Method for producing a pigment dispersion, and method for producing a toner for developing electrostatic images.

Abstract

To provide a method for producing a pigment dispersion which has high pigment dispersibility and suppresses clogging of a screen-type media separator of a media dispersion machine by a flame retardant.SOLUTION: There is provided a method for producing a pigment dispersion which comprises a first step of wet-dispersing a mixture A containing an organic pigment, a flame retardant, a dispersing agent and an aqueous medium using a media disperser to obtain a mixture B and a second step of wet-dispersing the mixture B using the media disperser to obtain a mixture C, wherein the media disperser in the first and second steps is an annular-type media disperser which has a cylindrical vessel, a cylindrical rotor which is installed inside the cylindrical vessel and rotates to disperse the mixture and a screen-type media separation part for separating media particles and the mixture and the number average particle diameters MA and MB of the media particles in the media dispersers in the first and second steps satisfy the expressions (1) and (2): Expression (1): 0.5 mm≥MA>MB≥0.05 mm and Expression (2): 0.3 mm≥MB≥0.05 mm.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a method for producing a pigment dispersion liquid and a method for producing an electrostatic charge image developing toner.

Background Art

[0002] For example, Patent Document 1 discloses "a method for producing a paste for a color filter in which a colorant is dispersed in multiple stages using a media stirring type disperser, wherein the diameter of the media in each stage is sequentially decreased and the dispersion is performed in a circulation manner."

[0003] Further, Patent Document 2 discloses "a method for producing a coloring material for a color filter including a pigment, a pigment derivative, and a liquid medium, which is a vertical type and has a rotor and a vessel, and is an annular type wet disperser equipped with a media separation mechanism by screenless centrifugation, and includes a step (A) of dispersing a pigment composition including a pigment, a pigment derivative, and a liquid medium using media with a particle diameter of 0.005 mmφ to 0.05 mmφ."

[0004] Further, Patent Document 3 discloses "a method for producing a polymer toner including a step 1 of preparing a polymerizable monomer composition containing a polymerizable monomer and a colorant, a step 2 of dispersing the polymerizable monomer composition in an aqueous dispersion medium to form droplets, and a step 3 of polymerizing the droplets to form colored resin particles, wherein the step 1 includes a dispersion step of supplying a mixed liquid containing a polymerizable monomer and a colorant to a media type disperser equipped with media particles and a media separation screen and dispersing the colorant in the mixed liquid."

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

[0006] The object of the present invention is to provide a method for producing a pigment dispersion, comprising a first step of wet dispersing a mixture A containing an organic pigment, a flame retardant, a dispersant, and an aqueous medium using a media disperser to obtain a mixture B, and a second step of wet dispersing the mixture B using a media disperser to obtain a mixture C, wherein the media disperser in the first and second steps is an annular media disperser having a cylindrical vessel, a cylindrical rotor provided inside the cylindrical vessel that rotates to disperse the mixture, and a screen-type media separation unit that separates media particles from the mixture, and the present invention provides a method for producing a pigment dispersion in which the dispersibility of the pigment is higher and clogging of the screen-type media separation unit of the media disperser by the flame retardant is suppressed compared to the case in which the number average particle size MA of the media particles of the media disperser in the first step and the number average particle size MB of the media particles of the media disperser in the second step do not satisfy the following formulas (1) and (2). [Means for solving the problem]

[0007] The following embodiments are included as specific means for solving the aforementioned problems. <1> The first step involves wet-dispersing mixture A, which contains an organic pigment, a flame retardant, a dispersant, and an aqueous medium, using a media disperser to obtain mixture B. The second step involves wet-dispersing the aforementioned mixture B using a media disperser to obtain mixture C, It has, The media disperser in the first and second steps is an annular media disperser having a cylindrical vessel, a cylindrical rotor provided inside the cylindrical vessel and rotating to disperse the mixture, and a screen-type media separation unit for separating media particles from the mixture. A method for producing a pigment dispersion, wherein the number-average particle size MA of the media particles in the media disperser in the first step and the number-average particle size MB of the media particles in the media disperser in the second step satisfy the following formulas (1) and (2). Formula (1): 0.5mm≧MA>MB≧0.05mm Formula (2): 0.3mm≧MB≧0.05mm <2> The number-average particle size MA of the media particles in the media disperser in the first step and the number-average particle size MB of the media particles in the media disperser in the second step satisfy the following equations (11) and (21). <1> A method for producing the pigment dispersion described above. Formula (11): 0.4mm≧MA>MB≧0.1mm Formula (21): 0.2mm≧MB≧0.1mm <3> The number-average particle size MA of the media particles in the media disperser in the first step and the number-average particle size MB of the media particles in the media disperser in the second step satisfy the following equation (3) <1> or <2> A method for producing the pigment dispersion described above. Formula (3): 0.45mm≧MA-MB≧0.05mm <4> The number-average particle size MA of the media particles in the media disperser in the first step and the number-average particle size MB of the media particles in the media disperser in the second step satisfy the following equation (31) <3> A method for producing the pigment dispersion described above. Formula (31): 0.3mm≧MA-MB>≧0.1mm <5> The flame retardant is a metal hydroxide. <1> ~ <4> A method for producing a pigment dispersion according to any one of the items. <6> In the first and second steps, the mesh opening of the screen-type media separation section of the media disperser is 1 / 3 or more and 1 / 2 or less in ratio to the number-average particle size of the media particles in the media disperser. <1> ~ <5> A method for producing a pigment dispersion according to any one of the items. <7> In the first and second steps, the inner diameter BD of the cylindrical vessel and the outer diameter RD of the cylindrical rotor of the media disperser satisfy the following equation (4): <1> ~ <6> A method for producing a pigment dispersion according to any one of the items. Formula (4): 1.50≧BD / RD≧1.05 <8> The peripheral speed of the cylindrical rotor is 9 m / s or more and 20 m / s or less. <7> A method for producing the pigment dispersion described above. <9> In the media disperser in the first and second steps, the screen-type media separation unit is provided inside the cylindrical rotor. <1> ~ <8> A method for producing a pigment dispersion according to any one of the items. <10> The media disperser in the first and second steps is a disperser that circulates and disperses the mixture. When the effective volume of the media disperser is V, the volume of the mixture to be dispersed by the media disperser is v, and the operating time is t, the residence time RT (=V / v×t) of the mixture in the media disperser is 0.5 minutes or more and 3 minutes or less. <1> ~ <9> A method for producing a pigment dispersion according to any one of the items. <11> resin particles and <1> ~ <10> A step of agglomerating at least the resin particles and the organic pigment in a dispersion containing an organic pigment obtained by a method for producing a pigment dispersion according to any one of the items described in the item, to form aggregated particles, The process involves heating the dispersion of aggregated particles to fuse and combine the aggregated particles to form toner particles, A method for manufacturing toner for electrostatic image developing having the following characteristics. [Effects of the Invention]

[0008] <1> According to the invention, a method for producing a pigment dispersion is provided, comprising: a first step of wet-dispersing a mixture A containing an organic pigment, a flame retardant, a dispersant, and an aqueous medium using a media disperser to obtain a mixture B; and a second step of wet-dispersing the mixture B using a media disperser to obtain a mixture C, wherein the media disperser in the first and second steps is an annular media disperser having a cylindrical vessel, a cylindrical rotor provided inside the cylindrical vessel that rotates to disperse the mixture, and a screen-type media separation unit that separates media particles from the mixture, wherein the method for producing a pigment dispersion has higher pigment dispersibility and suppresses clogging of the screen-type media separation unit of the media disperser by the flame retardant compared to the case where the number average particle size MA of the media particles in the media disperser in the first step and the number average particle size MB of the media particles in the media disperser in the second step do not satisfy the above formulas (1) and (2).

