JP6107464B2 - Toner for electrostatic image development - Google Patents

Description

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

Conventionally, in an electrophotographic image forming method, as a method of fixing a toner image formed by an electrostatic charge image developing toner (hereinafter also simply referred to as “toner”) on a recording material such as paper, for example, A heat roller fixing system in which a recording material on which a toner image is formed is fixed by passing between a heating roller and a pressure roller is widely used. In order to secure the fixability in the fixing method of this heat roller fixing method, that is, the adhesion of the toner to the recording material, the heating roller is required to have a certain amount of heat.
However, in recent years, due to a request for prevention of global warming in the global environment, image forming apparatuses adopting a heat roller fixing method are also required to save energy. A technique for reducing the amount of heat required for fixing has been studied.

  For example, a technique for improving low-temperature fixability of toner by using a combination of a crystalline resin and an amorphous resin as a binder resin has been proposed (Patent Document 1). Further, it has been proposed to improve low-temperature fixability by using a crystalline polyester resin as a binder resin (Patent Document 2). Further, a toner using a cross-linked crystalline polyester resin as a binder resin (Patent Document 3), or a crystalline polyester resin having a double bond derived from an unsaturated carboxylic acid introduced, A toner produced by including an emulsion polymerization step (Patent Document 4) has been proposed.

However, the toner disclosed in Patent Document 1 cannot provide sufficient low-temperature fixability. In addition, although the toner disclosed in Patent Document 2 can advantageously obtain low-temperature fixability, high-temperature offset occurs due to low elasticity at high temperatures. Further, in the toner disclosed in Patent Document 3, although high-temperature offset resistance is obtained, charging stability is low because the crystalline polyester resin is exposed on the surface of the toner particles. In addition, in the toner disclosed in Patent Document 4, it cannot be said that the bond between the vinyl resin and the crystalline polyester resin is sufficiently formed, and both the low temperature fixability and the high temperature offset resistance can be satisfactorily achieved. Not.
As described above, it has been difficult to obtain further charging stability while simultaneously obtaining low-temperature fixability, heat-resistant storage stability and high-temperature offset resistance.

Japanese Unexamined Patent Publication No. 2011-145587 Japanese Patent Laid-Open No. 2004-177496 JP 2001-117268 A JP 2011-118362 A

  The present invention has been made in consideration of the above circumstances, and its purpose is to provide an electrostatic charge that can be obtained at the same time with low-temperature fixability, heat-resistant storage stability, high-temperature offset resistance and charge stability. The object is to provide a toner for image development.

The electrostatic image developing toner of the present invention comprises a core-shell comprising a core particle made of a crystalline resin formed by bonding a vinyl polymer segment and a polyester polymer segment, and a shell layer made of a vinyl resin covering the core particle. Consisting of toner particles of structure,
The content ratio of the crystalline resin constituting the core particle in the total amount of the resin constituting the core particle is 70 to 100% by mass,
The content ratio of the vinyl polymerization segment in the crystalline resin constituting the core particle is 5 to 30% by mass,
The vinyl resin constituting the shell layer is a polymerization reaction product of a polymerizable monomer having at least an acid group.

  It is preferable that the vinyl polymerization segment in the crystalline resin constituting the core particle and the vinyl resin constituting the shell layer are each made of a styrene-acrylic copolymer.

It is preferable that the styrene-acrylic copolymer constituting the vinyl polymerization segment in the crystalline resin has a structural unit derived from a (meth) acrylic acid ester monomer represented by the following general formula (1).
Formula _{(1): H 2 C =} CR 1 -COOR 2
[Wherein, R ¹ represents a hydrogen atom or a methyl group, and R ² represents an alkyl group having 1 to 8 carbon atoms. ]

  It is preferable that the styrene-acrylic copolymer constituting the vinyl resin has a structural unit derived from the (meth) acrylic acid ester monomer represented by the general formula (1).

In the toner for developing an electrostatic charge image of the present invention, the core particle is in a matrix phase composed of a crystalline resin formed by bonding a vinyl polymer segment and a polyester polymer segment . It is preferably a domain-matrix structure in which the vinyl polymer segment is not dispersed as a domain phase.

