WO2017183364A1 - Toner for electrostatic latent image development and method for producing same - Google Patents

Abstract

This toner for electrostatic latent image development contains a plurality of toner particles, each of which comprises a toner core and a shell layer. The toner core contains a polyester resin. The shell layer contains a resin that is configured only of one or more kinds of repeating units that have no hydroxyl group. The ratio of the area of the surface region of the toner core covered by the shell layer is from 60% to 80% (inclusive). The amount of hydrogen ions present on the surfaces of the toner particles is from 5.0 × 10^-11 mol to 5.0 × 10^-10 mol (inclusive) per 1 g of the toner.

Description

Toner for developing electrostatic latent image and method for producing the same

The present invention relates to an electrostatic latent image developing toner and a manufacturing method thereof, and more particularly to a capsule toner and a manufacturing method thereof.

Patent Document 1 discloses a technique for improving the chargeability of toner by using conductive inorganic fine particles as an internal or external additive for toner particles.

JP 2004-109716 A

However, when conductive inorganic fine particles are contained in the toner particles, there is a concern that the conductive inorganic fine particles may inhibit fixing of the toner or increase the cost. In addition, when conductive inorganic fine particles are adhered to the surface of the toner particles, the conductive inorganic fine particles are embedded from the surface of the toner particles into the interior due to long-term use of the image forming apparatus or continuous printing. There is a concern that this will be insufficient.

The present invention has been made in view of the above problems, and provides a toner for developing an electrostatic latent image that hardly resists charge attenuation under a high-temperature and high-humidity environment and is excellent in both heat storage stability and low-temperature fixability, and a method for producing the same. The purpose is to do.

The electrostatic latent image developing toner according to the present invention includes a plurality of toner particles each including a core and a shell layer covering the surface of the core. The core contains a polyester resin. The shell layer contains a resin composed only of one or more repeating units having no hydroxyl group. The area ratio of the area | region which the said shell layer covers among the surface area | regions of the said core is 60% or more and 80% or less. The amount of hydrogen ions present on the surface of the toner particles is 5.0 × 10 ⁻¹¹ mol or more and 5.0 × 10 ⁻¹⁰ mol or less per 1 g of the toner.

The method for producing a toner for developing an electrostatic latent image according to the present invention is a method for producing the toner for developing an electrostatic latent image according to the present invention. The method for producing a toner for developing an electrostatic latent image according to the present invention includes a preparation step and a surface treatment step.
In the preparation step, a toner core containing a polyester resin and a shell layer containing a resin composed of only one or more kinds of repeating units that cover the surface of the toner core at an area ratio of 60% to 80% and have no hydroxyl group And core-shell particles comprising:
In the surface treatment step, the core-shell particles are placed in a liquid containing alkali metal ions, and the liquid is kept at a temperature of 35 ° C. or higher and 45 ° C. or lower and a pH of 7.0 or higher and 11.0 or lower for 30 minutes or longer. Keep for less than 4 hours.

According to the present invention, it is possible to provide a toner for developing an electrostatic latent image and a method for producing the same, which are not easily attenuated in a high-temperature and high-humidity environment and are excellent in both heat storage stability and low-temperature fixability.

Embodiments of the present invention will be described in detail. Note that the evaluation results (values indicating the shape or physical properties) of the powder (more specifically, the toner core, toner base particles, external additive, toner, etc.) are averaged from the powder unless otherwise specified. This is the number average of the values measured for each of the average particles by selecting a significant number of such particles.

The number average particle diameter of the powder is the number average value of the equivalent circle diameter of primary particles (diameter of a circle having the same area as the projected area of the particles) measured using a microscope unless otherwise specified. It is. Moreover, the measured value of the volume median diameter (D ₅₀ ) of the powder is not specified, and the “Coulter Counter Multisizer 3” manufactured by Beckman Coulter Co., Ltd. is used. ) Measured based on. Further, the measured values of the acid value and the hydroxyl value are values measured according to “JIS (Japanese Industrial Standard) K0070-1992” unless otherwise specified. Moreover, each measured value of a number average molecular weight (Mn) and a mass average molecular weight (Mw) is the value measured using the gel permeation chromatography, if not prescribed | regulated at all.

Hereinafter, a compound and its derivatives may be generically named by adding “system” after the compound name. When the name of a polymer is expressed by adding “system” after the compound name, it means that the repeating unit of the polymer is derived from the compound or a derivative thereof. Acrylic and methacrylic are sometimes collectively referred to as “(meth) acrylic”. Further, acryloyl (CH ₂ ═CH—CO—) and methacryloyl (CH ₂ ═C (CH ₃ ) —CO—) may be collectively referred to as “(meth) acryloyl”. The subscript “n” of the repeating unit in each chemical formula independently indicates the number of repeating units (number of moles) of the repeating unit. Unless otherwise specified, n (number of repetitions) is arbitrary.

The toner according to this embodiment can be suitably used for developing an electrostatic latent image, for example, as a positively chargeable toner. The toner of the present exemplary embodiment is a powder that includes a plurality of toner particles (each having a configuration described later). The toner may be used as a one-component developer. Further, a two-component developer may be prepared by mixing a toner and a carrier using a mixing device (more specifically, a ball mill or the like). In order to form a high-quality image, it is preferable to use a ferrite carrier (ferrite particle powder) as a carrier. In order to form a high-quality image over a long period of time, it is preferable to use magnetic carrier particles including a carrier core and a resin layer covering the carrier core. In order to impart magnetism to the carrier particles, the carrier core may be formed of a magnetic material (for example, a ferromagnetic substance such as ferrite), or the carrier core may be formed of a resin in which magnetic particles are dispersed. Good. Further, magnetic particles may be dispersed in the resin layer covering the carrier core. In order to form a high-quality image, the amount of toner in the two-component developer is preferably 5 parts by mass or more and 15 parts by mass or less with respect to 100 parts by mass of the carrier. The positively chargeable toner contained in the two-component developer is positively charged by friction with the carrier.

The toner particles contained in the toner according to the present embodiment include a core (hereinafter referred to as a toner core) and a shell layer (capsule layer) that covers the surface of the toner core. The toner core contains a binder resin. The toner core may contain internal additives (for example, a colorant, a release agent, a charge control agent, and magnetic powder). An external additive may be attached to the surface of the shell layer (or the surface region of the toner core not covered with the shell layer). If not necessary, the external additive may be omitted. Hereinafter, the toner particles before the external additive adheres are referred to as toner mother particles. A material for forming the toner core is referred to as a toner core material. A material for forming the shell layer is referred to as a shell material.

The toner according to the present embodiment can be used for image formation in, for example, an electrophotographic apparatus (image forming apparatus). Hereinafter, an example of an image forming method using an electrophotographic apparatus will be described.

First, an image forming unit (for example, a charging device and an exposure device) of an electrophotographic apparatus forms an electrostatic latent image on a photosensitive member (for example, a surface layer portion of a photosensitive drum) based on image data. Subsequently, a developing device of the electrophotographic apparatus (specifically, a developing device in which a developer containing toner is set) supplies the toner to the photoconductor to develop the electrostatic latent image formed on the photoconductor. The toner is charged by friction with the carrier, the developing sleeve, or the blade in the developing device before being supplied to the photoreceptor. For example, a positively chargeable toner is positively charged. In the developing process, toner (specifically, charged toner) on a developing sleeve (for example, a surface layer portion of a developing roller in the developing device) disposed in the vicinity of the photosensitive member is supplied to the photosensitive member, and the supplied toner is By attaching to the electrostatic latent image on 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.

In the subsequent transfer process, after the transfer device of the electrophotographic apparatus transfers the toner image on the photosensitive member to an intermediate transfer member (for example, a transfer belt), the toner image on the intermediate transfer member is further transferred to a recording medium (for example, paper). Transcript to. Thereafter, a fixing device (fixing method: nip formed by a heating roller and a pressure roller) 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 superposing four color toner images of black, yellow, magenta, and cyan. The transfer method may be a direct transfer method in which the toner image on the photosensitive member is directly transferred to the recording medium without using the intermediate transfer member. The fixing method may be a belt fixing method.

The toner according to the present embodiment is an electrostatic latent image developing toner having the following configuration (hereinafter referred to as a basic configuration).

(Basic toner configuration)
The electrostatic latent image developing toner includes a plurality of toner particles including a toner core and a shell layer. The toner core contains a polyester resin. A shell layer contains resin comprised only by 1 or more types of repeating units which do not have a hydroxyl group. Of the surface area of the toner core, the area ratio of the area covered by the shell layer (hereinafter referred to as shell coverage) is 60% or more and 80% or less. The amount of hydrogen ions present on the surface of the toner particles is 5.0 × 10 ⁻¹¹ mol or more and 5.0 × 10 ⁻¹⁰ mol or less per 1 g of toner. In addition, the measuring method of the amount of hydrogen ions is the same method as the Example mentioned later, or its alternative method.

