JP2017167206A - Toner for electrostatic latent image development - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a toner for electrostatic latent image development that is excellent in heat-resistant storage property and low-temperature fixability.SOLUTION: A toner for electrostatic latent image development comprises a plurality of toner particles including a toner core 11 and a shell layer 12 that covers the surface of the toner core 11. The shell layer 12 includes a resin film that is formed mainly of an aggregate of resin particles 12a having a glass transition point of 50°C or more and 100°C or less and a circularity of 0.55 or more and 0.75 or less. When a toner not containing an external additive is exposed in a vapor of a RuOaqueous solution at a density of 5 mass% for 20 minutes, 50% or more and 80% or less of the surface area of the toner particle not containing an external additive is dyed with Ru.SELECTED DRAWING: Figure 2

Description

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

  Patent Document 1 discloses a method of forming a shell layer (coating layer) on the surface of the toner core by applying a mechanical impact force or a compressive shear force to the polymer fine particles attached to the surface of the toner core (toner base particle). ing.

JP-A-9-179336

  However, it is difficult to provide an electrostatic latent image developing toner that is excellent in both heat-resistant storage stability and low-temperature fixability only by the technique disclosed in Patent Document 1.

  The present invention has been made in view of the above problems, and an object thereof is to provide a toner for developing an electrostatic latent image that is excellent in heat-resistant storage stability and low-temperature fixability.

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 shell layer includes a resin film mainly composed of an aggregate of resin particles having a glass transition point of 50 ° C. or more and 100 ° C. or less and a circularity of 0.55 or more and 0.75 or less. When the toner in the absence of external additive is exposed to the vapor of a 5 mass% RuO ₄ aqueous solution for 20 minutes, 50% to 80% of the surface area of the toner particle in the absence of external additive. This region is stained with Ru.

  According to the present invention, it is possible to provide a toner for developing an electrostatic latent image that is excellent in heat-resistant storage stability and low-temperature fixability.

FIG. 3 is a diagram illustrating an example of a cross-sectional structure of toner particles (particularly, toner mother particles) included in the electrostatic latent image developing toner according to the embodiment of the present invention. It is a figure which shows the 1st example of the cross-section of a shell layer about the electrostatic latent image developing toner which concerns on embodiment of this invention. It is a figure which shows the 2nd example of the cross-section of a shell layer about the electrostatic latent image developing toner which concerns on embodiment of this invention. 4 is a photograph of toner particles taken with a scanning electron microscope (SEM) of the toner according to an exemplary embodiment of the present invention. It is a figure for demonstrating the measuring method of Ru dyeing | staining rate. It is a figure for demonstrating the adjustment method of the glass transition point (Tg) of resin which comprises a shell layer.

  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. Moreover, each measured value of an acid value and a hydroxyl value is a value measured according to "JIS (Japanese Industrial Standard) K0070-1992" unless otherwise specified. Moreover, each measured value of a number average molecular weight (Mn) and a mass average molecular weight (Mw) is the value measured using the gel permeation chromatography, if not prescribed | regulated at all.

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 the exemplary 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 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, ferrite), or the carrier core may be formed of a resin in which magnetic particles are dispersed. Further, magnetic particles may be dispersed in the resin layer covering the carrier core. In order to form a high-quality image, the amount of toner in the two-component developer is preferably 5 parts by mass or more and 15 parts by mass or less with respect to 100 parts by mass of the carrier. The positively chargeable toner contained in the two-component developer is positively charged by friction with the carrier.

  The toner particles contained in the toner according to the exemplary 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 exemplary 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 electrostatic latent image is formed on a photoconductor (for example, a surface layer portion of a photoconductor drum) based on image data. Next, the formed electrostatic latent image is developed using a developer containing toner. In the developing process, toner (for example, toner charged by friction with a carrier or blade) 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 converted into an electrostatic latent image. A toner image is formed on the photoreceptor by adhering. In the subsequent transfer step, the toner image on the photosensitive member is transferred to an intermediate transfer member (for example, a transfer belt), and then the toner image on the intermediate transfer member is further transferred to a recording medium (for example, paper). Thereafter, the toner is heated and pressed by a fixing device (fixing method: nip formed by a heating roller and a pressure roller) 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 toner according to the exemplary 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 shell layer includes a resin film mainly composed of an aggregate of resin particles having a glass transition point of 50 ° C. or more and 100 ° C. or less and a circularity of 0.55 or more and 0.75 or less. When the resin film contains two or more types of resin particles, 50% by mass or more of the resin particles have a glass transition point of 50 ° C. or more and 100 ° C. or less and a circularity of 0.55 or more and 0.75 or less. Resin particles (hereinafter referred to as film-forming heat-resistant particles). Further, when the toner without external additives is exposed for 20 minutes in the vapor of a 5 mass% RuO ₄ (ruthenium tetroxide) aqueous solution, the toner base particles (toner particles without external additives) Of the surface area, 50% to 80% of the area is stained with Ru. Hereinafter, the ratio of the surface area of toner base particles that are dyed with Ru (ruthenium) when the toner without external additives is exposed to the vapor of a 5 mass% RuO ₄ aqueous solution for 20 minutes is represented by Ru dyeing. It is described as a rate. In addition, the resin particles constituting the resin film covering the surface of the toner core are referred to as shell particles.

  The toner having the above basic structure is excellent in both heat-resistant storage stability and low-temperature fixability. Hereinafter, the operation and effect of the basic configuration will be described in detail.

  In order to improve the low temperature fixability of the toner while maintaining sufficient toner durability, the Ru dyeing rate of the toner is 50% or more and 80% or less, and the glass transition point of the shell particles is 50 ° C. or more and 100 ° C. The inventors have found that it is effective that the circularity of the shell particles is 0.55 or more and 0.75 or less. Specifically, a resin film (hereinafter referred to as a heat-resistant particle assembly film) mainly composed of an aggregate of film-formed heat-resistant particles (resin particles having a glass transition point of 50 ° C. or more and 100 ° C. or less and a circularity of 0.55 or more and 0.75 or less). By covering the surface of the toner core, it is possible to achieve both heat resistant storage stability and low-temperature fixability of the toner. Further, it becomes easy to impart sufficient resistance to the stress in the developing device to the toner. Of the shell particles, 70% by mass or more of the particles are preferably film-formed heat-resistant particles, and 100% by mass of the particles are more preferably film-formed heat-resistant particles. If the glass transition point of the shell particles is too high, it becomes difficult to form a shell particle aggregate into a film, and the shell particles tend to be separated one by one.