  According to the toner for developing an electrostatic charge image of the present invention, a core particle composed of a crystalline resin formed by combining a vinyl polymer segment and a polyester polymer segment, and a shell layer made of a vinyl resin covering the core particle. -Since it is composed of toner particles having a shell structure, it is possible to obtain both low-temperature fixability, heat-resistant storage stability, high-temperature offset resistance and charging stability.

  Hereinafter, the present invention will be specifically described.

The toner of the present invention comprises a core particle made of a crystalline resin formed by bonding a vinyl polymer segment and a crystalline polyester polymer segment (hereinafter also referred to as “vinyl-modified crystal polyester resin”), and the core particle is coated. And core-shell toner particles composed of a vinyl resin shell layer.
Specifically, the content of the vinyl-modified crystalline polyester resin constituting the core particle is 70 to 100% by mass in the total amount of the resin constituting the core particle, and the vinyl-polymerized segment is contained in the vinyl-modified crystalline polyester resin. The ratio is 5 to 30% by mass, and the vinyl resin constituting the shell layer is synthesized from a polymerizable monomer having at least an acid group.

According to the toner as described above, the toner particles having a core-shell structure composed of core particles made of a vinyl-modified crystalline polyester resin and a shell layer made of a vinyl resin covering the core particles have low temperature fixability. , Heat resistant storage stability, high temperature offset resistance and charging stability can be achieved at the same time.
The reason is considered as follows. That is, since the core particles are made of a vinyl-modified crystalline polyester resin, excellent low-temperature fixability is obtained by the polyester polymerized segment of the vinyl-modified crystallized polyester resin, and the elasticity exhibited when the vinyl polymerized segment is thermally fixed. High temperature offset resistance is obtained. In addition, since the shell layer is made of a vinyl resin, excellent charging stability is obtained, and heat-resistant storage stability is obtained because it is incompatible with the core particles during storage of the toner. Furthermore, since the affinity of the vinyl resin constituting the shell layer to the vinyl-modified crystalline polyester resin constituting the core particle is high, the adhesion of the shell layer to the core particle is high, and as a result, the above-described charging stability and A heat-resistant storage property can be obtained over a long period of time.

[Core particles]
The core particles constituting the toner particles according to the present invention contain a vinyl-modified crystalline polyester resin, and may contain other resins.

[Vinyl modified crystalline polyester resin]
The vinyl-modified crystalline polyester resin constituting the core particle has a content ratio of 70 to 100% by mass, preferably 80 to 95% by mass in the total amount of the resin constituting the core particle.
When the content of the vinyl-modified crystalline polyester resin is 70% by mass or more, sufficient low-temperature fixability can be obtained.

  The vinyl-modified crystalline polyester resin is a crystalline resin formed by bonding a vinyl polymerization segment and a polyester polymerization segment.

  In the present invention, the crystalline resin refers to a resin having a clear endothermic peak rather than a stepwise change in endothermic amount in differential scanning calorimetry (DSC). The clear endothermic peak specifically means a peak in which the half-value width of the endothermic peak is within 15 ° C. when measured at a rate of temperature increase of 10 ° C./min in differential scanning calorimetry (DSC). To do.

[Melting point of vinyl-modified crystalline polyester resin]
The melting point of the vinyl-modified crystalline polyester resin is preferably 60 to 90 ° C, more preferably 65 to 85 ° C.
When the melting point of the vinyl-modified crystalline polyester resin is in the above range, sufficient low-temperature fixability and excellent heat-resistant storage properties can be reliably obtained.

  Here, the melting point of the vinyl-modified crystalline polyester resin is specifically raised from 0 ° C. to 200 ° C. at a raising / lowering rate of 10 ° C./min using a differential scanning calorimeter “Diamond DSC” (manufactured by Perkin Elmer). A first temperature raising process, a cooling process for cooling from 200 ° C. to 0 ° C. at a cooling rate of 10 ° C./min, and a second temperature raising process for raising the temperature from 0 ° C. to 200 ° C. at a raising / lowering speed of 10 ° C./min in this order. Based on the DSC curve obtained by this measurement, the endothermic peak top temperature derived from the vinyl-modified crystalline polyester resin in the first temperature raising process, The melting point. As a measurement procedure, 3.0 mg of vinyl-modified crystalline polyester resin is sealed in an aluminum pan and set in a sample holder of “Diamond DSC”. The reference used an empty aluminum pan.

