JP2020046463A - Two-component developer and method for manufacturing the same - Google Patents

Abstract

To provide a two-component developer that is excellent in charge stability of toner.SOLUTION: A two-component developer of the present invention contains a carrier and a toner. The carrier includes carrier particles. The carrier particles each include a carrier core and a coat layer that covers a surface of the carrier core. The coat layer includes a thermosetting resin and first silica particles and is formed of a first area on the inside in a radial direction and a second area on the outside in the radial direction. The first area includes 99.9 mass% of the first silica particles, and the second area includes the remainder, 0.1 mass%. The content ratio of the first silica particles in the first area is 1.5 mass% or more and 2.5 mass% or less. The toner includes toner particles. The toner particles each include a toner base particle and second silica particles attached to a surface of the toner base particle. The difference (IP-IP) between the ionization potential IPof the first silica particles and the ionization potential of the second silica particles IPis -0.20 eV or more and 0.00 eV or less.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a two-component developer and a method for producing the same.

  In a two-component developer, for the purpose of improving the charging stability of the toner, for example, a method of using a nitrogen-containing resin and an ammonium salt compound in a coating layer in a carrier having a carrier core and a coating layer covering the carrier core Has been proposed (Patent Document 1).

JP 2009-180841 A

  However, the present inventors have found that the two-component developer described in Patent Document 1 has room for improvement from the viewpoint of toner charging stability.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to provide a two-component developer having excellent toner charge stability.

The two-component developer of the present invention contains a carrier and a toner. The carrier includes carrier particles. The carrier particles include a carrier core and a coat layer covering a surface of the carrier core. The coating layer contains a thermosetting resin and first silica particles, and is composed of a radially inner first region and a radially outer second region. In the first silica particles, 99.9% by mass is contained in the first region, and the remaining 0.1% by mass is contained in the second region. The thickness of the first region is 300 nm or more and 600 nm or less. The thickness of the second region is 400 nm or more and 600 nm or less. The pencil hardness on the surface of the coat layer is 7H or more and 10H or less. The content ratio of the first silica particles in the first region is from 1.5% by mass to 2.5% by mass. The toner includes toner particles. The toner particles include toner base particles and second silica particles attached to the surface of the toner base particles. Difference in ionization potential IP _B of the second silica particles to the ionization potential IP _A of the first silica particles (IP _A -IP _B) is less than -0.20eV 0.00eV.

The method for producing a two-component developer of the present invention is a method for producing a two-component developer comprising a carrier and a toner, wherein the carrier preparing step for preparing the carrier, the toner preparing step for preparing the toner, A mixing step of mixing a carrier and the toner. The carrier includes carrier particles. The carrier particles include a carrier core and a coat layer covering a surface of the carrier core. The carrier preparation step includes a first coating layer forming step of forming a first coating layer covering the surface of the carrier core, and a second coating layer forming a second coating layer covering the surface of the first coating layer. A forming step, and a heating step of heating the carrier core covered with the first covering layer and the second covering layer. The thickness of the first coating layer after the heating step is 300 nm or more and 600 nm or less. The first coating layer is formed by a first coating solution containing an uncured first thermosetting resin and first silica particles. The content ratio of the first silica particles in the cured residue of the first coating solution is from 1.5% by mass to 2.5% by mass. The thickness of the second coating layer after the heating step is 400 nm or more and 600 nm or less. The second coating layer is formed by a second coating solution containing an uncured second thermosetting resin. The pencil hardness on the surface of the coat layer is 7H or more and 10H or less. The toner preparation step includes a toner base particle preparation step of preparing toner base particles, and an external addition step of externally adding second silica particles to the surface of the toner base particles. Difference in ionization potential IP _B of the second silica particles to the ionization potential IP _A of the first silica particles (IP _A -IP _B) is less than -0.20eV 0.00eV.

  ADVANTAGE OF THE INVENTION The two-component developer of this invention and its manufacturing method can provide the two-component developer excellent in the charge stability of a toner.

FIG. 2 is a diagram illustrating an example of a cross section of carrier particles in a two-component developer according to the first embodiment of the present invention. FIG. 2 is a diagram illustrating an example of a cross section of carrier particles in a two-component developer according to the first embodiment of the present invention. FIG. 2 is a diagram illustrating an example of a cross section of toner particles in a two-component developer according to the first embodiment of the present invention.

  Hereinafter, preferred embodiments of the present invention will be described. The toner is an aggregate (for example, powder) of toner particles. The external additive is an aggregate (for example, powder) of external additive particles. The carrier is an aggregate (for example, powder) of carrier particles. If the evaluation results (values indicating the shape, physical properties, etc.) of the powder (more specifically, the powder of the toner particles, the powder of the external additive particles, the powder of the carrier particles, etc.) are not specified, , A number average of the values obtained by selecting a considerable number of particles from the powder and measuring each of those particles.

The measured value of the volume median diameter (D ₅₀ ) of the powder was measured using a laser diffraction / scattering type particle size distribution analyzer (“LA-950” manufactured by Horiba, Ltd.) unless otherwise specified. Median diameter.

  Unless otherwise specified, the number average primary particle diameter of the powder is the circle equivalent diameter of the primary particles measured using a scanning electron microscope (Haywood diameter: a circle having the same area as the projected area of the primary particles). Is the number average value. The number average primary particle diameter of the powder is, for example, a number average value of a circle equivalent diameter of 100 primary particles. The number average primary particle diameter of the particles refers to the number average primary particle diameter of the particles in the powder unless otherwise specified.

  Unless otherwise specified, the charging property means the charging property in tribocharging. The strength of the positive charge (or the strength of the negative charge) in the triboelectric charging can be confirmed by a known charging sequence or the like. For example, the toner is mixed with a standard carrier (standard carrier for negatively chargeable toner: N-01, standard carrier for positively chargeable toner: P-01) provided by the Imaging Society of Japan, and the mixture is stirred to rub the measurement target. Charge. Before and after frictional charging, the charge amount of the measurement object is measured by, for example, a charge amount measurement device (Q / m meter), and the measurement object having a larger change in the charge amount before and after the frictional charging has stronger chargeability. Indicates that

  Unless otherwise specified, the softening point (Tm) is a value measured using a Koka type flow tester (“CFT-500D” manufactured by Shimadzu Corporation). In the S-shaped curve (horizontal axis: temperature, vertical axis: stroke) measured by the Koka type flow tester, the temperature at which “(baseline stroke value + maximum stroke value) / 2” is equal to Tm (softening point). Equivalent to.

  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) measured by a differential scanning calorimeter, the temperature at the inflection point due to the glass transition (specifically, the extrapolation line and the fall of the baseline) The temperature at the intersection of the line with the extrapolation line) corresponds to Tg (glass transition point).

  The “principal component” of a material, unless otherwise specified, means the component that is most frequently contained in the material on a mass basis.

  Hereinafter, a compound and its derivative may be generically referred to by adding “system” after the compound name. When a polymer name is indicated by adding “system” after the compound name, it means that the repeating unit of the polymer is derived from the compound or its derivative. Acrylic and methacryl may be generically referred to as "(meth) acryl". Each component described below may be used alone or in combination of two or more, unless otherwise specified.

<First embodiment: two-component developer>
The first embodiment of the present invention relates to a two-component developer. The two-component developer according to the exemplary embodiment includes a carrier and a toner. The carrier includes carrier particles. The carrier particles include a carrier core and a coat layer covering the surface of the carrier core. The coat layer contains a thermosetting resin and first silica particles, and is composed of a radially inner first region and a radially outer second region. In the first silica particles, 99.9% by mass is contained in the first region, and the remaining 0.1% by mass is contained in the second region. The thickness of the first region is 300 nm or more and 600 nm or less. The thickness of the second region is 400 nm or more and 600 nm or less. The pencil hardness on the surface of the coat layer is 7H or more and 10H or less. The content ratio of the first silica particles in the first region is from 1.5% by mass to 2.5% by mass. The toner includes toner particles. The toner particles include toner base particles and second silica particles attached to the surface of the toner base particles. Difference in ionization potential IP _B of the second silica particles to the ionization potential IP _A first silica particles (IP _A -IP _B) is more than -0.20eV 0.00eV or less.

  The two-component developer according to the exemplary embodiment can be used for forming an image in, for example, an electrophotographic apparatus (image forming apparatus). In the two-component developer according to the exemplary embodiment, the toner is charged by stirring the carrier and the toner in the developing device.

  The two-component developer according to the exemplary embodiment is excellent in charge stability of the toner by having the above-described configuration. The reason will be described below. In order to improve the charging stability of the toner in the two-component developer, it is important to maintain the characteristics of the carrier used in the developing device for a long time. Here, one of the main factors for changing the characteristics of the carrier is contamination of carrier particles by components (particularly, external additives) contained in the toner. As a conventional technique for suppressing contamination of carrier particles, for example, there is a method in which the surface of a carrier core is covered with a coat layer that is easily worn, and the surface of the carrier particles is refreshed by abrasion of the coat layer. However, with such carrier particles, the capacitance increases due to the decrease in the thickness of the coat layer with use, and as a result, a phenomenon (charge-up) of excessively charging the toner particles is likely to occur. In addition, the carrier particles of such carrier particles tend to be exposed by the loss of the coat layer due to abrasion, and the amount of charge applied to the toner particles tends to decrease.