A resin that is dyed with Ru when exposed to a vapor of a 5 mass% RuO ₄ aqueous solution for 20 minutes (hereinafter referred to as a Ru-dyed resin) is a non-crystalline resin having a styrene skeleton or an ethylene skeleton (crystallized). (For example, see Document A below).
Reference A: Tadafumi Komoto, Journal of Rubber Society, 1995, Vol. 68, No. 12

  The Ru dye resin has a low surface free energy and tends to undergo phase transition as compared with a toner core material (for example, polyester resin). By appropriately covering the surface of the toner core with the Ru dye resin film, sufficient toner releasability with respect to the heating roller of the fixing device can be secured, and the toner fixability with respect to the recording medium (for example, paper) can be improved. Is possible. It is considered that the adhesive force between the recording medium and the toner becomes stronger due to the toner throwing effect on the recording medium.

  Hereinafter, the configuration of toner particles contained in the toner having the above basic configuration will be described with reference to FIGS. FIG. 1 is a diagram showing an example of the configuration of toner particles (particularly toner mother particles) contained in the toner according to the embodiment of the present invention. 2 and 3 are enlarged views of the surface of the toner base particles.

  A toner base particle 10 shown in FIG. 1 includes a toner core 11 and a shell layer 12 formed on the surface of the toner core 11. Shell layer 12 includes a resin film (specifically, a film mainly composed of an aggregate of resin particles). The shell layer 12 partially covers the surface of the toner core 11.

  For example, as shown in FIG. 2, the resin film included in the shell layer 12 may be composed of only an aggregate of ellipsoidal resin particles 12 a. The resin particles 12a are film-forming heat-resistant particles (resin particles having a glass transition point of 50 ° C. or more and 100 ° C. or less and a circularity of 0.55 or more and 0.75 or less). The resin particles 12a are made of Ru dye resin.

  Further, the resin film included in the shell layer 12 may include two types of resin particles 12a and 12b having different monomer compositions as shown in FIG. 3, for example. For example, when the resin particles 12a are film-formed heat-resistant particles composed of Ru-dyed resin, the resin particles 12b may be film-formed heat-resistant particles or may not be film-formed heat-resistant particles. Further, the resin particles 12b may be particles composed of Ru dye resin, or may not be particles composed of Ru dye resin. The shape of the resin particle 12a is, for example, an ellipsoid. The resin particles 12b may have a spherical shape or an ellipsoidal shape. As the resin particles 12b, for example, resin particles that are more easily positively charged than the resin particles 12a (film-formed heat-resistant particles) are preferable.

  In the above basic configuration, each of the methods for measuring the Tg (glass transition point) of the shell particles, the circularity of the shell particles, and the Ru staining rate is the same method as in the examples described later or an alternative method thereof. When the toner particles include an external additive, the Ru dyeing rate is measured after the external additive is removed. Examples of a method for removing the external additive adhering to the toner base particles include a method of dissolving the external additive using a solvent (more specifically, an alkaline solution or the like), or a toner using an ultrasonic cleaner. A method of removing the external additive from the particles is mentioned.

Hereinafter, a method for measuring the Ru staining rate will be described with reference to FIGS. First, the toner base particles (powder) are exposed to the vapor of a 5 mass% RuO ₄ aqueous solution for 20 minutes to dye the toner base particles with Ru (ruthenium). Subsequently, the dyed toner base particles are photographed using a scanning electron microscope (SEM) to obtain, for example, a reflected electron image of the toner base particles as shown in FIG. Subsequently, image analysis of the reflected electron image is performed using image analysis software, and a luminance value histogram (vertical axis: frequency (number), horizontal axis: luminance value) indicating the luminance value distribution of the image data is obtained. Specifically, for example, waveforms L0 to L2 as shown in FIG. 5 are obtained by image analysis. In FIG. 5, a waveform L1 corresponds to a non-stained waveform indicating a distribution (normal distribution) of luminance values in a non-stained region (a region not stained with Ru) in the surface region of the toner base particles. The waveform L2 corresponds to a staining waveform indicating the distribution of luminance values (normal distribution) in the stained region (region stained with Ru) in the surface region of the toner base particles. The waveform L0 corresponds to a combined waveform of the waveform L1 and the waveform L2. When the area of the waveform L1 is represented by R _C and the area of the waveform L2 is represented by R _S , the Ru staining rate (unit:%) is expressed by the formula “Ru staining rate = 100 × R _S / (R _C + R _S )”. It is represented by

  Next, with reference to FIG. 6, the adjustment method of the glass transition point (Tg) of resin which comprises a shell particle is demonstrated. The glass transition point (Tg) of the resin can be adjusted, for example, by changing the type or amount (blending ratio) of the resin component (monomer). For example, when only the amount of n-butyl acrylate (BA) is changed among the raw material monomers used for the synthesis of the S-BA copolymer (S: styrene, BA: n-butyl acrylate), FIG. As shown in FIG. 4, the inventors confirmed that the glass transition point (Tg) of the resin obtained and the BA ratio (= BA mass / total mass of raw material monomers) are generally proportional. Specifically, the glass transition point (Tg) of the resin tends to decrease as the BA ratio increases.

In the above basic structure, the film-forming heat-resistant particles are preferably substantially composed of a monomer polymer (resin) containing one or more vinyl compounds. The 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, vinyl chloride, acrylic acid, methyl acrylate). Methacrylic acid, methyl methacrylate, acrylonitrile, styrene, etc.). 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).

  The resin constituting the film-forming heat-resistant particles preferably has, for example, a repeating unit derived from a nitrogen-containing vinyl compound, and particularly preferably has a repeating unit represented by the following formula (1).

In formula (1), R ¹¹ and R ¹² each independently represent a hydrogen atom, a halogen atom, or an alkyl group that may have a substituent. R ³¹ , R ³² , and R ³³ each independently represent a hydrogen atom, an alkyl group that may have a substituent, or an alkoxy group that may have a substituent. R ² represents an alkylene group which may have a substituent. R ¹¹ and R ¹² are each independently preferably a hydrogen atom or a methyl group, particularly preferably a combination in which R ¹¹ represents a hydrogen atom and R ¹² represents a hydrogen atom or a methyl group. R ³¹ , R ³² , and R ³³ are each independently preferably an alkyl group having 1 to 8 carbon atoms, and includes a methyl group, an ethyl group, an n-propyl group, an iso-propyl group, and an n-butyl group. The group or iso-butyl group is particularly preferred. R ² is preferably an alkylene group having 1 to 6 carbon atoms, particularly preferably a methylene group or an ethylene group. In the repeating unit derived from 2- (methacryloyloxy) ethyltrimethylammonium chloride, R ¹¹ is a hydrogen atom, R ¹² is a methyl group, R ² is an ethylene group, and each of R ^{31 to} R ³³ is a methyl group. Respectively.

