JP6720922B2 - Toner for developing electrostatic latent image and manufacturing method thereof - Google Patents

Description

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

A two-component developer is known as a developer used for development. The two-component developer contains toner and a carrier that charges the toner positively or negatively by friction. The toner includes a plurality of toner particles. The toner particles each include a toner base particle and a plurality of external additive particles attached to the surface of the toner base particle. For example, Patent Document 1 describes the use of silica particles as external additive particles.

JP, 2004-212508, A

External additive particles may detach from the surface of the toner mother particles during image formation. For example, when the toner is agitated in the developing device to charge the toner positively or negatively, the toner is subjected to thermal stress or mechanical stress. Therefore, when the toner is stirred in the developing device (hereinafter, referred to as “stirring of the toner”), the external additive particles are detached from the surface of the toner mother particles (hereinafter, “external additive particle detachment”). ]) is likely to occur. In particular, when the electrostatic attractive force acting between the toner mother particles and the external additive particles is small, or when the total amount of toner replenished to the image forming apparatus increases due to the increase in the number of printed sheets, The detachment of the additive particles becomes remarkable.

When the external additive particles are detached from the surface of the toner base particles, the external additive particles detached from the surface of the toner base particles (hereinafter referred to as “released particles”) become a member different from the toner base particles. May adhere. For example, if the external additive particles are detached when the toner is stirred, the detached particles may adhere to the carrier. When the detached particles adhere to the carrier, triboelectric charging hardly occurs between the toner and the carrier. Therefore, toner charging failure may occur. For example, the oppositely charged toner may be scattered. Therefore, fogging may occur in the formed image.

It is considered that the fogging can be prevented if the detachment of the external additive particles during the image formation can be prevented. However, it is not realistic to completely prevent detachment of the external additive particles during image formation, particularly to completely prevent detachment of the external additive particles during stirring of the toner. On the other hand, it is required to form an image having excellent image quality.

The present invention has been made in view of such circumstances, and an object thereof is to form an image having excellent image quality even when detachment of external additive particles occurs during image formation. Another object of the present invention is to provide a toner for developing an electrostatic latent image and a method for producing the same.

The electrostatic latent image developing toner according to the present invention contains a plurality of toner particles. The toner particles each include a toner mother particle and an external additive that adheres to the surface of the toner mother particle. Each of the toner mother particles has 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 an inner region of the first recess and an outer region of the first recess in a surface region of the toner core. A second concave portion corresponding to the first concave portion is formed on the surface of the toner mother particle. The number of the first recesses per unit area of the surface area of the toner core is 0.30/μm ² or more. The cross-sectional area of the toner core is composed of a first area that is within 500 nm from the inner area of the first recess and a second area that is an area other than the first area. The toner cores each have a plurality of high dielectric constant domains. Each of the high dielectric constant domains includes high dielectric constant particles having a relative dielectric constant of 100 or more. The ratio of the total area occupied by the high dielectric constant domain in the first region is higher than the ratio of the total area occupied by the high dielectric constant domain in the second region.

The method for producing a toner for developing an electrostatic latent image according to the present invention includes a step of producing toner base particles and a step of mixing the toner base particles and external additive particles. The step of producing toner mother particles includes the step of producing a toner core and the step of forming a shell layer on the surface of the toner core. In the step of producing the toner core, the first amorphous polyester resin and the high dielectric constant particles are mixed to obtain a mixture in which the high dielectric constant particles are dispersed in the first amorphous polyester resin. A step of obtaining, a step of melt-kneading the toner core material containing the mixture and the second amorphous polyester resin to obtain a melt-kneaded material, and a step of pulverizing the melt-kneaded material to obtain a pulverized material containing a plurality of particles. And a step of obtaining. In the step of forming the shell layer, a step of preparing a liquid containing the toner core and the shell material and having a pH of 6 or less, and a temperature raising step of raising the temperature of the liquid to a first target temperature, And a step of changing the pH of the liquid to 8 or more when the temperature of the liquid reaches the second target temperature in the temperature raising step. The softening point of the second non-crystalline polyester resin is higher than the softening point of the first non-crystalline polyester resin. The high dielectric constant particles have a relative dielectric constant of 100 or more. The first target temperature is higher than the softening point of the first non-crystalline polyester resin and lower than the softening point of the second non-crystalline polyester resin. The second target temperature is a temperature lower than the softening point of the first amorphous polyester resin.

According to the toner for developing an electrostatic latent image of the present invention, an image having excellent image quality can be formed even when detachment of external additive particles occurs during image formation.

FIG. 3 is a diagram showing an example of a cross-sectional structure of toner particles 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 area of the surface area of the toner mother particles shown in FIG. 1. It is a figure which shows the area|region within 500 nm from the inner surface of a 1st recessed part.

An embodiment of the present invention will be described. Unless otherwise specified, the evaluation result (value indicating shape or physical property) of the powder is the number average of the values measured for a considerable number of particles. Examples of the powder include a toner core, toner mother particles, an external additive, and a toner.

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

The glass transition point (Tg) is a value measured according to "JIS (Japanese Industrial Standard) K7121-2012" using a differential scanning calorimeter ("DSC-6220" manufactured by Seiko Instruments Inc.), unless otherwise specified. Is. Further, the softening point (Tm) is a value measured using a Koka type flow tester (“CFT-500D” manufactured by Shimadzu Corporation) unless otherwise specified. In the S-shaped curve (horizontal axis: temperature, vertical axis: stroke) measured with a Koka type flow tester, the temperature at which "(baseline stroke value + maximum stroke value)/2" becomes Tm (softening point) Equivalent to. The melting point (Mp) measured value is an endothermic curve (vertical axis: heat flow (DSC) measured using a differential scanning calorimeter (“DSC-6220” manufactured by Seiko Instruments Inc.) unless otherwise specified. Signal), horizontal axis: temperature) is the temperature of the maximum endothermic peak. This endothermic peak appears due to melting of the crystallization site.

The "main component" of a material means the component most abundant in the material on a mass basis, unless otherwise specified.

Hereinafter, a compound and its derivatives may be generically referred to by adding "system" after the compound name. When a "system" is added after the compound name to represent the polymer name, it means that the repeating unit of the polymer is derived from the compound or its derivative. In addition, acrylic and methacrylic may be collectively referred to as “(meth)acrylic”. In addition, acrylonitrile and methacrylonitrile may be collectively referred to as “(meth)acrylonitrile”.

The toner for developing an electrostatic latent image according to the present exemplary embodiment (hereinafter, referred to as “toner”) can be suitably used for developing an electrostatic latent image, for example, as a positive charging toner. The toner according to this exemplary embodiment may be used as a one-component developer. The positively chargeable toner contained in the one-component developer is positively charged by friction with the developing sleeve or the blade in the developing device. Further, the two-component developer may be prepared by mixing the toner and the carrier using a mixing device (for example, a ball mill). The positively chargeable toner contained in the two-component developer is positively charged by friction with the carrier in the developing device.

The toner according to this exemplary embodiment is a powder containing a plurality of toner particles. The toner particles each include a toner core and a shell layer that covers the surface of the toner core. The shell layer is substantially composed of resin. For example, by covering the toner core that melts at a low temperature with a shell layer having excellent heat resistance, it is possible to achieve both heat-resistant storage stability and low-temperature fixability of the toner. Additives may be dispersed in the resin forming the shell layer. An external additive is preferably attached to the surface of the shell layer or the surface area of the toner core not covered with the shell layer. Hereinafter, the toner particles before the external additive is attached are referred to as toner mother particles.

The toner according to this exemplary embodiment can be used for forming an image in, for example, an electrophotographic apparatus (image forming apparatus). The electrophotographic apparatus preferably includes a charging device and an exposure device as an image forming unit. It is preferable that the electrophotographic apparatus further includes a developing device, a transfer device, and a fixing device. Hereinafter, an example of the image forming method by the electrophotographic apparatus will be described.

First, the image forming unit of the electrophotographic apparatus forms an electrostatic latent image on the photoconductor based on the image data. In the subsequent developing step, the developing device of the electrophotographic apparatus (specifically, the developing device in which the developer containing toner is set) supplies the toner to the photoconductor to develop the electrostatic latent image formed on the photoconductor. To do. Before being supplied to the photosensitive member, the toner is charged by friction with the carrier, the developing sleeve, or the blade in the developing device. For example, a positively chargeable toner is positively charged. In the developing step, the toner on the developing sleeve arranged in the vicinity of the photoconductor (specifically, the charged toner) is supplied to the photoconductor, and the supplied toner adheres to the electrostatic latent image of the photoconductor, A toner image is formed on the photoconductor. The consumed toner is replenished to the developing device from a toner container containing replenishment toner. The photoconductor corresponds to, for example, the surface layer of the photoconductor drum. The developing sleeve corresponds to, for example, the surface layer portion of the developing roller in the developing device.

In the subsequent transfer step, the transfer device of the electrophotographic apparatus transfers the toner image on the photoconductor to the intermediate transfer body, and then transfers the toner image on the intermediate transfer body to the recording medium. Then, the fixing device of the electrophotographic apparatus heats and pressurizes the toner to fix the toner on the recording medium. As a result, an image is formed on the recording medium. For example, a full-color image can be formed by superimposing toner images of four colors of black, yellow, magenta, and cyan. After the transfer step, the toner remaining on the photoconductor is removed by the cleaning member. A transfer belt is an example of the intermediate transfer member. An example of the recording medium is printing paper. A cleaning blade is an example of the cleaning member. The transfer method is not limited to the indirect transfer method and may be a direct transfer method. In the direct transfer method, the toner image on the photoconductor is directly transferred to the recording medium without passing through the intermediate transfer body. The fixing method may be a nip fixing method using a heating roller and a pressure roller, or a belt fixing method.

[Basic configuration of toner]
The toner according to this exemplary embodiment has the following configuration (hereinafter referred to as the basic configuration). Specifically, the toner according to this exemplary embodiment includes a plurality of toner particles. The toner particles each include a toner mother particle and an external additive that adheres to the surface of the toner mother particle. Each of the toner mother particles has 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 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 mother particle. The number of the first recesses per unit area of the surface area of the toner core is 0.30/μm ² or more. The cross-sectional area of the toner core is composed of a first area that is within 500 nm from the inner area of the first recess and a second area that is an area other than the first area. The toner cores each have a plurality of high dielectric constant domains. The high dielectric constant domains each include high dielectric constant particles having a relative dielectric constant of 100 or more. The ratio of the total area occupied by the high dielectric constant domain in the first region is higher than the ratio of the total area occupied by the high dielectric constant domain in the second region. Hereinafter, the first recess will be referred to as a "base recess". In addition, the second recess is referred to as a “surface recess”.

