JP2018004697A - Toner for electrostatic latent image development - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a toner for electrostatic latent image development excellent in all of heat-resistant storage stability, low-temperature fixability, and chargeability.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 partially covers the surface of the composite core. The composite core is a complex of a toner core 11 containing a polyester resin and a plurality of core externally-added particles 13 respectively attached to the surface of the toner core 11. The shell layer 12 contains a thermosetting nitrogen-containing resin. The core externally-added particle 13 is a silica particle including an amino group in the surface.SELECTED DRAWING: Figure 2

Description

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

  The toner particles contained in the capsule toner include a core and a shell layer (capsule layer) that covers the surface of the core. The shell layer contains a resin. Patent Document 1 discloses a technique for improving the heat-resistant storage stability of a toner by containing inorganic fine particles in a shell layer.

JP 2006-215151 A

  Only with the technique described in Patent Document 1, it is difficult to obtain a toner (particularly, a positively chargeable toner) excellent in all of heat-resistant storage stability, low-temperature fixability, and chargeability. For example, if the shell coverage (the area ratio of the area covered by the shell layer in the surface area of the core) is too large, the low-temperature fixability of the toner is considered to deteriorate. Further, if the shell coverage is too small, it is considered that the heat resistant storage stability of the toner is deteriorated. Further, in the toner described in Patent Document 1, the chargeability of the core exposed region (the region of the core surface region that is not covered by the shell layer) on the surface of the toner particles depends on the core material, and sufficient toner charging is performed. It is considered difficult to ensure sex.

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

  The electrostatic latent image developing toner according to the present invention includes a plurality of toner particles including a composite core and a shell layer that partially covers the surface of the composite core. The composite core is a composite of a toner core containing a polyester resin and a plurality of core external particles each attached to the surface of the toner core. The shell layer contains a thermosetting nitrogen-containing resin. The core externally added particles are silica particles having amino groups on the surface.

  According to the present invention, it is possible to provide a toner for developing an electrostatic latent image that is excellent in all of heat-resistant storage stability, low-temperature fixability, and chargeability. Further, according to the present invention, in addition to this effect or instead of this effect, there may be an effect that it is possible to improve the film formation stability of the shell layer.

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.

The number average particle diameter of the powder is the number average value of the equivalent circle diameter of primary particles (diameter of a circle having the same area as the projected area of the particles) measured using a microscope unless otherwise specified. . 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 a value measured according to “JIS (Japanese Industrial Standard) K7121-2012” using a differential scanning calorimeter (“DSC-6220” manufactured by Seiko Instruments Inc.) unless otherwise specified. It is. 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.

  The chargeability means the chargeability in frictional charging unless otherwise specified. The strength of positive chargeability (or strength of negative chargeability) in frictional charging can be confirmed by a known charge train or the like.

  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, acrylonitrile and methacrylonitrile may be collectively referred to as “(meth) acrylonitrile”.

  The toner according to the exemplary embodiment can be suitably used for developing an electrostatic latent image. 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. 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 electrostatic latent image is formed on a photoconductor (for example, a surface layer portion of a photoconductor drum) based on image data. Next, the formed electrostatic latent image is developed using a developer containing toner. In the developing process, toner (for example, toner charged by friction with a carrier or blade) on a developing sleeve (for example, a surface layer portion of a developing roller in the developing device) disposed in the vicinity of the photosensitive member is converted into an electrostatic latent image. A toner image is formed on the photoreceptor by adhering. In the subsequent transfer step, the toner image on the photosensitive member is transferred to an intermediate transfer member (for example, a transfer belt), and then the toner image on the intermediate transfer member is further transferred to a recording medium (for example, paper). Thereafter, the toner is heated and pressed by a fixing device (fixing method: nip fixing using a heating roller and a pressure roller) to fix the toner on the recording medium. As a result, an image is formed on the recording medium. For example, a full color image can be formed by superposing four color toner images of black, yellow, magenta, and cyan. The fixing method may be a belt fixing method.

  The toner particles contained in the toner according to the exemplary embodiment include a core (hereinafter referred to as a toner core) and a shell layer (capsule layer) formed on the surface of the toner core. 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. A shell layer is a film | membrane comprised from resin substantially. By covering the toner core that melts at a low temperature with a shell layer (resin film) having excellent heat resistance, it is possible to achieve both heat-resistant storage stability and low-temperature fixability of the toner. Additives may be dispersed in the resin constituting the shell layer. Hereinafter, a material for forming the shell layer is referred to as a shell material.

  The toner according to this embodiment is an electrostatic latent image developing toner having the following 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 partially covering the surface of the composite core. The composite core is a composite of a toner core containing a polyester resin and a plurality of core external particles attached to the surface of the toner core. The shell layer contains a thermosetting nitrogen-containing resin. The core externally added particles are silica particles having amino groups on the surface.

  In order to improve the heat resistant storage stability of the toner, it is preferable to cover the surface of the toner core with a film of a thermosetting resin. However, if the entire surface of the toner core is covered with a thermosetting resin film, the low-temperature fixability of the toner tends to deteriorate. In order to achieve both the heat resistant storage stability and the low-temperature fixability of the toner, it is preferable to partially cover the surface of the toner core with a thermosetting resin film (shell layer).

  In order to improve the low-temperature fixability of the toner, the toner core preferably contains a polyester resin. However, a toner core containing a polyester resin tends to have a relatively strong negative chargeability. In the positively chargeable toner, in order to ensure sufficient positive chargeability of the toner, it is preferable to cover the toner core containing the polyester resin with a film (shell layer) of the nitrogen-containing resin. This is because the nitrogen-containing resin tends to have a relatively strong positive chargeability.

  In the toner having the above basic configuration, the surface of the composite particle (composite core) in a state where a plurality of core external additive particles are adhered to the surface of the toner core is covered with a shell layer. The presence of the core-added particles is considered to improve the stability of the film formation of the shell layer and strengthen the bond between the toner core and the shell layer. Specifically, it is considered that the adhesion between the toner core and the shell layer is improved by the penetration of the shell material into the irregularities on the surface of the toner core derived from the core externally added particles due to capillary action.

  When the particles externally added to the surface of the toner core containing the polyester resin (core externally added particles) are untreated silica particles (hereinafter sometimes referred to as silica base), the core externally added particles (silica base) Is easily detached from the toner core. Both polyester resins and silica substrates tend to have a relatively strong negative charge. For this reason, it is considered that the toner core containing the polyester resin and the core externally added particles (silica substrate) are electrically repelled from each other.

