JP2018054892A - Toner for electrostatic latent image development and method for producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a toner for electrostatic latent image development capable of preventing the occurrence of low-temperature offset while improving low-temperature fixability.SOLUTION: There is provided a toner for electrostatic latent image development which comprises a plurality of toner particles having a toner core and a shell layer for covering a surface of the toner core. A plurality of first recesses are formed on the surface of the toner core. The shell layer exists both in an inside area of the first recesses and an outside area of the first recesses in a surface area of the toner core. Second recesses corresponding to the first recesses are formed on the surface of the toner particles. The number of second recesses per unit area of the surface area of the toner particles is 0.30 pieces/μm. A plurality of inorganic particles containing an inorganic material exist in the inside area of the first recesses of an interface between the toner core and the shell layer. The inorganic particles have a thermal conductivity of 40 W/m K or more. The inorganic particles have a number average primary particle diameter of 100 nm or less.SELECTED DRAWING: Figure 3

Description

  The present invention relates to an electrostatic latent image developing toner and a method for producing the same.

  Toners are required to have improved low-temperature fixability (see, for example, Patent Document 1). The toner described in Patent Document 1 contains, as a binder resin, a polyester resin and an inorganic filler having a higher thermal conductivity than the polyester resin.

JP 2012-98386 A

  However, when the content of the inorganic filler (hereinafter simply referred to as “inorganic filler”) having a higher thermal conductivity than the main component of the binder resin in the binder resin increases, the viscosity of the toner increases. When the content of the inorganic filler in the binder resin is large, if the dispersibility of the inorganic filler in the binder resin is low, the viscosity of the toner further increases.

  In general, when toner is fixed on a printing paper using a fixing roller, the toner is pressed on the printing paper against the fixing roller. As a result, the toner is deformed and fixed to the printing paper. Therefore, if the viscosity of the toner is high, the adhesive force between the toner and the fixing roller increases when pressed by the fixing roller, and as a result, low temperature offset is likely to occur. As described above, when an inorganic filler is contained in the binder resin for the purpose of improving the low-temperature fixability of the toner, a low-temperature offset tends to occur.

  When the low temperature offset occurs, a part of the toner image formed on the printing paper is removed, and the toner contained in the removed toner image adheres to the fixing roller. When trying to fix a new toner using the fixing roller to which the toner is attached, the new toner is pressed against the fixing roller while being sandwiched between the toner attached to the fixing roller and the printing paper. Therefore, when a new toner is fixed using a fixing roller to which toner is attached, a new toner is applied from the fixing roller to a case where a new toner is fixed using a fixing roller to which no toner is attached. The pressure applied is reduced. Therefore, when a new toner is fixed using the fixing roller to which the toner is attached, the new toner is difficult to be deformed, and as a result, it is difficult to be fixed on the printing paper. Thus, when low temperature offset occurs, the developability of the toner is reduced. Therefore, it is required to prevent the occurrence of low temperature offset.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a toner for developing an electrostatic latent image capable of preventing low temperature offset while improving low temperature fixability. It is. Another object of the present invention is to provide a method for producing a toner for developing an electrostatic latent image capable of preventing low temperature offset while improving low temperature fixability.

The electrostatic latent image developing toner according to the present invention includes a plurality of toner particles including a toner core and a shell layer covering the surface of the toner core. A plurality of first recesses are formed on the surface of the toner core. The shell layer exists in both the inner region of the first recess and the outer region of the first recess in the surface region of the toner core. A second recess corresponding to the first recess is formed on the surface of the toner particles. The number of the second recesses per unit area of the surface area of the toner particles is 0.30 / μm ² or more. A plurality of inorganic particles containing an inorganic material are present in an inner region of the first recess in the interface between the toner core and the shell layer. The thermal conductivity of the inorganic particles is 40 W / m · K or more. The number average primary particle diameter of the inorganic particles is 100 nm or less.

  The method for producing a toner for developing an electrostatic latent image according to the present invention includes a step of preparing a toner core, and a step of preparing an aqueous medium that includes the prepared toner core and a shell material and has a pH of 3 to 6. And a step of raising the temperature of the prepared aqueous medium to a predetermined target temperature, and a step of keeping the temperature of the aqueous medium at the target temperature after the temperature raising step is completed. The step of preparing the toner core was obtained in a first mixing step of mixing an amorphous polyester resin having a softening point not higher than the target temperature and inorganic particles containing an inorganic material, and the first mixing step. A second mixing step of mixing the mixture with an amorphous polyester resin having a softening point higher than the target temperature. The thermal conductivity of the inorganic particles is 40 W / m · K or more. The number average primary particle diameter of the inorganic particles is 100 nm or less. The temperature raising step further includes a step of changing the pH of the aqueous medium to 8 or more and 12 or less when the temperature of the aqueous medium reaches a pH change temperature. The pH change temperature is lower than the target temperature.

  According to the toner for developing an electrostatic latent image of the present invention, it is possible to prevent the occurrence of a low temperature offset while improving the low temperature fixability.

It is a figure which shows an example of the cross-section of the toner particle contained in the electrostatic latent image developing toner according to the embodiment of the present invention. FIG. 2 is a plan view showing a partial region of a surface region of toner particles shown in FIG. 1. It is III-III sectional drawing in FIG.

  An embodiment of the present invention will be described. In the following, the evaluation results (values indicating shape, physical properties, etc.) relating to the toner core, toner particles, toner base particles, or external additives are the number average of the values measured for a considerable number of particles unless otherwise specified. It is. The toner base particles mean toner particles to which no external additive is added.

The number average particle diameter of the powder is the number average value of the equivalent circle diameter of primary particles (diameter of a circle having the same area as the projected area of the particles) measured using a microscope unless otherwise specified. It is. Unless otherwise specified, the measured volume median diameter (D ₅₀ ) of the powder is based on the Coulter principle (pore electrical resistance method) using “Coulter Counter Multisizer 3” manufactured by Beckman Coulter, Inc. Based on the measured value.

  Moreover, each measured value of an acid value and a hydroxyl value is a value measured according to "JIS (Japanese Industrial Standard) K0070-1992" unless otherwise specified. Moreover, each measured value of a number average molecular weight (Mn) and a mass average molecular weight (Mw) is the value measured using the gel permeation chromatography, if not prescribed | regulated at all. The glass transition point (Tg) and melting point (Mp) are values measured using a differential scanning calorimeter (“DSC-6220” manufactured by Seiko Instruments Inc.) unless otherwise specified. Moreover, the softening point (Tm) is a value measured using a Koka type flow tester (“CFT-500D” manufactured by Shimadzu Corporation) unless otherwise specified.

  In addition, a compound and a derivative thereof may be generically named by adding “system” after the compound name. When the name of a polymer is expressed by adding “system” after the compound name, it means that the repeating unit of the polymer is derived from the compound or a derivative thereof. Acrylic and methacrylic are sometimes collectively referred to as “(meth) acrylic”.

[Configuration of electrostatic latent image developing toner according to the embodiment]
The electrostatic latent image developing toner according to the present embodiment includes a plurality of toner particles including a toner core and a shell layer that covers the surface of the toner core. A plurality of first recesses are formed on the surface of the toner core. The shell layer exists in both the inner region of the first recess and the outer region of the first recess in the surface region of the toner core. A second concave portion corresponding to the first concave portion is formed on the surface of the toner particles. The number of the second recesses per unit area of the surface area of the toner particles is 0.30 / μm ² or more. A plurality of inorganic particles containing an inorganic material are present in the inner region of the first recess in the interface between the toner core and the shell layer. The thermal conductivity of the inorganic particles is 40 W / m · K or more. The number average primary particle diameter of the inorganic particles is 100 nm or less.

  Here, the number of second recesses per unit area of the surface area of the toner particles is determined using a field emission scanning electron microscope (FE-SEM) (for example, “JSM-7600F” manufactured by JEOL Ltd.). It is obtained by observing the entire surface of the particle. When the toner particles contain an external additive, it is preferable to observe the entire surface of the toner particles (toner base particles) from which the external additive has been removed. In the present exemplary embodiment, a hole having a depth of 100 nm or more is referred to as a “recessed portion” in order to distinguish the minute unevenness on the surface of the toner core that is naturally formed without intention from the first recessed portion and the second recessed portion. In the following description, the “first recess” is referred to as a “base recess” and the “second recess” is referred to as a “surface recess”.

  In addition, by observing a cross-sectional TEM photograph of the toner particles using a transmission electron microscope (TEM, for example, “H-7100FA” manufactured by Hitachi High-Technologies Corporation), the inorganic particles are exposed to a concave portion of the interface between the toner core and the shell layer. It can be checked whether or not it exists in the inner area. When the toner particles contain an external additive, it is preferable to observe a cross-sectional TEM photograph of the toner particles (toner base particles) from which the external additive has been removed.

  Moreover, the heat conductivity of an inorganic particle can be calculated | required based on the measuring method (heat flow meter method) of the thermal resistance and heat conductivity of a heat insulating material as described in JIS A 1412-2: 1999.

  The number average primary particle diameter of the inorganic particles is the number average value of the equivalent-circle diameters of the primary particles measured by observing the surface of the toner particles using a microscope (for example, a scanning electron microscope). .

  The electrostatic latent image developing toner according to the present embodiment (hereinafter sometimes referred to as toner) includes a plurality of toner particles having the above-described configuration. Thereby, it is possible to prevent the occurrence of the low temperature offset while improving the low temperature fixing property of the toner. In the following, the toner according to the exemplary embodiment will be described in detail after describing the problems of the conventional toner and the matters studied by the present inventor in order to solve the problems.

  Conventionally, when an inorganic material having a high thermal conductivity is contained in the binder resin for the purpose of improving the low-temperature fixability of the toner, a low-temperature offset is likely to occur. The present inventor has intensively studied the reason why the above-described problems are caused in order to provide a toner capable of improving the low-temperature fixability and preventing the occurrence of low-temperature offset. As a result, the following views were derived.

  In the case where an inorganic material having high thermal conductivity is present inside the toner particles, the effect of incorporating the inorganic material having high thermal conductivity into the toner particles (that is, improving the low-temperature fixability of the toner) can be obtained. hard. Therefore, in order to improve the low-temperature fixability of the toner, it is necessary to increase the content of the inorganic material having a high thermal conductivity. However, when the content of the inorganic material having high thermal conductivity is increased, the viscosity of the toner is increased, and as a result, low temperature offset is likely to occur.

  Based on such a view, the present inventor has attempted to optimize the position of the inorganic material having a high thermal conductivity in the toner particles. Further, it has been found that if an inorganic material having a high thermal conductivity is disposed at a specific position of the toner particles, the low temperature fixing property of the toner can be improved and the occurrence of the low temperature offset can be prevented.

  Specifically, in the toner according to the exemplary embodiment, inorganic particles having a thermal conductivity of 40 W / m · K or more (hereinafter referred to as inorganic particles having a high thermal conductivity) are the first among the interfaces between the toner core and the shell layer. 1 exists in the inner region of the recess. As a result, it is possible to effectively obtain the effect obtained by including the inorganic particles having high thermal conductivity in the toner particles. Specifically, the low-temperature fixability of the toner can be effectively improved. In consideration of the availability of inorganic particles having high thermal conductivity, the thermal conductivity of inorganic particles having high thermal conductivity is preferably 200 W / m · K or less.

  As described above, since the inorganic particles having high thermal conductivity exist in the inner region of the base recess in the interface between the toner core and the shell layer, it is not necessary to increase the content of the inorganic particles having high thermal conductivity in the toner particles. The low-temperature fixability of the toner can be effectively improved. For example, when the content of the inorganic particles having high thermal conductivity in the toner particles is 15 parts by mass or less with respect to the toner core of 100 parts by mass, the low-temperature fixability of the toner can be effectively improved. Therefore, in this embodiment, it is possible to prevent an increase in the viscosity of the toner even though the toner particles contain inorganic particles having a high thermal conductivity. Therefore, the occurrence of low temperature offset can be prevented. In this way, the presence of inorganic particles with high thermal conductivity in the inner region of the underlying recess in the interface between the toner core and shell layer effectively increases the low-temperature fixability of the toner and prevents the occurrence of low-temperature offset. it can. From the viewpoint of more effectively increasing the low-temperature fixability of the toner, the content of inorganic particles having high thermal conductivity in the toner particles may be 0.5 parts by mass or more with respect to 100 parts by mass of the toner core. preferable.