[0009] <2> According to the invention, a method for producing a pigment dispersion is provided that offers higher pigment dispersibility and suppresses clogging of the screen-type media separation section of the media disperser by a flame retardant, compared to the case where the number-average particle size MA of the media particles of the media disperser in the first step and the number-average particle size MB of the media particles of the media disperser in the second step satisfy formulas (11) and (21).

[0010] <3> According to the invention, a method for producing a pigment dispersion is provided that provides higher pigment dispersibility and suppresses clogging of the screen-type media separation section of the media disperser by a flame retardant, compared to the case where the number-average particle size MA of the media particles of the media disperser in the first step and the number-average particle size MB of the media particles of the media disperser in the second step do not satisfy formula (3).

[0011] According to the invention according to <4>, compared with the case where the number average particle diameter MA of the media particles of the media disperser in the first step and the number average particle diameter MB of the media particles of the media disperser in the second step do not satisfy the above formula (31), a method for producing a pigment dispersion liquid is provided, in which the dispersibility of the pigment is high and clogging of the screen-type media separation part of the media disperser by the flame retardant is suppressed.

[0012] According to the invention according to <5>, in a method for producing a pigment dispersion liquid having a first step of wet-dispersing a mixture A containing an organic pigment, a flame retardant, a dispersant, and an aqueous medium using a media disperser to obtain a mixture B, and a second step of wet-dispersing the mixture B using a media disperser to obtain a mixture C, the media disperser in the first step and the second step is an annular-type media disperser having a cylindrical vessel, a cylindrical rotor provided inside the cylindrical vessel and rotating to disperse the mixture, and a screen-type media separation part for separating media particles and the mixture. Compared with the case where the number average particle diameter MA of the media particles of the media disperser in the first step and the number average particle diameter MB of the media particles of the media disperser in the second step do not satisfy the above formula (1) and the above formula (2), even if the flame retardant is a metal hydroxide, a method for producing a pigment dispersion liquid is provided, in which the dispersibility of the pigment is high and clogging of the screen-type media separation part of the media disperser by the flame retardant is suppressed.

[0013] According to the invention according to <6>, compared with the case where the aperture of the screen-type media separation part of the media disperser in the first step and the second step is less than 1 / 3 or more than 1 / 2 in terms of the ratio to the number average particle diameter of the media particles of the media disperser, a method for producing a pigment dispersion liquid is provided, in which the dispersibility of the pigment is high and clogging of the screen-type media separation part of the media disperser by the flame retardant is suppressed.

[0014] <7> According to the invention, a method for producing a pigment dispersion is provided in which the pigment dispersibility is higher and clogging of the screen-type media separation section of the media dispersion is suppressed by the flame retardant, compared to the case in which the inner diameter BD of the cylindrical vessel and the outer diameter RD of the cylindrical rotor of the media dispersion in the first and second steps do not satisfy formula (4).

[0015] <8> According to the invention, a method for producing a pigment dispersion is provided that offers higher pigment dispersibility and suppresses clogging of the screen-type media separation section of a media disperser by a flame retardant, compared to cases where the peripheral speed of the cylindrical rotor is less than 9 m / s or more than 20 m / s.

[0016] <9> According to the invention, in the media disperser in the first and second steps, the screen-type media separation unit is provided to have higher pigment dispersibility and to suppress clogging of the screen-type media separation unit of the media disperser by flame retardants, compared to the case where the screen-type media separation unit is provided on the outside of the cylindrical rotor.

[0017] <10> According to the invention, the media disperser in the first and second steps is a disperser that circulates and disperses a mixture, and when the effective volume of the media disperser is V, the volume of the mixture to be dispersed by the media disperser is v, and the operating time is t, the residence time RT (=V / v×t) during which the mixture remains in the media disperser is less than 0.5 minutes or more than 3 minutes, compared to the case where the peripheral speed of the cylindrical rotor is 9 m / s or more and 20 m / s or less. A method for producing a pigment dispersion liquid that suppresses clogging of the screen-type media separation section of the media disperser with a flame retardant is provided.

[0018] <11> According to the present invention, a method for manufacturing a pigment dispersion is provided, comprising a first step of wet-dispersing a mixture A containing an organic pigment, a flame retardant, a dispersant, and an aqueous medium using a media disperser to obtain a mixture B, and a second step of wet-dispersing the mixture B using a media disperser to obtain a mixture C, wherein the media disperser in the first and second steps is an annular media disperser having a cylindrical vessel, a cylindrical rotor provided inside the cylindrical vessel that rotates to disperse the mixture, and a screen-type media separation unit that separates media particles from the mixture, and compared to a method for manufacturing a pigment dispersion in which the number average particle size MA of the media particles of the media disperser in the first step and the number average particle size MB of the media particles of the media disperser in the second step do not satisfy the above formulas (1) and (2), a method for manufacturing a toner for electrostatic image developing is provided, which has high pigment dispersibility and suppresses clogging of the screen-type media separation unit of the media disperser by the flame retardant. [Brief explanation of the drawing]

[0019] [Figure 1] This is a schematic diagram showing an example of a manufacturing apparatus used in the method for producing a pigment dispersion according to this embodiment. [Figure 2] This is a schematic diagram showing an example of an annular media disperser used in the first and second steps of the method for producing a pigment dispersion according to this embodiment. [Modes for carrying out the invention]

[0020] The following describes an example embodiment of the present invention. These descriptions and examples are illustrative of the present invention and do not limit it.

[0021] In this specification, numerical ranges indicated using "~" represent a range that includes the numbers before and after "~" as the minimum and maximum values, respectively. In numerical ranges described stepwise within this specification, the upper or lower limit of one numerical range may be replaced by the upper or lower limit of another numerical range described stepwise. Furthermore, in numerical ranges described in this disclosure, the upper or lower limit of that range may be replaced by the values ​​shown in the examples.

[0022] In this specification, the term "process" includes not only independent processes but also processes that cannot be clearly distinguished from other processes, provided that their intended purpose is achieved.

[0023] When embodiments are described herein with reference to the drawings, the configuration of such embodiments is not limited to that shown in the drawings. Furthermore, the sizes of the components in each figure are conceptual, and the relative relationships between the components are not limited thereto.

[0024] In this specification, each component may contain multiple types of the corresponding substance. When referring to the amount of each component in a composition in this disclosure, if there are multiple types of the substance corresponding to each component in the composition, unless otherwise specified, it means the total amount of those multiple types of substances present in the composition.