  The carrier particles in the two-component developer according to the present embodiment have a moderately hard surface of the coat layer (pencil hardness of 7H or more and 10H or less), and the coat layer is appropriately worn with use, so that surface contamination is caused. Can be suppressed. Further, the coat layer of the carrier particles is composed of a radially inner first region and a radially outer second region, and the first silica particles are unevenly distributed in the first region. The first region has a higher strength than the second region because the first silica particles play a role as a filler. As described above, since the carrier particles have excellent strength in the first region inside the coat layer, exposure of the carrier core due to disappearance of the coat layer can be suppressed. Further, the first silica particles have the same or slightly lower ionization potential than the second silica particles contained as an external additive in the toner particles. Therefore, when the carrier particles come into contact with the toner particles (especially, the second silica particles) via the first silica particles, the carrier particles give more charge than the case where they come into contact with the toner particles via the thermosetting resin. The amount tends to decrease. Therefore, in the two-component developer according to the present embodiment, when used for a long time, the amount of charge given to the toner particles due to the exposure of the first silica particles on the surface of the carrier particles is reduced, and the electrostatic charge of the carrier particles is reduced. Since an increase in the amount of charge applied to the toner particles due to an increase in the capacity acts in a direction to cancel each other, charge-up can be suppressed. As described above, the two-component developer according to the exemplary embodiment can suppress the contamination of the surface of the carrier particles, the charge-up, and the exposure of the carrier core, so that the charge stability of the toner is excellent.

  The two-component developer is obtained by mixing the carrier and the toner while stirring using, for example, a mixer (more specifically, a ball mill, a rocking mixer (registered trademark) or the like). The compounding amount of the toner with respect to 100 parts by mass of the carrier is preferably from 1 part by mass to 20 parts by mass, more preferably from 3 parts by mass to 15 parts by mass.

[Carrier]
The carrier includes carrier particles. FIG. 1 shows an example of a cross section of the carrier particles 1 included in the carrier. The carrier particles 1 include a carrier core 11 and a coat layer 12 that covers the surface of the carrier core 11. The coat layer 12 covers the entire surface of the carrier core 11.

  FIG. 2 is an enlarged view near the surface of the carrier particle 1. The coat layer 12 includes a first region 12a on the inner side in the radial direction and a second region 12b on the outer side in the radial direction. The coat layer 12 mainly includes a matrix 13 made of a thermosetting resin and a plurality of first silica particles 14 dispersed in the matrix 13. The first silica particles 14 are unevenly distributed in the first region 12 a in the coat layer 12. Specifically, of the first silica particles 14, 99.9% by mass is contained in the first region 12a, and the remaining 0.1% by mass is contained in the second region 12b.

In the coat layer 12, the position of the boundary line A between the first region 12a and the second region 12b can be obtained, for example, by the following method. First, the cross section of the carrier particles 1 is observed with an electron microscope, and a rectangular measurement region is determined. The measurement region includes the surface of the coat layer 12 and the interface between the carrier core 11 and the coat layer 12. In the measurement region, the width direction is parallel to the interface between the carrier core 11 and the coat layer 12, and the length in the width direction is 100 nm or more. If the interface between the carrier core 11 and the coat layer 12 is curved, the average line can be regarded as the interface. In the measurement region, the total area S ₁ of the first silica particles 14 existing in the coat layer 12 is calculated. Next, a virtual straight line parallel to the interface between the carrier core 11 and the coat layer 12 is set at an arbitrary position of the coat layer 12 in the measurement region, and the first silica particles 14 existing between the carrier core 11 and the virtual straight line are set. determine the area S _2. The area S ₂ of the first silica particles 14 existing between the virtual straight line and the carrier core 11 increases as the position of the virtual straight line is separated from the carrier core 11. A virtual straight line at a position where 100 × S ₂ / S ₁ is 99.9% is defined as a boundary line A between the first region 12a and the second region 12b.

  The carrier particles 1 have been described above with reference to FIGS. However, the carrier particles in the two-component developer according to the exemplary embodiment are not limited to the carrier particles shown in FIGS. Specifically, the surface of the carrier core may be partially exposed without being covered with the coat layer. Further, the coat layer may have a multilayer structure in which one or more interfaces exist. However, the coat layer preferably has a single-layer structure from the viewpoint of suppressing separation from the interface. Hereinafter, each configuration of the carrier particles will be described in detail.

(Carrier core)
The carrier core preferably contains a magnetic material. The carrier core may be particles of a magnetic material, and may be particles including a binder resin and particles of the magnetic material dispersed in the binder resin (hereinafter, may be referred to as a resin carrier core). Is also good.

  Examples of the magnetic material contained in the carrier core include ferromagnetic metals (more specifically, iron, cobalt, nickel, and alloys containing one or more of these metals), and ferromagnetic metal oxides. Can be Ferromagnetic metal oxides include ferrite and magnetite, which is one type of spinel ferrite. Examples of the ferrite include Ba ferrite, Mn ferrite, Mn-Zn ferrite, Ni-Zn ferrite, Mn-Mg ferrite, Ca-Mg ferrite, Li ferrite, Cu-Zn ferrite, and Mn-Mg-Sr ferrite. . As a method for manufacturing the carrier core, for example, a method including a step of pulverizing and firing a magnetic material can be exemplified. In the manufacture of the carrier core, the saturation magnetization of the carrier can be adjusted by changing the addition amount of the magnetic material (particularly, the ratio of the ferromagnetic material). Further, in the production of the carrier core, the circularity of the carrier core can be adjusted by changing the firing temperature. In addition, you may use a commercial item as a carrier core.

  Examples of the magnetic material particles used as the carrier core include ferrite particles. Ferrite particles tend to have sufficient magnetism for image formation with a two-component developer. Note that ferrite particles produced by a general production method do not have a perfect sphere but tend to have moderate irregularities on the surface. When the carrier core is ferrite particles (ferrite core), from the viewpoint of improving the adhesion between the surface of the ferrite core and the coat layer, the arithmetic average roughness of the surface of the ferrite core (for details, JIS (Japanese Industrial Standard) B0601) The arithmetic average roughness Ra) defined by -2013 is preferably from 0.3 μm to 2.0 μm.

  As the binder resin in the carrier core, a polyester resin, a urethane resin, or a phenol resin is preferable, and a phenol resin is more preferable. Examples of the magnetic material particles in the resin carrier core include particles containing one or more magnetic materials among the magnetic materials exemplified in the above magnetic material.

  In the carrier particles, the mass ratio of the carrier core to the total mass of the carrier core and the coat layer is preferably from 70% by mass to 99% by mass, and more preferably from 90% by mass to 97% by mass.

In order to obtain good developability, the volume median diameter (D ₅₀ ) of the carrier core is preferably 30 μm or more and 100 μm or less.

  The saturation magnetization of the carrier core can be, for example, not less than 50 emu / g and not more than 90 emu / g.

(Coat layer)
The thickness of the coat layer is preferably 800 nm or more and 1200 nm or less, more preferably 900 nm or more and 1100 nm or less. As the thickness of the coat layer increases, the increase in the capacitance of the carrier particles due to the wear of the coat layer tends to become gentler.

  The thickness of the first region of the coat layer is from 300 nm to 600 nm, preferably from 400 nm to 550 nm. By setting the thickness of the first region to 300 nm or more, even if there are irregularities on the surface of the carrier core and the thickness of the first region varies from region to region, the entire surface of the carrier core is covered by the first region. The area can be reliably coated. By setting the thickness of the first region to 600 nm or less, the first region can be exposed at a timing when the coat layer is worn and the capacitance of the carrier particles is sufficiently increased.

  The thickness of the second region of the coat layer is 400 nm or more and 600 nm or less, and more preferably 450 nm or more and 550 nm or less. When the thickness of the second region is 400 nm or more and 600 nm or less, the first region can be exposed at a timing when the coat layer is worn and the capacitance of the carrier particles is sufficiently increased.

  The thickness of the coat layer can be measured by using a commercially available image analysis software (for example, “WinROOF” manufactured by Mitani Corporation) to analyze a TEM (transmission electron microscope) photographed image of the cross section of the carrier particles. The cross section of the carrier particles can be prepared, for example, using a cross section sample preparation apparatus (“Cross Section Polisher (registered trademark)” manufactured by JEOL Ltd.). The cross section of the carrier particles may be dyed. When the thickness of the coat layer is not uniform in one specific carrier particle, four straight lines that are evenly spaced (specifically, two straight lines that are orthogonal to each other at the approximate center of the cross section of the carrier particle, The thickness of the coat layer is measured at each of the four points where the straight line intersects the coat layer), and the arithmetic average of the four measured values is used as the evaluation value (thickness of the coat layer) of the carrier particles. .

  The pencil hardness on the surface of the coat layer (that is, the pencil hardness in the second region) is from 7H to 10H, preferably from 7H to 8H. When the pencil hardness on the surface of the coat layer is relatively hard, that is, 7H or more and 10H or less, the coat layer is easily worn appropriately. As a result, since the surface of the carrier particles is refreshed with use, contamination by an external additive or the like contained in the toner is suppressed. The pencil hardness on the surface of the coat layer can be measured by the same method as described later in the examples or a method analogous thereto.

  On the surface of the carrier core, the area ratio of the region covered with the coat layer (coverage of the coat layer) is preferably from 90% to 100%, and more preferably from 95% to 100%. The coverage of the coat layer can be measured by the same method as the coverage of the shell layer in the toner core described later.

  The total content of the thermosetting resin and the first silica particles in the coat layer is preferably 90% by mass or more, and more preferably 99% by mass or more.