In the above basic structure, “having no hydroxyl group” means having no hydroxyl group (—OH) even in the form of a carboxyl group (—COOH). That is, the repeating unit derived from (meth) acrylic acid has a hydroxyl group. On the other hand, the repeating unit derived from the (meth) acrylic acid alkyl ester does not have a hydroxyl group.

In the above basic configuration, the shell coverage (unit:%) is represented by the formula “shell coverage = 100 × area of core coating area / area of surface area of toner core”. In the formula, “the area of the surface area of the toner core” corresponds to the sum of the area of the core covering area and the area of the core exposed area. The “core covered region” corresponds to a region covered with the shell layer in the surface region of the toner core, and the “core exposed region” corresponds to a region not covered with the shell layer in the surface region of the toner core. A shell coverage of 100% means that the entire surface of the toner core is covered with the shell layer. The method for measuring the shell coverage is the same method as in the examples described later or an alternative method thereof. The shell coverage may be measured after the external addition treatment. The measurement may be performed while avoiding the external additive, or the measurement may be performed after removing the external additive attached to the toner base particles. The external additive may be dissolved and removed using a solvent (for example, an alkaline solution), or the external additive may be removed from the toner particles using an ultrasonic cleaner.

In the toner having the above basic configuration, the toner core contains a polyester resin. The shell coverage is 60% or more and 80% or less. By including a polyester resin in the toner core, a toner having excellent low-temperature fixability can be easily obtained. Then, by adequately covering the surface region of the toner core containing the polyester resin with a shell layer, it becomes easy to ensure sufficient heat-resistant storage stability and low-temperature fixability of the toner. When the shell coverage is too large, the heat-resistant storage stability of the toner increases, while the low-temperature fixability of the toner tends to be insufficient.

However, when the shell coverage is 60% or more and 80% or less, the area of the surface area of the toner core that is more than 20% and less than 40% is not covered with the shell layer (exposed from the shell layer). ). According to the experiment of the present inventor, when the polyester resin is exposed in the core exposed region (the region not covered by the shell layer in the surface region of the toner core), after the toner is charged (for example, after stirring the toner and the carrier) It has been confirmed that charge attenuation tends to occur. This reason is considered to be because the carboxylic acid component of the polyester resin has high hygroscopicity. The inventor of the present application has found a method for easily and appropriately reducing the hygroscopicity of the toner particle surface (particularly, the hygroscopicity of the polyester resin). Specifically, after forming a shell layer on the surface of the toner core, the obtained core-shell particles are placed in a liquid containing an alkaline substance, and the liquid is heated to a temperature slightly higher than room temperature (for example, 35 ° C. or higher 45 Toner temperature having a low surface hygroscopicity by maintaining a neutral to weak alkaline pH (for example, a pH selected from 7.0 to 11.0) for a sufficient period of time. Particles are obtained. The reason for this is considered that the terminal hydrogen of the carboxyl group (—COOH) of the polyester resin is replaced with a counter ion (for example, alkali metal ion) of an alkaline substance. As this replacement proceeds, the pH of the liquid tends to decrease. Therefore, in order to keep the pH of the liquid constant for a long time, it is considered necessary to add an alkaline substance (for example, sodium hydroxide) to the liquid. Lowering the hygroscopicity of the toner particle surface makes it difficult for water molecules to be adsorbed on the surface of the toner particle, making it possible to suppress charge attenuation (particularly, charge attenuation of the toner in a high-temperature, high-humidity environment). Become.

From the viewpoint of the productivity of the toner (particularly the shell layer), in the above basic structure, one or more repeating units having no hydroxyl group in the resin constituting the shell layer are all repeating units derived from the vinyl compound. Preferably there is. A monomer polymer containing one or more vinyl compounds has a repeating unit derived from the vinyl compound. The vinyl compound is a compound having a vinyl group (CH ₂ ═CH—) or a group in which hydrogen in the vinyl group is substituted (more specifically, ethylene, propylene, butadiene, vinyl chloride, acrylic acid, acrylic Acid methyl, methacrylic acid, methyl methacrylate, acrylonitrile, or styrene). The vinyl compound can be polymerized by addition polymerization with a carbon double bond “C═C” contained in the vinyl group or the like to become a polymer (resin).

In order to suppress charge attenuation of the toner, the resin constituting the shell layer preferably contains a repeating unit derived from an acrylonitrile monomer (hereinafter referred to as an acrylonitrile unit), and is represented by the following formula (1). It is particularly preferred that the repeating unit is included.

In formula (1), R ¹¹ and R ¹² each independently represent a hydrogen atom, a halogen atom, an alkyl group that may have a substituent, or an alkoxy group that may have a substituent. However, none of the substituents has a hydroxyl group. A combination in which R ¹¹ represents a hydrogen atom and R ¹² represents a hydrogen atom or a methyl group is particularly preferred. In the repeating unit derived from acrylonitrile, R ¹¹ and R ¹² each independently represent a hydrogen atom.

In order to suppress charge attenuation of the toner, the repeating unit having the highest molar fraction among the repeating units contained in the resin constituting the shell layer is represented by an acrylonitrile-based unit (more preferably, the formula (1)). (Repeating unit).

In order to ensure sufficient heat-resistant storage stability and low-temperature fixability of the toner while suppressing toner charge attenuation, the resin constituting the shell layer is a repeating unit derived from a styrene monomer in addition to the acrylonitrile unit. (Hereinafter referred to as a styrene-based unit) is preferable. As the styrenic unit, a repeating unit represented by the following formula (2) is particularly preferable.

In formula (2), R ²¹ to R ²⁵ each independently represent a hydrogen atom, a halogen atom, an alkyl group which may have a substituent, an alkoxy group which may have a substituent, or a substituent. The aryl group which may have is represented. R ²⁶ and R ²⁷ each independently represent a hydrogen atom, a halogen atom, or an alkyl group that may have a substituent. However, none of the substituents has a hydroxyl group. R ²¹ to R ²⁵ are each independently a hydrogen atom, a halogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, or a carbon number (specifically, alkoxy and alkyl The total number of carbon atoms) is preferably an alkoxyalkyl group having 2 to 6 carbon atoms. R ²⁶ and R ²⁷ are each independently preferably a hydrogen atom or a methyl group, particularly preferably a combination in which R ²⁷ represents a hydrogen atom and R ²⁶ represents a hydrogen atom or a methyl group. In the repeating unit derived from styrene, each of R ²¹ to R ²⁷ represents a hydrogen atom.

In order to ensure sufficient heat-resistant storage stability and low-temperature fixability of the toner while suppressing toner charge attenuation, the resin constituting the shell layer is particularly preferably a crosslinked styrene-acrylonitrile resin.

In order to achieve both heat-resistant storage stability and low-temperature fixability of the toner, the thickness of the shell layer is preferably 1 nm or more and 20 nm or less. The thickness of the shell layer can be measured by analyzing a TEM (transmission electron microscope) image of the cross section of the toner particles using commercially available image analysis software (for example, “WinROOF” manufactured by Mitani Corporation). If the thickness of the shell layer is not uniform in one toner particle, four equally spaced locations (specifically, two straight lines that are perpendicular to each other at the approximate center of the cross section of the toner particle are drawn. The thickness of the shell layer is measured at each of the four points where the straight line intersects the shell layer, and the arithmetic average of the four measured values obtained is taken as the evaluation value of the toner particles (shell layer thickness). The boundary between the toner core and the shell layer can be confirmed, for example, by selectively dyeing only the shell layer of the toner core and the shell layer. When the boundary between the toner core and the shell layer is unclear in the TEM photographed image, a characteristic element contained in the shell layer in the TEM photographed image is formed by combining TEM and electron energy loss spectroscopy (EELS). By performing the mapping, the boundary between the toner core and the shell layer can be clarified.

Generally, the toner core is roughly classified into a pulverized core (also referred to as a pulverized toner) and a polymerized core (also referred to as a chemical toner). The toner core obtained by the pulverization method belongs to the pulverization core, and the toner core obtained by the aggregation method belongs to the polymerization core. In the toner having the basic structure described above, the toner core is preferably a pulverized core containing a polyester resin. In order to achieve both the heat-resistant storage stability and the low-temperature fixability of the toner, it is particularly preferable that the toner core contains one or more types of melt-kneaded crystalline polyester resins and one or more types of amorphous polyester resins. preferable.

In order to obtain a toner suitable for image formation, the volume median diameter (D ₅₀ ) of the toner is preferably 3 μm or more and less than 10 μm.

Next, the toner core (binder resin and internal additive), shell layer, and external additive will be described in order. Depending on the use of the toner, unnecessary components may be omitted.

[Toner core]
(Binder resin)
In the toner core, the binder resin generally occupies most of the components (for example, 85% by mass or more). For this reason, it is considered that the properties of the binder resin greatly affect the properties of the entire toner core. By using a combination of a plurality of types of resins as the binder resin, the properties of the binder resin (more specifically, the hydroxyl value, acid value, Tg, Tm, etc.) can be adjusted. When the binder resin has an ester group, a hydroxyl group, an ether group, an acid group, or a methyl group, the toner core has a strong tendency to become anionic, and when the binder resin has an amino group or an amide group, The toner core is more prone to become cationic. In order to enhance the binding between the toner core and the shell layer, it is preferable that at least one of the hydroxyl value and the acid value of the binder resin is 10 mgKOH / g or more.

