JP2018010184A - Toner for electrostatic latent image development - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a toner for electrostatic latent image development excellent in heat-resistant storage stability, low-temperature fixability, and durability.SOLUTION: A toner for electrostatic latent image development includes a plurality of toner particles each including a composite core and a shell layer 12 that covers the surface of the composite core. The composite core is a complex of a toner core 11, and first inorganic particles 13b and second inorganic particles 13a attached respectively to the surface of the toner core 11. The shell layer 12 is a film that contains a thermoplastic resin. The first inorganic particle 13b is an inorganic particle having a particle diameter of 5 nm or more and 20 nm or less. The second inorganic particle 13a is an inorganic particle having a particle diameter of 25 nm or more and 50 nm or less. The first inorganic particles 13b and second inorganic particles 13a are present on the boundary of the toner core 11 and shell layer 12. The amount of the first inorganic particles 13b present on the surface of the toner core 11 is 40 mass% or more and 90 mass% or less with respect to the total amount of the first inorganic particles 13b and second inorganic particles 13a present on the surface of the toner core 11.SELECTED DRAWING: Figure 2

Description

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

  For example, Patent Document 1 describes a capsule toner. The toner particles contained in the capsule toner include a toner core and a shell layer (capsule layer) that covers the surface of the toner core. In the capsule toner described in Patent Document 1, the toner core contains a binder resin and a colorant, and the shell layer contains a styrene-acryl-modified polyester resin. An inorganic layer made of silica particles is present on the surface of the toner core, and a shell layer is present on the surface of the inorganic layer.

JP 2013-257404 A

  In the capsule toner described in Patent Document 1, the inorganic layer present between the toner core and the shell layer has a substantially uniform thickness. It is difficult to achieve both heat-resistant storage stability and low-temperature fixability of such toner. For this reason, it is difficult to provide an electrostatic latent image developing toner that is excellent in heat-resistant storage stability, low-temperature fixability, and durability 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, low-temperature fixability, and durability.

  The electrostatic latent image developing toner according to the present invention includes a plurality of toner particles each including a composite core and a shell layer covering the surface of the composite core. The composite core is a composite of a toner core and first and second inorganic particles attached to the surface of the toner core. The shell layer is a film containing a thermoplastic resin. The first inorganic particles are inorganic particles having a particle diameter of 5 nm to 20 nm. The second inorganic particles are inorganic particles having a particle diameter of 25 nm or more and 50 nm or less. The first inorganic particles and the second inorganic particles are present at the interface between the toner core and the shell layer. The amount of the first inorganic particles present on the surface of the toner core is 40% by mass or more and 90% by mass or less based on the total amount of the first inorganic particles and the second inorganic particles present on the surface of the toner core. It is.

  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, low-temperature fixability, and durability.

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. FIG. 2 is an enlarged view showing a part of the surface of toner base particles shown in FIG. 1.

  An embodiment of the present invention will be described. 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.

Unless otherwise specified, the number average particle diameter of the powder is the number average of the equivalent-circle diameters of primary particles (Haywood diameter: the diameter of a circle having the same area as the projected area of the particles) measured using a microscope. Value. 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. The glass transition point (Tg) is measured in accordance with “JIS (Japanese Industrial Standard) K7121-2012” using a differential scanning calorimeter (“DSC-6220” manufactured by Seiko Instruments Inc.) unless otherwise specified. It is the value. In the endothermic curve (vertical axis: heat flow (DSC signal), horizontal axis: temperature) at the second temperature rise measured by the differential scanning calorimeter, the change point of the specific heat (outside the extrapolated line of the baseline and the falling line) The temperature (onset temperature) at the intersection with the insertion line corresponds to Tg (glass transition point). Moreover, the softening point (Tm) is a value measured using a Koka type flow tester (“CFT-500D” manufactured by Shimadzu Corporation) unless otherwise specified. In the S curve (horizontal axis: temperature, vertical axis: stroke) measured with the Koka type flow tester, the temperature that becomes "(baseline stroke value + maximum stroke value) / 2" is Tm (softening point). Equivalent to. Further, the measured value of the acid value is a value measured according to “JIS (Japanese Industrial Standard) K0070-1992” unless otherwise specified.

  The hydrophobic strength (or hydrophilic strength) can be expressed by, for example, the contact angle of water droplets (easy to wet water). The larger the contact angle of the water droplet, the stronger the hydrophobicity.

  The strength of the charging property corresponds to the ease of frictional charging unless otherwise specified. For example, the toner can be triboelectrically charged by mixing and stirring with a standard carrier (anionic: N-01, cationic: P-01) provided by the Imaging Society of Japan. The surface potential of the toner particles is measured with, for example, KFM (Kelvin probe force microscope) before and after the frictional charging, and the portion having a larger potential change before and after the frictional charging has a higher charging property.

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 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. Alternatively, a two-component developer may be prepared by mixing toner and carrier using a mixing device (for example, a ball mill). 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, 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. Examples of the resin constituting the resin layer are 1 selected from the group consisting of a fluororesin (more specifically, PFA or FEP), a polyamideimide resin, a silicone resin, a urethane resin, an epoxy resin, and a phenol resin. More than one type of resin may be mentioned. 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 particle diameter of the carrier particles is preferably 20 μm or more and 120 μm or less, and more preferably 25 μm or more and 80 μm or less. The positively chargeable toner contained in the two-component developer is positively charged by friction with the carrier.

  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 image forming unit (charging device and 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. 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 fixing using a heating roller and a pressure roller) of the electrophotographic apparatus 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 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 each including a composite core and a shell layer covering the surface of the composite core. The composite core is a composite of a toner core and first and second inorganic particles attached to the surface of the toner core. The shell layer is a film containing a thermoplastic resin. The first inorganic particles are inorganic particles having a particle diameter of 5 nm or more and 20 nm or less. The second inorganic particles are inorganic particles having a particle diameter of 25 nm or more and 50 nm or less. The first inorganic particles and the second inorganic particles are present at the interface between the toner core and the shell layer (hereinafter sometimes referred to as a core-shell interface). The amount of the first inorganic particles present on the surface of the toner core is 40% by mass or more and 90% by mass or less with respect to the total amount of the first inorganic particles and the second inorganic particles present on the surface of the toner core. Hereinafter, the ratio (mass ratio) of the amount of the first inorganic particles present on the surface of the toner core to the total amount of the first inorganic particles and the second inorganic particles present on the surface of the toner core is referred to as “the ratio of the first inorganic particles. May be written.

  An external additive may be attached to the surface of the shell layer, or an external additive may be attached to 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 shell layer is referred to as a shell material.

  In the toner having the above basic configuration, the first inorganic particles (inorganic particles having a particle diameter of 5 nm to 20 nm) and the second inorganic particles (inorganic particles having a particle diameter of 25 nm to 50 nm) are formed at the core-shell interface (interface between the toner core and the shell layer). ) Exists. The relatively large second inorganic particles tend to cause distortion in the shell layer, and form a portion having a weak strength (a portion easily broken) in the shell layer. When there is a portion that is easily broken in the shell layer, even if the shell layer covers the surface of the toner core with a high coverage, it is easy to ensure sufficient low-temperature fixability of the toner. Further, the inventors have found that the covering property of the shell layer can be improved by causing relatively small first inorganic particles in addition to relatively large second inorganic particles at the core-shell interface. By improving the covering property of the shell layer, detachment of the shell layer from the toner particles can be suppressed. Further, when the first inorganic particles are present in the core exposed region (the region of the toner core surface region that is not covered with the shell layer), the bleed (the toner particle internal additive oozes out to the toner particle surface). ) Can be suppressed. As described above, when the toner has the above basic configuration, it becomes easy to ensure sufficient heat-resistant storage stability, low-temperature fixability, and durability of the toner.

  In the toner having the above basic configuration, the first inorganic particles are inorganic particles having a particle size of 5 nm to 20 nm, and the second inorganic particles are inorganic particles having a particle size of 25 nm to 50 nm. If the particle diameter of the first inorganic particles is too small or too large, the first inorganic particles tend not to sufficiently obtain the above effects (the effect of improving the covering property of the shell layer and the effect of suppressing bleeding). is there. When the particle diameter of the second inorganic particles is too small, there is a tendency that a portion that is easily broken in the shell layer cannot be sufficiently formed. If the particle diameter of the second inorganic particles is too large, the shell layer tends to be easily detached from the toner particles.