  The resin constituting the film-forming heat-resistant particles preferably has, for example, a repeating unit derived from a styrene monomer, and particularly preferably has a repeating unit represented by the following formula (2).

In formula (2), R ^{41 to} R ⁴⁵ are each independently a hydrogen atom, a halogen atom, a hydroxyl group, an alkyl group that may have a substituent, an alkoxy group that may have a substituent, or a substituent. Represents an alkoxyalkyl group which may have a substituent or an aryl group which may have a substituent. R ⁴⁶ and R ⁴⁷ each independently represent a hydrogen atom, a halogen atom, or an alkyl group which may have a substituent. R ^{41 to} R ⁴⁵ 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 ⁴⁶ and R ⁴⁷ are each independently preferably a hydrogen atom or a methyl group, particularly preferably a combination in which R ⁴⁷ represents a hydrogen atom and R ⁴⁶ represents a hydrogen atom or a methyl group. In the repeating unit derived from 2- (ethoxymethyl) styrene, R ⁴¹ represents an ethoxymethyl group (C ₂ H ₅ OCH ₂ —), and each of R ^{42 to} R ⁴⁷ represents a hydrogen atom.

  The inventors have found that when the resin constituting the film-forming heat-resistant particles has one or more repeating units having an alcoholic hydroxyl group, the toner core can be easily coated on the shell layer with a high coverage. In order for the toner to have the above basic structure, the resin constituting the film-forming heat-resistant particles preferably has one or more repeating units having an alcoholic hydroxyl group, and the repeating unit represented by the following formula (3) It is particularly preferable to have it.

In formula (3), R ⁵¹ and R ⁵² each independently represents a hydrogen atom, a halogen atom, or an alkyl group which may have a substituent. R ⁶ represents an alkylene group which may have a substituent. R ⁵¹ and R ⁵² are each independently preferably a hydrogen atom or a methyl group, particularly preferably a combination in which R ⁵¹ represents a hydrogen atom and R ⁵² represents a hydrogen atom or a methyl group. R ⁶ is preferably an alkylene group having 1 to 6 carbon atoms, and more preferably an alkylene group having 1 to 4 carbon atoms. In the repeating unit derived from 2-hydroxyethyl methacrylate (HEMA), R ⁵¹ is a hydrogen atom, R ⁵² is a methyl group, and R ⁶ is a butylene group (—CH ₂ CH (C ₂ H ₅ ) —). Respectively.

  In order to achieve both heat-resistant storage stability and low-temperature fixability of the toner, the resin constituting the film-forming heat-resistant particles includes a repeating unit represented by the formula (1), a repeating unit represented by the formula (2), and It is preferable to have one or more repeating units selected from the group consisting of repeating units represented by formula (3).

  In order to achieve both the heat-resistant storage stability and the low-temperature fixability of the toner, it is preferable that the resin particles are bonded by a physical force in the heat-resistant particle aggregate film. By forming a portion (crushing point) that is easily crushed in the film, it becomes possible to improve the low-temperature fixability of the toner while maintaining the durability of the toner. The heat-resistant particle aggregate film having such a structure can be obtained, for example, by using resin particles as the shell material and forming the material (resin particles) into a film by dry mechanical treatment.

  In the toner having the above basic configuration, the shell layer contains film-formed heat-resistant particles having a circularity of 0.55 to 0.75. The inventors have found that the heat-resistant storage stability and the low-temperature fixability of the toner can be made compatible by forming a shell layer on the film-formed heat-resistant particles having such circularity (see Tables 1 to 4 described later). . It is considered that the reason why such an experimental result was obtained is that the film formation by the aggregate of resin particles is moderately advanced in the shell layer. If the film formation by the aggregate of resin particles proceeds too much or insufficiently, it is considered that sufficient heat-resistant storage stability of the toner cannot be ensured. In order to make the roundness of the shell particles 0.55 or more and 0.75 or less, physical force (more specifically, compression shear force or mechanical shock) is applied to the resin particles on the toner core by, for example, mechanical treatment. It is preferable that the resin particles are bonded to each other with a physical force.

  In order to achieve both heat-resistant storage stability and low-temperature fixability of the toner, the glass transition point (Tg) of the binder resin mainly constituting the toner core (specifically, at a ratio of 50% by mass or more) is 20 ° C. or higher. It is preferable that it is 60 degrees C or less. In order to achieve both heat-resistant storage stability and low-temperature fixability of the toner, the softening point (Tm) of the binder resin mainly constituting the toner core (specifically, at a ratio of 50% by mass or more) is 80 ° C. or higher and 145 ° C. The following is preferable. In addition, each measuring method of Tg and Tm is the same method as the Example mentioned later, or its alternative method.

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, materials suitable for forming toner particles will be described. Resins suitable as the toner core material and shell material are as follows.

<Preferable thermoplastic resin>
Examples of the thermoplastic resin constituting the toner particles (particularly, the toner core and the shell layer) include, for example, a styrene resin, an acrylic resin (more specifically, an acrylic ester polymer or a methacrylic ester polymer), Olefin resins (more specifically, polyethylene resins or polypropylene resins), vinyl chloride resins, polyvinyl alcohol, vinyl ether resins, N-vinyl resins, polyester resins, polyamide resins, or urethane resins are preferred. A copolymer of each of these resins, that is, a copolymer in which an arbitrary repeating unit is introduced into the resin (specifically, a styrene-acrylic acid resin or a styrene-butadiene resin) is also used as a toner. It is preferable as a thermoplastic resin constituting the particles.

  The thermoplastic resin can be obtained by addition polymerization, copolymerization, or condensation polymerization of one or more thermoplastic monomers. The thermoplastic monomer is a monomer that becomes a thermoplastic resin by homopolymerization (more specifically, an acrylic acid monomer or a styrene monomer), or a monomer that becomes a thermoplastic resin by condensation polymerization (for example, by condensation polymerization). A combination of a polyhydric alcohol and a polyhydric carboxylic acid to be a polyester resin.