In the toner having the basic configuration described above, the toner core contains a polyester resin. In order to achieve both heat-resistant storage stability and low-temperature fixability of the toner, the toner core preferably contains a crystalline polyester resin and an amorphous polyester resin as the polyester resin. By containing a crystalline polyester resin in the toner core, sharp melt properties can be imparted to the toner core.

In order to achieve both heat-resistant storage stability and low-temperature fixability of the toner, the amount of the crystalline polyester resin contained in the toner core is the total amount of the polyester resin in the toner core (the sum of the crystalline polyester resin and the amorphous polyester resin). The amount is preferably 1% by mass or more and 50% by mass or less, and more preferably 5% by mass or more and 25% by mass or less. For example, when the total amount of the polyester resin in the toner core is 100 g, the amount of the crystalline polyester resin contained in the toner core is preferably 1 g or more and 50 g or less (more preferably 5 g or more and 25 g or less).

In order for the toner core to have an appropriate sharp melt property, it is preferable to contain a crystalline polyester resin having a crystallinity index of 0.90 or more and less than 1.15 in the toner core. The crystallinity index of the resin corresponds to the ratio (= Tm / Mp) of the softening point (Tm) of the resin to the melting point (Mp) of the resin. For amorphous resins, it is often impossible to measure a clear Mp. The measuring method of each of Mp and Tm of the resin is the same method as the examples described later or its alternative method. The crystallinity index of the crystalline polyester resin can be adjusted by changing the type or amount of a material (for example, alcohol and / or carboxylic acid) for synthesizing the crystalline polyester resin. The toner core may contain only one type of crystalline polyester resin, or may contain two or more types of crystalline polyester resins.

The polyester resin is composed of one or more polyhydric alcohols (more specifically, diol, bisphenol, trihydric or higher alcohol as shown below) and one or more polyhydric carboxylic acids (more specifically, Can be obtained by polycondensation with a divalent carboxylic acid or a trivalent or higher carboxylic acid as shown below.

Suitable examples of the aliphatic diol include diethylene glycol, triethylene glycol, neopentyl glycol, 1,2-propanediol, α, ω-alkanediol (more specifically, ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, 1,12-dodecanediol, etc. ), 2-butene-1,4-diol, 1,4-cyclohexanedimethanol, dipropylene glycol, polyethylene glycol, polypropylene glycol, or polytetramethylene glycol.

Examples of suitable bisphenol include bisphenol A, hydrogenated bisphenol A, bisphenol A ethylene oxide adduct, or bisphenol A propylene oxide adduct.

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

Preferable examples of divalent carboxylic acids include aromatic dicarboxylic acids (more specifically, phthalic acid, terephthalic acid, or isophthalic acid), α, ω-alkanedicarboxylic acids (more specifically, malonic acid). Succinic acid, adipic acid, suberic acid, azelaic acid, sebacic acid, or 1,10-decanedicarboxylic acid), alkyl succinic acid (more specifically, n-butyl succinic acid, isobutyl succinic acid, n-octyl succinic acid) Acid, n-dodecyl succinic acid, or isododecyl succinic acid), alkenyl succinic acid (more specifically, n-butenyl succinic acid, isobutenyl succinic acid, n-octenyl succinic acid, n-dodecenyl succinic acid, or isodode Senyl succinic acid, etc.), unsaturated dicarboxylic acids (more specifically maleic acid, fumaric acid, citraconic acid, itaconic acid, or Glutaconic acid and the like), or cycloalkane dicarboxylic acid (more specifically, cyclohexane dicarboxylic acid and the like).

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

In order to achieve both heat-resistant storage stability and low-temperature fixability of the toner, it is particularly preferable that the toner core contains a crystalline polyester resin having a melting point (Mp) of 50 ° C. or higher and 100 ° C. or lower.

In an example of a suitable toner, the amorphous polyester resin comprises one or more bisphenols (more specifically, bisphenol A ethylene oxide adduct or bisphenol A propylene oxide adduct) and one or more dicarboxylic acids ( More specifically, it is a polymer of a monomer (resin raw material) containing terephthalic acid, fumaric acid, alkyl succinic acid, or the like, and the crystalline polyester resin has one or more carbon atoms of 6 or more and 12 or less. Α, ω-alkanedicarboxylic acid (more specifically, adipic acid having 6 carbon atoms or suberic acid having 8 carbon atoms) and one or more α, ω-alkanediols having 2 to 6 carbon atoms ( More specifically, polymerization of a monomer (resin raw material) containing ethylene glycol having 2 carbon atoms, propanediol having 3 carbon atoms, or butanediol having 4 carbon atoms) It is.

In order to achieve both heat-resistant storage stability and low-temperature fixability of the toner, the toner core preferably contains a plurality of types of non-crystalline polyester resins having different softening points (Tm) as the binder resin. It is particularly preferable to contain an amorphous polyester resin having a softening point of not lower than 90 ° C., an amorphous polyester resin having a softening point of not lower than 100 ° C. and not higher than 120 ° C., and an amorphous polyester resin having a softening point of not lower than 125 ° C.

As a suitable example of an amorphous polyester resin having a softening point of 90 ° C. or lower, bisphenol (for example, bisphenol A ethylene oxide adduct and / or bisphenol A propylene oxide adduct) is included as an alcohol component, and an aromatic component is used as an acid component. Non-crystalline polyester resin containing a group dicarboxylic acid (eg, terephthalic acid) and an unsaturated dicarboxylic acid (eg, fumaric acid).

Suitable examples of the non-crystalline polyester resin having a softening point of 100 ° C. or higher and 120 ° C. or lower include bisphenol (for example, bisphenol A ethylene oxide adduct and / or bisphenol A propylene oxide adduct) as an alcohol component, and an acid component. Non-crystalline polyester resin containing aromatic dicarboxylic acid (for example, terephthalic acid) and not containing unsaturated dicarboxylic acid.

As a suitable example of an amorphous polyester resin having a softening point of 125 ° C. or higher, an alcohol component contains bisphenol (for example, bisphenol A ethylene oxide adduct and / or bisphenol A propylene oxide adduct) and carbon as an acid component. Dicarboxylic acid having an alkyl group of several tens or more and 20 or less (for example, dodecyl succinic acid having an alkyl group having 12 carbon atoms), unsaturated dicarboxylic acid (for example, fumaric acid), and trivalent carboxylic acid (for example, trimellitic acid) ) Including non-crystalline polyester resin.

When an amorphous polyester resin is used as the binder resin of the toner core, the number average molecular weight (Mn) of the amorphous polyester resin is 1000 or more and 2000 or less in order to improve the strength of the toner core and the toner fixing property. It is preferable. The molecular weight distribution of amorphous polyester resin (ratio Mw / Mn of mass average molecular weight (Mw) to number average molecular weight (Mn)) is preferably 9 or more and 21 or less.

Further, the toner core may contain a resin other than the polyester resin as the binder resin. Examples of the binder resin other than the polyester resin include, for example, a styrene resin, an acrylic resin (more specifically, an acrylic ester polymer or a methacrylic ester polymer), and an olefin resin (more specifically, A thermoplastic resin such as a vinyl chloride resin, a polyvinyl alcohol, a vinyl ether resin, an N-vinyl resin, a polyamide resin, or a urethane resin. Copolymers of these resins, that is, copolymers in which arbitrary repeating units are introduced into the resin (more specifically, styrene-acrylic acid resin or styrene-butadiene resin) are also bonded. It can be suitably used as a resin.

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

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

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

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

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

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

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

Examples of the release agent include low molecular weight polyethylene, low molecular weight polypropylene, polyolefin copolymer, polyolefin wax, microcrystalline wax, paraffin wax, or aliphatic hydrocarbon wax such as Fischer-Tropsch wax; oxidized polyethylene wax or a block thereof Oxides of aliphatic hydrocarbon waxes such as copolymers; plant waxes such as candelilla wax, carnauba wax, wood wax, jojoba wax, or rice wax; animal properties such as beeswax, lanolin, or whale wax Waxes; mineral waxes such as ozokerite, ceresin, or petrolatum; waxes based on fatty acid esters such as montanic ester waxes or castor waxes; such as deoxidized carnauba wax; Some or all of the fatty acid ester can be preferably used de oxidized wax.

In order to ensure sufficient heat-resistant storage stability and low-temperature fixability of the toner while suppressing charge attenuation of the toner, it is preferable that the toner core contains two or more release agents. Synthetic ester wax and natural ester wax It is particularly preferable to contain (more specifically, carnauba wax or the like). By using a synthetic ester wax as a mold release agent, the melting point of the mold release agent can be easily adjusted to a desired range. A synthetic ester wax can be synthesized, for example, by reacting an alcohol and a carboxylic acid (or carboxylic acid halide) in the presence of an acid catalyst. The raw material of the synthetic ester wax may be, for example, a substance derived from a natural product such as a long-chain fatty acid prepared from natural fats and oils or a commercially available synthetic product.