In the toner according to this embodiment, the number of surface recesses per unit area of the surface area of the toner particles is 0.30 / μm ² or more. Here, the surface recesses are formed on the surface of the toner particles corresponding to the base recesses. Therefore, if the number of surface recesses per unit area of the toner particle surface area is 0.30 / μm ² or more, the number of base recesses per unit area of the toner core surface area is 0.30 / μm ^2. That's it. A plurality of inorganic particles having high thermal conductivity exist in the inner region of the base recess in the interface between the toner core and the shell layer. Therefore, if the number of surface recesses per unit area of the surface area of the toner particles is 0.30 / μm ² or more, the thermal conductivity in the inner area of the underlying recess in the interface between the toner core and the shell layer. It is possible to secure a location where high inorganic particles exist. Therefore, the low-temperature fixability of the toner can be effectively improved. In addition, if the location where the inorganic particles having high thermal conductivity exist in the inner region of the base recess in the interface between the toner core and the shell layer can be secured, the inorganic particles having high thermal conductivity can be prevented from existing inside the toner core. . Therefore, the occurrence of low temperature offset can be prevented. Thus, even when the number of surface recesses per unit area of the surface area of the toner particles is 0.30 / μm ² or more, the low temperature fixing property of the toner is effectively improved and the occurrence of the low temperature offset is prevented. it can. If the number of surface recesses per unit area of the surface area of the toner particles is too large, the heat resistant storage stability of the toner may be reduced due to the formation of the surface recesses. Therefore, the number of surface recesses per unit area of the surface area of the toner particles is preferably 1.0 piece / μm ² or less, more preferably 0.60 piece / μm ² or less.

  In the toner according to the exemplary embodiment, the number average primary particle diameter of inorganic particles having high thermal conductivity is 100 nm or less. Accordingly, a predetermined amount of inorganic particles having high thermal conductivity can be present in the inner region of the base recess in the interface between the toner core and the shell layer. Therefore, the low-temperature fixability of the toner can be effectively improved. Further, if a predetermined amount of inorganic particles having high thermal conductivity can be present in the inner region of the base recess in the interface between the toner core and the shell layer, the inorganic particles having high thermal conductivity are present inside the toner core. Can be prevented. Therefore, the occurrence of low temperature offset can be prevented. Thus, even when the number average primary particle diameter of the inorganic particles having high thermal conductivity is 100 nm or less, the low temperature fixing property of the toner can be effectively enhanced and the occurrence of the low temperature offset can be prevented. In view of the availability of inorganic particles, the number average primary particle size of the inorganic particles is preferably 20 nm or more.

  Preferably, the inorganic material contained in the inorganic particles having high thermal conductivity is at least one of aluminum nitride, boron nitride, aluminum oxide, and silicon carbide. Thereby, the inorganic particle whose heat conductivity is 40 W / m * K or more can be provided. For example, inorganic particles containing 80% by mass or more of at least one of aluminum nitride, boron nitride, aluminum oxide, and silicon carbide easily have a thermal conductivity of 40 W / m · K or more. More preferably, at least one of particles made of aluminum nitride, particles made of boron nitride, particles made of aluminum oxide, and particles made of silicon carbide is used as the inorganic particles having high thermal conductivity.

Preferably, the volume resistivity of the inorganic particles having a high thermal conductivity is 1.0 × 10 ¹⁴ Ω · cm or more. As a result, a decrease in the electrical resistance of the toner can be prevented, and a decrease in the toner charge amount can be prevented. Therefore, the charging stability of the toner can be improved. The toner having excellent charge stability means a characteristic that the toner charge amount distribution is sharp, a property that the toner charge amount can be maintained at a desired charge amount when starting to form an image using the toner, and the toner. It means a toner having the characteristic that the charge amount of the toner can be maintained at a desired charge amount when images are continuously formed.

  The volume specific resistance value of the inorganic particles having high thermal conductivity can be determined according to the following method. First, inorganic particles having high thermal conductivity are put into a measurement cell of an electric resistance meter (for example, “R6561” manufactured by Advantest Corporation). Next, a load of 1 kg is applied to the inorganic particles (inorganic particles having high thermal conductivity) in the measurement cell for 1 minute. Subsequently, a DC voltage of 10 V is applied to the inorganic particles in the measurement cell, and the electrical resistance of the inorganic particles is measured. The volume specific resistance value of the inorganic particles is calculated from the measured electric resistance value and the thickness of the inorganic particles at the time of measuring the electric resistance.

Considering availability, it is preferable that the volume resistivity of the inorganic particles having high thermal conductivity is 1.0 × 10 ¹⁷ Ω · cm or less. If the volume resistivity of the inorganic particles having high thermal conductivity is 1.0 × 10 ¹⁷ Ω · cm or less, an excessive increase in the electrical resistance of the toner can be prevented. Therefore, it is possible to prevent the toner from being charged excessively, and therefore, the charging stability of the toner can be further improved.

More preferably, the inorganic material contained in the inorganic particles having high thermal conductivity is at least one of aluminum nitride, boron nitride, and aluminum oxide. Thereby, it is possible to provide inorganic particles having a thermal conductivity of 40 W / m · K or more and a volume specific resistance value of 1.0 × 10 ¹⁴ Ω · cm or more. For example, inorganic particles containing 80% by mass or more of at least one of aluminum nitride, boron nitride, and aluminum oxide easily have a thermal conductivity of 40 W / m · K or more, and 1.0 × 10 ^It tends to have a volume resistivity of ¹⁴ Ω · cm or more. More preferably, at least one of particles made of aluminum nitride, particles made of boron nitride, and particles made of aluminum oxide is used as the inorganic particles having high thermal conductivity.

Specific examples of the inorganic particles having high thermal conductivity in the case where “a plurality of inorganic particles having high thermal conductivity are present in the inner region of the underlying recess in the interface between the toner core and the shell layer” are as follows. Examples to the third example are given. The toner particles preferably each include at least one of inorganic particles having high thermal conductivity in the first to third examples. For example, one toner particle can include the inorganic particles having high thermal conductivity in the first example and the inorganic particles having high thermal conductivity in the second example. The toner includes toner particles containing inorganic particles having high thermal conductivity in the first example and inorganic particles having high thermal conductivity in the second example, inorganic particles having high thermal conductivity in the second example, and third example. And toner particles containing inorganic particles having a high thermal conductivity.
First example: Inorganic particles having a high thermal conductivity exist in the toner core and contact the interface between the toner core and the shell layer.
Second example: Inorganic particles having high thermal conductivity exist in the shell layer. At this time, the inorganic particles having high thermal conductivity may be in contact with the interface between the toner core and the shell layer, or exist in the shell layer and outside the toner particle in the radial direction from the interface between the toner core and the shell layer. May be. In addition, among the inorganic particles having a high thermal conductivity, a portion located on the outer side in the radial direction of the toner particles may be exposed from the shell layer.
Third example: Of the inorganic particles having high thermal conductivity, the portion located inside the toner particle in the radial direction exists in the toner core, and the portion located outside in the radial direction of the toner particle exists in the shell layer. .

  In the present embodiment, the thickness of the shell layer is preferably 1 nm or more and 50 nm or less. Here, the depth of the base recess is 100 nm or more. Therefore, if the thickness of the shell layer is 1 nm or more and 50 nm or less, the thickness of the shell layer is sufficiently smaller than the depth of the base recess. Therefore, the surface recess is easily formed.

  If the thickness of the shell layer is sufficiently smaller than the depth of the base recess, the depth of the surface recess is considered to be substantially the same as the depth of the base recess. Therefore, when the depth of the base recess is 100 nm or more and the thickness of the shell layer is 1 nm or more and 50 nm or less, the depth of the surface recess is 100 nm or more. Moreover, in order to ensure sufficient formation ease of a surface recessed part, it is preferable that the depth of a base recessed part is 3 micrometers or less.

  The thickness of the shell layer means the dimension of the shell layer in the radial direction of the toner particles, and is measured, for example, according to the method described in the examples.

  In the present embodiment, the ratio of the area of the toner core covered by the shell layer in the surface area of the toner core (hereinafter referred to as the overall shell coverage) is preferably 30% or more and 80% or less. Here, the shell layer is more excellent in heat resistance than the toner core. Therefore, melting of the shell layer in the surface region of the toner core can be prevented even when heat is applied to the toner during image formation.

  In the present embodiment, the ratio of the area of the inner region covered by the shell layer in the inner region of the base recess (hereinafter referred to as the recess shell coverage) is preferably 30% or more and 80% or less. Here, the shell layer is more excellent in heat resistance than the toner core. Therefore, even if heat is applied to the toner during image formation, the shell layer in the inner region of the base recess can be prevented from melting.

  The total shell coverage (unit:%) is expressed by the formula “total shell coverage = 100 × area of the surface area of the toner core covered by the shell layer / area of the entire surface of the toner core”. An overall shell coverage of 100% means that the entire surface of the toner core is covered with the shell layer.

  The concave shell coverage (unit:%) is expressed by the formula “recess shell coverage = 100 × area of the inner region of the base concave portion covered by the shell layer / area of the entire inner region of the base concave portion”. When the concave shell coverage is 100%, it means that the entire inner region of the base concave is covered with the shell layer.

  The total shell coverage and the recessed shell coverage can each be determined according to the following method. First, Ru dyeing is performed on toner particles (for example, toner mother particles) that have not been subjected to external addition processing. Of the surface area of the toner core, the area covered with the shell layer is more easily dyed with ruthenium than the area not covered with the shell layer. The dyed toner particles are observed at a magnification of 50000 using a field emission scanning electron microscope (FE-SEM) (for example, “JSM-7600F” manufactured by JEOL Ltd.) to obtain a reflected electron image of the toner particles. .

Using the image analysis software (for example, “WinROOF” manufactured by Mitani Shoji Co., Ltd.), the obtained reflected electron image is binarized. Then, an area S _{A1 of the} entire reflected electron image of the toner particles and an area S _B1 of a relatively bright area in the reflected electron image are obtained, and an overall shell coverage (unit:%) is calculated according to the following formula.
Total shell coverage = 100 × area S _B1 / area S _A1

Except for changing the observation magnification from 50000 times to 100000 times, the area S _A2 of the inner region of the base recess and the inner region of the base recess are relatively bright in the same manner as the method for measuring the overall shell coverage. The area S _{B2 of the} region is obtained. And the recessed part shell coverage (unit:%) is computed according to a following formula.
Recessed shell coverage ratio = 100 × area S _B2 / area S _A2

  Hereinafter, an example of the configuration of the toner particles contained in the toner according to the present embodiment will be described with reference to FIGS. FIG. 1 is a diagram illustrating an example of a cross-sectional structure of toner base particles 10 included in toner particles. FIG. 2 is a plan view showing a partial region of the surface region of toner base particle 10 shown in FIG. 3 is a cross-sectional view taken along the line III-III in FIG.

  As shown in FIG. 1, the toner base particle 10 includes a toner core 11 and a shell layer 12 that covers the surface of the toner core 11. The shell layer 12 partially covers the surface of the toner core 11.

As shown in FIGS. 2 and 3, base recesses H <b> 11 to H <b> 14 are formed on the surface of the toner core 11. In the surface region of the toner core 11, the shell layer 12 exists in the outer region of the base recesses H11 to H14, the inner region of the base recess H12, and the inner region of the base recess H13. However, the shell layer 12 does not exist in the inner region of the base recess H11 and the inner region of the base recess H14. For this reason, the surface of the toner base particle 10 is formed with a base recess H11, a surface recess H22 corresponding to the base recess H12, a surface recess H23 corresponding to the base recess H13, and a base recess H14. The number of surface recesses per unit area of the surface area of the toner base particles 10 is 0.30 / μm ² or more.

  3 will be described before the toner base particles 10 are further described with reference to FIG. FIG. 3 shows a state in which the resin particles contained in the shell layer 12 are connected to form a film as the shell layer 12. However, in a part of the shell layer 12, the resin particles contained in the shell layer 12 may remain in a spherical shape. Further, when the resin particles contained in the shell layer 12 are connected to form a film, the resin particles may become flat. The shell layer 12 may contain such flat resin particles.

  Regarding the base recess H11, the range R1 indicates the range of the inner region of the base recess H11, and the depth D1 indicates the depth of the base recess H11. Regarding the base recess H13, the range R3 indicates the range of the inner region of the base recess H13, and the depth D3 indicates the depth of the surface recess H23 corresponding to the base recess H13.

  The toner base particles 10 will be further described with reference to FIG. As shown in FIG. 3, the toner base particles 10 further include inorganic particles 15 a to 15 d having high thermal conductivity. The inorganic particles 15a to 15d having high thermal conductivity are present in the inner regions of the base recess H12 and the base recess H13 in the interface 13 between the toner core 11 and the shell layer 12, respectively.