[Vinyl polymer segment]
The vinyl polymer segment is formed of a monomer having a vinyl group (hereinafter referred to as “vinyl monomer”), and includes, for example, a styrene polymer, an acrylic polymer, a styrene-acrylic copolymer, and the like. From the viewpoint that elasticity can be easily obtained at the time of heat fixing, a styrene-acrylic copolymer is preferable.
The vinyl monomer illustrated below can be used individually by 1 type or in combination of 2 or more types.

  Examples of the 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-dimethyl To styrene monomers such as styrene and 3,4-dichlorostyrene, methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, hexyl acrylate, cyclohexyl acrylate, and acrylic acid Butyl, phenyl acrylate, methyl methacrylate, ethyl methacrylate , Propyl methacrylate, butyl methacrylate, hexyl methacrylate, cyclohexyl methacrylate, 2-ethylhexyl methacrylate, heptyl methacrylate, ethyl β-hydroxyacrylate, propyl γ-aminoacrylate, stearyl methacrylate, dimethyl methacrylate And (meth) acrylic acid ester monomers such as aminoethyl and diethylaminoethyl methacrylate.

In the case where the vinyl polymer segment is made of a styrene-acrylic copolymer, in order to ensure high temperature offset resistance, in particular, a (meth) acrylic acid ester represented by the following general formula (1) as a vinyl monomer It is preferably formed using a body.
Formula _{(1): H 2 C =} CR 1 -COOR 2

In the general formula (1), R ¹ represents a hydrogen atom or a methyl group, and R ² represents an alkyl group having 1 to 8 carbon atoms.

  Examples of the (meth) acrylic acid ester monomer represented by the general formula (1) include methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, hexyl acrylate, acrylic acid Examples include cyclohexyl, heptyl acrylate, methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate, hexyl methacrylate, cyclohexyl methacrylate, heptyl methacrylate, and 2-ethylhexyl methacrylate.

Moreover, as a vinyl monomer, the following can also be used.
・ Vinyl esters Vinyl propionate, vinyl acetate, vinyl benzoate, etc.
・ Vinyl ethers Vinyl methyl ether, vinyl ethyl ether, etc.
・ Vinyl ketones Vinyl methyl ketone, vinyl ethyl ketone, vinyl hexyl ketone, etc.
N-vinyl compounds N-vinyl carbazole, N-vinyl indole, N-vinyl pyrrolidone and the like.
・ Others Vinyl compounds such as vinyl naphthalene and vinyl pyridine, acrylic acid or methacrylic acid derivatives such as acrylonitrile, methacrylonitrile and acrylamide.

Moreover, it is preferable to use the polymerizable monomer which has an acid group as a vinyl monomer. The polymerizable monomer having an acid group refers to a monomer having an ionic dissociation group such as a carboxy group, a sulfonic acid group, and a phosphoric acid group. Specifically, there are the following.
Examples of the monomer having a carboxy group include acrylic acid, methacrylic acid, maleic acid, itaconic acid, cinnamic acid, fumaric acid, maleic acid monoalkyl ester, itaconic acid monoalkyl ester, and the like. Examples of the monomer having a sulfonic acid group include styrene sulfonic acid, allyl sulfosuccinic acid, 2-acrylamido-2-methylpropane sulfonic acid, and the like. Furthermore, examples of the monomer having a phosphate group include acid phosphooxyethyl methacrylate.

  Furthermore, polyfunctional vinyls can be used as the vinyl monomer, and the vinyl polymer can have a crosslinked structure. Polyfunctional vinyls include divinylbenzene, ethylene glycol dimethacrylate, ethylene glycol diacrylate, diethylene glycol dimethacrylate, diethylene glycol diacrylate, triethylene glycol dimethacrylate, triethylene glycol diacrylate, neopentyl glycol dimethacrylate, neopentyl glycol Examples include diacrylate.