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

By adding a negatively chargeable charge control agent (more specifically, an organometallic complex or a chelate compound) to the toner core, the anionicity of the toner core can be increased. Further, by adding a positively chargeable charge control agent (more specifically, pyridine, nigrosine, quaternary ammonium salt, or the like) to the toner core, the toner core can be made more cationic. However, if sufficient chargeability is ensured in the toner, it is not necessary to include a charge control agent in the toner core.

(Magnetic powder)
The toner core may contain magnetic powder. Examples of magnetic powder materials include ferromagnetic metals (more specifically, iron, cobalt, nickel, or alloys containing one or more of these metals), ferromagnetic metal oxides (more specifically, Ferrite, magnetite, chromium dioxide, or the like) or a material subjected to ferromagnetization treatment (more specifically, a carbon material or the like imparted with ferromagnetism by heat treatment) can be suitably used. One type of magnetic powder may be used alone, or a plurality of types of magnetic powder may be used in combination.

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

[Shell layer]
The shell layer may be a film without graininess or a film with graininess. When resin particles are used as the shell material, if the material (resin particles) is not completely melted and cured in a film-like form, a film having a form in which the resin particles are two-dimensionally linked (graininess) It is thought that a film with For example, the resin particles can be formed into a film by attaching the resin particles to the surface of the toner core in the liquid and heating the liquid. However, the resin particles may be formed into a film by being heated in the drying step or receiving a physical impact force in the external addition step. The entire shell layer is not necessarily formed integrally. The shell layer may be a single film or an assembly of a plurality of films (islands) that are separated from each other.

Preferred examples of the resin constituting the shell layer (specifically, a resin comprising only one or more repeating units having no hydroxyl group) include a crosslinked styrene-acrylonitrile resin and a crosslinked styrene-alkyl (meth) acrylate. Examples include ester resins and cross-linked styrene resins. The crosslinked styrene-acrylonitrile resin is a polymer of one or more styrene monomers, one or more acrylonitrile monomers, and one or more crosslinking agents. The crosslinked styrene- (meth) acrylic acid alkyl ester resin is a polymer of at least one styrene monomer, at least one (meth) acrylic acid alkyl ester, and at least one crosslinking agent. The crosslinked styrene resin is a polymer of one or more styrene monomers and one or more crosslinking agents. In order to form a uniform crosslinked structure in the resin, an aromatic compound having two or more “C═C” (carbon double bond portion) (more specifically, divinylbenzene or the like) is used as a crosslinking agent. It is preferable to use it.

In order to ensure sufficient heat-resistant storage stability and low-temperature fixability of the toner while suppressing toner charge attenuation, it is particularly preferable that the shell layer is substantially composed of a crosslinked styrene-acrylonitrile resin. As the acrylonitrile monomer for introducing the acrylonitrile unit into the resin, for example, acrylonitrile or methacrylonitrile is preferable. Examples of the styrenic monomer for introducing a styrenic unit into the resin include styrene, α-methylstyrene, 4-methylstyrene, 4-tert-butylstyrene, 4-methoxystyrene, 4-bromostyrene, or 3 -Chlorostyrene is preferred. As a crosslinking agent for introducing a crosslinked structure into the resin, for example, divinylbenzene is preferable.

In order to ensure sufficient heat-resistant storage stability and low-temperature fixability of the toner, the glass transition point (Tg) of the resin constituting the shell layer is preferably 50 ° C. or higher and 100 ° C. or lower.

[External additive]
An external additive (specifically, a powder containing a plurality of external additive particles) may be adhered to the surface of the toner base particles. 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). For example, the toner base particles (powder) and the external additive (powder) are stirred together, so that the external additive adheres to the surface of the toner base particles. The toner base particles and the external additive particles do not chemically react with each other and are physically bonded instead of chemically. The strength of the bond between the toner base particles and the external additive particles depends on the stirring conditions (more specifically, the stirring time, the rotation speed of the stirring, etc.), the particle diameter of the external additive particles, and the shape of the external additive particles. And the surface condition of the external additive particles.

In order to fully perform the functions of the external additive while suppressing the detachment of the external additive particles from the toner particles, the amount of the external additive (if multiple types of external additives are used, The total amount of the additives is preferably 0.5 parts by mass or more and 10 parts by mass or less with respect to 100 parts by mass of the toner base particles.

The external additive particles are preferably inorganic particles such as silica particles or metal oxide particles (more specifically, alumina, titanium oxide, magnesium oxide, zinc oxide, strontium titanate, or barium titanate). Particularly preferred. However, particles of an organic acid compound such as a fatty acid metal salt (more specifically, zinc stearate) or resin particles may be used as the external additive particles. Moreover, you may use the composite particle which is a composite of a multiple types of material as external additive particle | grains. The external additive particles may be surface-treated. One type of external additive may be used alone, or a plurality of types of external additives may be used in combination.

In order to improve the fluidity of the toner, it is preferable to use inorganic particles (powder) having a number average primary particle diameter of 5 nm to 30 nm as external additive particles. 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 to 200 nm are used as the external additive particles. It is preferable to do.

[Toner Production Method]
Hereinafter, an example of a method for producing the toner having the above basic configuration will be described. First, a toner core is prepared. Subsequently, the toner core and the shell material are put in the liquid. In order to form a homogeneous shell layer, it is preferable to dissolve or disperse the shell material in the liquid by, for example, stirring the liquid containing the shell material. Subsequently, the shell material is adhered to the surface of the toner core in the liquid, and the shell material is formed on the surface of the toner core, whereby a shell layer (cured resin layer) is formed on the surface of the toner core. In order to suppress dissolution or elution of the toner core components (particularly the binder resin and the release agent) during the formation of the shell layer, it is preferable to form the shell layer in an aqueous medium. The aqueous medium is a medium containing water as a main component (more specifically, pure water or a mixed liquid of water and a polar medium). The aqueous medium may function as a solvent. A solute may be dissolved in the aqueous medium. The aqueous medium may function as a dispersion medium. The dispersoid may be dispersed in the aqueous medium. As a polar medium in the aqueous medium, for example, alcohol (more specifically, methanol or ethanol) can be used. The boiling point of the aqueous medium is about 100 ° C.

Hereinafter, the toner manufacturing method according to the present embodiment will be further described based on a more specific example.

(Preparation of toner core)
In order to easily obtain a good quality toner core, the toner core is preferably produced by an agglomeration method or a pulverization method, and more preferably produced by a pulverization method.

Hereinafter, an example of the pulverization method will be described. First, a binder resin (for example, a polyester resin) and an internal additive (for example, at least one of a colorant, a release agent, a charge control agent, and a magnetic powder) are mixed. Subsequently, the obtained mixture is melt-kneaded. Subsequently, the obtained melt-kneaded product is pulverized, and the obtained pulverized product is classified. As a result, a toner core having a desired particle size can be obtained.

Hereinafter, an example of the aggregation method will be described. First, these particles are aggregated in an aqueous medium containing fine particles of a binder resin (for example, a polyester resin), a release agent, and a colorant until a desired particle diameter is obtained. Thereby, aggregated particles containing the binder resin, the release agent, and the colorant are formed. Subsequently, the obtained aggregated particles are heated to unite the components contained in the aggregated particles. As a result, a toner core dispersion is obtained. Thereafter, an unnecessary substance (such as a surfactant) is removed from the dispersion liquid of the toner core to obtain the toner core.

(Formation of shell layer)
An acidic substance (for example, hydrochloric acid) is added to ion-exchanged water to prepare a weakly acidic (for example, pH selected from 3 to 5) aqueous medium. Subsequently, a toner core and a suspension of resin particles are added to an aqueous medium whose pH is adjusted. The suspension of resin particles corresponds to the shell material. The resin particles contained in the suspension are, for example, a crosslinked styrene-acrylonitrile resin composed only of repeating units having no hydroxyl group (for example, a co-polymer of a monomer (resin raw material) containing styrene having a crosslinked structure and acrylonitrile). It is substantially composed of a combination. The glass transition point of the resin particles contained in the suspension is, for example, 50 ° C. or higher and 100 ° C. or lower.

When a monomer or a prepolymer is added to an aqueous medium as a shell material and the shell material is polymerized on the surface of the toner core, a shell layer having a shell coverage of 100% (complete coating) is easily formed on the surface of the toner core. On the other hand, when pre-resinized particles (resin particles) are used as the shell material, it becomes easy to form a shell layer having a shell coverage of 60% or more and 80% or less on the surface of the toner core.

Resin particles (shell material) adhere to the surface of the toner core in the liquid. In order to uniformly adhere the resin particles to the surface of the toner core, it is preferable to highly disperse the toner core in a liquid containing the resin particles. In order to highly disperse the toner core in the liquid, a surfactant may be included in the liquid, or the liquid is stirred using a powerful stirring device (for example, “Hibis Disper Mix” manufactured by Primics Co., Ltd.). May be. As the surfactant, for example, sulfate ester salt, sulfonate salt, phosphate ester salt, or soap can be used.