  The inorganic particles 15a having a high thermal conductivity correspond to the inorganic particles having a high thermal conductivity in the first example. Specifically, the inorganic particles 15 a having high thermal conductivity exist in the toner core 11 and come into contact with the interface 13 between the toner core 11 and the shell layer 12.

  The inorganic particles 15b having a high thermal conductivity correspond to the inorganic particles having a high thermal conductivity in the second example. Specifically, the inorganic particles 15 b having high thermal conductivity are present in the shell layer 12 and are in contact with the interface 13 between the toner core 11 and the shell layer 12. The inorganic particles 15b having a high thermal conductivity are not in contact with the interface 13 between the toner core 11 and the shell layer 12, and are within the shell layer 12 and more than the toner base particle than the interface 13 between the toner core 11 and the shell layer 12. Ten radial outer sides X1 may exist. In addition, in the inorganic particles 15 b having high thermal conductivity, a portion located on the radially outer side X <b> 1 of the toner base particles 10 may be exposed from the shell layer 12.

  The inorganic particles 15c and 15d having high thermal conductivity correspond to the inorganic particles having high thermal conductivity in the third example. Specifically, a portion of each of the inorganic particles 15 c and 15 d having high thermal conductivity located on the radially inner side X <b> 2 of the toner base particle 10 exists in the toner core 11, and the radially outer side of the toner base particle 10. A portion located at X <b> 1 exists in the shell layer 12. The inorganic particles 15 c having high thermal conductivity are in contact with the surface 12 </ b> A of the shell layer 12. The inorganic particles 15d having a high thermal conductivity are not in contact with the surface 12A of the shell layer 12, and are present on the radially inner side X2 of the toner base particles 10 with respect to the surface 12A of the shell layer 12. The example of the configuration of the toner particles included in the toner according to the present embodiment has been described above with reference to FIGS.

  Heretofore, an example of the configuration of the toner according to the present embodiment and the configuration of the toner particles included in the toner according to the present embodiment has been described. The toner particles contained in the toner according to the present embodiment may be toner particles after external addition processing or toner base particles. The toner according to the exemplary embodiment may include both the toner particles after the external addition process and the toner base particles.

[Manufacture of Toner According to this Embodiment]
The following first to third methods can be considered as the toner manufacturing method according to the present embodiment, but it is preferable to manufacture the toner according to the present embodiment according to a third method described later. Hereinafter, the first to third methods will be described in order.

(First method)
In the first method, first, a base recess is formed on the surface of the toner core. Next, inorganic particles having a high thermal conductivity are fixed to the inner region of the base recess. Subsequently, a shell layer is formed in the inner region of the base recess and the outer region of the base recess.

  However, in the first method, it is difficult to manufacture the toner according to this embodiment. Specifically, it is difficult for the shell layer to be formed in the inner region of the base recess. Further, if the thickness of the shell layer is increased in order to ensure sufficient adhesive strength between the inner region of the base recess and the shell layer, the recess is hardly formed on the surface of the toner particles after the shell layer is formed. That is, it is difficult to form a surface recess.

  In addition, since the inner region of the base recess (especially the side wall of the base recess) is inclined, it is difficult to fix inorganic particles having high thermal conductivity to the inner region of the base recess. If the inorganic particles having high thermal conductivity are not sufficiently fixed to the inner region of the base recess, the inorganic particles having high thermal conductivity may move during the formation of the shell layer. Therefore, in the manufactured toner particles, inorganic particles having high thermal conductivity may not be present in the inner region of the base recess in the interface between the toner core and the shell layer.

(Second method)
In the second method, first, inorganic particles having a high thermal conductivity are fixed to a part of the surface region of the toner core. Next, a shell layer is formed on the surface of the toner core. Subsequently, a base recess is formed in a portion of the surface region of the toner core where inorganic particles having high thermal conductivity are fixed.

  However, even with the second method, it is difficult to manufacture the toner according to this embodiment. Specifically, since the base recess is formed after the shell layer is formed, the shell layer may be peeled off when the base recess is formed. Further, since the toner core is a sphere, it is difficult to fix inorganic particles having high thermal conductivity to a part of the surface region of the toner core. If the inorganic particles having a high thermal conductivity are not sufficiently fixed to a part of the surface region of the toner core, the inorganic particles having a high thermal conductivity may move during the formation of the shell layer or the formation of the underlying recess. Therefore, in the manufactured toner particles, inorganic particles having high thermal conductivity may not be present in the inner region of the base recess in the interface between the toner core and the shell layer.

  The inventor diligently studied a method by which the toner according to the exemplary embodiment can be easily manufactured. Then, if the toner is produced according to the third method shown below, it is concluded that the formation of the base concave portion with respect to the toner core, the placement of the inorganic particles having high thermal conductivity at the predetermined position, and the formation of the shell layer proceed simultaneously. It came to.

(Third method: manufacturing method of toner for developing electrostatic latent image according to this embodiment)
In other words, the method for producing a toner for developing an electrostatic latent image according to the present embodiment prepares an aqueous medium including a step of preparing a toner core, the prepared toner core and a shell material, and having a pH of 3 to 6. And a step of raising the temperature of the prepared aqueous medium to a predetermined target temperature, and a step of maintaining the temperature of the aqueous medium at the target temperature after the temperature raising step is completed. The step of preparing the toner core includes a first mixing step of mixing an amorphous polyester resin having a softening point equal to or lower than a target temperature and inorganic particles containing an inorganic material, and a mixture obtained in the first mixing step. And a second mixing step of mixing an amorphous polyester resin having a softening point higher than the target temperature. The thermal conductivity of the inorganic particles is 40 W / m · K or more. The number average primary particle diameter of the inorganic particles is 100 nm or less. The temperature raising step further includes a step of changing the pH of the aqueous medium to 8 or more and 12 or less when the temperature of the aqueous medium reaches the pH change temperature. The pH change temperature is lower than the target temperature.

  In the toner manufacturing method according to the present embodiment, the formation of the base recess due to the hydrolysis of the polyester resin and the formation of the shell layer proceed simultaneously. Therefore, the shell layer is formed not only in the outer region of the base recess but also in the inner region of the base recess.

  In the toner manufacturing method according to this embodiment, an amorphous polyester resin having a low softening point and inorganic particles having a high thermal conductivity are mixed. Therefore, inorganic particles having a high thermal conductivity are dispersed in an amorphous polyester resin having a low softening point. Here, an amorphous polyester resin having a low softening point is more easily hydrolyzed at a lower temperature than an amorphous polyester resin having a high softening point. Therefore, the base recess is more easily formed in an amorphous polyester resin having a lower softening point than in an amorphous polyester resin having a higher softening point. In addition, when the amorphous polyester resin is hydrolyzed, the inorganic particles having a high thermal conductivity remain without being hydrolyzed or dissolved. From these facts, when the base recess was formed because the non-crystalline polyester resin having a low softening point was hydrolyzed, the inorganic particles having a high thermal conductivity dispersed in the non-crystalline polyester resin having a low softening point were used. Among them, inorganic particles having a high thermal conductivity existing in the vicinity of the surface of the toner core are exposed in the inner region of the base recess. Therefore, in the manufactured toner, inorganic particles having high thermal conductivity are present in the inner region of the base recess in the interface between the toner core and the shell layer. Hereinafter, the toner manufacturing method according to the exemplary embodiment will be described in more detail.

(Preferred manufacturing method of toner according to this embodiment)
A preferred method for producing a toner according to the exemplary embodiment includes a toner core preparation step and a shell layer formation step. The preferred method for producing the toner according to the exemplary embodiment may further include at least one of a filtration step, a drying step, and an external addition step.

(Preparation of toner core)
The toner core preparation step includes a first mixing step and a second mixing step. Here, if the toner core is produced by a pulverization method or an agglomeration method, the toner core can be easily obtained. Therefore, hereinafter, the toner core preparation process will be described separately for the case where the toner core is manufactured by the pulverization method and the case where the toner core is manufactured by the aggregation method.

(Manufacture of toner by grinding method)
(First mix)
A non-crystalline polyester resin having a softening point equal to or lower than a first temperature (corresponding to a target temperature described later) (hereinafter referred to as LTm-non-crystalline polyester resin) and inorganic particles having high thermal conductivity are mixed. . In the mixture thus obtained (hereinafter referred to as the first mixture), inorganic particles having high thermal conductivity are uniformly dispersed in the LTm-amorphous polyester resin. As the LTm-amorphous polyester resin, for example, an amorphous polyester resin having a softening point of 80 ° C. or lower can be used, and preferably an amorphous polyester resin having a softening point of 70 ° C. or lower can be used.

(Second mixture)
A 1st mixture and the amorphous polyester resin (henceforth described as HTm-amorphous polyester resin) which has a softening point higher than 1st temperature are mixed. At this time, you may further mix an internal additive with respect to the mixture containing a 1st mixture and HTm-amorphous polyester resin. As the internal additive, for example, at least one of a colorant, a release agent, a charge control agent, and magnetic powder can be used. As the HTm-noncrystalline polyester resin, for example, an amorphous polyester resin having a softening point of 100 ° C. or higher can be used.

(Melt kneading, grinding, classification)
After the obtained mixture (hereinafter referred to as the second mixture) is melt-kneaded, the obtained melt-kneaded product is pulverized and classified. As a result, a toner core having a desired particle size can be obtained. The toner core may be manufactured according to the following method. The first mixture is melt-kneaded and the resulting melt-kneaded product is pulverized. The pulverized product thus obtained and HTm-amorphous polyester resin are mixed to prepare a second mixture.

(Manufacture of toner core by agglomeration method)
(First mixing, second mixing)
LTm-amorphous polyester resin and inorganic particles having high thermal conductivity are mixed to obtain a first mixture. The obtained 1st mixture and HTm-amorphous polyester resin are mixed, and a 2nd mixture is obtained.

(Aggregation)
In an aqueous medium containing fine particles of each of the obtained second mixture, release agent, and colorant, these particles are aggregated to a desired particle size. Thereby, agglomerated particles containing the second mixture, the release agent, and the colorant are formed. The obtained aggregated particles are heated to unitize the components contained in the aggregated particles. As a result, a toner core dispersion is obtained. Thereafter, unnecessary substances are removed from the dispersion liquid of the toner core. Surfactant is mentioned as an unnecessary substance. In this way, a toner core having a desired particle size is obtained.

(Toner core preparation: material content)
Regardless of the manufacturing method of the toner core, the content of each of the LTm-noncrystalline polyester resin and the HTm-noncrystalline polyester resin is preferably the following content.

  The proportion of LTm-amorphous polyester resin in the resin contained in the toner core is preferably 20% by mass or more. Thereby, in 1st mixture, content of LTm-amorphous polyester resin tends to increase rather than content of an inorganic particle with high heat conductivity. This is because the inorganic particles having a high thermal conductivity are preferably contained in an amount of 15 parts by mass or less with respect to 100 parts by mass of the toner core. In the first mixture, if the content of the LTm-amorphous polyester resin is larger than the content of the inorganic particles having a high thermal conductivity, the inorganic particles having a high thermal conductivity are converted to the LTm-amorphous polyester. It becomes easy to disperse uniformly in the resin. More preferably, the proportion of the LTm-amorphous polyester resin in the resin contained in the toner core is 50% by mass or more.

  More preferably, the proportion of the LTm-amorphous polyester resin in the resin contained in the toner core is 95% by mass or less. Accordingly, when the resin contained in the toner core is composed of LTm-amorphous polyester resin and HTm-amorphous polyester resin, among the resins contained in the toner core, HTm-amorphous polyester resin. The ratio occupied by is 5% by mass or more. Here, HTm-amorphous polyester resin is excellent in heat resistance compared with LTm-amorphous polyester resin. Therefore, if the ratio of the LTm-amorphous polyester resin in the resin contained in the toner core is 95% by mass or less, the heat resistant storage stability of the toner particles can be improved. For example, even when a plurality of toner particles are stored at a high temperature, melting of the toner core can be prevented, so that aggregation of the plurality of toner particles can be prevented.

  From the above, the proportion of the LTm-amorphous polyester resin in the resin contained in the toner core is preferably 20% by mass or more, more preferably 20% by mass or more and 95% by mass or less, and still more preferably. It is 50 mass% or more and 95 mass% or less. Therefore, when the resin contained in the toner core is composed of LTm-amorphous polyester resin and HTm-amorphous polyester resin, among the resins contained in the toner core, HTm-amorphous polyester resin is used. The proportion occupied is preferably 5% by mass or more, more preferably 5% by mass or more and 80% by mass or less, and further preferably 5% by mass or more and 50% by mass or less.