Here, by observing the surface area of the toner mother particles using a field emission scanning electron microscope (FE-SEM) (for example, "JSM-7600F" manufactured by JEOL Ltd.), the unit of the surface area of the toner core is measured. The number of base recesses per area can be obtained. It is preferable to observe the surface area of the toner base particles after removing the external additive from the surface of the toner base particles.

The distribution of the high dielectric constant domain in the toner core can be confirmed by observing a cross-sectional TEM photograph of the toner mother particles using a transmission electron microscope (TEM, for example, "H-7100FA" manufactured by Hitachi High-Technologies Corporation). It is preferable to observe a cross-sectional TEM photograph of the toner mother particles after removing the external additive from the surface of the toner mother particles.

Further, using a rotary rheometer (for example, "ARES-G2" manufactured by TA Instruments Co., Ltd.) and an LCR meter (for example, "4284A Precision LCR meter" manufactured by Keysight Technologies, Inc.), high dielectric constant particles are used. The relative permittivity of can be calculated. Specifically, the relative permittivity of the high permittivity particles can be determined by the method described in Examples below or a method similar thereto.

[Toner composition]
Hereinafter, the toner having the above-described basic configuration will be specifically described with reference to FIGS. In the drawings, the same reference numerals indicate the same or corresponding parts. The dimensional relationships such as length, width, thickness, and depth are appropriately changed for the sake of clarity and simplification of the drawings, and do not represent actual dimensional relationships.

FIG. 1 is a diagram showing an example of the configuration of the toner according to the present exemplary embodiment. The toner according to this exemplary embodiment includes a plurality of toner particles 10. Each of the toner particles 10 includes a toner mother particle 20 and a plurality of external additive particles 30 attached to the surface of the toner mother particle 20. The toner mother particles 20 each have a toner core 21 and a shell layer 23 that covers the surface of the toner core 21. The external additive particles 30 may be attached to the surface of the toner mother particles 20, may be attached to the surface of the shell layer 23, or may be attached to a portion of the surface area of the toner core 21 exposed from the shell layer 23. It may be attached.

FIG. 2 is an enlarged view showing a partial area of the surface area of the toner mother particles 20. As shown in FIG. 2, a plurality of base recesses H11 to H13 are formed on the surface of the toner core 21. The number of base recesses H1 per unit area of the surface area of the toner core 21 is 0.30/μm ² or more. Hereinafter, when it is not necessary to distinguish between the base recesses H11 to H13, each of the base recesses H11 to H13 is referred to as a “base recess H1”.

The base recess H1 preferably has a depth of 100 nm or more. Therefore, minute irregularities that are naturally formed on the surface of the toner core 21 unintentionally are not included in the base concave portion H1. More preferably, the depth of the base recess H1 is 3 μm or less. As a result, the ease of forming the base recess H1 can be ensured, and thus the ease of processing the toner core 21 can be ensured. More preferably, the depth of the base recess H1 is 500 nm or less. As a result, the number of base recesses H1 on the surface of the toner core 21 can be secured. Here, the planar shape of the base recess H1 on the surface of the toner core 21 is arbitrary, and may be a perfect circle, an ellipse, a polygon, or an irregular shape. Further, in FIG. 2, the depth D1 of the base recess H11 is shown as an example of the depth of the base recess H1.

The shell layer 23 exists in the inner region of the base recess H12 and the outer region of the base recess H12 in the surface region of the toner core 21. Further, the shell layer 23 exists in the inner region of the base recess H13 and the outer region of the base recess H13 in the surface region of the toner core 21. Therefore, the surface recesses H22 corresponding to the base recesses H12 and the surface recesses H23 corresponding to the base recesses H13 are formed on the surface of the toner mother particles 20. Hereinafter, when it is not necessary to distinguish between the surface recesses H22 and H23, each of the surface recesses H22 and H23 is referred to as a “surface recess H2”. Although the shell layer 23 is shown in FIG. 2 as a film without graininess, the shell layer 23 may be a film with graininess. When resin particles are used as a material for forming the shell layer 23, if the material (resin particles) is completely melted and cured in a film-like form, a film without a granular feeling is formed as the shell layer 23. Conceivable. On the other hand, if the material (resin particles) is not completely melted and is cured in a film-like form, a film having a form in which the resin particles are two-dimensionally connected (a film having a granular feeling) is formed as the shell layer 23. it is conceivable that.

The surface recess H2 preferably has a depth of 100 nm or more. Therefore, minute irregularities that are spontaneously formed on the surface of the toner mother particles 20 unintentionally are not included in the surface concave portions H2. If the thickness of the shell layer 23 is sufficiently smaller than the depth of the base recess H1, it is considered that the depth of the surface recess H2 is substantially the same as the depth of the base recess H1. For example, if the depth of the base recess H1 is 100 nm or more and the thickness of the shell layer 23 is 1 nm or more and 50 nm or less, the depth of the surface recess H2 is likely to be 100 nm or more. Note that FIG. 2 shows the depth D3 of the surface recess H23 as an example of the depth of the surface recess H2. Further, in FIG. 2, the range of the inner region of the base recess H13 is described as range R3.

The shell layer 23 does not exist in the inner region of the base recess H11. As described above, the shell layer 23 does not have to be present in the inner region of the base recess H1 in some of the plurality of base recesses H1. If the shell layer 23 does not exist in the inner region of the base recess H1, the surface recess H2 corresponding to the base recess H1 is not formed on the surface of the toner mother particle 20. In order to secure the mechanical strength of the toner mother particles 20, the number of surface recesses H2 per unit area of the surface region of the toner mother particles 20 is preferably 0.30/μm ² or more. Note that, in FIG. 2, the range of the inner region of the base recess H11 is described as a range R1.

The toner core 21 has a plurality of high dielectric constant domains 25. The high dielectric constant domains 25 each include one or more high dielectric constant particles. The relative permittivity of the high permittivity particles is 100 or more. Such a high dielectric constant domain 25 preferentially exists around the base recess H1. Hereinafter, the toner core 21 will be further described with reference to FIG.

FIG. 3 is a diagram showing a region within 500 nm from the inner surface of the base recess H1. The cross-sectional area of the toner core 21 is composed of a first area F1 and a second area F2. The first region F1 corresponds to a region within 500 nm from the region inside the base recess H1. In FIG. 3, the first region F1 corresponds to the shaded region, and therefore the distance d11 corresponds to 500 nm. The second area F2 is an area other than the first area F1. Therefore, the second region F2 corresponds to a region more than 500 nm away from the inner region of the base recess H1.

In the toner core 21, the ratio of the total area occupied by the high dielectric constant domain 25 in the first region F1 is higher than the ratio of the total area occupied by the high dielectric constant domain 25 in the second region F2. For example, the ratio of the total area occupied by the high dielectric constant domain 25 in the first region F1 is 20% or more and 60% or less, and the ratio of the total area occupied by the high dielectric constant domain 25 in the second region F2 is 1%. It is preferably 10% or less. Further, it is preferable that at least one high dielectric constant domain 25 exists in the first region F1 in more than half of the underlying recesses H1. As described above, in the present embodiment, the relative permittivity of the first region F1 is higher than that of the second region F2. Here, the first region F1 corresponds to a region within 500 nm from the region inside the base recess H1, and the second region F2 corresponds to a region other than the first region F1. Therefore, in the present embodiment, a region having a high relative dielectric constant (more specifically, the first region F1) exists on the surface side of the toner core 21.

Generally, the electrostatic attractive force acting between two objects tends to increase as the distance between the objects decreases. Therefore, if a region having a high relative dielectric constant exists on the surface side of the toner core 21, a relatively large electrostatic attractive force acts between the high dielectric constant domain 25 and the detached particles existing on the surface side of the toner core 21. To do. Therefore, even if the external additive particles 30 are detached during image formation, the detached particles are electrostatically attracted to the surface area of the toner mother particles 20 during image formation. For example, even when the external additive particles 30 are desorbed when the toner is stirred, the desorbed particles are electrostatically attracted to the surface area of the toner mother particles 20 when the toner is stirred. In the following description, "the detached particles are electrostatically attracted to the surface area of the toner base particles 20 during image formation (for example, when the toner is stirred)" means that the detached particles are toner base particles during the image formation. 20 surface areas”.

If the detached particles are collected in the surface area of the toner mother particles 20 during image formation, it is possible to prevent the detached particles from adhering to the carrier during image formation. This causes triboelectric charging between the toner and the carrier. Therefore, it is possible to prevent the toner from being defectively charged. For example, it is possible to prevent the reversely charged toner from scattering. Therefore, by forming an image using the toner according to the present exemplary embodiment, it is possible to prevent fogging in the formed image even if the external additive particles 30 are detached during the image formation. ..

If the detached particles are collected in the surface area of the toner mother particles 20 during image formation, it is possible to prevent the detached particles from adhering to the developing sleeve or the photoreceptor during image formation. As a result, when an image is formed using the toner according to the present exemplary embodiment, an image having excellent image density and image quality can be formed even when the external additive particles 30 are detached during image formation. ..

As described above, in the present embodiment, even when the external additive particles 30 are detached during image formation, the detached particles are collected in the surface area of the toner mother particles 20 during image formation. It is possible to prevent image defects from occurring in the formed image. For example, even when detachment of the external additive particles 30 occurs during continuous printing, it is possible to prevent image defects from occurring in any of the formed images. Therefore, it is possible to prevent image defects from occurring for a long period of time.

As described above, the electrostatic attractive force acting between two objects tends to increase as the distance between the objects decreases. The present inventor believes that if the thickness of the shell layer 23 is 50 nm or less, the detached particles can be collected even in the surface region of the toner mother particle 20 where the shell layer 23 exists. Therefore, the thickness of the shell layer 23 is preferably 50 nm or less.

