphous resin particle dispersion liquid.)

[0015] The toner manufacturing method according to the first embodiment, as configured above, can produce a toner that suppresses the occurrence of uneven gloss when forming high-density images by stopping the image forming apparatus for a certain period of time after continuously forming images in a high-temperature, high-humidity environment. The reason for this is presumed to be as follows.

[0016] A toner obtained by a toner manufacturing method including: a first step of preparing a first aggregate particle dispersion in which polyester resin particles and a flat colorant are aggregated to disperse first aggregate particles having a number-average particle size of 1 μm or more; a second step of adding an amorphous resin particle dispersion in which amorphous resin particles are dispersed to the first aggregate particle dispersion to cause the amorphous resin particles to adhere to the first aggregate particles to obtain second aggregate particles; and a third step of heating the second aggregate particle dispersion in which the second aggregate particles are dispersed to fuse and coalesce the second aggregate particles. This toner is prone to uneven gloss when images are formed continuously in a high-temperature, high-humidity environment, and then the image forming apparatus is stopped for a certain period of time to form an image with high image density. This is thought to be because the toner manufacturing method in question is prone to contain toner that does not contain colorant (hereinafter also referred to as "white particles"). When images are continuously formed in a high-temperature, high-humidity environment, the white particles tend to have a large charge, making them difficult to develop and prone to remaining in the developing machine. If the image forming apparatus is stopped for a certain period of time under this condition, the charge on the white particles decreases, making them more susceptible to development in the same way as toner that contains colorant. Therefore, when a high-density image is subsequently formed, the white particles are also developed, which can cause uneven gloss in the image.

[0017] In the toner manufacturing method according to the first embodiment, the particle size of the amorphous resin particles satisfies the above formula (2). By setting the particle size of the amorphous resin particles to 250 nm or less, the particle size does not become too large, and the cohesive force between the particle sizes of the amorphous resin particles is likely to be reduced. Furthermore, by setting the particle size of the amorphous resin particles to 100 nm or more, the dispersibility of particles derived from carboxy groups present on the surface of the amorphous resin particles is reduced, and the amorphous resin particles are likely to adhere to the first aggregate particles. Furthermore, in the toner manufacturing method according to the first embodiment, the acid value of the amorphous resin satisfies the above formula (3). When the acid value of the amorphous resin satisfies the above formula (3), the amount of carboxy groups present on the surfaces of the amorphous resin particles is adjusted, the dispersibility of the amorphous resin particles is reduced, and the amorphous resin particles tend to adhere to the first aggregate particles. In the toner manufacturing method according to the first embodiment, the particle size of the amorphous resin particles and the acid value of the amorphous resin satisfy the above formula (1). Although the reason for this is unclear, the inventors have conducted extensive research and found that when the particle size of the amorphous resin particles, the acid value of the amorphous resin, and the pH of the amorphous resin particle dispersion satisfy the above formula (1), the amorphous resin particles are more likely to adhere to the first aggregate particles. As described above, according to the method for producing the toner according to the first embodiment, the occurrence of white particles is suppressed.

[0018] From these facts, it is presumed that the toner manufacturing method according to the first embodiment, with the above-described configuration, can produce a toner that suppresses the occurrence of uneven gloss when forming high-density images by continuously forming images in a high-temperature, high-humidity environment and then stopping the image forming apparatus for a certain period of time.

[0019] The toner manufacturing method according to the second embodiment includes a first step of preparing a first aggregate particle dispersion in which polyester resin particles and a flat colorant are aggregated to disperse first aggregate particles having a number-average particle size of 1 μm or more; a second step of adding an amorphous resin particle dispersion in which amorphous resin particles are dispersed to the first aggregate particle dispersion to cause the amorphous resin particles to adhere to the first aggregate particles to obtain second aggregate particles; and a third step of heating the second aggregate particle dispersion in which the second aggregate particles are dispersed to fuse and coalesce the second aggregate particles, wherein the pH of the amorphous resin particle dispersion is 3.0 or more and 6.5 or less.

[0020] The toner manufacturing method according to the second embodiment, configured as described above, can produce a toner that suppresses the occurrence of uneven gloss when forming high-density images by stopping the image forming apparatus for a certain period of time after continuously forming images in a high-temperature, high-humidity environment. The reason for this is presumed to be as follows.

[0021] In the toner manufacturing method according to the second embodiment, the pH of the amorphous resin particle dispersion is 3.0 or more and 6.5 or less. If the pH of the amorphous resin particle dispersion is less than 3.0, the carboxyl groups present on the surface of the amorphous resin particles do not dissociate, making the particles themselves unstable and facilitating aggregation between the crystalline resin particles and forming white particles. If the pH of the amorphous resin particle dispersion exceeds 6.5, the carboxyl groups present on the surface of the amorphous resin particles are easily dissociated, stabilizing the particles and making them less likely to adhere to the primary aggregated particles. By adjusting the pH of the amorphous resin dispersion to 3.0 or more and 6.5 or less, the carboxyl groups present on the surface of the amorphous particles are appropriately dissociated, making them more likely to adhere to the surfaces of the primary aggregated particles, thereby suppressing the formation of white particles. As described above, according to the method for producing the toner according to the second embodiment, the occurrence of white particles is suppressed.

[0022] From these facts, it is presumed that the toner manufacturing method according to the second embodiment, with the above-described configuration, can produce a toner that suppresses the occurrence of uneven gloss when forming high-density images by continuously forming images in a high-temperature, high-humidity environment and then stopping the image forming apparatus for a certain period of time.

[0023] Hereinafter, a toner manufacturing method corresponding to either the toner manufacturing method according to the first or second embodiment will be described in detail, however, an example of the toner manufacturing method of the present invention may be any one of the toner manufacturing methods according to the first or second embodiment.

[0024] The polyester resin particles and amorphous resin particles serve as the binder resin of the toner obtained by the toner manufacturing method according to this embodiment.

[0025] (Dispersion liquid preparation process) Before the first step, it is advisable to prepare dispersions of the respective materials, mix the dispersions, and then carry out the first step. Specifically, this is done as follows. It is preferable to include a step before the first step of stirring a flat colorant, a surfactant, and a dispersion medium to obtain a colorant dispersion liquid. By including the step of obtaining a colorant dispersion, aggregation of the flat colorant particles in the first step is suppressed, and the polyester resin particles are more likely to adhere to the surface of the flat colorant. This suppresses aggregation of the polyester resin particles, and reduces the occurrence of white balls. This results in a toner manufacturing method that can produce a toner that suppresses the occurrence of gloss unevenness when forming high-density images by stopping the image forming apparatus for a certain period of time after continuously forming images in a high-temperature, high-humidity environment.

[0026] The surfactant and dispersion medium have the same meanings as those of the surfactant and dispersion liquid in the first step described below, and the preferred ranges are also the same.

[0027] Furthermore, before the first step, a polyester resin particle dispersion liquid may be prepared by dispersing polyester resin particles in a dispersion medium. Furthermore, if necessary, before the first step, a release agent particle dispersion liquid may be prepared by dispersing release agent particles in a dispersion medium.

[0028] (1st step) The first step is a step of aggregating polyester resin particles and a flat colorant to prepare a first aggregate particle dispersion liquid in which first aggregate particles having a number average particle size of 1 μm or more are dispersed. In the first step, colorant particles other than the flat colorant and release agent particles may be aggregated together with the polyester resin particles and the flat colorant.

[0029] Here, the flat colorant particles other than the colorant refer to particles containing a flat colorant other than the colorant as a main component. Here, the flat particles containing a colorant other than the color material as a main component refer to particles in which the content of the flat colorant other than the color material relative to the entire particle is 90 mass % or more. Examples of the colorant other than the flat colorant include colorants described below in the description of the colorant other than the flat colorant that may be contained in the toner. The amount of colorant other than the flat colorant added is not particularly limited, and the content of colorant other than the flat colorant relative to the total toner particles contained in the obtained toner is preferably 1% by mass or more and 20% by mass or less, and more preferably 5% by mass or more and 15% by mass or less, relative to the total toner particles described below.

[0030] The release agent particles refer to particles containing a release agent as a main component. Here, particles containing a release agent as a main component refer to particles in which the content of the release agent relative to the total amount of the particles is 90 mass % or more. Examples of the release agent include the release agents described below in the description of the release agent that may be contained in the toner. The amount of release agent particles added is not particularly limited, and the content of the release agent relative to all toner particles contained in the resulting toner is preferably 1% by mass or more and 20% by mass or less, and more preferably 5% by mass or more and 15% by mass or less, relative to all toner particles described below.

[0031] The aggregation is performed, for example, by dispersing the polyester resin particles and the flat color material in a dispersion medium to obtain a dispersion, and then aggregating the polyester resin particles and the flat color material in the dispersion. Furthermore, if necessary, the polyester resin particles, the flat colorant, and the release agent particles may be dispersed in a dispersion medium to obtain a dispersion liquid, and then the polyester resin particles, the flat colorant, and the release agent particles may be aggregated in the dispersion liquid.

[0032] Furthermore, for example, when a colorant dispersion liquid and a polyester resin particle dispersion liquid are prepared before the first step, the colorant dispersion liquid and the polyester resin particle dispersion liquid may be mixed to obtain a dispersion liquid, and then the polyester resin particles and the flat colorant may be aggregated in the dispersion liquid. If necessary, the colorant dispersion and the polyester resin particle dispersion may be mixed with a release agent particle dispersion to obtain a dispersion, and then the polyester resin particles, the flat colorant particles, and the release agent particles may be aggregated in the dispersion.