(Thermosetting resin)
As the thermosetting resin in the coating layer, for example, silicone resin, epoxy resin, melamine resin, urea resin, sulfonamide resin, glyoxal resin, guanamine resin, polyamideimide resin, phenol resin, alkyd resin, diallyl Examples include phthalate resin and polyimide resin. Examples of the polyamide-imide resin include a polyamide-imide resin having a siloxane bond (Si-O-Si). The thermosetting resin is a resin in which an uncured thermosetting resin (such as a prepolymer) is heated to form a crosslinked structure between molecules, or to increase the intermolecular force by imidization or the like. .

  As the thermosetting resin, a silicone resin or a melamine-based resin is preferable. As the silicone resin, a silicone resin having at least one of an alkyl group and an aryl group in a side chain is preferable. Examples of the alkyl group include an alkyl group having 1 to 5 carbon atoms (for example, a methyl group, an ethyl group, an n-propyl group, an iso-propyl group, a linear or branched butyl group, or a linear or branched butyl group). A pentyl group), and a methyl group is more preferable. As the aryl group, an aryl group having 6 to 14 carbon atoms (for example, a phenyl group, a naphthyl group or an anthracenyl group) is preferable, and a phenyl group is more preferable.

  The content of the thermosetting resin in the first region of the coat layer is preferably from 80.0% by mass to 98.5% by mass, and more preferably from 97.5% by mass to 98.5% by mass.

  The content of the thermosetting resin in the second region of the coat layer is preferably 80% by mass or more, and more preferably 99% by mass or more.

[First silica particles]
As the first silica particles, for example, particles containing silica as a main component (hereinafter sometimes referred to as a silica substrate) or particles obtained by subjecting a silica substrate to a surface treatment can be used.

  The silica substrate can be obtained, for example, by hydrolytic condensation of a silane compound. As a specific method of hydrolytic condensation of a silane compound, for example, a mixed solution of a basic substance, a polar medium (hydrophilic organic solvent) and water (more specifically, a mixed solution of ammonia, ethanol and water) And the like) and a method of reacting by adding a silane compound. The reaction temperature of the hydrolytic condensation can be, for example, 20 ° C or higher and 30 ° C or lower. Examples of the silane compound include tetraalkoxysilane (more specifically, tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, tetrabutoxysilane, and the like), and tetraphenoxysilane. In the hydrolytic condensation of the silane compound, an initial condensate of the silane compound may be added to the above-mentioned mixture instead of the silane compound.

  Examples of the surface treatment method for the silica substrate include a method of providing an amino group with an aminosilane compound, an aminoalkylsilane compound, or an amino-modified silicone oil.

The ionization potential IP _A of the first silica particles is preferably not less than 5.40eV or less 5.20 eV, preferably not more than more than 5.35eV 5.40ev. Thus, the ionization potential IP _A of the first silica particles With 5.20eV above 5.40eV or less, moderately suppress charge-up due to wear of the coating layer of carrier particles, the toner charge stability Can be further improved. The larger the ionization potential of the first silica particles, the stronger the tendency of the toner particles to positively charge the toner particles.

  When the first silica particles are particles obtained by subjecting a silica substrate to surface treatment, the ionization potential (that is, the ionization potential on the surface of the first silica particles) can be adjusted by, for example, a surface treatment method. Specifically, by giving an amino group to the surface of the silica substrate, its ionization potential can be reduced.

  The number average particle diameter of the first silica particles is preferably from 10 nm to 150 nm, more preferably from 30 nm to 80 nm.

  The content ratio of the first silica particles in the first region of the coat layer is from 1.5% by mass to 2.5% by mass, preferably from 1.8% by mass to 2.2% by mass. By setting the content ratio of the first silica particles in the first region to 1.5% by mass or more and 2.5% by mass or less, charge-up due to abrasion of the coat layer of the carrier particles is appropriately suppressed, and the toner particles The charging stability can be improved.

[toner]
The toner contained in the two-component developer according to the exemplary embodiment includes toner particles. FIG. 3 shows an example of a sectional structure of the toner particles 2 included in the toner. The toner particles 2 include toner base particles 21 and a plurality of second silica particles 22 attached to the surface of the toner base particles 21.

  The toner particles 2 have been described with reference to FIG. However, the toner particles in the two-component developer according to this embodiment are not limited to the toner particles shown in FIG. Specifically, the toner particles in the two-component developer according to the exemplary embodiment may be toner particles having a shell layer (hereinafter, may be referred to as capsule toner particles). The capsule toner particles include, for example, a toner core containing a binder resin, and a shell layer covering the surface of the toner core. The shell layer contains a resin. For example, by covering the toner core that melts at a low temperature with a shell layer having excellent heat resistance, the capsule toner particles can achieve both heat storage stability and low-temperature fixability of the toner. In the capsule toner particles, an additive may be dispersed in a resin constituting the shell layer. The shell layer may cover the entire surface of the toner core, or may partially cover the surface of the toner core. Further, the toner particles may further include an external additive other than the second silica particles adhered to the surface of the toner base particles. Hereinafter, each component of the toner particles will be described in detail.

(Toner mother particles)
In order to obtain a toner suitable for image formation, the volume median diameter (D ₅₀ ) of the toner base particles is preferably from 4 μm to 9 μm.

  The toner base particles contain, for example, a binder resin as a main component. The toner base particles may further contain an internal additive (for example, at least one of a colorant, a release agent, a charge control agent, and a magnetic powder) as necessary in addition to the binder resin.

(Binder resin)
As the binder resin, a polyester resin is preferable from the viewpoint of improving the low-temperature fixability of the toner. The content ratio of the binder resin in the toner base particles is preferably from 60% by mass to 95% by mass, and more preferably from 75% by mass to 90% by mass.

  Examples of the polyester resin include a crystalline polyester resin and an amorphous polyester resin. The toner base particles preferably contain both a crystalline polyester resin and an amorphous polyester resin. Since the toner base particles contain both the crystalline polyester resin and the amorphous polyester resin, the toner particles can be provided with a sharp melt property, and as a result, the heat resistance storage stability and the low-temperature fixability of the toner can be improved. . In the polyester resin contained in the toner mother particles, the content ratio of the amorphous polyester resin (100 × mass of the amorphous polyester resin / total mass of the crystalline polyester resin and the amorphous polyester resin) is 60% by mass or more. 97 mass% or less is preferable, and 85 mass% or more and 95 mass% or less are more preferable.

  A polyester resin is obtained by polycondensing one or more polyhydric alcohols with one or more polyhydric carboxylic acids. Examples of the polyhydric alcohol for synthesizing the polyester resin include dihydric alcohols (more specifically, diols or bisphenols) and trihydric or higher alcohols. Examples of the polyvalent carboxylic acid for synthesizing the polyester resin include a divalent carboxylic acid and a trivalent or higher carboxylic acid. Instead of the polycarboxylic acid, a polycarboxylic acid derivative capable of forming an ester bond by polycondensation (for example, a polycarboxylic acid anhydride and a polycarboxylic acid halide) may be used. In the synthesis of the polyester resin, another monomer (a monomer that is neither a polyhydric alcohol nor a polycarboxylic acid) may be used.

  Examples of the diols include ethylene glycol, diethylene glycol, triethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, neopentyl glycol, and 2-butene-1,4-diol. 1,5-pentanediol, 2-pentene-1,5-diol, 1,6-hexanediol, 1,4-cyclohexanedimethanol, dipropylene glycol, 1,4-benzenediol, polyethylene glycol, polypropylene glycol, And polytetramethylene glycol.

  Examples of the bisphenols include bisphenol A, hydrogenated bisphenol A, bisphenol A ethylene oxide adduct, and bisphenol A propylene oxide adduct.

  Examples of trihydric or higher alcohols include sorbitol, 1,2,3,6-hexanetetrol, 1,4-sorbitan, pentaerythritol, dipentaerythritol, tripentaerythritol, 1,2,4-butanetriol, 1,2,5-pentanetriol, glycerol, diglycerol, 2-methylpropanetriol, 2-methyl-1,2,4-butanetriol, trimethylolethane, trimethylolpropane, and 1,3,5-trihydroxy Methylbenzene is mentioned.

  Examples of divalent carboxylic acids include maleic acid, fumaric acid, citraconic acid, itaconic acid, glutaconic acid, phthalic acid, isophthalic acid, terephthalic acid, cyclohexanedicarboxylic acid, adipic acid, sebacic acid, azelaic acid, malonic acid, succinic acid Acids, alkyl succinic acids (more specifically, n-butyl succinic acid, isobutyl succinic acid, n-octyl succinic acid, n-dodecyl succinic acid, and isododecyl succinic acid), and alkenyl succinic acids (more specifically, , N-butenyl succinic acid, isobutenyl succinic acid, n-octenyl succinic acid, n-dodecenyl succinic acid, and isododecenyl succinic acid).

  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, 1,2,2 4-butanetricarboxylic acid, 1,2,5-hexanetricarboxylic acid, 1,3-dicarboxyl-2-methyl-2-methylenecarboxylpropane, 1,2,4-cyclohexanetricarboxylic acid, tetra (methylenecarboxyl) methane, 1,2,7,8-octanetetracarboxylic acid, pyromellitic acid, and empol trimer acid.

  As other monomers, for example, α, ω-alkanediol having 2 to 12 carbon atoms, α, ω-alkanedicarboxylic acid having 4 to 10 carbon atoms, styrene-based monomer, and acrylic acid-based monomer And the like.