[0025] In this specification, "electrostatic image developing toner" is also simply referred to as "toner."

[0026] <Method for producing a pigment dispersion> The method for producing a pigment dispersion according to this embodiment comprises a first step (hereinafter also referred to as the "first dispersion step") in which a mixture A containing an organic pigment, a flame retardant, a dispersant, and an aqueous medium is wet dispersed using a media disperser to obtain a mixture B, and a second step (hereinafter also referred to as the "second dispersion step") in which the mixture B is wet dispersed using a media disperser to obtain a mixture C. The media disperser in the first and second dispersion steps is an annular media disperser having a cylindrical vessel, a cylindrical rotor provided inside the cylindrical vessel and rotating to disperse the mixture, and a screen-type media separation unit for separating media particles from the mixture. Furthermore, the number-average particle size MA of the media particles in the media disperser in the first dispersion step and the number-average particle size MB of the media particles in the media disperser in the second dispersion step satisfy the following equations (1) and (2). Formula (1): 0.5mm≧MA>MB≧0.05mm Formula (2): 0.3mm≧MB≧0.05mm

[0027] The method for producing the pigment dispersion according to this embodiment provides high pigment dispersibility and suppresses clogging of the screen-type media separation section of the media disperser by the flame retardant. The reason for this is presumed to be as follows.

[0028] In toner manufacturing, to improve the color development of the pigment, it is necessary to reduce the particle size of the pigment to 0.5 μm or less and to improve the dispersion of the pigment. Conventionally, a method for producing a pigment dispersion that micronizes pigments is known, which involves stirring and mixing using a media disperser to break down and pulverize the pigment using shear force, frictional force, impact force from collisions between media particles, etc. It is known that smaller diameter media particles allow for finer pigment dispersion in a media disperser, enabling the dispersion of pigments down to a particle size of 0.5 μm or less. Furthermore, to efficiently achieve pigment fineness, a method of sequentially reducing the media diameter using a multi-stage media disperser is also known (for example, Patent Document 1).

[0029] As a media disperser for micronizing pigments, an annular media disperser is known, which has a cylindrical vessel and a cylindrical rotor provided inside the cylindrical vessel and rotating to disperse the mixture (for example, Patent Document 2). In an annular media disperser, media particles are placed between the cylindrical vessel and the cylindrical rotor, and the cylindrical rotor is rotated to apply a strong shearing force to the media particles, thereby efficiently crushing and pulverizing the pigment.

[0030] In annular media dispersers, centrifugal separation is used as a separation mechanism to efficiently separate media particles from pigment dispersions. However, organic pigments often have flame retardants added to them to meet flame retardancy requirements. In particular, metal oxides among the flame retardants are not separated by the media separation mechanism and become mixed into the pigment dispersion, causing deterioration of toner image quality and electrostatic properties.

[0031] On the other hand, a method for producing pigment dispersions using a screen-type media separation mechanism has also been proposed (for example, Patent Document 3). On the other hand, the pigments used as raw materials (especially organic pigments) contain flame retardants to prevent combustion. Therefore, the mixture A used as the raw material for the pigment dispersion contains a flame retardant. However, flame retardants can cause screen clogging, reducing the continuous processing capacity of the disperser.

[0032] In contrast, the method for producing a pigment dispersion involves a multi-stage process consisting of a first dispersion step and a second dispersion step, in which a mixture containing an organic pigment, a flame retardant, a dispersant, and an aqueous medium is wet-dispersed using an annular media disperser equipped with a screen-type media separation unit. Furthermore, the number-average particle size MA of the media particles in the media disperser in the first dispersion process and the number-average particle size MB of the media particles in the media disperser in the second dispersion process are made to satisfy equation (1) above and equation (2) below. In other words, the diameter of the media particles in the media disperser is reduced in both the first and second dispersion processes, and the diameter of the media particles in the media disperser in the first dispersion process is made larger than that in the second dispersion process. By reducing the diameter of the media particles in the media disperser in both the first and second dispersion processes, a stronger shearing action can be applied to the media particles in the media disperser in both processes compared to conventional methods, thereby efficiently crushing and pulverizing the pigment. In addition, by making the media particles of the media disperser larger in the first dispersion process than in the second dispersion process, the flame retardant can be collected in stages according to particle size in the first and second dispersion processes, thereby suppressing clogging.

[0033] From the above, it is presumed that the method for producing the pigment dispersion according to this embodiment has high pigment dispersibility and suppresses clogging of the screen-type media separation section of the media disperser by the flame retardant. Furthermore, in the method for producing the pigment dispersion according to this embodiment, clogging of the screen-type media separation section of the media disperser by the flame retardant is suppressed, and high continuous processing performance of the annular-type media disperser is also achieved.

[0034] In the method for producing a pigment dispersion according to this embodiment, the flame retardant can be removed by using a screen-type media separation unit.

[0035] The following describes in detail the method for producing the pigment dispersion according to this embodiment.

[0036] First, we will describe the manufacturing apparatus used in the method for producing the pigment dispersion according to this embodiment (hereinafter also referred to as the "pigment dispersion manufacturing apparatus").

[0037] The pigment dispersion manufacturing apparatus 100 shown in Figure 1 includes, for example, a first storage tank 10A, a first media disperser 12A, a second storage tank 10B, and a second media disperser 12B.

[0038] A supply pipe 14A is connected to the first storage tank 10A to supply a mixture A containing an organic pigment, a flame retardant, a dispersant, and an aqueous medium to the first storage tank 10A. The first storage tank 10A and the first media disperser 12A are connected by a first supply pipe 16A that supplies mixture A from the first storage tank 10A to the first media disperser 12A, and a first discharge pipe 18A that discharges the mixture A dispersed by the first media disperser 12A back to the first storage tank 10A.

[0039] A supply pipe 14B is connected to the second storage tank 10B from the path of the first discharge pipe 18A, supplying mixture B, which is obtained by circulating and dispersing mixture A in the first media disperser 12A, to the second storage tank 10B. The second storage tank 10B and the second media disperser 12B are connected by a second supply pipe 16B that supplies the mixture B from the second storage tank 10B to the second media disperser 12B, and a second discharge pipe 18B that discharges the mixture B dispersed in the second media disperser 12B back to the second storage tank 10B.

[0040] Next, the first media distributor 12A and the second media distributor 12B will be described. Note that since the configurations of the first media distributor 12A and the second media distributor 12B are the same, they may be described together as the first and second media distributors 12A and 12B. Furthermore, the component codes will be standardized. The first and second media dispersers 12A and 12B shown in Figure 2 are annular media dispersers, for example, having a cylindrical vessel 20, a cylindrical rotor 22 provided inside the cylindrical vessel 20 that rotates to disperse the mixture, and a screen-type media separation unit 24 that separates media particles from the mixture.

[0041] In Figure 2, 16A and 16B represent the first and second supply pipes 16A and 16B that supply mixtures A and B from the first and second storage tanks 10A and 10B to the first and second media dispersers 12A and 12B, respectively, while 18A and 18B represent the first and second discharge pipes 18A and 18B that discharge the mixtures A and B dispersed in the first and second media dispersers 12B back to the first and second storage tanks 10A and 10B.