[0033] Specifically, the aggregation is performed by adding an aggregating agent to the dispersion and adjusting the pH of the dispersion to an acidic value (for example, a pH of 2 or more and 5 or less), adding a dispersion stabilizer as needed, and then heating the dispersion to a temperature corresponding to the glass transition temperature of the polyester resin particles (specifically, for example, the glass transition temperature of the resin particles minus 30°C or more and the glass transition temperature minus 10°C or less), thereby aggregating the particles dispersed in the dispersion to form first aggregated particles. In the first step, for example, the aggregating agent may be added to the dispersion at room temperature (e.g., 25°C) while stirring, the pH of the dispersion may be adjusted to an acidic value (e.g., a pH of 2 or more and 5 or less), and a dispersion stabilizer may be added as needed, followed by heating.

[0034] In the first step, before the polyester resin particles and the flat color material are aggregated, the dispersion liquid in which the polyester resin particles and the flat color material are dispersed is preferably stirred with a stirring blade.

[0035] As described above, by stirring the dispersion liquid in which polyester resin particles and flat colorant are dispersed with a stirring blade, the force applied to the flat colorant during stirring of the dispersion liquid is not too large. This makes it easier to suppress deformation of the flat colorant. This makes it easier for the polyester resin particles to adhere to the surface of the flat colorant. Therefore, aggregation of the polyester resin particles is suppressed, and the occurrence of white balls is suppressed. Therefore, this is a method for producing a toner that can suppress the occurrence of uneven gloss when forming high-density images by stopping the image forming apparatus for a certain period of time after continuously forming images in a high-temperature, high-humidity environment.

[0036] -Polyester resin particles- The polyester resin particles refer to particles containing polyester resin as the main component. Here, particles containing polyester resin as a main component refer to particles in which the content of polyester resin relative to the total amount of the particles is 90% by mass or more.

[0037] Examples of polyester resins include known amorphous polyester resins. The polyester resin may be used in combination with a crystalline polyester resin. However, the content of the crystalline polyester resin is preferably in the range of 2% by mass to 40% by mass (preferably 2% by mass to 20% by mass) relative to the total binder resin.

[0038] The "crystalline" nature of a resin refers to the presence of a clear endothermic peak rather than a stepwise change in endothermic heat in differential scanning calorimetry (DSC). Specifically, this refers to the half-width of the endothermic peak being within 10°C when measured at a heating rate of 10°C / min. On the other hand, the term "amorphous" for a resin means that the half-width exceeds 10°C, that the endothermic amount exhibits a stepwise change, or that no clear endothermic peak is observed.

[0039] Amorphous polyester resin Examples of the amorphous polyester resin include a condensation polymer of a polycarboxylic acid and a polyhydric alcohol. Note that, as the amorphous polyester resin, a commercially available product or a synthesized product may be used.

[0040] Examples of polycarboxylic acids include aliphatic dicarboxylic acids (such as oxalic acid, malonic acid, maleic acid, fumaric acid, citraconic acid, itaconic acid, glutaconic acid, succinic acid, alkenylsuccinic acid, adipic acid, and sebacic acid), alicyclic dicarboxylic acids (such as cyclohexanedicarboxylic acid), aromatic dicarboxylic acids (such as terephthalic acid, isophthalic acid, phthalic acid, and naphthalenedicarboxylic acid), anhydrides thereof, and lower alkyl esters thereof (e.g., having 1 to 5 carbon atoms). Among these, aromatic dicarboxylic acids are preferred as polycarboxylic acids. The polycarboxylic 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 alkyl esters thereof (e.g., having 1 to 5 carbon atoms). The polycarboxylic acids may be used alone or in combination of two or more.

[0041] 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, preferred polyhydric alcohols are aromatic diols and alicyclic diols, and more preferred are aromatic diols. As the polyhydric alcohol, a trihydric or higher polyhydric alcohol having a crosslinked or branched structure may be used in combination with the diol. Examples of trihydric or higher polyhydric alcohols include glycerin, trimethylolpropane, and pentaerythritol. The polyhydric alcohols may be used alone or in combination of two or more.

[0042] The glass transition temperature (Tg) of the amorphous polyester resin is preferably 50°C or higher and 80°C or lower, and more preferably 50°C or higher and 65°C or lower. The glass transition temperature is determined from a DSC curve obtained by differential scanning calorimetry (DSC), more specifically, from the "extrapolated glass transition onset temperature" described in JIS K 7121-1987 "Method for measuring transition temperatures of plastics."

[0043] The weight average molecular weight (Mw) of the amorphous polyester resin is preferably 5,000 or more and 1,000,000 or less, and more preferably 7,000 or more and 500,000 or less. The number average molecular weight (Mn) of the amorphous polyester resin is preferably 2,000 or more and 100,000 or less. The molecular weight distribution Mw / Mn of the amorphous polyester resin is preferably 1.5 or more and 100 or less, and more preferably 2 or more and 60 or less. The weight-average molecular weight and number-average molecular weight are measured by gel permeation chromatography (GPC). Molecular weight measurements by GPC are performed using a Tosoh GPC HLC-8120GPC measuring device and a Tosoh TSKgel SuperHM-M (15 cm) column in THF solvent. The weight-average molecular weight and number-average molecular weight are calculated from the measurement results using a molecular weight calibration curve prepared with monodisperse polystyrene standard samples.

[0044] The amorphous polyester resin can be obtained by a known manufacturing method, for example, by carrying out the reaction at a polymerization temperature of 180°C or higher and 230°C or lower, reducing the pressure in the reaction system as necessary, and removing water and alcohol generated during the condensation. If the raw material monomer is not soluble or compatible at the reaction temperature, a high-boiling solvent may be added as a solubilizer to dissolve it. In this case, the polycondensation reaction is carried out while distilling off the solubilizer. If a monomer with poor compatibility is present, it is advisable to first condense the poorly compatible monomer with the acid or alcohol to be polycondensed, and then polycondense the monomer with the main component.

[0045] Crystalline polyester resin The crystalline polyester resin may be, for example, a polycondensate of a polycarboxylic acid and a polyhydric alcohol. Note that, as the crystalline polyester resin, a commercially available product or a synthesized product may be used. Here, the crystalline polyester resin is preferably a polycondensate using a polymerizable monomer having a linear aliphatic group rather than a polymerizable monomer having an aromatic group, since it easily forms a crystalline structure.

[0046] Examples of polycarboxylic 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, and naphthalene-2,6-dicarboxylic acid), anhydrides thereof, and lower alkyl esters thereof (e.g., having 1 to 5 carbon atoms). The polycarboxylic acid may be a tricarboxylic or higher carboxylic acid having a crosslinked or branched structure in combination with a dicarboxylic acid. Examples of the tricarboxylic acid include aromatic carboxylic acids (e.g., 1,2,3-benzenetricarboxylic acid, 1,2,4-benzenetricarboxylic acid, 1,2,4-naphthalenetricarboxylic acid, etc.), anhydrides thereof, and lower alkyl esters thereof (e.g., having 1 to 5 carbon atoms). As the polycarboxylic 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 polycarboxylic acids may be used alone or in combination of two or more.

[0047] 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, such as glycerin, trimethylolethane, trimethylolpropane, or pentaerythritol, in combination with the diol. The polyhydric alcohols may be used alone or in combination of two or more.

[0048] Here, the polyhydric alcohol has an aliphatic diol content of 80 mol % or more, preferably 90 mol % or more.

[0049] 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 is determined from a DSC curve obtained by differential scanning calorimetry (DSC) by using the "melting peak temperature" described in the method for determining the melting temperature in JIS K7121-1987 "Method for measuring transition temperatures of plastics."

[0050] The weight average molecular weight (Mw) of the crystalline polyester resin is preferably 6,000 or more and 35,000 or less.

[0051] The crystalline polyester resin can be obtained by a known manufacturing method, for example, in the same manner as the amorphous polyester.

[0052] The volume average particle size of the polyester resin particles dispersed in the dispersion before aggregation is preferably 0.01 μm or more and 1 μm or less, more preferably 0.08 μm or more and 0.8 μm or less, and even more preferably 0.1 μm or more and 0.6 μm or less. The volume average particle size of the polyester resin particles is measured using a particle size distribution obtained by measurement with a laser diffraction particle size distribution analyzer (for example, LA-700 manufactured by Horiba, Ltd.), and the cumulative distribution for the volume of the divided particle size range (channel) is calculated from the small particle size side, and the particle size at which the cumulative 50% of all particles is measured is defined as the volume average particle size D50v. The volume average particle sizes of particles in other dispersions are also measured in the same way.

[0053] -Flat color material- The ratio of the average length in the major axis direction of the flat color material to the average length in the thickness direction (average length in the major axis direction / average length in the thickness direction) is preferably from 5 to 200, more preferably from 10 to 100, and even more preferably from 10 to 70. The average length in the major axis direction of the flat color material is preferably from 1 μm to 20 μm, and more preferably from 3 μm to 10 μm.