  In the toner having the above basic configuration, when the proportion of the first inorganic particles is 40% by mass or more and 90% by mass or less, it is possible to improve the heat-resistant storage stability, low-temperature fixability, and durability of the toner. When the ratio of the first inorganic particles is too large, the low-temperature fixability of the toner tends to deteriorate. The reason for this is considered to be that when the proportion of the first inorganic particles is too large, a portion that is easily destroyed in the shell layer is not sufficiently formed. When the ratio of the first inorganic particles is too small, the heat resistant storage stability and durability of the toner tend to be deteriorated. The reason for this is that if the proportion of the first inorganic particles is too small, there are too many sites in the shell layer that are easily destroyed, the shell layer is easily detached from the toner particles, or the first inorganic particles are sufficiently bleed. This is thought to be because it becomes impossible to suppress.

  In order to achieve both the heat-resistant storage stability and the low-temperature fixing property of the toner, the coverage of the shell layer on the surface of the toner core is preferably 70% or more and 95% or less in terms of area ratio. Since the surface of the toner core is covered with the shell layer at a relatively high coverage, it becomes easy to ensure sufficient heat-resistant storage stability of the toner. The covering ratio (unit:%) of the shell layer is represented by the formula “the covering ratio of the shell layer = 100 × the area of the core covering area / the area of the surface area of the 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 covering rate of the shell layer of 100% means that the entire surface of the toner core is covered with the shell layer. The coverage of the shell layer can be measured by photographing the surface of toner particles (for example, pre-stained toner particles) with an electron microscope and analyzing the obtained photographed image using commercially available image analysis software. . The coverage of the shell layer 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.

  The second inorganic particles (inorganic particles having a particle diameter of 25 nm or more and 50 nm or less) existing at the core-shell interface (interface between the toner core and the shell layer) form a break point (a portion that is easily broken) in the shell layer, thereby However, even when the surface of the toner core is covered with an area ratio of 70% or more, sufficient low-temperature fixability of the toner is easily secured. In addition, the first inorganic particles present in the core exposed area (area not covered by the shell layer in the surface area of the toner core) suppresses bleeding (a phenomenon in which the toner particle internal additive exudes to the toner particle surface). As a result, even if the entire surface of the toner core is not covered with the shell layer, sufficient heat-resistant storage stability of the toner is easily secured.

  In order to achieve both heat-resistant storage stability and low-temperature fixability of the toner, the thickness of the shell layer is preferably 30 nm or more and 100 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). When the boundary between the toner core and the shell layer is unclear in the TEM image, a combination of TEM and electron energy loss spectroscopy (EELS) is used to combine the characteristics included in the shell layer in the TEM image. By mapping various elements, the boundary between the toner core and the shell layer can be clarified.

  Hereinafter, an example of toner particles (particularly, toner mother particles) contained in the toner having the above-described basic configuration will be described with reference to FIGS. 1 and 2.

  A toner base particle 10 shown in FIG. 1 includes a toner core 11 and a shell layer 12 that partially covers the surface of the toner core 11. However, on the surface of the toner core 11, as shown in FIG. 2, a plurality of first inorganic particles 13b (inorganic particles each having a particle diameter of 5 nm to 20 nm) and a plurality of second inorganic particles 13a (each having a particle diameter of 25 nm to 50 nm). The following inorganic particles are attached. The toner core 11 and the first inorganic particles 13b and the second inorganic particles 13a attached to the surface thereof constitute a composite (composite core). The first inorganic particles 13b and the second inorganic particles 13a are present at the interface between the toner core 11 and the shell layer 12, respectively. Each shape of the 1st inorganic particle 13b and the 2nd inorganic particle 13a is spherical, for example. However, each shape of the 1st inorganic particle 13b and the 2nd inorganic particle 13a is arbitrary if it is a particulate form.

  The shell layer 12 is a film containing a thermoplastic resin. The surface of the shell layer 12 has convex portions P corresponding to the second inorganic particles 13a. Specifically, in the surface region of the shell layer 12, the region where the second inorganic particles 13 a exist under the shell layer 12 is higher than the region where the second inorganic particles 13 a do not exist under the shell layer 12. .

The carbon ratio is described below. Of the CO ₂ present in the atmosphere, the concentration of CO ₂ containing radioactive carbon ( ¹⁴ C) is kept constant in the atmosphere. On the other hand, the plant takes in CO ₂ containing ¹⁴ C in the atmosphere in the process of photosynthesis. For this reason, it is considered that the concentration of ¹⁴ C in carbon in the organic component of the plant has the same ratio as the concentration of CO ₂ containing ¹⁴ C in the atmosphere. The concentration of ¹⁴ C in carbon in common plant organic components is about 107.5 pMC (percent Modern Carbon). Carbon contained in animals is derived from carbon contained in plants. For this reason, the concentration of ¹⁴ C in carbon in the organic components of animals also tends to be the same as that of plants.

The ratio of carbon derived from biomass out of carbon in the toner (unit: mass%) can be determined according to the following formula (1).
Ratio of carbon derived from biomass = (X / 107.5) × 100 (1)
In the above formula, X (pMC) is the concentration of ¹⁴ C contained in the toner.

A plastic product in which the proportion of carbon derived from biomass in the carbon contained in the product is 25% by mass or more is particularly preferable in order to achieve carbon neutrality. These plastic products are given a biomass plaque (Japan Bioplastics Association certification). For a toner in which the proportion of carbon derived from biomass in the contained carbon is 25% by mass or more, the concentration X of ¹⁴ C is obtained from the above formula (1), and becomes 26.9 pMC or more. Accordingly, when preparing the polyester resin, it is preferable that the concentration of radioactive carbon isotope ¹⁴ C of carbon contained in the toner is 26.9 pMC or more. The concentration of ¹⁴ C in the carbon element of the petrochemical product can be measured according to ASTM-D6866.

In order to achieve both the heat-resistant storage stability and the low-temperature fixability of the toner, the volume median diameter (D ₅₀ ) of the toner core is preferably 4 μm or more and 9 μm or less.

  Hereinafter, a suitable example of the configuration of the toner particles will be described. The toner core contains a binder resin. The toner core may contain an internal additive (for example, at least one of a release agent, a colorant, a charge control agent, and a magnetic powder) in addition to the binder resin, as necessary.

[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.

  The binder resin is preferably a polyester resin, an acid value of 3 mgKOH / g to 30 mgKOH / g, a glass transition point (Tg) of 55 ° C. to 65 ° C., and a softening point (Tm) of 130 ° C. to 150 ° C. Is particularly preferred.

  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, aliphatic diols or bisphenols) or trihydric or higher alcohols as shown below 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.

  Preferred examples of the aliphatic diols 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, or 1,12-dodecanediol Etc.), 2-butene-1,4-diol, 1,4-cyclohexanedimethanol, dipropylene glycol, polyethylene glycol, polypropylene glycol, or polytetramethylene glycol.

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

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

  Preferable examples of the divalent carboxylic acid include aromatic dicarboxylic acid (more specifically, phthalic acid, terephthalic acid, or isophthalic acid), α, ω-alkanedicarboxylic acid (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 (specifically, n-butenyl succinic acid, isobutenyl succinic acid, n-octenyl succinic acid, n-dodecenyl succinic acid, or isodode) Senylsuccinic acid, etc.), maleic acid, fumaric acid, citraconic acid, itaconic acid, glutaconic acid, or cyclohexanedicarboxylic acid Examples include acids.

  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.

  As the polyester resin (binder resin), a polyester resin containing plant-derived 1,2-propanediol as an alcohol component is preferable, and plant-derived 1,2-propanediol and one or more aromatic dicarboxylic acids (for example, A polymer of terephthalic acid) and one or more trivalent carboxylic acids (eg trimellitic acid) is particularly preferred. In order to improve the low-temperature fixability of the toner while ensuring sufficient environmental properties, 60% by mass or more of the alcohol component of the polyester resin (binder resin) is preferably plant-derived 1,2-propanediol. It is particularly preferable that 100% by mass of the alcohol component of the polyester resin (binder resin) is plant-derived 1,2-propanediol.