  The styrene-acrylic acid resin is a copolymer of one or more styrene monomers and one or more acrylic monomers. In order to synthesize a styrene-acrylic acid resin, for example, a styrene monomer and an acrylic acid monomer as shown below can be suitably used. By using an acrylic acid monomer having a carboxyl group, a carboxyl group can be introduced into the styrene-acrylic acid resin. Further, by using a monomer having a hydroxyl group (more specifically, p-hydroxystyrene, m-hydroxystyrene, (meth) acrylic acid hydroxyalkyl ester, or the like), the hydroxyl group can be introduced into the styrene-acrylic acid resin. . The acid value of the styrene-acrylic acid resin obtained can be adjusted by adjusting the amount of the acrylic acid monomer used. Moreover, the hydroxyl value of the styrene-acrylic acid-type resin obtained can be adjusted by adjusting the usage-amount of the monomer which has a hydroxyl group.

  Suitable examples of the styrenic monomer include styrene, α-methylstyrene, 4-methylstyrene, 4-ethylstyrene, 4-butylstyrene, 4-methoxystyrene, 3-hydroxystyrene, 4-hydroxystyrene, or halogenated. Styrene is mentioned.

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

  The polyester resin is obtained by polycondensation of one or more polyhydric alcohols and one or more polyhydric carboxylic acids. As the alcohol for synthesizing the polyester resin, for example, dihydric alcohols (more specifically, diols or bisphenols) as shown below or trihydric or higher alcohols can be suitably used. As the carboxylic acid for synthesizing the polyester resin, for example, divalent carboxylic acids or trivalent or higher carboxylic acids as shown below can be suitably used. Moreover, when synthesizing the polyester resin, the acid value and the hydroxyl value of the polyester resin can be adjusted by changing the amount of alcohol used and the amount of carboxylic acid used. When the molecular weight of the polyester resin is increased, the acid value and hydroxyl value of the polyester resin tend to decrease.

  Suitable examples of diols include ethylene glycol, diethylene glycol, triethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, neopentyl glycol, 1,4-butenediol, Examples include 1,5-pentanediol, 1,6-hexanediol, 1,4-cyclohexanedimethanol, di1,2-propanediol, polyethylene glycol, poly1,2-propanediol, or polytetramethylene glycol.

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

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

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

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

  Next, the toner core (binder resin and internal additive), shell layer, and external additive will be described in order. Depending on the toner application, unnecessary components (for example, an internal additive or an external additive) 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 property (reactivity) 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 order to achieve both the heat-resistant storage stability and the low-temperature fixability of the toner, the toner core preferably contains the above-mentioned “suitable thermoplastic resin” as a binder resin. It is more preferable to contain a polyester resin. The crystalline polyester resin has a characteristic that when heated in a solid state, it melts at the glass transition point (Tg) and the viscosity rapidly decreases. Further, the crystalline polyester resin and the amorphous polyester resin are easily compatible. In order to achieve both the heat-resistant storage stability and the low-temperature fixability of the toner, the toner core includes, as a binder resin, one or more crystalline polyester resins and one or more amorphous polyester resins that are melt-kneaded. It is particularly preferable to contain it.

  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.

(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 montanate ester wax or castor wax; fats such as deoxidized carnauba wax The wax portion of the ester or the whole was deoxygenated can be suitably used. One type of release agent may be used alone, or multiple types of release agents may be used in combination.

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

(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 enhanced. 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 toner according to the exemplary embodiment has the basic configuration described above. The shell layer includes a resin film mainly composed of an aggregate of film-forming heat-resistant particles (glass particles having a glass transition point of 50 ° C. or more and 100 ° C. or less and a circularity of 0.55 or more and 0.75 or less). The resin constituting the film-forming heat-resistant particles is preferably a monomer polymer containing one or more vinyl compounds, and more preferably a monomer polymer containing one or more nitrogen-containing vinyl compounds.

  In order to obtain a toner excellent in heat-resistant storage stability and low-temperature fixability, it is preferable that one or more repeating units derived from a styrenic monomer are contained in the resin constituting the film-forming heat-resistant particles. As the styrene monomer, styrene, α-methylstyrene, 4-methylstyrene, 4-tert-butylstyrene, 4-methoxystyrene, 4-bromostyrene, or 3-chlorostyrene can be preferably used.

  In order to obtain a toner excellent in chargeability, heat-resistant storage stability, and low-temperature fixability, it is preferable that one or more repeating units having an alcoholic hydroxyl group are contained in the resin constituting the film-forming heat-resistant particles. As a monomer for introducing a repeating unit having an alcoholic hydroxyl group into the resin constituting the film-forming heat-resistant particles, (meth) acrylic acid 2-hydroxyalkyl ester is preferable, 2-hydroxyethyl acrylate (HEA), 2-hydroxypropyl acrylate (HPA), 2-hydroxyethyl methacrylate (HEMA), or 2-hydroxypropyl methacrylate can be suitably used.

  In order to obtain a toner having excellent chargeability, heat-resistant storage stability, and low-temperature fixability, one or more repeating units derived from a (meth) acryloyl group-containing quaternary ammonium compound in the resin constituting the film-forming heat-resistant particles Is preferably included. Examples of the (meth) acryloyl group-containing quaternary ammonium compound include (meth) acrylamidoalkyltrimethylammonium salts (more specifically, (3-acrylamidopropyl) trimethylammonium chloride) or (meth) acryloyloxyalkyltrimethyl. An ammonium salt (more specifically, 2- (methacryloyloxy) ethyltrimethylammonium chloride or the like) can be preferably used.

[External additive]
Inorganic particles may be attached to the surface of the toner base particles as an external additive. For example, a toner base particle (specifically, a powder containing a plurality of toner base particles) and an external additive (specifically, a powder containing a plurality of external additive particles) are stirred together to physically The external additive adheres (physically bonds) to the surface of the toner base particles by force. The external additive is used, for example, to improve the fluidity or handleability of the toner. In order to improve the fluidity or handleability of the toner, the amount of the external additive is preferably 0.5 parts by mass or more and 10 parts by mass or less with respect to 100 parts by mass of the toner base particles. In order to improve the fluidity or handleability of the toner, the particle diameter of the external additive is preferably 0.01 μm or more and 1.0 μm or less.

  As the external additive particles, particles of silica particles or metal oxides (more specifically, alumina, titanium oxide, magnesium oxide, zinc oxide, strontium titanate, barium titanate, etc.) can be preferably used. One type of external additive may be used alone, or a plurality of types of external additives may be used in combination.

[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 reacted in the liquid to form a shell layer (cured resin layer) 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 exemplary embodiment will be further described based on a more specific example.