  In the toner having the above basic configuration, the surface of the composite core is partially covered with the shell layer. The composite core is a composite of a toner core containing a polyester resin and a plurality of core external particles attached to the surface of the toner core. The core externally added particles are silica particles having an amino group on the surface (hereinafter sometimes referred to as N-silica particles). N-silica particles tend to have a relatively strong positive charge. When the particles externally added to the surface of the toner core containing the polyester resin (core externally added particles) are N-silica particles, the core externally added particles (silica substrate) are hardly detached from the toner core. The reason for this is considered that the toner core containing the polyester resin and the core externally added particles (N-silica particles) are electrically attracted to each other. N-silica particles can be produced, for example, by treating the surface of a silica substrate with a compound having an amino group (surface treatment agent).

  In the toner having the above basic configuration, the surface of the composite core is partially covered with the shell layer. The toner core of the composite core contains a polyester resin. For this reason, it becomes easy to ensure sufficient low-temperature fixability of the toner. The shell layer contains a thermosetting nitrogen-containing resin (hereinafter sometimes referred to as N-thermosetting resin). N-thermosetting resins tend to have high strength and relatively strong positive chargeability. For this reason, the toner having the above basic configuration tends to be excellent in all of positive chargeability, low-temperature fixability, and heat-resistant storage stability.

  In the toner having the above basic configuration, the core additive particles are present at the interface between the toner core and the shell layer. Such core-added particles tend to cause distortion in the shell layer to form a portion having a weak strength (a portion easily broken) in the shell layer. The presence of a portion that is easily broken in the shell layer makes it easy to ensure sufficient low-temperature fixability of the toner even when the toner core is covered with a hard shell layer containing an N-thermosetting resin.

  When the surface of the composite core is partially covered with the shell layer, the surface of the toner core includes the core additive particles that are completely covered with the shell layer and the core additive particles that are at least partially exposed from the shell layer. There is a high possibility of doing. Of the core additive particles present on the surface of the toner core, the core additive particles that are at least partially exposed from the shell layer are easily detached from the toner core. However, in the toner having the above basic configuration, the toner core and the core externally added particles are electrically attracted to each other, so that the core externally added particles are prevented from being detached from the toner core. Further, in the toner having the above basic configuration, the surface of the core externally added particles exposed from the shell layer has an amino group. For this reason, on the surface of the toner particles, both the surface of the shell layer and the surface of the core externally added particles have strong positive chargeability based on nitrogen (N), and it becomes easy to ensure sufficient positive chargeability of the toner. . Further, the core externally added particles present in the core exposed region (region of the core surface region that is not covered by the shell layer) can contribute to improvement of the heat resistant storage stability of the toner.

  Hereinafter, an example of toner particles (particularly, toner mother particles) contained in the toner having the above 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, as shown in FIG. 2, a plurality of core additive particles 13 are attached to the surface of the toner core 11. Therefore, the plurality of core external additive particles 13 are present at the interface between the toner core 11 and the shell layer 12. The toner core 11 and the plurality of core external additive particles 13 attached to the surface thereof constitute a composite (composite core). The toner core 11 contains a polyester resin. The shell layer 12 contains a thermosetting nitrogen-containing resin. The core externally added particles 13 are silica particles having an amino group on the surface.

  The surface of the shell layer 12 has convex portions P corresponding to the core external additive particles 13. Specifically, in the surface region of the shell layer 12, the region where the core external additive particles 13 are present under the shell layer 12 is higher than the region where the core external additive particles 13 are not present under the shell layer 12. . The convex portion P functions as a spacer between the toner particles, and improves the heat resistant storage stability of the toner.

  The shape of the core external additive particle 13 is, for example, spherical. However, the shape of the core external additive particle 13 is arbitrary as long as it is particulate, may be hemispherical, may be elliptical, may be hemispherical, It may be polyhedral (for example, octahedral) or irregularly shaped.

  In the example shown in FIG. 2, the core external additive particles 13 that are completely covered by the shell layer 12 and the core external additive particles 13 that are entirely exposed from the shell layer 12 (for example, the most in FIG. There are core external additive particles 13) located on the left side and core external additive particles 13 partially exposed from the shell layer 12 (for example, the second core external additive particle 13 from the left in FIG. 2).

  In order to achieve both heat-resistant storage stability and low-temperature fixability of the toner, it is preferable that the shell layer covers an area of 50% to 90% of the surface area of the toner core. The area ratio of the surface area of the toner core covered by the shell layer (hereinafter referred to as the shell coverage) is obtained by, for example, photographing the surface of the toner particles with an electron microscope, It can be measured by analyzing using image analysis software. Moreover, in order to make a shell coverage into a suitable ratio, it is preferable that the thickness of a shell layer is 1 nm or more and 20 nm or less. As shown by a dimension D in FIG. 2, the thickness of the shell layer is determined from the surface of the toner core 11 to the shell layer 12 in a region where the core additive particles 13 are not present at the interface between the toner core 11 and the shell layer 12. This corresponds to the dimension up to the surface, and corresponds to the dimension from the surface of the core additive particle 13 to the surface of the shell layer 12 in the region where the core additive particle 13 exists at the interface between the toner core 11 and the shell layer 12. The thickness of the shell layer can be measured by analyzing a TEM (transmission electron microscope) image of the cross section of the toner particles using commercially available image analysis software (for example, “WinROOF” manufactured by Mitani Corporation). If the thickness of the shell layer is not uniform in one toner particle, four equally spaced locations (specifically, two straight lines that are perpendicular to each other at the approximate center of the cross section of the toner particle are drawn. The thickness of the shell layer is measured at each of the four points where the straight line intersects the shell layer, and the arithmetic average of the four measured values obtained is taken as the evaluation value of the toner particles (shell layer thickness). The boundary between the toner core and the shell layer can be confirmed, for example, by selectively dyeing only the shell layer of the toner core and the shell layer. When the boundary between the toner core and the shell layer is unclear in the TEM photographed image, a characteristic element contained in the shell layer in the TEM photographed image is formed by combining TEM and electron energy loss spectroscopy (EELS). By performing the mapping, the boundary between the toner core and the shell layer can be clarified.

  In order to improve the heat-resistant storage stability of the toner by forming convex portions functioning as spacers on the surface of the shell layer with the core external additive particles, the number average primary particle diameter of the core external additive particles is 60 nm or more and 80 nm or less. It is preferable. When the particle diameter of the core external additive particles is too large, the core external additive particles are easily detached from the toner core. However, in the toner having the above basic configuration, since the bond between the toner core and the core additive particles is strong, the core additive particles having a large particle diameter can be used.