  In addition to LTm-amorphous polyester resin, a crystalline polyester resin may be used. Here, the crystalline polyester resin is more easily hydrolyzed than the amorphous polyester resin. Therefore, if a crystalline polyester resin is used in addition to the LTm-amorphous polyester resin, hydrolysis of the resin contained in the toner core is further accelerated. Therefore, the formation of the base recess is further promoted.

(Formation of shell layer)
The shell layer forming step includes an aqueous medium preparation step, a temperature raising step, and a heat retention step. The temperature raising step includes a pH changing step.

(Formation of shell layer: preparation of aqueous medium)
In the aqueous medium preparation step, first, an aqueous medium is prepared.
The aqueous medium is a medium containing water as a main component, for example, pure water or a mixed liquid of water and a polar medium. The aqueous medium may function as a solvent. A solute may be dissolved in the aqueous medium. The aqueous medium may function as a dispersion medium. The dispersoid may be dispersed in the aqueous medium. As the polar medium in the aqueous medium, for example, an alcohol can be used, and as the alcohol, for example, methanol or ethanol can be used. The boiling point of the aqueous medium is preferably about 100 ° C. More preferably, ion exchange water is prepared as an aqueous medium.

  Subsequently, the pH of the aqueous medium is adjusted to a predetermined pH using an acidic substance. For example, the pH of the aqueous medium is adjusted to 3 or more and 6 or less using hydrochloric acid. Subsequently, the toner core obtained by the above method and the shell material are added to an aqueous medium whose pH is adjusted to 3 or more and 6 or less. As the addition amount of the shell material is increased, the thickness of the formed shell layer tends to increase.

  When the toner core and the shell material are added to the aqueous medium, the particles of the shell material are considered to adhere to the surface of the toner core in the aqueous medium. When a suspension containing particles made of water-insoluble thermoplastic resin is used as the shell material, it is considered that particles made of water-insoluble thermoplastic resin adhere to the surface of the toner core.

  Further, by forming the shell layer in an aqueous medium, it is possible to suppress dissolution or elution of the toner core component during the shell layer formation. Specifically, by forming a shell layer in an aqueous medium, dissolution or elution of the binder resin and the release agent during the formation of the shell layer can be suppressed.

  In order to uniformly adhere the shell material to the surface of the toner core, it is preferable to highly disperse the toner core in a liquid containing the shell material. In order to highly disperse the toner core in the liquid, a surfactant may be included in the liquid, or the liquid is stirred using a powerful stirring device (for example, “Hibis Disper Mix” manufactured by Primics Co., Ltd.). May be. When the toner core has an anionic property, aggregation of the toner core can be suppressed by using an anionic surfactant having the same polarity. As the anionic surfactant, for example, sulfate ester salt, sulfonate salt, phosphate ester salt, or soap can be used. In this way, an aqueous medium containing a toner core and a shell material and having a pH of 3 to 6 is prepared.

(Shell layer formation: temperature rise)
In the temperature raising step, the temperature of the aqueous medium prepared according to the above method is raised to a predetermined target temperature. Specifically, the temperature of the aqueous medium is increased to a predetermined target temperature at a predetermined speed while stirring the prepared aqueous medium. The temperature of the aqueous medium at the start of temperature rise is a temperature selected from, for example, 20 ° C. or more and 35 ° C. or less. The pH of the aqueous medium at the start of temperature increase is a pH selected from 3 to 6, for example. The rate of temperature increase is, for example, a rate selected from 0.1 ° C./min to 3.0 ° C./min, and preferably a rate selected from 0.1 ° C./min to 1.0 ° C./min. . The target temperature of the temperature increase is a temperature at which the temperature increase is stopped, for example, a temperature selected from 60 ° C. to 70 ° C.

(Temperature raising step: pH change)
When the temperature of the aqueous medium reaches the pH change temperature during the temperature increase, a pH change step is performed. In the pH changing step, when the temperature of the aqueous medium reaches the pH changing temperature, the pH of the aqueous medium is changed from 8 to 12. For example, the pH of an aqueous medium can be changed from an acidic value to an alkaline value by adding a basic substance to the aqueous medium. As a basic substance, for example, sodium hydroxide can be used. Moreover, it is preferable to change pH of an aqueous medium in a short time, for example, it is preferable to change pH of an aqueous medium within 10 second.

  It is considered that the base recess is formed by performing the pH changing step during the temperature increase of the aqueous medium. Specifically, if the pH changing step is performed during the temperature increase of the aqueous medium, the pH of the aqueous medium changes from an acidic value to an alkaline value after the temperature of the aqueous medium rises to some extent. As a result, it is considered that hydrolysis of the LTm-amorphous polyester resin contained in the toner core proceeds, and thus it is considered that a base recess is formed.

  Furthermore, when the temperature of the aqueous medium approaches the softening point of the LTm-amorphous polyester resin, the LTm-amorphous polyester resin softens. Here, the softening point of the LTm-amorphous polyester resin is equal to or lower than the target temperature for temperature increase. Moreover, it is thought that LTm-amorphous polyester resin is easily hydrolyzed even by softening. From these facts, the LTm-amorphous polyester resin has a change in pH of the aqueous medium during temperature rise (specifically, the pH of the aqueous medium changes from an acidic value to an alkaline value during the temperature rise). In addition to being softened by temperature rise, it is easily hydrolyzed. Therefore, formation of the base recess is promoted.

  Even if the LTm-amorphous polyester resin is hydrolyzed, the inorganic particles having a high thermal conductivity dispersed in the LTm-amorphous polyester resin remain without being hydrolyzed or dissolved. For this reason, when the base recess is formed, inorganic particles having high thermal conductivity existing near the surface of the toner core are exposed in the inner region of the base recess. As a result, the inorganic particles having a high thermal conductivity are present in the inner region of the base recess in the interface between the toner core and the shell layer.

  As described above, in the toner manufacturing method according to this embodiment, the LTm-non-crystalline polyester resin is hydrolyzed to form a base recess, a shell layer, and a predetermined position of inorganic particles having high thermal conductivity. The arrangement of the process proceeds simultaneously. Therefore, the toner according to the present embodiment can be manufactured relatively easily.

As described above, the base recess is formed by hydrolysis of the LTm-non-crystalline polyester resin. Therefore, if the conditions under which the LTm-amorphous polyester resin is hydrolyzed are controlled, the number of underlying recesses per unit area of the surface area of the toner core can be controlled. Here, the surface recess is formed corresponding to the base recess. Therefore, if the number of base recesses per unit area of the surface area of the toner core can be 0.30 / μm ² or more, the number of surface recesses per unit area of the surface area of the toner particles is 0.30 / It is thought that it can be set to μm ² or more.

For example, controlling at least one of the LTm-non-crystalline polyester resin material, the pH change temperature, and the pH of the aqueous medium after the pH change step (hereinafter referred to as the changed pH). Thus, the number of base recesses per unit area of the surface area of the toner core can be set to 0.30 / μm ² or more. Therefore, the number of surface recesses per unit area of the surface area of the toner particles can be 0.30 / μm ² or more. Hereinafter, the pH change temperature and the changed pH will be further described.

(PH change step: pH change temperature)
The pH change temperature is preferably higher than the temperature of the aqueous medium at the start of temperature increase. Accordingly, the resin contained in the toner core is easily softened and thus easily hydrolyzed. Therefore, formation of the base recess is promoted. In addition, with the formation of the base recess, the inorganic particles having high thermal conductivity existing near the surface of the toner core are exposed in the inner region of the base recess.

The pH change temperature is a temperature selected from, for example, 30 ° C. or more and 60 ° C. or less, preferably (LTm—softening point of non-crystalline polyester resin) ± 10 ° C., more preferably 30 ° C. or more and 40 ° C. or less. Temperature. As a result, the number of base recesses per unit area of the surface area of the toner core tends to be 0.30 / μm ² or more, so the number of surface recesses per unit area of the toner particle surface area is 0.30 / μm. It can be ² or more. Moreover, the same effect is acquired also when LTm-amorphous polyester resin whose softening point satisfy | fills the following relational expression as LTm-amorphous polyester resin is used.
pH change temperature = (LTm−softening point of non-crystalline polyester resin) ± 10 ° C.

(PH change step: pH after change)
The pH after the change is 8 or more and 12 or less. If the pH after change is 8 or more, hydrolysis of the resin contained in the toner core proceeds. Thereby, a base recess is formed. In addition, with the formation of the base recess, the inorganic particles having high thermal conductivity existing near the surface of the toner core are exposed in the inner region of the base recess. If the pH after change exceeds 12, hydrolysis of the resin contained in the toner core proceeds excessively. As a result, the base recess is excessively formed, and the number of surface recesses per unit area of the surface area of the toner particles may be excessive. As a result, the manufactured toner may cause deterioration in heat resistant storage stability. From the above, if the pH after change is 8 or more and 12 or less, the number of base recesses per unit area of the surface area of the toner core tends to be 0.30 / μm ² or more. The number of surface recesses per area can be 0.30 / μm ² or more. Preferably, the pH after the change is 8 or more and 11 or less.

(Temperature raising step: after pH changing step)
Even after the pH changing step is finished, the temperature of the aqueous medium is not stopped and the temperature of the aqueous medium is raised to a predetermined target temperature. As a result, the surface of the toner core in which the base recess is formed is covered with the shell material. Therefore, by optimizing the temperature rising time after the pH change step, the amount of shell material deposited on the surface of the toner core is optimized, and thus the thickness of the shell layer is optimized. Based on this, it is preferable to set the temperature raising time after the pH changing step. By changing at least one of the temperature increase rate, the pH change temperature, and the temperature increase target temperature, the temperature increase time after the pH change step is changed. For example, the pH change temperature is preferably lower than the target temperature for temperature increase. The difference between the pH change temperature and the target temperature for temperature increase is more preferably 10 ° C. or higher, and further preferably 30 ° C. or higher.

  As described above, in the shell layer forming step, the pH change step is performed during the temperature increase of the aqueous medium, and the temperature increase of the aqueous medium is continued even after the pH change step. Thereby, a shell layer is formed on the surface of the toner core including the inner region of the base recess while forming the base recess. In addition, by forming the base recess, inorganic particles having a high thermal conductivity existing near the surface of the toner core are exposed in the inner region of the base recess. As a result, inorganic particles having a high thermal conductivity are present in the inner region of the base recess in the interface between the toner core and the shell layer.

  For example, a suspension containing particles made of styrene-acrylic acid resin is used as the shell material, the temperature of the aqueous medium at the start of temperature increase in the temperature rising process is set to 30 ° C., and the rate of temperature increase in the temperature rising process is 1 ° C. Take the case of / min as an example. In this case, it is considered that the surface area of the toner core is sufficiently covered with the shell material when the temperature of the aqueous medium reaches 40 ° C. In addition, it is considered that the shell material starts to be immobilized on the surface of the toner core when the temperature of the aqueous medium reaches 60 ° C.

(Heat insulation)
In the heat retaining step, after the temperature raising step is completed, the temperature of the aqueous medium is maintained at a target temperature for the temperature raising for a predetermined time. The predetermined time is, for example, a time selected from 30 minutes to 4 hours. By maintaining the temperature of the aqueous medium at the target temperature for raising the temperature, the reaction is considered to proceed between the shell material adhering to the surface of the toner core and the toner core. The shell material is combined with the toner core to form a shell layer. Specifically, it is considered that a film (shell layer) having a granular feeling is formed by two-dimensionally linking the particles of the shell material on the surface of the toner core. In this way, a dispersion of toner base particles is obtained.

(Filtration)
First, cold water is added to the obtained dispersion of toner base particles, and the flask contents are cooled to room temperature (about 25 ° C.). Subsequently, the dispersion of the toner base particles is filtered using, for example, a Buchner funnel. As a result, the toner base particles are separated from the liquid, and wet cake-like toner base particles are obtained.

(Washing, drying)
The obtained wet cake-like toner base particles are washed. Subsequently, the washed toner base particles are dried.

(External)
The dried toner base particles and the external additive are mixed using a mixer (for example, FM mixer manufactured by Nippon Coke Kogyo Co., Ltd.). As a result, the external additive is physically bonded to the surface of the toner base particles. In this way, a toner containing a large number of toner particles is obtained.

  When the washed toner base particles are dried using a spray dryer, it is preferable to spray a dispersion of the external additive on the toner base particles. As a result, the dried toner base particles can be dried and externally added at the same time.

  Further, the content and order of the toner manufacturing method can be arbitrarily changed according to the required configuration or characteristics of the toner. For example, the shell material may be added to the aqueous medium at once, or may be added to the aqueous medium in a plurality of times. The toner may be sieved after the external addition step. Further, unnecessary steps may be omitted. For example, when a commercially available product can be used as a material as it is, the step of preparing the material can be omitted by using a commercially available product.