  Examples of the α, ω-alkanediol having 2 to 12 carbon atoms include ethylene glycol (2 carbon atoms). Examples of the α, ω-alkanedicarboxylic acid having 4 to 10 carbon atoms include sebacic acid (10 carbon atoms). Examples of the styrene-based monomer include styrene, alkylstyrene (more specifically, α-methylstyrene, p-ethylstyrene, and 4-tert-butylstyrene), and hydroxystyrene (more specifically, p-hydroxy Styrene, and m-hydroxystyrene), and halogenated styrene (more specifically, α-chlorostyrene, o-chlorostyrene, m-chlorostyrene, and p-chlorostyrene). Examples of the acrylic acid-based monomer include (meth) acrylic acid, (meth) acrylamide, (meth) acrylonitrile, (meth) acrylic acid alkyl ester, and (meth) acrylic acid hydroxyalkyl ester. Examples of the alkyl (meth) acrylate include methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, iso-propyl (meth) acrylate, and n- (meth) acrylate. -Butyl, iso-butyl (meth) acrylate, and 2-ethylhexyl (meth) acrylate. Examples of the hydroxyalkyl (meth) acrylate include 2-hydroxyethyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, and (meth) acrylic acid 4 -Hydroxybutyl.

  Examples of the amorphous polyester resin include bisphenol A ethylene oxide adduct, bisphenol A propylene oxide adduct, amorphous polyester resin mainly containing terephthalic acid and fumaric acid, bisphenol A ethylene oxide adduct, bisphenol A propylene oxide adduct Amorphous polyester resin containing bisphenol A ethylene oxide adduct, bisphenol A propylene oxide adduct, terephthalic acid, dodecyl succinic anhydride and trimellitic anhydride as main materials. Crystalline polyester resins are preferred.

  As the crystalline polyester resin, a crystalline polyester resin containing ethylene glycol and suberic acid as main raw materials is preferable.

(Coloring agent)
The toner base particles preferably contain a colorant. As the colorant, a known pigment or dye can be used according to the color of the toner. For example, a black colorant and a color colorant can be used. When the toner base particles contain a colorant, the content is preferably from 1.0 to 20.0 parts by mass based on 100 parts by mass of the binder resin from the viewpoint of improving the image quality of an image formed by the toner. It is preferably at most 3.0 parts by mass and more preferably at most 10.0 parts by mass.

  Examples of the black colorant include carbon black. Examples of the color colorant include a yellow colorant, a magenta colorant, and a cyan colorant. Note that the toner may be toned to black using a combination of a yellow colorant, a magenta colorant, and a cyan colorant.

  Examples of the yellow colorant include a condensed azo compound, an isoindolinone compound, an anthraquinone compound, an azo metal complex, a methine compound, and an arylamide compound. 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 and 194), naphthol yellow S, Hansa yellow G, and C.I. I. Bat yellow.

  Examples of the magenta colorant include condensed azo compounds, diketopyrrolopyrrole compounds, anthraquinone compounds, quinacridone compounds, basic dye lake compounds, naphthol compounds, benzimidazolone compounds, thioindigo compounds, and perylene compounds. 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 and 254).

  Examples of the cyan coloring agent include a copper phthalocyanine compound, an anthraquinone compound, and a basic dye lake compound. Examples of the cyan colorant include C.I. I. Pigment Blue (1, 7, 15, 15: 1, 15: 2, 15: 3, 15: 4, 60, 62, and 66), phthalocyanine blue, C.I. I. Bat blue, and C.I. I. Acid Blue.

〔Release agent〕
The toner base particles preferably contain a release agent. The release agent is used, for example, for the purpose of imparting hot offset resistance to the toner. When the toner base particles contain a release agent, the content is preferably from 1.0 part by mass to 20.0 parts by mass with respect to 100 parts by mass of the binder resin from the viewpoint of improving the hot offset resistance of the toner. Or less, more preferably 5.0 parts by mass or more and 15.0 parts by mass or less.

  Examples of the release agent include aliphatic hydrocarbon waxes (eg, low molecular weight polyethylene, low molecular weight polypropylene, polyolefin copolymer, polyolefin wax, microcrystalline wax, paraffin wax, and Fischer-Tropsch wax), aliphatic hydrocarbons Oxides (eg, polyethylene oxide waxes and block copolymers of polyethylene oxide waxes), vegetable waxes (candelilla wax, carnauba wax, wood wax, jojoba wax, and rice wax), animal waxes (eg, , Beeswax, lanolin, and spermaceti), mineral waxes (eg, ozokerite, ceresin, and petrolatum), ester waxes based on fatty acid esters (eg, montanate ester wax, and mosquito wax) Tar waxes), and waxes in which some or all of the fatty acid ester is de-oxidized (e.g., deoxidized carnauba wax) and the like. As the release agent, an ester wax is preferable.

  When the toner base particles contain a release agent, a compatibilizer may be further added to the toner base particles in order to improve the compatibility between the binder resin and the release agent.

(Charge control agent)
The toner base particles 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 characteristics of the toner. The charge rising characteristic of the toner is an index of whether or not the toner can be charged to a predetermined charge level in a short time.

  By including a negatively chargeable charge control agent in the toner base particles, the anionicity of the toner base particles can be enhanced. Further, by adding a positively chargeable charge control agent to the toner base particles, the cationic properties of the toner base particles can be enhanced.

(Magnetic powder)
The toner base particles may contain magnetic powder. As the material of the magnetic powder, for example, a ferromagnetic metal (for example, iron, cobalt and nickel) or an alloy thereof, a ferromagnetic metal oxide (for example, ferrite, magnetite, and chromium dioxide), and a ferromagnetic treatment are performed. (For example, a carbon material to which ferromagnetism is imparted by heat treatment).

(Shell layer)
The shell layer contains, for example, a shell resin as a main component. As the shell layer, a layer substantially composed of a shell resin (for example, a layer having a shell resin content of 90% by mass or more) is preferable, and a layer containing only the shell resin is more preferable.

  From the viewpoint of improving the image quality of the image formed by the toner, the thickness of the shell layer is preferably from 10 nm to 100 nm. As a method for measuring the thickness of the shell layer, for example, the same method as the method for measuring the thickness of the coat layer in the carrier particles described above can be used.

(Second silica particles)
As the second silica particles, for example, a silica substrate or particles obtained by subjecting a silica substrate to a surface treatment can be used. As a method for preparing the silica substrate and a method for treating the surface of the silica substrate, for example, the same method as that described for the first silica particles can be used.

The ionization potential IP _B of the second silica particles is preferably not less than 5.50eV or less 5.30 eV, preferably not more than more than 5.35eV 5.45ev. Thus, the ionization potential IP _B of the second silica particles is set to be lower than or equal 5.50eV above 5.30 eV, easily adjust the difference in the ionization potential of the first silica particles and second silica particles to a suitable range .

  The number average particle diameter of the second silica particles is preferably from 10 nm to 150 nm, more preferably from 30 nm to 80 nm.

  The content of the second silica particles in the toner particles is preferably from 0.01 to 10.0 parts by mass, and more preferably from 0.1 to 5.0 parts by mass based on 100 parts by mass of the toner base particles. More preferably, the content is 0.5 part by mass or more and 3.0 parts by mass or less.

The difference in ionization potential IP _B of the second silica particles to the ionization potential IP _A first silica particles (IP _A -IP _B), not less than -0.20eV 0.00eV or less, more -0.05eV 0. 00 eV or less is more preferable. The difference (IP _A -IP _B) a With -0.20eV or 0.00eV or less, moderately suppress charge-up due to wear of the coat layers of the carrier particles, it is possible to further improve the toner charging stability .

(Other external additives)
Other external additives are external additives other than the second silica particles, and include external additive particles. As the external additive particles, inorganic particles are preferable. Examples of the inorganic particles include particles of metal oxides (more specifically, alumina, titanium oxide, magnesium oxide, zinc oxide, strontium titanate, and barium titanate). The number average primary particle diameter of the inorganic particles is preferably from 1 nm to 100 nm, more preferably from 5 nm to 40 nm.

<Second embodiment: Method for producing two-component developer>
The second embodiment of the present invention relates to a method for producing a two-component developer. The method for manufacturing a two-component developer according to the present embodiment is a method for manufacturing a two-component developer including a carrier and a toner, and includes a carrier preparing step for preparing a carrier, a toner preparing step for preparing a toner, and a carrier. And a mixing step of mixing the toner and the toner. The carrier includes carrier particles. The carrier particles include a carrier core and a coat layer covering the surface of the carrier core. The carrier preparation step includes a first coating layer forming step of forming a first coating layer covering the surface of the carrier core, and a second coating layer forming step of forming a second coating layer covering the surface of the first coating layer. Heating the carrier core coated with the first coating layer and the second coating layer. The thickness of the first coating layer after the heating step is from 300 nm to 600 nm. The first coating layer is formed by a first coating solution containing an uncured first thermosetting resin and first silica particles. The content ratio of the first silica particles in the cured residue of the first coating solution is from 1.5% by mass to 2.5% by mass. The thickness of the second coating layer after the heating step is 400 nm or more and 600 nm or less. The second coating layer is formed by a second coating solution containing an uncured second thermosetting resin. The pencil hardness on the surface of the coat layer is 7H or more and 10H or less. The toner preparation step includes a toner base particle preparation step of preparing toner base particles, and an external addition step of externally adding second silica particles to the surface of the toner base particles. Difference in ionization potential IP _B of the second silica particles to the ionization potential IP _A first silica particles (IP _A -IP _B) is more than -0.20eV 0.00eV or less.

  The method for producing a two-component developer according to the present embodiment is a suitable method for producing the two-component developer according to the first embodiment described above. Hereinafter, description of components overlapping with the first embodiment will be omitted.