(Preparation of toner core)
In order to easily obtain a suitable toner core, the toner core is preferably produced by an aggregation 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 and an internal additive (for example, at least one of a colorant, a release agent, a charge control agent, and magnetic powder) are mixed. Subsequently, the obtained mixture is melt-kneaded. Subsequently, the obtained melt-kneaded product is pulverized and 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 agglomerated in an aqueous medium containing fine particles of a binder 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, monomers containing one or more vinyl compounds (for example, styrene, n-butyl acrylate, 2-hydroxyethyl methacrylate, and 2- (methacryloyloxy) ethyltrimethylammonium chloride). ). The glass transition point of the polymer constituting the resin particles is 50 ° C. or higher and 100 ° C. or lower. The circularity of the resin particles contained in the suspension may exceed 0.75.

  The toner core or the like may be added to an aqueous medium at room temperature, or may be added to an aqueous medium adjusted to a predetermined temperature. The appropriate addition amount of the shell material can be calculated based on the specific surface area of the toner core. In addition to the toner core and the like, a polymerization accelerator may be added to the aqueous medium.

  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, 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, 40 ° C. 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 dispersion liquid of toner base particles (hereinafter referred to as pre-treatment particles) before performing mechanical treatment described later is obtained.

  Subsequently, the dispersion of the pre-treatment particles is cooled to, for example, room temperature (about 25 ° C.). Subsequently, the dispersion of pre-treated particles is filtered, for example using a Buchner funnel. Thereby, the pre-treatment particles are separated from the liquid (solid-liquid separation), and wet cake-like pre-treatment particles are obtained. Subsequently, the wet pre-treatment particles obtained are washed. Subsequently, the washed pre-treated particles are dried.

  Subsequently, for example, using a mixer (more specifically, “Hybridization System (registered trademark)” manufactured by Nara Machinery Co., Ltd., “Mechanofusion (registered trademark)” manufactured by Hosokawa Micron Corporation, etc.) The pre-treatment particles are subjected to mechanical treatment to apply physical force to the resin particles present on the surface of the toner core. Each resin particle is deformed by receiving a physical force, and the resin particles are bonded by a physical force. By the mechanical treatment, an aggregate of resin particles is formed into a film on the surface of the toner core. As a result, a film having a form in which resin particles are two-dimensionally connected (a film having a granular feeling) is formed as a shell layer, and a powder of toner base particles is obtained.

  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.

  The contents 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. Moreover, even if it does not adjust pH of a liquid, when reaction for forming a shell layer advances favorably, you may omit a pH adjustment process. 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. The toner core material and the shell material are not limited to the above-described compounds (such as various monomers for synthesizing the resin). For example, if necessary, a derivative of the aforementioned compound may be used as the toner core material or shell material, or a prepolymer may be used instead of the monomer. Further, in order to obtain the above-mentioned 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-16 and TB-1 to TB-7 (each toner for developing an electrostatic latent image) according to Examples or Comparative Examples. Tables 2 and 3 show suspensions A-1 to A-9 and B-1 to B-2 used for manufacturing the toners shown in Table 1. “Emulsifier” in Table 2 is an anionic surfactant (“Latemul (registered trademark) WX” manufactured by Kao Corporation). “Initiator” in Table 2 is potassium persulfate.

  Hereinafter, the production methods, evaluation methods, and evaluation results of the toners TA-1 to TA-16 and TB-1 to TB-7 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. 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 and Mp>
As a measuring device, a differential scanning calorimeter (“DSC-6220” manufactured by Seiko Instruments Inc.) was used. The Tg and Mp of the sample were determined by measuring the endothermic curve of the sample (eg, resin) using a measuring device. Specifically, 15 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 10 ° C. to 150 ° C. at a rate of 10 ° C./min (RUN1). Thereafter, the temperature of the measurement part was lowered from 150 ° C. to 10 ° C. at a rate of 10 ° C./min. Subsequently, the temperature of the measurement part was again increased from 10 ° C. to 150 ° 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 Mp and Tg of the sample were 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. 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.

[Toner Production Method]
(Synthesis of crystalline polyester resin)
In a 5 L four-necked flask equipped with a thermometer (thermocouple), dehydration tube, nitrogen introduction tube, and stirring device, 1,4-butanediol 990 g (84 mol parts), 1,6-hexanediol 242 g (11 mol parts), 1480 g (100 mol parts) of fumaric acid, and 2.5 g of 1,4-benzenediol were added. Subsequently, while stirring the flask contents, the temperature of the flask contents was raised to 170 ° C., and the flask contents were reacted at that temperature (170 ° C.) for 5 hours. Subsequently, the flask contents were heated and reacted at a temperature of 210 ° C. for an additional 1.5 hours (90 minutes). Subsequently, the contents of the flask were reacted for 1 hour in a reduced pressure atmosphere (pressure 8 kPa) and a temperature of 210 ° C.

  Subsequently, the atmosphere in the flask was returned to the atmospheric pressure, and 69 g (2.8 mol parts) of styrene and 54 g (2.2 mol parts) of n-butyl methacrylate were placed in the flask. Subsequently, the flask contents were heated and reacted at 210 ° C. for 1.5 hours (90 minutes). Subsequently, the contents of the flask were reacted for 1 hour in a reduced pressure atmosphere (pressure 8 kPa) and a temperature of 210 ° C. As a result, Tm (softening point) 88.8 ° C., Mp (melting point) 82 ° C., acid value 3.1 mgKOH / g, hydroxyl value 19 mgKOH / g, Mw (mass average molecular weight) 27500, Mn (number average molecular weight) 3620 A crystalline polyester resin was obtained.

(Synthesis of non-crystalline polyester resin)
In a 5 L four-necked flask equipped with a thermometer (thermocouple), dehydration tube, nitrogen introduction tube, and stirrer, 1700 g of bisphenol A propylene oxide adduct, 650 g of bisphenol A ethylene oxide adduct, n- 500 g of dodecenyl succinic anhydride, 400 g of terephthalic acid, and 4 g of dibutyltin oxide were added. Subsequently, the contents of the flask were reacted at a temperature of 220 ° C. for 9 hours. Subsequently, the flask contents were reacted in a reduced pressure atmosphere (pressure 8.3 kPa) until the Tm of the reaction product (resin) reached a predetermined temperature (124.8 ° C.). As a result, Tm (softening point) 124.8 ° C., Tg (glass transition point) 57.2 ° C., acid value 6 mgKOH / g, hydroxyl value 41 mgKOH / g, Mw (mass average molecular weight) 109475, Mn (number average molecular weight) 3737 of an amorphous polyester resin was obtained.