[0042] Next, an example of each step in the method for producing the pigment dispersion according to this embodiment will be described. The method for producing a pigment dispersion according to this embodiment comprises a first dispersion step and a second dispersion step. The first dispersion step involves wet-dispersing mixture A, which contains an organic pigment, a flame retardant, a dispersant, and an aqueous medium, using a first media disperser 12A to obtain mixture B. The second dispersion step involves wet-dispersing mixture B using the second media disperser 12B to obtain mixture C.

[0043] Specifically, for example, in the first and second dispersion steps, the mixture is dispersed as follows:

[0044] In the pigment dispersion manufacturing apparatus 100 shown in Figure 1, a mixture A containing an organic pigment, a flame retardant, a dispersant, and an aqueous medium is supplied to the first storage tank 10A through a supply pipe 14A. Mixture A is supplied from the first containment tank 10A through the first supply pipe 16A and dispersed in the first media disperser 12A. Mixture A dispersed in the first media disperser 12A is returned to the first containment tank 10A through the first discharge pipe 18A and is circulated and dispersed again in the first media disperser 12A through the first supply pipe 16A.

[0045] In the pigment dispersion manufacturing apparatus 100, mixture B is supplied to the second storage tank 10B through the supply pipe 14B. Mixture B is supplied from the second containment tank 10B through the second supply pipe 16B and dispersed in the second media disperser 12B. Mixture A, dispersed in the second media disperser 12B, is returned to the second containment tank 10B through the second discharge pipe 18B and is circulated and dispersed again in the second media disperser 12B through the second supply pipe 16B. Mixture B is circulated and dispersed in the first media disperser 12A to obtain mixture C.

[0046] Furthermore, in the first and second media dispersers 12A and 12B shown in Figure 2, the mixture is supplied with media particles (not shown) placed between the cylindrical vessel 20 and the cylindrical rotor 22. The rotation of the cylindrical rotor 22 applies a strong shearing force to the media particles, causing the pigment to be crushed and pulverized, resulting in finer particles and dispersion. The media particles and the mixture are then separated in the screen-type media separation unit 24.

[0047] Furthermore, in the method for producing a pigment dispersion according to this embodiment, even with a mixture A containing, for example, an organic pigment composed of aggregates of primary particles with a volume-average particle size of 50 nm to 200 nm, and a flame retardant with a volume-average particle size of 50 μm to 1000 μm, the above dispersion treatment suppresses clogging of the screen-type media separation section of the media disperser by the flame retardant, while obtaining a pigment dispersion with high dispersibility, where the volume-average particle size (i.e., dispersion diameter) of the organic pigment is 50 nm to 300 nm. In addition, the flame retardant removal capability is also improved.

[0048] Here, the volume-average particle size of the organic pigment and flame retardant is measured as follows. The particle size is measured using a laser diffraction scattering particle size distribution analyzer (e.g., Microtrac MT3000II, manufactured by Microtrac-Bell), and the particle size representing the cumulative 50% of the volume-based particle size distribution is measured five times. Of the cumulative 50% of particle sizes obtained, the average of the three particle sizes excluding the maximum and minimum values ​​is defined as the volume-average particle size D50v.

[0049] Next, we will describe the details of the first and second media dispersers 12A and 12B in the method for producing the pigment dispersion according to this embodiment.

[0050] The number-average particle size MA of the media particles in the first media disperser 12A and the number-average particle size MB of the media particles in the second media disperser 12B satisfy the following equations (1) and (2). As a result, the pigment is made finer and its dispersibility is improved. In addition, clogging of the screen-type media separation section of the media disperser by flame retardants is suppressed. Furthermore, high continuous processing performance of the annular-type media disperser is achieved. Flame retardant removal performance is also improved. From these perspectives, it is preferable that the number-average particle size MA and the number-average particle size MB of the media particles satisfy the following equations (11) and (21).

[0051] Formula (1): 0.5mm≧MA>MB≧0.05mm Formula (2): 0.3mm≧MB≧0.05mm

[0052] Formula (11): 0.4mm≧MA>MB≧0.1mm Formula (21): 0.2mm≧MB≧0.1mm

[0053] The number-average particle size MA of the media particles in the first media disperser 12A and the number-average particle size MB of the media particles in the second media disperser 12B preferably satisfy the following equation (3), and more preferably satisfy the following equation (31). When the number-average particle size MA and the number-average particle size MB of the media particles satisfy the following equation (3) or equation (31), and when a sufficient particle size difference is ensured between each media particle in the first and second media dispersers 12A and 12B, the flame retardant can be collected in stages according to particle size in the first and second dispersion processes, thereby suppressing clogging. As a result, the dispersibility of the pigment is improved, and the effect of suppressing clogging of the screen-type media separation section 24 by the flame retardant is also enhanced. Furthermore, the high continuous processing performance of the annular-type media disperser is also improved. In addition, the flame retardant removal performance is also improved.

[0054] Formula (3): 0.45mm≧MA-MB≧0.05mm Formula (31): 0.3mm≧MA-MB>≧0.1mm

[0055] Here, the number-average particle size of the media particles is measured as follows: 100 media particles are observed using a Scanning Electron Microscope (SEM), and the equivalent circle diameter of each particle is determined by image analysis of the media particles. The 50th percentile diameter (D50p) at the cumulative frequency of the obtained equivalent circle diameters is defined as the number-average particle size of the media particles.

[0056] The inner diameter BD of the cylindrical vessel 20 and the outer diameter RD of the cylindrical rotor 22 preferably satisfy the following equation (4), and more preferably satisfy equation (41). When the inner diameter BD of the cylindrical vessel 20 and the outer diameter RD of the cylindrical rotor 22 satisfy the following equation (4) or equation (41), the distance between the cylindrical vessel 20 and the cylindrical rotor 22 becomes appropriate, suppressing a reduction in the flow rate of the mixture, while increasing the shearing effect of the media particles and improving the dispersibility of the pigment. Equation (4): 1.50≧BD / RD≧1.05 Formula (41): 1.30≧BD / RD≧1.07

[0057] The cylindrical rotor 22 is provided with slits 22A for media particles to move between the inner and outer parts of the cylindrical rotor 22. Preferably, multiple slits are provided, arranged circumferentially along the axial direction of the cylindrical rotor 22. The rotation of the cylindrical rotor 22 causes the media particles to circulate between the inner and outer parts of the cylindrical rotor 22, improving the dispersibility of the pigment. The cylindrical rotor 22 may have protrusions on its walls. When the cylindrical rotor 22 rotates, the protrusions increase the shearing action of the media particles, thereby improving the dispersibility of the pigment.

[0058] The peripheral speed of the cylindrical rotor 22 is preferably 9 m / s or more and 20 m / s or less, and more preferably 11 m / s or more and 17 m / s or less. Setting the peripheral speed of the cylindrical rotor within the above range increases the shearing action of the media particles, thereby improving the dispersibility of the pigment.

[0059] The screen-type media separation unit 24 may be, for example, a cylindrical metal mesh filter. The screen-type media separation unit 24 is not limited to the above filter, but from the viewpoint of strength and durability, a mesh filter made of wedge wire or notch wire is preferred.