The form of collecting the released particles in the surface region of the toner mother particles 20 is not particularly limited. In a portion of the surface area of the toner base particles 20 where the shell layer 23 does not exist, the detached particles are contained in the internal space of the base recess H1, in a form of closing the opening of the base recess H1, or the toner base particles. The toner may be collected in the surface area of the toner mother particles 20 in a form of being attached to a portion of the surface area of the base concave portion H1 located on the peripheral edge of the opening. In the area where the shell layer 23 exists in the surface area of the toner base particles 20, the detached particles are contained in the internal space of the surface recess H2, close the opening of the surface recess H2, or the toner base particles. The toner may be collected in the surface area of the toner mother particles 20 in a form of being attached to a portion of the surface area of the toner 20 located at the opening peripheral edge of the surface recess H2. If the desorbed particles are collected in the surface area of the toner base particles 20 in a form of being accommodated in the internal space of the base recess H1 or the internal space of the surface recess H2, the circular shape of the toner base particles due to the recovery of the released particles. It is possible to prevent an excessive decrease in the degree.

The inventor initially considered increasing the electrostatic attraction acting between the toner base particles and the detached particles by uniformly increasing the relative dielectric constant over the entire toner core. However, if the relative dielectric constant is uniformly increased over the entire toner core, the electrostatic attractive force acting between the toner base particles and other members tends to increase over the entire surface area of the toner base particles. Therefore, the toner mother particles are easily attached to the carrier, the developing sleeve, or the photoconductor. This may reduce the developability of the toner.

However, in the present embodiment, the ratio of the total area occupied by the high dielectric constant domain 25 in the first region F1 is higher than the ratio of the total area occupied by the high dielectric constant domain 25 in the second region F2. As a result, it is possible to prevent the electrostatic attraction acting between the toner mother particles 20 and other members from increasing over the entire surface area of the toner mother particles 20. Therefore, it is possible to prevent the toner mother particles 20 from adhering to the carrier, the developing sleeve, or the photoconductor during image formation. Therefore, it is possible to prevent the developability of the toner from decreasing.

Moreover, the first region F1 corresponds to a region within 500 nm from the inner region of the base recess H1. Here, the inner region of the base recessed portion H1 exists inside the toner mother particles 20 in the radial direction with respect to the surface region of the toner mother particles 20. Therefore, when an image is formed using the toner according to the present exemplary embodiment, it is possible to prevent the inner region of the base recess H1 from coming into contact with the developing sleeve or the photoconductor, so that the first region F1 comes into contact with the developing sleeve or the photoconductor. Can be effectively prevented. This also prevents the toner mother particles 20 from adhering to the developing sleeve or the photoconductor during image formation.

Further, in the present embodiment, the number of the base recesses H1 per unit area of the surface region of the toner core 21 is 0.30/μm ² or more. As a result, the number of the first areas F1 in the toner core 21 is easily secured. Therefore, it is easy to secure the number of detached particles collected in the surface region of the toner mother particles 20 during image formation. Also by this, if an image is formed using the toner according to the present exemplary embodiment, even if detachment of the external additive particles 30 occurs during image formation, an image defect occurs in the formed image. Can be prevented.

If the number of base recesses H1 per unit area of the surface area of the toner core 21 becomes too large, the number of the first areas F1 in the toner core 21 becomes excessive. Therefore, the electrostatic attractive force acting between the toner mother particles 20 and other members may become large over the entire surface area of the toner mother particles 20. Considering this, the number of the base recesses H1 per unit area of the surface area of the toner core 21 is preferably 1.00/μm ² or less, and more preferably 0.60/μm ² or less. .. The configuration of the toner has been described above with reference to FIGS. Hereinafter, a more preferable toner structure will be described with reference to FIGS. 1 to 3.

First, a preferable structure of the toner mother particles will be described.
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 “total shell coverage”) is preferably 30% or more and 80% or less. As described above, the shell layer has higher heat resistance than the toner core. Therefore, even if heat is applied to the toner during image formation, melting of the shell layer in the surface region of the toner core can be prevented.

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 “recess shell coverage”) is preferably 30% or more and 80% or less. As described above, the shell layer has higher heat resistance than the toner core. Therefore, even if heat is applied to the toner at the time of image formation, melting of the shell layer in the inner region of the base recess can be prevented.

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

The recessed shell coverage (unit: %) is represented by the formula “recessed shell coverage=100×area of inner region of underlying recess covered by shell layer/total area of inner region of underlying recess”. The 100% coverage of the recessed shell means that the entire inner region of the underlying recessed portion is covered with the shell layer.

The overall shell coverage and the recessed shell coverage can be determined according to the following methods. First, toner particles that have not been subjected to external addition processing (for example, toner mother particles) are Ru-dyed. Of the surface area of the toner core, the area covered with the shell layer is more likely to be dyed with ruthenium than the area not covered with the shell layer. The dyed toner particles are observed with a field emission scanning electron microscope (FE-SEM) (for example, "JSM-7600F" manufactured by JEOL Ltd.) at a magnification of 50,000 times to obtain a backscattered electron image of the toner particles. ..

Using image analysis software (for example, "WinROOF" manufactured by Mitani Corporation), the obtained backscattered electron image is binarized. Then, the area S _{A1 of the} entire backscattered electron image of the toner particles and the area S _B1 of a relatively bright region in the backscattered electron image are obtained, and the total shell coverage (unit: %) is calculated according to the following formula.
Overall shell coverage = 100 x area S _B1 / area S _A1

The area S _A2 of the inner region of the base recess and the area of the inner region of the base recess are relatively bright in the same manner as in the method for measuring the overall shell coverage except that the observation magnification is changed from 50,000 to 100,000. The area S _{B2 of the} region is obtained. Then, the recessed shell coverage (unit: %) is calculated according to the following formula.
Recessed shell coverage = 100 x area S _B2 / area S _A2

Next, a preferable configuration of the toner core will be described. The opening area of the base concave portion on the surface of the toner core is preferably 0.5 μm ² or more and 10 μm ² or less. This makes it easy to secure the mechanical strength of the toner core. For the opening area of the base concave portion, for example, an image of toner mother particles (for example, pre-stained toner mother particles) taken by a field emission scanning electron microscope (“JSM-7600F” manufactured by JEOL Ltd.) is analyzed. It can be measured.

The toner core preferably contains a binder resin. More preferably, the toner core has the following configurations X1 and X2. If the toner core has the following configurations X1 and X2, the toner according to this exemplary embodiment can be easily manufactured by the method described in [Toner manufacturing method] described below.
Structure X1: The toner core contains a first amorphous polyester resin having a softening point of 70° C. or lower and a second amorphous polyester resin having a softening point of 100° C. or higher.
Structure X2: The proportion of the first amorphous polyester resin in the resin contained in the toner core is 50% by mass or more and 80% by mass or less.

Next, the high dielectric constant domain will be further described. The high dielectric constant domain may include one high dielectric constant particle, or may include two or more high dielectric constant particles. When the high dielectric constant domain includes two or more high dielectric constant particles, two or more high dielectric constant particles may be arranged in a two-dimensional array, or two or more high dielectric constant particles may be three-dimensionally arranged. May be arranged in series.

The number average primary particle diameter of the high dielectric constant particles is preferably 300 nm or less. When the number average primary particle diameter of the high dielectric constant particles is 300 nm or less, the high dielectric constant particles are likely to exist on the surface side of the toner core. As a result, the distance between the high-dielectric-constant particles and the desorbed particles tends to be short, so that the electrostatic attractive force acting between the high-dielectric-constant particles and the desorbed particles tends to increase. Therefore, the detached particles are easily collected in the surface area of the toner mother particles during image formation. More preferably, the number average primary particle diameter of the high dielectric constant particles is 200 nm or less. Considering the availability of the high dielectric constant particles, the number average primary particle diameter of the high dielectric constant particles is preferably 5 nm or more. In order to secure the handleability of the high dielectric constant particles, the number average primary particle diameter of the high dielectric constant particles is preferably 10 nm or more.

If the content of the high dielectric constant particles in the toner core is too small and the external additive particles are detached during image formation, image defects may occur in the formed image. On the other hand, if the content of the high dielectric constant particles in the toner core is too large, it may not be possible to form an image. Considering these, it is preferable to determine the content of the high dielectric constant particles in the toner core. For example, the content of the high dielectric constant particles is preferably 0.5 part by mass or more and 15.0 parts by mass or less with respect to 100.0 parts by mass of the toner core.

The particles having a relative dielectric constant of 100 or more (high dielectric constant particles) are preferably titanium dioxide particles, strontium titanate particles, or barium titanate particles, respectively. For example, the high dielectric constant domain may include one or more high dielectric constant particles each containing the same high dielectric constant material, or two or more high dielectric constant particles containing different high dielectric constant materials. May be included.

Next, the external additive particles will be further described. The external additive particles preferably include silica particles. When the external additive particles further include other particles that are not silica particles, the relative dielectric constant of the other particles is preferably lower than the relative dielectric constant of the high dielectric constant particles. If the relative permittivity of the other particles is lower than the relative permittivity of the high permittivity particles, it is possible to prevent silica particles from adhering to the surface of the other particles during toner production. This allows the other particles to function as external additive particles.

[Toner manufacturing method]
The following first and second methods are conceivable as methods of manufacturing the toner according to this exemplary embodiment.
First method: First, a toner core having a plurality of high dielectric constant domains is prepared. Next, a base recess is formed in a portion of the surface area of the toner core that is close to the high dielectric constant domain. Then, a shell layer is formed in the inner region and the outer region of the base recess.
Second method: First, a shell layer is formed on the surface of a toner core having a plurality of high dielectric constant domains. Next, a recess is formed in a portion of the surface region of the shell layer that is close to the high dielectric constant domain.

However, according to the first method, since the depth of the base recess is as large as 100 nm or more, it is difficult to form the shell layer in the inner region of the base recess. Further, if the thickness of the shell layer is increased, the adhesive strength of the shell layer to the inner region of the underlying recess can be secured, but it is difficult to form the recess on the surface of the shell layer. Further, even if the surface of the toner core is observed, it is difficult to confirm the portion of the surface area of the toner core that is close to the high dielectric constant domain. Therefore, it is difficult to form the base recessed portion in a portion of the surface area of the toner core which is close to the high dielectric constant domain.

Further, in the second method, since the recess is formed on the surface of the shell layer, the shell layer may peel off when the recess is formed. Further, even if the surface of the shell layer is observed, it is difficult to confirm the portion of the surface region of the shell layer that is close to the high dielectric constant domain. Therefore, it is difficult to form the base recess in the surface region of the shell layer near the high dielectric constant domain.