[0054] The average length in the major axis direction and the average length in the thickness direction of the flat colorant are values ​​measured by the following method. Toner is applied to recording media such as paper at a toner density of 3 g / m 2By fixing the toner image with a fluorine-containing resin (HF), the surface direction of the flat color material contained in the toner is oriented along the surface direction of the recording medium. The toner image is embedded using a bisphenol A liquid epoxy resin and a curing agent, and then a cutting sample is prepared. Next, the cutting sample is cut using a diamond knife with a cutting machine, such as an ultramicrotome (Ultoracut UCT, manufactured by Leica), to prepare an observation sample. This observation sample is observed under a transmission electron microscope (TEM), and the major axis length and thickness length of 100 flat color materials are calculated. The arithmetic mean value of the major axis length of each measured flat color material is calculated to be the average major axis length. In addition, the arithmetic mean value of the thickness length of each measured flat color material is calculated to be the average thickness length. The magnification used for observation is such that approximately 1 to 10 bright pigment particles are visible per field of view.

[0055] The flat color material is preferably a glitter pigment. The luster pigment is a pigment that exhibits luster. Examples of the luster pigment include powders of metals such as aluminum, brass, bronze, nickel, stainless steel, and zinc; mica coated with titanium oxide or yellow iron oxide; flaky or plate-like crystals of aluminosilicates, basic carbonates, barium sulfate, titanium oxide, and bismuth oxychloride; glass flake powders, metal-deposited glass flake powders, and guanine crystals.

[0056] As the bright pigment, metal powder is preferred from the viewpoint of specular reflection intensity, flat metal powder is more preferred from the viewpoint of higher specular reflection intensity, and aluminum is preferred from the viewpoint of ease of obtaining flat powder. That is, flat aluminum powder is preferred as the bright pigment. The surface of the metal powder may be coated with acrylic resin, polyester resin, or the like.

[0057] Examples of the flocculant include a surfactant having a polarity opposite to that of the surfactant used as the dispersant added to the 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 can be reduced and the charging characteristics can be 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.

[0058] 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 these, it is preferable to use an aluminum compound as the flocculant. The chelating agent may be a water-soluble chelating agent, such as hydroxycarboxylic acid (e.g., tartaric acid, citric acid, gluconic acid), 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.

[0059] The dispersion medium contained in the dispersion liquid in the first step is preferably an aqueous medium. Examples of aqueous media include water such as distilled water and ion-exchanged water, alcohols, etc. These may be used alone or in combination of two or more.

[0060] Furthermore, the dispersion liquid in the first step preferably contains a surfactant as an aggregating agent or dispersant. Examples of surfactants include anionic surfactants such as sulfate ester salts, sulfonate salts, phosphate esters, 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. Nonionic surfactants may be used in combination with anionic surfactants or cationic surfactants. The surfactants may be used alone or in combination of two or more.

[0061] In the first step, the solid content concentration of the dispersion 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 the polyester resin particles, flat colorant, etc.

[0062] The number average particle size of the primary aggregate particles is set to 1 μm or more, but from the viewpoint of obtaining a toner that further suppresses the occurrence of gloss unevenness, it is preferably 1 μm or more and 8 μm or less, more preferably 2 μm or more and 6 μm or less, and even more preferably 3 μm or more and 5 μm or less.

[0063] The number average particle size of the primary aggregate particles is measured 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.), by subtracting the cumulative distribution of the number of particles from the small particle size side for the divided particle size range (channel), and measuring the particle size at which the cumulative distribution of all particles is 50% as the number average particle size.

[0064] (2nd process) The second step is a step of adding an amorphous resin particle dispersion in which amorphous resin particles are dispersed to the first aggregated particle dispersion, and attaching the amorphous resin particles to the first aggregated particles to obtain second aggregated particles.

[0065] Specifically, the adhesion in the second step is carried out by, for example, adding a dispersion stabilizer as needed, and then heating to the glass transition temperature of the amorphous resin particles (specifically, for example, a temperature equal to or lower than the glass transition temperature of the amorphous resin particles), causing the amorphous resin particles to adhere to the surfaces of the first aggregated particles, thereby forming second aggregated particles. Then, the pH of the dispersion containing the second aggregated particles is adjusted to stop the progress of aggregation. In the second step, for example, the first aggregate particle dispersion may be stirred with a rotary shear homogenizer at room temperature (for example, 25° C.) with the addition of a dispersion stabilizer as needed, and then the heating may be carried out. In the second step, a flocculant may be added, but it is preferable not to add it from the viewpoint of flocculation uniformity.

[0066] -Amorphous resin particle dispersion- The amorphous resin particle dispersion liquid disperses the amorphous resin particles. Here, the amorphous resin particles refer to particles containing an amorphous resin as a main component. Here, particles containing an amorphous resin as a main component refer to particles in which the content of the amorphous resin relative to the total amount of the particles is 90 mass % or more.

[0067] The amorphous resin particle dispersion contains a dispersion medium for dispersing the amorphous resin particles. The dispersion medium contained in the amorphous resin particle dispersion is preferably an aqueous medium. Examples of aqueous media include water such as distilled water and ion-exchanged water, alcohols, etc. These may be used alone or in combination of two or more.

[0068] Examples of amorphous resins include styrenes (e.g., styrene, parachlorostyrene, α-methylstyrene, etc.), (meth)acrylic acid esters (e.g., methyl acrylate, acrylic acid esters, etc.), and the like. Examples of the vinyl resin include a homopolymer of a monomer such as ethyl acrylate, n-propyl acrylate, n-butyl acrylate, lauryl methacrylate, 2-ethylhexyl acrylate, methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, lauryl methacrylate, 2-ethylhexyl methacrylate, etc., ethylenically unsaturated nitriles (e.g., acrylonitrile, methacrylonitrile, etc.), vinyl ethers (e.g., vinyl methyl ether, vinyl isobutyl ether, etc.), vinyl ketones (vinyl methyl ketone, vinyl ethyl ketone, vinyl isopropenyl ketone, etc.), and olefins (e.g., ethylene, propylene, butadiene, etc.), or a copolymer of two or more of these monomers. These amorphous resins may be used alone or in combination of two or more.

[0069] As the amorphous resin, an amorphous polyester resin is preferable. The amorphous polyester resin contained in the amorphous resin particles has the same meaning as the amorphous polyester described above, and the preferred range is also the same.

[0070] The amorphous resin particle dispersion satisfies the following formulas (1) to (3). Formula (1): -0.01×A-0.25×B+9.2≦pH≦--0.01×A-0.25×B+10.0 Formula (2): 100nm≦A≦200nm Formula (3): 9 mg KOH / g ≦ B ≦ 15 mg KOH / g (In the formulas (1) to (3), A is the particle size of the amorphous resin particles, B is the acid value of the amorphous resin, and pH is the pH of the amorphous resin particle dispersion liquid.)

[0071] From the viewpoint of providing a toner manufacturing method that can obtain a toner that further suppresses the occurrence of uneven gloss when forming high-density images by continuously forming images in a high-temperature, high-humidity environment and then stopping the image forming apparatus for a certain period of time, the amorphous resin particle dispersion preferably satisfies the following formulas (1-2) to (3-2), and more preferably satisfies the following formulas (1-3) to (3-3):

[0072] Formula (1-2): -0.01×A-0.25×B+9.5≦pH≦-0.01×A-0.25×B+10.0 Formula (2-2): 100nm≦A≦200nm Formula (3-2): 5mgKOH / g≦B≦15mgKOH / g

[0073] Formula (1-3): -0.01×A-0.25×B+9.5≦pH≦-0.01×A-0.25×B+9.8 Formula (2-3) 100nm≦A≦180nm Formula (3-3): 7mgKOH / g≦B≦15mgKOH / g (In the formulas (1-2) to (3-2) and (1-3) to (3-3), A is the particle size of the amorphous resin particles, B is the acid value of the amorphous resin, and pH is the pH of the amorphous resin particle dispersion.)

[0074] The particle size (A) of the amorphous resin particles is measured by the same procedure as that for measuring the volume average particle size of the polyester resin particles described above. The acid value (B) of the amorphous resin is measured in accordance with the method (potentiometric titration method) defined in JIS K0070-1992.

[0075] The pH of the amorphous resin particle dispersion is the pH when the temperature of the amorphous resin particle dispersion is 20°C. The pH of the amorphous resin particle dispersion is measured using a pH meter (for example, Seven2Go, manufactured by METTLER).

[0076] When the amorphous resin particle dispersion is added to the first aggregated particle dispersion two or more times, the particle size (A) of the amorphous resin particles, the acid value (B) of the amorphous resin, and the pH value of the amorphous resin particle dispersion are the arithmetic average values ​​of all the amorphous resin particle dispersions added to the first aggregated particle dispersion.

[0077] In the toner manufacturing method according to this embodiment, the pH of the amorphous resin particle dispersion is 3.0 or more and 6.5 or less. Here, the pH of the amorphous resin particle dispersion liquid has the same meaning as the pH of the amorphous resin particle dispersion liquid in the above formulas (1), (1-2), and (1-3), and the measurement method is also the same.

[0078] From the perspective of obtaining a toner that can suppress the occurrence of gloss unevenness when forming an image with high image density after continuously forming images in a high-temperature and high-humidity environment and then stopping the image forming apparatus for a certain period, the pH of the amorphous resin particle dispersion liquid is preferably 3.5 or more and 6.5 or less, more preferably 4.0 or more and 5.5 or less, and still more preferably 4.0 or more and 5.0 or less.

[0079] - Method of adding the amorphous resin particle dispersion liquid - In the second step, it is preferable to add the amorphous resin particle dispersion liquid to the first aggregated particle dispersion liquid two or more times, more preferably two to five times, still more preferably two or three times, and particularly preferably two times.

