JP2013254123A - Toner for electrostatic charge image development - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a toner for electrostatic charge image development that suppresses excessively high glossiness and has excellent fixing separability, while ensuring low-temperature fixability.SOLUTION: A toner for electrostatic charge image development comprising toner particles prepared by using an aggregating agent comprising metal salt, the toner particle has a core-shell structure obtained by forming a shell layer containing a polyester resin and wax on a core particle comprising a styrene-acrylic copolymer resin; the wax is present only in a thickness part within 1 μm from the surface of the toner particle; and the content of metal ions derived from the aggregating agent in the toner particles is 4.0 or more and 7.0 or less in Net strength measured by fluorescent X-ray analysis.

Description

  The present invention relates to an electrostatic charge image developing toner used for image formation by electrophotography.

  In recent years, in the field of electrostatic charge image developing toner (hereinafter, also simply referred to as “toner”), an electrophotographic apparatus suitable for the demand and a toner corresponding to the electrophotographic apparatus according to the demand from the market. Development is proceeding at a rapid pace.

  For example, as a toner corresponding to high image quality, since the reproducibility of minute dots is remarkably improved by developing development behavior of individual toner particles, a toner having a sharp particle size distribution is required. For this reason, an emulsion polymerization aggregation method has been proposed as a production method capable of arbitrarily controlling the shape and particle size distribution of toner particles. In this method, a dispersion of fine particles of a binder resin, a dispersion of fine particles of a colorant or a dispersion of fine particles of wax are mixed, and while stirring, these fine particles are added by adding a flocculant, controlling the pH, etc. In this method, toner particles are obtained by agglomerating particles and further fusing the aggregated particles by heating.

  In addition, from the viewpoint of energy saving, development of a low-temperature fixing toner that can be fixed with less energy is in progress. In order to lower the fixing temperature of the toner, it is necessary to lower the melting temperature and melt viscosity of the binder resin. However, if a binder resin having a low glass transition point or a binder resin having a low molecular weight is used to lower the melting temperature or melt viscosity of the binder resin, there is a problem that the glossiness becomes too high.

As a method for reducing the glossiness, a method for increasing the residual amount of the coagulant in the toner particles is known (see Patent Document 1).
By increasing the residual amount of the flocculant in the toner particles, the crosslink density of the toner is increased and the viscosity of the toner is increased, whereby irregularities are formed on the surface of the fixed image and a low-gloss fixed image can be obtained. However, since the crosslink density of the toner is increased, there is a problem that the wax is less likely to ooze out during fixing and the fixing separation property is lowered.

JP 2010-204243 A

  The present invention has been made based on the above circumstances, and an electrostatic charge image developing toner that suppresses excessive high gloss and has excellent fixing separation property while ensuring low temperature fixability. It is to provide.

The electrostatic charge image developing toner of the present invention is an electrostatic charge image developing toner comprising toner particles prepared using an aggregating agent comprising a metal salt.
The toner particles have a core-shell structure in which a shell layer containing a polyester resin and a wax is formed on core particles made of a styrene-acrylic copolymer resin.
The wax is present only in the thickness portion within 1 μm from the toner particle surface, and the metal ion content derived from the flocculant in the toner particle is 4.0 or more and 7.0 or less in the Net intensity by fluorescent X-ray analysis. It is characterized by being.

In the toner for developing an electrostatic charge image of the present invention, the shell layer includes a first-stage shell layer formed on the core particles and a second-stage shell layer formed on the first-stage shell layer. Two-layer structure,
The wax is preferably contained in the first stage shell layer.

In the electrostatic image developing toner of the present invention, the first shell layer is made of a styrene-acrylic copolymer resin,
The second shell layer is preferably made of a polyester resin.

In the electrostatic image developing toner of the present invention, the polyester resin constituting the second-stage shell layer is a styrene-acrylic modified polyester resin in which a styrene-acrylic copolymer segment is bonded to the end of the polyester segment. ,
The content ratio of the styrene-acrylic copolymer segment in the styrene-acrylic modified polyester resin is preferably 5% by mass or more and 30% by mass or less.

  In the electrostatic image developing toner of the present invention, the shell layer preferably has a layer thickness of 0.10 to 1.00 μm.

  In the electrostatic image developing toner of the present invention, the second shell layer preferably has a layer thickness of 0.10 to 0.50 μm.

  In the electrostatic image developing toner of the present invention, the metal ion is preferably divalent.

  According to the toner of the present invention, low temperature fixability is ensured by comprising core-shell toner particles in which a shell layer containing a polyester resin is formed on core particles made of a styrene-acrylic copolymer resin. However, the wax is present only in the thickness portion within 1 μm from the surface of the toner particles, and the metal ion content in the toner particles is within a specific range, thereby suppressing excessive high gloss and excellent fixing. Separability is obtained.

FIG. 3 is an explanatory cross-sectional view schematically showing an example of toner particles constituting the toner of the present invention.

  The present invention will be described in detail below.

〔toner〕
The toner of the present invention is composed of toner particles prepared using a flocculant made of a metal salt.
In the toner of the present invention, as shown in FIG. 1, the toner particle 10 has a core-shell structure in which a shell layer 12 containing wax is formed on a core particle 11 made of a styrene-acrylic copolymer resin. . The wax 13 contained in the shell layer 12 exists only in the thickness portion within a depth of 1 μm from the surface of the toner particles 10, and the content of metal ions derived from the flocculant in the toner particles 10 is the fluorescent X-ray. The net intensity by analysis is set to 4.0 or more and 7.0 or less. With the structure as described above, the core-shell structure in which the shell layer containing the polyester resin is formed on the core particles made of the styrene-acrylic copolymer resin has a metal ion content while ensuring low temperature fixability. By being in the specific range, excessive high gloss is suppressed and the wax 13 is unevenly distributed in the vicinity of the surface of the toner particles 10, so that the wax is easily oozed out and excellent fixing separation property is obtained.

  The toner particles according to the present invention may contain an internal additive such as a colorant or a charge control agent, if necessary. An external additive may be added to the toner particles. The internal additives such as the colorant and the charge control agent may be contained in either the core particle or the shell layer, or may be contained in either the core particle or the shell layer.

[Metal ion content]
In the toner of the present invention, the content of metal ions derived from the aggregating agent in the toner particles is such that the Net intensity is 4.0 or more and 7.0 or less, more preferably 3.0 or more and 6.0 or less in the fluorescent X-ray analysis. It is said. That is, in the present invention, the content of metal ions derived from the aggregating agent in the toner particles is defined by the X-ray intensity obtained by fluorescent X-ray analysis.
When the metal ion content in the toner particles is within the above range in terms of Net intensity, excessive high gloss can be controlled in the formed image.
Here, “Net intensity” refers to the X-ray intensity obtained by subtracting the background intensity from the X-ray intensity at the peak angle indicating the presence of metal ions.
When the metal ion content in the toner particles is less than 4.0 in terms of Net strength, a low gloss image cannot be obtained. On the other hand, when the metal ion content in the toner particles exceeds 7.0 in terms of Net strength, the metal ions and the carboxyl group are pseudo-crosslinked, resulting in an increase in toner hardness and impaired low-temperature fixability.

  In the present invention, the metal ion content in the toner particles is derived from an aggregating agent made of a metal salt added during the production of the toner particles. Examples of such an aggregating agent include monovalent metal salts such as alkali metal salts such as sodium, potassium and lithium; divalent metal salts such as calcium, magnesium, manganese and copper; and three such as iron and aluminum. Valent metal salts and the like. Specific examples of the metal salt include sodium chloride, potassium chloride, lithium chloride, calcium chloride, magnesium chloride, zinc chloride, copper sulfate, magnesium sulfate, and manganese sulfate. Among these, divalent metals It is particularly preferred to use a salt.

In the present invention, the metal ion content in the toner particles is measured as follows.
It can be determined by measuring the fluorescent X-ray intensity emitted from the metal species of the metal salt used as the aggregating agent using a fluorescent ray analyzer “system 3270 type” (manufactured by Rigaku Denki Kogyo Co., Ltd.). 6 g of toner was subjected to pressure molding with a pressure molding machine at a load of 10 t and a pressing time of 1 minute as a measurement sample. The measurement conditions of the X-ray fluorescence analyzer were a tube voltage of 40 kV, a tube current of 90 mA, and a measurement time of 30. The minute is obtained from the elemental composition ratio.

[Core particles]
The core particles constituting the toner particles contain at least a core resin made of a styrene-acrylic copolymer resin, and may contain an internal additive such as a colorant and a charge control agent as necessary. The core resin may contain a resin other than the styrene-acrylic copolymer resin. Other resins are not particularly limited, and various known resins can be used, and examples thereof include styrene resins and acrylic resins such as alkyl acrylates and alkyl methacrylates. Other resin can be contained in the ratio of 1-20 mass% with respect to the core resin whole quantity.

(Core resin)
The core resin constituting the core particle is made of a styrene-acrylic copolymer resin, and the polymerizable monomer used to form the styrene-acrylic copolymer resin includes an aromatic vinyl monomer, (Meth) acrylic acid ester monomers are mentioned.
Examples of the aromatic vinyl monomer include styrene, o-methyl styrene, m-methyl styrene, p-methyl styrene, p-methoxy styrene, p-phenyl styrene, p-chloro styrene, p-ethyl styrene, p. -N-butyl styrene, p-tert-butyl styrene, pn-hexyl styrene, pn-octyl styrene, pn-nonyl styrene, pn-decyl styrene, pn-dodecyl styrene, 2, Examples include 4-dimethylstyrene, 3,4-dichlorostyrene, and derivatives thereof.
These aromatic vinyl monomers can be used alone or in combination of two or more.
Examples of (meth) acrylic acid ester monomers include methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, cyclohexyl acrylate, phenyl acrylate, methyl methacrylate, ethyl methacrylate, and methacrylic acid. Examples include butyl, hexyl methacrylate, 2-ethylhexyl methacrylate, ethyl β-hydroxyacrylate, propyl γ-aminoacrylate, stearyl methacrylate, dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate, and the like.
These (meth) acrylic acid ester monomers can be used alone or in combination of two or more.

As the polymerizable monomer used for forming the styrene-acrylic copolymer resin, acrylic acid, methacrylic acid, anhydrous, together with the above aromatic vinyl monomer and (meth) acrylate monomer Maleic acid, vinyl acetate, etc., acrylamide, methacrylamide, acrylonitrile, ethylene, propylene, butylene vinyl chloride, N-vinylpyrrolidone, butadiene, etc. can also be used.
Moreover, a polyfunctional vinyl-type monomer can also be used as a polymerizable monomer with said aromatic vinyl monomer and (meth) acrylic acid ester monomer. Examples of the polyfunctional vinyl-based monomer include diacrylates such as ethylene glycol, propylene glycol, butylene glycol, and hexylene glycol; dimethacrylates and tri- and higher alcohols such as divinylbenzene, pentaerythritol, and trimethylolpropane. And methacrylate.
The copolymerization ratio of the polyfunctional vinyl monomer to the entire polymerizable monomer related to the core resin is usually 0.001 to 5% by mass, preferably 0.003 to 2% by mass, more preferably 0.00. 01 to 1% by mass.
By using a polyfunctional vinyl monomer, a gel component insoluble in tetrahydrofuran is generated. The gel component is preferably 40% by mass or less, more preferably 20% by mass or less of the entire core resin. is there.

  The glass transition point of the core resin constituting the core particle is preferably 30 to 60 ° C, more preferably 30 to 50 ° C. Moreover, it is preferable that a softening point is 80-110 degreeC, More preferably, it is 90-100 degreeC.

In the present invention, the glass transition point of the core resin is measured as follows.
Measured using a differential scanning calorimeter “Diamond DSC” (manufactured by PerkinElmer). Specifically, 4.5 mg of a measurement sample (core resin) is precisely weighed to two digits after the decimal point and sealed in an aluminum pan. And set in the DSC-7 sample holder. For the reference, an empty aluminum pan was used, and heat-cool-heat temperature control was performed at a measurement temperature of 0 to 200 ° C., a temperature increase rate of 10 ° C./min, and a temperature decrease rate of 10 ° C./min. Analysis is performed based on the data in Heat. The glass transition point is the value of the intersection of the extension line of the baseline before the rise of the first endothermic peak and the tangent line showing the maximum inclination between the rising portion of the first endothermic peak and the peak vertex.

In the present invention, the softening point of the core resin is measured as follows.
First, in an environment of 20 ° C. ± 1 ° C. and 50% ± 5% RH, 1.1 g of a measurement sample (core resin) is placed in a petri dish and left flat for 12 hours or more. ”(Manufactured by Shimadzu Corporation) with a pressure of 3820 kg / cm ² for 30 seconds to create a cylindrical molded sample having a diameter of 1 cm, and this molded sample was then subjected to 24 ° C. ± 5 ° C., 50% ± 20% RH Of the cylindrical die under the conditions of a load tester “CFT-500D” (manufactured by Shimadzu Corporation) under the conditions of a load of 196 N (20 kgf), a starting temperature of 60 ° C., a preheating time of 300 seconds, and a heating rate of 6 ° C./min The offset method temperature T _offset measured from the hole (1 mm diameter × 1 mm) using a piston with a diameter of 1 cm from the end of preheating and measured with a melting temperature measurement method of the temperature rising method with an offset value of 5 mm is The softening point of the core resin.

The weight average molecular weight (Mw) of the core resin constituting the core particles is preferably 5,000 to 30,000.
When the weight average molecular weight of the core resin is in the above range, low-temperature fixability and excessive high gloss can be suppressed.

In the present invention, the weight average molecular weight of the core resin is measured as follows.
Measured by gel permeation chromatography (GPC), specifically, using an apparatus “HLC-8220” (manufactured by Tosoh Corporation) and a column “TSKguardcolumn + TSKgelSuperHZM-M3 series” (manufactured by Tosoh Corporation), the column temperature at 40 ° C. While being held, tetrahydrofuran (THF) as a carrier solvent is flowed at a flow rate of 0.2 mL / min, and the measurement sample (core resin) is treated at room temperature for 5 minutes using an ultrasonic disperser to a concentration of 1 mg / mL. Then, the sample solution was obtained by processing with a membrane filter having a pore size of 0.2 μm, and 10 μL of this sample solution was injected into the apparatus together with the above carrier solvent, and a refractive index detector (RI detector) ) To detect the molecular weight distribution of the sample It is calculated using a calibration curve measured using a standard particle of titanium. Ten polystyrenes are used for calibration curve measurement.

(Coloring agent)
When the core particles contain a colorant, as the colorant, for example, carbon black, a magnetic material, a dye, other pigments, and the like can be arbitrarily used.
As the carbon black, channel black, furnace black, acetylene black, thermal black, lamp black and the like can be used.
As the magnetic material, ferromagnetic metals such as iron, nickel and cobalt, alloys containing these metals, and compounds of ferromagnetic metals such as ferrite and magnetite can be used.
As the pigment, C.I. I. Pigment Red 2, 3, 5, 7, 15, 16, 48: 1, 48: 3, 53: 1, 57: 1, 81: 4, 122, 123, 139, 144, 149, 166, 177, 178, 208, 209, 222, C.I. I. Pigment Orange 31 and 43, C.I. I. Pigment Yellow 3, 9, 14, 17, 35, 36, 65, 74, 83, 93, 94, 98, 110, 111, 138, 139, 153, 155, 180, 181, 185, C.I. I. Pigment green 7, C.I. I. Pigment Blue 15: 3, 15: 4, 60, and phthalocyanine pigments whose central metal is zinc, titanium, magnesium, or the like can be used, and a mixture thereof can also be used. As the dye, C.I. I. Solvent Red 1, 3, 14, 17, 17, 22, 22, 49, 51, 52, 58, 63, 87, 111, 122, 127, 128, 131, 145, 146, 149, 150, 151, 152, 153, 154, 155, 156, 157, 158, 176, 179, pyrazolotriazole Azo dyes, pyrazolotriazole azomethine dyes, pyrazolone azo dyes, pyrazolone azomethine dyes, C.I. I. Solvent Yellow 19, 44, 77, 79, 81, 82, 93, 98, 103, 104, 112, 162, C.I. I. Solvent Blue 25, 36, 60, 70, 93, 95, etc. can be used, and mixtures thereof can also be used.

  The content ratio of the colorant is preferably 1 to 30% by mass, more preferably 2 to 20% by mass with respect to the total amount of the resin constituting the toner particles.

(Charge control agent)
When the core particles contain a charge control agent, various known charge control agents can be used.
As the charge control agent, various known compounds that can be dispersed in an aqueous medium can be used. Specifically, nigrosine dyes, metal salts of naphthenic acid or higher fatty acids, alkoxylated amines, fourth compounds. Examples include quaternary ammonium salt compounds, azo metal complexes, salicylic acid metal salts or metal complexes thereof.

  The content ratio of the charge control agent is preferably 0.1 to 10% by mass, more preferably 0.5 to 5% by mass with respect to the total amount of the resin constituting the toner particles.

The average particle diameter of the core particles is preferably in the range of 4.7 to 7.0 μm, for example, in terms of volume-based median diameter.
In the present invention, the average particle diameter of the core particles is measured using “Coulter Multisizer 3” (manufactured by Coulter Beckman).

[Shell layer]
The shell layer constituting the toner particles contains a polyester resin and a wax, and the shell layer is configured such that fine particles of the wax are dispersed in a shell resin containing at least the polyester resin. The shell layer may contain internal additives such as the above-described colorants and charge control agents as necessary.
As shown in FIG. 1, the shell layer has a two-layer configuration of a first-stage shell layer 12a formed on the core particle 11 and a second-stage shell layer 12b formed on the first-stage shell layer 12a. Are preferred. When the shell layer 12 has a two-layer structure, the wax 13 is preferably contained in the first-stage shell layer 12a. With such a configuration, the wax 13 is prevented from being exposed on the surface of the toner particles 10, and heat resistant storage properties are improved.
The shell layer 12 is preferably configured to cover the surface of the core particle 11 with a uniform thickness, but may be configured such that a part of the surface of the core particle 11 is exposed.

The layer thickness of the shell layer 12 is preferably 0.10 to 1.00 μm, more preferably 0.20 to 0.90 μm.
When the layer thickness of the shell layer 12 is too small, sufficient heat-resistant storage property cannot be obtained. On the other hand, when the layer thickness of the shell layer 12 is excessive, sufficient fixing and separating properties cannot be obtained.

  In the case where the shell layer 12 has a two-layer configuration, the layer thickness of the first-stage shell layer 12a is preferably 0.10 to 1.00 μm, more preferably 0.50 to 0.90 μm. The layer thickness of the second shell layer 12b is preferably 0.10 to 0.50 μm, more preferably 0.10 to 0.40 μm.

In the present invention, the thickness of the shell layer is measured as follows.
The toner particles are embedded in an epoxy resin, cured at 60 ° C. for 24 hours, and then a flat surface is cut out using a microtome equipped with diamond teeth to smooth the cross section. Using a microscope “JEM-2010F” (manufactured by JEOL Ltd.), 100 randomly selected fields of view are observed by 1000 times STEM measurement. At least 10 toner particles are observed.

(Shell resin)
The shell resin constituting the shell layer contains at least a polyester resin, and other resins such as a styrene-acrylic copolymer resin may be contained together with the polyester resin.

  When the shell layer has a two-layer structure, it is preferable that the first-stage shell layer is made of a styrene-acrylic copolymer resin and the second-stage shell layer is made of a polyester resin. When the first-stage shell layer is a styrene-acrylic copolymer resin, when the shell layer contains a colorant, the dispersibility of the colorant is excellent, and as a result, high coloring power is obtained with a small amount of colorant. Further, since the second shell layer is a polyester resin, low temperature fixability can be obtained due to the characteristics of the polyester resin.

When the shell layer has a two-layer structure, the content ratio of the first shell resin constituting the first-stage shell layer is preferably 15 to 25% by mass with respect to the total amount of the resin constituting the toner particles, More preferably, it is 15-23 mass%. When the content ratio of the first shell resin is too small, the fixing separation property is deteriorated. On the other hand, when the content ratio of the first shell resin is excessive, sufficient low-temperature fixability cannot be obtained.
Further, the content ratio of the second shell resin constituting the second-stage shell layer is preferably 5 to 15% by mass, more preferably 5 to 10% by mass with respect to the total amount of the resin constituting the toner particles. . When the content ratio of the second shell resin is too small, there is a possibility that sufficient low-temperature fixability cannot be obtained. On the other hand, when the content ratio of the second shell resin is excessive, there is a possibility that the fixing separation property is deteriorated.

  As the styrene-acrylic copolymer resin, the same styrene-acrylic copolymer resin as the core particles described above can be used.

The polyester resin is obtained from a known polyhydric alcohol component and a known polyvalent carboxylic acid component.
Examples of the polyhydric alcohol component include 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, and 1,7-heptanediol. , 1,8-octanediol, neopentyl glycol, 1,4-butenediol and other aliphatic diols; aromatic diols such as alkylene oxide adducts of bisphenol A; 3 such as glycerin, pentaerythritol, trimethylolpropane and sorbitol Examples thereof include polyhydric alcohols having a valence higher than that. These polyhydric alcohol components can be used alone or in combination of two or more. Further, examples of the unsaturated alcohol include alkene diols, specifically, 2-butyne-1,4 diol, 3-butyne-1,4 diol, 9-octadezene-7,12 diol, and the like.
Examples of the polyvalent carboxylic acid component include aliphatic carboxylic acids such as succinic acid, adipic acid, sebacic acid, maleic acid, and fumaric acid; aromatic carboxylic acids such as phthalic acid, isophthalic acid, terephthalic acid, and naphthalenedicarboxylic acid. Is given. Examples of the trivalent carboxylic acid include trimet acid.

(Styrene-acrylic modified polyester resin)
In the present invention, in the case where the shell layer has a two-layer structure and the second-stage shell layer is made of a polyester resin, the polyester resin is a styrene obtained by bonding a styrene-acrylic copolymer segment to the end of the polyester segment. -It is preferably an acrylic-modified polyester resin.
When the polyester resin constituting the second shell layer is a styrene-acrylic modified polyester resin, a second shell layer having a uniform thickness can be formed on the surface of the first shell layer.

When the polyester resin constituting the second shell layer is a styrene-acrylic modified polyester resin, the content ratio of the styrene-acrylic copolymer segment (hereinafter also referred to as “styrene-acrylic modified amount”) is 5 mass%. The content is preferably 30% by mass or less and more preferably 5% by mass or more and 25% by mass or less.
When the amount of styrene-acrylic modification in the styrene-acrylic modified polyester resin is in the above range, the affinity with the styrene-acrylic copolymer resin constituting the first-stage shell layer is appropriately controlled, and a thin layer is obtained. However, it is possible to form a smooth second stage shell layer with a more uniform film thickness. On the other hand, when the amount of styrene-acryl modification is too small, the second-stage shell layer having a uniform film thickness cannot be formed, and the first-stage shell layer is partially exposed, resulting in sufficient heat resistance. Storage is not possible. If the amount of styrene-acrylic modification is excessive, the styrene-acrylic modified polyester resin has a high softening point, so that sufficient low-temperature fixability cannot be obtained for the entire toner particles.

  Here, the amount of styrene-acrylic modification in the styrene-acrylic modified polyester resin is specifically the total mass of the material used for synthesizing the styrene-acrylic modified polyester resin, that is, the polyvalent carboxylic acid that becomes the polyester segment. A monomer and / or a polyhydric alcohol monomer, an aromatic vinyl monomer and a (meth) acrylic acid ester monomer to be a styrene-acrylic copolymer segment, and a bireactive monomer for bonding them. The ratio of the mass of the aromatic vinyl monomer and the (meth) acrylic acid ester monomer relative to the total mass.

In the toner of the present invention, an aliphatic unsaturated dicarboxylic acid is used as the polyvalent carboxylic acid monomer to form the polyester segment of the styrene-acryl-modified polyester resin, and the polyester segment is derived from the aliphatic unsaturated dicarboxylic acid. These structural units are preferably contained.
The aliphatic unsaturated dicarboxylic acid refers to a chain dicarboxylic acid having a vinylene group in the molecule.
According to the styrene-acryl-modified amide bond-containing resin having a structural unit derived from an aliphatic unsaturated dicarboxylic acid, it is possible to reliably form a smooth second stage shell layer with a more uniform film thickness while being a thin layer. Can do.

(Method for producing styrene-acrylic modified polyester resin)
As a method for producing the styrene-acrylic modified polyester resin, an existing general scheme can be used. Typical methods include the following three methods.
(A-1) A polyester segment is polymerized in advance, the polyester segment is reacted with both reactive monomers, and an aromatic vinyl monomer and a (meta) are formed to form a styrene-acrylic copolymer segment. ) A method of reacting an acrylate monomer.
(A-2) A polyvalent carboxylic acid monomer for polymerizing a styrene-acrylic copolymer segment in advance, reacting the styrene-acrylic copolymer segment with both reactive monomers, and further forming a polyester segment And a method of reacting a polyhydric alcohol monomer.
(B) A method in which a polyester segment and a styrene-acrylic copolymer segment are respectively polymerized in advance, and both are reacted with each other to react them.

The method (A-1) will be specifically described.
(1) A mixing step of mixing an unmodified polyester resin, which becomes a polyester segment, an aromatic vinyl monomer and a (meth) acrylic acid ester monomer, and both reactive monomers,
(2) By passing through a polymerization step of polymerizing an aromatic vinyl monomer and a (meth) acrylic acid ester monomer, a styrene-acrylic copolymer segment can be formed at the end of the polyester segment.

  In the mixing step (1), it is preferable to heat. The heating temperature may be within a range where unmodified polyester resin, aromatic vinyl monomer, (meth) acrylic acid ester monomer and both reactive monomers can be mixed. Since it is obtained and polymerization control becomes easy, it can be set to, for example, 80 to 120 ° C., more preferably 85 to 115 ° C., and further preferably 90 to 110 ° C.

  Among unmodified polyester resin, aromatic vinyl monomer, (meth) acrylic acid ester monomer and both reactive monomers, aromatic vinyl monomer and (meth) acrylic acid ester monomer The total proportion of the resin material used, that is, the total amount of the aromatic vinyl monomer and the (meth) acrylic acid ester monomer when the total mass of the four members is 100% by mass. The ratio is 5% by mass or more and 30% by mass or less, and particularly preferably 5% by mass or more and 20% by mass or less.

  When the total ratio of the aromatic vinyl monomer and the (meth) acrylic acid ester monomer to the total mass of the resin material used is within the above range, the styrene-acrylic modified polyester resin and the first-stage shell The affinity with the styrene-acrylic copolymer resin constituting the layer is appropriately controlled, and a smooth second stage shell layer can be formed with a more uniform film thickness while being a thin layer. On the other hand, when the ratio is too small, the resulting styrene-acrylic modified polyester resin cannot form a second-stage shell layer having a uniform film thickness, and the first-stage shell layer is partially formed. As a result, the toner obtained does not have sufficient heat-resistant storage stability. If the ratio is excessive, the resulting styrene-acryl-modified polyester resin has a high softening point, so that the resulting toner cannot obtain sufficient low-temperature fixability as a whole.

The relative proportion of the aromatic vinyl monomer and the (meth) acrylic acid ester monomer is such that the glass transition point (Tg) calculated by the FOX formula represented by the following formula (A) is 35. It is preferable that the ratio is in the range of -80 ° C, preferably 40-60 ° C.
Formula (A): 1 / Tg = Σ (Wx / Tgx)
[In Formula (A), Wx is the weight fraction of monomer x, and Tgx is the glass transition point of the homopolymer of monomer x. ]
In the present specification, both reactive monomers are not used for calculation of the glass transition point.

  Among unmodified polyester resin, aromatic vinyl monomer, (meth) acrylic acid ester monomer, and both reactive monomers, the proportion of both reactive monomers used is the total mass of the resin material used, that is, The ratio of the two reactive monomers when the total mass of the four components is 100% by mass is 0.1% by mass or more and 5.0% by mass or less, and particularly 0.5% by mass or more and 3.0% by mass. The following is preferable.

(Aromatic vinyl monomers and (meth) acrylic acid ester monomers)
The aromatic vinyl monomer and (meth) acrylic acid ester monomer for forming the styrene-acrylic copolymer segment have an ethylenically unsaturated bond capable of radical polymerization.
Examples of the aromatic vinyl monomer include styrene, o-methyl styrene, m-methyl styrene, p-methyl styrene, p-methoxy styrene, p-phenyl styrene, p-chloro styrene, p-ethyl styrene, p. -N-butyl styrene, p-tert-butyl styrene, pn-hexyl styrene, pn-octyl styrene, pn-nonyl styrene, pn-decyl styrene, pn-dodecyl styrene, 2, Examples include 4-dimethylstyrene, 3,4-dichlorostyrene, and derivatives thereof.
These aromatic vinyl monomers can be used alone or in combination of two or more.
Examples of (meth) acrylic acid ester monomers include methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, cyclohexyl acrylate, phenyl acrylate, methyl methacrylate, ethyl methacrylate, and methacrylic acid. Examples include butyl, hexyl methacrylate, 2-ethylhexyl methacrylate, ethyl β-hydroxyacrylate, propyl γ-aminoacrylate, stearyl methacrylate, dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate, and the like.
These (meth) acrylic acid ester monomers can be used alone or in combination of two or more.

  As an aromatic vinyl monomer and (meth) acrylic acid ester monomer for forming a styrene-acrylic copolymer segment, styrene or a derivative thereof is used from the viewpoint of obtaining excellent chargeability and image quality characteristics. It is preferable to use a large amount. Specifically, the amount of styrene or a derivative thereof used is the total amount of monomers (aromatic vinyl monomer and (meth) acrylic acid ester single monomer used to form a styrene-acrylic copolymer segment). It is preferable that it is 50 mass% or more in the body.

(Amotropic monomer)
Examples of the both reactive monomers for forming the styrene-acrylic copolymer segment include a group capable of reacting with the polyvalent carboxylic acid monomer and / or the polyhydric alcohol monomer for forming the polyester segment, and a polymerizable unsaturated group. Specifically, for example, acrylic acid, methacrylic acid, fumaric acid, maleic acid, maleic anhydride, and the like can be used.

(Unmodified polyester resin)
The unmodified polyester resin used for preparing the styrene-acrylic modified polyester resin is produced by polycondensation reaction in the presence of an appropriate catalyst using the above-described polyhydric alcohol component and polyhydric carboxylic acid component as raw materials. Can do.

  As the polyvalent carboxylic acid component, it is preferable to use an aliphatic unsaturated dicarboxylic acid such as fumaric acid, maleic acid or mesaconic acid, and in particular, an aliphatic unsaturated dicarboxylic acid represented by the following general formula (A) is used. It is preferable.

General formula (A): HOOC- (CR < ¹ > = CR _< ² _> ) _n- COOH
[Wherein, R ¹ and R ² are a hydrogen atom, a methyl group or an ethyl group, and may be the same or different from each other. n is an integer of 1 or 2. ]
By using the aliphatic unsaturated dicarboxylic acid, the obtained styrene-acryl-modified polyester resin can surely form a smooth second stage shell layer with a more uniform film thickness while being a thin layer. It will be a thing. In particular, by using the aliphatic unsaturated dicarboxylic acid represented by the general formula (A), the obtained styrene-acryl-modified polyester resin is more surely a thin layer with a more uniform film thickness and A smooth second-stage shell layer can be formed.

The proportion of the aliphatic unsaturated dicarboxylic acid in all the polyvalent carboxylic acid components to be used is preferably 25 mol% or more and 75 mol% or less, and more preferably 30 mol% or more and 60 mol% or less.
When the ratio of the aliphatic unsaturated dicarboxylic acid to be used is in the above range, the obtained styrene-acryl-modified polyester resin is more surely a thin film with a more uniform film thickness and a smooth second. A stepped shell layer can be formed. On the other hand, if the proportion of the aliphatic unsaturated dicarboxylic acid used is too small, sufficient heat-resistant storage stability and chargeability may not be obtained in the obtained toner, and the proportion of the aliphatic unsaturated dicarboxylic acid used is If it is excessive, sufficient chargeability may not be obtained for the obtained toner.

  The ratio of the polyhydric carboxylic acid component to the polyhydric alcohol component is preferably an equivalent ratio [OH] / [COOH] of the hydroxyl group [OH] of the polyhydric alcohol component and the carboxyl group [COOH] of the polyhydric carboxylic acid component. The ratio is 1.5 / 1 to 1 / 1.5, more preferably 1.2 / 1 to 1 / 1.2.

  Various conventionally known catalysts can be used as a catalyst for synthesizing the unmodified polyester resin.

  The unmodified polyester resin for obtaining the styrene-acrylic modified polyester resin preferably has a glass transition point of 40 ° C. or higher and 70 ° C. or lower, more preferably 50 ° C. or higher and 65 ° C. or lower. When the glass transition point of the unmodified polyester resin is 40 ° C. or higher, the cohesive force in the high temperature region becomes appropriate for the polyester resin, and the occurrence of hot offset phenomenon during fixing is suppressed. Further, since the glass transition point of the unmodified polyester resin is 70 ° C. or less, sufficient melting can be obtained at the time of fixing, and a sufficient minimum fixing temperature can be ensured.

The unmodified polyester resin preferably has a weight average molecular weight (Mw) of 1,500 to 60,000, more preferably 3,000 to 40,000.
When the weight average molecular weight is 1,500 or more, a cohesive force suitable for the entire resin is obtained, and the occurrence of a hot offset phenomenon during fixing is suppressed. Further, when the weight average molecular weight is 60,000 or less, it is possible to obtain a sufficient melting and secure a minimum fixing temperature, while suppressing occurrence of a hot offset phenomenon during fixing. The

  The unmodified polyester resin has a partially branched structure or a crosslinked structure formed by selecting a carboxylic acid valence or an alcohol valence as a polyvalent carboxylic acid monomer and / or a polyhydric alcohol monomer to be used. May be.

(Polymerization initiator)
In the polymerization of the styrene-acrylic copolymer segment, the polymerization is preferably performed in the presence of a radical polymerization initiator, and the timing of addition of the radical polymerization initiator is not particularly limited, but it is easy to control radical polymerization. It is preferable to add after mixing the aromatic vinyl monomer and (meth) acrylic acid ester monomer for forming the polymerization of the styrene-acrylic copolymer segment.

  Various known polymerization initiators are preferably used as the polymerization initiator. Specifically, for example, hydrogen peroxide, acetyl peroxide, cumyl peroxide, tert-butyl peroxide, propionyl peroxide, benzoyl peroxide, chlorobenzoyl peroxide, dichlorobenzoyl peroxide, bromomethylbenzoyl peroxide, Lauroyl oxide, ammonium persulfate, sodium persulfate, potassium persulfate, diisopropyl peroxycarbonate, tetralin hydroperoxide, 1-phenyl-2-methylpropyl-1-hydroperoxide, pertriphenylacetic acid-tert-butyl hydroperoxide, performic acid- tert-butyl, peracetic acid-tert-butyl, perbenzoic acid-tert-butyl, perphenylacetic acid-tert-butyl, permethoxyacetic acid-tert-butyl, per-N- (3-toluyl) palmitic acid-tert-butyl, etc. Peroxide 2,2'-azobis (2-aminodipropane) hydrochloride, 2,2'-azobis- (2-aminodipropane) nitrate, 1,1'-azobis (1-methylbutyronitrile-3-sulfone) Acid salt), 4,4'-azobis-4-cyanovaleric acid, poly (tetraethylene glycol-2,2'-azobisisobutyrate) and other azo compounds.

(Chain transfer agent)
In the polymerization of the styrene-acrylic copolymer segment, a generally used chain transfer agent can be used for the purpose of adjusting the molecular weight of the styrene-acrylic copolymer segment. The chain transfer agent is not particularly limited, and examples thereof include alkyl mercaptans and mercapto fatty acid esters.
The chain transfer agent is mixed with the resin material in the mixing step of the aromatic vinyl monomer and the (meth) acrylic acid ester monomer to form the polymerization of the styrene-acrylic copolymer segment. Is preferred.

  The addition amount of the chain transfer agent varies depending on the molecular weight and molecular weight distribution of the desired styrene-acrylic copolymer segment. Specifically, the aromatic vinyl monomer and the (meth) acrylate monomer, and It is preferable to add in the range of 0.1-5 mass% with respect to the total amount of both reactive monomers.

  The polymerization temperature in the polymerization of the styrene-acrylic copolymer segment is not particularly limited. Polymerization between an aromatic vinyl monomer and a (meth) acrylic acid ester monomer and bonding to an unmodified polyester resin Can be appropriately selected within the range in which. For example, the polymerization temperature is preferably 85 ° C. or higher and 125 ° C. or lower, more preferably 90 ° C. or higher and 120 ° C. or lower, and further preferably 95 ° C. or higher and 115 ° C. or lower.

  In the production of a styrene-acrylic modified polyester resin, it is practically preferable that the volatile organic substances from the emulsion such as the amount of residual monomer after polymerization are suppressed to 1,000 ppm or less, more preferably 500 ppm or less, and still more preferably. Is 200 ppm or less.

  It is preferable that the glass transition point of the shell resin which comprises a shell layer is 50-70 degreeC, More preferably, it is 50-65 degreeC. Moreover, it is preferable that a softening point is 80-110 degreeC, More preferably, it is 90-100 degreeC.

In the present invention, the glass transition point of the shell resin is measured as follows.
Measured using a differential scanning calorimeter “Diamond DSC” (manufactured by PerkinElmer). Specifically, 4.5 mg of a measurement sample (shell resin) is precisely weighed to two digits after the decimal point and sealed in an aluminum pan. And set in the DSC-7 sample holder. For the reference, an empty aluminum pan was used, and heat-cool-heat temperature control was performed at a measurement temperature of 0 to 200 ° C., a temperature increase rate of 10 ° C./min, and a temperature decrease rate of 10 ° C./min. Analysis is performed based on the data in Heat. The glass transition point is the value of the intersection of the baseline extension before the first endothermic peak rises and the tangent line that shows the maximum slope between the first endothermic peak rising portion and the peak apex.

In the present invention, the softening point of the shell resin is measured as follows.
First, in an environment of 20 ° C. ± 1 ° C. and 50% ± 5% RH, 1.1 g of a measurement sample (shell resin) is placed in a petri dish and left flat for 12 hours or more. ”(Manufactured by Shimadzu Corporation) with a pressure of 3820 kg / cm ² for 30 seconds to create a cylindrical molded sample having a diameter of 1 cm, and this molded sample was then subjected to 24 ° C. ± 5 ° C., 50% ± 20% RH Of the cylindrical die under the conditions of a load tester “CFT-500D” (manufactured by Shimadzu Corporation) under the conditions of a load of 196 N (20 kgf), a starting temperature of 60 ° C., a preheating time of 300 seconds, and a heating rate of 6 ° C./min Offset method temperature T _offset measured from a hole (1 mm diameter x 1 mm) using a piston with a diameter of 1 cm from the end of preheating and measured with a melting temperature measurement method of the temperature rising method with an offset value of 5 mm Is the softening point of the shell resin.

The weight average molecular weight (Mw) of the shell resin constituting the shell layer is preferably 2,000 to 3,000.
When the weight average molecular weight of the shell resin is in the above range, both heat resistant storage stability and low temperature fixability can be achieved.

In the present invention, the weight average molecular weight of the shell resin is measured as follows.
Measured by gel permeation chromatography (GPC), specifically, using an apparatus “HLC-8220” (manufactured by Tosoh Corporation) and a column “TSKguardcolumn + TSKgelSuperHZM-M3 series” (manufactured by Tosoh Corporation), the column temperature at 40 ° C. While being held, tetrahydrofuran (THF) as a carrier solvent is flowed at a flow rate of 0.2 mL / min, and the measurement sample (shell resin) is treated at room temperature for 5 minutes using an ultrasonic disperser to a concentration of 1 mg / mL. Then, the sample solution was obtained by processing with a membrane filter having a pore size of 0.2 μm, and 10 μL of this sample solution was injected into the apparatus together with the above carrier solvent, and a refractive index detector (RI detector) ) To detect the molecular weight distribution of the sample It is calculated using a calibration curve measured using styrene standard particles. Ten polystyrenes are used for calibration curve measurement.

(wax)
The shell layer contains a wax, and the wax exists only in a thickness portion within 1 μm from the toner particle surface. That is, as shown in FIG. 1, the wax 13 is contained in a state of being unevenly distributed near the surface of the toner particle 10.
Since the wax exists only in the thickness portion within 1 μm from the surface of the toner particles, even if the metal ion content in the toner particles is large, it is possible to avoid the inhibition of the seepage of the wax due to the high crosslinking density of the toner. .

  Examples of the wax contained in the shell layer include hydrocarbon waxes such as low molecular weight polyethylene wax, low molecular weight polypropylene wax, Fischer-Tropsch wax, microcrystalline wax, and paraffin wax, carnauba wax, pentaerythritol behenate. And ester waxes such as behenyl behenate and behenyl citrate. These can be used individually by 1 type or in combination of 2 or more types.

In the present invention, the position of the wax can be confirmed as follows.
The toner particles are embedded in an epoxy resin, cured at 60 ° C. for 24 hours, and then a flat surface is cut out using a microtome equipped with diamond teeth to smooth the cross section. Using a microscope “JEM-2010F” (manufactured by JEOL Ltd.), 100 randomly selected fields of view are observed by 1000 times STEM measurement. At least 10 toner particles are observed.

The wax fine particles constituting the wax are preferably dispersed with an average particle size in the shell layer of 100 to 300 nm.
In the present invention, the average particle size of the wax fine particles is measured as follows.
The toner particles are embedded in an epoxy resin, cured at 60 ° C. for 24 hours, and then a flat surface is cut out using a microtome equipped with diamond teeth to smooth the cross section. Using a microscope “JEM-2010F” (manufactured by JEOL Ltd.), 100 fields randomly selected by STEM measurement at 10,000 times are observed. At least 10 toner particles are observed.

  As the wax, it is preferable to use a wax having a melting point of 50 to 95 ° C. from the viewpoint of reliably obtaining low-temperature fixability and releasability of the toner.

  The content of the wax is preferably 2 to 20% by mass, more preferably 3 to 18% by mass, and further preferably 4 to 15% by mass with respect to the total amount of the resin constituting the toner particles.

[Toner Production Method]
The toner of the present invention can be produced by various known methods. However, since the shell layer can be uniformly formed on the surface of the core particles, the core resin fine particles and the colorant fine particles dispersed in the aqueous medium are used. Is formed by agglomeration and fusing using a flocculant to form core particles, and a shell resin fine particle and a wax fine particle are agglomerated and fused on the surface of the core particle to obtain toner particles. It is preferable to manufacture.

Specific examples of the production of the toner of the present invention by the emulsion polymerization aggregation method are shown below.
(1-1) A dispersion liquid in which first shell resin fine particles are formed by polymerization in a water-based medium by polymerizing first shell resin constituting the first-stage shell layer and wax, and the first shell resin fine particles are dispersed. A first shell resin polymerization step to be prepared;
(1-2) Second shell for preparing a dispersion in which the second shell resin fine particles are formed by the second shell resin constituting the second shell layer in the aqueous medium, and the second shell resin fine particles are dispersed. Resin fine particle dispersion preparation process,
(1-3) Core resin polymerization step in which a core resin fine particle is formed by polymerization in an aqueous medium to prepare a dispersion liquid in which the core resin fine particles are dispersed;
(1-4) Colorant fine particle dispersion preparation step of preparing a dispersion in which colorant fine particles by a colorant are dispersed in an aqueous medium.
(2) a core particle forming step of aggregating the core resin fine particles and the colorant fine particles in an aqueous medium to form core particles;
(3-1) The first shell resin fine particles are added to the aqueous medium in which the core particles are dispersed, and the shell resin fine particles are aggregated and fused on the surface of the core particles to form the first-stage shell layer. First shelling step,
(3-2) The second shell resin fine particles are added to the aqueous medium in which the core particles on which the first-stage shell layer is formed are dispersed, and the second shell resin fine particles are aggregated on the surface of the first-stage shell layer. A second shelling step for forming a second shell layer by fusing,
(4) An aging step of adjusting the shape of the toner particles by aging with heat energy;
(5) a cleaning step of separating the toner particles from the toner particle dispersion (aqueous medium) and removing the surfactant from the toner particles;
(6) a drying step of drying the washed toner particles;
Consisting of, if necessary,
(7) An external additive addition step of adding an external additive to the dried toner particles may be performed.

In the present invention, the “aqueous medium” refers to a medium comprising 50 to 100% by mass of water and 0 to 50% by mass of a water-soluble organic solvent. Examples of the water-soluble organic solvent include methanol, ethanol, isopropanol, butanol, acetone, methyl ethyl ketone, and tetrahydrofuran, and alcohol-based organic solvents that do not dissolve the resulting resin are preferable.
Can be added.

(1-1) First Shell Resin Polymerization Step In the first shell resin polymerization step, first shell resin fine particles are formed and used for the first shell forming step.
Specifically, in order to form the first shell resin in the aqueous medium containing the surfactant having the critical micelle concentration (CMC) or less, the resin fine particles related to the first shell resin constituting the first stage shell layer. A monomer solution in which wax and other toner constituents such as a charge control agent are dissolved or dispersed is added to the polymerizable monomer, and mechanical energy is applied to form droplets. Next, a water-soluble radical polymerization initiator is added to cause the polymerization reaction to proceed in the droplets. Note that an oil-soluble polymerization initiator may be contained in the droplet. In such a first shell resin polymerization step, mechanical energy is imparted and forcedly emulsified (droplet formation) treatment is essential. Examples of the means for applying mechanical energy include means for applying strong stirring or ultrasonic vibration energy such as homomixer, ultrasonic wave, and manton gorin.

  The first shell resin fine particles formed in the first shell resin polymerization step may have a structure of two or more layers made of resins having different compositions. In this case, an emulsion polymerization treatment (first It is possible to employ a method in which a polymerization initiator and a polymerizable monomer are added to a dispersion of the first resin particles prepared by (stage polymerization), and this system is polymerized (second stage polymerization).

The average particle diameter of the first shell resin fine particles obtained in the first shell resin polymerization step is preferably in the range of, for example, 100 to 300 nm as a volume-based median diameter.
The volume-based median diameter of the first shell resin fine particles is measured using “UPA-150” (manufactured by Microtrack).

  In the present invention, the wax can be introduced into the shell layer by preparing a dispersion of wax fine particles consisting of only the wax, and aggregating the fine particles together with the first shell resin fine particles in the first shelling step. As described above, in the first shell resin polymerization step, it is preferable to dissolve or disperse in advance in the monomer solution for forming the first shell resin from the viewpoint of wax incorporation into the toner particles.

(Surfactant)
As the surfactant used in the first shell resin polymerization step, for example, known surfactants such as various cationic surfactants, anionic surfactants, and nonionic surfactants can be used.
Specific examples of the cationic surfactant include dodecyl ammonium bromide, dodecyl trimethyl ammonium bromide, dodecyl pyridinium chloride, dodecyl pyridinium bromide, hexadecyl trimethyl anonium bromide and the like.
Specific examples of nonionic surfactants include dodecyl polyoxyethylene ether, hexadecyl polyoxyethylene ether, norylphenyl polyoxyethylene ether, lauryl polyoxyethylene ether, sorbitan monooleate polyoxyethylene ether, styrylphenyl poly Examples thereof include oxyethylene ether and monodecanoyl sucrose.
Specific examples of the anionic surfactant include aliphatic soaps such as sodium stearate and sodium laurate, sodium lauryl sulfate, sodium dodecylbenzenesulfonate, polyoxyethylene (2) sodium lauryl ether sulfate and the like. it can.
The above surfactants can be used singly or in combination of two or more as desired.

(Polymerization initiator)
In the first shell resin polymerization step, the polymerization is preferably performed in the presence of a radical polymerization initiator. Various known polymerization initiators are preferably used as the polymerization initiator. Specifically, for example, hydrogen peroxide, acetyl peroxide, cumyl peroxide, tert-butyl peroxide, propionyl peroxide, benzoyl peroxide, chlorobenzoyl peroxide, dichlorobenzoyl peroxide, bromomethylbenzoyl peroxide, Lauroyl oxide, ammonium persulfate, sodium persulfate, potassium persulfate, diisopropyl peroxycarbonate, tetralin hydroperoxide, 1-phenyl-2-methylpropyl-1-hydroperoxide, pertriphenylacetic acid-tert-hydroperoxide, performic acid-tert -Butyl, peracetic acid-tert-butyl, perbenzoic acid-tert-butyl, perphenylacetic acid-tert-butyl, permethoxyacetic acid-tert-butyl, per-N- (3-toluyl) palmitic acid-tert-butyl, etc. Peroxides; 2 2'-azobis (2-aminodipropane) hydrochloride, 2,2'-azobis- (2-aminodipropane) nitrate, 1,1'-azobis (1-methylbutyronitrile-3-sulfonic acid sodium salt) 4, 4'-azobis-4-cyanovaleric acid, poly (tetraethylene glycol-2,2'-azobisisobutyrate) and other azo compounds.

(Chain transfer agent)
In the first shell resin polymerization step, a commonly used chain transfer agent can be used for the purpose of adjusting the molecular weight of the first shell resin. The chain transfer agent is not particularly limited, and examples thereof include alkyl mercaptans and mercapto fatty acid esters.

(1-2) Second Shell Resin Fine Particle Dispersion Preparation Step In this second shell resin fine particle dispersion preparation step, the second shell resin fine particle dispersion is prepared by using, for example, an ultrasonic dispersion method or a bead mill dispersion method. It can be obtained by an aqueous direct dispersion method to which an activator is added.

The average particle diameter of the second shell resin fine particles obtained in the second shell resin fine particle dispersion preparing step is preferably in the range of, for example, 50 to 500 nm in terms of volume-based median diameter.
The volume-based median diameter of the second shell resin fine particles is measured using “UPA-150” (manufactured by Microtrack).

  When the surfactant is used in the second shell resin fine particle dispersion preparation step, the same surfactants that can be used in the first shell resin polymerization step described above can be used.

(1-3) Core resin polymerization process In this core resin polymerization process, core resin microparticles are formed and used for the core particle formation process.
Specifically, the resin fine particles related to the core resin are used as a polymerizable monomer for forming the core resin in an aqueous medium containing a surfactant having a critical micelle concentration (CMC) or less, if necessary. Add a monomer solution in which other toner components such as a charge control agent are dissolved or dispersed, add mechanical energy to form droplets, then add a water-soluble radical polymerization initiator, The polymerization reaction proceeds in the droplet. Note that an oil-soluble polymerization initiator may be contained in the droplet. In such a core resin polymerization process, mechanical energy is imparted and forcedly emulsified (droplet formation) treatment is essential. Examples of the means for applying mechanical energy include means for applying strong stirring or ultrasonic vibration energy such as homomixer, ultrasonic wave, and manton gorin.

  The core resin fine particles formed in this core resin polymerization step can also have a structure of two or more layers made of resins having different compositions. In this case, by emulsion polymerization treatment (first stage polymerization) according to a conventional method. A method in which a polymerization initiator and a polymerizable monomer are added to the prepared dispersion of the first resin particles, and this system is polymerized (second stage polymerization) can be employed.

The average particle diameter of the core resin fine particles obtained in this core resin polymerization step is preferably in the range of, for example, 100 to 300 nm in terms of volume-based median diameter.
The volume-based median diameter of the core resin fine particles was measured using “UPA-150” (manufactured by Microtrack).

  As the surfactant, the polymerization initiator, and the chain transfer agent used in the core resin polymerization step, for example, the same ones that can be used in the above-described first shell resin polymerization step can be used.

  The toner particles of the present invention may contain other toner components such as a charge control agent and magnetic powder, if necessary, in addition to the resin and wax. Thus, for example, in this core resin polymerization step, it can be introduced into the toner particles by dissolving or dispersing in advance in a monomer solution for forming the core resin. In addition, such an internal additive is prepared by separately preparing a dispersion of internal additive fine particles consisting only of the internal additive, and aggregating the internal additive fine particles together with the core resin fine particles and the colorant fine particles in the core particle forming step. Can be introduced into the toner particles, but it is preferable to adopt a method that is introduced in advance in the core resin polymerization step.

(1-4) Colorant fine particle dispersion preparation step The colorant fine particle dispersion can be prepared by dispersing a colorant in an aqueous medium. The colorant dispersion treatment is preferably performed in a state where the surfactant concentration in the aqueous medium is not less than the critical micelle concentration (CMC) since the colorant is uniformly dispersed. Various known dispersers can be used as a disperser used for the dispersion treatment of the colorant.
Examples of the surfactant used include the same surfactants as those described above.

The dispersion diameter of the colorant fine particles in the colorant fine particle dispersion prepared in the colorant fine particle dispersion preparing step is preferably 10 to 300 nm in terms of volume-based median diameter.
The volume-based median diameter of the colorant fine particles in the colorant fine particle dispersion is measured by an electrophoretic light scattering photometer “ELS-800 (manufactured by Otsuka Electronics Co., Ltd.)”.

  The colorant may be introduced into the toner particles by, for example, dissolving or dispersing in advance in a monomer solution for forming the core resin in the core resin polymerization step.

(2) Core particle forming step In the core particle forming step, fine particles of other toner constituent components such as a charge control agent can be aggregated together with the core resin fine particles and the colorant fine particles, if necessary.

  As a specific method for agglomerating and fusing the core resin fine particles and the colorant fine particles, a flocculant is added to an aqueous medium so as to have a critical aggregation concentration or higher, and then the glass transition point of the core resin fine particles or higher. Further, by heating the mixture to a temperature equal to or higher than the melting peak temperature (° C.) of the mixture, the salting out of the fine particles such as the core resin fine particles and the colorant fine particles proceeds, and at the same time, the fusion is proceeded in parallel to obtain desired particles. In this method, the particle growth is stopped by adding a coagulation terminator when it has grown to the diameter, and further, heating is continued to control the particle shape as necessary.

  In this method, the time allowed to stand after addition of the flocculant is shortened as much as possible, and immediately heated to a temperature above the glass transition point of the core resin fine particles and above the melting peak temperature (° C.) of the mixture. It is preferable. The reason for this is not clear, but depending on the standing time after salting out, the aggregation state of the particles may fluctuate and the particle size distribution may become unstable, and the surface properties of the fused particles may vary. This is because there is concern about the occurrence. The time until this temperature rise is usually preferably within 30 minutes, and more preferably within 10 minutes. Moreover, it is preferable that it is 1 degree-C / min or more as a temperature increase rate. The upper limit of the heating rate is not particularly specified, but is preferably 15 ° C./min or less from the viewpoint of suppressing the generation of coarse particles due to rapid progress of fusion. Furthermore, after the reaction system reaches a temperature equal to or higher than the glass transition point, it is important to continue the fusion by maintaining the temperature of the reaction system for a certain time. Thereby, the growth and fusion of the core particles can be effectively advanced, and the durability of the toner particles finally obtained can be improved.

(Flocculant)
As the flocculant used in the core particle forming step, the above-described metal salt is used.
The addition amount of the flocculant is preferably 5.0 to 40.0% by mass, and more preferably 5.0 to 35.0% by mass with respect to the total amount of the resin constituting the toner particles.
When the addition amount of the flocculant is within the above range, the metal ion content in the toner particles can be within the range of the present invention.
When the addition amount of the flocculant is too small, the content of metal ions in the toner particles becomes too small, and it is possible to prevent the seepage of the wax due to the high cross-linking of the toner, so that fixing separation is obtained, but it is formed. The image may become highly glossy. On the other hand, when the addition amount of the flocculant is excessive, the metal ion content in the toner particles becomes excessive, and a low gloss image is obtained due to the high crosslinking of the toner, but the wax exudation is inhibited, and the fixing separation is caused. Sex worsens.

  When a surfactant is used in the core particle forming step, the same surfactants as those listed as the surfactant that can be used in the first shell resin polymerization step can be used, for example. .

The average particle diameter of the core particles obtained in this core particle forming step is preferably such that the volume-based median diameter (D ₅₀ ) is 4.7 to 7.0 μm, more preferably 5.0 to 6.5 μm. It is.
The volume-based median diameter of the core particles is measured by “Coulter Multisizer 3” (manufactured by Coulter Beckman).

(3-1) First shell forming step In the first shell forming step, the first shell resin fine particles are added to the core particle dispersion, and the first shell resin fine particles are aggregated and fused on the surface of the core particles. And the first shell layer is coated on the surface of the core particles.
Specifically, as the core particle dispersion, the first shell resin fine particle dispersion is added while maintaining the temperature in the core particle formation step, and the first shell resin is slowly added over several hours while continuing the heating and stirring. The first-stage shell layer having a thickness of 100 to 300 nm is coated on the surface of the core particles by aggregating and fusing the fine particles on the surface of the core particles. The heating and stirring time is preferably 1 to 7 hours, particularly preferably 3 to 5 hours.
In the toner of the present invention, when the shell layer has a single layer configuration, the first shell forming step or the second shell forming step described later is omitted, so that the toner particles having a single layer core shell structure can be obtained. Can be obtained.

(3-2) Second shell forming step In the second shell forming step, the dispersion of the second shell resin fine particles is added to the dispersion of the core particles on which the first-stage shell layer is formed, followed by heating and stirring. The second shell resin layer having a thickness of 100 to 300 nm is coated by slowly aggregating and fusing the second shell resin fine particles on the surface of the first shell layer over several hours while continuing. The heating and stirring time is preferably 1 to 7 hours, particularly preferably 3 to 5 hours.

(4) Ripening step The shape of the toner particles in the toner can be made uniform to some extent by controlling the heating temperature in the core particle forming step, the first shelling step, and the second shelling step. In order to achieve uniformization, a aging process is performed.
This aging step is controlled by controlling the heating temperature and time so that the surface of the toner particles formed with a constant particle size and a narrow distribution has a smooth but uniform shape. Specifically, in the core particle forming step, the first shell forming step, and the second shell forming step, the heating temperature is lowered to suppress the progress of fusion between the resin fine particles to promote the leveling, and this aging step In this case, the toner particles are controlled to have a desired average circularity, that is, a surface having a uniform shape by lowering the heating temperature and increasing the time.

(5) Washing step to (6) Drying step The washing step and the drying step can be performed by employing various known methods.

(7) External additive addition step This external additive addition step is a step of adding and mixing external additives as necessary to the dried toner particles.
The toner particles produced through the steps up to the drying step can be used as toner particles as they are, but from the viewpoint of improving the charging performance, fluidity, and cleaning properties of the toner, the surface thereof is known. It is preferable to add particles such as inorganic fine particles and organic fine particles, and a lubricant as external additives.
Various external additives may be used in combination.

(External additive)
Examples of the inorganic fine particles include inorganic oxide fine particles such as silica fine particles, alumina fine particles, and titanium oxide fine particles, inorganic stearate compound fine particles such as aluminum stearate fine particles and zinc stearate fine particles, or strontium titanate and zinc titanate. An inorganic titanic acid compound fine particle etc. are mentioned.
These inorganic fine particles are preferably those subjected to surface treatment with a silane coupling agent, a titanium coupling agent, a higher fatty acid, silicone oil, or the like from the viewpoint of heat-resistant storage stability and environmental stability.

The amount of these external additives added is 0.05 to 5 parts by mass, preferably 0.1 to 3 parts by mass with respect to 100 parts by mass of the toner particles.
Examples of the method for adding the external additive include a dry method in which the external additive is added in powder form to the dried toner particles. Examples of the mixing device include mechanical mixing devices such as a Henschel mixer and a coffee mill. .

[Average particle diameter of toner particles]
The average particle diameter of the toner particles constituting the toner of the present invention is preferably, for example, 3 to 10 μm in volume-based median diameter (D ₅₀ ). This average particle diameter can be controlled, for example, by the emulsion polymerization aggregation method, depending on the concentration of the coagulant used, the amount of organic solvent added, the fusing time, and the polymer composition.
When the volume-based median diameter is within the above range, for example, a very small dot image of 1200 dpi (dpi; number of dots per inch (2.54 cm)) level can be faithfully reproduced.

In the present invention, the volume-based median diameter of toner particles is a measuring device in which a computer system equipped with data processing software “Software V3.51” is connected to “Coulter Multisizer 3” (manufactured by Beckman Coulter). Measured and calculated.
Specifically, 0.02 g of a measurement sample (toner) was added to 20 mL of a surfactant solution (for example, a surfactant obtained by diluting a neutral detergent containing a surfactant component 10 times with pure water for the purpose of dispersing toner particles). Solution) and ultrasonically disperse for 1 minute to prepare a toner particle dispersion. This toner particle dispersion is placed in “ISOTONII” (manufactured by Beckman Coulter) in the sample stand. Pipette into a beaker until the displayed concentration of the measuring device is 8%. Here, a reproducible measurement value can be obtained by setting the concentration range. In the measuring apparatus, the frequency value is calculated by setting the number of measured particle counts to 25000 and the aperture diameter to 100 μm, and the particle diameter of 50% from the larger volume integrated fraction is the volume-based median diameter.

[Average circularity of toner particles]
In the toner of the present invention, the arithmetic average value of the circularity represented by the following formula (T) is 0.850 to 0.990 from the viewpoint of improving the transfer efficiency of the individual toner particles constituting the toner. Is preferred.
Formula (T): Circularity = perimeter of perfect circle having projection area equivalent to particle projection image / perimeter of particle projection image

In the present invention, the average circularity of toner particles is measured using “FPIA-2100” (manufactured by Sysmex).
Specifically, the measurement sample (toner) is moistened with an aqueous surfactant solution, and ultrasonic dispersion is performed for 1 minute. After dispersion, the measurement sample is used in the measurement condition HPF (high magnification imaging) mode using “FPIA-2100”. The measurement is performed at an appropriate concentration of 3000 to 10,000 HPF detections. Within this range, reproducible measurement values can be obtained.

[Two-component developer]
The toner of the present invention can be used as a magnetic or non-magnetic one-component developer, but may be mixed with a carrier and used as a two-component developer.
As the carrier, for example, magnetic particles made of conventionally known materials such as metals such as iron, ferrite and magnetite, and alloys of these metals with metals such as aluminum and lead can be used. Among these, ferrite particles Is preferably used.

As the carrier, a coated carrier in which the surface of magnetic particles is coated with a coating agent such as a resin, a resin-dispersed carrier in which a magnetic fine powder is dispersed in a binder resin, or the like may be used.
The carrier particles preferably have a volume average particle diameter of 15 to 100 μm, and more preferably 25 to 80 μm.

(Image forming method)
The toner of the present invention can be used in a general electrophotographic image forming method. In addition, as an image forming apparatus in which such an image forming method is performed, for example, a photosensitive member which is an electrostatic latent image carrier, and a uniform potential is applied to the surface of the photosensitive member by corona discharge having the same polarity as the toner. A charging unit; an exposure unit that forms an electrostatic latent image by performing image exposure on the surface of the uniformly charged photosensitive member based on image data; A developing unit that visualizes the electrostatic latent image to form a toner image, a transfer unit that transfers the toner image to a transfer material via an intermediate transfer member as necessary, and a toner image on the transfer material that is heated and fixed. Those having fixing means can be used. Among image forming apparatuses having such a configuration, a color image forming apparatus having a configuration in which image forming units related to a plurality of photoconductors are provided along the intermediate transfer body, in particular, the photoconductors are arranged in series on the intermediate transfer body. It can be suitably used for the tandem type color image forming apparatus.

  From the above, according to the toner of the present invention, the wax is present only in the thickness portion within 1 μm from the surface of the toner particles, and the metal ion content in the toner particles is within a specific range. While securing the fixing property, it is possible to suppress an excessively high gloss and to obtain an excellent fixing separation property.

  As mentioned above, although embodiment of this invention was described concretely, embodiment of this invention is not limited to said example, A various change can be added.

  Hereinafter, specific examples of the present invention will be described, but the present invention is not limited thereto.

[Preparation of core resin fine particle dispersion [A]]
An anion obtained by dissolving 2.0 parts by mass of anionic surfactant “sodium lauryl sulfate” in 2900 parts by mass of ion-exchanged water in a reaction vessel equipped with a stirrer, a temperature sensor, a temperature controller, a cooling pipe, and a nitrogen introducing unit. The internal temperature was raised to 80 ° C. while charging the neutral surfactant solution and stirring at a stirring speed of 230 rpm under a nitrogen stream.
After adding 9.0 parts by mass of a polymerization initiator “potassium persulfate (KPS)” to this anionic surfactant solution and setting the internal temperature to 78 ° C., 540 parts by mass of styrene, 154 parts by mass of n-butyl acrylate, A monomer solution consisting of 77 parts by mass of methacrylic acid and 17 parts by mass of n-octyl mercaptan was added dropwise over 3 hours. After completion of the dropping, polymerization was carried out by heating and stirring at 78 ° C. for 1 hour to prepare a core resin fine particle dispersion [A] in which the core resin fine particles [A] were dispersed. The core resin fine particles [A] had a glass transition point of 45 ° C., a softening point of 100 ° C., and a volume-based median diameter of 151 nm.

[Preparation of shell resin fine particle dispersion [B]]
(1) First-stage polymerization A reaction vessel equipped with a stirrer, a temperature sensor, a temperature controller, a cooling tube and a nitrogen introducing device was charged with 2.0 parts by mass of an anionic surfactant “sodium lauryl sulfate” in advance with ion-exchanged water 2900. An anionic surfactant solution dissolved in mass parts was charged, and the internal temperature was raised to 80 ° C. while stirring at a stirring speed of 230 rpm under a nitrogen stream.
After adding 9.0 parts by mass of a polymerization initiator “potassium persulfate (KPS)” to this anionic surfactant solution and setting the internal temperature to 78 ° C., 540 parts by mass of styrene, 154 parts by mass of n-butyl acrylate, A monomer solution consisting of 77 parts by mass of methacrylic acid and 17 parts by mass of n-octyl mercaptan was added dropwise over 3 hours. After completion of the dropwise addition, polymerization was carried out by heating and stirring at 78 ° C. for 1 hour to prepare a resin particle dispersion [b-1].

(2) Second stage polymerization In a flask equipped with a stirrer, wax was added to a solution consisting of 94 parts by mass of styrene, 27 parts by mass of n-butyl acrylate, 6 parts by mass of methacrylic acid, and 1.7 parts by mass of n-octyl mercaptan. As a monomer solution, 51 parts by mass of microcrystalline wax (melting point: 80 ° C.) was added and heated to 85 ° C. to dissolve.
On the other hand, a surfactant solution in which 2.0 parts by mass of the anionic surfactant “sodium lauryl sulfate” was dissolved in 1100 parts by mass of ion-exchanged water was heated to 90 ° C., and the above resin particles were added to this surfactant solution. After adding 28 parts by mass of the dispersion [b-1] in terms of solid content, the above monomer solution was mixed for 4 hours with a mechanical disperser “CLEAMIX” (manufactured by M Technique Co., Ltd.) having a circulation path. A dispersion liquid having emulsified particles having a dispersed particle diameter of 350 nm was prepared by dispersing, and a polymerization initiator solution in which 2.5 parts by weight of a polymerization initiator “KPS” was dissolved in 110 parts by weight of ion-exchanged water was added to the dispersion liquid. Polymerization was carried out by heating and stirring the system at 90 ° C. for 2 hours to prepare a resin particle dispersion [b-2].

(3) Third-stage polymerization A polymerization initiator solution prepared by dissolving 2.5 parts by mass of a polymerization initiator “KPS” in 110 parts by mass of ion-exchanged water is added to the resin particle dispersion [b-2], and 80 ° C. The monomer solution consisting of 230 parts by mass of styrene, 78 parts by mass of n-butyl acrylate, 16 parts by mass of methacrylic acid, and 4.2 parts by mass of n-octyl mercaptan was added dropwise over 1 hour. After completion of the dropping, polymerization was carried out by heating and stirring for 3 hours. Then, it cooled to 28 degreeC and prepared shell resin fine particle dispersion [B] in which shell resin fine particles [B] were disperse | distributed in the anionic surfactant solution. The shell resin fine particles [B] had a glass transition point of 53 ° C., a softening point of 100 ° C., and a volume-based median diameter of 256 nm.

[Preparation of shell resin fine particle dispersion [C]]
(1) Synthesis of Shell Resin (Styrene-Acrylic Modified Polyester Resin B) A bisphenol A propylene oxide 2-mol adduct 500 was added to a 10-liter four-necked flask equipped with a nitrogen introduction tube, a dehydration tube, a stirrer and a thermocouple. Part by mass, 117 parts by mass of terephthalic acid, 82 parts by mass of fumaric acid and 2 parts by mass of an esterification catalyst (tin octylate) were subjected to polycondensation reaction at 230 ° C. for 8 hours, and further reacted at 8 kPa for 1 hour, 160 ° C. Then, a mixture of 10 parts by mass of acrylic acid, 30 parts by mass of styrene, 7 parts by mass of butyl acrylate and 10 parts by mass of a polymerization initiator (di-t-butyl peroxide) was added dropwise with a dropping funnel over 1 hour. After dropping, the addition polymerization reaction was continued for 1 hour while maintaining the temperature at 160 ° C., then the temperature was raised to 200 ° C. and 10 kPa. Then, acrylic acid, styrene and butyl acrylate were removed to obtain a styrene-acryl modified polyester resin [c-1]. The glass transition point of the styrene-acryl-modified polyester resin [c-1] was 60 ° C., and the softening point was 100 ° C.

(2) Preparation of Shell Resin Fine Particle Dispersion 100 parts by mass of the obtained styrene-acrylic modified polyester resin [c-1] was pulverized with “Landel mill type: RM” (manufactured by Tokuju Kogakusha Co., Ltd.) and prepared in advance. Mixing with 400 parts by mass of 26 mass% sodium lauryl sulfate solution and ultrasonically dispersing with stirring using an ultrasonic homogenizer “US-150T” (manufactured by Nippon Seiki Seisakusho) at V-LEVEL, 300 μA for 30 minutes, A shell resin fine particle dispersion [C] in which the shell resin fine particles [C] having a volume-based median diameter (D ₅₀ ) of 250 nm are dispersed was prepared.

[Preparation of Colorant Fine Particle Dispersion [D]]
90 parts by weight of sodium dodecyl sulfate was dissolved in 1600 parts by weight of ion-exchanged water while stirring, and while stirring this solution, 420 parts by weight of carbon black “Mogal L” (manufactured by Cabot) was gradually added. A colorant particle dispersion [D] in which the colorant fine particles [D] are dispersed was prepared by performing a dispersion treatment using “Cleamix” (manufactured by M Technique Co., Ltd.). The particle size of the colorant fine particles [D] was measured using a Microtrac particle size distribution measuring device “UPA-150” (manufactured by Nikkiso Co., Ltd.) and found to be 117 nm.

Example 1: Preparation of toner [1] having a two-layer core shell structure
Into a reaction vessel equipped with a stirrer, a temperature sensor and a cooling pipe, 280 parts by mass of the core resin fine particle dispersion [A] and 2000 parts by mass of ion-exchanged water are charged, and 5 mol / liter sodium hydroxide is added. The pH was adjusted to 10 by adding an aqueous solution. Thereafter, 40 parts by mass of the colorant fine particle dispersion [D] was added in terms of solid content, and then an aqueous solution in which 120 parts by mass of magnesium chloride as an aggregating agent was dissolved in 60 parts by mass of ion-exchanged water was stirred at 30 ° C. Added over 10 minutes. Thereafter, the temperature was raised after standing for 3 minutes, and the system was heated to 80 ° C. over 100 minutes (temperature raising rate 0.5 ° C./min), and the particle growth reaction was continued while maintaining 80 ° C. . In this state, the particle size of the core particles is measured by “Coulter Multisizer 3” (manufactured by Coulter Beckman), and when the volume-based median diameter (D ₅₀ ) becomes 5.6 μm, the shell resin fine particles are dispersed. When the liquid [B] is added in 80 parts by mass in terms of solid content over 30 minutes and the supernatant of the reaction liquid becomes transparent, the shell resin fine particle dispersion [C] is added in an amount of 30 parts by mass in terms of solids. When the supernatant of the reaction solution became transparent, an aqueous solution in which 190 parts by mass of sodium chloride was dissolved in 760 parts by mass of ion-exchanged water was added to stop particle growth. Further, the temperature is raised and the mixture is heated and stirred in a state of 90 ° C. to advance the fusing of the particles, and the average circularity measurement apparatus “FPIA-2100” (manufactured by Sysmex) is used (HPF detection). When the average circularity reached 0.945, the mixture was cooled to 30 ° C. to obtain a toner particle dispersion liquid [1] in which toner particles [1] were dispersed.
This toner particle dispersion [1] is solid-liquid separated with a centrifuge to form a wet cake of toner particles, which is ion-exchanged at 35 ° C. until the electrical conductivity of the filtrate reaches 5 μS / cm. After washing with water, it was transferred to a “flash jet dryer” (manufactured by Seishin Enterprise Co., Ltd.) and dried until the water content was 0.5 mass%.
1% by mass of hydrophobic silica (number average primary particle size = 12 nm) and 0.3% by mass of hydrophobic titania (number average primary particle size = 20 nm) are added to the dried toner particles [1], and a Henschel mixer is used. By mixing, Toner [1] was produced.
The volume-based median diameter of the toner particles [1] is 6.4 μm, the average circularity is 0.947, the layer thickness of the first shell layer is 0.5 μm, and the layer thickness of the second shell layer is 0.3 μm. there were. The metal ion content (magnesium ion content) in the toner particles [1] was 4.6 in terms of Net strength. It was also confirmed that the wax was present within 0.8 μm from the surface of the toner particles [1].