Subsequently, an alkaline substance (for example, sodium hydroxide) is added to the liquid containing the toner core and the resin particles to adjust the pH of the liquid to about 7 (for example, a pH selected from 7.0 to 8.0). .

Subsequently, while stirring the liquid containing the toner core and the resin particles, the temperature of the liquid is changed to a predetermined temperature (for example, 55 at a speed selected from 0.1 ° C./min to 3 ° C./min). To a temperature selected from 85 ° C. to 85 ° C. Further, the temperature of the liquid is maintained at the temperature for a predetermined time (for example, a time selected from 30 minutes to 4 hours) while stirring the liquid. As a result, a shell layer is formed on the surface of the toner core, and a dispersion of core-shell particles before alkali treatment (hereinafter referred to as pre-treatment particles) is obtained.

By the above-described method, a toner core containing a polyester resin and a shell containing a resin composed of only one or more repeating units having a surface area ratio of 60% to 80% and covering the surface of the toner core and having no hydroxyl group Core-shell particles (pre-treatment particles) comprising a layer can be prepared.

As described above, the resin particles are adhered to the surface of the toner core in the liquid, and the liquid is heated, whereby the resin particles can be dissolved (or deformed) to form a film. However, the resin particles may be formed into a film by being heated in the drying step or receiving a physical impact force in the external addition step.

Subsequently, the temperature of the obtained dispersion of pre-treated particles is adjusted to a temperature slightly higher than room temperature (for example, a temperature selected from 35 ° C. to 50 ° C.). Thereafter, an alkaline substance containing alkali metal ions (for example, sodium hydroxide) is added to the dispersion of the pre-treatment particles, and the pH of the liquid is in a neutral to weakly alkaline range (for example, 7.0 to 11.0). To a pH selected from Furthermore, the dispersion liquid of the particles before the treatment is maintained at such a temperature and pH for a predetermined time (for example, a time selected from 30 minutes to 4 hours). As a result, a dispersion of toner base particles (particles surface-treated with an alkaline substance) is obtained. In a part of the core exposed region of the obtained toner base particles, it is considered that the exposed carboxylate ion (—COO ⁻ ) of the polyester resin is bonded to an alkali metal ion (for example, sodium ion). If the temperature during the alkali treatment is too high, the toner base particles tend to aggregate.

Subsequently, the dispersion of the toner base particles is filtered using, for example, a Buchner funnel. Thereby, the toner base particles are separated from the liquid (solid-liquid separation), and wet cake-like toner base particles are obtained. Subsequently, the obtained wet cake-like toner base particles are washed. Subsequently, the washed toner base particles are dried.

Thereafter, if necessary, the toner base particles and the external additive are mixed using a mixer (for example, FM mixer manufactured by Nippon Coke Kogyo Co., Ltd.), and the external additive is adhered to the surface of the toner base particles. May be.

It should be noted that the content and order of the toner manufacturing method can be arbitrarily changed according to the required configuration or characteristics of the toner. For example, when reacting a material (for example, a shell material) in a liquid, the material may be reacted in the liquid for a predetermined time after the material is added to the liquid, or the material is added to the liquid over a long period of time. Then, the material may be reacted in the liquid while adding the material to the liquid. Further, the shell material may be added to the liquid at once, or may be added to the liquid in a plurality of times. The toner may be sieved after the external addition step. Further, unnecessary steps may be omitted. For example, when a commercially available product can be used as a material as it is, the step of preparing the material can be omitted by using a commercially available product. If an external additive is unnecessary, the external addition process may be omitted. When the external additive is not attached to the surface of the toner base particles (the step of external addition is omitted), the toner base particles correspond to the toner particles. As a material for synthesizing the resin, a prepolymer may be used instead of the monomer, if necessary. In order to obtain a predetermined compound, a salt, ester, hydrate, or anhydride of the compound may be used as a raw material. In order to produce the toner efficiently, it is preferable to form a large number of toner particles simultaneously. The toner particles produced at the same time are considered to have substantially the same configuration.

Examples of the present invention will be described. Table 1 shows toners TA-1 to TA-5, TB-1 to TB-3, and TC-1 to TC-4 (each toner for developing an electrostatic latent image) according to Examples or Comparative Examples. In Table 1, “crosslinked ST-AN resin” indicates a crosslinked styrene-acrylonitrile resin.

Hereinafter, manufacturing methods, evaluation methods, and evaluation results of toners TA-1 to TA-5, TB-1 to TB-3, and TC-1 to TC-4 will be described in order. In the evaluation in which an error occurs, a considerable number of measurement values with sufficiently small errors are obtained, and the arithmetic average of the obtained measurement values is used as the evaluation value. A scanning electron microscope (“JSM-7600F” manufactured by JEOL Ltd.) was used for measurement of the number average primary particle size of the powder. In addition, methods for measuring Tg (glass transition point), Mp (melting point), and Tm (softening point) are as follows unless otherwise specified.

<Measurement method of Tg>
As a measuring device, a differential scanning calorimeter (“DSC-6220” manufactured by Seiko Instruments Inc.) was used. The Tg (glass transition point) of the sample was determined by measuring the endothermic curve of the sample using a measuring device. Specifically, about 10 mg of a sample (for example, resin) was placed in an aluminum dish (aluminum container), and the aluminum dish was set in the measurement unit of the measuring device. In addition, an empty aluminum dish was used as a reference. In the measurement of the endothermic curve, the temperature of the measurement part was increased from the measurement start temperature of 25 ° C. to 200 ° C. at a rate of 10 ° C./min (RUN1). Thereafter, the temperature of the measurement part was lowered from 200 ° C. to 25 ° C. at a rate of 10 ° C./min. Subsequently, the temperature of the measurement part was again raised from 25 ° C. to 200 ° C. at a rate of 10 ° C./min (RUN 2). An endothermic curve (vertical axis: heat flow (DSC signal), horizontal axis: temperature) of the sample was obtained by RUN2. The Tg of the sample was read from the obtained endothermic curve. In the endothermic curve, the temperature (onset temperature) of the specific heat change point (intersection of the extrapolation line of the base line and the extrapolation line of the falling line) corresponds to the Tg (glass transition point) of the sample.

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

<Measurement method of Mp>
As a measuring device, a differential scanning calorimeter (“DSC-6220” manufactured by Seiko Instruments Inc.) was used. The Mp (melting point) of the sample was determined by measuring the endothermic curve of the sample using a measuring device. Specifically, about 15 mg of a sample (for example, resin) was put in an aluminum dish (aluminum container), and the aluminum dish was set in the measurement unit of the measuring device. In addition, an empty aluminum dish was used as a reference. In the measurement of the endothermic curve, the temperature of the measurement part was increased from a measurement start temperature of 30 ° C. to 170 ° C. at a rate of 10 ° C./min. During the temperature increase, the endothermic curve (vertical axis: heat flow (DSC signal), horizontal axis: temperature) of the sample was measured. The Mp of the sample was read from the obtained endothermic curve. In the endothermic curve, the maximum peak temperature due to the heat of fusion corresponds to the Mp (melting point) of the sample.

[Preparation of toner core material]
(Synthesis of crystalline polyester resin)
In a 10 L four-necked flask equipped with a thermometer (thermocouple), dehydration tube, nitrogen inlet tube, and stirring device, 2231 g of ethylene glycol, 5869 g of suberic acid, and 40 g of tin (II) 2-ethylhexanoate And 3 g of gallic acid. Subsequently, the contents of the flask were reacted for 4 hours under conditions of a nitrogen atmosphere and a temperature of 180 ° C. Subsequently, the contents of the flask were heated and reacted at a temperature of 210 ° C. for 10 hours. Subsequently, the contents of the flask were reacted for 1 hour in a reduced pressure atmosphere (pressure 8.3 kPa) and a temperature of 210 ° C. As a result, a crystalline polyester resin having Tm of 78 ° C. and Mp of 74 ° C. was obtained.

(Synthesis of non-crystalline polyester resin A)
In a 10 L four-necked flask equipped with a thermometer (thermocouple), dehydration tube, nitrogen introduction tube, and stirrer, 370 g of bisphenol A propylene oxide adduct, 3059 g of bisphenol A ethylene oxide adduct, terephthalic acid 1194 g, fumaric acid 286 g, tin (II) 2-ethylhexanoate 10 g and gallic acid 2 g were added. Subsequently, the contents of the flask were reacted in a nitrogen atmosphere and at a temperature of 230 ° C. until the reaction rate reached 90% by mass or more. The reaction rate was calculated according to the formula “reaction rate = 100 × actual amount of reaction product water / theoretical product water amount”. Subsequently, the flask contents were reacted under a reduced pressure atmosphere (pressure 8.3 kPa) and a temperature of 230 ° C. until the Tm of the reaction product (resin) reached a predetermined temperature (89 ° C.). As a result, an amorphous polyester resin A having a Tm of 89 ° C. and a Tg of 50 ° C. was obtained.