As described above, it is difficult to manufacture the toner according to the exemplary embodiment by either the first method or the second method. The present inventor diligently studied the method for producing a toner according to this embodiment. Then, it was concluded that the toner according to the present embodiment can be manufactured by manufacturing the toner by the following method.

Specifically, the toner manufacturing method according to the present embodiment includes a toner mother particle manufacturing process and an external addition process. The production process of the toner mother particles includes a production process of the toner core and a formation process of the shell layer. In the manufacturing process of the toner core, first, the first amorphous polyester resin and high dielectric constant particles are mixed. In this way, a mixture (hereinafter, referred to as “mixture Y1”) in which the high dielectric constant particles are present in a state of being dispersed in the first amorphous polyester resin is obtained. Next, the toner material containing the mixture Y1 and the second amorphous polyester resin is melt-kneaded. The melt-kneaded product thus obtained is pulverized to obtain a pulverized product containing a plurality of particles.

In the step of forming the shell layer, first, a liquid containing the obtained toner core and the shell material and having a pH of 6 or less (hereinafter, referred to as “shell forming liquid”) is prepared. Next, the temperature of the shell forming liquid is raised to the first target temperature. At this time, when the temperature of the shell forming liquid reaches the second target temperature, the liquid property of the shell forming liquid is changed from acidic to alkaline. Hereinafter, “changing the liquidity of the shell-forming liquid from acidic to alkaline” is described as “changing the liquidity of the shell-forming liquid”.

Thus, in the shell layer forming step, the temperature of the shell forming liquid is raised. Here, the softening point of the second amorphous polyester resin is higher than the softening point of the first amorphous polyester resin. Therefore, when the temperature of the shell forming liquid is raised, the first non-crystalline polyester resin is more easily hydrolyzed than the second non-crystalline polyester resin.

Further, in the shell layer forming step, the liquidity of the shell forming liquid is changed when the temperature of the shell forming liquid reaches the second target temperature. Here, the second target temperature is lower than the softening point of the first amorphous polyester resin. Therefore, by changing the liquidity of the shell-forming liquid when the temperature of the shell-forming liquid reaches the second target temperature, the first non-crystalline polyester resin becomes the second non-crystalline polyester resin. It is considered that they are preferentially hydrolyzed.

When the first non-crystalline polyester resin is hydrolyzed preferentially as compared with the second non-crystalline polyester resin, the base recess is likely to be formed on the surface of the toner core. Here, the toner core contains the mixture Y1. Further, in the mixture Y1, the high dielectric constant particles are present in a state of being dispersed in the first amorphous polyester resin. Even if the first amorphous polyester resin is hydrolyzed, the high dielectric constant particles remain in the toner core without being hydrolyzed or dissolved. From these facts, when the base concave portion is formed on the surface of the toner core, the high dielectric constant particles existing in the vicinity of the surface of the toner core among the high dielectric constant particles dispersed in the mixture Y1 are converted into the base concave portion of the toner core. It becomes easy to exist in the site located around the inner region of the. In this way, the proportion of the total area occupied by the high dielectric constant domain in the first region becomes higher than the proportion of the total area occupied by the high dielectric constant domain in the second region.

The first target temperature is higher than the softening point of the first amorphous polyester resin and lower than the softening point of the second amorphous polyester resin. Therefore, the first target temperature is higher than the second target temperature. Therefore, in the toner manufacturing method according to the present embodiment, the temperature of the shell forming liquid is further increased even after the liquid property of the shell forming liquid is changed. It is considered that, as a result, a shell layer is formed on the surface of the toner core in which the base recess is formed. Hereinafter, each step will be specifically described.

<Production process of toner mother particles>
As described above, the step of producing the toner mother particles includes the step of producing the toner core and the step of forming the shell layer. In order to efficiently produce toner base particles, it is preferable to produce a large number of toner base particles at the same time. The toner mother particles produced at the same time are considered to have the same constitution as each other.

(Toner core manufacturing process)
It is preferable to produce the toner core by a pulverization method or an aggregation method. Thereby, the toner core can be easily obtained. Hereinafter, the manufacturing process of the toner core will be described by taking the method of manufacturing the toner core by the pulverization method as an example.

First, a mixture (mixture Y1) in which the high dielectric constant particles are present in a state of being dispersed in the first amorphous polyester resin is prepared. Specifically, the first amorphous polyester resin and the high dielectric constant particles are mixed using a mixing device (for example, an FM mixer). The obtained mixture is melt-kneaded to obtain a melt-kneaded product. For melt-kneading, a twin-screw extruder, a three-roll kneader, or a two-roll kneader can be preferably used. Next, the melt-kneaded product is cooled using a cooling and solidifying device such as a drum flaker. The obtained solidified product is crushed using a crushing device. In this way, the mixture Y1 is obtained.

Next, the mixture Y1 and the second amorphous polyester resin are mixed using a mixing device (for example, an FM mixer). At least one of a colorant, a release agent, and a charge control agent may be added to the mixture Y1 and the second amorphous polyester resin. The obtained mixture is melt-kneaded to obtain a melt-kneaded product. For melt-kneading, a twin-screw extruder, a three-roll kneader, or a two-roll kneader can be preferably used. Next, the melt-kneaded product is cooled using a cooling and solidifying device such as a drum flaker. The obtained solidified product is crushed using a crushing device. The obtained pulverized product is classified if necessary. In this way, a powder containing a plurality of toner cores is obtained.

(Formation of shell layer)
In the step of forming the shell layer, the shell layer is formed on the surface of the toner core. In order to suppress the dissolution or elution of the toner core components (particularly, the binder resin and the release agent) when forming the shell layer, it is preferable to form the shell layer in an aqueous medium.

First, a shell forming liquid is prepared. For the reasons mentioned above, the shell-forming liquid preferably contains an aqueous medium. The aqueous medium contains water as a main component and is preferably, for example, pure water or a mixed liquid of water and a polar medium. The aqueous medium may function as a solvent. The 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. For example, alcohol can be used as the polar medium in the aqueous medium, and methanol or ethanol can be used as the alcohol. The boiling point of the aqueous medium is preferably about 100°C. More preferably, ion-exchanged water is prepared as the aqueous medium.

The pH of the aqueous medium is adjusted to 6 or less using an acidic substance. Preferably, the pH of the aqueous medium is adjusted to 3 or more and 6 or less using an acidic substance. As the acidic substance, for example, hydrochloric acid or p-toluenesulfonic acid aqueous solution can be used. Then, the toner core and the shell material obtained by the above-described method are added to an aqueous medium whose pH is adjusted to 6 or less. A thermoplastic resin suspension is preferably used as the shell material. As the particle size of the resin particles contained in the suspension increases, the thickness of the shell layer formed tends to increase. Further, the larger the amount of the shell material added, the higher the coverage of the shell layer formed. In this way, a shell-forming liquid is obtained.

When the toner core and the shell material are added to the aqueous medium, the shell material (more specifically, resin particles) adheres to the surface of the toner core in the aqueous medium. In order to uniformly attach the shell material to the surface of the toner core, it is preferable to highly disperse the toner core in the liquid containing the shell material. In order to highly disperse the toner core in the liquid, a surfactant may be contained in the liquid, and the liquid is stirred using a powerful stirring device (for example, "Hibis Dispermix" manufactured by PRIMIX Corporation). May be. When the toner core has an anionic property, it is possible to suppress aggregation of the toner core by using anionic surfactants having the same polarity. As the anionic surfactant, for example, a sulfate ester salt, a sulfonate salt, a phosphate ester salt, or soap can be used.

Next, the shell forming liquid is raised to the first target temperature. For example, it is preferable to raise the shell forming liquid to the first target temperature while stirring the shell forming liquid. The temperature of the shell-forming liquid at the start of temperature increase is preferably a temperature selected from a temperature range of 20° C. or higher and 35° C. or lower. The rate of temperature increase is preferably a rate selected from a rate range of 0.1° C./min or more and 3.0° C./min or less, and more preferably 0.1° C./min or more and 1.0° C./min or less. It is a speed selected from the speed range.

When the temperature of the shell forming liquid reaches the second target temperature, the pH of the shell forming liquid is changed to 8 or higher. For example, by adding a basic substance to the shell-forming liquid, the pH of the shell-forming liquid can be changed to 8 or higher. As the basic substance, for example, sodium hydroxide can be used. Preferably, the pH of the shell-forming liquid is changed to 8 or more and 12 or less. If the pH of the shell-forming liquid becomes too high, the hydrolysis of the first amorphous polyester resin may proceed excessively. Further, it is preferable to change the liquidity of the shell-forming liquid in a short time (for example, within 10 seconds). The second target temperature is a temperature selected from a temperature range of 30° C. or higher and 60° C. or lower, and preferably a temperature selected from a temperature range of 30° C. or higher and 40° C. or lower.

Even after changing the liquidity of the shell-forming liquid, the temperature rise is not stopped and the temperature of the shell-forming liquid is raised to the first target temperature. As described above, it is considered that the surface of the toner core in which the base recess is formed is covered with the shell material by continuing the temperature increase even after changing the liquidity of the shell forming liquid. Therefore, by optimizing the temperature rising time after changing the liquidity of the shell forming liquid, the amount of the shell material attached to the surface of the toner core is optimized, and thus the thickness of the shell layer is optimized. .. If at least one of the first target temperature, the second target temperature, and the rate of temperature increase is changed, the above-described temperature increase time (more specifically, after changing the liquidity of the shell forming liquid) The temperature rise time) can be optimized. For example, the rate of temperature increase is preferably a rate selected from a rate range of 0.1° C./min or more and 3.0° C./min or less, and more preferably 0.1° C./min or more and 1.0° C./min. It is a speed selected from the following speed ranges. The first target temperature is preferably a temperature selected from a temperature range of 60°C or higher and 70°C or lower, for example. The difference between the first target temperature and the second target temperature is preferably 10°C or higher, more preferably 30°C or higher.

An example is given in which a suspension containing styrene-acrylic acid resin particles is used as the shell material, the temperature of the shell-forming liquid at the start of heating is 30° C., and the heating rate is 1° C./minute. .. 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 shell-forming liquid reaches 40°C. Further, it is considered that the shell material starts to be fixed on the surface of the toner core when the temperature of the shell-forming liquid reaches 60°C.