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 particles may include a shell external additive (powder of shell external particles). When the toner particles include a shell external additive, the toner particles include a toner base particle and a plurality of shell external particles. The shell externally added particles are attached to the surface of the toner base particles. In the toner having the above basic configuration, the toner base particles include a composite core (toner core and core externally added particles) and a shell layer. When omitting the shell external additive, the toner base particles correspond to the toner particles.

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

  In order to ensure sufficient toner fixability even during high-speed fixing, the glass transition point of the binder resin (the binder resin having the highest mass ratio when the toner core contains multiple types of binder resins) (Tg) is preferably 30 ° C. or higher and 60 ° C. or lower. Also, in order to ensure sufficient toner fixability even during high-speed fixing, softening of the binder resin (when the toner core contains multiple types of binder resins, the binder resin having the highest mass ratio) It is preferable that a point (Tm) is 60 degreeC or more and 150 degrees C or less.

  In the toner having the basic structure described above, the toner core contains a polyester resin. The polyester resin is composed of one or more polyhydric alcohols (more specifically, aliphatic diols, bisphenols, trihydric or higher alcohols, etc. as shown below) and one or more polyhydric carboxylic acids ( More specifically, it can be obtained by polycondensation with divalent carboxylic acid or trivalent or higher carboxylic acid as shown below.

  Preferred examples of the aliphatic diols include ethylene glycol, diethylene glycol, triethylene glycol, neopentyl glycol, 1,2-propanediol, α, ω-alkanediol (more specifically, 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.

  Preferred examples of the polyester resin contained in the toner core include one or more bisphenols (more specifically, bisphenol A ethylene oxide adduct or bisphenol A propylene oxide adduct) and one or more aromatics. And a monomer copolymer containing carboxylic acid (more specifically, terephthalic acid or trimellitic acid).

  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. The amount of the colorant is preferably 1 part by mass or more and 20 parts by mass or less with respect to 100 parts by mass of the binder resin.

  The toner core may contain a black colorant. An example of a black colorant is carbon black. The black colorant may be a colorant that is toned to black using a yellow colorant, a magenta colorant, and a cyan colorant. You may use the magnetic powder mentioned later as a black coloring agent.

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

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

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

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

(Release agent)
The toner core may contain a release agent. The release agent is used, for example, for the purpose of improving the fixing property or offset resistance of the toner.

  Examples of the release agent in the toner core include ester wax, polyethylene wax, polypropylene wax, fluororesin wax (for example, Teflon (registered trademark) -containing wax), Fischer-Tropsch wax, paraffin wax, and 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 order to improve the compatibility with the polyester resin (binder resin) in the toner core, the release agent is preferably an ester wax (for example, carnauba wax) or a polyethylene wax. One of these release agents may be used alone, or two or more thereof 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.

[Core external particles]
In the toner having the above-described basic configuration, the surface of the composite particle (composite core) in a state where a plurality of core external additive particles are attached to the surface of the toner core is covered with a shell layer. For example, the toner core (powder) and the core external additive (powder of core external additive particles) are stirred together, and the core external additive particles adhere to the surface of the toner core with physical force (physical bonding). To do. The core externally added particles are N-silica particles (silica particles having an amino group on the surface).

  The silica substrate (untreated silica particles) used in the core externally added particles may be silica particles produced by a dry method (more specifically, a combustion method or a deflagration method), or a wet method. (More specifically, silica particles produced by a sedimentation method, a gel method, or a sol-gel method) may be used. Combustion method silica particles (fumed silica particles) are silica particles obtained by burning a silane compound. The deflagration silica particles are silica particles obtained by explosive combustion of metallic silicon powder. Precipitated silica particles are silica particles obtained by advancing a neutralization reaction between sodium silicate and a mineral acid (for example, sulfuric acid) in an alkaline pH region to aggregate primary particles into blocks and settle them. Gel silica particles are silica particles obtained by generating an aggregate in a state where the neutralization reaction between sodium silicate and mineral acid (for example, sulfuric acid) is advanced in an acidic pH range and the growth of primary particles is suppressed. It is. The sol-gel silica particles are silica particles obtained by hydrolysis and condensation polymerization of metal alkoxide.

  In order to suppress the liberation rate of the core externally added particles, it is preferable to use sol-gel silica particles (silica particles produced by the sol-gel method) as the silica substrate. Si (silicon atoms) in the silica structure is three-dimensionally bonded by “Si—O” bonds. However, in the sol-gel silica particles, “—O—” of the “Si—O” bond in the silica structure is partially terminated with “H” to become “—OH”. The sol-gel method includes a hydrolysis step and a condensation step. A silane compound having “—OH” (hydroxyl group) is produced during the production (hydrolysis step). Hereinafter, specific examples of the sol-gel method will be described.

  First, a silane compound is added to a mixed solution (more specifically, a mixed solution of ammonia water, alcohol, and water) of a polar medium (hydrophilic organic solvent) containing a basic substance and water. Preferable examples of the silane compound include tetraalkoxysilane (more specifically, tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, or tetrabutoxysilane), or tetraphenoxysilane. Note that the silane compound put into the mixed solution may be an initial condensate of the silane compound.

  In the hydrolysis step, functional groups (for example, alkoxy groups or aryloxy groups) of the silane compound are hydrolyzed in the mixed solution. The functional group of the silane compound is replaced with “—OH” (hydroxyl group) by hydrolysis. Some of the functional groups of the silane compound may remain unreacted. However, in the presence of an alkali catalyst, when one functional group in a molecule is hydrolyzed, hydrolysis of the remaining three functional groups in the molecule is accelerated, and a functional group (for example, an alkoxy group or an aryloxy group) Group) remains unreacted.

  In the subsequent condensation step, a dehydration condensation reaction takes place between the hydroxyl groups, and Si (silicon atom) is three-dimensionally bonded with a “Si—O” bond like “—Si—O—Si—O—” The viscosity becomes higher. As a result, a sol is obtained. When the dehydration condensation reaction proceeds in the obtained sol and the condensation product (three-dimensional network structure) further increases, a gel in which the whole is connected by one network is obtained. Then, spherical silica particles (sol-gel method silica particles) are obtained by heat-treating the obtained gel at a high temperature. The particle diameter of the sol-gel method silica particles can be adjusted by changing, for example, the mixing ratio of the raw materials, the supply rate of the raw materials, and the conditions of the condensation process (more specifically, the reaction temperature or the stirring speed).