(Preparation of suspension A-1)
A 1 L three-necked flask equipped with a thermometer and a stirring blade was set in a water bath. Inside the flask, 875 mL of ion-exchanged water having a temperature of 30 ° C. and an anionic surfactant (“Latemul WX” manufactured by Kao Corporation) Ingredients: Sodium polyoxyethylene alkyl ether sulfate, solid content concentration: 26% by mass) and 75 mL. Thereafter, the temperature in the flask was raised to 80 ° C. using a water bath. Subsequently, two kinds of liquids (first liquid and second liquid) were dropped into the contents of the flask at 80 ° C. over 5 hours. The first liquid is 18 g of styrene (S), 2 g of n-butyl acrylate (BA), 0.1 g of 2-hydroxyethyl methacrylate (HEMA), and 2- (methacryloyloxy) ethyltrimethylammonium chloride (METAC). ) (Alfa Aesar) 0.1g. The second liquid was a solution in which 0.5 g of potassium persulfate was dissolved in 30 mL of ion exchange water. Subsequently, the temperature in the flask was kept at 80 ° C. for another 2 hours to polymerize the flask contents. As a result, a resin fine particle suspension A-1 (solid content concentration: 2% by mass) was obtained.

(Preparation of suspension A-2)
The method for preparing the suspension A-2 (solid content concentration: 2% by mass) was the same as the preparation of the suspension A-1, except that the amount of 2-hydroxyethyl methacrylate (HEMA) used was changed from 0.1 g to 4.0 g. It was the same as the method.

(Preparation of suspension A-3)
The preparation method of the suspension A-3 (solid content concentration: 2% by mass) was as follows. Regarding the amount of each material used, 18 g of styrene (S) was changed to 16 g, and 2 g of n-butyl acrylate (BA) was changed to 4 g. Except for the change, the procedure was the same as the method for preparing the suspension A-1.

(Preparation of suspension A-4)
The suspension A-4 (solid content concentration: 2 mass%) was prepared by changing the amount of styrene (S) used from 18 g to 20 g and not using n-butyl acrylate (BA). It was the same as the preparation method of A-1.

(Preparation of suspension A-5)
In the preparation method of suspension A-5 (solid content concentration: 2% by mass), the amount of anionic surfactant (Latemul WX) used was changed from 75 mL to 30 mL, and the amount of potassium persulfate used was changed from 0.5 g to 0.001. Except for changing to 1 g, it was the same as the method for preparing the suspension A-1.

(Preparation of suspension A-6)
The method for preparing the suspension A-6 (solid content concentration: 2% by mass) was the same as the method for preparing the suspension A-1, except that 2- (methacryloyloxy) ethyltrimethylammonium chloride (METAC) was not used. It was.

(Preparation of suspension A-7)
The suspension A-7 (solid content concentration: 2% by mass) was prepared as a first liquid mixture of the above monomer composition (S: 18 g, BA: 2 g, HEMA: 0.1 g, METAC: 0.00. 1 g), 20 g of 2- (ethoxymethyl) styrene (EMST), 0.1 g of 2-hydroxyethyl methacrylate (HEMA), 2- (methacryloyloxy) ethyltrimethylammonium chloride (METAC) (Alfa Aesar) (Product made) It was the same as the preparation method of suspension A-1 except having used the liquid mixture with 0.1g.

(Preparation of suspension A-8)
The preparation method of suspension A-8 (solid content concentration: 2% by mass) is as follows. Regarding the amount of each material used, 18 g of styrene (S) is changed to 15 g, and 2 g of n-butyl acrylate (BA) is changed to 5 g. Except for the change, the procedure was the same as the method for preparing the suspension A-1.

(Preparation of suspension A-9)
The suspension A-9 (solid content concentration: 2% by mass) was prepared by using 20 g of 4-chlorostyrene (CS) instead of 18 g of styrene (S) and 2 g of n-butyl acrylate (BA). This was the same as the method for preparing the suspension A-1.

(Preparation of suspension B-1)
In a 1 L three-necked flask equipped with a thermometer, a condenser tube, a nitrogen inlet tube, and a stirring blade, 90 g of isobutanol, 25 g of styrene (S), 65 g of methyl methacrylate (MMA), and acrylic acid n 10 g of butyl (BA), 0.1 g of 2-hydroxyethyl methacrylate (HEMA), 30 g of 2- (methacryloyloxy) ethyltrimethylammonium chloride (METAC) (manufactured by Alfa Aesar), 2,2′-azobis 6 g of (2-methyl-N- (2-hydroxyethyl) propionamide) (“VA-086” manufactured by Wako Pure Chemical Industries, Ltd.) was added. Subsequently, the contents of the flask were reacted for 3 hours under conditions of a nitrogen atmosphere and a temperature of 80 ° C. Thereafter, 3 g of 2,2′-azobis (2-methyl-N- (2-hydroxyethyl) propionamide) (“VA-086” manufactured by Wako Pure Chemical Industries, Ltd.) was added to the flask, and the nitrogen atmosphere and temperature were increased. The flask contents were further reacted for 3 hours under the condition of 80 ° C. to obtain a liquid containing a polymer. Subsequently, the liquid containing the obtained polymer was dried under a reduced pressure atmosphere and a temperature of 150 ° C. Subsequently, the dried polymer was crushed to obtain a positively chargeable resin.

  Subsequently, 200 g of the positively chargeable resin obtained as described above and 184 mL of ethyl acetate (“Ethyl acetate special grade” manufactured by Wako Pure Chemical Industries, Ltd.) were mixed with a mixing device (“Hibismix (registered trademark)” manufactured by Primics Co., Ltd. ) 2P-1 type "). Subsequently, using the mixing apparatus, the contents of the container were stirred for 1 hour at a rotation speed of 20 rpm to obtain a highly viscous solution. Thereafter, an aqueous solution of ethyl acetate or the like (specifically, 18 mL of 1N hydrochloric acid and an anionic surfactant (“Emar (registered trademark) 0” manufactured by Kao Corporation, ingredient: sodium lauryl sulfate) 20 g) was added to the resulting highly viscous solution. And 16 g of ethyl acetate (“Ethyl acetate special grade” manufactured by Wako Pure Chemical Industries, Ltd.) dissolved in ion-exchanged water 562 g) were added. As a result, a resin fine particle suspension B-1 (solid content concentration: 20% by mass) was obtained.