[Carrier preparation step]
In this step, a carrier is prepared. This step includes a first coating layer forming step, a second coating layer forming step, and a heating step.

(First coating layer forming step)
In this step, a first coating layer that covers the surface of the carrier core is formed. The first coating layer is formed by a first coating solution containing an uncured first thermosetting resin and first silica particles. As a method for forming the first coating layer, for example, there is a method in which the first coating solution is applied to the carrier core and then heated. As a method of applying the first coating solution to the carrier core, for example, a method of immersing the carrier core in a liquid containing the first coating solution, or a method of spraying the liquid containing the first coating solution onto the carrier core in the fluidized bed Is mentioned.

  In the heating in this step, it is preferable that the uncured first thermosetting resin is not completely cured but is kept semi-cured. Therefore, the heating conditions may be, for example, a heating temperature of 160 ° C. or more and 200 ° C. or less, and a heating time of 20 minutes or more and 80 minutes or less.

  As the uncured first thermosetting resin, a resin (prepolymer or the like) corresponding to the thermosetting resin contained in the coat layer described in the first embodiment can be used.

  The first coating solution may further contain a curing agent corresponding to the uncured first thermosetting resin. When the first thermosetting resin is a silicone resin, for example, tetrabutyl orthotitanate or tetraisopropyl orthotitanate can be used as the curing agent. When the first thermosetting resin is a melamine resin, for example, an inorganic acid (for example, nitric acid) can be used as a curing agent. The content ratio of the curing agent in the first coating solution is preferably 0.1% by mass or more and 5.0% by mass or less with respect to 100 parts by mass of the cured residue.

(Second coating layer forming step)
In this step, a second coating layer that covers the surface of the first coating layer is formed. The second coating layer is formed by a second coating solution containing an uncured second thermosetting resin. As a method of forming the second coating layer, for example, there is a method of applying a second coating solution to a composite including a carrier core and a first coating layer that covers the surface of the carrier core. As a method of applying the second coating solution to the above-described composite, for example, a method similar to the method exemplified as the application method of the first coating solution may be used.

  The second coating solution may further contain a curing agent corresponding to the uncured second thermosetting resin. The type and content of the curing agent can be the same as the curing agent in the first coating solution.

  It is preferable that the first thermosetting resin and the second thermosetting resin are the same as each other. As described above, since the first thermosetting resin and the second thermosetting resin are the same, it is possible to improve the adhesion between the first coating layer and the second coating layer after the heating step.

(Heating process)
In this step, the carrier core coated with the first coating layer and the second coating layer is heated. Thereby, the first thermosetting resin in the first coating layer and the second thermosetting resin in the second coating layer are cured. As a result, the first and second regions of the coating layer are formed from the first and second coating layers, respectively, and the first and second coating layers adhere to each other. In addition, by semi-curing the first coating layer as described above, the migration of the first silica particles contained in the first coating layer to the second coating layer during the heating step can be substantially suppressed.

  As the heating conditions in this step, for example, the heating temperature can be 180 ° C. or more and 260 ° C. or less, and the heating time can be 40 minutes or more and 3 hours or less.

[Toner preparation process]
In this step, a toner is prepared. This step includes a toner base particle preparation step and an external addition step.

(Toner base particle preparation step)
In this step, toner base particles are prepared. The method for preparing the toner base particles is not particularly limited, and a known pulverizing method or a known aggregating method can be used, but it is preferable to use a pulverizing method. The obtained toner base particles may be directly subjected to an external addition step, or may be subjected to an external addition step after being covered with a shell layer.

  In one example of the pulverization method, first, a binder resin and an internal additive added as needed 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 material is pulverized and classified. Thereby, toner base particles are obtained.

  In one example of the agglomeration method, first, in an aqueous medium containing fine particles of a binder resin and, if necessary, an internal additive added, these fine particles are aggregated to a desired particle size. Thereby, agglomerated particles containing a binder resin and the like are formed. Subsequently, the obtained aggregated particles are heated to integrate the components contained in the aggregated particles. Thereby, toner base particles are obtained.

(External process)
In this step, the second silica particles are externally added to the surface of the toner base particles. As a specific method of attaching the second silica particles, for example, the toner base particles and the second silica particles are mixed using a mixer (for example, “Multipurpose Mixer” manufactured by Nippon Coke Industry Co., Ltd.). As a result, a toner including toner particles including the toner base particles and the second silica particles attached to the surface of the toner base particles is obtained.

  In this step, if necessary, an external additive other than the second silica particles may be externally added to the surface of the toner mother particles together with the second silica particles.

[Mixing process]
In this step, the carrier and the toner are mixed. As a method of mixing the carrier and the toner, for example, a method using a mixer (more specifically, a ball mill, a rocking mixer (registered trademark), or the like) is used.

  Hereinafter, the present invention will be described more specifically with reference to examples. However, the invention is not at all limited to the scope of the examples.

<Manufacture of two-component developer>
The two-component developers of Examples and Comparative Examples were produced by the following methods. First, silica particles used as the first silica particles or the second silica particles were prepared.

[Preparation of silica particles (S-3)]
2,450 g of ethanol was charged into the flask. 100 g of ion-exchanged water, 200 g of tetraethoxysilane (manufactured by Wako Pure Chemical Industries, Ltd.), and 100 g of 1% by mass ammonia water as a basic catalyst were further added to the flask. The reaction was carried out for a predetermined time (1 hour) while maintaining the internal temperature of the flask at 25 ° C. using a water bath. As a result, a silica substrate dispersion liquid in which the particulate silica substrate was dispersed in the solvent was obtained.

  Using a Buchner funnel, a wet cake-like silica substrate was collected from the silica substrate dispersion by filtration. Next, the silica substrate in the form of a wet cake was washed by being redispersed in ion-exchanged water. The washing operation by filtration of the silica substrate and redispersion in ion-exchanged water was repeated a total of three times to obtain a washed silica substrate.

  Next, 500 g of toluene (manufactured by Tokyo Chemical Industry Co., Ltd.) and 3-aminopropyltriethoxysilane (“KBE-903 manufactured by Shin-Etsu Chemical Co., Ltd.) are placed in a three-neck flask having a capacity of 1 L equipped with a thermometer and a stirring blade. 3), 3 g of n-propyltrimethoxysilane ("KBM-3033", manufactured by Shin-Etsu Chemical Co., Ltd.) and 50 g of the above-mentioned silica substrate. The reaction (surface treatment) was performed by maintaining the mixed solution at 80 ° C. for 2 hours. After the reaction, the reaction solution was boiled (temperature: 90 to 110 ° C.) for 2 hours to remove toluene, thereby obtaining silica particles (S-3). The number average particle diameter of the silica particles (S-3) was 50 nm.

[Preparation of silica particles (S-1), (S-2) and (S-4)]
Silica particles (S-1), (S-2) and (S-4) were prepared in the same manner as in the preparation of silica particles (S-3), except for the following changes. In the preparation of the silica particles (S-3), 3 g of 3-aminopropyltriethoxysilane (6 parts by mass with respect to 100 parts by mass of the silica substrate) was used in the surface treatment. On the other hand, in the preparation of the silica particles (S-1), (S-2) and (S-4), the amount of 3-aminopropyltriethoxysilane shown in Table 1 below was used in the surface treatment. The ionization potential of the obtained silica particles decreased as the amount of 3-aminopropyltriethoxysilane added increased.

(Measurement of ionization potential)
The ionization potential of the silica particles (S-1) to (S-4) was measured by the following method. The measurement object was put into the measurement cell. Specifically, the measurement object was filled into the concave portion of the measurement cell by pushing the measurement object from above using a slide glass. Thereafter, the measurement object overflowing from the measurement cell was removed by reciprocating the slide glass on the surface of the measurement cell. Then, the measuring cell filled with the object to be measured is set in a measuring device, and in an environment of a temperature of 22.5 ° C. and a humidity of 50% RH, a photoelectron spectrum (vertical axis: number of photoelectrons, horizontal axis: excitation energy) under the following conditions: Was measured.

(Measurement condition)
Measuring device: Atmospheric photoelectron spectroscopy device (“AC-3” manufactured by Riken Keiki Co., Ltd.)
Measurement principle: Low energy electron counting method Light source: UV lamp (deuterium lamp with lamp house)
Spectrometer: Nitrogen-substituted grating monochromator Measurement range (photoelectron measurement energy scanning range): 5.00 eV to 6.00 eV
Measurement interval: 0.01 eV
Excitation light intensity: 200 nW

In the above measuring device, the light emitted from the ultraviolet lamp was incident on the chamber replaced with nitrogen, the light amount was adjusted by the light amount adjusting device in the chamber, and was incident on the spectroscope. Further, the light whose wavelength was selected (energy selected) by the spectroscope was emitted into the atmosphere through a CaF ₂ window and collected on the surface of the measurement target. When light (excitation light) was applied to the surface of the measurement target, photoelectrons were emitted from the surface layer of the measurement target (specifically, a region at a depth of about 200 ° from the surface) due to the photoelectric effect. The photoelectrons were counted by an open counter.

  In the measurement of the ionization potential of the silica particles (S-1) to (S-4), the excitation energy at the point where the rise of the photoelectron count number occurred in the photoelectron spectrum was defined as the ionization potential [eV]. The measurement results are shown in Table 1 below.

  In Table 1 below, “APTS” indicates 3-aminopropyltriethoxysilane. "Parts by mass" indicates the amount of 3-aminopropyltriethoxysilane used per 100 parts by mass of the silica substrate.