Preferably, the temperature of the shell forming liquid is maintained at the first target temperature for a predetermined time. When such heat retention treatment is performed, a reaction proceeds between the toner core and the shell material on the surface of the toner core. A shell layer is formed by bonding the toner core and the shell material. For example, the shell material is two-dimensionally continuous on the surface of the toner core to form a film (shell layer) having a granular feeling. Further, the shell material is completely melted on the surface of the toner core and cured in a film-like form, so that a film (shell layer) having no granular feeling is formed.

The obtained dispersion liquid of toner base particles is filtered to obtain wet cake-shaped toner base particles. The wet cake-shaped toner mother particles are washed and then dried. In this way, a powder containing a plurality of toner base particles is obtained.

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

[Examples of Materials Constituting Toner]
<Toner core>
In the toner core, the binder resin generally occupies most of the components (for example, 85% by mass or more). Therefore, it is considered that the properties of the binder resin have a great influence on the properties of the entire toner core. By using plural kinds of resins in combination as the binder resin, the properties of the binder resin (more specifically, hydroxyl value, acid value, Tg, Tm, etc.) can be adjusted. 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 be anionic, and when the binder resin has an amino group, the toner core is Tend to be cationic.

The toner core may further contain at least one of a colorant, a release agent, and a charge control agent, in addition to the binder resin. Hereinafter, they will be described in order.

(Binder resin)
As described above, the toner core preferably has the above-mentioned configurations X1 and X2. More preferably, the proportion of the second amorphous polyester resin in the binder resin contained in the toner core is 10% by mass or more. Thereby, the heat resistant storage stability of the toner can be sufficiently ensured.

The toner core may further contain a third non-crystalline polyester resin in addition to the first non-crystalline polyester resin and the second non-crystalline polyester resin. The softening point of the third non-crystalline polyester resin is preferably higher than that of the first non-crystalline polyester resin, and is preferably lower than that of the second non-crystalline polyester resin. For example, the third non-crystalline polyester resin is preferably a non-crystalline polyester resin having a softening point of 80° C. or higher and 95° C. or lower.

The toner core may further contain a crystalline polyester resin having a crystallinity index of 0.98 or more and 1.20 or less in addition to the first non-crystalline polyester resin and the second non-crystalline polyester resin. 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. Examples of the material for synthesizing the polyester resin include at least one of alcohol for synthesizing the polyester resin and carboxylic acid for synthesizing the polyester resin. In addition, with respect to the amorphous polyester resin, it is often impossible to measure a clear Mp.

A preferable example of the first non-crystalline polyester resin is a non-crystalline polyester resin containing bisphenol as an alcohol component and aromatic dicarboxylic acid and unsaturated dicarboxylic acid as an acid component. The bisphenol is preferably, for example, at least one of a bisphenol A ethylene oxide adduct and a bisphenol A propylene oxide adduct. The aromatic dicarboxylic acid is preferably, for example, terephthalic acid. The unsaturated dicarboxylic acid is preferably fumaric acid, for example.

Preferable examples of the second non-crystalline polyester resin include a dicarboxylic acid containing bisphenol as an alcohol component and having an alkyl group having 10 to 20 carbon atoms as an acid component, an unsaturated dicarboxylic acid, and a trivalent carboxylic acid. The non-crystalline polyester resin containing is mentioned. The bisphenol is preferably, for example, at least one of a bisphenol A ethylene oxide adduct and a bisphenol A propylene oxide adduct. The dicarboxylic acid having an alkyl group having 10 to 20 carbon atoms is preferably, for example, dodecylsuccinic acid having an alkyl group having 12 carbon atoms. The unsaturated dicarboxylic acid is preferably fumaric acid, for example. The trivalent carboxylic acid is preferably trimellitic acid, for example.

A preferred example of the third non-crystalline polyester resin is a non-crystalline polyester resin containing bisphenol as an alcohol component and aromatic dicarboxylic acid as an acid component but not unsaturated dicarboxylic acid. The bisphenol is preferably, for example, at least one of a bisphenol A ethylene oxide adduct and a bisphenol A propylene oxide adduct. The aromatic dicarboxylic acid is preferably, for example, terephthalic acid.

Suitable examples of the crystalline polyester resin having a crystallinity index of 0.98 or more and 1.20 or less include α,ω-alkanediol having 2 to 12 carbon atoms as an alcohol component and 4 or more carbon atoms as an acid component. A crystalline polyester resin containing 14 or less aliphatic dicarboxylic acid may be mentioned. The α,ω-alkanediol having 2 to 12 carbon atoms is preferably, for example, 1,4-butanediol having 4 carbon atoms. The aliphatic dicarboxylic acid having 4 to 14 carbon atoms is preferably fumaric acid having 4 carbon atoms.

(Colorant)
As the colorant, a known pigment or dye can be used according to the color of the positively chargeable toner. In order to form a high quality image using the positively chargeable 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. Examples of black colorants include carbon black. Further, the black colorant may be a colorant toned in black by using a yellow colorant, a magenta colorant, and a cyan colorant.

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

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. Bat yellow can be 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 magenta colorants 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 used.

As the cyan colorant, for example, one or more compounds selected from the group consisting of copper phthalocyanine compounds, anthraquinone compounds, and basic dye lake compounds 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 used.

(Release agent)
The release agent is used, for example, for the purpose of improving the fixing property or the high temperature offset resistance of the positively chargeable toner. In order to enhance the cationic property of the toner core, it is preferable to prepare the toner core by using a wax having cationic property.

The release agent is, for example, an aliphatic hydrocarbon wax, a vegetable wax, an animal wax, a mineral wax, a wax containing a fatty acid ester as a main component, or a wax obtained by partially or completely deoxidizing a fatty acid ester. Is preferred. The aliphatic hydrocarbon wax is preferably low molecular weight polyethylene, low molecular weight polypropylene, polyolefin copolymer, polyolefin wax, microcrystalline wax, paraffin wax, or Fischer-Tropsch wax. These oxides are also included in the aliphatic hydrocarbon wax. The vegetable wax is preferably candelilla wax, carnauba wax, wood wax, jojoba wax, or rice wax, for example. The animal wax is preferably, for example, beeswax, lanolin, or whale wax. The mineral wax is preferably, for example, ozokerite, ceresin, or petrolatum. The wax containing a fatty acid ester as a main component is preferably montanic acid ester wax or caster wax. One type of wax may be used alone, or a plurality of types of wax may be used in combination.

A compatibilizing agent may be added to the toner core in order to improve the compatibility between the binder resin and the release agent.

(Charge control agent)
The charge control agent is used, for example, for the purpose of improving charge stability or charge rising characteristics of the positively chargeable toner. The charge rising characteristic of the positively chargeable toner is an index of whether or not the positively chargeable toner can be charged to a predetermined charge level in a short time. The cationicity of the toner core can be enhanced by incorporating a positively chargeable charge control agent into the toner core. By including a negatively chargeable charge control agent in the toner core, the anionic property of the toner core can be enhanced.

<Shell layer>
The shell layer preferably contains a thermoplastic resin. This makes it possible to achieve both heat-resistant storage stability and low-temperature fixability of the toner. When the shell layer contains a styrene-acrylic acid-based resin, it is possible to improve both the heat-resistant storage stability of the toner and the low-temperature fixability, and to improve the charging stability of the toner. Therefore, the shell layer preferably contains a styrene-acrylic acid resin. Further, the resin contained in the shell layer has at least one alcoholic hydroxyl group derived from 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 2-hydroxyethyl methacrylate, or 2-hydroxypropyl methacrylate. When the unit is included, the quality of the shell layer film can be improved.

The styrene-acrylic acid resin is a copolymer of one or more styrene monomers and one or more acrylic acid monomers. Preferable examples of the styrene-based monomer for synthesizing the styrene-acrylic acid-based resin include styrene, alkylstyrene, hydroxystyrene, and halogenated styrene. The alkyl styrene is preferably, for example, α-methyl styrene, m-methyl styrene, p-methyl styrene, p-ethyl styrene, or 4-tert-butyl styrene. The hydroxystyrene is preferably, for example, p-hydroxystyrene or m-hydroxystyrene. The halogenated styrene is preferably, for example, α-chlorostyrene, o-chlorostyrene, m-chlorostyrene, or p-chlorostyrene.

Preferable examples of the acrylic acid-based monomer for synthesizing the styrene-acrylic acid-based resin include, for example, (meth)acrylic acid, (meth)acrylamide, (meth)acrylonitrile, (meth)acrylic acid alkyl ester, or ( Examples include hydroxyalkyl esters of (meth)acrylic acid. Examples of alkyl (meth)acrylate include methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, iso-propyl (meth)acrylate, and n-(meth)acrylate. Butyl, iso-butyl (meth)acrylate, or 2-ethylhexyl (meth)acrylate is preferred. The hydroxyalkyl (meth)acrylate ester is, for example, 2-hydroxyethyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, or (meth)acrylic acid 4-ester. Hydroxybutyl is preferred.

<External additive>
Unlike the internal additive, the external additive does not exist inside the toner base particles but selectively exists only on the surface of the toner base particles (surface layer portion of the toner particles). The toner mother particles and the external additive particles do not chemically react with each other, and are physically bonded rather than chemically. The bond strength between the toner base particles and the external additive particles can be adjusted by the stirring conditions, the particle diameter of the external additive particles, the shape of the external additive particles, the surface state of the external additive particles, and the like. The stirring conditions include, for example, stirring time and stirring rotation speed.

In order to fully exhibit the function of the external additive while suppressing the detachment of the external additive particles from the toner particles, the amount of the external additive is 0.5 parts by mass with respect to 100 parts by mass of the toner base particles. It is preferably from 10 parts by mass to 10 parts by mass. When the toner particles include two or more kinds of external additive particles, the total amount of the external additive particles is 0.5 parts by mass or more and 10 parts by mass or less with respect to 100 parts by mass of the toner mother particles. preferable.

The external additive particles are preferably inorganic particles. More preferably, the external additive particles are silica particles or metal oxide particles. Here, the metal oxide is preferably alumina, titanium oxide, magnesium oxide, zinc oxide, strontium titanate, or barium titanate. However, particles of an organic acid compound such as a fatty acid metal salt or resin particles may be used as the external additive particles. The fatty acid metal salt is preferably zinc stearate, for example. Further, as the external additive particles, composite particles which are composites of plural kinds of materials may be used. One type of external additive particles may be used alone, or a plurality of types of external additive particles may be used in combination.