[Polyester polymerization segment]
The polyester polymerized segment is a crystalline one formed by a polyvalent carboxylic acid containing two or more carboxy groups in one molecule and a polyhydric alcohol containing two or more hydroxyl groups in one molecule. In the differential scanning calorimetry (DSC), it means a sample having a clear endothermic peak, not a stepwise endothermic amount change.

As the polyvalent carboxylic acid, an aliphatic dicarboxylic acid is preferably used, and an aromatic dicarboxylic acid may be used in combination.
The polyvalent carboxylic acid preferably has 4 to 12 carbon atoms in the main chain including the carboxy group, particularly preferably 6 to 6 carbon atoms in the main chain, from the viewpoint of obtaining excellent crystallinity in the polyester polymerized segment. It is preferable to use a linear aliphatic dicarboxylic acid of 10.
A polyvalent carboxylic acid may be used individually by 1 type, and may be used in combination of 2 or more type.

  Examples of the aliphatic dicarboxylic acid include saturated aliphatic dicarboxylic acids such as oxalic acid, malonic acid, succinic acid, adipic acid, azelaic acid, sebacic acid, and n-dodecyl succinic acid; and alicyclic dicarboxylic acids such as cyclohexanedicarboxylic acid Aromatic dicarboxylic acids such as phthalic acid, isophthalic acid and terephthalic acid; trimellitic acid; trivalent or higher polyvalent carboxylic acids such as pyromellitic acid; and their anhydrides or alkyl esters having 1 to 3 carbon atoms Is mentioned.

As the polyhydric alcohol, an aliphatic diol is preferably used, and a diol other than the aliphatic diol may be used in combination as necessary.
As the polyhydric alcohol, it is preferable to use a linear aliphatic diol having 2 to 15 carbon atoms in the main chain among the aliphatic diols from the viewpoint of obtaining excellent crystallinity in the polyester polymerized segment. In particular, it is preferable to use an aliphatic diol having 2 to 10 carbon atoms in the main chain.
A polyhydric alcohol may be used individually by 1 type, and may be used in combination of 2 or more type.

  Examples of the aliphatic diol include 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, Aliphatic diols such as 1,8-octanediol, neopentyl glycol and 2-butene-1,4-diol: trihydric or higher polyhydric alcohols such as glycerin, pentaerythritol, trimethylolpropane and sorbitol.

[Ester group concentration of vinyl-modified crystalline polyester resin]
The ester group concentration of the vinyl-modified crystalline polyester resin is preferably from 0.1 mmol / g to 7.5 mmol / g.
When the ester group concentration of the vinyl-modified crystalline polyester resin is in the above range, the phase separation from the vinyl resin constituting the shell layer is sufficiently obtained, and toner particles having a core-shell structure are reliably obtained. be able to.

Here, the ester group concentration is a ratio of ester groups (ester bonds) in the vinyl-modified crystalline polyester resin, and indicates the degree of affinity for water. The larger the value, the higher the affinity for water. Is.
In the present invention, the ester group concentration is a value calculated by the following formula (2).
Formula (2): Ester group concentration = [average of the number of moles of a moiety that can be an ester group contained in the polyvalent carboxylic acid and polyhydric alcohol forming the vinyl-modified crystalline polyester resin / ((polyvalent carboxylic acid and polyvalent Total molecular weight of alcohol)-(molecular weight of water separated by dehydration polycondensation × number of moles of ester group))] × 1000
The ester group concentration of the vinyl-modified crystalline polyester resin can be controlled by selecting the monomer species to be used.