The surface of the N-silica particles may have an amino group in a form such as “—Si— (CH ₂ ) ₃ —NH ₂ ”. As the surface treatment agent for imparting an amino group to the surface of the silica substrate, one or more compounds selected from the group consisting of aminosilane compounds, aminoalkylsilane compounds, and amino-modified silicone oils are preferable. When such a compound is used as a surface treatment agent, a silyl group having an amino group at the end (more specifically, an aminosilyl group or an aminoalkylsilyl group) may be imparted to the surface of the silica substrate. it can. As an aminoalkylsilane compound (specifically, aminosilane coupling agent) for surface-treating a silica substrate, 3-aminopropyltrialkoxysilane (more specifically, 3-aminopropyltrimethoxysilane or 3-amino) is used. Propyltriethoxysilane, etc.), 3- (2-aminoethylamino) propyltrialkoxysilane (more specifically, 3- (2-aminoethylamino) propyltrimethoxysilane, or 3- (2-aminoethylamino) ) Propyltriethoxysilane, etc.), 3- (2-aminoethylamino) propyl dialkoxymethylsilane (more specifically, 3- (2-aminoethylamino) propyldimethoxymethylsilane, etc.), 3-aminopropyltri Alkoxysilane (more specifically, 3-aminopropyl Rimethoxysilane, etc.), N-phenyl-3-aminopropyltrialkoxysilane (more specifically, N-phenyl-3-aminopropyltrimethoxysilane, N-phenyl-3-aminopropyltriethoxysilane, etc.) Or 3-triethoxysilyl-N- (1,3-dimethyl-butylidene) propylamine is particularly preferred.

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 substrate) —OH” + “B (coupling agent) —OH” → “A—O—B” + H ₂ O) occurs with a hydroxyl group present on the surface of the silica substrate. By such a reaction, the amino group is imparted to the surface of the silica substrate by chemically bonding the silane coupling agent having an amino group and the silica substrate. 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). N-silica particles (silica substrate provided with amino groups) tend to have a stronger positive charge than silica substrates (untreated silica particles).

  The method of surface treating the silica substrate may be a dry method or a wet method. Specific examples of the method for surface treating the silica substrate include a method of dropping or spraying the surface treatment agent on the silica substrate while stirring the silica substrate at a high speed; a solution in which the surface treatment agent is dissolved in a solvent (for example, an organic solvent). A method of putting a silica substrate into the solution while stirring is mentioned.

[Shell layer]
In the toner having the above basic configuration, the toner core and a plurality of core external additive particles (N-silica particles) attached to the surface thereof constitute a composite (composite core). For example, by stirring together a toner core (powder) and a core external additive (powder of core externally added particles), part of the core externally added particles (bottom part) are embedded in the surface layer part of the toner core, and physical The core additive particles adhere to the surface of the toner core with a specific force (physical bonding). The shell layer partially covers the surface of the composite core. For example, by chemically reacting the composite core and the shell material in the liquid, the shell layer is bonded (chemically bonded) to the surface of the composite core (particularly, the surface of the toner core). The shell layer contains an N-thermosetting resin (thermosetting nitrogen-containing resin).

  The shell layer is, for example, one or more N-thermosetting resins selected from the group consisting of melamine resins, urea resins, sulfonamide resins, glyoxal resins, guanamine resins, aniline resins, and polyimide resins. It is preferable to contain. The polyimide resin has a nitrogen element in the molecular skeleton. For this reason, the shell layer containing a polyimide resin tends to have strong cationic properties. Examples of the polyimide resin include a maleimide polymer or a bismaleimide polymer (more specifically, an amino bismaleimide polymer or a bismaleimide triazine polymer).

  In order to form a high-quality shell layer on the surface of the composite core, the shell layer is an N-thermosetting resin (hereinafter referred to as amino) produced by condensation polymerization of a compound having an amino group and an aldehyde (for example, formaldehyde). It is preferable to contain aldehyde resin. The melamine resin is a condensation polymer of melamine and formaldehyde. The urea resin is a condensation polymer of urea and formaldehyde. Glyoxal resin is a polycondensation product of a reaction product of glyoxal and urea and formaldehyde.

  Examples of monomers that can be used to synthesize N-thermosetting resins include methylol melamine, melamine, methylolated urea (more specifically, dimethylol dihydroxyethylene urea), urea, benzoguanamine, acetoguanamine. Or spiroguanamine. When synthesizing an aminoaldehyde resin, it is possible to proceed with resin synthesis (polymerization reaction) without adding an aldehyde separately by using methylolated product as a resin raw material (monomer or prepolymer). Become. In order to form a good quality shell layer on the surface of the composite core, it is preferable to use a water-soluble monomer in the synthesis of the resin constituting the shell layer.

  In order to improve the low-temperature fixability of the toner, the shell layer contains a thermoplastic nitrogen-containing resin (hereinafter sometimes referred to as N-thermoplastic resin) in addition to the N-thermosetting resin. It is preferable. A preferred example of the N-thermoplastic resin is polyacrylamide.

  When the shell layer contains a resin other than the N-thermosetting resin (for example, N-thermoplastic resin) in addition to the N-thermosetting resin, sufficient heat-resistant storage stability of the toner and sufficient shell layer In order to ensure the film formation stability, it is preferable that 30% by mass or more of the resin constituting the shell layer is an N-thermosetting resin.

[Shell external additive]
A shell external additive (powder of shell external additive particles) may be attached to the surface of the toner base particles. For example, by stirring together the toner base particles (powder) and the shell external additive (powder), a part (bottom part) of the shell external particles is embedded in the surface layer of the toner base particles, The external shell particles adhere to the surface of the toner base particles with a sufficient force (physical bonding). The shell external additive is used, for example, to improve the fluidity or handleability of the toner. In order to fully exhibit the function of the shell external additive while suppressing the detachment of the shell external additive from the toner particles, the amount of the shell external additive (when using multiple types of shell external additives) The total amount of these shell external additives) is preferably 0.5 parts by mass or more and 10 parts by mass or less with respect to 100 parts by mass of the toner base particles.

  As the shell externally added particles, inorganic particles are preferable, and silica particles or metal oxide particles (specifically, alumina, titanium oxide, magnesium oxide, zinc oxide, strontium titanate, barium titanate, etc.) are used. 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 shell externally added particles. One type of shell external additive may be used alone, or a plurality of types of shell external additives may be used in combination.