[0060] The mesh opening of the screen-type media separation unit 24 is preferably 1 / 3 or more and 1 / 2 or less in ratio to the number-average particle size of the media particles of the first and second media dispersers 12A and 12B, and more preferably 1 / 2.5 or more and 1 / 2 or less. By setting the mesh opening of the screen-type media separation unit 24 within the above range, the opening area of ​​the screen can be widened while separating the mixture and media particles, thereby increasing the effectiveness of suppressing clogging of the screen-type media separation unit 24 by flame retardants. This also improves the high continuous processing performance of the media disperser. Furthermore, the flame retardant removal performance is also improved.

[0061] The mesh opening of the screen-type media separation section 24 is preferably 20 μm or more and 250 μm or less, and more preferably 30 μm or more and 200 μm or less.

[0062] The screen-type media separation unit 24 is, for example, located inside the cylindrical rotor 22. This suppresses the pressing of media against the screen by centrifugal force, compared to when the screen-type media separation unit 24 is located outside the cylindrical rotor 22, thereby suppressing clogging of the screen-type media separation unit 24. Furthermore, high continuous processing performance of the media disperser is achieved.

[0063] The first and second media dispersers 12A and 12B are, for example, dispersers that circulate and disperse a mixture. Furthermore, when the effective volume V of the first and second media dispersers 12A and 12B is denoted by the volume v of the mixture dispersed by the first and second media dispersers 12A and 12B and the operating time is denoted by the operating time t, it is preferable that the residence time RT (=V / v×t) of the mixture in the first and second media dispersers 12A and 12B is 0.5 minutes or more and 3 minutes or less, and more preferably 0.7 minutes or more and 2.5 minutes or less. By setting the residence time TR within the above range, the shearing action of the media particles is sufficiently applied to the pigment, improving the dispersibility of the pigment. In addition, the increased residence time suppresses the pressing of the flame retardant onto the screen, thereby preventing clogging of the screen-type media separation unit 24 by the flame retardant. Furthermore, high continuous processing performance of the media disperser is achieved.

[0064] Here, the effective volume V (unit = L) represents the volume of the area in the media disperser where the packed media contributes to the dispersion of the mixture, and the catalog value of the media disperser is adopted. The effective volume V is, for example, between 0.5 and 10. The volume v of the mixture (unit = L) represents the total volume of the mixture circulated and dispersed in the media disperser. The volume v of the mixture is, for example, between 10 L and 1500 L. Operating time t refers to the time from the start of circulating dispersion of the mixture in the media disperser to the end of circulating dispersion. The unit is time (minutes). The operating time t is, for example, between 10 minutes and 1500 minutes.

[0065] Next, we will describe mixture A, which is used as a raw material in the method for producing the pigment dispersion according to this embodiment. Mixture A comprises an organic pigment, a flame retardant, a dispersant, and an aqueous medium. Mixture A may also contain other additives. In addition, in the pigment dispersion manufacturing apparatus 100, the first storage tank 10A may be supplied with a pre-mixed mixture A, or each component of mixture A may be supplied individually.

[0066] -Organic Pigments- Examples of well-known organic pigments include Chrome Yellow, Hansa Yellow, Benzidine Yellow, Sluen Yellow, Quinoline Yellow, Pigment Yellow, Permanent Orange GTR, Pyrazolone Orange, Vulcan Orange, Watch Young Red, Permanent Red, Brilliant Carmine 3B, Brilliant Carmine 6B, DuPont Oil Red, Pyrazolone Red, Risol Red, Rhodamine B Lake, Lake Red C, Pigment Red, Rose Bengal, Aniline Blue, Ultramarine Blue, Chalcioil Blue, Methylene Blue Chloride, Phthalocyanine Blue, Pigment Blue, Phthalocyanine Green, and Malachite Green Oxalate.

[0067] -Flame retardant- Flame retardants are components that are pre-mixed with organic pigments to prevent them from burning. Examples of flame retardants include metal hydroxides, phosphorus compounds such as red phosphorus, antimony compounds, and bromine compounds. Among these, metal hydroxides are preferred as flame retardants. Although metal oxides are hard and difficult to crush and pulverize, even when used as flame retardants, they offer high pigment dispersibility and high flame retardant removal while suppressing clogging of the screen-type media separation section of the media disperser. Furthermore, with soft flame retardants such as red phosphorus, which are easily crushed and broken, excessive crushing and breaking can make it difficult to remove the flame retardant after the pigment dispersion is manufactured, due to knots and other factors.

[0068] -Dispersant- Examples of dispersants include anionic surfactants. Examples of anionic surfactants include alkylbenzene sulfonates, alkylphenyl sulfonates, alkylnaphthalene sulfonates, higher fatty acid salts, sulfate salts of higher fatty acid esters, sulfonates of higher fatty acid esters, sulfate salts and sulfonates of higher alcohol ethers, higher alkyl sulfosuccinates, polyoxyethylene alkyl ether carboxylates, polyoxyethylene alkyl ether sulfates, alkyl phosphates, and polyoxyethylene alkyl ether phosphates. Other dispersants include rosin, rosin derivatives, and coupling agents.

[0069] -Aqueous medium- Examples of aqueous media include water (distilled water, deionized water, etc.) and alcohols. However, the proportion of water in the aqueous medium should be 80% by mass (preferably 90% by mass or more, more preferably 100% by mass).

[0070] -Amount of each component in mixture A- The proportions of each component in mixture A are as follows: The amount of organic pigment blended is preferably 10% by mass or more and 40% by mass or less relative to the aqueous medium, and more preferably 15% by mass or more and 35% by mass or less. The amount of flame retardant added is, for example, 0.005% by mass or more and 1% by mass or less relative to the organic pigment. The amount of dispersant added is, for example, 5% by mass to 15% by mass relative to the organic pigment.

[0071] Furthermore, since the flame retardant is a component that is pre-mixed with organic pigments, it will be measured as follows. First, the type of flame retardant contained in the object being measured is identified through various analyses. Separately, a substance containing the flame retardant identified through analysis, with a known formulation, is subjected to fluorescent X-ray analysis to measure the elemental amounts contained in the identified flame retardant, and a calibration curve is created. Then, the sample to be measured is subjected to fluorescent X-ray analysis to determine the amount of elements contained in the identified flame retardant, and the amount of the target component is determined from the obtained elemental amounts and calibration curve.

[0072] The method for producing the pigment dispersion according to this embodiment, as described above, is typically applied to the production of resin particle dispersions for toner. Other applications include inkjet inks, cosmetics, powder coatings, various coatings, and electronic paper inks.

[0073] <Toner manufacturing method> The toner manufacturing method according to this embodiment is: A step of forming aggregated particles by agglomerating at least the resin particles and organic pigment in a dispersion containing resin particles and organic pigment (hereinafter referred to as the aggregated particle formation step), The process involves heating a dispersion of aggregated particles to fuse and combine the aggregated particles to form toner particles (hereinafter referred to as the fusion and combination process), It has. Furthermore, the organic pigment obtained by the method for producing the pigment dispersion according to the above embodiment is used as the organic pigment.