[Preparation of toner]
An evaluation toner was obtained by the following method. First, a polyester resin (specifically, an amorphous polyester resin A, an amorphous polyester resin B, and a crystalline polyester resin A) used for the toner mother particles of the evaluation toner was synthesized.

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

(Synthesis of amorphous polyester resin B)
In a 10-L four-necked flask equipped with a thermometer (thermocouple), a dehydrating tube, a nitrogen introducing tube, and a stirrer, 1286 g of bisphenol A propylene oxide adduct, 2218 g of bisphenol A ethylene oxide adduct, and terephthalic acid 1603 g, tin (II) 2-ethylhexanoate 10 g, and gallic acid 2 g were added. Subsequently, the contents of the flask were reacted under a nitrogen atmosphere and a temperature of 230 ° C. until the conversion represented by the above formula became 90% by mass or more. Subsequently, the contents of the flask were reacted under a reduced pressure atmosphere (pressure 8.3 kPa) and a temperature of 230 ° C. until the softening point of the reaction product (resin) reached a predetermined temperature (111 ° C.). As a result, an amorphous polyester resin B having a softening point (Tm) of 111 ° C and a glass transition point (Tg) of 69 ° C was obtained.

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

(Synthesis of crystalline polyester resin A)
In a 10 L four-necked flask equipped with a nitrogen inlet tube, a dehydrating tube, a stirrer, and a thermometer (thermocouple), 2231 g of ethylene glycol, 5869 g of suberic acid, and 40 g of tin (II) 2-ethylhexanoate were placed. And 2 g of gallic acid. Subsequently, the contents of the flask were reacted for 4 hours under the conditions of a nitrogen atmosphere and a temperature of 180 ° C. Subsequently, the contents of the flask were reacted for 10 hours at a temperature of 210 ° C. Subsequently, the contents of the flask were reacted for 1 hour under reduced pressure atmosphere (pressure 8.3 kPa) and temperature 210 ° C. As a result, a crystalline polyester resin A having a softening point (Tm) of 78 ° C and an endothermic peak temperature of 74 ° C was obtained.

(Preparation of toner base particles)
Using an FM mixer (manufactured by Nippon Coke Industries, Ltd.), 300 g of the amorphous polyester resin A, 100 g of the amorphous polyester resin B, 600 g of the amorphous polyester resin C, and 100 g, release agent A (Carnauba wax special No. 1 manufactured by Kato Yoko Co., Ltd., component: carnauba wax), and release agent B (Nissan Elector (registered trademark) WEP- manufactured by NOF CORPORATION) 3 ", component: ester wax) 48 g, and 144 g of a coloring agent (" Colortex (registered trademark) Blue B1021 ", component: phthalocyanine blue) manufactured by Sanyo Dyeing Co., Ltd.) were mixed at a rotation speed of 2400 rpm.

Subsequently, using a twin-screw extruder (“PCM-30” manufactured by Ikegai Co., Ltd.), the obtained mixture was fed at a material supply speed of 5 kg / hour, a shaft rotation speed of 160 rpm, and a set temperature (cylinder temperature) of 100 ° C. Was melt-kneaded. Then, the obtained kneaded material was cooled. Subsequently, the cooled kneaded material was coarsely pulverized using a pulverizer (“Rotoplex (registered trademark) 16/8” manufactured by Hosokawa Micron Corporation). Subsequently, the obtained coarsely pulverized product was finely pulverized using a jet mill ("Ultrasonic Jet Mill I" manufactured by Nippon Pneumatic Industries, Ltd.). Subsequently, the obtained finely pulverized product was classified using a classifier ("Elbow Jet EJ-LABO" manufactured by Nippon Steel Mining Co., Ltd.). As a result, toner base particles having a volume median diameter (D ₅₀ ) of 6.8 μm were obtained.

(External process)
1.5 parts by mass of the silica particles (S-3) was added to 100 parts by mass of the toner base particles, and the mixture was stirred at 1700 rpm for 5 minutes using an FM mixer (manufactured by Nippon Coke Co., Ltd.), so that the surface of the toner base particles was Silica particles (S-3) were attached. As a result, an evaluation toner was obtained.

[Preparation of carrier]
In the preparation of the carrier, "EF-35B" manufactured by Powder Tech Co., Ltd. was used as the carrier core. This carrier core was a spherical ferrite core containing manganese, magnesium, strontium and iron (number-average particle diameter 35 μm, saturation magnetization 68 Am ² / kg).

(Preparation of resin solution)
Resin solutions (R-1) to (R-4) used for preparing the first coating solution and the second coating solution in forming the coat layer were prepared. As the resin solution (R-1), "KR-220L" manufactured by Shin-Etsu Silicone Co., Ltd. was used as it was. The resin solutions (R-2) to (R-4) were prepared by adding a specific amount of a curing agent to a commercially available raw material solution as shown in Table 2 below. In Table 2, "KR-220L" and "SR-2431" were solutions containing a methyl silicone resin. “KR-300” was a solution containing a silicone resin having a methyl group and a phenyl group. “SM-800” was a solution containing a modified melamine resin. The “addition amount” of the curing agent indicates a value obtained by “100 × the addition amount of the curing agent / the mass of the remaining resin solution”.

[Example 1]
The two-component developer of Example 1 was produced by the following method.

[Preparation of first coating solution]
Silica particles (S-3) were added to the resin solution (R-1) and stirred to obtain a silica particle-containing resin solution. The addition amount of the silica particles (S-3) was set so that the content ratio of the silica particles (S-3) in the cured residue of the silica particle-containing resin solution was 2.0% by mass. Toluene was added to the obtained silica particle-containing resin solution to obtain a first coating solution. The amount of toluene added was such that the concentration of the cured residue of the first coating solution (100 × the mass of the cured residue of the first coating solution / the mass of the first coating solution) was 10% by mass.

[Formation of First Coating Layer]
The first coating solution was spray-coated on the surface of the carrier core. Specifically, 100 parts by mass of the carrier core was charged into a fluid coating apparatus (“Multiplex MP-01” manufactured by Powrex Co., Ltd.) and allowed to flow in the apparatus. Then, 50 parts by mass of the first coating solution was added to the fluidized coating apparatus. Thereafter, the carrier core to which the first coating solution was applied was heated at 180 ° C. for 1 hour using an oven. As a result, first coated particles comprising a carrier core and a first coating layer covering the carrier core were obtained. When the first coating particles were observed with a scanning electron microscope (SEM) by the following method, the thickness of the first coating layer was 500 nm.

  Observation with a scanning electron microscope (SEM) was performed by the following method. After the particles to be measured are dispersed in a visible light curable resin ("Aronix (registered trademark) LCR D-800" manufactured by Toagosei Co., Ltd.), the resin is cured by irradiation with visible light to obtain a cured product. . Subsequently, the obtained cured product was processed using a knife and a file to obtain a rectangular plate-shaped thin slice sample having predetermined dimensions (length: 1 cm, width: 1 cm, thickness: 3 mm). Thereafter, the slice sample was processed under the following conditions using a cross-sectional sample manufacturing apparatus (“Cross Section Polisher (registered trademark) SM-09010” manufactured by JEOL Ltd., processing method: ion beam), and the sample to be measured was processed. A cross section of the particles was obtained.

(Processing conditions)
・ Ion acceleration voltage: 4.0 kV
-Gas used: argon (purity: 99.9999% or more, pressure: 0.15 MPa)
・ Processing time: 12 hours

  A cross section of the obtained particles was photographed at a magnification of 30,000 times using a scanning electron microscope (SEM) (“JSM-7900F” manufactured by JEOL Ltd.). Then, the thickness of the coating layer was measured by analyzing the SEM photographed image using image analysis software (“WinROOF” manufactured by Mitani Corporation). Specifically, two straight lines perpendicular to the center of the cross section of the carrier particle were drawn, and the thickness of the coating layer was measured at each of four points where the two straight lines intersected the coating layer. The arithmetic average value of the measured four thicknesses was defined as the thickness of the coating layer of the particles. Then, the thickness of the coating layer is measured for each of the 10 particles included in the particles to be measured, and the number average value of the measured thickness is evaluated as the evaluation value of the particles to be measured (the thickness of the first coating layer. ).

[Preparation of second coating solution]
Toluene was added to the resin solution (R-1) to obtain a second coating solution. The amount of toluene added was such that the concentration of the cured residue of the second coating solution (100 × the mass of the cured residue of the second coating solution / the mass of the second coating solution) was 10% by mass.

[Formation of Second Coating Layer]
The surface of the first coated particles was spray-coated with the second coating solution. Specifically, the entire amount of the above-mentioned first coated particles was charged into a fluid coating apparatus (“Multiplex MP-01” manufactured by Powrex Corporation) and allowed to flow in the apparatus. Then, 50 parts by mass of the second coating solution was added to the fluidized coating apparatus. As a result, second coated particles comprising a carrier core, a first coating layer covering the surface of the carrier core, and a second coating layer covering the surface of the first coating layer were obtained.

〔heating〕
The second coated particles were heated at 190 ° C. for 2 hours using an oven. When the second coated particles after heating were observed by SEM by the above-mentioned method, the first coated layer and the second coated layer were united to form a single coated layer (thickness: 1000 nm). From this, it is determined that the thickness of the second coating layer after the heating step is 500 nm.

When the second coated particles after heating were observed by SEM using the above-described method, the first silica particles were unevenly distributed radially inside the coat layer. Specifically, in the coat layer, the area S ₂ of the first silica particles contained in the region from the surface of the carrier core to a thickness of 500 nm is 99.9% of the total area S ₁ of the first silica particles. there were. That is, the thicknesses of the first coating layer and the second coating layer after heating were substantially the same as the thicknesses of the first region and the second region of the coating layer.