In order to improve the fluidity of the toner, it is preferable to use, as the external additive particles, inorganic particles (powder) having a number average primary particle diameter of 5 nm or more and 30 nm or less. Further, in order to make the external additive function as a spacer between the toner particles to improve the heat resistant storage stability of the toner, resin particles (powder) having a number average primary particle diameter of 50 nm or more and 100 nm or less are used as the external additive particles. Is preferably used.

Examples of the present invention will be described. Table 1 shows the configurations of the toners T-1 to T-10 according to the examples or the comparative examples. In Table 1, the "relative permittivity" indicates the relative permittivity calculated by the method described in <Calculating relative permittivity> described later. In the "particle diameter", the number average primary particle diameter of fine particles is described. The "content" is the amount of fine particles contained in 100 parts by mass of the toner core. “Number of base recesses” indicates the number of base recesses per unit area of the surface area of the toner core. For toner T-8, a toner was manufactured without using fine particles.

Table 2 shows manufacturing conditions of the toners T-1 to T-10 according to the examples or the comparative examples. The "temperature" indicates the temperature in the flask containing the shell-forming liquid. In "pH", the pH of the shell-forming liquid is noted. As the toner T-9, the toner was manufactured without changing the liquid property of the shell forming liquid.

In the following, first, a method of manufacturing the toner according to the example or the comparative example (more specifically, each of the toners T-1 to T-10) will be described. Next, a method for measuring the physical property values of the toner particles contained in each of the toners according to the examples or comparative examples will be described. Next, a toner evaluation method and evaluation results according to the examples or comparative examples will be described. In the evaluation in which an error occurs, a considerable number of measurement values with which the error is sufficiently small was obtained, and the arithmetic mean of the obtained measurement values was used as the evaluation value. Further, 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. The relative permittivity was measured by the following method.

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

<Method of measuring Tm>
A sample (for example, a resin) is set on a high-performance flow tester (“CFT-500D” manufactured by Shimadzu Corporation), and the die pore diameter is 1 mm, the plunger load is 20 kg/cm ² , and the heating rate is 6° C./min. Then, 1 cm ³ of the sample was melted and flowed out, and the S-shaped curve (horizontal axis: temperature, vertical axis: stroke) of the sample was obtained. The Tm (softening point) of the sample was read from the obtained S-shaped curve. In the obtained S-curve, if the maximum value of the stroke is S ₁ and the stroke value of the low temperature side baseline is S ₂ , the value of the stroke in the S-curve is “(S ₁ +S ₂ )/2”. The temperature at which is equal to the Tm (softening point) of the sample.

<Calculation method of relative permittivity>
The relative dielectric constant of the fine particles was obtained using a rotary rheometer (“ARES-G2” manufactured by TA Instruments) and an LCR meter (“4284A Precision LCR meter” manufactured by Keysight Technologies, Inc.). Specifically, first, a pair of electrodes was attached to the rotary rheometer. Next, the sample (more specifically, fine particles) was sandwiched between a pair of electrodes. Then, the distance between the electrodes was adjusted to a predetermined length while a predetermined load was applied to the sample. Then, the capacitance of the sample was measured using an LCR meter. At this time, in the LCR meter, the applied voltage was 1.0 V and the frequency was 1.0 kHz. Then, the relative permittivity ε _r [unit: F/m] of the sample was calculated using the following formula. In the formula below, the dielectric constant ε _{v in} vacuum was set to 5.854×10 ⁻¹² [unit: F/m].
ε _r =(L×C)÷(S×ε _v )
ε _r : relative permittivity of sample [unit: F/m]
L: Distance between electrodes [unit: m]
S: Electrode area [unit: m ² ]
C: Measured capacitance of sample [unit: F/m]
ε _v : Dielectric constant of vacuum [unit: F/m]

[Production Method of Toner T-1]
(Preparation of toner core)
First, the mixture Y1 was prepared. Specifically, using an FM mixer (manufactured by Nippon Coke Industry Co., Ltd.), 92.5 parts by mass of a low-viscosity amorphous polyester resin (Tg=38° C., Tm=65° C.) and 7.5 parts by mass of titanium. Barium acid particles (“1401GC” manufactured by SkySpring Nanomaterials) were mixed at a rotation speed of 2400 rpm. Using a twin-screw extruder (“PCM-30” manufactured by Ikegai Co., Ltd.), the obtained mixture was supplied at a material feed rate of 5 kg/hour, a shaft rotation speed of 160 rpm, and a set temperature range (cylinder temperature range) of 40° C. or higher and 80° C. or higher. Melt kneading was carried out under the condition of not higher than 0°C. The obtained melt-kneaded product was cooled, and the cooled melt-kneaded product was roughly pulverized by using a pulverizer (former Toa Kikai Seisakusho “Rotoplex 16/8 type”). Thus, the mixture Y1 was obtained.

Next, using an FM mixer (manufactured by Nippon Coke Industry Co., Ltd.), 66 parts by mass of the mixture Y1, 9 parts by mass of a medium viscosity amorphous polyester resin (Tg=53° C., Tm=84° C.), 12 High-viscosity non-crystalline polyester resin (Tg=71° C., Tm=120° C.), 5 parts by weight of carnauba wax (“Carnauba wax No. 1” manufactured by Kato Hiroyuki Co., Ltd.), and 8 parts by weight of coloring. The agent (“KET BLUE 111” manufactured by DIC Corporation, phthalocyanine blue) was mixed at a rotation speed of 2400 rpm. Using a twin-screw extruder (“PCM-30” manufactured by Ikegai Co., Ltd.), the obtained mixture was supplied at a material feed rate of 5 kg/hour, a shaft rotation speed of 160 rpm, and a set temperature range (cylinder temperature range) of 80° C. or higher and 130° C. Melt kneading was performed under the following conditions. The obtained melt-kneaded product was cooled, and the cooled melt-kneaded product was roughly pulverized by using a pulverizer (former Toa Kikai Seisakusho “Rotoplex 16/8 type”). The resulting coarsely pulverized product was finely pulverized using a jet mill (“Ultrasonic Jet Mill I type” manufactured by Nippon Pneumatic Mfg. Co., Ltd.). The obtained finely pulverized product was classified using a classifier (“Elbow Jet EJ-LABO type” manufactured by Nittetsu Mining Co., Ltd.). Thus, 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 barium titanate particles per 100 parts by mass of the toner core.

(Formation of shell layer)
First, a shell material was prepared. Specifically, a three-necked flask (capacity: 1 L) equipped with a thermometer and a stirring blade was set in a water bath. In the flask, 875 g of ion-exchanged water (temperature: 30° C.) and 75 g of anionic surfactant (“Latemul (registered trademark) WX” manufactured by Kao Corporation, component: sodium polyoxyethylene alkyl ether sulfate, solid content concentration: 26% by mass) was added. The temperature inside the flask was raised to 80° C. using a water bath while stirring the contents of the flask. While maintaining the temperature in the flask at 80° C., each of the two kinds of liquids was dropped into the flask over 5 hours while stirring the contents of the flask. The two types of liquid contained the first liquid and the second liquid. The first liquid was a mixed liquid of 17 g of styrene and 3 g of butyl acrylate. The second liquid was a solution prepared by dissolving 0.5 g of potassium persulfate in 30 g of ion-exchanged water.

While maintaining the temperature in the flask at 80° C., the contents of the flask were further stirred for 2 hours to allow the polymerization reaction of the contents of the flask to proceed sufficiently. As a result, a suspension (solid content concentration: 3.6% by mass) containing particles (resin particles) made of a polymer of a hydrophobic monomer was obtained. The resin particles contained in the obtained suspension had a number average particle diameter of 32 nm and a Tg of 71°C. In this way, a shell material was obtained.

Next, a shell forming liquid was prepared. Specifically, a three-necked flask (capacity: 1 L) equipped with a thermometer and a stirring blade was set in a water bath, and 300 g of ion-exchanged water was put in the flask. Then, the temperature in the flask was kept at 30° C. using a water bath. Then, diluted hydrochloric acid was added to the flask to adjust the pH of the contents of the flask to 4. Then, 30 g of shell material (suspension prepared by the above procedure) was added to the flask. In this way, a dispersion liquid of the shell material was obtained.

To the obtained dispersion liquid of the shell material, 300 g of the toner core (the toner core manufactured by the above procedure) was added. Then, the contents of the flask were stirred at a rotation speed of 200 rpm for 1 hour. Then, 300 g of ion-exchanged water was further added to the flask. In this way, a shell-forming liquid was obtained.

Then, the temperature of the shell forming liquid was raised (temperature rising process). Specifically, while stirring the flask contents at a rotation speed of 100 rpm, the flask contents were heated at a temperature rising rate of 1.0° C./min until the temperature inside the flask reached 70° C. The temperature of the flask contents was 30° C. and the pH of the flask contents was 4 at the start of temperature increase.

When the temperature in the flask reached 35° C. during the temperature rise, an aqueous sodium hydroxide solution was added to the flask to change the pH of the contents of the flask from 4 to 9. Even during the addition of the aqueous sodium hydroxide solution and after the pH of the flask contents was changed to 9, the temperature rising process was not stopped and the temperature of the shell-forming liquid was raised to 70°C.

When the temperature of the flask contents reached 70°C, the flask contents were further stirred for 1 hour at a rotation speed of 100 rpm while maintaining the temperature of the flask contents at 70°C. Then, the contents of the flask were cooled to room temperature (about 25°C). In this way, a dispersion liquid containing toner mother particles was obtained.

(Washing)
The obtained dispersion liquid of toner mother particles was filtered (solid-liquid separation) using a Buchner funnel. In this way, wet cake-shaped toner mother particles were obtained. The obtained wet cake-shaped toner mother particles were redispersed in ion-exchanged water. Then, the dispersion and filtration were repeated 5 times to wash the toner mother particles.

(Dry)
The toner mother particles were dispersed in an ethanol aqueous solution (concentration: 50% by mass). In this way, a slurry was obtained. The toner base particles in the slurry were dried under the conditions of a hot air temperature of 45° C. and a blower air flow rate of 2 m ³ /min using a continuous surface modification device (“Courtmizer (registered trademark)” manufactured by Freund Corporation). .. In this way, toner mother particles (powder) were obtained.