[0074] The toner according to this embodiment is a toner having toner particles obtained by the toner manufacturing method according to this embodiment.

[0075] The details of each step are explained below. The following explanation describes a method for obtaining toner particles containing organic pigments and a release agent, but the release agent is used only as needed. Of course, other additives besides the release agent may also be used.

[0076] -Particle dispersion preparation process- In the particle dispersion preparation process, resin particle dispersion, pigment dispersion, and mold release agent dispersion are prepared. The pigment dispersion is manufactured according to the method for manufacturing the pigment dispersion according to the embodiment described above. However, a pigment dispersion other than the one obtained by the method for manufacturing the pigment dispersion according to the embodiment described above may be used in combination.

[0077] ·Resin particle dispersion A resin particle dispersion is a dispersion in which resin particles, which serve as the binder resin for toner, are dispersed. A resin particle dispersion can be prepared, for example, by dispersing resin particles in an aqueous medium using a surfactant.

[0078] Examples of resins used for resin particles include vinyl resins consisting of monomer homopolymers of styrenes (e.g., styrene, parachlorostyrene, α-methylstyrene, etc.), (meth)acrylic acid esters (e.g., methyl acrylate, ethyl acrylate, n-propyl acrylate, n-butyl acrylate, lauryl acrylate, 2-ethylhexyl acrylate, methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, lauryl methacrylate, 2-ethylhexyl methacrylate, etc.), ethylenically unsaturated nitriles (e.g., acrylonitrile, methacrylonitrile, etc.), vinyl ethers (e.g., vinyl methyl ether, vinyl isobutyl ether, etc.), vinyl ketones (vinyl methyl ketone, vinyl ethyl ketone, vinyl isopropenyl ketone, etc.), olefins (e.g., ethylene, propylene, butadiene, etc.), etc., or copolymers of two or more of these monomers. Examples of resins include non-vinyl resins such as epoxy resins, polyester resins, polyurethane resins, polyamide resins, cellulose resins, polyether resins, and modified rosin; mixtures of these with the aforementioned vinyl resins; and graft polymers obtained by polymerizing vinyl monomers in the presence of these. These resins may be used individually or in combination of two or more types.

[0079] The resin is preferably a resin having polar groups such as carboxyl groups, sulfonic acid groups, and hydroxyl groups, and in particular, it is preferably a resin having an acid value.

[0080] It is preferable to use an amorphous resin. However, a crystalline resin (for example, a crystalline polyester resin) may also be used. Here, amorphous resins refer to materials that, in thermal analysis measurements using differential scanning calorimetry (DSC), exhibit only a stepwise endothermic change rather than a clear endothermic peak, are solid at room temperature, and undergo thermoplasticization at temperatures above their glass transition temperature. On the other hand, crystalline resins are those that exhibit a clear endothermic peak in differential scanning calorimetry (DSC), rather than a stepwise change in endothermic heat. Specifically, for example, a crystalline resin means that the full width at half maximum (FWHM) of the endothermic peak measured at a heating rate of 10°C / min is within 10°C, while an amorphous resin means a resin whose FWHM exceeds 10°C, or a resin in which no clear endothermic peak is observed.

[0081] This section will explain amorphous resins. Examples of amorphous resins include known amorphous resins such as amorphous polyester resin, amorphous vinyl resin (e.g., styrene-acrylic resin), epoxy resin, polycarbonate resin, and polyurethane resin. Among these, amorphous polyester resin and amorphous vinyl resin (particularly styrene-acrylic resin) are preferred, and amorphous polyester resin is more preferred. Furthermore, it is also preferable to use amorphous polyester resin and styrene-acrylic resin in combination as the amorphous resin. In addition, it is also preferable to use an amorphous resin having amorphous polyester resin segments and styrene-acrylic resin segments as the amorphous resin.

[0082] Examples of aqueous media include water (distilled water, deionized water, etc.) and alcohols.

[0083] Examples of surfactants include anionic surfactants such as sulfate esters, sulfonates, phosphates, and soaps; cationic surfactants such as amine salts and quaternary ammonium salts; and nonionic surfactants such as polyethylene glycol, alkylphenol ethylene oxide adducts, and polyhydric alcohols. Among these, anionic surfactants and cationic surfactants are particularly noteworthy. Nonionic surfactants may be used in combination with anionic or cationic surfactants. Surfactants may be used individually or in combination of two or more types.

[0084] In resin particle dispersions, common dispersion methods for dispersing resin particles in a dispersion medium include, for example, rotary shear homogenizers, ball mills with media, sand mills, and dyno mills. Depending on the type of resin particles, the resin particles may also be dispersed in the resin particle dispersion using, for example, a phase inversion emulsification method. Phase inversion emulsification is a method in which the resin to be dispersed is dissolved in a hydrophobic organic solvent in which the resin is soluble, a base is added to the organic continuous phase (O phase) to neutralize it, and then an aqueous medium (W phase) is added. This causes a conversion of the resin from W / O to O / W (so-called phase inversion), resulting in a discontinuous phase, and the resin is dispersed in the aqueous medium in particulate form.

[0085] The volume-average particle size of the resin particles dispersed in the resin particle dispersion is preferably 0.01 μm or more and 1 μm or less, more preferably 0.08 μm or more and 0.8 μm or less, and even more preferably 0.1 μm or more and 0.6 μm or less. The volume-average particle size of the resin particles is measured using a laser diffraction particle size distribution analyzer (e.g., LA-700, manufactured by Horiba, Ltd.). The particle size distribution is obtained by subtracting the cumulative distribution from the smallest particle size side for each divided particle size range (channel), and the particle size that accounts for 50% of the total particle size is measured as the volume-average particle size D50v. The volume-average particle size of particles in other dispersions is measured in the same manner.

[0086] The resin particle content in the resin particle dispersion is preferably, for example, 5% by mass or more and 50% by mass or less, and more preferably 10% by mass or more and 40% by mass or less.

[0087] • Release agent particle dispersion A release agent particle dispersion is a dispersion in which a release agent is dispersed in an aqueous medium. Examples of release agents include hydrocarbon waxes; natural waxes such as carnauba wax, rice wax, and candelilla wax; synthetic or mineral / petroleum-based waxes such as montan wax; and ester waxes such as fatty acid esters and montanic acid esters. However, the release agents are not limited to these. The melting temperature of the release agent is preferably 50°C to 110°C, and more preferably 60°C to 100°C. The melting temperature is determined from the DSC curve obtained by differential scanning calorimetry (DSC) using the "melting peak temperature" described in JIS K 7121-1987 "Method for determining the transition temperature of plastics".

[0088] The release agent is dispersed in an aqueous medium by known methods, but media-type dispersers such as rotary shear homogenizers, ball mills, sand mills, and attritors, and high-pressure opposing impact dispersers are preferably used. Alternatively, a polar ionic surfactant may be used as the release agent, and it may be dispersed in an aqueous solvent using a homogenizer to prepare a release agent particle dispersion. The volume-average particle size of the release agent particles is preferably 1 μm or less, and more preferably 0.01 μm or more and 1 μm or more.