  Plant-derived 1,2-propanediol can be produced using, for example, chemical synthesis, fermentation, or a combination of these methods. In an example of a method for producing a plant-derived 1,2-propanediol, plant biomass containing a saccharide such as glucose is hydrolyzed to obtain glycerin. Subsequently, plant-derived 1,2-propanediol is obtained by reacting glycerin with hydrogen. As the plant biomass, for example, one or more vegetable oils and fats selected from the group consisting of soybean oil, palm oil, palm oil, castor oil, and cacao oil can be used. As a method for hydrolyzing plant biomass, a chemical method using an acid or a base may be employed, a biological method using an enzyme or a microorganism may be employed, or another method may be employed. Also good.

  As a method for synthesizing a polyester resin, one or more polyhydric alcohols and one or more polyhydric carboxylic acids can be used in the presence of a catalyst while removing by-product volatile components at a temperature of 200 ° C. or more and 250 ° C. or less And a method of subjecting the polymer to condensation polymerization. In order to accelerate the polymerization reaction, the polymerization reaction of the resin raw material (monomer or prepolymer) may be performed in a reduced pressure atmosphere. Examples of catalysts include metals (more specifically, tin, titanium, antimony, manganese, nickel, zinc, lead, iron, magnesium, calcium, germanium, etc.) or metal compounds (more specifically, the aforementioned Metal oxide).

  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 any repeating unit is introduced into the resin (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 obtain a toner suitable for image formation, the amount of the colorant is preferably 0.1 parts by mass or more and 50 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. You may use the magnetic powder mentioned later as a black coloring agent.

  The toner core includes a yellow colorant (more specifically, naphthol yellow, monoazo yellow, diazo yellow, disazo yellow, or anthraquinone compound), a magenta colorant (more specifically, quinacridone compound, naphthol compound, carmine 6B, Or a colorant such as monoazo red) or a cyan colorant (more specifically, a phthalocyanine blue or anthraquinone compound).

(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 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 10 parts by mass or less with respect to 100 parts by mass of the binder resin.

  Wax is preferred as the release agent in the toner core. Examples of the wax include ester wax, polyethylene wax, polypropylene wax, fluororesin wax, Fischer-Tropsch wax, paraffin wax, or montan wax. In order to improve the fixing property and offset resistance of the toner, ester wax is preferable. Examples of the ester wax include natural ester wax (for example, carnauba wax or rice wax), or synthetic ester wax. In the toner having the above basic configuration, when the toner core contains a polyester resin as a binder resin, the toner core may contain an ester wax (for example, carnauba wax) or a polyethylene wax as a release agent. Particularly preferred. One type of release agent may be used alone, or multiple types of release agents may be used in combination.

(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 uniformly impart sufficient magnetism to the toner core, the particle size of the magnetic powder is preferably 0.1 μm or more and 1.0 μm or less. In addition, in order to suppress elution of metal ions (for example, iron ions) from magnetic powder, magnetic powder (more specifically, with a surface treatment agent (more specifically, silane coupling agent or titanate coupling agent)) The surface of each magnetic particle contained in the magnetic powder is preferably treated.

[First inorganic particles and second inorganic particles]
In the toner having the basic configuration described above, the toner particles include a composite core and a shell layer that covers the surface of the composite core. In the composite core, first inorganic particles (inorganic particles having a particle diameter of 5 nm to 20 nm) and second inorganic particles (inorganic particles having a particle diameter of 25 nm to 50 nm) are attached to the surface of the toner core. For example, the toner particles and the inorganic powder (specifically, a powder containing a plurality of first inorganic particles and a plurality of second inorganic particles) are agitated together, whereby the first inorganic particles and the second inorganic particles are stirred. A part (bottom part) of each of the particles is embedded in the surface layer portion of the toner core, and the first inorganic particles and the second inorganic particles adhere to the surface of the toner core by physical force (physical bonding). The amount of each of the first inorganic particles and the second inorganic particles 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 core.

  Examples of materials of the first inorganic particles and the second inorganic particles include silica, silicon carbide, silicon nitride, alumina, titanium oxide, zinc oxide, tin oxide, chromium oxide, cerium oxide, antimony trioxide, magnesium oxide, Zirconium oxide, barium sulfate, barium carbonate, calcium carbonate, barium titanate, magnesium titanate, calcium titanate, strontium titanate, silica sand, clay, mica, wollastonite, diatomaceous earth, or pengala.

(Example of method for producing titanium oxide particles)
A titanium tetrachloride solution is neutralized with sodium hydroxide to precipitate a colloidal titanium compound. The obtained colloidal titanium compound is aged and then baked at a temperature of 575 ° C. to obtain titanium oxide (bulk). The obtained titanium oxide (bulk) is pulverized using a hammer mill to obtain a pulverized product of titanium oxide (for example, a pulverized product having a number average primary particle size of 0.01 μm to 0.50 μm). By changing the pulverization conditions, the particle size of the pulverized product can be adjusted.

Subsequently, the obtained pulverized titanium oxide is dispersed in water, sodium pyrophosphate is added, and wet pulverization is performed using a sand mill to obtain a 50 g / L suspension of titanium oxide fine particles. Subsequently, after the obtained titanium oxide suspension was heated to 80 ° C., tin chloride (SnCl ₄ .5H ₂ O) and antimony chloride (SbCl) were maintained while maintaining the pH of the titanium oxide suspension at 6-9. ₂ ) is dissolved in 300 mL of a 2N aqueous hydrochloric acid solution and a 10% strength by weight aqueous sodium hydroxide solution is added to the titanium oxide suspension over 60 minutes. Thereby, in the titanium oxide suspension, a coating layer (conductive layer) composed of hydrates of tin oxide and antimony oxide is formed on the surface of the titanium oxide fine particles.

Subsequently, after adjusting the pH of the titanium oxide suspension to 8, the titanium oxide suspension is filtered (solid-liquid separation). Further, filtration (solid-liquid separation) and washing (dispersion in water) are repeated until the specific resistance of the filtrate reaches 20000 Ω · cm to obtain wet cake-like titanium oxide fine particles. Subsequently, the obtained wet cake-like titanium oxide fine particles are dried at a temperature of 120 ° C. and then baked at a temperature of 500 ° C. for 60 minutes. Subsequently, the fired titanium oxide fine particles are crushed using, for example, a jet mill (manufactured by Nippon Pneumatic Industry Co., Ltd.). By the above method, titanium oxide particles (substrate: TiO ₂ particles, coating layer: Sb-doped SnO ₂ film) are obtained.

(Example of method for producing alumina particles)
Aluminate (for example, sodium aluminate) is hydrolyzed to obtain sodium hydroxide particles (for example, sodium hydroxide particles having a boehmite transition rate of 30% or less). Subsequently, the obtained sodium hydroxide particles are pulverized using a vibration mill. Thereafter, a classification process (for example, a process for removing particles larger than a predetermined particle diameter), a firing process (for example, a heat treatment at a temperature of 1000 ° C. to 1200 ° C.), and a cleaning process (for example, cleaning with warm water) are performed. Thus, alumina particles are obtained.