[0080] In the second step, by adding the amorphous resin particle dispersion liquid to the first aggregated particle dispersion liquid two or more times, the concentration of the amorphous resin particles in the dispersion liquid containing the first aggregated particles and the amorphous resin particles is reduced, and the aggregation of the amorphous resin particles with each other is more easily suppressed. Therefore, the generation of white spots is more suppressed. As a result, a toner manufacturing method can be obtained that can more suppress the occurrence of gloss unevenness when forming an image with high image density after continuously forming images in a high-temperature and high-humidity environment and then stopping the image forming apparatus for a certain period.

[0081] - Solid content concentration of the amorphous resin particle dispersion liquid - It is preferable that the solid content concentration of the amorphous resin particle dispersion liquid satisfies the following formula (4). Formula (4): The solid content concentration of the amorphous resin particle dispersion liquid added at the nth time < the solid content concentration of the amorphous resin particle dispersion liquid added at the (n + 1)th time (In formula (4), n is an integer of 1 or more)

[0082] The solid content concentration of the amorphous resin particle dispersion liquid refers to the content of the amorphous resin particles contained in the amorphous resin particle dispersion liquid relative to the mass of the amorphous resin particle dispersion liquid.

[0083] When the solids concentration of the amorphous resin particle dispersion satisfies the above formula (4), it becomes possible to gradually adhere the amorphous resin particles to the primary aggregate particles, which makes it easier to suppress the aggregation of the amorphous resin particles and further suppresses the occurrence of white particles.

[0084] It is preferable that the solid content concentration of the amorphous resin particle dispersion liquid satisfies the following formula (5). Equation (5): 2 mass%≦(solid content concentration of the amorphous resin particle dispersion liquid added the n+1th time)−(solid content concentration of the amorphous resin particle dispersion liquid added the nth time)≦20 mass% (In formula (5), n is an integer of 1 or more.)

[0085] When the solids concentration of the amorphous resin particle dispersion satisfies the above formula (5), a large increase in the concentration of the amorphous resin particles in the dispersion containing the first aggregated particles and the amorphous resin particles is suppressed, and the amorphous resin particles can be adhered to the first aggregated particles in a more stepwise manner, which further facilitates suppression of aggregation between the amorphous resin particles and further suppresses the occurrence of white particles.

[0086] From the viewpoint of providing a toner manufacturing method that can produce a toner that particularly suppresses the occurrence of uneven gloss when forming high-density images by continuously forming images under a high-temperature, high-humidity environment and then stopping the image forming apparatus for a certain period of time, it is more preferable that the solids concentration of the amorphous resin particle dispersion satisfy the following formula (5-2), and even more preferable that it satisfy the following formula (5-3).

[0087] Formula (5-2): 2 mass%≦(solid content concentration of the amorphous resin particle dispersion liquid added the n+1th time)−(solid content concentration of the amorphous resin particle dispersion liquid added the nth time)≦18 mass% Formula (5-3): 2 mass%≦(solids concentration of the amorphous resin particle dispersion liquid added the n+1th time)−(solids concentration of the amorphous resin particle dispersion liquid added the nth time)≦15 mass% (In formula (5-2) and formula (5-3), n is an integer of 1 or more.)

[0088] The solid content concentration of the amorphous resin particle dispersion is preferably 5% by mass or more and 40% by mass or less, more preferably 5% by mass or more and 35% by mass or less, and even more preferably 10% by mass or more and 35% by mass or less.

[0089] The pH of the first aggregated particle dispersion is preferably lower than the pH of the amorphous resin particle dispersion. When the pH of the first aggregate particle dispersion and the pH of the amorphous resin particle dispersion satisfy the above relationship, aggregation of the amorphous resin can be suppressed when the amorphous particles are added, adhesion to the surfaces of the primary particles becomes nearly uniform, and a toner manufacturing method can be obtained that further suppresses the occurrence of uneven gloss when images with high image density are formed by continuously forming images under a high-temperature and high-humidity environment and then stopping the image forming apparatus for a certain period of time.

[0090] (3rd step) The third step is a step of heating the second aggregated particle dispersion liquid in which the second aggregated particles are dispersed to fuse and coalesce the second aggregated particles. In the third step, 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 polyester resin particles and the amorphous 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), to fuse and coalesce the second aggregated particles and form toner particles. In the third step, the resins are in a fused state at a temperature equal to or higher than the glass transition temperature of the amorphous resin particles and the polyester resin particles, and then cooled to obtain toner particles.

[0091] The third step is carried out in a stirring vessel having an opening and containing the second flocculated particle dispersion, and the second flocculated particle dispersion is stirred at a rate of 5 L / (min m) per unit amount of the second flocculated particle dispersion in the stirring vessel. 3 It is preferable that the second aggregated particles are fused and coalesced in a state where a gas having a volume of at least 1000 ppm is blown.

[0092] When the second aggregate particle dispersion contains a low-molecular-weight compound, the aggregation of the white particles is likely to be promoted. By configuring the third step as the above step, the volatilization of the low-molecular-weight compound contained in the second aggregate particle dispersion is promoted and the aggregation of the white particles is suppressed, resulting in a toner manufacturing method that can obtain a toner that further suppresses the occurrence of uneven gloss when forming high-density images by stopping the image forming apparatus for a certain period of time after continuously forming images in a high-temperature, high-humidity environment.

[0093] The above air volume is 5 L / (min m) per unit volume of the second flocculated particle dispersion. 3 ) or more 150L / (min m 3 ) or less, and 10 L / (min m 3 ) or more 100L / (min m 3 ) or less, and 20 L / (min m 3 ) or more 100L / (min m 3 ) or less is particularly preferred.

[0094] Through the above steps, core-shell type toner particles are obtained.

[0095] After the third step is completed, the toner particles formed in the solution are subjected to a known washing step, solid-liquid separation step, and drying step to obtain dried toner particles. In the washing step, it is preferable to carry out sufficient replacement washing with ion-exchanged water from the viewpoint of electrostatic chargeability. Furthermore, the solid-liquid separation step is not particularly limited, but from the viewpoint of productivity, it is preferable to carry out suction filtration, pressure filtration, etc. Furthermore, in the drying step, there is no particular limitation on the method, but from the viewpoint of productivity, it is preferable to carry out freeze drying, flash drying, fluidized drying, vibration-type fluidized drying, etc.

[0096] The method for producing the toner for developing electrostatic images according to this exemplary embodiment preferably includes a step of externally adding an external additive to the obtained toner particles. The external addition may be carried out using, for example, a V blender, a Henschel mixer, a Loedige mixer, etc. Furthermore, if necessary, coarse particles of the toner may be removed using a vibrating sieve, an air sieve, etc.

[0097] Examples of the external additive used in the step of adding the external additive include inorganic particles described in the description of the external additives that may be contained in the toner, which will be described later.

[0098] <Toner for developing electrostatic images> Each component contained in the toner will be described in detail below. The toner according to this embodiment contains toner particles and, if necessary, an external additive.

[0099] The toner particles preferably contain a binder resin, a flat colorant, and, if necessary, a release agent, a colorant other than the flat colorant, and other additives.

[0100] (binder resin) The binder resin contains a polyester resin and an amorphous resin. The polyester resin and amorphous resin contained in the binder resin have the same meanings as the polyester resin and amorphous resin described above, and the preferred ranges are also the same.

[0101] The content of the binder resin is preferably 40% by mass to 95% by mass, more preferably 50% by mass to 90% by mass, and even more preferably 60% by mass to 85% by mass, based on the total mass of the toner particles.

[0102] (Flat color material) The flat color material contained in the toner particles has the same meaning as the flat color material described above, and the preferred range is also the same. The content of the bright pigment in the toner particles is, for example, 1% by mass to 50% by mass, 5% by mass to 50% by mass, or 10% by mass to 30% by mass, based on the total mass of the toner particles.

[0103] (mold release agent) The toner particles may optionally contain a release agent. Examples of release agents include hydrocarbon waxes, natural waxes such as carnauba wax, rice wax, and candelilla wax, synthetic or mineral / petroleum waxes such as montan wax, and ester waxes such as fatty acid esters and montanic acid esters, but are not limited thereto.

[0104] The melting temperature of the release agent is preferably 50°C or higher and 110°C or lower, and more preferably 60°C or higher and 100°C or lower. The melting temperature is determined from a DSC curve obtained by differential scanning calorimetry (DSC) by using the "melting peak temperature" as described in the method for determining the melting temperature in JIS K 7121-1987 "Method for measuring transition temperatures of plastics."

[0105] The content of the release agent is, for example, preferably 1% by mass or more and 20% by mass or less, and more preferably 5% by mass or more and 15% by mass or less, based on the total mass of the toner particles.

[0106] (Coloring agents other than flat coloring materials) The toner particles may contain a colorant other than the flat color material (hereinafter, also simply referred to as "colorant") as needed. 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 the like. Examples of the dye include various pigments such as phosphorus blue, chalco oil 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.

[0107] The colorant may be surface-treated as needed, or may be used in combination with a dispersant. Furthermore, a plurality of colorants may be used in combination.

[0108] The content of the colorant is, for example, preferably 1% by mass or more and 30% by mass or less, and more preferably 3% by mass or more and 15% by mass or less, based on the total mass of the toner particles.

[0109] -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.

[0110] -Characteristics of toner particles, etc.- The toner particles contained in the toner obtained by the toner production method according to this embodiment will be described in detail below. The toner particles according to this embodiment have a core-shell structure. The toner particles according to the present embodiment are preferably composed of, for example, a core containing a binder resin and a flat color material (and optionally other additives such as a colorant and a release agent), and a coating layer containing the binder resin.