(Synthesis of non-crystalline polyester resin B)
The method for synthesizing the non-crystalline polyester resin B is as follows. The method was the same as the synthesis method of the amorphous polyester resin A except that 2218 g of the oxide adduct and 1603 g of terephthalic acid were used. Regarding the obtained non-crystalline polyester resin B, Tm was 111 ° C. and Tg was 69 ° C.

(Synthesis of non-crystalline polyester resin C)
In a 10 L four-necked flask equipped with a thermometer (thermocouple), dehydration tube, nitrogen introduction tube, and stirring device, 4907 g of bisphenol A propylene oxide adduct, 1942 g of bisphenol A ethylene oxide adduct, and fumaric acid 757 g, 2078 g of dodecyl succinic anhydride, 30 g of tin (II) 2-ethylhexanoate, and 2 g of gallic acid were added. Subsequently, the contents of the flask were reacted in a nitrogen atmosphere and at a temperature of 230 ° C. until the reaction rate represented by the above formula reached 90% by mass or more. Subsequently, the contents of the flask were reacted for 1 hour in a reduced pressure atmosphere (pressure 8.3 kPa) and a temperature of 230 ° C. Subsequently, 548 g of trimellitic anhydride is added to the flask, and Tm of the reaction product (resin) reaches a predetermined temperature (127 ° C.) under a reduced pressure atmosphere (pressure 8.3 kPa) and a temperature of 220 ° C. The flask contents were reacted. As a result, an amorphous polyester resin C having a Tm of 127 ° C. and a Tg of 51 ° C. was obtained.

[Preparation of shell material]
A round bottom flask equipped with an anchor type stirring blade was set in a water bath at a temperature of 30 ° C., and 20 parts by mass of styrene, 80 parts by mass of acrylonitrile, 10 parts by mass of divinylbenzene, potassium persulfate (water solution) 4.5 parts by mass of a polymerization polymerization initiator) and 100 parts by mass of ion-exchanged water. And the temperature in a flask was heated up to 70 degreeC using the water bath, stirring the flask contents at a rotational speed of 100 rpm using the anchor type stirring blade. Thereafter, emulsion polymerization (soap-free) is carried out at a temperature of 70 ° C. for 8 hours while stirring at a rotation speed of 100 rpm, and a dispersion of resin particles (specifically, crosslinked styrene-acrylonitrile resin particles) is obtained in the flask. It was. The obtained dispersion was filtered (solid-liquid separation), and the resulting resin particles were washed, and then redispersed in an aqueous solution of sodium alkyl ether sulfate having a concentration of 10% by mass. As a result, a suspension of resin particles having a solid content concentration of 8% by mass was obtained. Regarding the resin particles contained in the obtained suspension, the number average primary particle diameter was 20 nm, and Tg was 73 ° C. The resin particles contained in the suspension were substantially composed of a crosslinked styrene-acrylonitrile resin.

[Method for Producing Toners TA-1 to TA-5, TB-1, TC-1 to TC-4]
(Production of toner core)
300 g of a first binder resin (amorphous polyester resin A synthesized by the above procedure), 100 g of a second binder resin (amorphous polyester resin B synthesized by the above procedure), and a third binder resin ( 600 g of the non-crystalline polyester resin C synthesized by the above procedure, 100 g of the fourth binder resin (crystalline polyester resin synthesized by the above procedure), and the first release agent (carnauba wax: manufactured by Hiroyuki Kato Co., Ltd.) 12 g of “Carnauba Wax No. 1”, 48 g of a second release agent (synthetic ester wax: “Nissan Electol (registered trademark) WEP-3” manufactured by NOF Corporation), and a colorant (manufactured by Sanyo Dye Co., Ltd.) 144 g of “Colortex (registered trademark) Blue B1021”, component: phthalocyanine blue), using an FM mixer (manufactured by Nippon Coke Kogyo Co., Ltd.) and a rotational speed of 2400 They were mixed in a pm.

Subsequently, the obtained mixture was subjected to conditions using a twin-screw extruder (“PCM-30” manufactured by Ikegai Co., Ltd.) at a material supply speed of 5 kg / hour, a shaft rotation speed of 160 rpm, and a set temperature (cylinder temperature) of 100 ° C. Was melt kneaded. Thereafter, the obtained kneaded material was cooled. Subsequently, the cooled kneaded material was coarsely pulverized using a pulverizer (“Rotoplex 16/8” manufactured by Toa Machinery Co., Ltd.). Subsequently, the obtained coarsely pulverized product was finely pulverized using a jet mill (“Ultrasonic Jet Mill Type I” manufactured by Nippon Pneumatic Industry Co., Ltd.). Subsequently, the obtained finely pulverized product was classified using a classifier (“Elbow Jet EJ-LABO type” manufactured by Nippon Steel Mining Co., Ltd.). As a result, a toner core having a volume median diameter (D ₅₀ ) of 6.8 μm was obtained.

(Shell layer forming process)
A 1 L three-necked flask equipped with a thermometer and a stirring blade was set in a water bath, and 300 mL of ion-exchanged water was placed in the flask. Thereafter, the temperature in the flask was kept at 30 ° C. using a water bath. Subsequently, dilute hydrochloric acid was added to the flask to adjust the pH of the flask contents to 4. Subsequently, the shell material (a suspension of the cross-linked styrene-acrylonitrile resin prepared by the above procedure) was added into the flask in the amount shown in Table 1. For example, in the production of toner TA-1, 20 g of suspension (solid content concentration: 8% by mass) was added as a shell material to the flask. Further, in the production of the toner TB-1, no shell material (suspension) was added.

Subsequently, 300 g of a toner core (toner core produced by the above procedure) and 1 g of an anionic surfactant (“Emar (registered trademark) 0” manufactured by Kao Corporation, component: sodium lauryl sulfate) were added to the flask. The flask contents were stirred for 1 hour at a rotation speed (stirring blade) of 200 rpm.

Subsequently, 300 mL of ion exchange water was added to the flask. Subsequently, sodium hydroxide was added to the flask to adjust the pH of the flask contents to 7.5. The temperature of the flask contents at this point was 30 ° C. Subsequently, the flask contents were heated at a rate of 1 ° C./min while stirring the flask contents at a rotation speed (stirring blade) of 100 rpm. Then, when the temperature of the flask contents reached 62 ° C., the temperature increase was stopped and cold water was put into the flask to rapidly cool the flask contents to 40 ° C. Subsequently, sodium hydroxide was added to the flask to adjust the pH of the flask contents to the values shown in Table 1. For example, in the production of toner TA-1, the pH of the flask contents was adjusted to 10. Thereafter, while stirring the flask contents at a rotation speed (stirring blade) of 100 rpm, the flask contents were kept at a temperature of 40 ° C. and the adjusted pH (10 for toner TA-1) for 1 hour. The pH of the flask contents tended to decrease with time. For this reason, the pH of the flask contents was maintained at the values shown in Table 1 while adding sodium hydroxide into the flask. Thus, a dispersion of toner base particles was obtained in the flask.

(Washing process)
The dispersion of toner base particles obtained as described above was filtered (solid-liquid separation) using a Buchner funnel. As a result, toner base particles in the form of wet cake were obtained. Thereafter, the obtained wet cake-like toner base particles were redispersed in 1.5 L of ion-exchanged water. The toner base particles were washed by repeating dispersion and filtration until the electric conductivity of the filtrate after washing (washing water) reached 3 μS / cm. For the measurement of conductivity, an electric conductivity meter “HORIBA ES-51” manufactured by Horiba, Ltd. was used.

(Drying process)
Subsequently, the washed wet cake-like toner mother particles were put in a vacuum shelf dryer and dried for 24 hours under the conditions of a vacuum degree of 1 kPa and a temperature of 40 ° C. As a result, dried toner base particles (powder) were obtained.

(External addition process)
Subsequently, 100 parts by mass of toner base particles and 1.0 part by mass of positively chargeable silica particles (silica particles imparted with positive charge by surface treatment: “AEROSIL (registered trademark) REA90” manufactured by Nippon Aerosil Co., Ltd.) , Conductive titanium oxide particles (“EC-100” manufactured by Titanium Industry Co., Ltd., base material: TiO ₂ , coating layer: Sb-doped SnO ₂ film) and 0.5 part by mass of FM mixer (Nippon Coke Industries, Ltd.) with a capacity of 10 L For 5 minutes. As a result, external additives (silica particles and titanium oxide particles) adhered to the surface of the toner base particles. Thereafter, sieving was performed using a 200 mesh sieve (aperture 75 μm). As a result, toners containing a large number of toner particles (toners TA-1 to TA-5, TB-1, and TC-1 to TC-4 shown in Table 1) were obtained.

[Production Method of Toner TB-2]
The production method of the toner TB-2 is the same as the production method of the toner TA-1, except that the suspension of the polyester resin prepared by the following method is used in the shell layer forming step instead of the suspension of the crosslinked styrene-acrylonitrile resin. Met.