An example of calculating the ester group concentration of the vinyl-modified crystalline polyester resin is shown below.
A vinyl-modified crystalline polyester resin obtained by a polyvalent carboxylic acid represented by the following formula (a) and a polyhydric alcohol represented by the following formula (b) is represented by the following formula (c).
Formula ^{(a): HOOC-R 3} -COOH
Formula (b): HO—R ⁴ —OH
Formula (c): — (— OCO—R ³ —COO—R ⁴ —) _n —
“Average of the number of moles of a moiety capable of forming an ester group contained in a polyvalent carboxylic acid and a polyhydric alcohol that forms a vinyl-modified crystalline polyester resin” means that the carboxyl of the polyvalent carboxylic acid that forms the vinyl-modified crystalline polyester resin Is the average of the number of moles of the group and the number of moles of the hydroxyl group of the polyhydric alcohol, specifically, the number of moles of the carboxy group of the polyvalent carboxylic acid of the formula (a) “2” and the number of moles of the formula (b) The average is “2” with the number of moles of hydroxyl groups of the hydric alcohol “2”.
When the molecular weight of the polyvalent carboxylic acid of the formula (a) is m1, the molecular weight of the polyhydric alcohol of the formula (b) is m2, and the molecular weight of the vinyl-modified crystalline polyester resin of the formula (c) is m3, “(multiple (Molecular weight of polyvalent carboxylic acid and polyhydric alcohol)-(molecular weight of water separated by dehydration polycondensation × number of moles of ester group) ”is (m1 + m2) − (18 × average number of moles of ester group“ 2 Therefore, the molecular weight of the vinyl-modified crystalline polyester resin of the formula (c) is “m3”.
From the above, the ester group concentration of the vinyl-modified crystalline polyester resin represented by the formula (c) is “2 / m 3”.
In addition, when two or more polycarboxylic acids or two or more polyhydric alcohols are used in combination, the average of the carboxy group and molecular weight of each polycarboxylic acid and the average of the hydroxyl group and molecular weight of the polyhydric alcohol Become.

In the present invention, the content of the vinyl polymerized segment in the vinyl-modified crystalline polyester resin is 5 to 30% by mass, preferably 10 to 25% by mass.
Specifically, the content ratio of the vinyl polymerized segment is the total mass of the resin material used for synthesizing the vinyl-modified crystalline polyester resin, that is, the polyvalent carboxylic acid and polyhydric alcohol serving as the polyester polymerized segment, and vinyl. It is the ratio of the mass of the vinyl monomer to the total mass of the total of the vinyl monomer that becomes the polymerization segment and the both reactive monomers for bonding them.
When the content ratio of the vinyl polymer segment is 5% by mass or more, a highly elastic component can be sufficiently obtained at the time of heat fixing, and excellent high temperature offset resistance can be surely obtained. Moreover, the adhesiveness between the core particles and the shell layer can be improved, and charging stability and charging stability can be obtained over a long period of time. On the other hand, when the content is 30% by mass or less, the amount of the polyester polymerization segment contributing to the low-temperature fixability can be ensured, and sufficient low-temperature fixability can be surely obtained.

[Molecular weight of vinyl-modified crystalline polyester resin]
The weight average molecular weight (Mw) calculated from the molecular weight distribution measured by gel permeation chromatography (GPC) of the vinyl-modified crystalline polyester resin is preferably 5,000 to 50,000.
When the vinyl-modified crystalline polyester resin has a weight average molecular weight (Mw) of 5,000 or more, a high elastic component can be sufficiently obtained at the time of heat fixing, and excellent high temperature offset resistance can be surely obtained. On the other hand, when the weight average molecular weight (Mw) is 50,000 or less, the amount of the polyester polymer segment contributing to the low-temperature fixability can be ensured, and sufficient low-temperature fixability can be surely obtained.

Measurement of molecular weight distribution by GPC was performed as follows. That is, using an apparatus “HLC-8220” (manufactured by Tosoh Corporation) and a column “TSKguardcolumn + TSKgelSuperHZM-M3 series” (manufactured by Tosoh Corporation), while maintaining the column temperature at 40 ° C., tetrahydrofuran (THF) was used as a carrier solvent at a flow rate of 0. Flow at 2 ml / min, and dissolve the measurement sample (vinyl-modified crystalline polyester resin) in tetrahydrofuran to a concentration of 1 mg / ml under a dissolution condition in which treatment is performed for 5 minutes using an ultrasonic disperser at room temperature. A sample solution is obtained by processing with a 0.2 μm membrane filter, and 10 μL of this sample solution is injected into the apparatus together with the carrier solvent described above, detected using a refractive index detector (RI detector), and possessed by the measurement sample. Molecular weight distribution using monodisperse polystyrene standard particles Calculate using the measured calibration curve. As a standard polystyrene sample for calibration curve measurement, molecular weights manufactured by Pressure Chemical Co., Ltd. are 6 × 10 ² , 2.1 × 10 ³ , 4 × 10 ³ , 1.75 × 10 ⁴ , 5.1 × 10 ⁴ , 1 .1 × 10 ⁵ , 3.9 × 10 ⁵ , 8.6 × 10 ⁵ , 2 × 10 ⁶ , 4.48 × 10 ⁶ , and at least about 10 standard polystyrene samples were measured, and a calibration curve It was created. A refractive index detector was used as the detector.