[0111] The volume average particle size (D50v) of the toner particles is preferably 2 μm or more and 20 μm or less, and more preferably 4 μm or more and 15 μm or less.

[0112] The various average particle sizes and particle size distribution indices of the toner particles are measured using a Coulter Multisizer II (manufactured by Beckman Coulter), and the electrolyte is measured using an ISOTON-II (manufactured by Beckman Coulter). For the measurement, 0.5 mg to 50 mg of the sample to be measured is added to 2 ml of a 5% 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 solution containing the suspended sample is dispersed for 1 minute using an ultrasonic disperser, and the particle size distribution of particles with a particle size range of 2 μm to 60 μm is measured using a Coulter Multisizer II with an aperture diameter of 100 μm. The number of particles sampled is 50,000. Based on the particle size distribution measured, cumulative distributions of volume and number are drawn for each divided particle size range (channel) from the smallest diameter side, and the particle size at 16% of the cumulative total is defined as the volume particle size D16v, the number particle size D16p, the particle size at 50% of the cumulative total as the volume average particle size D50v, the cumulative number average particle size D50p, and the particle size at 84% of the cumulative total as the volume particle size D84v and the number particle size D84p. Using these, the volumetric particle size distribution index (GSDv) is (D84v / D16v) 1 / 2 , the number particle size distribution index (GSDp) is (D84p / D16p) 1 / 2 It is calculated as:

[0113] The average circularity of the toner particles is preferably 0.94 or more and 1.00 or less, and more preferably 0.95 or more and 0.98 or less.

[0114] The average circularity of toner particles is calculated by (circular equivalent perimeter) / (perimeter) [(perimeter of a circle having the same projected area as the particle image) / (perimeter of the particle projected image)]. Specifically, this value is measured by the following method. First, the toner particles to be measured are sucked and collected, forming a flat flow, and a still image of the particles is captured by instantaneously activating a strobe light, and the particle image is analyzed using a flow-type particle image analyzer (FPIA-3000 manufactured by Sysmex Corporation).The number of samples to be sampled when calculating the average circularity is 3,500. When the toner contains external additives, the toner (developer) to be measured is dispersed in water containing a surfactant, and then ultrasonic treatment is performed to obtain toner particles from which the external additives have been removed.

[0115] (external additives) Examples of external additives include inorganic particles such as SiO2, TiO2, Al2O3, CuO, ZnO, SnO2, CeO2, Fe2O3, MgO, BaO, CaO, KO, Na2O, ZrO2, CaO·SiO2, KO·(TiO2)n, Al2O3·2SiO2, CaCO3, MgCO3, BaSO4, and MgSO4.

[0116] The surfaces of inorganic particles as external additives are preferably subjected to a hydrophobic treatment. The hydrophobic treatment is carried out, 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 hydrophobic treatment agent is usually, for example, 1 part by mass or more and 10 parts by mass or less per 100 parts by mass of the inorganic particles.

[0117] 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 particles of fluorine-based polymers).

[0118] The amount of the external additive added is, for example, preferably 0.01% by mass or more and 5% by mass or less, and more preferably 0.01% by mass or more and 2.0% by mass or less, based on the toner particles.

[0119] <Electrostatic image developer> The electrostatic image developer according to this embodiment contains at least the toner according to this embodiment. The electrostatic image developer according to this embodiment may be a one-component developer containing only the toner according to this embodiment, or may be a two-component developer containing the toner mixed with a carrier.

[0120] The carrier is not particularly limited, and examples thereof include known carriers, such as coated carriers in which the surface of a core material made of magnetic powder is coated with a coating resin, magnetic powder dispersion carriers in which magnetic powder is dispersed and blended in a matrix resin, and resin-impregnated carriers 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.

[0121] Examples of magnetic powder include magnetic metals such as iron, nickel, and cobalt, and magnetic oxides such as ferrite and magnetite.

[0122] Examples of coating resins and matrix resins 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 resins containing organosiloxane bonds or modified products thereof, fluororesins, polyesters, polycarbonates, phenolic resins, and epoxy resins. The coating resin and the matrix resin may contain other additives such as conductive particles. Examples of 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.

[0123] Here, the method of coating the surface of the core material with a coating resin includes a method of coating with a solution for forming a coating layer, in which the coating resin and, if necessary, various additives are dissolved in an appropriate solvent. The solvent is not particularly limited and may be selected taking into consideration the coating resin to be used, its applicability, 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 the carrier and the solution for forming a coating layer are mixed in a kneader coater and the solvent is removed.

[0124] In the two-component developer, the mixing ratio (mass ratio) of toner to carrier is preferably toner:carrier=1:100 to 30:100, and more preferably 3:100 to 20:100.

[0125] <Image forming device / image forming method> An image forming apparatus and an 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 unit that charges the surface of the image carrier, an electrostatic image forming unit that forms an electrostatic image on the surface of the charged image carrier, a developing unit that contains an electrostatic image developer and develops the electrostatic image formed on the surface of the image carrier as a toner image using the electrostatic image developer, a transfer unit that transfers the toner image formed on the surface of the image carrier to the surface of a recording medium, and a fixing unit that fixes 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.

[0126] The image forming apparatus according to this embodiment carries out an image forming method (the image forming method according to this embodiment) that 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.

[0127] The image forming apparatus according to the present embodiment may be any of known image forming apparatuses, such as a direct transfer type apparatus that directly transfers a toner image formed on the surface of an image carrier to a recording medium; an intermediate transfer type apparatus that primarily transfers a toner image formed on the surface of an image carrier to the surface of an intermediate transfer medium, and then secondarily transfers the toner image transferred to the surface of the intermediate transfer medium to the surface of a recording medium; an apparatus equipped with a cleaning means that cleans the surface of the image carrier after the transfer of the toner image but before charging; and an apparatus equipped with a discharging means that irradiates the surface of the image carrier with discharging light to discharge it after the transfer of the toner image but before charging.

[0128] When the image forming apparatus according to the present embodiment is an apparatus of the intermediate transfer type, the transfer means is configured to have, for example, an intermediate transfer body onto whose surface a toner image is transferred, a primary transfer means for primarily transferring the toner image formed on the surface of the image carrier onto the surface of the intermediate transfer body, and a secondary transfer means for secondarily transferring the toner image transferred onto the surface of the intermediate transfer body onto the surface of the recording medium.

[0129] In the image forming apparatus according to the present embodiment, for example, the portion including the developing means may have a cartridge structure (process cartridge) that is detachably attached to the image forming apparatus. As the process cartridge, for example, a process cartridge that contains the electrostatic image developer according to the present embodiment and is equipped with the developing means is preferably used.

[0130] The image forming apparatus according to this embodiment may be a tandem type image forming apparatus in which an image forming unit that forms a glossy toner image (i.e., a toner image formed using the toner according to this embodiment) and at least one image forming unit that forms a toner image of a color other than the glossy color are arranged in parallel, or may be an image forming apparatus that is equipped only with an image forming unit that forms a glossy toner image.

[0131] 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. In the following description, the main parts shown in the drawings will be described, and the description of the rest will be omitted.

[0132] FIG. 1 is a schematic diagram showing the configuration of an image forming apparatus according to the present embodiment, and is a diagram showing a five-tandem type and intermediate transfer type image forming apparatus.

[0133] The image forming apparatus shown in Figure 1 includes first through fifth electrophotographic image forming units 10G, 10Y, 10M, 10C, and 10K (image forming means) that output images in each of the colors glitter (G), 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") 10G, 10Y, 10M, 10C, and 10K are arranged side by side horizontally spaced a predetermined distance apart from one another. These units 10G, 10Y, 10M, 10C, and 10K may be process cartridges that are detachably attached to the image forming apparatus.

[0134] An intermediate transfer belt (an example of an intermediate transfer body) 20 is provided below each of the units 10G, 10Y, 10M, 10C, and 10K and extends through each unit. The intermediate transfer belt 20 is provided wrapped around a drive roll 22, a support roll 23, and an opposing roll 24, which are in contact with the inner surface of the intermediate transfer belt 20, and runs in a direction from the first unit 10G to the fifth unit 10K. An intermediate transfer body cleaning device 21 is provided on the image bearing surface side of the intermediate transfer belt 20, facing the drive roll 22.

[0135] The developing devices (examples of developing means) 4G, 4Y, 4M, 4C, and 4K of each unit 10G, 10Y, 10M, 10C, and 10K are supplied with photoluminescent, yellow, magenta, cyan, and black toner contained in toner cartridges 8G, 8Y, 8M, 8C, and 8K, respectively.

[0136] Since the first to fifth units 10G, 10Y, 10M, 10C, and 10K have the same configuration and operation, we will explain here the first unit 10G, which forms a glossy image and is arranged upstream in the direction of travel of the intermediate transfer belt.

[0137] The first unit 10G has a photoconductor 1G that acts as an image carrier. Around the photoconductor 1G, there are arranged in this order: a charging roll (an example of a charging means) 2G that charges the surface of the photoconductor 1G to a predetermined potential; an exposure device (an example of an electrostatic image forming means) 3G that exposes the charged surface to a laser beam based on a color-separated image signal to form an electrostatic image; a developing device (an example of a developing means) 4G that supplies toner to the electrostatic image to develop it; a primary transfer roll (an example of a primary transfer means) 5G that transfers the developed toner image onto the intermediate transfer belt 20; and a photoconductor cleaning device (an example of a cleaning means) 6G that removes toner remaining on the surface of the photoconductor 1G after the primary transfer.