  Further, the material of the toner core and the shell material are not limited to the materials described in the following [Examples of materials of toner core, shell layer, and external additive]. For example, a derivative of the material described in the following [Examples of materials of toner core, shell layer, and external additive] may be used as the material or shell material of the toner core. A prepolymer may be used in place of the monomer. In addition, in order to obtain the materials described in the following [Exemplary materials for toner core, shell layer, and external additive], the salt, ester, hydrate, or anhydride of the compound is used as a raw material. Also good.

  In order to produce the toner efficiently, it is preferable to form a large number of toner particles simultaneously. The toner particles produced at the same time are considered to have substantially the same configuration.

[Examples of materials of toner core, shell layer, and external additive]
Hereinafter, specific examples of materials of the toner core, the shell layer, and the external additive will be described in order.

(Toner core)
The toner core contains a binder resin. The toner core may further contain at least one of a colorant, a release agent, a charge control agent, and magnetic powder.

(Toner core: Binder resin)
In the toner core, the binder resin generally occupies most of the components (for example, 85% by mass or more). For this reason, it is considered that the properties of the binder resin greatly affect the properties of the entire toner core.

  Moreover, the property (specifically, hydroxyl value, acid value, glass transition point, or softening point) of the binder resin can be adjusted by using a combination of a plurality of types of resins as the binder resin. For example, when the binder resin has an ester group, a hydroxyl group, an ether group, an acid group, or a methyl group, the toner core tends to become anionic. Further, when the binder resin has an amino group or an amide group, the toner core tends to be cationic. In order for the binder resin to have a strong anionic property, it is preferable that at least one of the acid value and the hydroxyl value of the binder resin is 10 mgKOH / g or more.

(Binder resin: Polyester resin)
The toner core preferably contains the following polyester resin.
The polyester resin is obtained by polycondensing one or more alcohols and one or more carboxylic acids. As the alcohol for synthesizing the polyester resin, for example, the following dihydric alcohol or trihydric or higher alcohol can be suitably used. As the dihydric alcohol, for example, diols or bisphenols can be used. As the carboxylic acid for synthesizing the polyester resin, for example, the following divalent carboxylic acids or trivalent or higher carboxylic acids can be suitably used. When at least one of alcohol and carboxylic acid has an aromatic ring in the molecule, the synthesized polyester resin tends to exhibit crystallinity. On the other hand, when neither alcohol nor carboxylic acid has an aromatic ring in the molecule, the synthesized polyester resin tends to exhibit non-crystalline properties. Moreover, if the crystallinity of the synthesized polyester resin is low, the softening point of the polyester resin tends to be low.

  Preferable examples of diols include ethylene glycol, diethylene glycol, triethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, neopentyl glycol, 2-butene-1,4. -Diol, 1,5-pentanediol, 1,6-hexanediol, 1,4-cyclohexanedimethanol, dipropylene glycol, polyethylene glycol, polypropylene glycol, or polytetramethylene glycol.

  Preferable examples of the bisphenol include bisphenol A, hydrogenated bisphenol A, bisphenol A ethylene oxide adduct, or bisphenol A propylene oxide adduct.

  Preferable examples of trihydric or higher alcohols include sorbitol, 1,2,3,6-hexanetetrol, 1,4-sorbitan, pentaerythritol, dipentaerythritol, tripentaerythritol, 1,2,4-butane. Triol, 1,2,5-pentanetriol, glycerol, diglycerol, 2-methylpropanetriol, 2-methyl-1,2,4-butanetriol, trimethylolethane, trimethylolpropane, or 1,3,5- Trihydroxymethylbenzene is mentioned.

  As preferable examples of the divalent carboxylic acid, maleic acid, fumaric acid, citraconic acid, itaconic acid, glutaconic acid, phthalic acid, isophthalic acid, terephthalic acid, cyclohexanedicarboxylic acid, adipic acid, sebacic acid, azelaic acid, malonic acid Succinic acid, alkyl succinic acid (more specifically, n-butyl succinic acid, isobutyl succinic acid, n-octyl succinic acid, n-dodecyl succinic acid, isododecyl succinic acid, etc.), or alkenyl succinic acid (more specific Specifically, n-butenyl succinic acid, isobutenyl succinic acid, n-octenyl succinic acid, n-dodecenyl succinic acid, or isododecenyl succinic acid, etc.) may be mentioned.

  Preferred examples of the trivalent or higher carboxylic acid include 1,2,4-benzenetricarboxylic acid (trimellitic acid), 2,5,7-naphthalenetricarboxylic acid, 1,2,4-naphthalenetricarboxylic acid, 2,4-butanetricarboxylic acid, 1,2,5-hexanetricarboxylic acid, 1,3-dicarboxyl-2-methyl-2-methylenecarboxypropane, 1,2,4-cyclohexanetricarboxylic acid, tetra (methylenecarboxyl) Examples include methane, 1,2,7,8-octanetetracarboxylic acid, pyromellitic acid, or empole trimer acid.

  When the toner core contains an amorphous polyester resin, the number average molecular weight (Mn) of the amorphous polyester resin is preferably 1000 or more and 2000 or less. This improves the strength of the toner core and the toner fixability. The molecular weight distribution of the amorphous polyester resin is preferably 9 or more and 21 or less. Here, the molecular weight distribution of the amorphous polyester resin means the ratio (Mw / Mn) of the mass average molecular weight (Mw) to the number average molecular weight (Mn).

  When the toner core contains a crystalline polyester resin in addition to the amorphous polyester resin, the toner core preferably contains a crystalline polyester resin having a crystallinity index of 0.98 to 1.20. Thereby, hydrolysis of the polyester resin contained in the toner core is further accelerated. Therefore, the formation of the base recess is further promoted. Here, the crystallinity index corresponds to the ratio of the softening point (Tm) to the melting point (Mp) (= Tm / Mp). The crystallinity index of the polyester resin can be adjusted by changing the type or amount of the material for synthesizing the polyester resin. For example, the crystallinity index of the polyester resin can be adjusted by changing the type or amount of at least one of alcohol and carboxylic acid. In addition, about non-crystalline polyester resin, clear Mp cannot be measured in many cases.

(Binder resin: Thermoplastic resin)
The toner core may further contain the following thermoplastic resin in addition to the polyester resin.

  As the thermoplastic resin, for example, a styrene resin, an acrylic acid resin, an olefin resin, a vinyl resin, a polyamide resin, or a urethane resin can be suitably used. A copolymer of these resins, that is, a copolymer in which an arbitrary repeating unit is introduced into the resin, can also be suitably used as the thermoplastic resin constituting the toner particles. For example, a styrene-acrylic acid resin or styrene-butadiene resin can also be suitably used as the thermoplastic resin constituting the toner core.

  As the acrylic resin, for example, an acrylic ester polymer or a methacrylic ester polymer can be used. As the olefin resin, for example, a polyethylene resin or a polypropylene resin can be used. As the vinyl resin, for example, vinyl chloride resin, polyvinyl alcohol, vinyl ether resin, or N-vinyl resin can be used.

  The styrene-acrylic acid resin is a copolymer of one or more styrene monomers and one or more acrylic monomers. In order to synthesize a styrene-acrylic acid resin, for example, the following styrene monomer and acrylic acid monomer can be suitably used. By using an acrylic acid monomer, a carboxyl group can be introduced into the styrene-acrylic acid resin. Moreover, a hydroxyl group can be introduce | transduced into a styrene-acrylic acid-type resin by using the monomer which has a hydroxyl group. As the monomer having a hydroxyl group, for example, p-hydroxystyrene, m-hydroxystyrene, or (meth) acrylic acid hydroxyalkyl ester can be used.

  Preferable examples of the styrenic monomer include styrene, alkyl styrene, p-hydroxystyrene, m-hydroxystyrene, vinyl toluene, α-chlorostyrene, o-chlorostyrene, m-chlorostyrene, or p-chlorostyrene. It is done. Examples of the alkyl styrene include α-methyl styrene, p-ethyl styrene, and 4-tert-butyl styrene.

  Preferable examples of the acrylic acid monomer include (meth) acrylic acid, (meth) acrylic acid alkyl ester, or (meth) acrylic acid hydroxyalkyl ester. Suitable examples of the (meth) acrylic acid alkyl ester include methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, iso-propyl (meth) acrylate, and (meth) acrylic. Examples include n-butyl acid, iso-butyl (meth) acrylate, or 2-ethylhexyl (meth) acrylate. Suitable examples of the (meth) acrylic acid hydroxyalkyl ester include 2-hydroxyethyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, or (meth) acrylic. The acid 4-hydroxybutyl is mentioned.

(Toner core: Colorant)
As the colorant, a known pigment or dye can be used according to the color of the toner. In order to form a high-quality image using toner, the amount of the colorant is preferably 1 part by mass or more and 20 parts by mass or less with respect to 100 parts by mass of the binder resin.

  The toner core may contain a black colorant. An example of a black colorant is carbon black. The black colorant may be a colorant that is toned to black using a yellow colorant, a magenta colorant, and a cyan colorant.

  The toner core may contain a color colorant such as a yellow colorant, a magenta colorant, or a cyan colorant.

  As the yellow colorant, for example, one or more compounds selected from the group consisting of condensed azo compounds, isoindolinone compounds, anthraquinone compounds, azo metal complexes, methine compounds, and arylamide compounds can be used. Examples of the yellow colorant include C.I. I. Pigment Yellow (3, 12, 13, 14, 15, 17, 62, 74, 83, 93, 94, 95, 97, 109, 110, 111, 120, 127, 128, 129, 147, 151, 154, 155 168, 174, 175, 176, 180, 181, 191, or 194), naphthol yellow S, Hansa yellow G, or C.I. I. Vat yellow can be preferably used.

  The magenta colorant is, for example, selected from the group consisting of condensed azo compounds, diketopyrrolopyrrole compounds, anthraquinone compounds, quinacridone compounds, basic dye lake compounds, naphthol compounds, benzimidazolone compounds, thioindigo compounds, and perylene compounds. One or more compounds can be used. Examples of the magenta colorant include C.I. I. Pigment Red (2, 3, 5, 6, 7, 19, 23, 48: 2, 48: 3, 48: 4, 57: 1, 81: 1, 122, 144, 146, 150, 166, 169, 177 184, 185, 202, 206, 220, 221 or 254) can be preferably used.

  As the cyan colorant, for example, one or more compounds selected from the group consisting of a copper phthalocyanine compound, an anthraquinone compound, and a basic dye lake compound can be used. Examples of cyan colorants include C.I. I. Pigment blue (1, 7, 15, 15: 1, 15: 2, 15: 3, 15: 4, 60, 62, or 66), phthalocyanine blue, C.I. I. Bat Blue, or C.I. I. Acid blue can be preferably used.

(Toner core: Release agent)
The release agent is used, for example, for the purpose of improving the fixing property or offset resistance of the toner. In order to increase the anionicity of the toner core, it is preferable to produce the toner core using an anionic wax. In order to improve the fixing property or offset resistance of the toner, the amount of the release agent is preferably 1 part by mass or more and 30 parts by mass or less with respect to 100 parts by mass of the binder resin.

  Examples of the release agent include low molecular weight polyethylene, low molecular weight polypropylene, polyolefin copolymer, polyolefin wax, microcrystalline wax, paraffin wax, or aliphatic hydrocarbon wax such as Fischer-Tropsch wax; oxidized polyethylene wax or a block thereof Oxides of aliphatic hydrocarbon waxes such as copolymers; plant waxes such as candelilla wax, carnauba wax, wood wax, jojoba wax, or rice wax; animal properties such as beeswax, lanolin, or whale wax Waxes; mineral waxes such as ozokerite, ceresin, or petrolatum; waxes based on fatty acid esters such as montanate ester wax or castor wax; fats such as deoxidized carnauba wax The wax portion of the ester or the whole was deoxygenated can be suitably used. One type of release agent may be used alone, or multiple types of release agents may be used in combination.

  In order to improve the compatibility between the binder resin and the release agent, a compatibilizer may be added to the toner core.

(Toner core: charge control agent)
The charge control agent is used, for example, for the purpose of improving the charge stability or charge rising property of the toner. The charge rising characteristic of the toner is an index as to whether or not the toner can be charged to a predetermined charge level in a short time.

  By adding a negatively chargeable charge control agent to the toner core, the anionicity of the toner core can be enhanced. Further, the cationic property of the toner core can be increased by including a positively chargeable charge control agent in the toner core. However, if sufficient chargeability is ensured in the toner, it is not necessary to include a charge control agent in the toner core.