Each of the first inorganic particles and the second inorganic particles may be surface-treated. For example, when silica particles are used as the inorganic particles, hydrophobicity and / or positive chargeability may be imparted to the surface of the silica particles by a surface treatment agent. Examples of the surface treatment agent include a coupling agent (more specifically, a silane coupling agent, a titanate coupling agent, or an aluminate coupling agent), or silicone oil (more specifically, dimethyl silicone oil). Etc.) can be suitably used. As the silane coupling agent, a silane compound (more specifically, methyltrimethoxysilane, aminosilane or the like) may be used, or a silazane compound (more specifically, HMDS (hexamethyldisilazane) or the like). May be used. When the surface of the silica substrate (untreated silica particles) is treated with the surface treatment agent, a large number of hydroxyl groups (—OH) present on the surface of the silica substrate are partially or entirely derived from the surface treatment agent. Substituted with a functional group. As a result, silica particles having a functional group derived from the surface treating agent (specifically, a functional group that is more hydrophobic and / or positively charged than the hydroxyl group) on the surface can be obtained. For example, when the surface of a silica substrate is treated with a silane coupling agent having an amino group, a hydroxyl group of the silane coupling agent (for example, a hydroxyl group generated by hydrolysis of an alkoxy group of the silane coupling agent with moisture) A dehydration condensation reaction (“A (silica particle) —OH” + “B (coupling agent) —OH” → “AO—B” + H ₂ O) occurs with a hydroxyl group present on the surface of the silica particle. By such a reaction, a silane coupling agent having an amino group is chemically bonded to silica, whereby an amino group is imparted to the surface of the silica particles. More specifically, the hydroxyl group present on the surface of the silica substrate is substituted with a functional group having an amino group at the end (more specifically, —O—Si— (CH ₂ ) ₃ —NH ₂ or the like). Silica particles provided with amino groups tend to have a positive chargeability stronger than that of a silica substrate. When a silane coupling agent having an alkyl group is used, a hydroxyl group present on the surface of the silica substrate is converted into a functional group having an alkyl group at the end (more specifically,- it can be replaced by O-Si-CH _3, etc.). Thus, the silica particle to which the hydrophobic group (alkyl group) was provided instead of the hydrophilic group (hydroxyl group) tends to have a stronger hydrophobicity than the silica substrate.

  Examples of the method for surface treatment of the inorganic particles include the first method in which the hydrophobizing agent is dropped or sprayed on the inorganic particles while stirring the inorganic particles at high speed, or the hydrophobizing agent solution is stirred while the solution is being stirred. A second method of adding inorganic particles to the solution can be mentioned. The hydrophobizing agent may be dissolved in an organic solvent. A commercially available hydrophobizing agent may be diluted with an organic solvent.

[Shell layer]
In the toner having the basic configuration described above, the toner core and the first inorganic particles (inorganic particles having a particle size of 5 nm to 20 nm) and the second inorganic particles (inorganic particles having a particle size of 25 nm to 50 nm) attached to the surface thereof are formed. Constructs a composite (composite core). The shell layer covers the surface of the composite core. For example, the shell layer is bonded (chemically bonded) to the surface of the composite core by chemically reacting the composite core and the shell material in the liquid. The shell layer is a film containing a thermoplastic resin.

In order to impart sufficient performance to the toner while ensuring sufficient toner fixing properties, the shell layer includes a sea-like domain (domain distributed in a sea state) containing the first resin that is a thermoplastic resin, It preferably includes an island-like domain (domain distributed in an island shape) containing the second resin. In order to ensure sufficient film quality of the shell layer, it is preferable that the first resin and the second resin each include a repeating unit derived from a vinyl compound. In addition, a vinyl compound having a functional group corresponding to the performance to be imparted to the toner is polymerized to obtain a second resin (as a result, island-like domains are formed in the shell layer by the second resin). The desired performance can be imparted to the toner accurately. In the resin, it is considered that the repeating unit derived from the vinyl compound is addition-polymerized by a carbon double bond “C═C”. 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. Examples of the vinyl compound include ethylene, propylene, butadiene, vinyl chloride, acrylic acid, acrylic acid ester, methacrylic acid, methacrylic acid ester, acrylonitrile, or styrene.

  In order to ensure sufficient toner chargeability even in a high-temperature and high-humidity environment, each of the plurality of island-like domains has a stronger chargeability than the sea-like domain, and the hydrophobicity of the sea-like domain It is preferably stronger than the hydrophobicity of each of the island domains. Moreover, it is preferable that the quantity of 2nd resin in a shell layer is 5 to 30 mass parts with respect to 100 mass parts of 1st resin in a shell layer.

  In order to achieve both the heat-resistant storage stability and the low-temperature fixability of the toner, the first resin constituting the sea domain is one or more repeating units derived from a styrene monomer (more specifically, styrene or the like). And one or more kinds of repeating units derived from (meth) acrylic acid alkyl ester (more specifically, butyl acrylate or the like). In order to achieve both the heat resistant storage stability and the low-temperature fixability of the toner, the glass transition point (Tg) of the first resin is preferably 60 ° C. or higher and 80 ° C. or lower. For example, when the first resin is a copolymer of one or more styrene monomers and one or more (meth) acrylic acid alkyl esters, the amount of (meth) acrylic acid alkyl esters relative to the amount of styrene monomers is As the amount (mixing ratio) is increased, the glass transition point (Tg) of the first resin tends to decrease.

  In order for the sea domain to have sufficiently strong hydrophobicity and appropriate strength, the repeating unit having the highest molar fraction among the repeating units contained in the first resin constituting the sea domain is a styrene monomer. The repeating unit derived from is preferable.

In order to sufficiently suppress the moisture in the air from adsorbing to the surface of the sea domain, among all the repeat units contained in the first resin constituting the sea domain, a repeat unit having a hydrophilic functional group Is preferably 10% by mass or less, particularly preferably 0% by mass. The hydrophilic functional group is an acid group (more specifically, a carboxyl group or a sulfo group), a hydroxyl group, and a salt thereof (more specifically, —COONa, —SO ₃ Na, or —ONa). is there.

  In order to improve the positive chargeability of the toner, it is preferable that the second resin constituting the island-like domain is a resin containing one or more repeating units derived from a (meth) acryloyl group-containing quaternary ammonium compound. . Preferable examples of the (meth) acryloyl group-containing quaternary ammonium compound include (meth) acrylamidoalkyltrimethylammonium salts (more specifically, (3-acrylamidopropyl) trimethylammonium chloride, etc.) or (meth) acryloyloxy. Examples thereof include alkyltrimethylammonium salts (more specifically, 2- (methacryloyloxy) ethyltrimethylammonium chloride and the like).

  In order to improve the positive chargeability of the toner, the second resin constituting the island-like domain is composed of one or more repeating units derived from (meth) acrylamide alkyltrimethylammonium salt and 1 derived from an acrylic acid monomer. It is particularly preferable that the resin contains a repeating unit of more than one species (for example, a repeating unit derived from methyl methacrylate and a repeating unit derived from butyl acrylate). In order to ensure sufficient island-like domain strength, the glass transition point (Tg) of the second resin is preferably 90 ° C. or higher and 120 ° C. or lower. For example, when the second resin is a copolymer of at least one (meth) acrylamide alkyltrimethylammonium salt and at least one acrylic monomer, (meth) acrylamide alkyl relative to the amount of acrylic monomer. The glass transition point (Tg) of the second resin tends to increase as the amount of trimethylammonium salt (mixing ratio) increases.

  Preferable examples of the styrene monomer include styrene, alkyl styrene (more specifically, α-methyl styrene, p-ethyl styrene, 4-tert-butyl styrene, etc.), p-hydroxy styrene, m-hydroxy styrene. , Vinyl toluene, α-chlorostyrene, o-chlorostyrene, m-chlorostyrene, or p-chlorostyrene.

  Preferable examples of the acrylic acid monomer include (meth) acrylic acid, (meth) acrylonitrile, (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.

[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. For example, by stirring together the toner base particles (powder) and the external additive (powder), a part (bottom part) of the external additive particles is embedded in the surface layer part of the toner base particles, 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 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 additive particles are used, The total amount of external additive particles) 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. One type of external additive particles may be used alone, or a plurality of types of external additive particles may be used in combination.

[Toner Production Method]
In order to easily and suitably manufacture the toner having the above basic configuration, for example, a toner manufacturing method including the following toner core preparation step, core external addition step, and shell layer formation step is preferable.

(Toner core preparation process)
Preferable examples of the method for producing the toner core include a pulverization method or an aggregation method. These methods facilitate easy dispersion of the internal additive in the binder resin.

  In an example of the pulverization method, first, a binder resin, a colorant, a charge control agent, and a release agent are mixed. Subsequently, the obtained mixture is melt-kneaded using a melt-kneading apparatus (for example, a single-screw or twin-screw extruder). Subsequently, the obtained melt-kneaded product is pulverized and classified. Thereby, a toner core is obtained. The pulverization method can often produce a toner core more easily than the aggregation method.