[0138] The primary transfer roll 5G is disposed inside the intermediate transfer belt 20 and is positioned opposite the photoconductor 1G. A bias power supply (not shown) that applies a primary transfer bias is connected to the primary transfer rolls 5G, 5Y, 5M, 5C, and 5K of each unit. Each bias power supply changes the value of the transfer bias applied to each primary transfer roll under the control of a control unit (not shown).

[0139] The operation of forming a lustrous image in the first unit 10G will be described below. First, prior to operation, the surface of the photosensitive member 1G is charged to a potential of -600V to -800V by the charging roll 2G. The photoconductor 1G is conductive (for example, the volume resistivity at 20°C is 1×10 -6 The photosensitive layer is formed by laminating a photosensitive layer on a substrate with a resistivity of Ωcm or less. This photosensitive layer is normally highly resistive (the resistance of ordinary resins), but when irradiated with a laser beam, the resistivity of the irradiated portion changes. Therefore, a laser beam is irradiated onto the charged surface of the photosensitive drum 1G from an exposure device 3G in accordance with image data for glitter sent from a control unit (not shown). This forms an electrostatic charge image of a glitter image pattern on the surface of the photosensitive drum 1G.

[0140] An electrostatic image is an image formed on the surface of the photosensitive element 1G by charging it; it is a so-called negative latent image formed when the resistivity of the irradiated portion of the photosensitive layer is reduced by the laser beam from the exposure device 3G, causing the charged charges on the surface of the photosensitive element 1G to flow, while the charges remain in the portions not irradiated by the laser beam. The electrostatic image formed on the photoreceptor 1G rotates to a predetermined development position as the photoreceptor 1G moves, where the electrostatic image on the photoreceptor 1G is developed into a toner image by the developing device 4G and made visible.

[0141] The developing device 4G contains an electrostatic image developer containing, for example, at least a photoluminescent toner (i.e., the toner according to this embodiment) and a carrier. The photoluminescent toner is frictionally charged by stirring inside the developing device 4G 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 photoreceptor 1G. As the surface of the photoreceptor 1G passes through the developing device 4G, the photoluminescent toner electrostatically adheres to the discharged latent image portion on the surface of the photoreceptor 1G, and the latent image is developed with the photoluminescent toner. The photoreceptor 1G on which the photoluminescent toner image has been formed continues to travel at a predetermined speed, and the toner image developed on the photoreceptor 1G is transported to a predetermined primary transfer position.

[0142] When the glossy toner image on the photoreceptor 1G is transported to the primary transfer position, a primary transfer bias is applied to the primary transfer roll 5G, and an electrostatic force from the photoreceptor 1G toward the primary transfer roll 5G acts on the toner image, causing the toner image on the photoreceptor 1G to be transferred onto the intermediate transfer belt 20. The transfer bias applied at this time has a (+) polarity opposite to the (-) polarity of the toner, and is controlled by a control unit (not shown) in the first unit 10G to, for example, +10 μA. On the other hand, the toner remaining on the photoreceptor 1G is removed and collected by the photoreceptor cleaning device 6G.

[0143] The primary transfer bias applied to the primary transfer rolls 5Y, 5M, 5C, and 5K of the second unit 10Y and subsequent units is also controlled in accordance with the first unit. In this way, the intermediate transfer belt 20 onto which the glossy toner image has been transferred in the first unit 10G is transported sequentially through the second to fifth units 10Y, 10M, 10C, and 10K, where the toner images of each color are superimposed and transferred.

[0144] The intermediate transfer belt 20, onto which the five-color toner images have been multiplex-transferred through the first to fifth units, reaches a secondary transfer section composed of the intermediate transfer belt 20, an opposing roll 24 in contact with 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, recording paper (an example of a recording medium) P is fed via a supply mechanism into the gap between the secondary transfer roll 26 and the intermediate transfer belt 20 at a predetermined timing, and a secondary transfer bias is applied to the opposing roll 24. The transfer bias applied at this time has a negative polarity, the same as the negative polarity of the toner. Electrostatic force from the intermediate transfer belt 20 toward the recording paper P acts on the toner image, transferring the toner image on the intermediate transfer belt 20 onto the recording paper P. The secondary transfer bias at this time is determined based on resistance detected by resistance detection means (not shown) that detects resistance in the secondary transfer section, and is voltage-controlled.

[0145] Thereafter, the recording paper P is sent to a pressure contact portion (nip portion) of a pair of fixing rolls in a fixing device (an example of fixing means) 28, where the toner image is fixed onto the recording paper P, forming a fixed image.

[0146] Examples of the recording paper P onto which the toner image is transferred include plain paper used in electrophotographic copiers, printers, etc. In addition to the recording paper P, examples of the recording medium include overhead projector sheets and the like. To further improve the smoothness of the image surface after fixing, it is preferable that the surface of the recording paper P is also smooth. For example, coated paper in which the surface of plain paper is coated with resin or the like, or art paper for printing, etc., is preferably used.

[0147] The recording paper P on which the color image has been fixed is conveyed toward the discharge section, and the series of color image forming operations is completed.

[0148] <Process cartridges / toner cartridges> The process cartridge according to this embodiment will be described. The process cartridge according to this embodiment is a process cartridge that is detachably attached to an image forming apparatus and that contains the electrostatic image developer according to this embodiment and 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.

[0149] The process cartridge according to this embodiment is not limited to the above configuration, but may also be configured to include a developing device and, if necessary, at least one other means selected from an image carrier, a charging means, an electrostatic image forming means, and a transfer means.

[0150] An example of a process cartridge 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 other parts will be omitted.

[0151] FIG. 2 is a schematic diagram showing the configuration of the process cartridge according to the present embodiment. The process cartridge 200 shown in FIG. 2 is configured to integrally combine and hold a photosensitive member 107 (an example of an image carrier), a charging roll 108 (an example of a charging means) provided around the photosensitive member 107, a developing device 111 (an example of a developing means), and a photosensitive member cleaning device 113 (an example of a cleaning means), which are held by a housing 117 provided with, for example, mounting rails 116 and an opening 118 for exposure, and is made 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).

[0152] 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.

[0153] 1 is an image forming apparatus having a configuration in which toner cartridges 8Y, 8M, 8C, and 8K can be attached and detached, and developing devices 4Y, 4M, 4C, and 4K are connected to the toner cartridges corresponding to each developing device (color) by toner supply pipes (not shown). When the toner stored in a toner cartridge runs low, the toner cartridge is replaced. [Example]

[0154] Examples will be described below, but the present invention is not limited to these examples. In the following description, unless otherwise specified, all "parts" and "%" are by mass.

[0155] <Dispersion liquid preparation process> (Preparation of Amorphous Resin Particle Dispersion) (Preparation of amorphous resin particle dispersion 1) Terephthalic acid: 30 parts by mole Fumaric acid: 70 parts by mole Bisphenol A ethylene oxide adduct: 5 parts by mole Bisphenol A propylene oxide adduct: 95 parts by mole The above materials were placed in a flask equipped with a stirrer, a nitrogen inlet tube, a temperature sensor, and a distillation column, and the temperature was raised to 220°C over 1 hour, followed by adding 1 part of titanium tetraethoxide per 100 parts of the above materials. The temperature was raised to 230°C over 30 minutes while distilling off the generated water, and the dehydration condensation reaction was continued at that temperature for 1 hour. The reaction product was then cooled to obtain an amorphous polyester resin (weight average molecular weight 18,000, glass transition temperature 59°C). A container equipped with a temperature control device and a nitrogen purge device was charged with 40 parts of methyl ethyl ketone and 25 parts of 2-butanol to prepare a mixed solvent, and then 100 parts of amorphous polyester resin was gradually added and dissolved. 5 parts of anionic surfactant (Neogen RK, manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.) was added and stirred for 30 minutes. The atmosphere inside the container was then purged with dry nitrogen, the temperature was maintained at 40°C, and 800 parts of ion-exchanged water was added dropwise to the stirred mixture to emulsify it. After the addition was completed, the emulsion was returned to 25°C, yielding a resin particle dispersion containing dispersed resin particles with a volume average particle size of 180 nm. Ion-exchanged water was added to this resin particle dispersion to adjust the solids concentration to 40%, yielding Amorphous Resin Particle Dispersion 1.

[0156] (Preparation of amorphous resin particle dispersion 2) A mixed solvent was prepared by adding 60 parts of methyl ethyl ketone and 37 parts of 2-butanol to the amorphous polyester resin obtained by the procedure described for Amorphous Resin Particle Dispersion 1. Then, 100 parts of the amorphous polyester resin was gradually added and dissolved. 5 parts of anionic surfactant (Neogen RK, manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.) was added and stirred for 30 minutes. The atmosphere inside the vessel was then purged with dry nitrogen, the temperature was maintained at 40°C, and 800 parts of ion-exchanged water was added dropwise to the stirred mixture to emulsify it. After the addition, the emulsion was returned to 25°C, yielding a resin particle dispersion containing dispersed resin particles with a volume average particle size of 100 nm. Ion-exchanged water was added to this resin particle dispersion to adjust the solids concentration to 40%, yielding Amorphous Resin Particle Dispersion 2.