<Method for preparing suspension of polyester resin>
In a reaction vessel equipped with a stirrer, a heating / cooling device, a thermometer, and a dehydrator, 681 parts by mass of bisphenol A · EO (ethylene oxide) 2 mol adduct and bisphenol A · PO (propylene oxide) 2 mol adduct 81 Part by mass, 282 parts by mass of terephthalic acid, 22 parts by mass of trimellitic anhydride, and 2 parts by mass of dibutyltin oxide were added. Subsequently, after dehydration reaction was performed in the container under conditions of normal pressure and temperature of 230 ° C. for 5 hours, dehydration reaction was further performed under conditions of reduced pressure atmosphere (pressure 0.0004 MPa) and temperature of 230 ° C. for 5 hours. As a result, a polyester resin having a number average molecular weight (Mn) of 2200, a mass average molecular weight (Mw) of 9500, and a Tg (glass transition point) of 60 ° C. was obtained.

Subsequently, 50 parts by mass of the polyester resin obtained as described above and 250 parts by mass of methyl ethyl ketone were placed in a reaction vessel equipped with a stirrer, a heating / cooling device, a thermometer, and a solvent removal apparatus. Subsequently, the temperature in the container was raised to 80 ° C. to dissolve the polyester resin. Thereafter, the temperature in the container was lowered to 40 ° C., and 5 parts by mass of triethylamine was added to the container. Subsequently, the obtained container contents were poured into 1000 parts by mass of ion-exchanged water stirred in another container and emulsified. Thereafter, methyl ethyl ketone was removed to obtain a polyester resin suspension. With respect to the resin particles (polyester resin particles) contained in the obtained suspension, the volume median diameter (D ₅₀ ) was 20 nm. For measurement of the volume median diameter (D ₅₀ ), a laser diffraction / scattering particle size distribution measuring device (“LA-920” manufactured by Horiba, Ltd.) was used.

[Production Method of Toner TB-3]
The manufacturing method of toner TB-3 is the same as the manufacturing method of toner TA-1, except that, in the shell layer forming step, a crosslinked styrene resin suspension prepared by the following method was used instead of the crosslinked styrene-acrylonitrile resin suspension. It was the same.

<Method for preparing suspension of crosslinked styrene resin>
A round bottom flask equipped with an anchor type stirring blade was set in a water bath at a temperature of 30 ° C., and 100 parts by mass of styrene, 10 parts by mass of divinylbenzene, and potassium persulfate (water-soluble polymerization initiator) 4 were placed in the flask. 0.5 parts by mass and 100 parts by mass of ion-exchanged water were added. And the temperature in a flask was heated up to 70 degreeC using the water bath, stirring the flask contents at a rotational speed of 100 rpm using the anchor type stirring blade. Thereafter, emulsion polymerization (soap-free) was performed at a temperature of 70 ° C. for 6 hours while continuing stirring at a rotation speed of 100 rpm to obtain a dispersion of resin particles (specifically, crosslinked styrene resin particles) in the flask. The obtained dispersion was filtered (solid-liquid separation), and the resulting resin particles were washed, and then redispersed in an aqueous solution of sodium alkyl ether sulfate having a concentration of 10% by mass. As a result, a suspension of resin particles having a solid content concentration of 8% by mass (a suspension of a crosslinked styrene resin) was obtained. Regarding the resin particles contained in the obtained suspension, the number average primary particle diameter was 20 nm, and Tg was 75 ° C. The resin particles contained in the suspension were substantially composed of a crosslinked styrene resin.

Regarding the toners TA-1 to TA-5, TB-1 to TB-3, and TC-1 to TC-4 obtained as described above, the shell coverage and the amount of hydrogen ions existing on the surface of the toner particles ( Table 1 shows the result of measuring (per 1 g of toner). For example, for toner TA-1, the shell coverage was 72% and the hydrogen ion content was 3.0 × 10 ⁻¹⁰ mol / g. Each measuring method of the shell coverage and the amount of hydrogen ions was as follows.

<Measurement method of shell coverage>
The toner base particles (toner before external addition) of each sample (any one of toners TA-1 to TA-5, TB-1 to TB-3, and TC-1 to TC-4) were measured. Specifically, the toner base particles (powder) to be measured are exposed to the vapor of 2 mL of a 0.5% by weight aqueous RuO ₄ solution for 5 minutes in an air atmosphere at room temperature (25 ° C.), whereby the toner base is obtained. The particles were Ru stained. The dyed toner base particles are observed with a field emission scanning electron microscope (FE-SEM) (“JSM-7600F” manufactured by JEOL Ltd.) at a magnification of 50000 times. I got a statue. Of the surface area of the toner core, the area covered with the shell layer was easily dyed with ruthenium.

In the obtained reflected electron image, the brightness value was divided into 256, with the brightest value being 255 and the darkest value being 0. Then, using the image analysis software (“WinROOF” manufactured by Mitani Shoji Co., Ltd.), the binarization process based on the luminance value 144 was performed on the reflected electron image. After binarization, the area SA1 of the entire reflected electron image of the toner base particles (corresponding to the total number of pixels in the reflected electron image) and the area SB1 of the region having a luminance value of 144 or more in the reflected electron image (reflected electron image) And corresponding to the number of pixels having a luminance value of 144 or more), and the shell coverage (unit:%) was calculated according to the following formula.
Shell coverage = 100 × area SB1 / area SA1

<Method for measuring the amount of hydrogen ions present on the surface of toner particles>
1 part by mass of the sample (toner) (50 g of toner) was placed in 2 parts by mass of ion-exchanged water (100 g of ion-exchanged water) to obtain a toner dispersion. The toner dispersion was gently stirred while the temperature of the toner dispersion was kept at 25 ° C., and the pH of the toner dispersion was measured. The toner dispersion liquid at a temperature of 25 ° C. is continuously stirred until the pH of the toner dispersion liquid is stabilized, and the measured pH value at the time when the pH of the toner dispersion liquid is stabilized is measured for the sample (toner). Value (pH value). A pH meter (“D-51” manufactured by Horiba, Ltd.) was used for pH measurement. From the measured value (pH value) obtained, the amount of hydrogen ions (unit: mol / g) present on the surface of the toner particles was calculated according to the following formula.
Amount of hydrogen ions = 10 ^−pH value × 1000 / (amount of ion exchange water × amount of toner)

For example, with toner TA-1, the measured pH value was 10.22. For this reason, the amount of hydrogen ions present on the surface of the toner particles was “10 ^−10.22 × 1000 / (20 × 10) = 3.0 × 10 ⁻¹⁰ ” (unit: mol / g) (see Table 1). ).

[Evaluation methods]
The evaluation method of each sample (toners TA-1 to TA-5, TB-1 to TB-3, and TC-1 to TC-4) is as follows.

(Minimum fixing temperature)
100 parts by weight of developer carrier (carrier for “TASKalfa 5550ci” manufactured by Kyocera Document Solutions Co., Ltd.) and 10 parts by weight of sample (toner) were mixed for 30 minutes using a ball mill to prepare a two-component developer. .

An image was formed using the two-component developer prepared as described above, and the minimum fixing temperature was evaluated. As an evaluation machine, a color printer having a Roller-Roller type heat and pressure fixing device (an evaluation machine in which “FS-C5250DN” manufactured by Kyocera Document Solutions Co., Ltd. was modified to change the fixing temperature) was used. The two-component developer prepared as described above was charged into the developing device of the evaluation machine, and the sample (replenishment toner) was charged into the toner container of the evaluation machine.

Using the above-mentioned evaluation machine, a linear speed of 200 mm / second and a toner applied amount of 1.0 mg / cm on a paper having a basis weight of 90 g / m ² (A4 size printing paper) in an environment of a temperature of 25 ° C. and a humidity of 50% RH. ^Under the condition ² , a solid image having a size of 25 mm × 25 mm (specifically, an unfixed toner image) was formed. Subsequently, the paper on which the image was formed was passed through the fixing device of the evaluation machine.

In the evaluation of the minimum fixing temperature, the measuring range of the fixing temperature was 100 ° C. or higher and 200 ° C. or lower. Specifically, the fixing temperature of the fixing device is increased from 100 ° C. by 5 ° C. (in the vicinity of the minimum fixing temperature by 2 ° C.), and the minimum temperature (minimum fixing temperature) at which a solid image (toner image) can be fixed on paper is set. It was measured. Whether or not the toner could be fixed was confirmed by a rubbing test as shown below. Specifically, the evaluation paper passed through the fixing device was bent so that the surface on which the image was formed was on the inside, and the image on the fold was rubbed 5 times with a 1 kg weight coated with a cloth. Subsequently, the paper was spread and the bent portion of the paper (the portion where the solid image was formed) was observed. Then, the length (peeling length) of toner peeling at the bent portion was measured. The lowest temperature among the fixing temperatures at which the peeling length was 1 mm or less was defined as the lowest fixing temperature. When the minimum fixing temperature was 150 ° C. or lower, it was evaluated as “good”, and when the minimum fixing temperature exceeded 150 ° C., it was evaluated as “poor” (not good).

(Heat resistant storage stability)
3 g of the sample (toner) was put in a 20 mL polyethylene container, and the container was left in a thermostat set at 58 ° C. for 3 hours. Thereafter, the toner taken out from the thermostat was cooled to room temperature to obtain an evaluation toner.