[Preparation of developer]
100 parts by mass of the above-described carrier and 8 parts by mass of the above-described toner for evaluation were charged into a powder mixer (“Locking Mixer (registered trademark)” manufactured by Aichi Electric Co., Ltd.). The contents were stirred using a mixing device for 30 minutes. Thus, a two-component developer of Example 1 was obtained.

  The two-component developers of Examples 2 to 10 and Comparative Examples 1 to 11 were produced in the same manner as in the production of the two-component developer of Example 1 except that the following points were changed in the preparation of the carrier. In each of the two-component developers, the thickness of the first region and the second region of the coat layer of the carrier particles was substantially the same as the thickness of the first coat layer and the second coat layer after heating.

[Example 2, Comparative Example 1, and Comparative Example 2]
In Example 2, Comparative Example 1 and Comparative Example 2, silica particles (S-2), (S-4) or (S-1) were used as the first silica particles instead of silica particles (S-3). Each was used.

[Comparative Example 3]
In Comparative Example 3, the resin solution (R-2) was used instead of the resin solution (R-1) as the resin solution used for preparing the first coating solution and the second coating solution. In Comparative Example 3, the heating conditions for the second coated particles were changed to 260 ° C. for 1 hour.

[Example 3, Example 4, Comparative Example 4 and Comparative Example 5]
In Example 3, Example 4, Comparative Example 4 and Comparative Example 5, the amount of the first coating solution added was changed to 32 parts by mass, 58 parts by mass, 28 parts by mass, or 62 parts by mass, respectively. As a result, in Example 3, Example 4, Comparative Example 4, and Comparative Example 5, the thickness of the first coating layer and the thickness of the first region of the coating layer were 320 nm, 580 nm, 280 nm, and 620 nm, respectively. .

[Example 5, Example 6, Comparative Example 6, and Comparative Example 7]
In Example 5, Example 6, Comparative Example 6, and Comparative Example 7, the added amount of the second coating solution was changed to 42 parts, 58 parts, 38 parts, or 62 parts by weight, respectively. As a result, in Example 5, Example 6, Comparative Example 6, and Comparative Example 7, the thickness of the second coating layer after heating and the thickness of the second region of the coating layer were 420 nm, 580 nm, 380 nm, or 620 nm, respectively. It became.

[Example 7, Example 8, Comparative Example 8, and Comparative Example 9]
In Example 7, Example 8, Comparative Example 8 and Comparative Example 9, the amount of the silica particles (S-3) was changed in the preparation of the silica particle-containing resin solution, and the silica particles (S-3) in the cured residue were changed. Was 1.6 mass%, 2.4 mass%, 1.4 mass%, or 2.6 mass%, respectively.

[Example 9]
In Example 9, the resin solution (R-3) was used instead of the resin solution (R-1) as the resin solution used for preparing the first coating solution and the second coating solution. In Example 9, the heating conditions for the second coated particles were changed to a temperature of 220 ° C. and 2 hours.

[Example 10]
In Example 10, the preparation method of the first coating solution and the second coating solution was changed as follows. In the preparation of the first coating solution, first, silica particles (S-3) were added to the resin solution (R-4) and stirred to obtain a silica particle-containing resin solution. The amount of the silica particles added was such that the content of the silica particles (S-3) in the cured residue of the silica particle-containing resin solution was 2.0% by mass. Ion exchange water was added to the obtained silica particle-containing resin solution to obtain a first coating solution. The amount of ion-exchanged water added was such that the concentration of the cured residue of the first coating solution (100 × the mass of the cured residue of the first coating solution / the mass of the first coating solution) was 10% by mass. The second coating solution was prepared by adding ion-exchanged water to the resin solution (R-4). The amount of ion-exchanged water added was such that the concentration of the cured residue of the second coating solution (100 × the mass of the cured residue of the second coating solution / the mass of the second coating solution) was 10% by mass.

  Further, in Example 10, the heating condition of the carrier core coated with the first coating solution was 250 ° C. for 1 hour, and the heating condition of the second coated particles was 250 ° C. for 1 hour.

[Comparative Example 10]
In Comparative Example 10, the first coating layer was formed using the solution used as the second coating solution in Example 1, and the second coating layer was formed using the solution used as the first coating solution in Example 1. That is, in Comparative Example 10, contrary to Example 1, the silica particles (S-3) were added to the second coating layer without adding the silica particles (S-3) to the first coating layer.

[Comparative Example 11]
In Comparative Example 11, the first coating layer and the second coating layer were formed using the solution used as the second coating solution in Example 1. That is, in Comparative Example 11, the silica particles (S-3) were not added to any of the first coating layer and the second coating layer.

[Method of measuring pencil hardness of coat layer]
For each carrier used in the preparation of the two-component developer of the examples and comparative examples, fluorescent X-ray analysis was performed under the following conditions, and the fluorescent X-ray spectrum (horizontal axis: energy, vertical axis: intensity (number of photons)) was determined. Obtained. The measurement element was a characteristic element in the coat layer located on the uppermost layer of the carrier particles. Specifically, for the carriers used for the preparation of the two-component developers of Examples 1 to 9 and Comparative Examples 1 to 11, Si (silicon) was used as the measurement element. For the carrier used for preparing the two-component developer of Example 10, the element to be measured was N (nitrogen).

(Conditions for X-ray fluorescence analysis)
・ Analyzer: Scanning fluorescent X-ray analyzer (“ZSX” manufactured by Rigaku Corporation)
・ X-ray tube (X-ray source): Rh (rhodium)
Excitation conditions: tube voltage 50 kV, tube current 50 mA
・ Measurement area (X-ray irradiation range): 30 mm in diameter

The peak intensity of the element to be measured was read from the obtained fluorescent X-ray spectrum. Hereinafter, the peak intensity of the measured element measured here is referred to as “initial intensity X _A ”.

  Next, a plurality of types of pencil core powders having different hardnesses were prepared, and the following stirring test was performed using each of the pencil cores in an environment at a temperature of 23 ° C. and a humidity of 50% RH. . The hardness of the core of each pencil was HB, F, 1H, 2H, 3H, 4H, 5H, 6H, 7H, 8H, 9H or 10H. The lead of each pencil was pulverized using a mortar, and then passed through a 635-mesh (mesh opening: 20 μm) sieve to obtain a powder having a particle diameter of 20 μm or less (hereinafter referred to as a pencil lead powder). In some cases).

(Stirring test)
1 g of a carrier to be measured and 0.1 g of a pencil lead powder having a predetermined hardness were placed in a sample bottle having a capacity of 5 mL. Subsequently, the sample bottle was stirred for 48 hours using a shaker mixer ("Tabler (registered trademark) mixer T2F" manufactured by Willy & Bacoffen (WAB)).

After the stirring test, the carrier component removed from the carrier particles by the pencil core powder and removed from the contents of the sample bottle and the pencil core powder are separated by suction (specifically, suction through a 635 mesh sieve). To obtain a carrier after the stirring test. Subsequently, the carrier after the stirring test was subjected to a fluorescent X-ray analysis under the above-described conditions to obtain a fluorescent X-ray spectrum. Then, the peak intensity of the element to be measured was read from the obtained fluorescent X-ray spectrum. Hereinafter, the peak intensity of the measured element measured here will be referred to as “strength after stirring X _B ”. Incidentally, in the stirring test, the higher the amount of the coating layer of carriers cut by the graphite powder increases, the intensity X _B After stirring tends to decrease.

From the initial intensity X _A and after stirring intensity X _B was measured as described above, based on the formula "coat layer wear amount _{= 100 × (X A -X B} ) / (X A) ", the wear amount coat layer I asked. When the shaving amount of the coat layer is less than 5%, it means that the surface of the coat layer of the carrier is harder than the core of the pencil used in the stirring test. The hardness of the hardest pencil core among the hardnesses of the pencil cores whose coating layer shaving amount was less than 5% was defined as the evaluation value (the pencil hardness of the surface of the coat layer) of the measurement target (carrier). For example, when a pencil lead having a hardness of 1H was used in the stirring test, the shaved amount of the coat layer was less than 5%. However, when a pencil lead having a hardness of 2H was used in the stirring test, the cut amount of the coat layer was 5%. In this case, the evaluation value (the pencil hardness of the surface of the coat layer) of the measurement object (carrier) was set to 1H. The evaluation results are shown in Tables 3 and 4 below.

<Evaluation>
The charging stability of the toners in the two-component developers of Examples and Comparative Examples was evaluated by the following method. The evaluation was performed in an environment at a temperature of 23 ° C. and a humidity of 50% RH. The evaluation results are shown in Tables 3 and 4 below.

  As the evaluation machine, a color printer ("FS-C5250DN" manufactured by Kyocera Document Solutions Inc.) was used. The two-component developers of the examples and the comparative examples were respectively charged into the developing device for cyan of the evaluation machine, and the above-described toner for evaluation was charged into the toner container for cyan of the evaluation machine.

  The two-component developer charged into the cyan developing device of the evaluation machine was subjected to an aging treatment for 2 minutes. For the two-component developer after the aging treatment, the charge amount of the toner (the charge amount of the toner contained in the two-component developer) was measured by the following method. The measured toner charge was defined as an initial charge [μC / g].

  Using an evaluation machine, 100,000 sheets of an image having a printing rate of 5% were printed on printing paper. The toner charge amount of the two-component developer after printing was measured again by the following method. The measured charge amount of the toner was defined as a charge amount after the durability test [μC / g].