[0157] (Preparation of Amorphous Resin Particle Dispersion 3) Amorphous resin 3 having a volume average particle size of 90 nm and a solid content of 40% was obtained in the same manner as in preparation of amorphous resin dispersion 2, except that the amount of 2-butanol added was changed to 39 parts.

[0158] (Preparation of amorphous resin particle dispersion 4) Amorphous resin 4 having a volume average particle size of 250 nm and a solid content of 40% was obtained in the same manner as in the preparation of amorphous resin dispersion 2, except that the amounts of methyl ethyl ketone and 2-butanol added were changed to 35 parts of methyl ethyl ketone and 24 parts of 2-butanol.

[0159] (Preparation of Amorphous Resin Particle Dispersion 5) Amorphous resin 5 having a volume average particle size of 260 nm and a solid content concentration of 40% was obtained in the same manner as in the preparation of amorphous resin dispersion 2, except that the amounts of methyl ethyl ketone and 2-butanol added were changed to 34 parts of methyl ethyl ketone and 22 parts of 2-butanol.

[0160] (Preparation of amorphous resin dispersion 6) Amorphous resin dispersion liquid 1 having a volume average particle size of 226 nm and a solids concentration of 40% was prepared by the same procedure as in preparation of amorphous resin dispersion liquid 1, except that the amount of fumaric acid charged in the flask equipped with a stirrer, nitrogen inlet tube, temperature sensor, and rectification column was changed from 70 molar parts to 50 molar parts, and 20 molar parts of ethylene glycol were added to the flask equipped with a stirrer, nitrogen inlet tube, temperature sensor, and rectification column in addition to terephthalic acid, fumaric acid, bisphenol A ethylene oxide adduct, and bisphenol A propylene oxide adduct. Amorphous polyester resin (weight average molecular weight: 19,500, glass transition temperature: 61° C.) dispersion liquid 6 was obtained.

[0161] (Preparation of amorphous resin dispersion 7) Amorphous polyester resin dispersion 7 (weight average molecular weight 19,600, glass transition temperature 60°C) having a volume average particle size of 225 nm and a solids concentration of 40% was obtained in the same manner as in the preparation of amorphous resin dispersion 1, except that the amount of fumaric acid charged into a flask equipped with a stirrer, a nitrogen inlet tube, a temperature sensor, and a rectification column was changed from 70 molar parts to 45 molar parts, and 25 molar parts of ethylene glycol were added to the flask equipped with a stirrer, a nitrogen inlet tube, a temperature sensor, and a rectification column in addition to terephthalic acid, fumaric acid, bisphenol A ethylene oxide adduct, and bisphenol A propylene oxide adduct.

[0162] (Preparation of amorphous resin dispersion 8) Amorphous polyester resin dispersion 8 (weight average molecular weight 18,000, glass transition temperature 60°C) having a volume average particle size of 113 nm and a solids concentration of 40% was obtained in the same procedure as in preparation of amorphous resin dispersion 1, except that the amount of fumaric acid charged into a flask equipped with a stirrer, a nitrogen inlet tube, a temperature sensor, and a rectification column was changed from 70 molar parts to 55 molar parts, and 15 molar parts of trimellitic acid were added to the flask equipped with a stirrer, a nitrogen inlet tube, a temperature sensor, and a rectification column in addition to terephthalic acid, fumaric acid, bisphenol A ethylene oxide adduct, and bisphenol A propylene oxide adduct.

[0163] (Preparation of amorphous resin dispersion 9) Amorphous polyester resin dispersion 8 (weight average molecular weight 18,000, glass transition temperature 60°C) having a volume average particle size of resin particles of 112 nm and a solids concentration of 40% was obtained in the same procedure as in preparation of amorphous resin dispersion 1, except that the amount of fumaric acid charged into a flask equipped with a stirrer, a nitrogen inlet tube, a temperature sensor, and a rectification column was changed from 70 molar parts to 50 molar parts, and 20 molar parts of trimellitic acid were added to the flask equipped with a stirrer, a nitrogen inlet tube, a temperature sensor, and a rectification column in addition to terephthalic acid, fumaric acid, bisphenol A ethylene oxide adduct, and bisphenol A propylene oxide adduct.

[0164] Table 1 shows the particle size, acid value of the amorphous resin, and pH of each of the amorphous resin particle dispersions.

[0165] (Preparation of Crystalline Polyester Resin Particle Dispersion) Decanedioic acid: 81 parts Hexanediol: 47 parts The above materials were charged into a flask, and the temperature was raised to 160°C over 1 hour. After confirming that the reaction system was uniformly stirred, 0.03 parts of dibutyltin oxide was added. The temperature was raised to 200°C over 6 hours while distilling off the produced water, and stirring was continued at 200°C for 4 hours. The reaction liquid was then cooled, solid-liquid separation was performed, and the solid was dried at 40°C under reduced pressure to obtain a crystalline polyester resin (weight average molecular weight 15,000, melting point 64°C). 50 parts of crystalline polyester resin, 2 parts of anionic surfactant (Neogen RK, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.), and 200 parts of ion-exchanged water were mixed, heated to 120°C, and thoroughly dispersed using a homogenizer (Ultra-Turrax T50, manufactured by IKA Corporation), followed by a dispersion treatment using a pressure discharge homogenizer. When the volume average particle size reached 180 nm, the particles were collected to obtain a crystalline polyester resin particle dispersion with a solids content of 20%.

[0166] (Preparation of colorant dispersion) Aluminum pigment (Toyo Aluminum 2173EA): 100 parts Anionic surfactant (Neogen R manufactured by Daiichi Kogyo Seiyaku Co., Ltd.): 1.5 parts Ion-exchanged water: 900 parts After removing the solvent from the aluminum pigment paste, the above materials were mixed and dispersed for 1 hour using a Cavitron emulsifying disperser (CR1010 manufactured by Pacific Machinery Works, Ltd.) to obtain a colorant dispersion liquid with a solid content of 10% in which the luster pigment (aluminum pigment) was dispersed.

[0167] (Preparation of Release Agent Particle Dispersion) Paraffin wax (manufactured by Nippon Seiro Co., Ltd., FNP92, endothermic peak onset 81°C): 45 parts Anionic surfactant (Dai-ichi Kogyo Seiyaku Co., Ltd., Neogen RK): 5 parts Ion-exchanged water: 200 parts The above ingredients were mixed and heated to 95°C, and dispersed using a homogenizer (Ultra Turrax T50, manufactured by IKA). After that, a dispersion treatment was carried out using a Manton-Gaulin high-pressure homogenizer (Gaulin), and a release agent particle dispersion liquid (solid content concentration: 20%) in which the release agent was dispersed was prepared. The volume average particle size of the release agent particles was 0.19 μm.

[0168] Example 1

[0169] (1st step) Ion-exchanged water: 500 parts ·Amorphous resin particle dispersion 1: 170 parts Crystalline polyester resin particle dispersion: 100 parts Release agent particle dispersion: 25 parts ·Coloring material particle dispersion: 50 parts Anionic surfactant (TaycaPower): 3.0 parts The above materials (hereinafter also referred to as "charged materials") were placed in a jacket temperature-controlled stirring tank, and then stirred for 5 minutes (hereinafter also referred to as "dispersion stirring time"). After adjusting the pH to 3.5 by adding a 0.1 N aqueous nitric acid solution, an aqueous polyaluminum chloride solution prepared by dissolving 2 parts of polyaluminum chloride (30% powder product, manufactured by Oji Paper Co., Ltd.) in 30 parts of ion-exchanged water was added. After a dispersion treatment using a homogenizer, the mixture was heated to 45°C and maintained until the number average particle size reached 4.6 μm, thereby obtaining a first aggregate particle dispersion liquid in which the first aggregate particles were dispersed.

[0170] (2nd process) For the first addition of amorphous resin particle dispersion, 100 parts of amorphous resin particle dispersion 1, the pH of which had been adjusted to 4.6 and the solid content concentration of which had been adjusted to 15% by mass, was added to the stirring tank and held for 30 minutes. Next, for the second addition of amorphous resin particle dispersion, 100 parts of amorphous resin particle dispersion 1, the pH of which had been adjusted to 4.8 and the solid content concentration of which had been adjusted to 30% by mass, was added to the stirring tank and held for 30 minutes, to obtain a second aggregated particle dispersion in which the second aggregated particles were dispersed.

[0171] (3rd step) 20 parts of a 10% NTA (nitrilotriacetic acid) metal salt aqueous solution (Chilest 70, manufactured by Chelest Co., Ltd.) was added to a stirring tank, and a 1N aqueous sodium hydroxide solution was added to adjust the pH to 9.0. Next, 1 part of an anionic surfactant (TaycaPower) was added, and the mixture was heated to 85°C with continued stirring and maintained at this temperature for 5 hours. The mixture was then cooled to 20°C at a rate of 20°C / min, yielding a toner particle dispersion liquid containing dispersed toner particles. The third step is carried out in a stirring vessel having an opening, and the flow rate per unit amount of the second aggregate particle dispersion in the stirring vessel is 15 L / (min m 3 The test was carried out with a gas (air) flow rate of 1000 psi.

[0172] (Cleaning process, etc.) Then, the mixture was sieved through a 20 μm mesh, washed repeatedly with water, and then dried in a vacuum dryer to obtain toner particles.

[0173] (External addition of external additives) 100 parts of toner particles and 1.5 parts of hydrophobic silica (RY50 manufactured by Nippon Aerosil Co., Ltd.) were mixed using a sample mill at a rotation speed of 10,000 rpm for 30 seconds. The mixture was then sieved using a vibrating sieve with 45 μm openings to obtain a toner. The volume average particle diameter of the obtained toner was 11.2 μm.