(Toner core: magnetic powder)
As the material of the magnetic powder, for example, a ferromagnetic metal or an alloy thereof, a ferromagnetic metal oxide, or a material subjected to ferromagnetization treatment can be preferably used. For example, iron, cobalt, or nickel can be used as the ferromagnetic metal. As the ferromagnetic metal oxide, for example, ferrite, magnetite, or chromium dioxide can be used. Examples of the ferromagnetization treatment include heat treatment. One type of magnetic powder may be used alone, or a plurality of types of magnetic powder may be used in combination.

  In order to suppress elution of metal ions (for example, iron ions) from the magnetic powder, it is preferable to surface-treat the magnetic powder. When a shell layer is formed on the surface of the toner core under acidic conditions, if the metal ions are eluted on the surface of the toner core, the toner cores are easily fixed to each other. It is considered that fixing of the toner cores can be suppressed by suppressing elution of metal ions from the magnetic powder.

(Shell layer)
The shell layer may be a film without graininess or a film with graininess. When resin particles are used as a material for forming the shell layer, it is considered that if the resin particles are completely melted and cured in a film-like form, a film having no graininess is formed as the shell layer. On the other hand, if the resin particles are not completely melted and are cured in a film-like form, it is considered that a film having a form in which the resin particles are two-dimensionally connected (a film having a granular feeling) is formed as a shell layer. .

(Shell layer: Thermoplastic resin)
The shell layer preferably contains at least one of the polyester resin described in the above (binder resin: polyester resin) and the thermoplastic resin described in the above (binder resin: thermoplastic resin).

  The shell layer may further contain a thermosetting resin. As the thermosetting resin contained in the shell layer, for example, the following thermosetting resins can be used.

  Preferable examples of the thermosetting resin include amino aldehyde resin, polyimide resin, and xylene resin. An aminoaldehyde resin is a resin produced by condensation polymerization of a compound having an amino group and an aldehyde. Here, as the aldehyde, for example, formaldehyde can be used. Examples of aminoaldehyde resins include melamine resins, urea resins, sulfonamide resins, glyoxal resins, guanamine resins, or aniline resins. As the polyimide resin, for example, a maleimide polymer or a bismaleimide polymer can be used.

  In order to improve the film quality of the shell layer, the resin contained in the shell layer is derived from 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 2-hydroxyethyl methacrylate, or 2-hydroxypropyl methacrylate. One or more alcoholic hydroxyl groups may be introduced.

  In order to improve the charging stability of the toner, the shell layer particularly preferably contains a copolymer of one or more styrene monomers and one or more acrylic monomers. As the styrene monomer, for example, styrene can be used. As the acrylic monomer, for example, an acrylic ester can be used.

  The charge stability of the toner may be improved by incorporating a charge control agent in the shell layer. In order to contain the charge control agent in the shell layer, a repeating unit derived from the charge control agent (for example, quaternary ammonium salt) may be incorporated in the resin constituting the shell layer, or in the resin constituting the shell layer. You may disperse the charged particles. In order to positively charge the toner particles, the shell layer preferably includes resin particles having positive chargeability.

(External additive)
The external additive is used, for example, to improve the fluidity of toner particles or the handling of toner. For example, the amount of the external additive is preferably 0.5 parts by mass or more and 10 parts by mass or less with respect to 100 parts by mass of the toner base particles. The particle size of the external additive is preferably 0.01 μm or more and 1.0 μm or less.

  As the external additive, silica particles or metal oxide particles can be preferably used. The metal oxide is preferably alumina, titanium oxide, magnesium oxide, zinc oxide, strontium titanate, or barium titanate, for example. One type of external additive may be used alone, or a plurality of types of external additives may be used in combination.

[Exemplary Use of Toner According to this Embodiment]
The toner according to the exemplary embodiment can be suitably used for developing an electrostatic latent image, for example, as a positively chargeable toner. The toner of this embodiment may be used as a one-component developer or may be used as a toner contained in a two-component developer.

(Example of use of toner according to this embodiment: two-component developer)
When the toner of this embodiment is used as a toner contained in a two-component developer, the two-component developer can be prepared by mixing the toner and the carrier using a mixing device. As the mixing device, for example, a ball mill can be used.

  It is preferable to use a ferrite carrier as the carrier. Thereby, a high quality image can be formed. As the carrier, it is more preferable to use magnetic carrier particles including a carrier core and a resin layer covering the carrier core. Thereby, a high-quality image can be formed over a long period of time. In order to impart magnetism to the carrier particles, the carrier particles may be formed of a magnetic material, or the carrier particles may be formed of a resin in which the magnetic particles are dispersed. Further, magnetic particles may be dispersed in the resin layer covering the carrier core. In order to form a high-quality image, the amount of toner in the two-component developer is preferably 5 parts by mass or more and 15 parts by mass or less with respect to 100 parts by mass of the carrier. The positively chargeable toner contained in the two-component developer is positively charged by friction with the carrier.

  In Examples, toners T-1 to T-11 were manufactured, and the manufactured toners T-1 to T-11 were evaluated. Table 1 shows the physical properties of the inorganic particles contained in the toner particles of the toners T-1 to T-11. The powder composed of a plurality of inorganic particles contained inorganic particles having a particle diameter (equivalent circle diameter) of “particle diameter” ± 1 nm shown in Table 1 at a ratio of 85% by number or more. Table 2 shows the manufacturing conditions of each of the toners T-1 to T-11, specifically, the temperature rising conditions when forming the shell layer. In Table 1, “particle diameter” means the number average primary particle diameter of inorganic particles. The “content” means the content of inorganic particles with respect to 100 parts by mass of the toner core. In Table 2, “−” at the target pH of the toner T-11 means that the pH of the flask contents was not changed in the temperature raising step when forming the shell layer.

  Below, the manufacturing method of toner T-1 to T-11 is demonstrated first. Next, a method for measuring the physical property values of the toner particles contained in each of the toners T-1 to T-11 will be described. Next, an evaluation method and evaluation results of toners T-1 to T-11 will be described. In the evaluation in which an error occurs, a considerable number of measurement values with sufficiently small errors are obtained, and the arithmetic average of the obtained measurement values is used as the evaluation value. The number average particle diameter of the powder is the number average value of the equivalent-circle diameters of the primary particles measured using a transmission electron microscope (TEM) unless otherwise specified. Further, Tg (glass transition point) and Tm (softening point) were measured by the following methods.

<Measurement method of Tg>
Using a differential scanning calorimeter (“DSC-6220” manufactured by Seiko Instruments Inc.), the endothermic curve (vertical axis: heat flow (DSC signal), horizontal axis: temperature) of the sample (for example, resin) was determined. Subsequently, the Tg (glass transition point) of the sample was read from the obtained endothermic curve. The temperature of the specific heat change point (intersection of the extrapolation line of the base line and the extrapolation line of the falling line) in the obtained endothermic curve corresponds to the Tg (glass transition point) of the sample.

<Tm measurement method>
A sample (for example, resin) is set on a Koka type flow tester (“CFT-500D” manufactured by Shimadzu Corporation), a die pore diameter of 1 mm, a plunger load of 20 kg / cm ² , and a temperature rising rate of 6 ° C./min. Then, a 1 cm ³ sample was melted and discharged, and an S-shaped curve (horizontal axis: temperature, vertical axis: stroke) of the sample was obtained. Subsequently, the Tm (softening point) of the sample was read from the obtained S-shaped curve. In the obtained S-curve, if the maximum stroke value is S ₁ and the low-temperature baseline stroke value is S ₂ , the stroke value in the S-curve is “(S ₁ + S ₂ ) / 2”. Corresponds to the Tm (softening point) of the sample.

[Production of Toner T-1]
(Production of toner core)
92.5 parts by mass of low-viscosity amorphous polyester resin (Tg = 38 ° C., Tm = 65 ° C.) and 7.5 parts by mass of aluminum nitride particles (“1360HK” manufactured by SkySpring Nanomaterials, Inc.) Mixing was performed at a rotational speed of 2400 rpm using a mixer (manufactured by Nippon Coke Industries, Ltd.). The mixture thus obtained was subjected to a material supply speed of 5 kg / hour, a shaft rotation speed of 160 rpm, and a set temperature range (cylinder temperature range) using a twin-screw extruder (“PCM-30” manufactured by Ikegai Co., Ltd.). It was melt-kneaded under conditions of 40 ° C. or higher and 80 ° C. or lower. The obtained melt-kneaded product was cooled, and the cooled melt-kneaded product was coarsely pulverized using a pulverizer (“Rotoplex 16/8” manufactured by Toa Machinery Co., Ltd.). In this way, a coarsely pulverized product containing aluminum nitride particles was obtained.

66 parts by mass of coarsely pulverized product (coarse pulverized product containing aluminum nitride particles), 9 parts by mass of medium-viscosity amorphous polyester resin (Tg = 53 ° C., Tm = 84 ° C.), and 12 parts by mass of high viscosity non- Crystalline polyester resin (Tg = 71 ° C., Tm = 120 ° C.), 5 parts by mass of carnauba wax (“Carnauba Wax No. 1” manufactured by Hiroyuki Kato Co., Ltd.), and 8 parts by mass of colorant (manufactured by DIC Corporation) “KET BLUE 111” and phthalocyanine blue) were mixed at a rotational speed of 2400 rpm using an FM mixer (manufactured by Nippon Coke Industries, Ltd.). Using the twin screw extruder ("PCM-30" manufactured by Ikegai Co., Ltd.), the resulting mixture was fed at a material supply rate of 5 kg / hour, a shaft rotation speed of 160 rpm, and a set temperature range (cylinder temperature range) of 80 ° C to 130 ° C. Melt kneading was performed under the following conditions. Subsequently, the obtained melt-kneaded product was cooled, and the cooled melt-kneaded product was coarsely pulverized using a pulverizer (former “Rotoplex 16/8” manufactured by Toa Machinery Co., Ltd.). Subsequently, the obtained coarsely pulverized product was finely pulverized using a jet mill (“Ultrasonic Jet Mill Type I” manufactured by Nippon Pneumatic Industry Co., Ltd.). Subsequently, the obtained finely pulverized product was classified using a classifier (“Elbow Jet EJ-LABO type” manufactured by Nippon Steel Mining Co., Ltd.). As a result, a toner core having a volume median diameter (D ₅₀ ) of 6 μm was obtained. The obtained toner core contained 5 parts by mass of aluminum nitride particles with respect to 100 parts by mass of the toner core.

(Preparation of shell material)
A 1 L three-necked flask equipped with a thermometer and a stirring blade was set in a water bath. Subsequently, 875 g of ion-exchanged water (temperature: 30 ° C.) and 75 g of an anionic surfactant (“Latemul (registered trademark) WX” manufactured by Kao Corporation), components: sodium polyoxyethylene alkyl ether sulfate, Solid content concentration: 26% by mass). Thereafter, the temperature in the flask was raised to 80 ° C. using a water bath while stirring the flask contents. Subsequently, while stirring the contents of the flask at 80 ° C., two kinds of liquids (first liquid and second liquid) were dropped into the flask over 5 hours each. The first liquid was a mixture of 17 g styrene and 3 g butyl acrylate. The second liquid was a solution in which 0.5 g of potassium persulfate was dissolved in 30 g of ion exchange water.

  Subsequently, while maintaining the temperature in the flask at 80 ° C., the flask contents were further stirred for 2 hours to sufficiently proceed the polymerization reaction of the flask contents. As a result, a suspension (solid content concentration: 3.6% by mass) containing particles made of a hydrophobic thermoplastic resin was obtained. Regarding the resin particles contained in the obtained suspension, the number average particle diameter was 32 nm and Tg was 71 ° C.

(Formation of shell layer)
A 1 L three-necked flask equipped with a thermometer and a stirring blade was set in a water bath, and 300 g of ion-exchanged water was placed in the flask. Thereafter, the temperature in the flask was kept at 30 ° C. using a water bath. Subsequently, dilute hydrochloric acid was added to the flask to adjust the pH of the flask contents to 4. Subsequently, 30 g of shell material (a suspension of hydrophobic thermoplastic resin particles prepared by the above-described procedure) was added to the flask to obtain a dispersion of shell material.

(Shell layer formation: temperature rise)
Subsequently, 300 g of a toner core (toner core produced by the above-described procedure) was added to the obtained dispersion of shell material, and the flask contents were stirred at a rotational speed of 200 rpm for 1 hour. Thereafter, 300 g of ion-exchanged water was further added into the flask. Subsequently, the flask contents were heated while stirring the flask contents at a rotation speed of 100 rpm. At the start of heating, the temperature of the flask contents (described as initial temperature in Table 2) was 30 ° C., and the pH of the flask contents (described as initial pH in Table 2) was 4. Regarding the temperature raising conditions, the target temperature was 70 ° C. and the temperature raising rate was 1.0 ° C./min.