(Preparation of suspension B-2)
Suspension B-2 (solid content concentration: 20% by mass) is prepared by using 25 g of styrene (S) to 0 g (not used) and 65 g of methyl methacrylate (MMA) to 100 g with respect to the amount of each material used. Suspension B, except that 10 g of n-butyl acrylate (BA) was changed to 12 g, and 30 g of 2- (methacryloyloxy) ethyltrimethylammonium chloride (METAC) (Alfa Aesar) was changed to 0.1 g. -1 was the same as the preparation method.

  Regarding the resin fine particles contained in each of the suspensions A-1 to A-9 and B-1 to B-2 prepared as described above, the number average particle diameter and the glass transition point (Tg) are shown in Tables 2 and 3. It was as shown in. In each of Tables 2 and 3, “particle diameter” means the number average particle diameter. A transmission electron microscope (TEM) was used for the measurement of the number average particle diameter. For example, regarding the resin fine particles contained in the suspension A-1, the number average particle diameter was 35 nm, and the glass transition point (Tg) was 70 ° C.

(Production of toner core)
Using an FM mixer ("FM-20B" manufactured by Nippon Coke Kogyo Co., Ltd.), 20 parts by mass of the first binder resin (crystalline polyester resin synthesized by the above procedure) and the second binder resin (the above procedure). 80 parts by mass of the non-crystalline polyester resin synthesized in 1), 6 parts by mass of carbon black (“MA100” manufactured by Mitsubishi Chemical Corporation), and a release agent (ester wax: “Nissan Electol” (registered trademark) manufactured by NOF Corporation) ) WEP-9 ") 4 parts by weight.

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 6 kg / hour, a shaft rotation speed of 160 rpm, and a set temperature (cylinder temperature) of 120 ° C. Was melt kneaded. Thereafter, the obtained kneaded material was cooled. Subsequently, the cooled kneaded material was coarsely pulverized using a pulverizer (“Rohtoplex (registered trademark)” manufactured by Hosokawa Micron Corporation). Subsequently, the obtained coarsely pulverized product was finely pulverized using a pulverizer (“Turbo Mill RS type” manufactured by Freund Turbo 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 7 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 (suspension shown in Table 1 defined for each toner) was added to the flask in the amount shown in Table 1. For example, in the production of toner TA-1, 220 g of suspension A-1 (solid content concentration: 2% by mass) was added to the flask as a shell material. In the production of toner TA-11, as shell materials, 220 g of suspension A-6 (solid content concentration: 2 mass%) and 3 g of suspension B-1 (solid content concentration: 20 mass%) were respectively placed in the flask. Added.

  Subsequently, 300 g of a toner core (toner core produced by the above procedure) was added to the flask. Subsequently, while stirring the flask contents at a rotation speed of 100 rpm, the temperature in the flask was increased to 70 ° C. at a rate of 1 ° C./min. Subsequently, the flask contents were stirred for 2 hours under the conditions of a temperature of 70 ° C. and a rotation speed of 100 rpm.

  Subsequently, sodium hydroxide was added to the flask to adjust the pH of the flask contents to 7. Subsequently, the flask contents were cooled until the temperature reached room temperature (about 25 ° C.) to obtain a dispersion containing pre-treatment particles (toner base particles before performing mechanical treatment described later).

(Washing process)
The pre-treatment particle dispersion obtained as described above was filtered (solid-liquid separation) using a Buchner funnel to obtain wet cake-like pre-treatment particles. Thereafter, the obtained wet cake-like pre-treatment particles were redispersed in ion-exchanged water. Furthermore, dispersion | distribution and filtration were repeated 5 times, and the particle | grains before a process were wash | cleaned.

(Drying process)
Subsequently, the obtained pre-treatment particles were dispersed in an aqueous ethanol solution having a concentration of 50% by mass. Thereby, the slurry of the particle | grains before a process was obtained. Subsequently, using a continuous surface reformer (“Coatmizer (registered trademark)” manufactured by Freund Sangyo Co., Ltd.), the pre-treatment particles in the slurry were removed under the conditions of a hot air temperature of 45 ° C. and a blower air volume of 2 m ³ / min. Dried.

(Mechanical processing)
Subsequently, using a fluid mixer ("FM-20C / I" manufactured by Nihon Coke Kogyo Co., Ltd.), under the conditions of a rotational speed of 3000 rpm and a jacket temperature of 20 ° C, mechanical treatment (more specifically, Treatment to give a shearing force). The processing time of this mechanical processing was as shown in Table 1. For example, in the production of toner TA-1, the pre-treatment particles were subjected to a mechanical treatment for 10 minutes. In the production of the toner TA-9, the pre-treatment particles were subjected to a mechanical treatment for 20 minutes. By subjecting the pre-treated particles to a mechanical treatment, toner mother particle powder was obtained. In the production of the toner TB-5, the mechanical treatment was not performed, and the pre-treatment particles were used as toner base particles as they were.

(External addition process)
Subsequently, 100 parts by mass of toner base particles and hydrophobic silica particles (Nippon Aerosil Co., Ltd.) under the conditions of a rotation speed of 3000 rpm and a jacket temperature of 20 ° C. using an FM mixer (“FM-10B” manufactured by Nippon Coke Industries, Ltd.) 1.2 parts by mass of “AEROSIL (registered trademark) RA-200H” manufactured by company) and 0.8 parts by mass of conductive titanium oxide particles (“EC-100” manufactured by Titanium Industry Co., Ltd.) were mixed for 2 minutes. As a result, the external additive 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-16 and TB-1 to TB-7 shown in Table 1) were obtained.

  Regarding the toners TA-1 to TA-16 and TB-1 to TB-7 obtained as described above, the results of measuring the roundness of the shell particles and the Ru dyeing rate are as shown in Table 1. For example, regarding toner TA-1, the circularity of the shell particles was 0.62, and the Ru dyeing rate was 68%. In toner TB-7, the resin particles constituting the shell layer did not contain Ru dye resin. Each measurement method of the roundness of the shell particles and the Ru staining rate was as follows.

<Measuring method of circularity of shell particles>
A sample (toner) was dispersed in a room temperature curable epoxy resin and cured in an atmosphere at a temperature of 40 ° C. for 2 days to obtain a cured product. The obtained cured product was dyed with ruthenium tetroxide, and then cut out using an ultramicrotome (“EM UC6” manufactured by Leica Microsystems Co., Ltd.) equipped with a diamond knife to obtain a flake sample. Then, the cross section of the obtained thin piece sample was image | photographed using the transmission electron microscope (TEM) (The JEOL Co., Ltd. product "JSM-6700F").