[0174] (Carrier production) 500 parts of spherical magnetite powder particles (volume average particle diameter: 0.55 μm) were thoroughly stirred in a Henschel mixer, and then 5.0 parts of a titanate coupling agent were added, 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% aqueous ammonia, and 425 parts of water were mixed and stirred in a four-neck flask. After reacting for 120 minutes at 85°C with stirring, the mixture was cooled to 25°C, 500 parts of water was added, the supernatant 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.

[0175] (Preparation of electrostatic image developer) The obtained carrier and toner were placed in a V blender in a ratio of toner:carrier=5:95 (mass ratio), and stirred for 20 minutes to obtain an electrostatic image developer.

[0176] <Examples 2 to 24, Comparative Examples 1 and 2> An electrostatic image developer was obtained in the same manner as in Example 1, except that the conditions for (first step), (second step), and (third step) were changed as shown in Table 1. Example 25 An electrostatic image developer was obtained in the same manner as in Example 1, except that in the materials charged in the first step, 5 parts of aluminum pigment (2173EA manufactured by Toyo Aluminum Co., Ltd.) was added instead of 50 parts of the colorant particle dispersion.

[0177] <Gloss Unevenness Evaluation> A "700 Digital Color Press" manufactured by Fujifilm Business Innovation Co., Ltd. was prepared as an image forming apparatus, and the developer obtained in each Example and Comparative Example was filled into its developing device. 50,000 images with a solid image density of 5% were printed on OK topcoat paper (basis weight 127) in an environment of 10°C and 20% RH. With the image forming apparatus stopped, the environment was changed overnight from 10°C, 20% RH to 25°C, 60% RH. Five copies of the same image were printed, and a goniophotometer (Nippon Denshoku Industries Co., Ltd., spectral variable angle color difference meter GC5000L) was used to measure the reflectance X at a receiving angle of +30° and the reflectance Y at a receiving angle of -30° for each image, with incident light at an incident angle of -45° for the solid image. The arithmetic mean value of the reflectance X for each image and the arithmetic mean value of the reflectance Y for each image were calculated. The reflectance X and reflectance Y were measured at 20 nm intervals for light with wavelengths ranging from 400 nm to 700 nm, and the average reflectance values ​​at each wavelength were used. Table 1 shows the value obtained by dividing the arithmetic mean value of reflectance X by the arithmetic mean value of reflectance Y (arithmetic mean value of reflectance X ÷ arithmetic mean value of reflectance Y; hereinafter also referred to as "ratio (X / Y)"). The higher the ratio (X / Y), the smaller the gloss unevenness, and the lower the ratio (X / Y), the greater the gloss unevenness.

[0178] [Table 1-1]

[0179] [Table 1-2]

[0180] In Table 1, "Difference in solid content concentration (second addition - first addition) (mass %)" represents the value of (solid content concentration of the amorphous resin particle dispersion liquid added the second time) - (solid content concentration of the amorphous resin particle dispersion liquid added the second time). In Table 1, the description "Whether or not the stirring tank has an opening" indicates whether or not the stirring tank used in Step 3 has an opening. If the stirring tank has an opening, it is written as "Yes," and if the stirring tank does not have an opening, it is written as "No." The "Air volume (L / (min·m3))" in Table 1 represents the volume of gas blown per unit amount of the second flocculated particle dispersion in the stirring tank. In Table 1, "Colorant Addition Method" indicates whether the flat colorant is added as a colorant particle dispersion or as an aluminum pigment in the materials charged in the first step. In the examples marked "Dispersion," the materials charged in the first step contain a colorant particle dispersion. On the other hand, in the examples marked "Pigment," the materials charged in the first step do not contain a colorant particle dispersion, and the aluminum pigment is added as is.

[0181] From the above results, it can be seen that the toner manufacturing method of this embodiment can produce a toner that suppresses the occurrence of gloss unevenness when forming high-density images by stopping the image forming apparatus for a certain period of time after continuously forming images in a high-temperature, high-humidity environment. [Explanation of symbols]

[0182] 1G, 1Y, 1M, 1C, 1K Photoconductor (an example of an image carrier) 2G, 2Y, 2M, 2C, 2K Charging roll (an example of charging means) 3G, 3Y, 3M, 3C, 3K exposure equipment (an example of electrostatic image forming means) 4G, 4Y, 4M, 4C, 4K developing device (an example of developing means) 5G, 5Y, 5M, 5C, 5K Primary transfer roll (an example of a primary transfer means) 6G, 6Y, 6M, 6C, 6K Photoconductor cleaning device (an example of a cleaning means) 8G, 8Y, 8M, 8C, 8K toner cartridges 10G, 10Y, 10M, 10C, 10K Image Formation Unit 20 Intermediate transfer belt (an example of an intermediate transfer body) 21 Intermediate transfer body cleaning device 22 Drive Roll 23 Support Roll 24 opposing roll 26 Secondary transfer roll (an example of a secondary transfer means) 28 Fixing device (an example of fixing means) P Recording paper (an example of a recording medium)

[0183] 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 transfer means) 113 Photosensitive drum cleaning device (an example of cleaning means) 115 Fixing device (an example of fixing means) 116 Mounting Rail 117 Cabinet 118 Exposure opening 200 Process Cartridge 300 Recording paper (an example of a recording medium)

Claims

1. a first step of aggregating polyester resin particles and a flat colorant to prepare a first aggregate particle dispersion liquid in which first aggregate particles having a number average particle size of 1 μm or more are dispersed; a second step of adding an amorphous resin particle dispersion liquid dispersing amorphous resin particles to the first aggregated particle dispersion liquid two or more times to cause the amorphous resin particles to adhere to the first aggregated particles, thereby obtaining second aggregated particles; a third step of heating the second aggregate particle dispersion liquid in which the second aggregate particles are dispersed to fuse and coalesce the second aggregate particles, the amorphous resin particle dispersion liquid satisfies the following formulas (1) to (3), The method for producing a toner for developing electrostatic images, wherein the solid content concentration of the amorphous resin particle dispersion liquid satisfies the following formula (4): Formula (1): -0.01×A-0.25×B+9.2≦pH≦-0.01×A-0.25×B+10.0 Formula (2): 100nm≦A≦250nm Formula (3): 5mgKOH / g≦B≦20mgKOH / g (In the formulas (1) to (3), A is the particle size of the amorphous resin particles, B is the acid value of the amorphous resin, and pH is the pH of the amorphous resin particle dispersion liquid.) Formula (4): Solid content concentration of the amorphous resin particle dispersion liquid added for the nth time<Solid content concentration of the amorphous resin particle dispersion liquid added for the n+1th time (In formula (4), n is an integer of 1 or more)

2. a first step of preparing a first aggregate particle dispersion liquid in which polyester resin particles and a flat colorant are aggregated to disperse first aggregate particles having a number average particle size of 1 μm or more; a second step of adding an amorphous resin particle dispersion liquid dispersing amorphous resin particles to the first aggregated particle dispersion liquid two or more times to cause the amorphous resin particles to adhere to the first aggregated particles, thereby obtaining second aggregated particles; a third step of heating the second aggregate particle dispersion liquid in which the second aggregate particles are dispersed to fuse and coalesce the second aggregate particles, the pH of the amorphous resin particle dispersion is 3.0 or more and 6.5 or less, The method for producing a toner for developing electrostatic images, wherein the solid content concentration of the amorphous resin particle dispersion liquid satisfies the following formula (4): Formula (4): Solid content concentration of the amorphous resin particle dispersion liquid added for the nth time<Solid content concentration of the amorphous resin particle dispersion liquid added for the n+1th time (In formula (4), n is an integer of 1 or more)

3. 3. The method for producing a toner for developing electrostatic images according to claim 1, wherein in the first step, before the polyester resin particles and the flat colorant are aggregated, a dispersion liquid in which the polyester resin particles and the flat colorant are dispersed is stirred with a stirring blade.

4. 4. The method for producing a toner for developing electrostatic images according to claim 1, wherein the solid content concentration of the amorphous resin particle dispersion liquid satisfies the following formula (5): Formula (5): 2 mass%≦(solid content concentration of the amorphous resin particle dispersion liquid added for the (n+1)th time)−(solid content concentration of the amorphous resin particle dispersion liquid added for the (n)th time)≦20 mass% (In formula (5), n is an integer of 1 or more)

5. 5. The method for producing a toner for developing electrostatic images according to claim 1, wherein the pH of the first aggregated particle dispersion is lower than the pH of the amorphous resin particle dispersion.

6. the third step is carried out in a stirring tank having an opening and containing the second aggregate particle dispersion, 5 L / (min m) per unit amount of the second aggregate particle dispersion in the stirring tank ３ 6. The method for producing a toner for developing electrostatic images according to claim 1, wherein the second aggregated particles are fused and coalesced in a state where a gas having a volume of at least 1000 ppm is blown into the toner.

7. The air volume is 5 L / (min m) per unit amount of the second aggregate particle dispersion liquid in the stirring tank. ３ ) or more 150L / (min・m ３ 7. The method for producing a toner for developing electrostatic images according to claim 6, wherein the toner is 0.1 or less.

8. 8. The method for producing a toner for developing an electrostatic image according to claim 1, further comprising, before the first step, a step of stirring a flat colorant, a surfactant, and a dispersion medium to obtain a colorant dispersion liquid.

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