[0089] -Agglomerated particle formation process- Next, the resin particle dispersion is mixed with the pigment dispersion and the mold release agent particle dispersion. Then, in the mixed dispersion, the resin particles, organic pigment, and release agent particles are heteroaggregated to form aggregated particles containing the resin particles, organic pigment, and release agent particles, which have a diameter close to that of the target toner particles.

[0090] Specifically, for example, a coagulant is added to a mixed dispersion, the pH of the mixed dispersion is adjusted to be acidic (for example, pH 2 to 5), a dispersion stabilizer is added as needed, and then the mixture is heated to a temperature of the glass transition temperature of the resin particles (specifically, for example, above the glass transition temperature of the resin particles -30°C or below the glass transition temperature of -10°C) to agglomerate the particles dispersed in the mixed dispersion and form agglomerated particles. In the agglomerated particle formation step, for example, the mixed dispersion may be stirred in a rotary shear homogenizer, the above-mentioned flocculant may be added at room temperature (e.g., 25°C), the pH of the mixed dispersion may be adjusted to acidic (e.g., pH 2 to 5), a dispersion stabilizer may be added as needed, and then the above-mentioned heating may be performed.

[0091] Examples of flocculants include surfactants with opposite polarity to the surfactant used as a dispersant added to a mixed dispersion, inorganic metal salts, and metal complexes with a valency of 2 or higher. In particular, when a metal complex is used as a flocculant, the amount of surfactant used is reduced and the electrostatic properties are improved. Additives that form complexes or similar bonds with the metal ions of the flocculant may be used as needed. Chelating agents are preferably used as such additives.

[0092] 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. As a chelating agent, a water-soluble chelating agent may be used. Examples of chelating agents include oxycarboxylic acids such as tartaric acid, citric acid, and gluconic acid, as well as iminodiacetic acid (IDA), nitrilotriacetic acid (NTA), and ethylenediaminetetraacetic acid (EDTA). The amount of chelating agent to be added is preferably 0.01 parts by mass or more and 5.0 parts by mass or less per 100 parts by mass of resin particles, and more preferably 0.1 parts by mass or more and less than 3.0 parts by mass.

[0093] -Fusion / unification process- Next, the dispersion of aggregated particles is heated to a temperature above the glass transition temperature of the resin particles (for example, 10 to 30°C higher than the glass transition temperature of the resin particles) to fuse and combine the aggregated particles and form toner particles.

[0094] Toner particles are obtained through the above process. Furthermore, toner particles may be manufactured by further mixing a dispersion of aggregated particles containing dispersed aggregated particles with a dispersion of resin particles containing dispersed resin particles, thereby agglomerating the aggregated particles so that resin particles adhere to the surface of the aggregated particles to form second aggregated particles, and by heating the second dispersion of aggregated particles containing the second aggregated particles to fuse and combine the second aggregated particles to form toner particles with a core / shell structure.

[0095] After the fusion and combination process is complete, the toner particles formed in the solution are subjected to known washing, solid-liquid separation, and drying processes to obtain dried toner particles. The washing process should be thoroughly performed using ion-exchanged water for displacement washing, considering the electrostatic charge. The solid-liquid separation process is not particularly restricted, but suction filtration, pressure filtration, etc., are preferable for productivity. The drying process is also not particularly restricted, but freeze-drying, air-flow drying, fluidized bed drying, vibratory fluidized bed drying, etc., are preferable for productivity.

[0096] The toner and its manufacturing method according to this embodiment are produced, for example, by adding an external additive to the obtained dried toner particles and mixing them. Mixing can be performed using, for example, a V-blender, a Henschel mixer, a Redigge mixer, etc. Furthermore, if necessary, coarse particles of the toner may be removed using a vibrating screen separator, a wind screen separator, etc.

[0097] Examples of external additives include inorganic particles. Examples of such inorganic particles include SiO2, TiO2, Al2O3, CuO, ZnO, SnO2, CeO2, Fe2O3, MgO, BaO, CaO, K2O, Na2O, ZrO2, CaO·SiO2, K2O·(TiO2)n, Al2O3·2SiO2, CaCO3, MgCO3, BaSO4, MgSO4, and the like.

[0098] The surface of the inorganic particles used as an external additive should preferably be hydrophobic. Hydrophobic treatment is carried out, for example, by immersing the inorganic particles in a hydrophobic agent. The hydrophobic agent is not particularly limited, but examples include silane-based coupling agents, silicone oil, titanate-based coupling agents, and aluminum-based coupling agents. These may be used individually or in combination of two or more. The amount of hydrophobic treatment agent is typically, for example, 1 to 10 parts by mass per 100 parts by mass of inorganic particles.

[0099] Examples of external additives include resin particles (such as polystyrene, polymethyl methacrylate (PMMA), and melamine resin), and cleaning activators (for example, metal salts of higher fatty acids represented by zinc stearate, and fluorine-based high molecular weight particles).

[0100] The amount of external additive added is preferably 0.01% by mass or more and 5% by mass or less relative to the toner particles, and more preferably 0.01% by mass or more and 2.0% by mass or less. [Examples]

[0101] The following describes embodiments of the present invention, but the present invention is not limited to these embodiments. In the following description, unless otherwise specified, "parts" and "%" all refer to mass.

[0102] (Example 1) <Manufacturing of Pigment Dispersion> • Organic pigment: Manufactured by Dainichi Seika Co., Ltd., Y74, 98 parts by mass • Flame retardant: Aluminum hydroxide (number average particle size = 80 μm) 0.1 parts by mass (flame retardant contained in organic pigment) • Anionic surfactant (manufactured by Daiichi Kogyo Seiyaku Co., Ltd., Neogen®) 2 parts by mass • Ion-exchanged water 400 parts by mass Mixture A, which was a mixture of the above components, was circulated and dispersed as the first dispersion step under the conditions shown in Table 1 using the first media disperser shown in Figure 2 (a modified version of Inoue Seisakusho Co., Ltd.'s "Keymill KMC-0.5") to obtain mixture B. Next, as a second dispersion step, mixture B was circulated and dispersed under the conditions shown in Table 1 using the second media disperser shown in Figure 2 (a modified version of Inoue Seisakusho Co., Ltd.'s "Keymill KMC-0.5") to obtain mixture C. Through the above steps, a pigment dispersion consisting of mixture C was obtained.

[0103] (Examples 2-15, Comparative Examples 1-5) A pigment dispersion was obtained in the same manner as in Example 1, except that the conditions shown in Table 1 were changed. However, in Example 7, instead of aluminum hydroxide as a flame retardant, the organic pigment contained 0.1 parts by mass of red phosphorus (number-average particle size = 10 μm). Furthermore, Example 13 used first and second media dispersers that were modified to position the screen-type separation unit on the outside of the cylindrical rotor. Comparative Example 4 used first and second media dispersers that were modified to replace the screen-type separation unit with a centrifugal separation unit. In Comparative Example 5, instead of the first and second media dispersers, a stirred tank type disperser with a screen-type separation section (a modified version of the Willy e Bakkofen (WAB) "DynoMill ECM-AP05") was used.