Subsequently, the obtained toner for evaluation was placed on a sieve having a known mass of 200 mesh (aperture 75 μm). Then, the mass of the sieve containing the toner was measured, and the mass of the toner before sieving was determined. Subsequently, a sieve is set in a powder property evaluation apparatus (“Powder Tester (registered trademark)” manufactured by Hosokawa Micron Co., Ltd.), and according to the manual of the powder tester, the sieve is vibrated for 30 seconds under the condition of the rheostat scale 5 to evaluate toner. Was sieved. Then, after sieving, the mass of the toner remaining on the sieve was determined by measuring the mass of the sieve containing the toner. From the mass of the toner before sieving and the mass of the toner after sieving (the mass of toner remaining on the sieving after sieving), the degree of aggregation (unit: mass%) was determined based on the following formula.
Aggregation degree = 100 × mass of toner after sieving / mass of toner before sieving

When the degree of aggregation was 20% by mass or less, it was evaluated as “good”, and when the degree of aggregation exceeded 20% by mass, it was evaluated as “poor” (not good).

(Charge decay characteristics)
As an evaluation machine, an electrostatic diffusivity measuring device (“NS-D100” manufactured by Nano Seeds Co., Ltd.) was used. The evaluator can charge the sample and monitor the charge decay state of the charged sample with a surface potentiometer. The evaluation method was a method based on JIS (Japanese Industrial Standards) C 61340-2-1-2006. Hereinafter, a method for evaluating the charge decay constant will be described in detail.

The sample (toner) was put in the measurement cell. The measurement cell was a metal cell in which a recess having an inner diameter of 10 mm and a depth of 1 mm was formed. The sample was pushed in from above using a slide glass, and the concave portion of the cell was filled with the sample. The sample overflowed from the cell was removed by reciprocating the slide glass on the surface of the cell. The filling amount of the sample (toner) was 0.05 g.

Subsequently, the measurement cell filled with the sample was allowed to stand for 12 hours in an environment of a temperature of 32.5 ° C. and a humidity of 80% RH. Subsequently, the measurement object was charged by corona discharge under the conditions of a voltage of 10 kV and a charging time of 0.5 seconds. Then, after 0.7 seconds had elapsed from the end of corona discharge, the surface potential of the measurement object was continuously recorded under the conditions of a sampling frequency of 10 Hz and a maximum measurement time of 300 seconds. Based on the recorded surface potential data and the equation “V = V ₀ exp (−α√t)”, the charge decay constant α is calculated for the decay time of 2 seconds (the period from the start of measurement to 2 seconds later). did. In the formula, V represents the surface potential [V], V ₀ represents the initial surface potential [V], and t represents the decay time [second].

When the charge decay constant was 0.020 or less, it was evaluated as ◯ (good), and when the charge decay constant exceeded 0.020, it was evaluated as x (not good).

[Evaluation results]
For each of toners TA-1 to TA-5, TB-1 to TB-3, and TC-1 to TC-4, heat-resistant storage stability (aggregation), low-temperature fixability (minimum fixing temperature), and charge decay characteristics The results of evaluating (charge decay constant) are shown in Table 2.

The toners TA-1 to TA-3, TB-3, and TC-1 to TC-2 (toners according to Examples 1 to 6) each had the above-described basic configuration. Specifically, the toners TA-1 to TA-3, TB-3, and TC-1 to TC-2 each include a plurality of toner particles including a toner core and a shell layer. The toner core contained a polyester resin (specifically, non-crystalline polyester resins A to C and a crystalline polyester resin). The shell layer contained a resin composed of only one or more repeating units having no hydroxyl group (specifically, a crosslinked styrene-acrylonitrile resin or a crosslinked styrene resin) (see Table 1). The shell coverage (the area ratio of the area covered by the shell layer in the surface area of the toner core) was 60% or more and 80% or less (see Table 1). The amount of hydrogen ions present on the surface of the toner particles was 5.0 × 10 ⁻¹¹ mol or more and 5.0 × 10 ⁻¹⁰ mol or less per 1 g of toner (see Table 1). In each of toners TA-1 to TA-3, TB-3, and TC-1 to TC-2, the thickness of the shell layer was 10 nm or more and 20 nm or less.

As shown in Table 2, the toners TA-1 to TA-3, TB-3, and TC-1 to TC-2 were excellent in all of heat-resistant storage stability, low-temperature fixability, and charge decay characteristics, respectively. .

In the toner TC-3 (the toner according to Comparative Example 5), the evaluation results of the heat resistant storage stability and the charge decay characteristic were worse than those of the toners TA-1 to TA-3 and TC-1 to TC-2. This is because the polyester resin (binder resin) in the toner core is hydrolyzed because the pH is excessively increased by adjusting the pH after the shell layer is formed on the surface of the toner core (after cooling) (see Table 1). it is conceivable that. In addition, it is considered that the shell layer was peeled off from the surface of the toner core due to hydrolysis of the polyester resin.

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.

Claims (13)

1. An electrostatic latent image developing toner comprising a plurality of toner particles each having a core and a shell layer covering the surface of the core,
   The core contains a polyester resin,
   The shell layer contains a resin composed only of one or more repeating units having no hydroxyl group,
   The area ratio of the region covered by the shell layer in the surface region of the core is 60% or more and 80% or less,
   The electrostatic latent image developing toner, wherein the amount of hydrogen ions present on the surface of the toner particles is 5.0 × 10 ⁻¹¹ mol or more and 5.0 × 10 ⁻¹⁰ mol or less per 1 g of the toner.
2. The electrostatic latent image developing toner according to claim 1, wherein in the resin constituting the shell layer, all of the one or more repeating units having no hydroxyl group are repeating units derived from a vinyl compound.
3. The electrostatic resin for developing an electrostatic latent image according to claim 2, wherein the resin constituting the shell layer includes a repeating unit represented by the following formula (1) and a repeating unit represented by the following formula (2). toner.
   

   

   [In Formula (1), R ¹¹ and R ¹² each independently have a hydrogen atom, a halogen atom, an alkyl group that may have a substituent that does not contain a hydroxyl group, or a substituent that does not contain a hydroxyl group. Represents an optionally substituted alkoxy group. ]
   

   

   [In the formula (2), R ²¹ to R ²⁵ each independently have a hydrogen atom, a halogen atom, an alkyl group that may have a substituent that does not contain a hydroxyl group, or a substituent that does not contain a hydroxyl group. Represents an alkoxy group that may be substituted or an aryl group that may have a substituent that does not contain a hydroxyl group, and R ²⁶ and R ²⁷ each independently have a hydrogen atom, a halogen atom, or a substituent that does not contain a hydroxyl group. Represents an optionally substituted alkyl group. ]
4. The electrostatic latent image developing toner according to claim 1, wherein the resin constituting the shell layer includes a repeating unit derived from an acrylonitrile monomer as a repeating unit having no hydroxyl group.
5. The electrostatic latent image developing toner according to claim 4, wherein the resin constituting the shell layer further includes a repeating unit derived from a styrene monomer as the repeating unit having no hydroxyl group.
6. The electrostatic latent image developing toner according to claim 1, wherein the resin constituting the shell layer is a crosslinked styrene resin.
7. The electrostatic latent image developing toner according to claim 1, wherein the resin constituting the shell layer is a crosslinked styrene-acrylonitrile resin.
8. 2. The electrostatic latent image developing toner according to claim 1, wherein carboxylate ions of the polyester resin in the core are bonded to alkali metal ions.
9. The electrostatic latent image developing toner according to claim 1, wherein the shell layer has a thickness of 1 nm to 20 nm.
10. The core is a ground core;
    The electrostatic latent image developing toner according to claim 9, wherein the core contains a crystalline polyester resin and an amorphous polyester resin as the polyester resin.
11. The non-crystalline polyester resin is a polymer of monomers containing one or more bisphenols and one or more dicarboxylic acids;
    The crystalline polyester resin includes one or more α, ω-alkanedicarboxylic acids having 6 to 12 carbon atoms and one or more α, ω-alkanediols having 2 to 6 carbon atoms. The toner for developing an electrostatic latent image according to claim 10, which is a polymer of
12. The electrostatic latent image developing toner according to claim 10, wherein the core contains a plurality of amorphous polyester resins having different softening points as the amorphous polyester resin.
13. A method for producing the electrostatic latent image developing toner according to claim 1,
    A core comprising a toner core containing a polyester resin and a shell layer covering the surface of the toner core at an area ratio of 60% or more and 80% or less and containing a resin composed only of one or more repeating units having no hydroxyl group; A preparation step of preparing shell particles;
    The core-shell particles are placed in a liquid containing alkali metal ions, and the liquid is kept at a temperature of 35 ° C. or higher and 45 ° C. or lower and a pH of 7.0 or higher and 11.0 or lower for a period of 30 minutes or longer and 4 hours or shorter. Surface treatment process to keep,
    A method for producing a toner for developing an electrostatic latent image, comprising: