JP2013011642A - Toner for electrostatic charge image development, and manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide toner for electrostatic charge image development that has sufficient low-temperature fixability when used in a high-speed machine, is excellent in heat-resistant storage performance, experiences less variation in the charge amount, and provides high-quality images in a stable manner.SOLUTION: Toner for electrostatic charge image development is configured in a core-shell structure. A shell layer contains a styrene-acrylic modified polyester resin; the acid value of the styrene-acrylic modified polyester resin is 10 KOHmg/g or more and 40 KOHmg/g or less; an acrylic component that configures the styrene-acrylic modified polyester resin is derived from a polymerizable monomer represented by the following general formula (1). The general formula (1): CH=CR-COOR.

Description

  The present invention relates to an electrostatic charge image developing toner and a manufacturing method thereof, and more particularly to an electrostatic charge image developing toner used in an electrophotographic image forming apparatus and a manufacturing method thereof.

  In recent years, in the field of electrostatic image developing toner, development of an electrophotographic apparatus suitable for the demand from the market and a toner usable for the electrophotographic apparatus are proceeding at a rapid pace. For example, a toner compatible with high image quality is required to have a sharp particle size distribution. When the toner particle size is uniform and the particle size distribution is sharpened, the development behavior of each individual toner particle is uniformed, so that the reproducibility of minute dots is remarkably improved. However, it is not easy to sharpen the particle size distribution of the toner by a conventional toner manufacturing method using a pulverization method.

  On the other hand, an emulsion 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 colorant particle dispersion and, if necessary, a wax dispersion are mixed with an emulsion dispersion of resin particles, and while stirring, each particle is aggregated by addition of a flocculant, pH control, and the like. The toner particles are obtained by fusing the particles.

  Further, 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 the glass transition temperature or molecular weight of the binder resin is lowered in order to lower the melting temperature or melt viscosity of the binder resin, new problems arise, such as the heat resistant storage stability of the toner being lowered.

  In order to achieve both low-temperature fixability and heat-resistant storage stability, a technique for controlling the toner into a core / shell structure has been reported (for example, see Patent Document 1). That is, by forming a shell layer composed of particles having a high softening point and excellent heat resistance on the surface of the core particles excellent in low temperature fixability, it becomes possible to achieve both low temperature fixability and heat resistant storage stability. Particularly in toner production by the emulsion aggregation method, there is an advantage that such shape control can be easily performed. However, as the speed of copiers and printers and the expansion of compatible paper types are increasing in the production printing area in recent years, it has become difficult to achieve both low-temperature fixing and heat-resistant storage stability with the core-shell type toner. .

  In order to solve this problem, a toner using a polyester resin for a shell layer has been developed (for example, see Patent Document 2). Polyester resin has the advantage of being able to easily design a low softening point while maintaining a high glass transition temperature compared to styrene-acrylic resin. By using polyester resin for the shell layer, low-temperature fixability and heat-resistant storage Toner with good properties can be obtained.

  However, styrene-acrylic resin and polyester resin have poor affinity, and when styrene-acrylic resin is used for the core and polyester resin is used for the shell layer, it is difficult to form a thin and uniform shell layer. A sufficient heat-resistant storage property could not be obtained. In addition, it is difficult to control the shape of the toner because the core and the shell are hardly fused, and it is difficult to produce a toner having a smooth shell layer surface. Also, the toner is agitated in the developing machine during continuous printing. As a result, peeling of the shell layer occurred, and as a result, there was a problem that image noise was generated and image quality was lowered.

  In order to solve these problems, a core / shell toner using a urethane-modified polyester resin and / or an acrylic-modified polyester resin in a shell layer has been proposed (see, for example, Patent Document 3). In addition, by using a modified polyester resin in which a radical polymer unit and a polyester resin are bonded via a divalent cross-linking group as a toner resin, a toner that improves low temperature fixing property, high temperature offset property, and charging humidity stability can be obtained. Technology has also been studied (see, for example, Patent Document 4).

JP 2005-221933 A JP 2005-338548 A JP 2005-173202 A JP 2011-28257 A

  In order to improve the affinity between styrene-acrylic resin and polyester resin, urethane-modified polyester resin or acrylic-modified polyester resin is used as the resin constituting the shell layer, and styrene-acrylic resin is used for the core. However, a uniform shell layer can be formed to some extent. However, since the styrene component does not exist in the shell layer, when the low-temperature fixability is further imparted to the core resin, it is still not sufficient in terms of achieving both the low-temperature fixability and the heat-resistant storage property.

  In addition, as described above, it is difficult to obtain a toner having a smooth shell layer surface, and even when treated with an external additive, the external additive is unevenly distributed in the concave portion of the uneven portion of the toner. There was a problem that the function of could not be pulled out sufficiently. Therefore, there is a problem that the fluidity of the toner is lowered and the image is deteriorated.

  In recent years, in the production print area, since printing is performed at high speed, the toner and the toner are easily deteriorated due to a large stress of stirring between the carrier and the toner in the developing machine. That is, detachment of the external additive from the toner base and embedding of the external additive in the toner base are likely to occur. For this reason, the reduction in charge amount is increased. Accordingly, in order to minimize the decrease in the charge amount even under such conditions, it is necessary to suppress the dependency of the charge amount control function on the external additive and to improve the chargeability of the toner base itself.

  The present invention has been made to solve the above-mentioned problems, and has sufficient low-temperature fixability even in a high-speed machine used in a production print region by providing a thin and uniform shell layer on the surface of the core. However, it is an object of the present invention to provide a toner for developing an electrostatic image having a core / shell structure excellent in heat-resistant storage. Another object of the present invention is to provide a toner for developing an electrostatic charge image that can stably obtain a high-quality image with little change in charge amount even when used in a copying machine in a high-speed production print area. The purpose is that.

The above-described problems of the present invention are solved by the following configuration.
1.
A core-shell toner having a shell layer on the surface of core particles containing at least a binder resin,
The shell layer contains a styrene-acrylic modified polyester resin;
The acid value of the styrene-acrylic modified polyester resin is 10 KOHmg / g or more and 40 KOHmg / g or less,
A toner for developing an electrostatic charge image, wherein the acrylic component constituting the styrene-acrylic modified polyester resin is derived from a polymerizable monomer represented by the following general formula (1).
General formula (1)
CH ₂ = _CR 1 -COOR ₂
(In the formula, R ₁ and R ₂ may be the same or different and each represents a hydrogen atom or an alkyl group having 1 to 12 carbon atoms which may have a substituent.)
2.
2. The electrostatic image developing toner according to 1 above, wherein a content ratio of the styrene-acrylic polymer segment in the styrene-acrylic modified polyester resin is 5% by mass or more and 30% by mass or less.
3.
The content ratio of the aliphatic unsaturated dicarboxylic acid component in the polyvalent carboxylic acid component for constituting the polyester segment in the styrene-acryl-modified polyester resin is 25 mol% or more and 75 mol% or less, 3. The toner for developing an electrostatic charge image according to 1 or 2 above.
4).
4. The electrostatic image developing toner according to 3 above, wherein the aliphatic unsaturated dicarboxylic acid is represented by the following general formula (2) or an acid anhydride thereof.
General formula (2)
HOOC- (CR ₃ = CR ₄ ) _n -COOH
(In the formula, R ₃ and R ₄ 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.)
5.
The styrene-acrylic modified polyester resin comprises an aromatic vinyl monomer and a (meth) acrylic acid ester monomer for forming the styrene-acrylic polymer segment of the styrene-acrylic modified polyester resin,
An unmodified polyester resin having a polymerizable unsaturated group and a group capable of reacting with a polyvalent carboxylic acid monomer or a polyhydric alcohol monomer for forming a polyester segment of the styrene-acryl-modified polyester resin 5. The electrostatic charge image developing toner according to any one of 1 to 4, wherein the toner is obtained by polymerization in the presence of
6).
2. A method for producing a toner for developing an electrostatic charge image according to 1 above,
At least a step of preparing an aqueous dispersion of binder resin particles, a step of preparing an aqueous dispersion of colorant particles,
A step of mixing the aqueous dispersion of the binder resin particles and the aqueous dispersion of the colorant particles to prepare a mixed solution;
Adding an aggregating agent to the mixed solution to agglomerate the binder resin particles and the colorant particles to form core particles;
An electrostatic charge image developing toner comprising a step of adding an aqueous dispersion of styrene-acryl-modified polyester resin particles to the aqueous dispersion of core particles to form a shell layer on the surface of the core particles. Production method.

  By adopting the above-described configuration, the present invention is excellent in low-temperature fixability and heat-resistant storage stability, has a small decrease in charge amount, and can stably obtain high-quality images for developing a highly durable electrostatic image. Toner can be obtained.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments for carrying out the present invention will be described in detail, but the present invention is not limited thereto.

  The present invention relates to an electrostatic charge image developing toner and a method for producing the same, and the toner relates to a toner having a core-shell structure having a shell layer on the surface of core particles, and the shell layer is made of styrene-acrylic. Contains a modified polyester resin. Here, the acid value of the styrene-acryl-modified polyester resin constituting the shell layer is 10 KOHmg / g or more and 40 KOHmg / g or less, and the acrylic component constituting the styrene-acryl-modified polyester resin is represented by the following general formula (1). It is derived from a polymerizable monomer.

General formula (1)
CH ₂ = _CR 1 -COOR ₂
(In the formula, R ₁ and R ₂ may be the same or different and each represents a hydrogen atom or an alkyl group having 1 to 12 carbon atoms which may have a substituent.)
Here, the styrene-acryl-modified polyester resin is used as the shell layer resin for the following reason. That is, the advantage of a polyester resin as a toner resin is that a low softening point can be easily designed while maintaining a glass transition temperature higher than that of a styrene-acrylic resin. For this reason, a polyester resin is a preferred resin in order to achieve both low-temperature fixability and heat-resistant storage stability. However, as described above, the polyester resin constituting the shell layer and the styrene-acrylic resin used as the main component for the core particles have poor affinity, and it is difficult to form a thin and uniform shell layer. Therefore, the high glass transition temperature and low softening point of the polyester resin are maintained by bonding the polyester resin used in the shell layer to the polyester resin with a styrene-acrylic resin having an acrylic component represented by the following general formula (1). By increasing the affinity of the core particles with the styrene-acrylic resin as it is, it is possible to form a smooth shell layer having a more uniform film thickness while being a thin layer. This makes it possible to achieve both low-temperature fixability and heat-resistant storage stability. Further, the surface of the shell layer becomes smooth and the concave portions are eliminated, so that the external additive is not unevenly distributed and uniformly on the shell layer surface. Came to exist. The reason why the shell layer became smooth is that the styrene-acrylic modified polyester resin was used for the shell layer, so that the styrene-acrylic part was appropriately compatible with the core particles at the time of aggregation, and as a result, the polyester part was on the outside. It is presumed that a uniform and smooth shell layer is formed due to the orientation. In addition, by using a styrene-acryl-modified polyester resin having a specific acid value as the resin constituting the shell layer, the triboelectric charging property of the polyester segment dominates the charging property of the entire toner, so that the charging property is stable. As a result, it is possible to obtain a toner for developing an electrostatic image that can stably obtain a high-quality image.

≪Shell layer≫
The shell layer constituting the toner of the present invention is made of a shell resin containing a styrene-acrylic modified polyester resin, and the styrene-acrylic modified polyester resin has a styrene-acrylic polymer segment bonded to a polyester segment. The acid value of the styrene-acrylic modified polyester resin is 10 KOHmg / g or more and 40 KOHmg / g or less, and the acrylic component of the styrene-acrylic modified polyester resin is represented by the following general formula (1) It is characterized by being.

General formula (1)
CH ₂ = _CR 1 -COOR ₂
(In the formula, R ₁ and R ₂ may be the same or different and each represents a hydrogen atom or an alkyl group having 1 to 12 carbon atoms which may have a substituent.)
Examples of the resin that can be contained in the shell resin together with the styrene-acrylic modified polyester resin include a styrene-acrylic resin, a polyester resin, and a urethane resin.

  The content of the styrene-acrylic modified polyester resin in the shell resin is preferably 70 to 100% by mass and more preferably 90 to 100% by mass in 100% by mass of the shell resin.

  When the content ratio of the styrene-acrylic modified polyester resin in the shell resin is less than 70% by mass, sufficient affinity between the core particles and the shell layer cannot be obtained, and a desired shell layer cannot be formed. Therefore, there is a possibility that sufficient heat storage stability, chargeability or crushing resistance may not be obtained.

<Styrene-acrylic modification amount>
In the present invention, the content of the styrene-acrylic polymer segment in the styrene-acrylic modified polyester resin (hereinafter also referred to as “styrene-acrylic modification amount”) is 5% by mass or more and 30% by mass or less. Is preferred.

  Specifically, the amount of styrene-acrylic modification is the total mass of the resin material used for synthesizing the styrene-acrylic modified polyester resin, that is, the unmodified polyester resin that becomes the polyester segment, and the styrene-acrylic polymer. Aromatic vinyl monomer and (meth) acrylic acid ester monomer with respect to the total mass of the segmented aromatic vinyl monomer and (meth) acrylic acid ester monomer and both reactive monomers for bonding them The ratio of the mass of

  When the amount of styrene-acrylic modification is in the above range, the affinity between the styrene-acrylic modified polyester resin and the core particles is properly controlled, and a thin shell layer with a more uniform thickness and a smooth layer can be obtained. Can be formed. On the other hand, when the amount of styrene-acryl modification is too small, a shell layer with a uniform film thickness cannot be formed, and the core particles are partially exposed. As a result, sufficient heat storage stability and chargeability are obtained. I can't get it. 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.

<Acid value of polyester resin>
The acid value of the styrene-acryl-modified polyester resin is 10 KOHmg / g or more and 40 KOHmg / g or less. When the acid value is less than 10 KOHmg / g, the triboelectric charging property of the toner base itself is lowered, and the charge amount is further reduced by the detachment and burying of the external additive due to the stress of the toner in the developing device. It becomes larger and the image quality deteriorates. When the acid value exceeds 40 KOHmg / g, the triboelectric charging performance of the polyester resin increases, but the environmental dependency increases. In particular, the transferability is deteriorated due to the influence of moisture in a high temperature and high humidity environment, and the image quality is deteriorated.

(Measurement of acid value)
In the present invention, the acid value of the polyester resin used for the shell layer is a value measured as follows.

  That is, the acid value represents the mass of potassium hydroxide (KOH) necessary for neutralizing the acid contained in 1 g of the polyester resin in mg. The acid value of the polyester resin is measured according to JIS K0070-1966.

Specifically, it is measured according to the following procedure.
(1) Preparation of Reagent 1.0 g of phenolphthalein is dissolved in 90 ml of ethyl alcohol (95% by volume), and ion exchanged water is added to make 100 ml to prepare a “phenolphthalein solution”.

7 g of JIS special grade potassium hydroxide is dissolved in 5 ml of ion exchange water, and ethyl alcohol (95% by volume) is added to make 1 liter. In order to avoid contact with carbon dioxide gas, it is placed in an alkali-resistant container and allowed to stand for 3 days, followed by filtration to produce a “potassium hydroxide solution”. The orientation is in accordance with the description of JIS K0070-1966.
(2) Operation (a) Main test 2.0 g of the pulverized resin sample is precisely weighed into a 200 ml Erlenmeyer flask, and 100 ml of a mixed solution of toluene / ethanol (2: 1) is added and dissolved over 5 hours. Subsequently, several drops of the phenolphthalein solution is added as an indicator, and titration is performed using the potassium hydroxide solution. Note that the end point of the titration is when the light red color of the indicator lasts for about 30 seconds.

(B) Blank test The same operation as described above is performed except that no sample is used (that is, only a mixed solution of toluene / ethanol (2: 1) is used).
(3) Calculation of acid value The obtained result is substituted into the following formula (1) to calculate the acid value.

Formula (1)
A = [(BC) × f × 5.6] / S
here,
A: Acid value (mgKOH / g),
B: Amount of added potassium hydroxide solution for blank test (ml),
C: Amount of added potassium hydroxide solution in this test (ml),
f: Factor of 0.1 mol / liter potassium hydroxide ethanol solution,
S: Sample (g).

  The acid value of the styrene-acrylic modified polyester resin can be controlled by stopping the polymerization reaction when a desired value is reached during polymerization of the polyester segment.

<Styrene-acrylic polymer segment>
The aromatic vinyl monomer and (meth) acrylic acid ester monomer for forming the styrene-acrylic polymer segment constituting the styrene-acrylic modified polyester resin of the present invention are an ethylenic monomer capable of radical polymerization. It has a saturated bond.

(Aromatic vinyl monomer)
Examples of the aromatic vinyl monomer include styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, p-methoxystyrene, p-phenylstyrene, p-chlorostyrene, p-ethylstyrene, and pn. -Butyl styrene, p-tert-butyl styrene, pn-hexyl styrene, pn-octyl styrene, pn-nonyl styrene, pn-decyl styrene, pn-dodecyl styrene, 2,4- Examples thereof include dimethylstyrene, 3,4-dichlorostyrene, and derivatives thereof.

  These aromatic vinyl monomers can be used alone or in combination of two or more.

((Meth) acrylic acid ester monomer)
As the (meth) acrylic acid ester monomer, the (meth) acrylic monomer represented by the general formula (1) is used. For example, acrylic acid, methyl methacrylate, ethyl methacrylate, propyl methacrylate, and methacrylic acid n -Butyl, isobutyl methacrylate, n-octyl methacrylate, decyl methacrylate, undecyl methacrylate, dodecyl methacrylate, 2-ethylhexyl methacrylate, methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, acrylic Examples include propyl acid, n-octyl acrylate, decyl acrylate, undecyl acrylate, dodecyl acrylate, and 2-ethylhexyl acrylate. These (meth) acrylic acid ester monomers can be used alone or in combination of two or more.

In the general formula (1), if the number of carbon atoms of R ₁ and R ₂ exceeds 12, the compatibility with the core is too high, the shell layer is difficult to form, and the acid group of the polyester resin is difficult to be oriented on the surface. Become.

  In the present invention, among the (meth) acrylic acid ester monomers represented by the general formula (1), butyl acrylate or hexyl acrylate is preferable, and 2-ethylhexyl acrylate is more preferable.

<Polyester segment>
(Monomer forming polyester segment>
In the toner of the present invention, a polyvalent carboxylic acid monomer and a polyhydric alcohol monomer are used as monomers for forming the polyester segment of the styrene-acryl-modified polyester resin. In the polyester segment of the styrene-acrylic modified polyester resin of the present invention, an aliphatic unsaturated dicarboxylic acid is used as a polyvalent carboxylic acid monomer, and the polyester segment contains a structural unit derived from the aliphatic unsaturated dicarboxylic acid. It is preferable.

  The aliphatic unsaturated dicarboxylic acid refers to a chain dicarboxylic acid having a vinylene group in the molecule.

  According to the styrene-acryl-modified polyester resin having a structural unit derived from an aliphatic unsaturated dicarboxylic acid, it is possible to reliably form a smooth shell layer having a more uniform film thickness while being a thin layer.

  The proportion of structural units derived from aliphatic unsaturated dicarboxylic acids in the structural units derived from polyvalent carboxylic acid monomers constituting the polyester segment of the styrene-acrylic modified polyester resin (hereinafter referred to as “specific unsaturated dicarboxylic acid-containing” The ratio is also preferably 25 mol% or more and 75 mol% or less, and more preferably 30 mol% or more and 60 mol% or less.

  When the content ratio of the specific unsaturated dicarboxylic acid is within the above range, a smooth shell layer having a more uniform film thickness can be more reliably formed while being a thin layer. On the other hand, if the specific unsaturated dicarboxylic acid content is too small, sufficient heat-resistant storage stability and chargeability may not be obtained, and if the specific unsaturated dicarboxylic acid content is excessive, Sufficient chargeability may not be obtained.

  The structural unit derived from the aliphatic unsaturated dicarboxylic acid is preferably a structural unit derived from the one represented by the following general formula (2). Moreover, when using for superposition | polymerization, you may use with the form of the anhydride of aliphatic dicarboxylic acid represented by following General formula (2).

General formula (2)
HOOC- (CR ₃ = CR ₄ ) _n -COOH
(Wherein R ₃ and R ₄ 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 containing the structural unit derived from such an aliphatic unsaturated dicarboxylic acid, it is possible to more reliably form a smooth shell layer with a more uniform film thickness while being a thin layer.

  That is, in general, polyester resins have hydrophobic properties. When toner particles are produced by the emulsion aggregation method described later, the polyester resin particles are aggregated in the presence of core particles made of styrene-acrylic resin. In other words, so-called homoaggregation occurs. However, when a carbon-carbon double bond is present in the polyester molecule, the hydrophilicity of the polyester resin is increased and homoaggregation hardly occurs. In addition, the increase in hydrophilicity of the polyester resin increases the effect of the polyester segment being oriented outward with respect to the core particles, that is, toward the aqueous medium when toner particles are produced by an emulsion aggregation method in an aqueous medium. A thin and uniform shell layer can be formed.

  Therefore, as described above, the resin constituting the shell layer is a styrene-acrylic modified polyester resin, so that the styrene-acrylic resin of the styrene-acrylic modified resin constituting the shell layer constitutes the core and the styrene-acrylic resin. It is possible to form a uniform and dense shell layer with a much thinner layer due to the hydrophilic effect by the carbon-carbon double bond in the polyester resin segment, while maintaining the affinity of the core particle. It is assumed that

  The shell resin preferably has a glass transition point of 50 to 70 ° C. from the viewpoint of surely obtaining fixing properties such as low-temperature fixing property and fixing separation property, and heat resistance such as heat-resistant storage property and blocking resistance, More preferably, it is 50-65 degreeC, and it is preferable that a softening point is 80-110 degreeC.

  The glass transition point of the shell resin is a value measured by a method (DSC method) defined in ASTM (American Society for Testing and Materials) D3418-82.

  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 shell resin is placed in a petri dish and flattened, and left for 12 hours or more. Then, a molding machine “SSP-10A (manufactured by Shimadzu Corporation) ) ”Is applied with a force of 3820 kg / cm ² for 30 seconds to produce a cylindrical molded sample having a diameter of 1 cm, and this molded sample is then subjected to an environment of 24 ° C. ± 5 ° C. and 50% ± 20% RH. Using a flow tester “CFT-500D (manufactured by Shimadzu Corporation)”, a cylindrical die hole (1 mm diameter) 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. from × 1 mm), extruded from the time of preheating ends with piston diameter 1 cm, the offset method temperature _{T offset} measured by setting the offset value 5mm at a melt temperature measurement method of temperature ramps It is the softening point of the shell resin.

  The content ratio of the shell resin in the binder resin constituting the toner is preferably 5 to 50% by mass, and more preferably 10 to 40% by mass based on the total amount of the binder resin.

  When the content ratio of the shell resin in the binder resin is excessively low, sufficient heat-resistant storage stability may not be obtained, and when the content ratio of the shell resin in the binder resin is excessively high, the temperature is sufficiently low. There is a possibility that the fixing property cannot be obtained.

(Polyester resin)
The polyester resin used for producing the styrene-acrylic modified polyester resin according to the present invention is obtained by polycondensation reaction in the presence of an appropriate catalyst using polyvalent carboxylic acid monomer (derivative) and polyhydric alcohol monomer (derivative) as raw materials It is manufactured.

  As polyvalent carboxylic acid monomer derivatives, alkyl esters, acid anhydrides and acid chlorides of polyvalent carboxylic acid monomers can be used. As polyhydric alcohol monomer derivatives, ester compounds of polyhydric alcohol monomers and hydroxycarboxylic acids are used. Can be used.

  Examples of the polyvalent carboxylic acid monomer include oxalic acid, succinic acid, maleic acid, adipic acid, β-methyladipic acid, azelaic acid, sebacic acid, nonanedicarboxylic acid, decanedicarboxylic acid, undecanedicarboxylic acid, dodecanedicarboxylic acid, fumaric acid. Acid, citraconic acid, diglycolic acid, cyclohexane-3,5-diene-1,2-dicarboxylic acid, malic acid, citric acid, hexahydroterephthalic acid, malonic acid, pimelic acid, tartaric acid, mucoic acid, phthalic acid, Isophthalic acid, terephthalic acid, tetrachlorophthalic acid, chlorophthalic acid, nitrophthalic acid, p-carboxyphenylacetic acid, p-phenylenediacetic acid, m-phenylenediglycolic acid, p-phenylenediglycolic acid, o-phenylenediglycolic acid, Diphenylacetic acid, diphenyl-p, p'- Divalent carboxylic acids such as carboxylic acid, naphthalene-1,4-dicarboxylic acid, naphthalene-1,5-dicarboxylic acid, naphthalene-2,6-dicarboxylic acid, anthracene dicarboxylic acid, dodecenyl succinic acid; trimellitic acid, pyromellitic And divalent or higher carboxylic acids such as acid, naphthalenetricarboxylic acid, naphthalenetetracarboxylic acid, pyrenetricarboxylic acid, and pyrenetetracarboxylic acid.

  As the polyvalent carboxylic acid monomer, an aliphatic unsaturated dicarboxylic acid such as fumaric acid, maleic acid or mesaconic acid is preferably used, and in particular, an aliphatic unsaturated dicarboxylic acid represented by the general formula (2) is used. It is preferable. Moreover, acid anhydrides, such as maleic anhydride, can also be used.

  By using the aliphatic unsaturated dicarboxylic acid, the obtained styrene-acryl-modified polyester resin can surely form a smooth shell layer with a more uniform film thickness while being a thin layer. . In particular, by using the aliphatic unsaturated dicarboxylic acid represented by the general formula (2), the obtained styrene-acryl-modified polyester resin has a more uniform film thickness while being more surely thin. A smooth shell layer can be formed.

  The ratio of the aliphatic unsaturated dicarboxylic acid in the total polyvalent carboxylic acid monomer 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 used is in the above range, the obtained styrene-acryl-modified polyester resin is more surely a thin shell with a more uniform film thickness and a smooth 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.

  Examples of the polyhydric alcohol monomer include ethylene glycol, propylene glycol, butanediol, diethylene glycol, hexanediol, cyclohexanediol, octanediol, decanediol, dodecanediol, ethylene oxide adduct of bisphenol A, propylene oxide adduct of bisphenol A, etc. And trivalent or higher polyols such as glycerin, pentaerythritol, hexamethylol melamine, hexaethylol melamine, tetramethylol benzoguanamine, and tetraethylol benzoguanamine.

<Method for producing styrene-acrylic modified polyester resin>
As a method for producing the styrene-acrylic modified polyester resin contained in the shell resin as described above, an existing general scheme can be used. Typical methods include the following three methods.
(A) A polyester segment is polymerized in advance, and the polyester segment is reacted with both reactive monomers, and further, an aromatic vinyl monomer and a (meth) acrylic acid ester for forming a styrene-acrylic polymer segment. A method of forming a styrene-acrylic polymerized segment by reacting a system monomer.
(B) A styrene-acrylic polymer segment is polymerized in advance, the reactive monomer is reacted with the styrene-acrylic polymer segment, and a polyvalent carboxylic acid monomer and a polyvalent monomer for forming a polyester segment are obtained. A method of forming a polyester segment by reacting a monohydric alcohol monomer.
(C) A method in which a polyester segment and a styrene-acrylic polymer segment are respectively polymerized in advance, and both are reacted with each other by reacting them with each other.
(D) A method in which a polyester segment is polymerized in advance, a styrene-acrylic polymerizable monomer is added to the polymerizable unsaturated group of the polyester segment, and both are bonded.

  In this specification, the both reactive monomers are a group capable of reacting with a polyvalent carboxylic acid monomer and / or a polyhydric alcohol monomer for forming a polyester segment of a styrene-acryl-modified polyester resin, and a polymerizable unsaturated group. And a monomer having

The method (A) will be specifically described.
(1) A mixing step of mixing an unmodified polyester resin, an aromatic vinyl monomer and a (meth) acrylic acid ester monomer, and a bireactive monomer;
(2) The styrene-acrylic polymer segment can be bonded to the polyester segment through a polymerization step of polymerizing the aromatic vinyl monomer and the (meth) acrylic acid ester monomer. In this case, the terminal hydroxyl group of the polyester segment and the carboxy group of both reactive monomers form an ester bond, and the vinyl group of both reactive monomers is the vinyl group of the aromatic vinyl monomer or (meth) acrylic acid monomer. The styrene-acrylic polymer segment is bonded to each other. Of the above synthesis methods, the method (A) is most preferred.

  According to this method, a styrene-acrylic polymer segment can be added to the end of a chain-like polyester segment, and this styrene-acrylic polymer segment has an affinity for the styrene-acrylic resin of the core particle. It is considered that the core-shell toner having a thin and uniform shell layer can be formed in such a manner that the polyester segments are exposed to the toner surface.

  In the mixing step (1), it is preferable to heat. The heating temperature may be a range in which an unmodified polyester resin, aromatic vinyl monomer, (meth) acrylic acid ester monomer and amount-reactive monomer can be mixed, and good mixing is obtained. Since polymerization control becomes easy, it can be set to 80-120 degreeC, for example, More preferably, it is 85-115 degreeC, More preferably, it is 90-110 degreeC.

  Of unmodified polyester resin, aromatic vinyl monomer, (meth) acrylic acid ester monomer and both reactive monomers, the proportion of aromatic vinyl monomer and (meth) acrylic acid ester monomer used is the resin used The total ratio of the aromatic vinyl monomer and the (meth) acrylic acid ester monomer when the total mass of the material, that is, the total mass of the above four parties is 100 mass% is set to 5 mass% or more and 30 mass% or less. In particular, it is preferably 5% by mass or more and 20% by mass or less.

  Affinity between the styrene-acrylic modified polyester resin and the core particles is appropriate because 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. Therefore, it is possible to form a smooth shell layer with a more uniform film thickness while being a thin layer. On the other hand, when the ratio is too small, the resulting styrene-acryl-modified polyester resin cannot form a shell layer with a uniform film thickness, resulting in partial exposure of the core particles. Therefore, sufficient heat storage stability and chargeability cannot be obtained for the obtained toner. 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 to 80 ° C., The ratio is preferably in the range of 40 to 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 above four factors The ratio of both reactive monomers is 100% by mass or more and 5.0% by mass or less, and particularly 0.5% by mass or more and 3.0% by mass or less, when the total mass is 100% by mass. It is preferable.

  As aromatic vinyl monomers and (meth) acrylic acid ester monomers for forming styrene-acrylic polymer segments, styrene or its derivatives are often used from the viewpoint of obtaining excellent chargeability and image quality characteristics. Is preferred. Specifically, the amount of styrene or its derivative used is 50 mass in all monomers (aromatic vinyl monomer and (meth) acrylic acid ester monomer) used to form the styrene-acrylic polymer segment. % Or more is preferable.

(Amotropic monomer)
As the both reactive monomers for forming a styrene-acrylic polymer segment, a group capable of reacting with a polyvalent carboxylic acid monomer and / or a polyhydric alcohol monomer for forming a polyester segment, a polymerizable unsaturated group, Specifically, for example, acrylic acid, methacrylic acid, fumaric acid, maleic acid, maleic anhydride, and the like can be used. In the present invention, it is preferable to use acrylic acid or methacrylic acid.

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

  As the catalyst for synthesizing the polyester resin, various conventionally known catalysts can be used.

  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 binder 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 step of polymerizing the aromatic vinyl monomer and the (meth) acrylic acid ester monomer, the polymerization is preferably performed in the presence of a radical polymerization initiator, and the timing of adding the radical polymerization initiator is not particularly limited. However, it is preferably added after the mixing step in terms of easy control of radical polymerization.

  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 polymerization step of polymerizing the aromatic vinyl monomer and the (meth) acrylic acid ester monomer, a chain transfer agent generally used for the purpose of adjusting the molecular weight of the styrene-acrylic polymer segment. Can be used. The chain transfer agent is not particularly limited, and examples thereof include alkyl mercaptans and mercapto fatty acid esters.

  The chain transfer agent is preferably mixed with the resin material in the mixing step.

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

  The polymerization temperature in the polymerization step for polymerizing the aromatic vinyl monomer and the (meth) acrylic acid ester monomer is not particularly limited, and the polymerization between the aromatic vinyl monomer and the (meth) acrylic acid ester monomer and the polyester resin In the range where the coupling | bonding to progresses, it can select suitably. 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 the styrene-acrylic modified polyester resin, it is practically preferable that volatile organic substances from the emulsion such as the amount of residual monomer after the polymerization step are suppressed to 1,000 ppm or less, more preferably 500 ppm or less, Preferably it is 200 ppm or less.

  As described above, in the present invention, the styrene-acrylic modified polyester resin means that the polyester segment and the styrene-acrylic resin segment are bonded via both reactive monomers, and the styrene-acrylic resin segment is fine in the polyester segment. It is a composite resin configured in a uniformly dispersed state.

≪Core particle≫
In the present invention, the core particles contain at least a binder resin. In addition to the binder resin, a colorant can be contained depending on the purpose of use. The binder resin constituting the core particle is not particularly limited as long as it is conventionally used as a binder resin for an electrophotographic toner, and various resins can be used, preferably a vinyl resin. Further, a styrene-acrylic resin is preferably used.

  As a method for forming the core particle, it can be produced by a known method, but an emulsion aggregation method in which resin particles dispersed in an aqueous medium and colored particles are aggregated to form core particles is preferably used. 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.

  When the core particles have a configuration in which resin particles made of styrene-acrylic resin are aggregated / fused, the core particles are usually formed by an emulsion aggregation method. When adopting the emulsion aggregation method, in detail, resin particles and colorant particles obtained by emulsifying and dispersing a polymerizable monomer in an aqueous medium and polymerizing, if necessary, an anti-offset agent such as wax, a charge control agent, magnetic powder, etc. In the aqueous medium, the core particles may be formed by agglomeration / fusion in the aqueous medium, or the polymerizable monomer is added in the aqueous medium in the presence of the emulsified offset inhibitor or charge control agent additive. The core particles may be formed by seed emulsion polymerization. The particle diameter of the resin particles is usually preferably in the range of 50 nm to 500 nm in terms of weight average particle diameter.

  When the shell layer is uniformly formed on the surface of the core particle, it is preferable to employ an emulsion aggregation method. When the emulsion aggregation method is employed, an emulsion dispersion of shell particles can be added to an aqueous dispersion of core particles, and the shell particles can be aggregated / fused on the surface of the core particles.

  The aromatic vinyl monomer and (meth) acrylic acid ester monomer for forming the styrene-acrylic resin used for the core particles of the present invention have an ethylenically unsaturated bond capable of radical polymerization. is there.

(Aromatic vinyl monomer)
Examples of the aromatic vinyl monomer include styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, p-methoxystyrene, p-phenylstyrene, p-chlorostyrene, p-ethylstyrene, and pn. -Butyl styrene, p-tert-butyl styrene, pn-hexyl styrene, pn-octyl styrene, pn-nonyl styrene, pn-decyl styrene, pn-dodecyl styrene, 2,4- Examples thereof include dimethylstyrene, 3,4-dichlorostyrene, and derivatives thereof.

  These aromatic vinyl monomers can be used alone or in combination of two or more.

((Meth) acrylic acid ester monomer)
Examples of (meth) acrylic acid ester monomers include acrylic acid, methyl methacrylate, ethyl methacrylate, propyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, n-octyl methacrylate, decyl methacrylate, and undecyl methacrylate. , Dodecyl methacrylate, 2-ethylhexyl methacrylate, methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, propyl acrylate, n-octyl acrylate, decyl acrylate, undecyl acrylate, dodecyl acrylate And 2-ethylhexyl acrylate. These (meth) acrylic acid ester monomers can be used alone or in combination of two or more.

  A third vinyl monomer can also be used as the polymerizable monomer. Examples of the third vinyl monomer include acid monomers such as acrylic acid, methacrylic acid, maleic anhydride, and vinyl acetate, acrylamide, methacrylamide, acrylonitrile, ethylene, propylene, butylene vinyl chloride, N-vinyl pyrrolidone, and butadiene. It is done.

  The copolymerization ratio of these polymerizable monomers is selected so that the glass transition temperature of the resin constituting the obtained core particle is 30 ° C. to 60 ° C., preferably 30 ° C. to 50 ° C. The softening point is 80 ° C to 110 ° C, preferably 90 ° C to 100 ° C.

  A polyfunctional vinyl monomer may be further used as the polymerizable monomer. Examples of the polyfunctional vinyl monomer include diacrylates such as ethylene glycol, propylene glycol, butylene glycol and hexylene glycol, dimethacrylates and trimethacrylates of tertiary alcohols such as divinylbenzene, pentaerythritol, and trimethylolpropane. Can be mentioned. The copolymerization ratio of the polyfunctional vinyl monomer to the entire polymerizable monomer is usually 0.001 to 5% by mass, preferably 0.003 to 2% by mass, and more preferably 0.01 to 1% by mass.

  By using a polyfunctional vinyl monomer, a gel component insoluble in tetrahydrofuran is produced, but the proportion of the gel component in the whole polymer is usually 40% by mass or less, preferably 20% by mass or less.

  In the present invention, a polymerization initiator and a chain transfer agent may be added together with the polymerizable monomer.

(Polymerization initiator)
In the polymerization step of polymerizing the styrene-acrylic resin used for the core particles of the present invention, it is preferable to perform polymerization in the presence of a radical polymerization initiator, and the timing of addition of the radical polymerization initiator is not particularly limited, In view of easy control of radical polymerization, it is preferably added after the mixing step.

  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)
Moreover, in the said superposition | polymerization process, the chain transfer agent generally used can be used in order to adjust the molecular weight of a styrene-acrylic-type polymer 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 preferably mixed with the resin material in the mixing step.

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

  The polymerization temperature in the polymerization step for polymerizing the aromatic vinyl monomer and the (meth) acrylic acid ester monomer is not particularly limited, and the polymerization between the aromatic vinyl monomer and the (meth) acrylic acid ester monomer and the polyester It can select suitably in the range in which the coupling | bonding to resin advances. 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 the styrene-acrylic modified polyester resin, it is practically preferable that volatile organic substances from the emulsion such as the amount of residual monomer after the polymerization step are suppressed to 1,000 ppm or less, more preferably 500 ppm or less, Preferably it is 200 ppm or less.

(Surfactant)
When a styrene-acrylic resin is dispersed in an aqueous medium and polymerized by an emulsion polymerization method, a dispersion stabilizer is usually added to prevent aggregation of the dispersed droplets. As the dispersion stabilizer, a known surfactant can be used, and a dispersion stabilizer selected from a cationic surfactant, an anionic surfactant, a nonionic surfactant and the like can be used. Two or more of these surfactants may be used in combination. The dispersion stabilizer can also be used in a dispersion liquid such as a colorant and an offset preventing agent.

  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 dodecylbenzene sulfonate, polyoxyethylene (2) sodium lauryl ether sulfate and the like. it can.

  A colorant, a wax, and a charge control agent can be added to the toner of the present invention as necessary.

(Coloring agent)
As the colorant to be used, carbon black, magnetic substance, dye, pigment, etc. can be arbitrarily used, and as channel black, furnace black, acetylene black, thermal black, lamp black, etc. are used as carbon black. . 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 dye, C.I. I. Solvent Red 1, 49, 52, 58, 63, 111, 122, 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. Examples of the pigment include C.I. I. Pigment Red 5, 48: 1, 48: 3, 53: 1, 57: 1, 81: 4, 122, 139, 144, 149, 166, 177, 178, 222, C.I. I. Pigment Orange 31 and 43, C.I. I. Pigment Yellow 14, 17, 74, 93, 94, 138, 155, 180, 185, C.I. I. Pigment green 7, C.I. I. Pigment Blue 15: 3, 15: 4, 60, and the like, and a mixture thereof can also be used. The number average primary particle diameter varies depending on the type, but is preferably about 10 to 200 nm.

(wax)
Examples of the wax include low molecular weight polyethylene wax, low molecular weight polypropylene wax, Fischer-Tropsch wax, microcrystalline wax, hydrocarbon waxes such as paraffin wax, carnauba wax, pentaerythritol behenate, behenyl behenate, And ester waxes such as behenyl acid. These can be used alone or in combination of two or more.

  The content of the wax is 2 to 20% by mass, preferably 3 to 18% by mass, and more preferably 4 to 15% by mass, based on the total mass of the resin particles.

  Further, the melting point of the wax is preferably 50 to 95 ° C. from the viewpoint of low-temperature fixability and releasability of the toner in electrophotography.

(Charge control agent)
As the charge control agent constituting the charge control agent particles, various known ones that can be dispersed in an aqueous medium can be used. Specific examples include nigrosine dyes, naphthenic acid or higher fatty acid metal salts, alkoxylated amines, quaternary ammonium salt compounds, azo metal complexes, salicylic acid metal salts or metal complexes thereof.

  The charge control agent particles preferably have a number average primary particle diameter of about 10 to 500 nm in a dispersed state.

<Description of toner base particles>
Next, the toner base particles used in the present invention will be described. The “toner base particles” referred to in the present invention are particles having a core / shell structure having a shell layer on the surface of the core particles. The toner base particles can be used as toner particles as they are, but it is usually preferable to add the external additives. The toner is an aggregate of toner particles.

(Average circularity)
First, the average circularity of the toner particles used in the present invention will be described. The average circularity of the toner particles used in the present invention is preferably from 0.850 to 0.990. Here, the average circularity of the toner particles is a value measured using “FPIA-2100 (manufactured by Sysmex)”.

  Specifically, the toner particles are moistened with an aqueous surfactant solution, and ultrasonic dispersion is performed for 1 minute. After dispersion, HPFP detection is performed in the measurement condition HPF (high magnification imaging) mode using “FPIA-2100”. Measurement is performed at appropriate concentrations of several thousand to 10,000. Within this range, reproducible measurement values can be obtained. The circularity is calculated by the following formula.

Average circularity = (perimeter of a circle having the same projection area as the particle image) / (perimeter of the particle projection image)
The average circularity is an arithmetic average value obtained by adding the circularity of each particle and dividing by the total number of particles measured.

(Particle size of toner particles)
Next, the particle size of the toner particles used in the present invention will be described. The toner particles used in the present invention preferably have a volume-based median diameter (D ₅₀ ) of 3 μm or more and 10 μm or less.

  By setting the volume reference median diameter in the above range, for example, it is possible to faithfully reproduce a very minute dot image at a level of 1200 dpi (dpi; number of dots per inch (2.54 cm)).

The volume-based median diameter (D ₅₀ ) of the toner particles can be measured and calculated using, for example, a device in which a computer system for data processing is connected to “Multisizer 3 (manufactured by Beckman Coulter)”.

  As a measurement procedure, 0.02 g of toner particles are used in 20 ml of a surfactant solution (for example, a surfactant solution obtained by diluting a neutral detergent containing a surfactant component 10 times with pure water for the purpose of dispersing toner particles). After being blended, ultrasonic dispersion is performed for 1 minute to prepare a toner particle dispersion. This toner particle dispersion is poured into a beaker containing ISOTON II (manufactured by Beckman Coulter) in a sample stand with a pipette until the measured concentration becomes 5 to 10%, and the measuring machine count is set to 25,000. taking measurement. The aperture size of the multisizer 3 is 100 μm.

(Toner softening point)
The softening point of the toner of the present invention is preferably 90 ° C to 115 ° C. When the softening point of the toner is within this range, preferable low-temperature fixability can be obtained.

  The softening point can be measured by the above-described method, that is, “Flow Tester CFT-500D (manufactured by Shimadzu Corporation)”.

≪Method for producing toner base particles≫
Next, a method for producing toner base particles used in the present invention will be described.

  The toner base particles used in the present invention are particles containing at least a binder resin and a colorant, and constitute a base of toner particles used for electrophotographic image formation. These are called colored particles.

  Examples of the method for producing the toner base particles of the present invention include a suspension polymerization method, an emulsion aggregation method, and other known methods. The emulsion aggregation method is preferably used. According to this emulsion aggregation method, the toner particles can be easily reduced in size from the viewpoint of production cost and production stability.

  Here, the emulsion aggregation method refers to a dispersion of binder resin particles (hereinafter also referred to as “binder resin particles”) produced by emulsification, and, if necessary, particles of colorant (hereinafter referred to as “coloring”). In this method, toner particles are produced by mixing with a dispersion liquid (also referred to as “agent particles”), aggregating until a desired toner particle diameter is obtained, and further fusing the binder resin particles to control the shape. is there. Here, the binder resin particles may optionally contain a release agent, a charge control agent, and the like.

An example of using the emulsion aggregation method as a method for producing the toner is shown below.
(1) Step of preparing a dispersion liquid in which colorant particles are dispersed in an aqueous medium (2) Dispersion liquid in which binder resin particles containing an internal additive are dispersed in an aqueous medium as necessary (3) A step of mixing the colorant particle dispersion and the binder resin particle dispersion to agglomerate and fuse the colorant particles and the binder resin particles to form toner particles (4) ) A step of filtering out toner particles from a dispersion system (aqueous medium) of toner particles and removing a surfactant, etc. (5) A step of drying toner particles (6) A step of adding an external additive to the toner particles As a method for dispersing the binder resin particles in the step 2), it is preferable to use an emulsion polymer particle dispersion obtained by emulsion polymerization. The binder resin particles may have a multilayer structure of two or more layers made of binder resins having different compositions. For the binder resin particles having such a structure, for example, those having a two-layer structure, a dispersion of resin particles is prepared by emulsion polymerization treatment (first-stage polymerization) according to a conventional method, and polymerization is started in this dispersion. An agent and a polymerizable monomer are added, and this system can be obtained by a technique of polymerization treatment (second stage polymerization).

  In the emulsion aggregation method, it is also possible to obtain toner particles having a core / shell structure. Specifically, toner particles having a core / shell structure are prepared by first binding resin particles for core particles and colorant particles. Then, core particles are prepared by agglomerating and fusing, and then the binder resin particles for the shell layer are added to the core particle dispersion to agglomerate and fuse the binder resin particles for the shell layer on the core particle surface. It can be obtained by forming a shell layer that coats the surface of the core particles.

(Process for producing core particles)
As a method for forming the core particles, a known method can be used, but an emulsion aggregation method in which the resin particles dispersed in the aqueous medium and the colorant particles are aggregated to form the core particles is preferably used.

  When the core particles have a configuration in which resin particles made of styrene-acrylic resin are aggregated / fused, the core particles are usually formed by an emulsion aggregation method. When adopting the emulsion aggregation method, in detail, resin particles and colorant particles obtained by emulsifying and dispersing a polymerizable monomer in an aqueous medium and polymerizing, if necessary, an anti-offset agent such as wax, a charge control agent, magnetic powder, etc. The core particles may be formed by agglomeration / fusion in an aqueous medium together with other additives, or the polymerizable monomer is added in an aqueous medium in the presence of an emulsified anti-offset agent or charge control agent additive. The core particles may be formed by seed emulsion polymerization. The particle diameter of the resin particles is usually preferably in the range of 50 nm to 500 nm in terms of weight average particle diameter.

(Method for forming shell layer)
When the shell layer is uniformly formed on the surface of the core particle, it is preferable to employ an emulsion aggregation method. When the emulsion aggregation method is employed, an emulsion dispersion of shell particles can be added to an aqueous dispersion of core particles, and the shell particles can be aggregated / fused on the surface of the core particles.

  In particular, the toner of the present invention is a mixture of a dispersion liquid in which colorant particles are dispersed in an aqueous medium and a dispersion liquid in which binder resin particles are dispersed in an aqueous medium, whereby the colorant particles and the binder are mixed. It is preferably obtained by a process of aggregating and fusing the resin particles, that is, obtained by a production method such as an emulsion aggregation method.

  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.

(Surfactant)
A dispersion stabilizer is usually added to the aqueous medium in order to prevent aggregation of dispersed droplets. As the dispersion stabilizer, a known surfactant can be used, and a dispersion stabilizer selected from a cationic surfactant, an anionic surfactant, a nonionic surfactant and the like can be used. Two or more of these surfactants may be used in combination. The dispersion stabilizer can also be used in a dispersion liquid such as a colorant and an offset preventing agent.

  Specific examples of the cationic surfactant include dodecyl ammonium bromide, dodecyl trimethyl ammonium bromide, dodecyl pyridinium chloride, dodecyl pyridinium bromide, hexadecyl trimethyl ammonium 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 dodecylbenzene sulfonate, polyoxyethylene (2) sodium lauryl ether sulfate and the like. it can.

(Dispersion of colorant)
A dispersion of colorant particles can be prepared by dispersing a colorant in an aqueous medium. The dispersion treatment of the colorant is preferably performed in a state where the surfactant concentration in the aqueous medium is equal to or higher than the critical micelle concentration because the colorant is uniformly dispersed. A known disperser can be used as the disperser used for the dispersion treatment of the colorant. Moreover, as a surfactant which can be used, a publicly known thing can be used.

  The particle diameter of the colorant particles in the step (1) of adjusting the colorant dispersion is preferably 10 to 300 nm in terms of volume-based median diameter.

(Measurement of dispersed particle size in colorant dispersion)
The dispersion particle diameter of the colorant particles in the aqueous medium is a volume average particle diameter, that is, a median diameter based on a fixed volume, and this median diameter is measured using a microtrack particle size distribution measuring apparatus “UPA-150 (Nikkiso Co., Ltd.)”. Measured value.

(Measurement condition)
(1) Sample refractive index: 1.59
(2) Sample sample specific gravity: 1.05 (in terms of spherical particles)
(3) Solvent refractive index: 1.33
(4) Solvent viscosity: 0.797 at 30 ° C
1.002 at 20 ° C
Ion exchange water is put into the measurement cell, and the zero point adjustment is performed.

(Aggregating process)
Next, the step of aggregating and associating resin particles and colorant particles in the emulsion aggregation method will be described.

  In the aggregation / aggregation step, an aqueous dispersion of resin particles is mixed with a dispersion of colorant particles and, if necessary, wax particle charge control agent particles and other toner constituent particles to prepare an aggregation dispersion. Then, it is aggregated and fused in an aqueous medium to form a dispersion of colored particles.

  The flocculant used in the present invention is not particularly limited, but those selected from metal salts are preferably used. For example, salts of monovalent metals such as alkali metal salts such as sodium, potassium and lithium, salts of divalent metals such as calcium, magnesium, manganese and copper, salts of trivalent metals such as iron and aluminum Specific examples of the salt include sodium chloride, potassium chloride, lithium chloride, calcium chloride, magnesium chloride, zinc chloride, copper sulfate, magnesium sulfate, and manganese sulfate. A divalent metal salt is preferred. When a divalent metal salt is used, agglomeration can be promoted with a smaller amount. These may be used alone or in combination of two or more.

  In the aggregation / aggregation step, it is preferable that the standing time (time until heating is started) to be left after adding the aggregating agent is as short as possible. That is, after adding the flocculant, it is preferable to start heating the flocculating dispersion liquid as quickly as possible so as to be equal to or higher than the glass transition point of the resin composition. The reason for this is not clear, but the agglomeration state of the particles fluctuates with the passage of the standing time, and there is a possibility that the particle size distribution of the obtained toner particles becomes unstable or the surface property fluctuates. Because there is. The standing time is usually within 30 minutes, preferably within 10 minutes.

  In the aggregation and association step, it is preferable to quickly raise the temperature by heating, and the rate of temperature rise is preferably 1 ° C./min or more. The upper limit of the heating rate is not particularly limited, 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, it is important to continue the fusion by holding the temperature of the aggregation dispersion liquid for a certain period of time after the aggregation dispersion liquid reaches a temperature equal to or higher than the glass transition temperature. Thereby, the growth and fusion of the colored particles can be effectively advanced, and the durability of the toner particles finally obtained can be improved.

(External additive)
In the present invention, an external additive can be added for the purpose of improving the fluidity and charging characteristics of the toner.

  Examples of the external additive used in the present invention 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 inorganic fine particles such as inorganic titanic acid compound fine particles such as zinc titanate.

  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 addition amount of the external additive 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 base particles. Various external additives may be used in combination.

  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 base particles. Examples of the mixing device include mechanical mixing devices such as a Henschel mixer and a coffee mill. It is done.

(Developer)
The toner of the present invention can be used as a two-component developer composed of a carrier and a toner, or as a non-magnetic one-component developer composed only of a toner.

  Carriers that are magnetic particles used when used as a two-component developer are conventionally known materials such as metals such as iron, ferrite, and magnetite, and alloys of these metals with metals such as aluminum and lead. It is possible to use. Among these, ferrite particles are preferable. Further, as the carrier, a coated carrier in which the surface of the magnetic particles is coated with a coating agent such as a resin, a resin dispersion type carrier in which a magnetic fine powder is dispersed in a binder resin, or the like may be used. The carrier has a volume average particle size of preferably 15 to 100 μm, more preferably 25 to 80 μm.

(Image forming device)
An image forming apparatus in which the toner of the present invention is used includes an electrostatic latent image carrier (typically an electrophotographic photoreceptor, hereinafter simply referred to as a photoreceptor), and charging means, exposure means, and toner. Developing means using a developer, and transfer means for transferring a toner image formed by the developing means to a transfer material via an intermediate transfer member. In particular, it is effective to use for color image forming devices that sequentially transfer the toner images on the photosensitive member to the intermediate transfer member, tandem type color image forming devices in which a plurality of photosensitive members for each color are arranged in series on the intermediate transfer member, etc. It is.

  EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.

The toner of the present invention was prepared by the following procedure.
(1) Preparation of resin particles for core (A) Dispersion (2) Preparation of resin particles for shell [B] Dispersion (3) Preparation of colorant particle dispersion (1) (4) Aggregation / fusion-out Additive treatment step The following will be described in order.
(1) Preparation of resin particles for core (A) dispersion (1-1) First stage polymerization (preparation of “resin particle (a1)” dispersion)
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 surfactant solution and adjusting the internal temperature to 78 ° C.,
Monomer solution (1)
Styrene 540 parts by weight n-butyl acrylate 270 parts by weight Methacrylic acid 65 parts by weight n-octyl mercaptan 17 parts by weight of monomer solution (1) was added dropwise over 3 hours. Polymerization (first stage polymerization) was carried out by stirring to prepare a “resin particle (a1)” dispersion.

(1-2) Second-stage polymerization: formation of intermediate layer (preparation of “resin particle (a11)” dispersion)
In a flask equipped with a stirrer,
Styrene 94 parts by weight n-butyl acrylate 60 parts by weight Methacrylic acid 11 parts by weight n-octyl mercaptan 5 parts by weight Paraffin wax (melting point: 73 ° C.) 51 parts by weight is added as a release agent to 85 ° C. A monomer solution (2) was prepared by heating and dissolving.

  On the other hand, a surfactant solution in which 2 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 “resin particles (a1)” was added to the surfactant solution. After adding 28 parts by mass of the dispersion of resin particles (a1) in terms of solid content, the monomer solution (2) was added using a mechanical disperser “CLEAMIX (manufactured by M Technique)” having a circulation path. Was mixed and dispersed for 4 hours to prepare a dispersion containing emulsified particles having a dispersed particle diameter of 350 nm, and 2.5 parts by mass of a polymerization initiator “KPS” was dissolved in 110 parts by mass of ion-exchanged water. An aqueous initiator solution was added, and the system was heated and stirred at 90 ° C. for 2 hours to conduct polymerization (second stage polymerization) to prepare a “resin particle (a11)” dispersion.

(1-3) Third-stage polymerization: Formation of outer layer (Preparation of “core resin particle (A) dispersion”)
An initiator aqueous solution in which 2.5 parts by mass of a polymerization initiator “KPS” is dissolved in 110 parts by mass of ion-exchanged water is added to the dispersion of the “resin particles (a11)”, and the temperature is 80 ° C. ,
Monomer solution (3)
Styrene 230 parts by mass n-butyl acrylate 100 parts by mass n-octyl mercaptan 5.2 parts by mass A monomer solution (3) was added dropwise over 1 hour. After completion of the dropwise addition, polymerization (third stage polymerization) was carried out by heating and stirring for 3 hours. Then, it cooled to 28 degreeC and produced "the resin particle for cores (A) dispersion | distribution liquid" in which the resin particles for cores (A) were disperse | distributed in the anionic surfactant solution.
(2) Process for producing resin particles for shell [B] dispersion (2-1) Synthesis of resin for shell [B1] (styrene-acryl-modified polyester resin [B1]) Nitrogen introduction tube, dehydration tube, stirrer, and thermoelectric In a four-necked flask equipped with a pair,
Bisphenol A propylene oxide 2-mole adduct 500 parts by mass Terephthalic acid 117 parts by mass Fumaric acid 82 parts by mass Esterification catalyst (tin octylate) 2 parts by mass are put into a polycondensation reaction at 230 ° C for 8 hours, and further reacted at 8 kPa. The reaction was stopped when the acid value reached 25 KOH mg / g. After cooling to 160 ° C,
Acrylic acid 10 parts by weight Styrene 30 parts by weight 2-ethylhexyl acrylate 7 parts by weight Polymerization initiator (di-t-butyl peroxide) 10 parts by weight of the mixture was dropped with a dropping funnel over 1 hour. The resin for shell [B1] was obtained by continuing the addition polymerization reaction for 1 hour while keeping the temperature at 200 ° C. and holding at 10 kPa for 1 hour, and then removing acrylic acid, styrene and butyl acrylate. (Styrene-acrylic modified polyester resin [B1]) was obtained.

  This shell resin [B1] had a glass transition point of 60 ° C. and a softening point of 105 ° C.

(2-2) Preparation of Resin Particles for Shell [B1] Dispersion 100 parts by mass of the obtained resin for shell [B1] (styrene-acrylic modified polyester resin [B1]) was used as a “Landel mill type: RM (Tokuju Factory) ), And mixed with 638 parts by mass of a sodium lauryl sulfate solution having a concentration of 0.26% by mass prepared in advance, and using an ultrasonic homogenizer “US-150T (manufactured by Nippon Seiki Seisakusho)” while stirring. -LEVEL, ultrasonically dispersed at 300 μA for 30 minutes to prepare “resin particles for shell [B1] dispersion” in which resin particles for shell [B1] having a volume-based median diameter (D ₅₀ ) of 250 nm are dispersed .

(2-3) Shell resin particles [B2] to [B18] Dispersion Preparation Process In the “(2-1) Synthesis of Shell Resin [B1]”, the monomer composition was changed as shown in Table 1. Thus, “shell resins [B2] to [B18]” were synthesized. Using this shell resin, “shell resin particles [B2] to [B18] dispersions” were prepared in the same manner as “(2-2) Preparation of shell resin particles [B1] dispersion”. .

(2-4) Synthesis of Resin for Shell [B19] (Synthesis of Polyester Resin (a))
In a reaction vessel equipped with a cooling pipe, a stirrer and a nitrogen introduction pipe, 316 parts by mass of a bisphenol A propylene oxide 2-mole adduct, 80 parts by mass of terephthalic acid, 34 parts by mass of maleic anhydride, and titanium tetraisoso 2 parts by mass of propoxide was divided into 10 portions and reacted at 200 ° C. for 10 hours while distilling off the water generated under a nitrogen stream. Subsequently, the reaction was carried out under reduced pressure of 13.3 kPa (100 mmHg), and the reaction was stopped when the acid value reached 20 KOH mg / mg. This is designated as polyester resin (a). The polyester resin (a) had a Tg of 58 ° C., a number average molecular weight of 4500, a weight average molecular weight of 13500, and a softening point of 104 ° C.

(Synthesis of shell resin [B19])
In an autoclave reaction vessel equipped with a thermometer and a stirrer, 430 parts by mass of xylene and the above polyester resin (a) are added and dissolved, and after substitution with nitrogen, 86 parts by mass of styrene and 21.5 parts by mass of 2-ethylhexyl acrylate A mixed solution of 40 parts by mass of di-t-butyl peroxide and 100 parts of xylene was dropped and polymerized at 170 ° C. over 3 hours, and further maintained at this temperature for 30 minutes. Next, distilled water was added and the solvent was removed to obtain “resin for shell [B19]”.

(2-5) Preparation of Resin Particle for Shell [B19] Dispersion 100 parts by mass of the resin for shell [B19] was dissolved in 400 parts by mass of ethyl acetate (manufactured by Kanto Chemical Co., Inc.) with stirring. Next, it was mixed with 401 parts by mass of a sodium lauryl sulfate solution having a concentration of 0.26% by mass prepared in advance, and ultrasonicated with an ultrasonic homogenizer “US-150T (manufactured by Nippon Seiki Seisakusho)” for 30 minutes at V-LEVEL 300 μA while stirring. After the dispersion, using a diaphragm vacuum pump “V-700 (manufactured by BUCHI)” while being heated to 50 ° C., ethyl acetate was completely removed while stirring for 5 hours under reduced pressure. A “shell resin particle [B19] dispersion” having a diameter (D ₅₀ ) of 180 nm and a solid content of 20% by mass was obtained.

(2-6) Synthesis of Shell Resin [B20] (Unmodified Polyester Resin [B20]) In “(2-1) Synthesis of Shell Resin [B1]”, acrylic acid, styrene, acrylic acid 2- A “shell resin [B20] (unmodified polyester resin [B20])” was synthesized in the same manner except that ethylhexyl was not added.

(2-7) Preparation of Shell Resin Particle [B20] Dispersion In the above-mentioned “(2-2) Preparation of Shell Resin Particle [B1] Dispersion”, the shell resin [B1] is changed to the shell resin [B20. The “resin particle for shell [B20] dispersion” was prepared in the same manner except that the above was changed.

(3) Production of Colorant Particle Dispersion (1) 90 parts by mass of sodium dodecyl sulfate was stirred and dissolved in 1600 parts by mass of ion-exchanged water. While stirring this solution, 420 parts by mass of carbon black “Mogal L (manufactured by Cabot Corp.)” was gradually added, and then dispersed using a stirrer “Claremix (manufactured by M Technique Corp.)”. A “colorant particle dispersion (1)” having dispersed colorant particles was prepared. The particle diameter of this dispersion was measured using a Microtrac particle size distribution analyzer “UPA-150 (manufactured by Nikkiso Co., Ltd.)” and found to be 117 nm.
(4) Aggregation / Fusion to External Additive Processing Step << Production of Toner >>
(4-1) Preparation of toner 1 (Aggregation / fusion process)
Into a reaction vessel equipped with a stirrer, a temperature sensor, and a cooling tube, 288 parts by mass of the “core resin particle (A) dispersion” and 2000 parts by mass of ion-exchanged water are added in an amount of 5 mol / liter. The pH was adjusted to 10 by adding aqueous sodium hydroxide.

Then, 40 parts by mass of “colorant particle dispersion (1)” was added in terms of solid content. Next, an aqueous solution in which 60 parts by mass of magnesium chloride was dissolved in 60 parts by mass of ion-exchanged water was added over 10 minutes at 30 ° C. with stirring. Thereafter, the temperature was raised after being allowed to stand for 3 minutes, and the temperature of the system was raised to 80 ° C. over 60 minutes, and the particle growth reaction was continued while maintaining 80 ° C. In this state, the particle size of the associated particles was measured with “Multisizer 3 (manufactured by Beckman Coulter)”, and when the median diameter (D ₅₀ ) on the volume basis became 6.0 μm, “resin particles for shell” [B1] Dispersion "72 parts by mass in terms of solid content was added over 30 minutes, and when the supernatant of the reaction liquid 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 grain growth. Further, the temperature is raised and the mixture is heated and stirred at 90 ° C. to promote particle fusion, and the average circularity of the toner is measured using “FPIA-2100 (manufactured by Sysmex)” (HPF detection). (The number was 4000) When the average circularity reached 0.945, it was cooled to 30 ° C. to prepare “Dispersion of toner base particle 1”.

(Washing / drying process)
The particles produced in the aggregation / fusion step (“dispersion of toner base particles 1”) were subjected to solid-liquid separation with a centrifuge to form a wet cake of toner base particles. The wet cake was washed with ion-exchanged water at 35 ° C. until the electric conductivity of the filtrate reached 5 μS / cm in the centrifuge, and then transferred to “flash jet dryer (manufactured by Seishin Enterprise Co., Ltd.)”. Drying to 0.5% by mass produced “toner base particles [1]”.

(External additive treatment process)
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 “toner base particle [1]”, and Henschel is added. “Toner 1” was prepared by mixing with a mixer.

(4-2) Preparation of Toners 2 to 20 In “(4-1) Preparation of Toner 1”, the types and amounts of “shell resin particle dispersion” and “core resin particle dispersion” are shown in Table 2. “Toners 2 to 20” were produced in the same manner except for the above changes.

  Here, toners 1 to 7, toners 10 to 12, and toners 15 to 19 are toners of the present invention, and toners 8, 9, 13, and 14 and toner 20 are comparative toners.

≪Development of developer≫
100 parts by mass of ferrite core and 5 parts by mass of copolymer resin particles of cyclohexyl methacrylate / methyl methacrylate (copolymerization ratio 5/5) are put into a high-speed mixer equipped with stirring blades and stirred and mixed at 120 ° C. for 30 minutes. Then, a resin coat layer was formed on the surface of the ferrite core by the action of mechanical impact force to obtain a carrier having a volume-based median diameter of 50 μm.

  The volume-based median diameter of the carrier was measured by a laser diffraction particle size distribution measuring apparatus “HELOS (manufactured by Sympathic)” equipped with a wet disperser.

  Toners 1 to 20 are added to the carrier so that the toner concentration is 6% by mass, and the mixture is put into a “micro-type V-type mixer (Tsujii Chemical Co., Ltd.)”. An agent was prepared.

≪Evaluation method≫
(1) Low-temperature fixing characteristics Image evaluation was performed by sequentially loading the developer prepared above into a developing device of a commercially available color multifunction peripheral “bizhub PRO C6500 (manufactured by Konica Minolta Business Technologies, Inc.)”. . In addition, modification was made so that the fixing temperature, the toner adhesion amount, and the system speed could be set freely. “NPi fine paper 128 g / m ² (manufactured by Nippon Paper Industries)” was used as an evaluation paper, and a solid image with a toner adhesion amount of 11.3 g / m ² was fixed at a fixing speed of 300 mm / sec. Was set at 20 ° C. lower than the upper belt, and the fixing lower limit temperature at which cold offset does not occur when fixing at a level of 5 ° C. was evaluated. The lower the fixing minimum temperature, the better the fixing property.

A: Fixing lower limit temperature is 150 ° C. or less (fixing property is very good)
○: Fixing lower limit temperature is 165 ° C. or less (good fixability)
X: The minimum fixing temperature is 170 ° C. or more (insufficient fixing property)
(2) Heat-resistant storage stability 0.5 g of toner was placed in a 10-ml glass bottle with an inner diameter of 21 mm, the lid was closed, and the lid was removed after shaking 600 times at room temperature with a tap denser “KYT-2000” (manufactured by Seishin Enterprise). The sample was left in an environment of 55 ° C. and 35% RH for 2 hours. Next, the toner is placed on a 48 mesh (mesh 350 m) sieve while being careful not to crush the toner agglomerates, and set in a “powder tester (manufactured by Hosokawa Micron)”. After fixing and adjusting the vibration strength to a feed width of 1 mm and applying vibration for 10 seconds, the ratio (mass%) of the amount of toner remaining on the sieve was measured. The toner aggregation rate is a value calculated by the following formula.

Toner aggregation rate (%) = residual toner mass on sieve (g) /0.5 (g) × 100
The heat resistant storage stability of the toner was evaluated according to the criteria described below.

A: The toner aggregation rate is less than 10% by mass (the toner aggregation rate is extremely low and the heat-resistant storage property is extremely good).
○: The toner aggregation rate is 10% by mass or more and less than 15% by mass (the toner aggregation rate is low and the heat resistant storage property is good).
Δ: The toner aggregation rate is 15% by mass or more and less than 20% by mass (the toner aggregation rate is high, but the allowable level)
X: Toner aggregation rate of 20% by mass or more (toner has poor heat storage stability and cannot be used)
(3) Charging stability When 20,000 sheets of black (Bk) toner single color and 1% printing area ratio are output using color complex machine “bizhub pro C6500 (manufactured by Konica Minolta Business Technologies, Inc.)” If the difference between the amount of charge and the initial charge amount before output was less than 15 μc / g, the test was accepted.

A: Charge amount difference is less than 5 μc / g ○: Charge amount difference is 5 μc / g or more and less than 10 μc / g Δ: Charge amount difference is 10 μc / g or more and less than 15 μc / g ×: Charge amount difference is 15 μc / g or more (4 ) Cover (image quality)
Using a color multifunction device “bizhub pro C6500 (manufactured by Konica Minolta Business Technologies)”, 400,000 images with a black (Bk) toner single color and a print area ratio of 5% were output. The white density of the image support was measured at 20 locations of A4 size, the average value was determined as the density of the white paper, and then the absolute image density at 20 locations was similarly measured for the white background portion of the 400,000th image of the formed image. A value obtained by subtracting the white paper density from the average density was evaluated as the fog density. If the fog density was 0.006 or less, the fog was accepted.

  Density measurement was performed using a reflection densitometer “RD-918 (manufactured by Macbeth)”.

A: Less than 0.003 (fogging is extremely small and good)
○: 0.003 to less than 0.006 (small fog and good)
Δ: 0.006 to 0.010 or less (fogging is visually recognized but practically acceptable level)
X: A value greater than 0.010 (a level at which fogging is large and causes practical problems)
The above evaluation results are shown in Table 2.

  As is apparent from the results in Table 2, the toner of the present invention is generally excellent in low-temperature fixing property, heat-resistant storage property, charging stability and image characteristics (fogging) as compared with the comparative toner. I understand.

Claims (6)

A core-shell toner having a shell layer on the surface of core particles containing at least a binder resin,
The shell layer contains a styrene-acrylic modified polyester resin;
The acid value of the styrene-acrylic modified polyester resin is 10 KOHmg / g or more and 40 KOHmg / g or less,
A toner for developing an electrostatic charge image, wherein the acrylic component constituting the styrene-acrylic modified polyester resin is derived from a polymerizable monomer represented by the following general formula (1).
General formula (1)
CH ₂ = _CR 1 -COOR ₂
(In the formula, R ₁ and R ₂ may be the same or different and each represents a hydrogen atom or an alkyl group having 1 to 12 carbon atoms which may have a substituent.)   2. The electrostatic image developing toner according to claim 1, wherein a content ratio of the styrene-acrylic polymer segment in the styrene-acrylic modified polyester resin is 5% by mass or more and 30% by mass or less.   The content ratio of the aliphatic unsaturated dicarboxylic acid component in the polyvalent carboxylic acid component for constituting the polyester segment in the styrene-acryl-modified polyester resin is 25 mol% or more and 75 mol% or less. The toner for developing an electrostatic charge image according to claim 1 or 2. The electrostatic image developing toner according to claim 3, wherein the aliphatic unsaturated dicarboxylic acid is represented by the following general formula (2) or an acid anhydride thereof.
General formula (2)
HOOC- (CR ₃ = CR ₄ ) _n -COOH
(In the formula, R ₃ and R ₄ 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.) The styrene-acrylic modified polyester resin comprises an aromatic vinyl monomer and a (meth) acrylic acid ester monomer for forming the styrene-acrylic polymer segment of the styrene-acrylic modified polyester resin,
An unmodified polyester resin having a polymerizable unsaturated group and a group capable of reacting with a polyvalent carboxylic acid monomer or a polyhydric alcohol monomer for forming a polyester segment of the styrene-acryl-modified polyester resin The electrostatic image developing toner according to claim 1, wherein the toner is obtained by polymerizing in the presence of the toner. A method for producing the electrostatic image developing toner according to claim 1,
At least a step of preparing an aqueous dispersion of binder resin particles, a step of preparing an aqueous dispersion of colorant particles,
A step of mixing the aqueous dispersion of the binder resin particles and the aqueous dispersion of the colorant particles to prepare a mixed solution;
Adding an aggregating agent to the mixed solution to agglomerate the binder resin particles and the colorant particles to form core particles;
An electrostatic charge image developing toner comprising a step of adding an aqueous dispersion of styrene-acryl-modified polyester resin particles to an aqueous dispersion of the core particles to form a shell layer on the surface of the core particles. Production method.