  In order to improve the fluidity or handleability of the toner, it is preferable to use inorganic particles having a particle diameter of 0.005 μm or more and 1.000 μm or less as the shell externally added particles. In order to make the shell external additive function as a spacer to improve the heat resistant storage stability of the toner, it is preferable to use resin particles having a particle diameter of 50 nm or more and 150 nm or less as the shell external additive particles.

  The shell externally added particles may be surface-treated. 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.

[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)
Examples of the method of fixing the core externally added particles on the surface of the toner core include a mixing device (more specifically, an FM mixer manufactured by Nippon Coke Kogyo Co., Ltd. or a Nauter mixer (registered trademark) manufactured by Hosokawa Micron Co., Ltd. And the like, and a method in which the toner core and the core additive particles (N-silica particles) are mixed under the condition that the core additive particles are not buried in the toner core. By stirring the toner core and the core externally added particles together, the core externally added particles adhere to the surface of the toner core by physical force (physical bonding). As a result, a composite core (composite of a toner core and core-added particles) is obtained.

  As the mixing device, for example, an FM mixer (manufactured by Nippon Coke Kogyo Co., Ltd.) can be used. The FM mixer includes a mixing tank with a temperature adjusting jacket, and further includes a deflector, a temperature sensor, an upper blade, and a lower blade in the mixing tank. When mixing the material (more specifically, powder or slurry, etc.) charged into the mixing tank using an FM mixer, the material in the mixing tank is swung in the vertical direction by rotating the lower blade. To flow. This causes convection of the material in the mixing tank. The upper blade rotates at a high speed and gives a shearing force to the material. The FM mixer applies a shearing force to the material, thereby allowing the material to be mixed with a strong mixing force.

(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, hydrochloric acid is added to ion-exchanged water to prepare a weakly acidic (for example, pH selected from 3 to 5) aqueous medium. Subsequently, a shell material (eg, methylol melamine and acrylamide) is added to the pH adjusted aqueous medium. 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. 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. In order to favorably advance the formation of the shell layer, the holding temperature is preferably 40 ° C. or higher and 95 ° C. or lower, and more preferably 50 ° C. or higher and 80 ° C. or lower. Subsequently, 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. While maintaining the temperature of the liquid at a high temperature (or during the temperature increase), the polymerization reaction of the shell material on the surface of the composite core (for example, in-situ polymerization reaction) is performed between the composite core and the shell material. It is considered that the reaction (immobilization of the shell layer) proceeds. The shell material is chemically bonded to the composite core to form a 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.

  Subsequently, the toner mother particle dispersion is neutralized using, for example, sodium hydroxide. 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, the toner base particles and the shell external addition particles (for example, silica particles) are mixed using, for example, a mixer (more specifically, FM mixer manufactured by Nippon Coke Kogyo Co., Ltd.) Shell external additive particles are adhered to the surface of the toner base particles. When a spray dryer is used in the drying step, the drying step and the shell external addition step can be performed simultaneously by spraying a dispersion of the shell external addition particles (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. Moreover, even if it does not adjust pH of a liquid, when reaction for forming a shell layer advances favorably, you may omit a pH adjustment process. Moreover, you may omit the shell external addition process. When the shell external additive particles are not adhered to the surface of the toner base particles (the shell external addition step is omitted), the toner base particles correspond to the toner particles. As a material for synthesizing the resin, a prepolymer may be used instead of the monomer, if necessary. In order to obtain a predetermined compound, a salt, ester, hydrate, or anhydride of the compound may be used as a raw material. In order to produce the toner efficiently, it is preferable to form a large number of toner particles simultaneously. The toner particles produced at the same time are considered to have substantially the same configuration.

  Examples of the present invention will be described. Table 1 shows toners TA-1 to TA-8 and TB-1 to TB-8 (each toner for developing an electrostatic latent image) according to Examples or Comparative Examples. Table 2 shows the core external additive particles CA-1 to CA-10 used for the production of the toner shown in Table 1.

  Hereinafter, a production method, an evaluation method, and an evaluation result of toners TA-1 to TA-8 and TB-1 to TB-8 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.

[Toner Production Method]
(Synthesis of polyester resin PES-1)
A reaction vessel with a capacity of 5 L equipped with a thermometer (thermocouple), dehydration tube, nitrogen introduction tube, and stirring device (stirring blade) is set in an oil bath, and BPA-PO (bisphenol A propylene oxide addition) is placed in the vessel. Product) 1575 g, BPA-EO (bisphenol A ethylene oxide adduct) 163 g, fumaric acid 377 g, and catalyst (dibutyltin oxide) 4 g were added. Subsequently, after making the inside of the container a nitrogen atmosphere, the temperature inside the container was raised to 220 ° C. using an oil bath while stirring the contents of the container. Then, the contents of the container were reacted for 8 hours (specifically, polymerization reaction) while distilling by-product water under the conditions of nitrogen atmosphere and temperature of 220 ° C.

  Subsequently, the inside of the container was decompressed, and the contents of the container were further reacted for 1 hour (specifically, polymerization reaction) under the conditions of a decompressed atmosphere (pressure: 60 mmHg) and a temperature of 220 ° C. Thereafter, the temperature in the vessel was lowered to 210 ° C., and then 336 g of trimellitic anhydride was added to the vessel and reacted for 1 hour in a reduced pressure atmosphere (pressure: about 60 mmHg) and a temperature of 210 ° C. Thereafter, the container contents were taken out of the container and cooled to obtain a polyester resin PES-1 (non-crystalline polyester resin).

(Synthesis of polyester resin PES-2)
A reaction vessel with a capacity of 5 L equipped with a thermometer (thermocouple), dehydration tube, nitrogen introduction tube, and stirring device (stirring blade) is set in an oil bath, and BPA-PO (bisphenol A propylene oxide addition) is placed in the vessel. Product) 420 g, BPA-EO (bisphenol A ethylene oxide adduct) 1235 g, 714 g of terephthalic acid, and 4 g of catalyst (dibutyltin oxide) were added. Subsequently, the contents of the container were reacted at a temperature of 220 ° C. for 8 hours. Subsequently, the contents of the container were reacted for 1 hour in a reduced-pressure atmosphere (pressure 8.3 kPa). Thereafter, the container contents were taken out of the container and cooled to obtain a polyester resin PES-2 (non-crystalline polyester resin).

(Production of toner core)
100 parts by mass of binder resin (polyester resin PES-1 or PES-2 shown in Table 1 defined for each toner) and colorant (CI Pigment Blue 15: 3, component: copper phthalocyanine pigment) 5 parts by mass and 5 parts by mass of a release agent (ester wax: “Nissan Electol (registered trademark) WEP-3” manufactured by NOF Corporation) are mixed using an FM mixer (manufactured by Nippon Coke Industries, Ltd.). did.

Subsequently, the obtained mixture was melt-kneaded using a twin-screw extruder (“PCM-30” manufactured by Ikegai Co., Ltd.). Thereafter, the obtained kneaded material was cooled. Subsequently, the cooled kneaded product was pulverized using a mechanical pulverizer (“Turbo Mill” manufactured by Freund Turbo). 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 6 μm was obtained.

(Preparation of silica substrates S-1 to S-3)
A silica substrate S-1 having a number average primary particle size of 38 nm, a silica substrate S-2 having a number average primary particle size of 25 nm, and a silica substrate S-3 having a number average primary particle size of 64 nm were prepared. These silica substrates S-1 to S-3 were sol-gel silica particles (powder) prepared through the hydrolysis step, the condensation step, and the high-temperature heat treatment described above. As a mixed liquid of the hydrophilic organic solvent and water, a mixed liquid of ammonia water, ethanol and ion exchange water was used, and tetraethoxysilane was used as the silane compound. By changing the conditions of the condensation step, the particle size of each silica substrate was adjusted to a desired value. As the high-temperature heat treatment, heat treatment was performed at a temperature of 100 ° C. for 48 hours.

(Preparation of core external additive particle CA-1)
While stirring 200 parts by mass of the silica substrate S-1 in a stainless steel container with a stirrer, 3-aminopropyltriethoxysilane (“KBE-903” manufactured by Shin-Etsu Chemical Co., Ltd.) was added to the silica substrate in the container. ) 1.4 parts by mass were sprayed. After the spraying, the inside of the container was kept for 10 hours under a nitrogen atmosphere and a temperature of 60 ° C., and then the temperature inside the container was raised to keep the inside of the container for 5 hours under a nitrogen atmosphere and a temperature of 150 ° C. Thereafter, residual volatile components in the container were removed with a nitrogen stream to obtain core externally added particles CA-1.

(Preparation of core external additive particle CA-2)
The core externally added particles CA-2 were prepared by replacing 3-aminopropyltriethoxysilane (KBE-903) 1.4 parts by mass with 3-aminopropyltriethoxysilane (“KBE-” manufactured by Shin-Etsu Chemical Co., Ltd.). 903 ") 1.0 parts by mass and hexamethyldisilazane (" SZ-31 "manufactured by Shin-Etsu Chemical Co., Ltd.) 1.4 parts by mass are the same as the production method of the core-added particles CA-1. there were.

(Preparation of core external additive particle CA-3)
The core external additive particle CA-3 was prepared by using hexamethyldisilazane (“SZ-31” manufactured by Shin-Etsu Chemical Co., Ltd.) 1 instead of 1.4 parts by mass of 3-aminopropyltriethoxysilane (KBE-903) 1 Except for using 4 parts by mass, it was the same as the method for preparing the core-added particles CA-1.

(Preparation of core external additive particles CA-4)
The core external additive particle CA-4 was prepared by using the same method except that the silica base S-2 (200 parts by mass) was used instead of the silica base S-1 (200 parts by mass). It was the same as the method.

(Preparation of core external additive particles CA-5)
The core external additive particle CA-5 was prepared by using the same method except that silica base S-3 (200 parts by mass) was used instead of silica base S-1 (200 parts by mass). It was the same as the method.

(Preparation of core externally added particles CA-6 to CA-10)
As the core external additive particle CA-6, hydrophobic fumed silica particles (“AEROSIL (registered trademark) NA50Y” manufactured by Nippon Aerosil Co., Ltd., surface treatment agent: silicone oil and aminosilane, number average primary particle size: about 35 nm) Prepared.

  Hydrophobic fumed silica particles (“AEROSIL R972” manufactured by Nippon Aerosil Co., Ltd., surface treatment agent: dimethyldichlorosilane (DDS), number average primary particle size: about 16 nm) are prepared as the core externally added particles CA-7. did.

  Hydrophobic fumed silica particles (“AEROSIL R805” manufactured by Nippon Aerosil Co., Ltd., surface treatment agent: octylsilane, number average primary particle size: about 12 nm) were prepared as the core externally added particles CA-8.

  Silica substrate S-1 was prepared as the core external additive particle CA-9.

  As the core externally added particles CA-10, hydrophilic fumed silica particles (“AEROSIL 130” manufactured by Nippon Aerosil Co., Ltd., number average primary particle size: about 16 nm) were prepared.

(Core external addition process)
100 parts by mass of the toner core produced by the above-described procedure, and 2 parts by mass of core external additive particles (one of the core external additive particles CA-1 to CA-10 shown in Table 1 defined for each toner) Using an FM mixer (“FM-10B” manufactured by Nippon Coke Kogyo Co., Ltd.), the mixture was mixed for 10 minutes under the conditions of a rotation speed (stirring blade) of 3500 rpm and a jacket temperature of 20 ° C. As a result, a toner core (composite core) having core-added particles adhered to the surface was obtained. Hereinafter, the obtained composite core (powder) may be referred to as a pre-encapsulation toner.

  In addition, in the production of the toner TB-8, the core external addition process was not performed. Further, in the production of the toner TB-7, the following shell layer forming step to drying step were not performed.

(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, dilute hydrochloric acid was added to the flask to adjust the pH of the flask contents to 4.

  Subsequently, a shell material (a raw material for synthesizing the resin shown in “shell layer” in Table 1 specified for each toner) was added to the flask. For example, in the production of the toner TA-1, only the raw material for synthesizing the melamine resin was added as the shell material. In the production of the toner TA-7, only the raw material for synthesizing the urea resin was added as the shell material. Further, in the production of the toner TA-8, as a shell material, a raw material for synthesizing a melamine resin and a raw material for synthesizing polyacrylamide were added. In the production of the toner TB-6, only a raw material for synthesizing polyacrylamide was added as a shell material.