  In an example of the aggregation method, first, these fine particles are aggregated in an aqueous medium containing fine particles of the binder resin, the release agent, and the colorant until a desired particle diameter is obtained. Thereby, aggregated particles containing a binder resin, a release agent, and a colorant are formed. Subsequently, the obtained aggregated particles are heated to unite the components contained in the aggregated particles. Thereby, a toner core having a desired particle diameter is obtained.

(Core external addition process)
As an example of a method of immobilizing the first inorganic particles (inorganic particles having a particle diameter of 5 nm to 20 nm) and the second inorganic particles (inorganic particles having a particle diameter of 25 nm to 50 nm) on the surface of the toner core, a mixing apparatus (more specifically, Specifically, using an FM mixer manufactured by Nippon Coke Industries, Ltd., a multi-purpose mixer manufactured by Nippon Coke Industries, Ltd., or a Nauter mixer (registered trademark) manufactured by Hosokawa Micron Corporation), a toner core (powder) A method of mixing inorganic powder (specifically, a powder containing a plurality of first inorganic particles and a plurality of second inorganic particles) can be mentioned. By stirring the toner core (powder) and the inorganic powder together, the first inorganic particles and the second inorganic particles adhere to the surface of the toner core by physical force (physical bonding). As a result, a composite core (composite of toner core, first inorganic particles, and second inorganic particles) is obtained.

(Shell layer forming process)
Next, a shell layer is formed on the surface of the obtained composite core. Hereinafter, a suitable example of the method for forming the shell layer will be described. In order to suppress dissolution or elution of the toner core components (particularly, the binder resin and the release agent) when forming the shell layer, it is preferable to form the shell layer in an aqueous medium. 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.

  First, a neutral aqueous medium is prepared. Subsequently, the composite core and shell material are added to the aqueous medium. The order of addition is arbitrary, and the shell material may be added before the composite core, or the composite core and the shell material may be added simultaneously. As the shell material, for example, a suspension of first resin particles (resin particles substantially composed of a first resin) and a suspension of second resin particles (resin particles substantially composed of a second resin) are added. The second resin particles have a stronger charging property than the first resin particles. Further, the hydrophobicity of the first resin particles is stronger than the hydrophobicity of the second resin particles. The Tg of the second resin is higher than the Tg of the first resin. The first resin particles and the second resin particles may be added simultaneously or separately.

  In addition, the addition amount of the shell material suitable for forming the shell layer having a desired thickness can be calculated based on, for example, the specific surface area of the composite core. Moreover, you may add a polymerization accelerator in a liquid.

  In order to uniformly adhere the shell material to the surface of the composite core, it is preferable that the composite core is highly dispersed in the liquid containing the shell material. In order to highly disperse the composite core in the liquid, a surfactant may be included in the liquid, or the liquid is stirred using a powerful stirring device (for example, “Hibis Disper Mix” manufactured by Primics Co., Ltd.). May be. When the composite core has an anionic property, aggregation of the composite core can be suppressed by using an anionic surfactant having the same polarity. 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 composite core and shell material, the liquid temperature is set at a predetermined holding temperature (for example, a speed selected from 0.1 ° C./min to 3.0 ° C./min). For example, the temperature is increased to a temperature selected from 40 ° C. to 95 ° C. Furthermore, the temperature of the liquid is maintained at the above holding temperature for a predetermined time (for example, a time selected from 30 minutes to 4 hours) while stirring the liquid. It is considered that the reaction (immobilization of the shell layer) proceeds between the composite core and the shell material while maintaining the temperature of the liquid at a high temperature (or during the temperature increase). The shell material is chemically bonded to the composite core to form a shell layer. While the first resin particles are melted (or deformed) in the liquid by heating, the second resin particles maintain a particle-like form, thereby forming a sea-island structure (sea: first resin, island: second resin). Is formed (shell layer). By forming a shell layer on the surface of the composite core in the liquid, a dispersion of toner base particles can be obtained. The first inorganic particles and the second inorganic particles remain on the surface of the toner core while maintaining the particulate form. For this reason, in the obtained toner base particles, the first inorganic is present in the core exposed region (the region of the toner core surface region not covered with the shell layer) and the core-shell interface (interface between the toner core and the shell layer). There are particles and second inorganic particles.

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

  Subsequently, the toner mother particle dispersion is cooled to, for example, room temperature (about 25 ° C.). 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, for example, the dispersion of the toner base particles in water and the filtration of the obtained dispersion liquid are repeated to wash the toner base particles. Subsequently, the washed toner base particles are dried. For drying the toner base particles, for example, a spray dryer, a fluidized bed dryer, a vacuum freeze dryer, or a vacuum dryer can be used. Thereafter, external addition to the toner base particles (shell external addition step) may be performed as necessary. In the shell external addition step, toner toner particles and external additives (for example, silica particles) are mixed using, for example, a mixer (more specifically, an FM mixer manufactured by Nippon Coke Kogyo Co., Ltd.). An external additive is adhered to the surface of the mother particle. When a spray dryer is used in the drying step, the drying step and the shell external addition step can be performed at the same time by spraying a dispersion of an external additive (for example, silica particles) onto the toner base particles. In this way, a toner containing a large number of toner particles is obtained.

  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. If an external additive is unnecessary, the shell external addition step may be omitted. When the external additive is not attached to the surface of the toner base particle (the shell external addition step is omitted), the toner base particle corresponds to the toner particle. 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-9 and TB-1 to TB-13 (each toner for developing an electrostatic latent image) according to Examples or Comparative Examples. Table 2 shows inorganic powders (inorganic particle powders) used in the production of the toner shown in Table 1.

  Hereinafter, a manufacturing method, an evaluation method, and an evaluation result of toners TA-1 to TA-9 and TB-1 to TB-13 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.

[Preparation of materials]
(Binder resin: Synthesis of polyester resin)
First, vegetable oil was hydrolyzed to obtain glycerin. Specifically, vegetable oil and a 10% by weight aqueous sodium hydroxide solution having a concentration twice the amount necessary to completely saponify the vegetable oil were added to the reaction vessel. Subsequently, the container contents were heated to completely saponify the vegetable oil. The glycerin aqueous solution was separated from the saponified container contents, and the resulting glycerin aqueous solution was distilled. Activated carbon treatment was performed on the glycerin after distillation to purify glycerin.

Next, 200 g of ethylene glycol and 76 g of cupric nitrate trihydrate were added into a reaction vessel equipped with a reflux condenser. Subsequently, after the container contents were heated and stirred at a temperature of 80 ° C. for 2 hours, 52 g of tetraethoxysilane was added dropwise, and the mixture was heated and stirred at a temperature of 80 ° C. for 2 hours. Thereafter, 18 g of water was dropped into the container, and then the contents of the container were stirred at a temperature of 80 ° C. for 3 hours to obtain a precipitate in the container. The obtained precipitate was dried at a temperature of 120 ° C. and then calcined in air at a temperature of 400 ° C. for 2 hours to obtain a copper / silica catalyst (copper content: 50 mass%). An aqueous solution containing 29.8 mg of tetraammineplatinum (II) nitrate [Pt (NH ₃ ) ₄ (NO ₃ ) ₂ ] was added to 3 g of the obtained copper / silica catalyst, and the mixture was dried to dryness using a rotary evaporator. The obtained solid was dried at a temperature of 120 ° C. and then calcined in the air at a temperature of 400 ° C. for 2 hours, and a copper-platinum / silica catalyst having a copper content of 50% by mass (mass ratio: Cu / Pt / Si = 50). /0.5/17).

Subsequently, 2 g of the copper-platinum / silica catalyst obtained as described above and 200 g of glycerin (purified glycerin) obtained by the above procedure were added to a 500 mL iron autoclave with a stirrer, and the air in the autoclave was added. Was replaced with hydrogen. Subsequently, the temperature inside the autoclave is raised to 230 ° C., and hydrogen gas is introduced into the autoclave at a rate of 5 L / min, while the autoclave is in a hydrogen (H ₂ ) atmosphere, a pressure of 2 MPa, and a temperature of 25 ° C. The inner material (liquid) was reacted for 7 hours to obtain a reaction product (liquid). The resulting reaction product was purified according to a conventional method to obtain plant-derived 1,2-propanediol.