  By analyzing the TEM image using image analysis software (“WinROOF” manufactured by Mitani Corporation), the circularity (= projection area of the particles) of the shell particles (resin particles constituting the resin film covering the surface of the toner core) (Perimeter of the circle / perimeter of the particle). The circularity of each of the 10 shell particles was measured for each toner particle, and the number average value of the circularity of the 10 obtained shell particles was defined as the circularity of the shell particle in the toner particle.

<Measurement method of Ru staining rate>
Toner dispersion liquid was prepared by dispersing 2.0 g of a sample (toner) in 100 g of a 2% by weight aqueous solution of a nonionic surfactant (Emulgen (registered trademark) 120 manufactured by Kao Corporation, component: polyoxyethylene lauryl ether). Got. Subsequently, the obtained toner dispersion was subjected to ultrasonic treatment using an ultrasonic disperser (“Ultrasonic Miniwelder P128” manufactured by Ultrasonic Industrial Co., Ltd., output: 100 W, oscillation frequency: 28 kHz), and toner mother The external additive was removed from the particles. Subsequently, the ultrasonically treated toner dispersion was subjected to suction filtration using a qualitative filter paper (“FILTER PAPER No. 1” manufactured by Advantech). Thereafter, reslurry to which 50 mL of ion exchange water was added and suction filtration were repeated three times to obtain toner base particles (toner from which the external additive had been removed) of the sample (toner).

Subsequently, the obtained toner base particles (powder) are exposed to steam of 2 mL of 5% strength by weight RuO ₄ aqueous solution for 20 minutes in an air atmosphere at normal temperature (25 ° C.). Stained with (ruthenium). The dyed toner base particles were photographed using a field emission scanning electron microscope (FE-SEM) (“JSM-7600F” manufactured by JEOL Ltd.) to obtain a reflected electron image of the toner base particles. . Of the surface area of the toner base particles, the area stained with Ru (stained area) was displayed brighter than the area not stained with Ru (non-stained area). The FE-SEM imaging conditions were an acceleration voltage of 10.0 kV, an irradiation current of 95 pA, a WD (working distance) of 7.8 mm, a magnification of 5000 times, a contrast of 4800, and a brightness (brightness) of 550.

Subsequently, image analysis of the reflected electron image was performed using image analysis software (“WinROOF” manufactured by Mitani Corporation). Specifically, the backscattered electron image was converted into image data in jpg format, and 3 × 3 Gaussian filter processing was performed. Subsequently, a luminance value histogram (vertical axis: frequency (number of pixels), horizontal axis: luminance value) of the filtered image data was obtained. The luminance value histogram showed the distribution of luminance values in the surface area (stained area and non-stained area) of the toner base particles. With respect to the luminance value histogram, fitting to a normal distribution by the least square method and waveform separation are performed, and a non-stained waveform indicating a luminance value distribution (normal distribution) in a non-stained region and a luminance value distribution (normal distribution) in the stained region. And a stained waveform showing. Subsequently, the Ru staining rate (unit:%) was determined from the areas of the two obtained waveforms (the area R _{C of} the unstained waveform and the area R _{S of the} stained waveform) based on the following formula.
Ru staining rate = 100 × R _S / (R _C + R _S )

[Evaluation method]
The evaluation method of each sample (toners TA-1 to TA-16 and TB-1 to TB-7) 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 type 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 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 setting 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)
2 g of the sample (toner) was put in a 20 mL polyethylene container, and the container was left in a thermostat set at 65 ° 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 100 mesh (aperture 150 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 was set on a powder tester (manufactured by Hosokawa Micron Co., Ltd.), and according to the manual of the powder tester, the sieve was vibrated for 30 seconds under the conditions of the rheostat scale 5, and the evaluation 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).

[Evaluation results]
Table 4 shows the results of evaluating heat-resistant storage stability (aggregation degree) and low-temperature fixability (minimum fixing temperature) for each of toners TA-1 to TA-16 and TB-1 to TB-7.

Each of the toners TA-1 to TA-16 (toners according to Examples 1 to 16) had the above-described basic configuration. Specifically, as shown in Tables 1 and 2, in each of toners TA-1 to TA-16, the shell layer has film-forming heat-resistant particles (glass transition point of 50 ° C. or more and 100 ° C. or less and circularity of 0.55 or more and 0 .75 or less of resin particles). In toner TA-14, the resin film contained two or more types of resin particles, and 50% by mass (= 100 × 110 / (110 + 110)) of the resin particles were film-formed heat-resistant particles. In each of toners TA-1 to TA-16, when toner without an external additive is exposed to the vapor of a 5 mass% RuO ₄ (ruthenium tetroxide) aqueous solution for 20 minutes, toner base particles ( Of the surface area of the toner particles in the absence of external additives, 50% to 80% of the surface area was dyed with Ru (see Table 1). As shown in Table 4, each of the toners TA-1 to TA-16 was excellent in heat resistant storage stability and low temperature fixability.

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

DESCRIPTION OF SYMBOLS 10 Toner mother particle 11 Toner core 12 Shell layer 12a Resin particle 12b Resin particle

Claims (8)

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 shell layer includes a resin film mainly composed of an aggregate of resin particles having a glass transition point of 50 ° C. or more and 100 ° C. or less and a circularity of 0.55 or more and 0.75 or less,
When the toner in the absence of external additive is exposed to the vapor of a 5 mass% RuO ₄ aqueous solution for 20 minutes, 50% to 80% of the surface area of the toner particle in the absence of external additive. An electrostatic latent image developing toner in which the region is dyed with Ru.   The electrostatic latent image developing toner according to claim 1, wherein the resin particles are substantially composed of a polymer of a monomer containing at least one vinyl compound.   The electrostatic latent image developing toner according to claim 2, wherein the monomer of the polymer constituting the resin particles includes a nitrogen-containing vinyl compound as the vinyl compound.   The electrostatic latent image developing toner according to claim 2, wherein the monomer of the polymer constituting the resin particle includes a styrene monomer as the vinyl compound.   The electrostatic latent image developing toner according to claim 2, wherein the polymer constituting the resin particles includes one or more repeating units having an alcoholic hydroxyl group.   The electrostatic latent image developing toner according to claim 1, wherein in the aggregate of the resin particles constituting the resin film, the resin particles are bonded to each other by a physical force. .   The electrostatic latent image developing toner according to claim 1, wherein the core contains a crystalline polyester resin and an amorphous polyester resin.   The toner for developing an electrostatic latent image according to claim 1, wherein the toner particles further include inorganic particles as external additives.