  As a raw material for synthesizing the melamine resin, an aqueous solution of hexamethylol melamine initial polymer (“Milben (registered trademark) Resin SM-607” manufactured by Showa Denko KK) was used. An aqueous solution of methylolated urea (“BECKAMINE (registered trademark) J-300S” manufactured by DIC Corporation) was used as a raw material for synthesizing the urea resin. As a raw material for synthesizing polyacrylamide, an aqueous solution of acrylamide (“BECKAMINE A-1” manufactured by DIC Corporation) was used. When only the raw material for synthesizing the melamine resin was added as the shell material, the amount added was 0.2 mL. When only the raw material for synthesizing the urea resin was added as the shell material, the amount added was 3.0 mL. When only the raw material for synthesizing polyacrylamide was added as the shell material, the amount added was 3.0 mL. Further, in the production of the toner TA-8, 2.0 mL of an aqueous solution of hexamethylol melamine initial polymer (milben resin SM-607) and 2.0 mL of an aqueous solution of acrylamide (BECKAMINE A-1) were added.

  Subsequently, 300 g of the composite core prepared in the above-described procedure (however, the toner core in the production of toner TB-7) was added to the flask, and the flask contents were sufficiently stirred. 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. Subsequently, the flask contents were stirred at a temperature of 70 ° C. for 2 hours. As a result, a shell layer was formed on the surface of the composite core (the toner core in the production of toner TB-7) in the liquid, and a dispersion of toner base particles was obtained.

  Subsequently, the pH of the toner mother particle dispersion was adjusted to 7 using sodium hydroxide (neutralized), and the toner mother particle dispersion was cooled to room temperature (about 25 ° C.).

(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 wet cake-like toner mother particles were put in a vacuum shelf dryer and dried for 24 hours under the conditions of a vacuum degree of 1 kPa and a temperature of 40 ° C. As a result, dried toner base particles (powder) were obtained. Hereinafter, the obtained toner base particles (powder) may be referred to as toner after encapsulation.

(Shell external addition process)
Subsequently, using an FM mixer (“FM-10B” manufactured by Nippon Coke Kogyo Co., Ltd.) under the conditions of a rotational speed of 3500 rpm and a jacket temperature of 20 ° C., 100 parts by mass of the toner base particles obtained as described above, and hydrophobicity Silica particles (“AEROSIL (registered trademark) RA-200H” manufactured by Nippon Aerosil Co., Ltd., content: dry silica particles surface-modified with trimethylsilyl groups and amino groups, number average primary particle size: about 12 nm) 0.7 mass Part, conductive titanium oxide particles (“EC-100” manufactured by Titanium Industry Co., Ltd., substrate: TiO ₂ particles, coating layer: Sb-doped SnO ₂ film, number average primary particle size: about 0.35 μm) 1.0 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 containing a large number of toner particles (toners TA-1 to TA-8 and TB-1 to TB-8) were obtained.

[Evaluation method]
The evaluation method of each sample (toners TA-1 to TA-8 and TB-1 to TB-8) is as follows. For each of the toners TB-7 and TB-8, the core external addition step or the shell layer forming step was not performed, so the liberation rate of the core external addition particles was not measured. For toner TB-7, no shell layer was formed, so the film formation stability was not evaluated.

(Free rate of core external particles)
In the production process of each sample (toners TA-1 to TA-8 and TB-1 to TB-6), the toner before encapsulation (composite core) and the toner after encapsulation (toner mother particles) were measured. Each of the toner before encapsulation and the toner after encapsulation was subjected to fluorescent X-ray analysis to obtain a fluorescent X-ray spectrum. Then, by comparing the fluorescent X-ray spectrum of the pre-encapsulated toner with the fluorescent X-ray spectrum of the encapsulated toner, the liberation rate of the core externally added particles was determined. Details of the X-ray fluorescence analysis and how to determine the liberation rate were as follows.

<Fluorescence X-ray analysis>
0.5 g of a measurement target (toner before encapsulation or toner after encapsulation) was set in a molding machine, and was pressure-molded at a pressure of 10 MPa using the molding machine to produce a cylindrical pellet having a diameter of 20 mm. Subsequently, the obtained pellet is subjected to fluorescent X-ray analysis under the following conditions, and the fluorescent X-ray spectrum including the peak derived from Si (silicon) (horizontal axis: energy, vertical axis: intensity (number of photons)) Obtained.
・ Analyzer: Scanning X-ray fluorescence analyzer (“ZSX” manufactured by Rigaku Corporation)
-Spectral crystal: PET (pentaerythritol)
・ X-ray tube (X-ray source): Rh (Rhodium)
Excitation conditions: tube voltage 50 kV, tube current 30 mA
・ Measurement element: Si (silicon)

<How to determine the liberation rate of core external additive particles>
Based on the fluorescent X-ray spectra obtained for the pre-encapsulated toner and the post-encapsulated toner by the fluorescent X-ray analysis, the liberation rate of the core externally added particles was calculated. Specifically, the peak intensity X _A (unit: kcps) derived from the core external additive particles of the toner after encapsulation (specifically, the Kα ray of Si in the core external additive particles) and the core external additive particles of the toner before encapsulation. From the peak intensity X _B (unit: kcps) derived from (specifically, the Kα line of Si in the core externally added particles), the core according to the formula “X _T = 100 × (X _B −X _A ) / X _B ” It was calculated liberation percentage X _T of external particles.

Free factor X _T of the obtained core outer additive particles is evaluated and if it is less than 5.0% ○ (good), was evaluated as × (not good) if more than 5.0%.

(Film deposition stability)
In the production process of each sample (toners TA-1 to TA-8, TB-1 to TB-6, and TB-8), the encapsulated toner was measured. 20 mg of a measurement target (toner after encapsulation), 1 mL of a surfactant (sodium alkyl ether sulfate) and 50 mL of an electrolytic solution (“ISOTON-2” manufactured by Beckman Coulter, Inc.) were mixed. Subsequently, the resulting mixture was subjected to ultrasonic irradiation at a frequency of 20 kHz for 3 minutes using an ultrasonic disperser (manufactured by ASONE Corporation “VS-D100”). As a result, a dispersion for evaluation was obtained. Subsequently, the volume particle size distribution of the evaluation dispersion was measured using a particle size distribution measuring apparatus (“Coulter Counter Multisizer 3” manufactured by Beckman Coulter, Inc.) under the conditions of an aperture diameter of 100 μm and the number of measured particles of 50000. Then, to determine the volume median diameter from the measured volume particle size distribution (D _50).

  When the obtained volume median diameter was 7 μm or less, it was evaluated as ◯ (good), and when it exceeded 7 μm, it was evaluated as x (not good).