[Examples 2 to 7: Preparation of toners [2] to [7] having a two-layer core-shell structure]
Toners [2] to [7] were prepared in the same manner as in Example 1, except that the addition amounts of the shell resin fine particle dispersion [B] and the shell resin fine particle dispersion [C] were changed according to Table 1.
Volume-based median diameter, average circularity, layer thickness of first-stage shell layer and second-stage shell layer, metal ion content (magnesium ion content), and position of wax of toner particles [2]-[7] Is shown in Table 2.

[Comparative Example 1: Preparation of toner [8] having a two-layer core shell structure]
A toner [8] was prepared in the same manner as in Example 1 except that the addition amount of magnesium chloride as the flocculant was changed to 60 parts by mass.
Table 2 shows the volume-based median diameter, average circularity, layer thickness of the shell layer, metal ion content (magnesium ion content), and wax location of the toner particles [8].

[Comparative Example 2: Preparation of toner [9] having a one-layer core shell structure]
Into a reaction vessel equipped with a stirrer, a temperature sensor, and a cooling tube, 288 parts by mass of the shell resin fine particle dispersion [B] in terms of solid content and 2000 parts by mass of ion-exchanged water are added, and 5 mol / liter sodium hydroxide is added. The pH was adjusted to 10 by adding an aqueous solution. Thereafter, 40 parts by mass of the colorant fine particle dispersion [D] was added in terms of solid content, and then an aqueous solution in which 120 parts by mass of magnesium chloride as an aggregating agent was dissolved in 60 parts by mass of ion-exchanged water was stirred at 30 ° C. Added over 10 minutes. Thereafter, the temperature was raised after standing for 3 minutes, and the system was heated to 80 ° C. over 100 minutes (temperature raising rate 0.5 ° C./min), and the particle growth reaction was continued while maintaining 80 ° C. . In this state, the particle size of the core particles is measured with “Coulter Multisizer 3” (manufactured by Coulter Beckman), and when the volume-based median diameter (D ₅₀ ) reaches 6.0 μm, the shell resin fine particles are dispersed. Add 50 parts by mass of liquid [C] over 30 minutes in terms of solid content, and when the supernatant of the reaction solution becomes transparent, add an aqueous solution in which 190 parts by mass of sodium chloride is dissolved in 760 parts by mass of ion-exchanged water. Then, the grain growth was stopped. Further, the temperature is raised and the mixture is heated and stirred in a state of 90 ° C. to advance the fusing of the particles, and the average circularity measurement apparatus “FPIA-2100” (manufactured by Sysmex) is used (HPF detection). When the average circularity reached 0.945, the mixture was cooled to 30 ° C. to obtain a toner particle dispersion [9] in which toner particles [9] were dispersed.
This toner particle dispersion [9] is subjected to solid-liquid separation with a centrifuge to form a wet cake of toner particles, which is ion-exchanged at 35 ° C. until the electric conductivity of the filtrate reaches 5 μS / cm. After washing with water, it was transferred to a “flash jet dryer” (manufactured by Seishin Enterprise Co., Ltd.) and dried until the water content became 0.5% by mass.
1% by mass of hydrophobic silica (number average primary particle size = 12 nm) and 0.3% by mass of hydrophobic titania (number average primary particle size = 20 nm) are added to the dried toner particles [9], and a Henschel mixer is used. By mixing, a toner [9] was produced.
Toner particles [9] had a volume-based median diameter of 6.3 μm, an average circularity of 0.945, and a shell layer thickness of 0.3 μm. The metal ion content (magnesium ion content) in the toner particles [9] was 4.6 in terms of Net strength. It was also confirmed that the wax was present in the interior from 1.0 μm from the surface of the toner particles [9].

[Developer Preparation Examples [1] to [9]]
Toners [1] to [9] were mixed with a silicone carrier-coated ferrite carrier having a volume average particle diameter of 50 nm to prepare dry developers [1] to [9] having a toner concentration of 6% by mass, respectively. .

[Evaluation 1: Low-temperature fixability]
Developers [1] to [9] were mounted on a commercially available color multifunction peripheral “bizhub PRO C6500” (manufactured by Konica Minolta Business Technologies). A fixing device of the color complex machine is used so that the surface temperature of the upper fixing belt can be changed within the range of 140 to 170 ° C. and the surface temperature of the lower fixing roller can be changed within the range of 120 to 150 ° C. A fixing experiment for fixing a solid image with a toner adhesion amount of 11.3 g / m ² at a fixing speed of 300 mm / sec on an evaluation paper “NPi fine paper 128 g / m ² ” (manufactured by Nippon Paper Industries Co., Ltd.) was performed by cold offset. Until fixing failure was observed, the fixing temperature (surface temperature of the fixing upper belt) to be set was changed to 170 ° C., 165 ° C.... The lower fixing roller was always set to a surface temperature 20 ° C. lower than the surface temperature of the upper fixing belt. Then, the lowest fixing temperature in the fixing experiment in which fixing failure due to cold offset was not observed was evaluated as the lower limit fixing temperature. In addition, it means that it is excellent in low temperature fixability, so that this fixing minimum temperature is low, and if it is 155 degrees C or less, it will be judged that there is no problem practically and is a pass. The results are shown in Table 2.

[Evaluation 2: Heat-resistant storage]
After taking 0.5 g of each of toners [1] to [9] into a 10 mL glass bottle with an inner diameter of 21 mm, closing the lid, and shaking 600 times at room temperature using a tap denser “KYT-2000” (manufactured by Seishin Enterprise) The sample was left in an environment of a temperature of 55 ° C. and a humidity of 35% RH for 2 hours with the lid removed. Next, the toner is placed on a 48-mesh (mesh 350 μm) sieve while being careful not to disintegrate the toner aggregates, set in a powder tester (manufactured by Hosokawa Micron), and fixed with a press bar and knob nut. After adjusting the vibration strength to a feed width of 1 mm and applying vibration for 10 seconds, the amount of residual toner remaining on the sieve was measured, and the toner aggregation rate, which is the ratio of the residual toner amount, was calculated by the following formula (1). In addition, if it is 20% or less, it will be judged that there is no problem practically and it is a pass. The results are shown in Table 2.
Formula (1): toner aggregation rate (%) = {residual toner amount (g) /0.5 (g)} × 100

[Evaluation 3: Fixation Separation]
Developers [1] to [9] were mounted on a commercially available color multifunction peripheral “bizhub PRO C6500” (manufactured by Konica Minolta Business Technologies). Using the color multifunction machine, a fixing separation experiment in which a solid image having a margin of 5 mm at the head is formed on an evaluation paper “NPi fine paper 128 g / m ² ” (manufactured by Nippon Paper Industries) until a wrapping phenomenon occurs. The procedure was repeated while changing the set toner adhesion amount to 0.5 g / m ² , 0.6 g / m ² , 0.7 g / m ² ... In increments of 0.1 g / m ² . Then, the maximum value of the toner adhesion amount at which the winding phenomenon does not occur was evaluated as the maximum toner adhesion amount that can be fixed and separated. If the maximum toner adhesion amount is 1.0 g / m ² or more, it is judged as acceptable without any practical problem. The results are shown in Table 2.

[Evaluation 4: Glossiness]
On the evaluation paper “NPi fine paper 128 g / m ² ” (manufactured by Nippon Paper Industries Co., Ltd.), a solid image having a toner adhesion amount of 4.0 g / m ² is formed, and the glossiness is set at a light incident angle of 75 degrees with respect to this image. Was obtained using “Gloss Meter GM-26D” (manufactured by Murakami Color Research Laboratory). If it is 15% or less, it is judged as a low gloss image. The results are shown in Table 2.

  From the above results, in the toners [1] to [7] according to Examples 1 to 7, the toner particles have a core-shell structure, the wax exists only in a thickness portion within 1 μm from the toner particle surface, and It is confirmed that the metal ion content in the toner particles is within a specific range, while maintaining low-temperature fixability and heat-resistant storage stability while suppressing excessive high gloss and providing excellent fixability. It was done. On the other hand, it was confirmed that the toner [8] according to Comparative Example 1 had a high glossiness because the metal ion content in the toner particles was too small. Further, in the toner [9] according to Comparative Example 2, the position of the wax is not present only in the thickness portion within 1 μm from the toner particle surface, that is, the toner is present inside 1 μm from the toner particle surface. It was confirmed that separability could not be obtained.

10 Toner particles 11 Core particles 12 Shell layer 12a First stage shell layer 12b Second stage shell layer 13 Wax

Claims (7)

In an electrostatic charge image developing toner comprising toner particles prepared using a flocculant comprising a metal salt,
The toner particles have a core-shell structure in which a shell layer containing a polyester resin and a wax is formed on core particles made of a styrene-acrylic copolymer resin.
The wax is present only in the thickness portion within 1 μm from the toner particle surface, and the metal ion content derived from the flocculant in the toner particle is 4.0 or more and 7.0 or less in the Net intensity by fluorescent X-ray analysis. A toner for developing an electrostatic charge image. The shell layer has a two-layer structure of a first-stage shell layer formed on the core particle and a second-stage shell layer formed on the first-stage shell layer;
The electrostatic image developing toner according to claim 1, wherein the wax is contained in the first-stage shell layer. The first shell layer is made of a styrene-acrylic copolymer resin,
The electrostatic image developing toner according to claim 2, wherein the second-stage shell layer is made of a polyester resin. The polyester resin constituting the second-stage shell layer is a styrene-acrylic modified polyester resin in which a styrene-acrylic copolymer segment is bonded to the end of the polyester segment,
4. The electrostatic image developing toner according to claim 3, wherein a content ratio of the styrene-acrylic copolymer segment in the styrene-acrylic modified polyester resin is 5% by mass or more and 30% by mass or less.   The electrostatic image developing toner according to claim 1, wherein the shell layer has a layer thickness of 0.10 to 1.00 μm.   The electrostatic charge image developing toner according to claim 2, wherein the second shell layer has a layer thickness of 0.10 to 0.50 μm.   7. The electrostatic image developing toner according to claim 1, wherein the metal ion is divalent.