[0104] (evaluation) <Evaluation of pigment dispersibility> The volume-average particle size D50v of the organic pigment in the pigment dispersion obtained in each example was measured using the method described above. The dispersion diameter of the organic pigment was then evaluated according to the following criteria. The practically acceptable range is B or higher. A: The dispersion diameter of the organic pigment is 200 nm or less. B: The dispersion diameter of the organic pigment is greater than 200 nm and less than or equal to 300 nm. C: The dispersion diameter of the organic pigment is greater than 300 nm and less than or equal to 700 mm. D: Dispersion diameter of organic pigment exceeds 700 nm

[0105] <Evaluation of flame retardant removal capability> The entire amount of pigment dispersion obtained in each example was sieved through a sieve with a mesh size of 0.05 μm, and the number of flame retardant particles remaining on the mesh was visually confirmed. The dispersion was then evaluated according to the following criteria. A practically acceptable range is defined as B or higher. A: The number of flame retardant particles remaining on the sieve screen is 20 or less. B: The number of flame retardant particles remaining on the sieve screen is between 20 and 40. C: The number of flame retardant particles remaining on the sieve screen is between 40 and 60. D: The number of flame retardant particles remaining on the sieve exceeded 60.

[0106] <Evaluation of the continuous processing capabilities of media distribution machines> The manufacturing process for each pigment dispersion was repeated, and the number of continuous processes required until the screen-type separation section of the media disperser became blocked was evaluated. Specifically, a pressure gauge was installed immediately before the mixed liquid supply inlet of the media disperser, and when the gauge pressure rose to 0.5 MPa, it was determined that clogging by the flame retardant had occurred and the screen-type separation section had become blocked. The following criteria were used for evaluation. However, the evaluation was based on the number of processing cycles until the screen-type separation section of either the first media disperser in the first dispersion process or the second media disperser in the second dispersion process became blocked. The practically acceptable range is B○ or higher. A: Number of consecutive processing attempts: 20 or more B: Number of consecutive processing cycles is 10 or more but less than 20. C: Number of consecutive processing cycles is 5 or more but less than 10 D: Number of consecutive processing attempts is less than 5

[0107] The results are shown in Table 1. Further details regarding the abbreviations and other terms used in Table 1 are as follows: • First stage media diameter MA: Number-average particle size MA of media particles in the first media disperser in the first dispersion process. • Second stage media diameter MB: Number-average particle size MB of media particles in the second media disperser during the second dispersion process. • Screen-type separation section mesh opening (ratio to MA and MB): The mesh opening of the clean-type separation section, expressed as the ratio of the number-average particle size MA and MB of the media particles in the first and second media dispersers.

[0108] [Table 1-1]

[0109] [Table 1-2]

[0110] From the above results, it can be seen that the method for producing the pigment dispersion in this embodiment has higher pigment dispersibility compared to the method for producing the pigment dispersion in the comparative example, and that it suppresses clogging of the screen-type media separation section of the media disperser by the flame retardant. Furthermore, it can be seen that it has high flame retardant removal efficiency. [Explanation of Symbols]

[0111] 10A First Storage Tank 10B Second storage tank 12A First Media Distributor 12B Second Media Distributor 14A supply pipe 14B Supply pipe 16A First supply pipe 16B Second supply pipe 18A First discharge pipe 18B Second discharge pipe 20 Cylindrical Vessels 22 Cylindrical rotor 22A Slit 24-screen media separation unit

Claims

1. The first step involves wet-dispersing mixture A, which contains an organic pigment, a flame retardant, a dispersant, and an aqueous medium, using a media disperser to obtain mixture B. The second step involves wet-dispersing the aforementioned mixture B using a media disperser to obtain mixture C, It has, The media disperser in the first and second steps is an annular media disperser having a cylindrical vessel, a cylindrical rotor provided inside the cylindrical vessel and rotating to disperse the mixture, and a screen-type media separation unit for separating media particles from the mixture. The number-average particle size MA of the media particles in the media disperser in the first step and the number-average particle size MB of the media particles in the media disperser in the second step satisfy the following equations (1) and (2), In the first and second steps, the mesh opening of the screen-type media separation section of the media disperser is 1 / 3 or more and 1 / 2 or less in ratio to the number-average particle size of the media particles of the media disperser. A method for producing a pigment dispersion, wherein the flame retardant is at least one of a metal hydroxide, a phosphorus compound, an antimony compound, and a bromine compound. Formula (1): 0.5mm≧MA>MB≧0.05mm Formula (2): 0.3mm≧MB≧0.05mm

2. A method for producing a pigment dispersion according to claim 1, wherein the number-average particle size MA of the media particles of the media disperser in the first step and the number-average particle size MB of the media particles of the media disperser in the second step satisfy the following formulas (11) and (21). Formula (11): 0.4mm≧MA>MB≧0.1mm Formula (21): 0.2mm≧MB≧0.1mm

3. A method for producing a pigment dispersion according to claim 1 or claim 2, wherein the number-average particle size MA of the media particles of the media disperser in the first step and the number-average particle size MB of the media particles of the media disperser in the second step satisfy the following formula (3). Formula (3): 0.45mm≧MA-MB≧0.05mm

4. The method for producing a pigment dispersion according to claim 3, wherein the number-average particle size MA of the media particles of the media disperser in the first step and the number-average particle size MB of the media particles of the media disperser in the second step satisfy the following formula (31). Formula (31): 0.3mm≧MA-MB>≧0.1mm

5. A method for producing a pigment dispersion according to any one of claims 1 to 4, wherein the flame retardant is a metal hydroxide.

6. The method for producing a pigment dispersion according to any one of Claims 1 to 5, wherein the flame retardant is a component that has been mixed with an organic pigment in advance.

7. A method for producing a pigment dispersion according to any one of claims 1 to 6, wherein the inner diameter BD of the cylindrical vessel and the outer diameter RD of the cylindrical rotor of the media disperser in the first step and the second step satisfy the following formula (4). Formula (4): 1.50≧BD / RD≧1.05

8. The method for producing a pigment dispersion according to claim 7, wherein the peripheral speed of the cylindrical rotor is 9 m / s or more and 20 m / s or less.

9. In the media disperser in the first and second steps, the screen-type media separation unit is provided inside the cylindrical rotor, any one of claims 1 to 8. A method for producing the pigment dispersion described in the section.

10. The media disperser in the first and second steps is a disperser that circulates and disperses the mixture. A method for producing a pigment dispersion according to any one of claims 1 to 9, wherein, when the effective volume of the media disperser is V, the volume of the mixture to be dispersed by the media disperser is v, and the operating time is t, the residence time RT (= V / v × t) during which the mixture remains in the media disperser is 0.5 minutes or more and 3 minutes or less.

11. A step of forming aggregated particles by agglomerating at least the resin particles and the organic pigment in a dispersion containing resin particles and an organic pigment obtained by the method for producing a pigment dispersion according to any one of claims 1 to 10, The process involves heating the dispersion of aggregated particles to fuse and combine the aggregated particles to form toner particles, A method for manufacturing toner for electrostatic image developing having the following characteristics.

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