(Heat resistant storage stability)
3 g of a sample (toner) was put in a 20 mL polyethylene container, and the container was left to stand for 12 hours in an environment of a temperature of 23 ° C. and a humidity of 50% RH without a lid. Thereafter, the container was covered and the sealed container was heated in an oven set at 60 ° C. for 3 hours. Thereafter, the toner taken out from the oven 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 an aperture of 106 μm with a known mass. Then, the mass of the sieve containing the toner was measured, and 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 obtained degree of aggregation was 30% by mass or less, it was evaluated as ◯ (good), and when it exceeded 30% by mass, it was evaluated as x (not good).

(Toner scattering)
The ferrite carrier and the sample (toner) were mixed for 30 minutes using a ball mill to prepare a developer for evaluation (two-component developer). The ratio of the sample (toner) in the developer for evaluation was 10% by mass. A ferrite carrier is obtained by spraying 230 parts by mass of a resin solution (resin: 30 parts by mass of a silicone resin, solvent: 200 parts by mass of toluene) on 1000 parts by mass of a Mn—Mg ferrite core (powder) having a number average primary particle size of 35 μm. After coating, it was produced by performing a heat treatment at a temperature of 200 ° C. for 60 minutes.

  A multifunction machine (“TASKalfa 500ci” manufactured by Kyocera Document Solutions Inc.) was used as an evaluation machine. The evaluation developer was put into the developing device of the evaluation machine, and the sample (replenishment toner) was put into the toner container of the evaluation machine.

  Using the evaluation machine, continuous printing (printing durability test) of 200000 sheets at a fixing temperature of 150 ° C. and a printing rate of 5.0% was performed in a normal temperature and humidity environment (temperature 20 ° C., humidity 50% RH). . After the printing durability test, the entire sample (toner) scattered in the developing device of the evaluation machine was collected. Then, the mass of the collected toner was measured, and the measured mass of toner (toner scattering amount) was evaluated according to the following criteria.

  When the obtained toner scattering amount was less than 400 mg, it was evaluated as ◯ (good), and when it was 400 mg or more, it was evaluated as x (bad). For each of the toners TB-7 and TB-8, the evaluation result of the heat-resistant storage stability was poor, and thus toner scattering was not evaluated.

[Evaluation results]
Table 3 shows the evaluation results of toners TA-1 to TA-8 and TB-1 to TB-8. Table 3 shows the core external additive particle release rate, film-forming stability (volume median diameter of encapsulated toner), heat-resistant storage (toner aggregation after heating), and toner scattering (toner scattering amount). The measured value is shown.

  The toners TA-1 to TA-8 (toners according to Examples 1 to 8) each had the above-described basic configuration. Specifically, each of toners TA-1 to TA-8 includes a composite core (specifically, a composite of a toner core containing a polyester resin and a plurality of core external particles attached to the surface of the toner core), and a composite core. A plurality of toner particles including a shell layer partially covering the surface of the toner particles. The shell layer contained a thermosetting nitrogen-containing resin. The core externally added particles were silica particles having amino groups on the surface (see Tables 1 and 2). As confirmed by image analysis of the SEM image, the shell coverage was 50% or more and 90% or less for all of the toners TA-1 to TA-8 (see “Shell Layer” in Table 3). See "Coverage"). Further, the surface of the shell layer had a convex portion corresponding to the core-added particles of the composite core. Further, when the cross section of the toner particles was confirmed using a TEM (transmission electron microscope), the thickness of the shell layer was 1 nm or more and 20 nm or less in any of the toners TA-1 to TA-8 (Table 3). (See “Thickness” of “Shell layer” in the middle)

  As shown in Table 3, each of the toners TA-1 to TA-8 was excellent in heat resistant storage stability. In each of the toners TA-1 to TA-8, the shell layer could be formed while suppressing the release of the core externally added particles and the aggregation of the composite core. In addition, the toners TA-1 to TA-8 were excellent in low-temperature fixability and chargeability, respectively. Specifically, by forming an image using toners TA-1 to TA-8, it was possible to form a good image over a long period of time while suppressing toner scattering.

  In the toners TB-1 to TB-5 (the toners according to Comparative Examples 1 to 5), the liberation rate of the core externally added particles was large (see Table 3). It is considered that an electrical repulsive force is generated between the toner core and the core external additive particles, and the core external additive particles are released during the formation of the shell layer. In addition, it is considered that toner scattering is likely to occur due to the free core externally added particles contaminating the carrier.

  Toner TB-6 (the toner according to Comparative Example 6) was inferior in heat-resistant storage stability and film formation stability. It is considered that the bond between the toner core and the shell layer was weak. In addition, it is considered that toner scattering is likely to occur because the shell component (component of the shell layer) peeled off from the toner core contaminates the carrier.

  Toner TB-7 (the toner according to Comparative Example 7) was inferior in heat resistant storage stability. The reason is considered to be that the shell layer was not formed.

  Toner TB-8 (toner according to Comparative Example 8) was inferior in heat-resistant storage stability and film formation stability. It is considered that the bond between the toner core and the shell layer is weakened by the absence of the core additive particles at the interface between the toner core and the shell layer. Moreover, it is thought that the site | part which is easy to destroy was not formed in the shell layer.

  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.

10 Toner Base Particle 11 Toner Core 12 Shell Layer 13 Core External Additive Particle P Protrusion

Claims (8)

A plurality of toner particles comprising a composite core and a shell layer partially covering the surface of the composite core;
The composite core is a composite of a toner core containing a polyester resin and a plurality of core external additive particles attached to the surface of the toner core,
The shell layer contains a thermosetting nitrogen-containing resin,
The toner for electrostatic latent image development, wherein the core externally added particles are silica particles having amino groups on the surface.   The electrostatic latent image developing toner according to claim 1, wherein the surface of the silica particles has an aminoalkylsilyl group containing the amino group.   The electrostatic latent image developing toner according to claim 1, wherein the silica particles are sol-gel silica particles.   The electrostatic shell image developing toner according to claim 1, wherein the shell layer further contains polyacrylamide.   The composite core includes, as the core additive particles, the core additive particles that are completely covered by the shell layer, and the core additive particles that are at least partially exposed from the shell layer. 5. The electrostatic latent image developing toner according to any one of 4 above.   6. The electrostatic latent image developing toner according to claim 1, wherein a number average primary particle size of the core externally added particles is 60 nm or more and 80 nm or less.   The electrostatic latent image developing toner according to claim 1, wherein the shell layer contains a melamine resin and / or a urea resin as the thermosetting nitrogen-containing resin.   The electrostatic latent image according to claim 1, wherein the polyester resin is a copolymer of monomers including one or more bisphenols and one or more aromatic carboxylic acids. Development toner.

Images