  During the temperature increase, when the temperature of the flask contents reached 35 ° C., an aqueous sodium hydroxide solution was added to the flask to change the pH of the flask contents to 9. That is, the pH change temperature was set to 35 ° C. when the toner T-1 was manufactured. The temperature increase was continued to the target temperature (70 ° C.) without stopping the temperature increase during and after the pH change.

  When the temperature of the flask contents reaches 70 ° C. due to the above temperature rise, the temperature of the flask contents is maintained at that temperature (70 ° C.), and the flask contents are further stirred for 1 hour at a temperature of 70 ° C. and a rotation speed of 100 rpm. did. Then, cold water was put in the flask, and the flask contents were rapidly cooled to room temperature (about 25 ° C.). As a result, a dispersion containing toner mother particles was obtained.

(Washing)
The dispersion of toner base particles obtained as described above was filtered (solid-liquid separation) using a Buchner funnel. As a result, toner base particles in the form of wet cake were obtained. Thereafter, the obtained wet cake-like toner base particles were redispersed in ion-exchanged water. Further, dispersion and filtration were repeated 5 times to wash the toner base particles.

(Dry)
Subsequently, the obtained toner base particles were dispersed in an aqueous ethanol solution having a concentration of 50% by mass. As a result, a slurry of toner base particles was obtained. Subsequently, the toner base particles in the slurry were removed under the conditions of a hot air temperature of 45 ° C. and a blower air volume of 2 m ³ / min using a continuous surface reformer (“Coat Mizer (registered trademark)” manufactured by Freund Sangyo Co., Ltd.). Dried. As a result, dried toner base particles (powder) were obtained.

(External)
100 parts by weight of toner base particles (toner base particles obtained as described above) and 1.8 parts by weight of hydrophobic silica particles (“AEROSIL® RA-200H” manufactured by Nippon Aerosil Co., Ltd., contents: Dry silica particles surface-modified with trimethylsilyl group and amino group, BET specific surface area: about 150 m ² / g, number average primary particle size: about 12 nm), and a 10 L capacity FM mixer (manufactured by Nippon Coke Industries, Ltd.) For 5 minutes. As a result, the external additive (silica particles) was adhered to the surface of the toner base particles. Thereafter, the obtained toner was sieved using a sieve of 200 mesh (aperture 75 μm). As a result, a toner (toner T-1) containing a large number of toner particles was obtained. In the toner particles contained in the toner T-1, a shell layer having a thickness of 20 nm was formed on the surface region of the toner core.

[Production of Toner T-2]
Except for the following points, Toner T-2 was manufactured according to the manufacturing method of Toner T-1. Specifically, in the above (preparation of toner core), 92.5 parts by mass of low-viscosity amorphous polyester resin (Tg = 38 ° C., Tm = 65 ° C.) and 7.5 parts by mass of aluminum nitride particles (SkySpring Nanomaterials, Inc.) Instead of mixing “1360HK”), 85 parts by mass of low-viscosity amorphous polyester resin (Tg = 38 ° C., Tm = 65 ° C.) and 15 parts by mass of aluminum nitride particles (manufactured by SkySpring Nanomaterials, Inc.) “1360HK”). Therefore, the obtained toner core contained 10 parts by mass of aluminum nitride particles with respect to 100 parts by mass of the toner core. Further, in the toner particles contained in the toner T-2, a shell layer having a thickness of 20 nm was formed on the surface region of the toner core.

[Production of Toner T-3]
Except for the following points, Toner T-3 was manufactured according to the manufacturing method of Toner T-1. Specifically, in the above (preparation of toner core), 92.5 parts by mass of low-viscosity amorphous polyester resin (Tg = 38 ° C., Tm = 65 ° C.) and 7.5 parts by mass of aluminum nitride particles (SkySpring Nanomaterials, Inc.) Instead of “1360HK”), 99.25 parts by weight of low-viscosity amorphous polyester resin (Tg = 38 ° C., Tm = 65 ° C.) and 0.75 parts by weight of aluminum nitride particles (SkySpring Nanomaterials) , Inc. "1360HK"). Therefore, the obtained toner core contained 0.5 parts by mass of aluminum nitride particles with respect to 100 parts by mass of the toner core. Further, in the toner particles contained in the toner T-3, a shell layer having a thickness of 20 nm was formed on the surface region of the toner core.

[Production of Toner T-4]
According to the production method of toner T-1, except that boron nitride particles (“1522DX” manufactured by SkySpring Nanomaterials, Inc.) are used instead of aluminum nitride particles (“1360HK” manufactured by SkySpring Nanomaterials, Inc.), toner T -4 was produced. In the toner particles contained in the toner T-4, a shell layer having a thickness of 20 nm was formed on the surface region of the toner core.

[Production of Toner T-5]
According to the production method of toner T-1, except that aluminum oxide particles (“1319NH” manufactured by SkySpring Nanomaterials, Inc.) are used instead of aluminum nitride particles (“1360HK” manufactured by SkySpring Nanomaterials, Inc.), toner T -5 was produced. In the toner particles contained in the toner T-5, a shell layer having a thickness of 20 nm was formed in the surface region of the toner core.

[Production of Toner T-6]
Except for the following points, Toner T-6 was manufactured according to the manufacturing method of Toner T-1. Specifically, in the above (formation of shell layer: temperature increase), the target temperature for temperature increase was 65 ° C., and the temperature increase rate was 0.5 ° C./min. Further, when the temperature of the flask contents reached 35 ° C., an aqueous sodium hydroxide solution was added to the flask to change the pH of the flask contents to 11. In the toner particles contained in the manufactured toner T-6, a shell layer having a thickness of 20 nm was formed on the surface region of the toner core.

[Production of Toner T-7]
According to the production method of toner T-1, except that silicon carbide particles (“6820HK” manufactured by SkySpring Nanomaterials, Inc.) are used instead of aluminum nitride particles (“1360HK” manufactured by SkySpring Nanomaterials, Inc.), toner T -7 was produced. In the toner particles contained in the toner T-7, a shell layer having a thickness of 20 nm was formed on the surface region of the toner core.

[Production of Toner T-8]
Toner T-8 was manufactured according to the manufacturing method of Toner T-1, except that the toner core was prepared without adding aluminum nitride particles. In the toner particles contained in the toner T-8, a shell layer having a thickness of 20 nm was formed on the surface region of the toner core.

[Production of Toner T-9]
The toner T- 9 was produced. In the toner particles contained in the toner T-9, a shell layer having a thickness of 20 nm was formed on the surface region of the toner core.

[Production of Toner T-10]
According to the production method of toner T-1, except that aluminum nitride particles (“593044” manufactured by Sigma Aldrich, Inc.) are used instead of aluminum nitride particles (“1360HK” manufactured by SkySpring Nanomaterials, Inc.), toner T -10 was produced. In the toner particles contained in the toner T-10, a shell layer having a thickness of 20 nm was formed in the surface region of the toner core.

[Production of Toner T-11]
Toner T-11 was produced according to the production method of toner T-1, except that the aqueous sodium hydroxide solution was not added to the flask in the above (formation of shell layer: temperature increase). In the toner particles contained in the toner T-11, a shell layer having a thickness of 20 nm was formed on the surface region of the toner core.

[Method for measuring physical properties of toner particles]
(Measurement of the number of surface recesses per unit area of the toner particle surface area)
Regarding the toners T-1 to T-11 obtained as described above, the number of surface recesses per unit area of the surface area of the toner particles was measured. The measurement target was toner base particles contained in each of toners T-1 to T-11. That is, the number of surface recesses per unit area of the surface area of the toner particles was determined before the external addition process was performed on the toner base particles. Specifically, the entire surface of the toner base particles was observed using a field emission scanning electron microscope (FE-SEM) (“JSM-7600F” manufactured by JEOL Ltd.). 20 toner base particles were observed for each sample. And the number (number average value) of the surface recessed part per unit area of the surface area | region of a toner particle was calculated | required. The results are shown in Table 3.

(Evaluation of the position of inorganic particles)
With respect to the toners T-1 to T-11 obtained as described above, it was examined whether or not inorganic particles were present in the inner region of the base recess in the interface between the toner core and the shell layer. The measurement target was toner base particles contained in each of toners T-1 to T-11. Specifically, the entire surface of the toner base particles was observed using a field emission scanning electron microscope (FE-SEM) (“JSM-7600F” manufactured by JEOL Ltd.). And it was investigated whether the inorganic particle exists in a predetermined location. The results are shown in Table 3.

The present inventors have confirmed that in toners T-1 to T-7, each toner particle contains at least one of the following inorganic particles IP-1 to IP-3.
The inorganic particles IP-1 were present in the toner core and were in contact with the interface between the toner core and the shell layer.
The inorganic particles IP-2 were present in the shell layer. Specifically, the inorganic particles IP-2 may be in contact with the interface between the toner core and the shell layer, or may be present on the outer side in the radial direction of the toner particles with respect to the interface between the toner core and the shell layer. . Furthermore, in the inorganic particles IP-2, a portion located outside the toner particles in the radial direction may be exposed from the shell layer.
In the inorganic particle IP-3, a portion located inside the toner particle in the radial direction exists in the toner core, and a portion located outside the toner particle in the radial direction exists in the shell layer.

(Measurement of shell layer thickness)
Regarding the toners T-1 to T-11 obtained as described above, the thickness of the shell layer was measured. The measurement target was toner base particles contained in each of toners T-1 to T-11. Specifically, first, a cross-sectional TEM photograph of the toner base particles was taken using a transmission electron microscope (TEM, “H-7100FA” manufactured by Hitachi High-Technologies Corporation). Next, a cross-sectional TEM photograph of the obtained toner base particles was analyzed using image analysis software (“WinROOF” manufactured by Mitani Corporation). Specifically, two straight lines perpendicular to the approximate center of the cross section of the toner base particles were drawn. In each of the two straight lines, the length from the interface between the toner core and the shell layer (corresponding to the surface of the toner core) to the surface of the shell layer was measured. The average value of the four lengths thus measured was taken as the thickness of the shell layer provided in one toner base particle. The thickness of the shell layer was measured for a plurality of toner base particles, and the average value of the thicknesses of the shell layers included in the plurality of toner base particles (measurement target) was obtained. The average value of the thickness of the shell layer thus obtained was defined as “shell layer thickness”.

  When the boundary between the toner core and the shell layer is unclear in the cross-sectional TEM photograph of the toner base particles, the cross-sectional TEM photograph of the toner base particles is converted into an electron energy loss spectroscopy (EELS) detector (“GIF TRIDIEM” manufactured by Gatan). (Registered trademark) ”) and image analysis software (“ WinROOF ”manufactured by Mitani Corporation). Thereby, the boundary between the toner core and the shell layer became clear in the cross-sectional TEM photograph of the toner base particles.

[Toner Evaluation Method]
(Measurement of minimum fixing temperature)
The minimum fixing temperature means the lowest temperature among the fixing temperatures when it is determined that a low temperature offset has not occurred. If the minimum fixing temperature is 130 ° C. or lower, it can be said that the occurrence of low temperature offset is prevented and the toner has excellent low temperature fixing properties.

  In this evaluation, a modified printer (“FS-C5250DN” manufactured by Kyocera Document Solutions Co., Ltd.) was used as an evaluation machine. The evaluation machine used was able to adjust the amount of toner on the recording paper and the temperature at which the toner placed on the recording paper was fixed to the recording paper (hereinafter referred to as the fixing temperature).

  As a measurement object, a two-component developer containing each of the toners T-1 to T-11 obtained as described above was used. As the two-component developer, one prepared according to the following method was used. Each of the toners T-1 to T-11 obtained as described above and a ferrite carrier (“F-150” manufactured by Powdertech) were mixed so that the toner concentration was 10% by mass.

(Minimum fixing temperature measurement: preliminary test)
In the measurement of the minimum fixing temperature, a preliminary test was performed and then an evaluation test was performed. In the preliminary test, a temperature range including the minimum fixing temperature was specified. Specifically, first, a two-component developer was set in the developing device of the evaluation machine. The bias of the evaluator was adjusted so that the amount of toner loaded on the recording paper was 0.4 mg / cm ² . While conveying printing paper (90 g / m ² printing paper) at a linear speed of 200 mm / sec, an unfixed solid image was formed on the printing paper.