(External processing)
Using an FM mixer (manufactured by Nippon Coke Industry Co., Ltd., capacity: 10 L), 100 parts by mass of toner mother particles (toner mother particles obtained by the above-mentioned procedure) and 2.5 parts by mass of hydrophobic silica particles ( "AEROSIL (registered trademark) RA-200H" manufactured by Nippon Aerosil Co., Ltd.) and 1.5 parts by mass of conductive titanium oxide particles ("EC-100" manufactured by Titanium Industry Co., Ltd.) were mixed for 5 minutes. The obtained powder was sieved using a 200 mesh (mesh opening 75 μm) sieve. In this way, a toner (toner T-1) containing a large number of toner particles was obtained.

In the toner particles contained in Toner T-1, a shell layer having a thickness of 20 nm was formed in the surface area of the toner core. In addition, the relative dielectric constant of the conductive titanium oxide particles (“EC-100” manufactured by Titanium Industry Co., Ltd.) was calculated by the method described in <Calculation method of relative dielectric constant> above. The relative dielectric constant of the conductive titanium oxide particles (“EC-100” manufactured by Titanium Industry Co., Ltd.) was calculated to be 110.

[Method of Manufacturing Toner T-2]
Toner T-2 was manufactured according to the manufacturing method of toner T-1 except that the mixture Y1 was manufactured using strontium titanate particles (“NP-SRTIO3” manufactured by EM Japan Co., Ltd.). The obtained toner core contained 5 parts by mass of strontium titanate particles per 100 parts by mass of the toner core. Further, in the toner particles contained in Toner T-2, the shell layer having a thickness of 20 nm was formed in the surface region of the toner core.

[Manufacturing Method of Toner T-3]
Toner T-3 was manufactured according to the manufacturing method of toner T-1, except that the mixture Y1 was manufactured using titanium dioxide particles ("NP-TIO2-11" manufactured by EM Japan Co., Ltd.). The obtained toner core contained 5 parts by mass of titanium dioxide particles per 100 parts by mass of the toner core. Further, in the toner particles contained in Toner T-3, the shell layer having a thickness of 20 nm was formed in the surface region of the toner core.

[Manufacturing Method of Toner T-4]
Toner T-4 was manufactured according to the manufacturing method of toner T-1 except that the blending amount of barium titanate particles was changed to 15 parts by mass. In the obtained toner core, 10 parts by mass of barium titanate particles were contained with respect to 100 parts by mass of the toner core. Further, in the toner particles contained in Toner T-4, the shell layer having a thickness of 20 nm was formed in the surface region of the toner core.

[Manufacturing Method of Toner T-5]
Toner T-5 was manufactured according to the manufacturing method of Toner T-1 except that the compounding amount of barium titanate particles was changed to 1.5 parts by mass. In the obtained toner core, 1 part by mass of barium titanate particles was contained with respect to 100 parts by mass of the toner core. Further, in the toner particles contained in Toner T-5, a shell layer having a thickness of 20 nm was formed in the surface area of the toner core.

[Manufacturing Method of Toner T-6]
Toner T-6 was manufactured according to the manufacturing method of toner T-3 except that the compounding amount of titanium dioxide particles was changed to 1.5 parts by mass. The obtained toner core contained 1 part by mass of titanium dioxide particles per 100 parts by mass of the toner core. Further, in the toner particles contained in Toner T-6, the shell layer having a thickness of 20 nm was formed in the surface region of the toner core.

[Manufacturing Method of Toner T-7]
In the temperature raising process, the temperature raising rate was changed to 0.3° C./min, and the target temperature was changed to 60° C. Except for this, Toner T-7 was manufactured according to the manufacturing method of Toner T-1. The obtained toner core contained 5 parts by mass of barium titanate particles per 100 parts by mass of the toner core. Further, in the toner particles contained in Toner T-7, the shell layer having a thickness of 20 nm was formed in the surface area of the toner core.

[Manufacturing Method of Toner T-8]
Toner T-8 was manufactured according to the manufacturing method of Toner T-1 except that the toner core was manufactured without using barium titanate particles. In the toner particles contained in Toner T-8, a shell layer having a thickness of 20 nm was formed in the surface area of the toner core.

[Production Method of Toner T-9]
Toner T-9 was manufactured according to the manufacturing method of Toner T-1 except that the temperature raising step was performed without adding the aqueous sodium hydroxide solution. The obtained toner core contained 5 parts by mass of barium titanate particles per 100 parts by mass of the toner core. Further, in the toner particles contained in Toner T-9, the shell layer having a thickness of 20 nm was formed in the surface region of the toner core.

[Manufacturing Method of Toner T-10]
Toner T-10 was manufactured according to the manufacturing method of Toner T-1 except that the mixture Y1 was manufactured using silica particles (“Seahoster (registered trademark) KE-P10” manufactured by Nippon Shokubai Co., Ltd.). The obtained toner core contained 5 parts by mass of silica particles with respect to 100 parts by mass of the toner core. Further, in the toner particles contained in Toner T-10, the shell layer having a thickness of 20 nm was formed in the surface region of the toner core.

[Method of measuring physical properties of toner particles]
(Measurement of the number of base recesses per unit area of the surface area of the toner core)
With respect to the obtained toner (more specifically, each of the toners T-1 to T-10), the number of base recesses per unit area of the surface area of the toner core was measured. The measurement target was the toner mother particles contained in each of the toners. That is, the number of base recesses per unit area of the surface area of the toner core was determined before the external addition treatment. Specifically, a field emission scanning electron microscope (FE-SEM) ("JSM-7600F" manufactured by JEOL Ltd.) was used to observe the entire surface of the toner mother particles. 20 toner mother particles were observed for one sample. Then, the number of base recesses per unit area of the surface area of the toner core (number average value) was determined. The results are shown in Table 1.

(Confirmation of presence of fine particles in toner core)
Regarding the obtained toner (more specifically, each of the toners T-1 to T-10), the presence state of fine particles in the toner core was examined. The measurement target was the toner mother particles contained in each of the toners. Specifically, using a transmission electron microscope (“H-7100FA” manufactured by Hitachi High-Technologies Corporation), a cross-sectional TEM photograph of the toner mother particles was observed.

It was confirmed that in each of the toners T-1 to T-7 and T-10, the fine particles were preferentially present in the first area over the second area. More specifically, it was confirmed that the ratio of the total area occupied by the high dielectric constant domain in the first region was higher than the ratio of the total area occupied by the high dielectric constant domain in the second region. More specifically, it was confirmed that at least one high-permittivity domain was present in the first region in more than half of the underlying recesses. On the other hand, in toner T-8, fine particles were not confirmed. Further, in the toner T-9, the base recessed portion was not confirmed. Therefore, it could not be confirmed that the fine particles preferentially exist in the first region.

(Measurement of shell layer thickness)
With respect to the obtained toner (more specifically, each of toners T-1 to T-10), the thickness of the shell layer was measured. The measurement target was the toner mother particles contained in each of the toners. Specifically, first, a transmission electron microscope (“H-7100FA” manufactured by Hitachi High-Technologies Corporation) was used to take a TEM photograph of a cross section of the toner mother particles. Next, a TEM photograph of a cross section of the obtained toner mother particles was analyzed using image analysis software (“WinROOF” manufactured by Mitani Corporation). Specifically, two straight lines that are orthogonal to each other at substantially the center of the cross section of the toner mother particles are drawn. For 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 measured in this way was taken as the thickness of the shell layer included in one toner mother particle. The thickness of the shell layer was measured for a plurality of toner base particles, and the average value of the thickness of the shell layer included in the plurality of toner base particles (measurement target) was determined. 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 TEM photograph of the cross section of the toner mother particle, the TEM photograph of the cross section of the toner mother particle is taken by an electron energy loss spectroscopy (EELS) detector (“GIF TRIDIEEM” manufactured by Gatan Co., Ltd.). (Registered trademark)” and image analysis software (“WinROOF” manufactured by Mitani Shoji Co., Ltd.). As a result, the boundary between the toner core and the shell layer became clear in the TEM photograph of the cross section of the toner mother particles.

[Toner evaluation method]
<Preparation of evaluation device>
An evaluation device was prepared by the method described below. Specifically, first, using a powder mixer ("Rocking Mixer (registered trademark)" manufactured by Aichi Electric Co., Ltd.), 9 parts by mass of toner (more specifically, toners T-1 to T-) over 30 minutes. -10 each) and 100 parts by mass of a ferrite carrier ("F-150" manufactured by Powdertech Co., Ltd.) were mixed. In this way, a two-component developer was obtained.

Next, the toner (more specifically, each of the toners T-1 to T-10) was supplied to the toner container of the multi-function peripheral (“Taskalfa5551ci” manufactured by Kyocera Document Solutions Co., Ltd.). Further, the two-component developer obtained by the above-mentioned method was supplied to the developing device of the composite machine. After that, the installation operation was performed. In this way, the evaluation device was prepared.

<Evaluation of fogging density>
First, a printing durability test was conducted using an evaluation device in an environment of a temperature of 25° C. and a humidity of 50% RH. In the printing durability test, 50,000 solid images were continuously printed on A4 size plain paper under the following process conditions.
(Process condition)
Development bias voltage: The development bias voltage was adjusted so that the applied toner amount was 0.4 mg/cm ² .
・Line speed: 200 mm/sec ・Fixing temperature: 160°C

Next, a sample image was printed on A4 size plain paper using an evaluation device. The sample image included a solid image part and a blank part (a region without printing). After that, the reflection density of the blank part of the sample image was measured using a color reflection densitometer (“R710” manufactured by Ihara Electronics Co., Ltd.). Then, the fog density (FD) was calculated based on the following formula.
FD=(reflection density of blank area)-(reflection density of unprinted paper)

The evaluation criteria are as shown below. The evaluation results are shown in Table 3.
Good (◯): Fog density (FD) is 0.010 or less.
Poor (x): Fogging density (FD) exceeds 0.010.

<Evaluation of charge amount and spent amount>
First, the two-component developer obtained by the method described above (more specifically, the two-component developer containing each of the toners T-1 to T-10) was placed in a polyethylene container (capacity: 20 mL). It was The contents of the container were stirred for 30 minutes using a rocking mixer in an environment of a temperature of 25° C. and a humidity of 50% RH. After that, a small amount of the two-component developer was taken out from the polyethylene container.