The method for measuring the toner charge amount will be described. Specifically, first, the two-component developer to be evaluated was taken out from the cyan developing device of the evaluation machine. Next, 0.10 g of an evaluation target is put into a measurement cell of a Q / m meter (“MODEL 210HS-1” manufactured by Trek Corporation), and the evaluation target is sucked through a sieve (wire mesh) for 10 seconds to obtain only toner. Was isolated. Then, for the separated toner, the toner charge amount [μC / g] was calculated based on the following equation.
Toner charge amount [μC / g] = Total electricity amount of toner [μC] / mass of toner [g]

For each two-component developer, the charge variation rate [%] was calculated from the initial charge amount [μC / g] and the post-durability charge amount [μC / g] based on the following equation. The charge stability of the two-component developer can be evaluated as good when the charge fluctuation rate is less than 10% in absolute value (that is, more than -10% + less than 10%), and the charge fluctuation rate is 10% or more in absolute value. The case can be evaluated as defective.
Charge variation rate [%] = 100 × (charge amount after durability [μC / g] −initial charge amount [μC / g]) / initial charge amount [μC / g]

The two-component developers of Examples 1 to 10 each contained a carrier and a toner. The carrier contained carrier particles. The carrier particles had a carrier core and a coat layer covering the surface of the carrier core. The coat layer contained a thermosetting resin and first silica particles, and was composed of a radially inner first region and a radially outer second region. In the first silica particles, 99.9% by mass was contained in the first region, and the remaining 0.1% by mass was contained in the second region. The thickness of the first region was 300 nm or more and 600 nm or less. The thickness of the second region was 400 nm or more and 600 nm or less. The pencil hardness on the surface of the coat layer was 7H or more and 10H or less. The content ratio of the first silica particles in the first region was from 1.5% by mass to 2.5% by mass. The toner contained toner particles. The toner particles had toner base particles and second silica particles attached to the surface of the toner base particles. Difference in ionization potential IP _B of the second silica particles to the ionization potential IP _A first silica particles (IP _A -IP _B) was not less than -0.20eV 0.00eV or less. As shown in Tables 3 and 4, the two-component developers of Examples 1 to 10 each had good toner charge stability.

  On the other hand, the two-component developers of Comparative Examples 1 to 11 did not have the above-described configurations. As a result, the two-component developers of Comparative Examples 1 to 11 had poor toner charging stability. Hereinafter, the two-component developers of Comparative Examples 1 to 11 will be described in detail.

[Comparative Example 1]
In the two-component developer of Comparative Example 1, the silica particles (S-4) having a higher ionization potential than the silica particles (S-3) contained in the toner particles were exposed when the coat layer was worn. It is determined that the positive charge that the particles impart to the toner particles has increased.

[Comparative Example 2]
In the two-component developer of Comparative Example 2, the silica particles (S-1) having an excessively low ionization potential as compared to the silica particles (S-3) contained in the toner particles were exposed when the coat layer was worn. , It is determined that toner charge-up has been excessively suppressed.

[Comparative Example 3]
In the two-component developer of Comparative Example 3, since the surface of the coat layer had elasticity (pencil hardness of 4H), it was determined that the surface of the carrier particles was not sufficiently refreshed due to wear of the coat layer. That is, in the two-component developer of Comparative Example 3, the external additive particles adhere to the carrier particles and become contaminated, so that it is determined that the charge amount of the toner is reduced.

[Comparative Example 4]
In the two-component developer of Comparative Example 4, it was determined that the first region of the coat layer was thin, and there was a portion of the coat layer where the thickness of the first region was nearly zero. As a result, in the two-component developer of Comparative Example 4, it is determined that the core was exposed when the coat layer was worn, and the charge amount of the toner was reduced. In the case of the two-component developer of Example 3 (the thickness of the first region is 320 nm), the charge amount of the toner does not decrease. Therefore, the exposure of the core is suppressed by setting the thickness of the first region to 300 nm or more. It is determined that it can be done.

[Comparative Example 5]
In the two-component developer of Comparative Example 5, since the first region of the coat layer is thick, the capacitance is unlikely to increase even if the coat layer is worn. Therefore, in the two-component developer of Comparative Example 5, when the coat layer is worn, the first silica particles are exposed although the capacitance is not so much increased, and the charge-up of the toner is excessively suppressed. It is determined that it has been done.

[Comparative Example 6]
In the two-component developer of Comparative Example 6, the second region of the coat layer is thin. Therefore, in the two-component developer of Comparative Example 6, when the coat layer is worn, the first silica particles are exposed even though the capacitance is not so much increased, and the charge-up of the toner is excessively suppressed. It is determined that it has been done.

[Comparative Example 7]
In the two-component developer of Comparative Example 7, the second region of the coat layer was too thick. Therefore, in the two-component developer of Comparative Example 7, it was determined that the charge-up of the toner could not be suppressed because the first region was difficult to be exposed even when the coat layer was worn.

[Comparative Example 8]
In the two-component developer of Comparative Example 8, the first region did not sufficiently contain the first silica particles. As a result, with the two-component developer of Comparative Example 8, when the coat layer was worn, it was determined that the effect of suppressing the charge-up of the toner due to the exposure of the first silica particles was not sufficiently obtained.

[Comparative Example 9]
In the two-component developer of Comparative Example 9, first silica particles were excessively contained in the first region. As a result, in the two-component developer of Comparative Example 9, when the coat layer was worn, it was determined that the effect of suppressing the charge-up of the toner due to the exposure of the first silica particles worked excessively.

[Comparative Example 10]
In the two-component developer of Comparative Example 10, since the silica particles (S-3) were contained in the second region of the coat layer, the strength of the second region was excessively high, and the surface of the carrier particles due to abrasion of the coat layer was reduced. It is determined that the refresh has not been performed sufficiently. That is, in the two-component developer of Comparative Example 10, it is considered that the amount of charge of the toner was reduced by the external additive particles adhering to the carrier particles.

[Comparative Example 11]
The two-component developer of Comparative Example 11 did not contain the first silica particles in the first region of the coat layer. As a result, in the two-component developer of Comparative Example 11, when the coat layer was worn, the effect of suppressing the charge-up of the toner due to the exposure of the first silica particles did not work, so it is determined that the charge amount of the toner was increased. .

  The two-component developer according to the present invention can be used for forming an image in, for example, a copying machine, a printer, or a multifunction peripheral.

DESCRIPTION OF SYMBOLS 1 Carrier particle 11 Carrier core 12 Coat layer 12a 1st area 12b 2nd area 13 Matrix 14 1st silica particle 2 Toner particle 21 Toner base particle 22 2nd silica particle

Claims (6)

A two-component developer containing a carrier and a toner,
The carrier includes carrier particles,
The carrier particles include a carrier core and a coat layer covering the surface of the carrier core,
The coat layer contains a thermosetting resin and first silica particles, and includes a radially inner first region and a radially outer second region,
99.9% by mass of the first silica particles is contained in the first region, and the remaining 0.1% by mass is contained in the second region,
A thickness of the first region is not less than 300 nm and not more than 600 nm;
A thickness of the second region is 400 nm or more and 600 nm or less;
The pencil hardness on the surface of the coat layer is 7H or more and 10H or less,
The content ratio of the first silica particles in the first region is from 1.5% by mass to 2.5% by mass,
The toner includes toner particles,
The toner particles include toner base particles and second silica particles attached to the surface of the toner base particles,
The difference in ionization potential IP _B of the second silica particles to the ionization potential IP _A first silica particles (IP _A -IP _B) is more than -0.20eV 0.00eV or less, the two-component developer. The ionization potential IP _A of the first silica particles is less than 5.20 eV 5.40 eV, 2-component developer according to claim 1.   The two-component developer according to claim 1, wherein the thermosetting resin is a melamine resin or a silicone resin.   The two-component developer according to any one of claims 1 to 3, wherein the first silica particles and the second silica particles each independently have a number average particle diameter of 10 nm or more and 150 nm or less. A method for producing a two-component developer including a carrier and a toner, comprising:
A carrier preparation step of preparing the carrier,
A toner preparation step of preparing the toner,
A mixing step of mixing the carrier and the toner,
The carrier includes carrier particles,
The carrier particles include a carrier core and a coat layer covering the surface of the carrier core,
The carrier preparation step,
A first coating layer forming step of forming a first coating layer covering the surface of the carrier core;
A second coating layer forming step of forming a second coating layer covering the surface of the first coating layer;
A heating step of heating the carrier core coated with the first coating layer and the second coating layer,
The thickness of the first coating layer after the heating step is 300 nm or more and 600 nm or less,
The first coating layer is formed by a first coating solution containing an uncured first thermosetting resin and first silica particles,
The content ratio of the first silica particles in the cured residue of the first coating solution is 1.5% by mass or more and 2.5% by mass or less,
The thickness of the second coating layer after the heating step is 400 nm or more and 600 nm or less,
The second coating layer is formed by a second coating solution containing an uncured second thermosetting resin,
The pencil hardness on the surface of the coat layer is 7H or more and 10H or less,
The toner preparation step,
Toner base particle preparation step of preparing toner base particles,
External addition step of externally adding second silica particles to the surface of the toner base particles,
The difference in ionization potential IP _B of the second silica particles to the ionization potential IP _A first silica particles (IP _A -IP _B) is less than -0.20eV 0.00eV, manufacturing of the two-component developer Method.   The method of claim 5, wherein the first thermosetting resin and the second thermosetting resin are the same as each other.

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