  A 5-L four-necked flask equipped with a stirrer (As One Co., Ltd. “SM-104”), a nitrogen introducing tube, a thermocouple, a dehydrating tube, and a rectifying column was used as a reaction vessel. In this reaction vessel, 1142 g of plant-derived 1,2-propanediol (alcohol component) prepared as described above, 1743 g of terephthalic acid (carboxylic acid component), and 4 g of tin (II) dioctanoate (condensation catalyst) And added. While removing water produced by the reaction, the contents of the container were reacted at a temperature of 230 ° C. for 15 hours under an atmospheric pressure of a nitrogen atmosphere. Thereafter, the pressure in the container was reduced to 8.3 kPa, and the contents of the container were further reacted for 1 hour under conditions of a pressure of 8.3 kPa and a temperature of 230 ° C.

  Subsequently, the pressure in the container was returned to atmospheric pressure, the temperature in the container was lowered to 180 ° C., and 288 g of trimellitic anhydride was added to the container. Thereafter, the temperature in the container was raised to 210 ° C. at a rate of 10 ° C./hour. Subsequently, the contents of the container were reacted for 10 hours at 210 ° C. under atmospheric pressure. Subsequently, the pressure in the container was reduced to 20 kPa, and the contents of the container were further reacted for 1 hour under the conditions of a pressure of 20 kPa and a temperature of 230 ° C. After completion of the reaction, the contents of the container were taken out and cooled. As a result, a polyester resin was obtained.

(Preparation of inorganic powders A-1 to A-9)
Inorganic powders A-1 to A-9 from titania powder (titanium oxide crystal type: rutile, surface treatment agent: tetramethylsilane) having a broad particle size distribution, after classification and sieving. Got.

  Each of the inorganic powders A-2 to A-4 has a sharp particle size distribution, and has a number average primary particle size substantially including only titanium oxide particles having particle sizes of about 10 nm, about 15 nm, and about 20 nm, respectively. The powders were 10 nm, 15 nm, and 20 nm. Each of the inorganic powders A-6 to A-8 has a sharp particle size distribution and has a number average primary particle diameter substantially including only titanium oxide particles having particle diameters of about 30 nm, about 40 nm, and about 45 nm, respectively. The powders were 30 nm, 40 nm, and 45 nm.

  In addition, by the above classification and sieving, inorganic powder A-1 having a number average primary particle diameter of 3 nm substantially containing only titanium oxide particles having a particle diameter of about 3 nm was also obtained. In addition, inorganic powder A-5 having a number average primary particle size of 23 nm containing substantially only titanium oxide particles having a particle size of about 23 nm was also obtained by the above classification and sieving. In addition, inorganic powder A-9 having a number average primary particle size of 60 nm and containing substantially only titanium oxide particles having a particle size of about 60 nm was also obtained by the above classification and sieving.

(Preparation of inorganic powders B-1 to B-2)
From silica powder having a broad particle size distribution (“AEROSIL (registered trademark) RA-200H” manufactured by Nippon Aerosil Co., Ltd., content: dry silica particles surface-modified with trimethylsilyl group and amino group), through classification and sieving An inorganic powder B-1 substantially containing only silica particles having a particle diameter of 5 nm to 20 nm and an inorganic powder B-2 substantially containing only silica particles having a particle diameter of 25 nm to 50 nm were obtained. The inorganic powder B-1 was a powder having a sharp particle size distribution and having a number average primary particle size of 15 nm substantially including only silica particles having a particle size of about 15 nm. Inorganic powder B-2 was a powder having a sharp particle size distribution and having a number average primary particle diameter of 40 nm substantially including only silica particles having a particle diameter of about 40 nm.

(Preparation of inorganic powders C-1 to C-2)
From alumina powder (surface treatment agent: 3-aminopropyltriethoxysilane) manufactured by Nippon Aerosil Co., Ltd. having a broad particle size distribution, substantially only alumina particles having a particle diameter of 5 nm to 20 nm are obtained through classification and sieving. Inorganic powder C-1 and inorganic powder C-2 substantially containing only alumina particles having a particle diameter of 25 nm to 50 nm were obtained. The inorganic powder C-1 was a powder having a sharp particle size distribution and having a number average primary particle diameter of 15 nm substantially including only alumina particles having a particle diameter of about 15 nm. Inorganic powder C-2 was a powder having a sharp particle size distribution and having a number average primary particle size of 40 nm substantially containing only alumina particles having a particle size of about 40 nm.

  Each of the inorganic powders A-1 to A-9, B-1 to B-2, and C-1 to C-2 has a particle diameter (equivalent circle diameter) of “average particle diameter” ± 1 nm shown in Table 2. And 85% by number or more of inorganic particles. For example, inorganic powder A-1 contained inorganic particles having a particle diameter of 2 nm or more and 4 nm or less in a proportion of 85% by number or more.

(First shell material: Preparation of suspension S-1)
A 1 L three-necked flask equipped with a thermometer and a stirring blade was set in a water bath at a temperature of 30 ° C., and 815 mL of ion-exchanged water and a cationic surfactant (“Cootamin (registered trademark) 24P manufactured by Kao Corporation) were placed in the flask. , Lauryltrimethylammonium chloride 25 mass% aqueous solution) 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 was a mixed liquid of 68 mL of styrene and 12 mL of n-butyl acrylate. 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 suspension of resin fine particles (hereinafter referred to as suspension S-1) was obtained. Regarding the resin fine particles contained in the obtained suspension S-1, the number average primary particle diameter was 50 nm and Tg was 71 ° C.

(Second shell material: Preparation of suspension S-2)
A 1 L three-necked flask equipped with a thermometer and a stirring blade was set in a water bath at a temperature of 30 ° C., and 790 mL of ion-exchanged water and a cationic surfactant (“Coatamine 24P” manufactured by Kao Corporation, lauryl trimethyl) were placed in the flask. 30 mL of ammonium chloride 25% by mass aqueous solution) was added. Thereafter, the temperature in the flask was raised to 80 ° C. using a water bath. Subsequently, two kinds of liquids (third liquid and fourth liquid) were dropped into the flask contents at 80 ° C. in the flask over 5 hours. The third liquid was a mixed liquid of 100 mL of methyl methacrylate, 30 mL of n-butyl acrylate, and 20 mL of (3-acrylamidopropyl) trimethylammonium chloride. The fourth 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 suspension of resin fine particles (hereinafter referred to as suspension S-2) was obtained. Regarding the resin fine particles contained in the obtained suspension S-2, the number average primary particle diameter was 55 nm, and Tg was 103 ° C.

[Toner Production Method]
(Production of toner core)
100 parts by mass of the polyester resin obtained by the above procedure, 7.0 parts by mass of a release agent (synthetic ester wax: “Nissan Electol (registered trademark) WEP-3” manufactured by NOF Corporation), and a quaternary ammonium salt 1.5 parts by mass ("BONTRON (registered trademark) P-51" manufactured by Orient Chemical Co., Ltd.) and 7.0 parts by mass of a colorant (carbon black: "MA-100" manufactured by Mitsubishi Chemical Corporation) It mixed using the FM mixer (Nippon Coke Kogyo Co., Ltd. "FM-20B").

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. And melt-kneaded. Thereafter, the obtained kneaded material was cooled. Subsequently, the cooled kneaded material was coarsely pulverized using a pulverizer (“Rotoplex 16/8 type” manufactured by Toa Machinery Co., Ltd.) under the condition of a set particle diameter of 2 mm. Further, the obtained coarsely pulverized product was finely pulverized using a pulverizer (“Turbo Mill RS Model” manufactured by Freund Turbo Co., Ltd.). Subsequently, the obtained 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.