The charge amount of the toner was measured by using the taken-out two-component developer as an evaluation target. Specifically, in a measuring cell of a Q/m meter (“MODEL 210HS-1” manufactured by Trek), 0.10 g of an object to be evaluated (more specifically, a two-component developer taken out from a polyethylene container) was put. It was Only the toner of the evaluation targets was sucked through the sieve (wire mesh) for 10 seconds. Then, the charge amount of the toner [unit: μC/g] was calculated based on the following formula. In this way, the initial charge amount was calculated.
Toner charge amount [unit: μC/g]=total amount of electricity of sucked toner [unit: μC]/mass of sucked toner [unit: g]

Further, among the evaluation targets, the samples that were not sucked and remained on the sieve were subjected to fluorescent X-ray analysis. Specifically, 1.5 g of a sample (more specifically, a sample of the evaluation target that was not sucked and remained on the sieve) was pressure-molded under the conditions of a pressure of 20 MPa and a pressing time of 3 seconds. In this way, a cylindrical pellet having a diameter of 30 mm was produced. The columnar pellets thus obtained were subjected to fluorescent X-ray analysis under the analysis conditions shown below. In this way, a fluorescent X-ray spectrum [horizontal axis: energy, vertical axis: intensity (number of photons)] was obtained. The fluorescent X-ray spectrum contained a peak derived from elemental silicon. Then, the peak intensity of the peak derived from the silicon element was obtained using the fluorescent X-ray spectrum. In this way, the initial peak intensity was obtained.
(Analysis conditions)
・Analyzer: Scanning fluorescent X-ray analyzer ("ZSX" manufactured by Rigaku Corporation)
・X-ray tube (X-ray source): Rh (rhodium)
・Excitation conditions: tube voltage 50 kV, tube current 50 mA
・Measurement area (X-ray irradiation range): Diameter 30 mm
・Measurement element: Si (silicon)

The particle size of the carrier particles was larger than the particle size of the toner particles. Therefore, carrier particles were considered as the sample that remained on the sieve without being sucked among the evaluation targets. The obtained fluorescent X-ray spectrum contained a peak derived from silicon element, but the carrier particles did not contain silicon element. However, the toner particles contained hydrophobic silica particles as external additive particles. From these, it is considered that the peak derived from the elemental silicon originates from the hydrophobic silica particles detached from the surface of the toner mother particles and attached to the surface of the carrier particles. That is, it is considered that the peak intensity of the peak derived from the silicon element corresponds to the amount of the hydrophobic silica particles attached to the surface of the carrier particles (hereinafter, referred to as “spent amount”).

The content (number) of conductive titanium oxide particles per unit number of toner particles is overwhelmingly smaller than the content (number) of hydrophobic silica particles per unit number of toner particles. Therefore, the present inventor believes that the number of detached particles can be approximated by the amount of spent.

Next, a printing durability test was conducted under the conditions described in <Evaluation of fog density> above. Then, a small amount of the two-component developer was taken out from the developing device of the evaluation device. The charge amount of the toner was measured by using the taken-out two-component developer as an evaluation target. The method of measuring the charge amount of the toner was as described above. In this way, the amount of charge after printing was calculated.

Further, a fluorescent X-ray analysis was performed on the sample, which was not sucked and remained on the sieve when the charge amount of the toner was measured, under the above-described analysis conditions. Using the obtained fluorescent X-ray spectrum, the peak intensity of the peak derived from silicon element was determined. In this way, the peak intensity after printing was determined.

The variation rate (unit: %) of the charge amount was calculated based on the following formula.
Change rate of charge amount (unit: %)=100×(initial charge amount−charge amount after printing endurance)/initial charge amount Evaluation criteria are as follows. The evaluation results are shown in Table 3.
Good (∘): The variation rate of the charge amount is 15% or less.
Poor (x): The variation rate of the charge amount exceeds 15%.

Further, the rate of change of the spent amount (unit: %) was calculated based on the following formula.
Spent amount fluctuation rate (unit: %)=100×(initial peak strength-peak strength after printing)/initial peak strength Evaluation criteria are as follows. The evaluation results are shown in Table 3.
Good (∘): The fluctuation rate of the peak intensity is 15% or less.
Bad (x): The fluctuation rate of the peak intensity is more than 15%.

[Toner evaluation results]
Table 3 shows the evaluation results of the toner.

Toners T-1 to T-7 (more specifically, toners according to Examples 1 to 7) each had the above-described basic configuration. Specifically, each of the toner particles was provided with a toner mother particle and an external additive attached to the surface of the toner mother particle. The toner mother particles each had a toner core and a shell layer covering 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 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 mother particles. The number of the first recesses per unit area of the surface area of the toner core was 0.30/μm ² or more. The cross-sectional area of the toner core was composed of a first area, which is an area within 500 nm from the inner area of the first recess, and a second area, which is an area other than the first area. The toner cores each had multiple high dielectric constant domains. Each of the high dielectric constant domains contained high dielectric constant particles having a relative dielectric constant of 100 or more. The ratio of the total area occupied by the high dielectric constant domain in the first region was higher than the ratio of the total area occupied by the high dielectric constant domain in the second region.

As shown in Table 3, with toners T-1 to T-7, it was possible to prevent fog from occurring in the formed images. Further, the variation rate of the toner charge amount can be suppressed to a low level, and the variation rate of the spent amount can be suppressed to a low level.

On the other hand, each of the toners T-8 to T-10 (toner according to Comparative Example 1) did not have the above-described basic configuration. Specifically, Toner T-8 did not contain high dielectric constant particles. Then, with toner T-8, fogging occurred in the formed image. Further, the variation rate of the toner charge amount cannot be kept low, and the variation rate of the spent amount cannot be kept low.

Further, in the toner T-9, the base concave portion and the surface concave portion were not formed. Then, with toner T-9, fogging occurred in the formed image. Further, the variation rate of the toner charge amount cannot be kept low, and the variation rate of the spent amount cannot be kept low.

Further, Toner T-10 did not contain high dielectric constant particles. Then, with toner T-10, fogging occurred in the formed image. Further, the variation rate of the toner charge amount cannot be kept low, and the variation rate of the spent amount cannot be kept low.

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

10 Toner mother particles 11 Toner core 12 Shell layer 12A Surface 13 Interfaces 15a to 15d Inorganic particles H11 to H14 Underlying recesses H22, H23 Surface recesses

Claims (5)

An electrostatic latent image developing toner containing a plurality of toner particles,
The toner particles each include a toner mother particle and an external additive attached to the surface of the toner mother particle,
The toner mother particles each include 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 an inner region of the first recess and an outer region of the first recess in a surface region of the toner core,
A second recess corresponding to the first recess is formed on the surface of the toner mother particle,
The number of the first concave portions per unit area of the surface region of the toner core is 0.30 pieces/μm ² or more and 1.00 pieces/μm ² or less ,
The depth of the first recess is 100 nm or more and 3 μm or less,
The cross-sectional area of the toner core is composed of a first area which is an area within 500 nm from an inner area of the first recess and a second area which is an area other than the first area.
The toner cores each have a plurality of high dielectric constant domains,
Each of the high dielectric constant domains includes high dielectric constant particles having a relative dielectric constant of 100 or more,
Each of the toner cores contains a first non-crystalline polyester resin and a second non-crystalline polyester resin,
The softening point of the second non-crystalline polyester resin is higher than the softening point of the first non-crystalline polyester resin,
The high dielectric constant domain contained in the second region contains only the high dielectric constant particles and the first amorphous polyester resin,
The toner for developing an electrostatic latent image, wherein the ratio of the total area occupied by the high dielectric constant domain in the first region is higher than the ratio of the total area occupied by the high dielectric constant domain in the second region. The external additive contains silica particles and external additive particles that are not silica particles,
The electrostatic latent image developing toner according to claim 1, wherein the relative dielectric constant of the external additive particles that are not the silica particles is less than the relative dielectric constant of the high dielectric constant particles. 3. The electrostatic latent image developing toner according to claim 1, wherein the high dielectric constant particles are titanium dioxide particles, strontium titanate particles, or barium titanate particles, respectively. The toner core is a first non-crystalline polyester resin softening point of 70 ° C. or less, softening point and said at 100 ° C. or more second non-crystalline polyester resin, containing,
The electrostatic latent image according to claim 1, wherein a proportion of the first amorphous polyester resin in the resin contained in the toner core is 50% by mass or more and 80% by mass or less. Toner for development. A step of producing toner mother particles,
A step of mixing the toner mother particles and the external additive particles,
Including
The step of producing the toner mother particles includes
A step of producing a toner core,
Forming a shell layer on the surface of the toner core;
Including
The step of producing the toner core includes
Mixing the first non-crystalline polyester resin and high dielectric constant particles and melt-kneading to obtain a mixture in which the high dielectric constant particles are present in a state of being dispersed in the first non-crystalline polyester resin;
Melt-kneading a toner core material containing the mixture and a second amorphous polyester resin to obtain a melt-kneaded product;
Pulverizing the melt-kneaded product to obtain a pulverized product containing a plurality of particles,
Including
The step of forming the shell layer includes
Preparing a liquid containing the toner core and the shell material and having a pH of 6 or less;
A temperature raising step of raising the temperature of the liquid to a first target temperature;
Changing the pH of the liquid to 8 or more when the temperature of the liquid reaches the second target temperature in the temperature raising step,
Including
A plurality of first recesses are formed on the surface of the toner core,
The shell layer exists in an inner region of the first recess and an outer region of the first recess in a surface region of the toner core,
A second recess corresponding to the first recess is formed on the surface of the toner mother particle,
The number of the first concave portions per unit area of the surface region of the toner core is 0.30 pieces/μm ² or more and 1.00 pieces/μm ² or less,
The depth of the first recess is 100 nm or more and 3 μm or less,
The softening point of the second non-crystalline polyester resin is higher than the softening point of the first non-crystalline polyester resin,
The relative permittivity of the high dielectric constant particles is 100 or more,
The first target temperature is a temperature higher than the softening point of the first non-crystalline polyester resin and lower than the softening point of the second non-crystalline polyester resin,
The method for producing a toner for developing an electrostatic latent image, wherein the second target temperature is lower than the softening point of the first amorphous polyester resin.

Images