  The printing paper on which an unfixed solid image was formed was passed through the fixing device of the evaluation machine. At this time, the temperature of the fixing device of the evaluation machine (specifically, the temperature of the fixing roller included in the fixing device of the evaluation machine) is increased from 90 ° C. by 5 ° C., whereby the fixing temperature is 90 ° C. or more and 200 ° C. or less. The temperature was raised by 5 ° C. over the temperature range of In this way, solid images (23 types) fixed at each fixing temperature were obtained.

  Each of the obtained solid images was subjected to a rubbing test to determine whether or not a low temperature offset occurred. Specifically, the recording paper on which the solid image was fixed was folded in half so that the surface on which the solid image was fixed was inside. Using a 1 kg weight coated with a fabric, the recording sheet was rubbed 5 times on the fold. Thereafter, the recording paper was expanded, and the length of toner peeling (hereinafter referred to as peeling width) in the portion where the solid image was fixed in the bent portion of the recording paper was measured. When the peeling width was less than 1.0 mm, it was determined that the low temperature offset did not occur, and when the peeling width was 1.0 mm or more, it was determined that the low temperature offset occurred. The minimum fixing temperature is within the range from the highest fixing temperature when it is determined that a low temperature offset has occurred to the lowest fixing temperature when it is determined that a low temperature offset has not occurred. It was judged that it exists.

(Minimum fixing temperature measurement: evaluation test)
In the evaluation test, the fixing temperature when the low temperature offset occurred was specified. Specifically, by increasing the temperature of the fixing device of the evaluation machine by 1 ° C., the low temperature offset did not occur from the highest fixing temperature when it was determined that the low temperature offset occurred. When it was judged, the fixing temperature was changed to the lowest temperature. In this way, solid images (6 types) fixed at each fixing temperature were obtained. By performing the above-described rubbing test using each of the obtained solid images, it was determined whether or not a low temperature offset occurred. In this way, the minimum fixing temperature was determined.
The results are shown in Table 3. A minimum fixing temperature of 130 ° C. or lower was evaluated as good.

(Measurement of variation in saturation)
As an evaluation machine, a printer (“FS-C5250DN” manufactured by Kyocera Document Solutions Inc.) was used. In the evaluation machine used, the bias was adjusted so that the toner loading amount on the recording paper was 0.4 mg / cm ² .

  As a measurement object, a two-component developer containing each of the toners T-1 to T-11 obtained as described above was used. As the two-component developer, one prepared according to the following method was used. Each of the toners T-1 to T-11 obtained as described above and a ferrite carrier (“F-150” manufactured by Powdertech) were mixed so that the toner concentration was 10% by mass.

First, the two-component developer was set in the developing device of the evaluation machine. Then, an unfixed solid image was formed on the printing paper while conveying the printing paper (90 g / m ² printing paper) at a linear speed of 200 mm / sec. The printing paper on which the unfixed solid image was formed was passed through the fixing device of the evaluation machine, and the unfixed solid image was fixed on the printing paper at a fixing temperature of 140 ° C. In this way, a solid image fixed at 140 ° C. was obtained.

About the obtained solid image, saturation was measured using the reflection densitometer ("SpectroEye (trademark)" by X-Rite). Specifically, the saturation was measured at any 10 locations in the obtained solid image. Then, among the measured saturations, the minimum saturation and the maximum saturation were substituted into the following formula to calculate a variation value of the saturation.
Variation value of saturation = 100 × minimum saturation / maximum saturation

  The results are shown in Table 3. If the variation value of saturation was 95% or more, it was evaluated as good. Specifically, if the variation value of saturation is 95% or more, the toner is considered to be excellent in charging stability. The reason is as follows. When the toner has excellent charge stability, the charge amount of the toner is maintained within an appropriate range even during image formation. Therefore, if an image is formed using a toner having excellent charging stability, it is possible to prevent the toner from remaining on the surface of the constituent member of the image forming apparatus even after the image is formed. Thus, an image having the designed toner amount is formed on the printing paper. Therefore, the variation value of saturation increases. For example, the saturation variation value is 95% or more.

(Evaluation of heat-resistant storage stability)
With respect to the toners T-1 to T-11 obtained as described above, the heat resistant storage stability was evaluated. Specifically, 2 g of toner was put in a 20 mL polyethylene container and sealed, and the sealed container was allowed to stand in a thermostat set at 60 ° C. for 3 hours. Thereafter, the toner taken out from the thermostat was cooled to room temperature (about 25 ° C.) to obtain an evaluation toner.

Subsequently, the obtained toner for evaluation was placed on a sieve having a known mass of 100 mesh (aperture 150 μm). Then, the mass of the sieve containing the evaluation toner was measured, and the mass of the toner before sieving was determined. Subsequently, the sieve was set in a powder tester (manufactured by Hosokawa Micron Corporation), and the sieve for evaluation was sieved by vibrating the sieve for 30 seconds under the conditions of the rheostat scale 5 according to the manual of the powder tester. After sieving, the mass of the toner that did not pass through the sieve was measured. Based on the mass of the toner before sieving and the mass of the toner after sieving, the degree of toner aggregation (unit: mass%) was determined according to the following formula. The “mass of toner after sieving” in the following formula is the mass of toner that has not passed through the sieve, and is the mass of toner remaining on the sieve after sieving.
Toner aggregation degree = 100 × mass of toner after sieving / mass of toner before sieving

  The results are shown in Table 3. When the toner aggregation degree was 50% by mass or less, it was evaluated as normal. A toner aggregation degree of 40% by mass or less was evaluated as good.

  In Table 3, “Numerical aperture” indicates the number of surface recesses per unit area of the surface area of the toner particles. In the case of “inorganic particles”, “present” is described when the inorganic particles are present in the inner region of the base recess in the interface between the toner core and the shell layer. On the other hand, when the inorganic particles are not present in the inner region of the base recess in the interface between the toner core and the shell layer, “None” is indicated.

  The “fixing temperature” is the minimum fixing temperature. “Saturation” indicates a variation value (unit:%) of saturation. “Aggregation degree” describes the toner aggregation degree.

Toners T-1 to T-7 (toners according to Examples 1 to 7) each had the above-described basic configuration. Specifically, the toners according to Examples 1 to 7 each include a plurality of toner particles each including a toner core and a shell layer that covers the surface of the toner core. A plurality of first recesses were formed on the surface of the toner core. The shell layer was present in both the inner region of the first recess and the outer region of the first recess in the surface region of the toner core. A second concave portion corresponding to the first concave portion was formed on the surface of the toner particles. The number of second recesses per unit area of the surface area of the toner particles was 0.30 / μm ² or more. A plurality of inorganic particles containing an inorganic material existed in the inner region of the first recess in the interface between the toner core and the shell layer. The thermal conductivity of the inorganic particles was 40 W / m · K or more. The number average primary particle diameter of the inorganic particles was 100 nm or less.

  As shown in Table 3, each of the toners T-1 to T-7 was excellent in low temperature fixability and prevented the occurrence of low temperature offset. In addition, the toner was excellent in charging stability and the degree of toner aggregation was kept low.

  With toner T-8 (toner according to comparative example 1), the minimum fixing temperature was higher than that of toners T-1 to T-7. The reason why such a result is obtained is considered as follows. With toner T-8, a toner core was produced without using any of aluminum nitride particles, boron nitride particles, aluminum oxide particles, and silicon carbide particles. Therefore, none of the aluminum nitride particles, boron nitride particles, aluminum oxide particles, and silicon carbide particles existed in the inner region of the base recess in the interface between the toner core and the shell layer (see Table 3).

  With toner T-9 (toner according to Comparative Example 2), the minimum fixing temperature was higher than that of toners T-1 to T-7. The reason why such a result is obtained is considered as follows. The thermal conductivity of the inorganic particles used in the toner T-9 was very small compared to the thermal conductivity of the inorganic particles used in the toners T-1 to T-7.

  With toner T-10 (toner according to Comparative Example 3), the minimum fixing temperature was higher than that of toners T-1 to T-7. The reason why such a result is obtained is considered as follows. The number average primary particle size of the aluminum nitride particles used in the toner T-10 was larger than the number average primary particle size of the inorganic particles used in the toners T-1 to T-7. Therefore, it is difficult to ensure the amount of aluminum nitride particles present in the inner region of the base recess in the interface between the toner core and the shell layer. In addition, the number of surface recesses per unit area of the surface area of the toner particles was smaller for toner T-10 than for toners T-1 to T-7 (see Table 3). Here, the surface recesses are formed on the surface of the toner particles corresponding to the base recesses. Therefore, if the number of surface recesses per unit area of the surface area of the toner particles is small, the number of base recesses per unit area of the surface area of the toner core is reduced. This also makes it difficult to secure the abundance of aluminum nitride particles in the inner region of the underlying recess in the interface between the toner core and the shell layer.

  The toner T-11 (the toner according to Comparative Example 4) had a minimum fixing temperature higher than those of the toners T-1 to T-7. The reason why such a result is obtained is considered as follows. In the toner T-11, the aqueous sodium hydroxide solution was not added to the flask in the temperature raising step when forming the shell layer. Therefore, it is difficult to form a base recess on the surface of the toner core. Therefore, aluminum nitride particles did not exist in the inner region of the base recess in the interface between the toner core and the shell layer (see Table 3). Moreover, it was difficult to form a surface recess (see Table 3).

Further, the toners T-1 to T-6 (the toners according to Examples 1 to 6) had higher saturation variation values than the toner T-7 (the toner according to Example 7). The reason why such a result is obtained is considered as follows. The volume specific resistance value of the inorganic particles used in each of the toners T-1 to T-6 was 1.0 × 10 ¹⁴ Ω · cm or more, whereas that of the inorganic particles used in the toner T-7. The volume resistivity value was 1.0 × 10 ⁸ Ω · cm. As a result, the toners T-1 to T-6 can further prevent a decrease in the electrical resistance of the toner as compared with the toner T-7, and thus can further prevent a decrease in the charge amount of the toner. outstanding.

  The toner for developing an electrostatic latent image according to the present invention can be used to form an image in, for example, a copying machine, a printer, or a multifunction machine.

DESCRIPTION OF SYMBOLS 10 Toner base particle 11 Toner core 12 Shell layer 12A Surface 13 Interface 15a-15d Inorganic particle H11-H14 Base recessed part H22, H23 Surface recessed part

Claims (5)

An electrostatic latent image developing toner comprising a plurality of toner particles comprising a toner core and a shell layer covering the surface of the toner core,
A plurality of first recesses are formed on the surface of the toner core,
The shell layer is present in both the inner region of the first recess and the outer region of the first recess in the surface region of the toner core;
On the surface of the toner particles, a second recess corresponding to the first recess is formed,
The number of the second recesses per unit area of the surface area of the toner particles is 0.30 / μm ² or more,
A plurality of inorganic particles containing an inorganic material are present in the inner region of the first recess in the interface between the toner core and the shell layer,
The thermal conductivity of the inorganic particles is 40 W / m · K or more,
A toner for developing an electrostatic latent image, wherein the number average primary particle diameter of the inorganic particles is 100 nm or less. The toner for developing an electrostatic latent image according to claim 1, wherein the inorganic particles have a volume resistivity of 1.0 × 10 ¹⁴ Ω · cm or more.   The electrostatic latent image developing toner according to claim 2, wherein the inorganic material is at least one of aluminum nitride, boron nitride, and aluminum oxide. A step of preparing a toner core;
Providing an aqueous medium comprising the prepared toner core and shell material and having a pH of 3 to 6;
A temperature raising step for raising the temperature of the prepared aqueous medium to a predetermined target temperature;
Maintaining the temperature of the aqueous medium at the target temperature after completion of the temperature raising step;
Including
The step of preparing the toner core includes:
A first mixing step of mixing an amorphous polyester resin having a softening point equal to or lower than the target temperature and inorganic particles containing an inorganic material;
A second mixing step of mixing the mixture obtained in the first mixing step with an amorphous polyester resin having a softening point higher than the target temperature,
The thermal conductivity of the inorganic particles is 40 W / m · K or more,
The number average primary particle diameter of the inorganic particles is 100 nm or less,
The temperature raising step further includes a step of changing the pH of the aqueous medium from 8 to 12 when the temperature of the aqueous medium reaches a pH change temperature,
The method for producing toner for developing an electrostatic latent image, wherein the pH change temperature is lower than the target temperature. The rate of temperature rise is 0.1 ° C./min or more and 1.0 ° C./min or less,
The method for producing a toner for developing an electrostatic latent image according to claim 4, wherein the target temperature is 60 ° C. or higher and 70 ° C. or lower, and the pH change temperature is 30 ° C. or higher and 40 ° C. or lower.

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