(Core external)
100 parts by mass of the toner core obtained as described above and 1 part by mass of the predetermined inorganic powder shown in Table 1 were mixed into a multipurpose compact mixing and grinding machine (“Multipurpose Mixer” manufactured by Nippon Coke Industries, Ltd., blade rotation speed). (Maximum): 10,000 rpm), and the mixture was mixed for 10 minutes under the condition of a rotational speed of 5000 rpm. Specifically, at least one of inorganic powders A-1 to A-9, B-1 to B-2, and C-1 to C-2 shown in Table 1 defined for each toner is shown in Table 1. Was mixed with the toner core in the amount (blending ratio) shown in FIG. “Amount” in Table 1 indicates a ratio (unit: wt% = mass%) with respect to the total amount of the inorganic powder. The total amount of the inorganic powder corresponds to 1 part by mass with respect to 100 parts by mass of the toner core. For example, in the production of the toner TA-1, 100 parts by mass of the toner core, 0.4 parts by mass of the inorganic powder A-3, and 0.6 parts by mass of the inorganic powder A-7 were mixed. In the production of the toner TA-6, 100 parts by mass of the toner core, 0.6 parts by mass of the inorganic powder B-1, and 0.4 parts by mass of the inorganic powder B-2 were mixed. In the production of the toner TA-8, 100 parts by mass of the toner core, 0.1 parts by mass of the inorganic powder A-1, 0.4 parts by mass of the inorganic powder A-3, 0.5 parts by mass Inorganic powder A-7 was mixed. In the production of the toner TB-6, 100 parts by mass of the toner core and 1 part by mass of the inorganic powder A-3 were mixed.

  The external addition process (mixing of the toner core and the inorganic powder) at this timing corresponds to “core external addition”. By the external addition of the core, inorganic particles (any of inorganic particles A-1 to A-9, B-1 to B-2, and C-1 to C-2) adhered to the surface of the toner core. As a result, a composite core (toner core having inorganic particles attached to the surface) was obtained. However, in the production of the toner TB-5, the core was not externally added. In the production of the toner TB-5, a shell layer was formed on the surface of the toner core in a state where inorganic particles were not attached in the shell layer forming step described below.

(Shell layer forming process)
A 1 L three-necked flask equipped with a thermometer and a stirring blade was prepared, and the flask was set in a water bath. Subsequently, 300 mL of ion-exchanged water was put in the flask, and the temperature in the flask was kept at 30 ° C. using a water bath. Subsequently, sodium hydroxide or dilute hydrochloric acid was added to the flask to adjust the pH of the flask contents to 7.

  Subsequently, 30 mL of the first shell material (suspension S-1 prepared by the above procedure) and 2 mL of the second shell material (suspension S-2 prepared by the above procedure) were added to the flask.

  Subsequently, 300 g of the composite core prepared in the above-described procedure (however, the toner core in the production of toner TB-5) is added to the flask, and the flask contents are stirred for 1 hour at a rotation speed of 200 rpm and a temperature of 30 ° C. did. Subsequently, 300 mL of ion exchange water was added to the flask, and the temperature in the flask was increased to 70 ° C. at a rate of 1 ° C./min while stirring the flask contents at a rotation speed of 100 rpm. 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. Thereafter, the toner mother particle dispersion was cooled to room temperature (about 25 ° C.). As a result, a shell layer was formed on the surface of the composite core in the liquid (however, in the production of toner TB-5), and a dispersion of toner base particles was obtained.

(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 ion-exchanged water. Further, dispersion and filtration were repeated 5 times to wash the toner base particles.

(Drying process)
Subsequently, the washed toner base particles (powder) were dispersed in an aqueous ethanol solution having a concentration of 50% by mass to obtain a slurry of toner base particles. Subsequently, the toner base particles in the slurry were removed under the conditions of a hot air temperature of 45 ° C. and a blower air volume of 2 m ³ / min. Dried. As a result, dried toner base particles (powder) were obtained.

(External shell)
Subsequently, using a 10 L capacity FM mixer (manufactured by Nippon Coke Kogyo Co., Ltd.), 100 parts by mass of the toner base particles obtained as described above, and dry silica particles (“AEROSIL REA90” manufactured by Nippon Aerosil Co., Ltd.) 1 The mass part was mixed for 5 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 (toners TA-1 to TA-9 and TB-1 to TB-13) containing a large number of toner particles were obtained.

  Regarding the toners TA-1 to TA-9 and TB-1 to TB-13 obtained as described above, the ratio of the first inorganic particles (inorganic particles having a particle diameter of 5 nm to 20 nm) and the second inorganic particles (particles) Each measurement result with the ratio of the inorganic particles having a diameter of 25 nm or more and 50 nm or less was as shown in “abundance ratio of inorganic particles” in Table 1. The ratio of the first inorganic particles is a mass ratio of the amount of the first inorganic particles present on the surface of the toner core to the total amount of the first inorganic particles and the second inorganic particles present on the surface of the toner core. The “first particle (small)” in the “abundance ratio of inorganic particles” in FIG. The ratio of the second inorganic particles is the mass ratio of the amount of the second inorganic particles present on the surface of the toner core to the total amount of the first inorganic particles and the second inorganic particles present on the surface of the toner core. The “second particle (large)” in the “abundance ratio of inorganic particles” in FIG. The ratio of the first inorganic particles and the ratio of the second inorganic particles were measured based on the cross-sectional images of the toner particles photographed using a TEM (transmission electron microscope). Whether or not the inorganic particles present on the surface of the toner core correspond to the first inorganic particles (or the second inorganic particles) was determined based on the equivalent circle diameter of the inorganic particles in the cross-sectional image. For example, regarding toner TA-1, the ratio of the first inorganic particles was 40% by mass, and the ratio of the second inorganic particles was 60% by mass.

[Evaluation method]
The evaluation method of each sample (toners TA-1 to TA-9 and TB-1 to TB-13) is as follows.

(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 50 ° C. for 100 hours. Thereafter, the toner taken out from the thermostat was cooled to room temperature (about 25 ° C.) to obtain an evaluation toner.

Subsequently, the obtained toner for evaluation was placed on a sieve having a known mass of 140 mesh (aperture 105 μm). Then, the mass of the sieve containing the toner was measured, and the mass of the toner on the sieve (the mass of the toner before sieving) was determined. Subsequently, the 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 condition of the rheostat scale 5, and the evaluation toner was sieved. Then, the mass of the toner remaining on the sieve (the mass of the toner after sieving) was determined by measuring the mass of the sieve containing the toner after sieving. From the mass of the toner before sieving and the mass of the toner 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 is 10% by mass or less, it is evaluated as ◎ (very good), and when the degree of aggregation is more than 10% by mass and 20% by mass or less, it is evaluated as ◯ (good), and the degree of aggregation exceeds 20% by mass. X (not good).

(Low temperature fixability)
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. .

  As an evaluator, a printer having a Roller-Roller type heat and pressure type fixing device (nip width 8 mm) (evaluator capable of changing the fixing temperature by remodeling “FS-C5200DN” manufactured by Kyocera Document Solutions Co., Ltd.) 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, the size is 25 mm × on the evaluation paper (“ColorCopy (registered trademark)” manufactured by Mondi, A4 size, basis weight 90 g / m ² ) under the condition of a toner loading of 1.3 mg / cm ^2. A 25 mm solid image (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 setting range of the fixing temperature was 100 ° C. or higher and 145 ° C. or lower. Specifically, the fixing temperature of the fixing device was gradually lowered from 145 ° C., and the lowest temperature (minimum fixing temperature) at which the solid image (toner image) can be fixed on the paper 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 folded in half so that the surface on which the image was formed was inside, and the image on the crease was rubbed 5 times with a 1 kg brass weight covered with a fabric. . 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 120 ° C. or lower, it was evaluated as “good”, and when the minimum fixing temperature exceeded 120 ° C., it was evaluated as “poor” (not good).

(Charge amount and image density: initial)
100 parts by weight of a developer carrier (carrier for “TASKalfa 5550ci” manufactured by Kyocera Document Solutions Co., Ltd.) and 10 parts by weight of a sample (toner) were mixed for 30 minutes using a ball mill to obtain a developer for evaluation. . Subsequently, the developer for evaluation was allowed to stand for 24 hours under a predetermined environment (normal temperature and normal humidity environment or high temperature and high humidity environment). The room temperature and humidity environment was “temperature 20 ° C. and humidity 65% RH”, and the high temperature and humidity environment was “temperature 32.5 ° C. and humidity 80% RH”. Thereafter, using a Q / m meter (“MODEL 210HS” manufactured by Trek), the charge amount of the toner in the developer for evaluation was measured under the following conditions.

<Measurement method of charge amount of toner in developer>
0.10 g of developer (carrier and toner) was charged into a Q / m meter measurement cell, and only the toner out of the charged developer was sucked through a sieve (metal mesh) for 10 seconds. Then, based on the formula “total electric amount of sucked toner (unit: μC) / mass of sucked toner (unit: g)”, the charge amount of toner in the developer (unit: μC / g) is calculated. Calculated.

  When the charge amount was 20.0 μC / g or more, it was judged as “good”, and when the charge amount was less than 20.0 μC / g, it was judged as “poor” (not good).

  Further, an image was formed using the evaluation developer prepared by the above-described method, and the image density (ID) of the image was measured. As an evaluation machine, a printer (“ECOSYS (registered trademark) FS-C5016N” manufactured by Kyocera Document Solutions Co., Ltd., linear velocity: 100 mm / second) was used. The evaluation 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 such an evaluation machine, a sample image including a solid portion and a blank portion was formed on a recording medium (evaluation paper) under a predetermined environment (normal temperature and normal humidity environment or high temperature and high humidity environment). The room temperature and humidity environment was “temperature 20 ° C. and humidity 65% RH”, and the high temperature and humidity environment was “temperature 32.5 ° C. and humidity 80% RH”. The image density (ID) of the solid portion of the image formed on the recording medium was measured using a reflection densitometer (“RD914” manufactured by X-Rite).

  When the image density (ID) was 1.22 or more, it was judged as ◯ (good), and when the image density (ID) was less than 1.22, it was judged as x (not good).

(Charge amount and image density after printing)
Using the same evaluation machine as the initial evaluation, a printing durability test was performed in which 100,000 sheets were continuously printed at a printing rate of 4% under a predetermined environment (normal temperature and normal humidity environment or high temperature and high humidity environment). The room temperature and humidity environment was “temperature 20 ° C. and humidity 65% RH”, and the high temperature and humidity environment was “temperature 32.5 ° C. and humidity 80% RH”. After the printing durability test, the charge amount of the toner in the developer taken out from the developing device of the evaluation machine was measured. Further, after the printing durability test, a sample image including a solid portion and a blank portion was formed on a recording medium (evaluation paper) using an evaluation machine, and the image density (ID) of the formed image was measured. The measurement method and evaluation criteria for the charge amount and the image density (ID) are the same as in the initial evaluation.

[Evaluation results]
Tables 3 and 4 show the evaluation results of toners TA-1 to TA-9 and TB-1 to TB-13, respectively. Table 3 shows the measured values of the charge amount in each environment (each toner charge amount after initial printing and after printing) and ID (each image density after printing and initial printing) in each environment. . Table 4 shows measured values of low-temperature fixability (minimum fixing temperature) and heat-resistant storage stability (cohesion degree). In Table 3, “N / N” indicates a normal temperature and normal humidity environment (temperature 20 ° C. and humidity 65% RH), and “H / H” indicates a high temperature and high humidity environment (temperature 32.5 ° C. and humidity 80% RH). ).

  The toners TA-1 to TA-9 (toners according to Examples 1 to 9) each had the above-described basic configuration. Specifically, each of the toners TA-1 to TA-9 includes a plurality of toner particles each including a composite core and a shell layer that covers the surface of the composite core. The composite core was a composite of a toner core and first and second inorganic particles attached to the surface of the toner core. The shell layer was a film containing a thermoplastic resin (specifically, a styrene-acrylic acid resin). The first inorganic particles were inorganic particles having a particle diameter of 5 nm or more and 20 nm or less. The second inorganic particles were inorganic particles having a particle diameter of 25 nm or more and 50 nm or less. The first inorganic particles and the second inorganic particles were present at the core-shell interface (the interface between the toner core and the shell layer). The amount of the first inorganic particles present on the surface of the toner core was 40% by mass or more and 90% by mass or less with respect to the total amount of the first inorganic particles and the second inorganic particles present on the surface of the toner core (Table 1 (see “first particles (small)” in “abundance ratio of inorganic particles” in FIG. 1).

The concentration of radioactive carbon isotope ¹⁴ C of carbon contained in each of toners TA-1 to TA-9 (measurement method: ASTM-D6866) was about 33.5 pMC. In each of the toners TA-1 to TA-9, the cross section of the toner particles was confirmed using a TEM (transmission electron microscope), and the surface of the shell layer was a convex portion corresponding to the second inorganic particles of the composite core. Had. Moreover, the thickness of the shell layer was about 40 nm. Further, when the surface of the toner particles was confirmed using an SEM (scanning electron microscope), the area ratio of the area covered with the shell layer in the surface area of the toner core was about 90%. The first inorganic particles were present in the core exposed area (area of the surface area of the toner core that was not covered with the shell layer).

  As shown in Tables 3 and 4, the toners TA-1 to TA-9 were excellent in low-temperature fixability, heat-resistant storage stability, and durability, respectively. The toners TA-1 to TA-9 had excellent chargeability both at the initial stage and after the printing durability test, and could form high-quality images.

  The toners TB-1, TB-2, TB-7, and TB-9 (the toners according to Comparative Examples 1, 2, 7, and 9) are stored in higher heat resistance than the toners TA-1 to TA-9, respectively. It was inferior. In addition, in each of toners TB-1, TB-2, TB-7, and TB-9, the shell layer is detached from the toner particles during the printing durability test, and a high-quality image cannot be continuously formed. It was.

  Toner TB-8 (toner according to Comparative Example 8) was inferior in heat resistant storage stability as compared with toners TA-1 to TA-9. In toner TB-8, bleeding occurred in the core exposed area.

  The toner TB-13 (toner according to Comparative Example 13) was inferior in heat resistant storage stability as compared with the toners TA-1 to TA-9. In addition, with toner TB-13, the covering property of the shell layer was insufficient, bleeding occurred in the core exposed region, and a high-quality image could not be continuously formed.

  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 13a 2nd inorganic particle 13b 1st inorganic particle P Convex part

Claims (8)

A plurality of toner particles comprising a composite core and a shell layer covering the surface of the composite core;
The composite core is a composite of a toner core and first inorganic particles and second inorganic particles attached to the surface of the toner core, respectively.
The shell layer is a film containing a thermoplastic resin,
The first inorganic particles are inorganic particles having a particle diameter of 5 nm to 20 nm,
The second inorganic particles are inorganic particles having a particle diameter of 25 nm or more and 50 nm or less,
The first inorganic particles and the second inorganic particles are present at the interface between the toner core and the shell layer;
The amount of the first inorganic particles present on the surface of the toner core is 40% by mass or more and 90% by mass or less based on the total amount of the first inorganic particles and the second inorganic particles present on the surface of the toner core. An electrostatic latent image developing toner.   The electrostatic latent image developing toner according to claim 1, wherein the surface of the shell layer has a convex portion corresponding to the second inorganic particles.   3. The electrostatic latent image developing toner according to claim 1, wherein a coverage ratio of the shell layer on a surface of the toner core is 70% or more and 95% or less in an area ratio.   4. The electrostatic latent image developing toner according to claim 3, wherein the first inorganic particles are present in an area of the surface area of the toner core that is not covered with the shell layer. 5.   The toner for electrostatic latent image development according to any one of claims 1 to 4, wherein the toner core contains a polyester resin containing plant-derived 1,2-propanediol as an alcohol component. The shell layer includes a sea-like domain containing a first resin that is a thermoplastic resin, and an island-like domain containing a second resin,
The electrostatic latent image developing toner according to claim 1, wherein each of the first resin and the second resin includes a repeating unit derived from a vinyl compound. The first resin is a thermoplastic resin including one or more repeating units derived from a styrene monomer and one or more repeating units derived from an alkyl (meth) acrylate,
The electrostatic latent image developing toner according to claim 6, wherein the second resin is a resin including one or more repeating units derived from a (meth) acryloyl group-containing quaternary ammonium compound.   The electrostatic latent image developing toner according to claim 1, wherein each of the first inorganic particles and the second inorganic particles is a titanium oxide particle.

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