[Glass transition point of vinyl-modified crystalline polyester resin]
The glass transition point of the vinyl-modified crystalline polyester resin is preferably 30 to 70 ° C, more preferably 35 to 60 ° C.
When the glass transition point is in the above range, sufficient low-temperature fixability can be obtained.

The glass transition point (Tg) of the vinyl-modified crystalline polyester resin is a value measured using “Diamond DSC” (manufactured by PerkinElmer).
As a measurement procedure, 3.0 mg of a measurement sample (vinyl-modified crystalline polyester resin) is sealed in an aluminum pan and set in a holder. The reference used an empty aluminum pan. The measurement conditions were a measurement temperature of 0 ° C. to 200 ° C., a temperature increase rate of 10 ° C./min, a temperature decrease rate of 10 ° C./min, and heat-cool-heat temperature control. Perform analysis based on the data in Heat, draw a baseline extension before the rise of the first endothermic peak, and a tangent line indicating the maximum slope between the rise of the first peak and the peak apex, Let the intersection be the glass transition point.

[Method for producing vinyl-modified crystalline polyester resin]
The vinyl-modified crystalline polyester resin can be produced by bonding a polyester polymer segment and a vinyl polymer segment via both reactive monomers. Specifically, it can be produced by performing a polycondensation reaction in the presence of a polyvalent carboxylic acid and a polyhydric alcohol at least at any time before, during and after the step of addition polymerization of a vinyl monomer. it can.
Specifically, an existing general scheme can be used. The following three methods are listed as typical methods.
(1) After performing an addition polymerization reaction of a vinyl monomer to form a vinyl polymerization segment, a polycondensation reaction of a polyvalent carboxylic acid and a polyhydric alcohol to form a polyester polymerization segment is performed. A method in which a tri- or higher valent vinyl monomer serving as a crosslinking agent is added to the reaction system to further advance the condensation polymerization reaction.
(2) After the polycondensation reaction of polyvalent carboxylic acid and polyhydric alcohol to form a polyester polymer segment, an addition polymerization reaction of a vinyl monomer to form a vinyl polymer segment is performed, and then necessary According to the method, a trivalent or higher valent vinyl monomer serving as a cross-linking agent is added to the reaction system, and the polycondensation reaction further proceeds under temperature conditions suitable for the polycondensation reaction.
(3) An addition polymerization reaction of a vinyl monomer for forming a vinyl polymerization segment and a polyvalent carboxylic acid and a polyhydric alcohol for forming a polyester polymerization segment under temperature conditions suitable for the addition polymerization reaction. After the polycondensation reaction is carried out in parallel and the addition polymerization reaction is completed, a trivalent or higher valent vinyl monomer as a cross-linking agent is added to the reaction system as necessary, under temperature conditions suitable for the polycondensation reaction. A method of further proceeding the condensation polymerization reaction.

  Both reactive monomers are added together with polyvalent carboxylic acid / polyhydric alcohol and / or vinyl monomer.

Both reactive monomers have at least one functional group selected from the group consisting of a hydroxyl group, a carboxy group, an epoxy group, a primary amino group and a secondary amino group in the molecule, preferably a hydroxyl group and / or a carboxy group. It is preferably a compound having a group, more preferably a carboxy group and an ethylenically unsaturated bond, that is, a vinyl carboxylic acid. Specific examples of the both reactive monomers include, for example, acrylic acid, methacrylic acid, fumaric acid, maleic acid and the like, and these hydroxyalkyl (C1-3) esters may be used. From this viewpoint, it is preferable to use acrylic acid, methacrylic acid and fumaric acid.
In addition, it is preferable to use a monovalent vinyl carboxylic acid as a bi-reactive monomer rather than a polyvalent vinyl carboxylic acid from the viewpoint of toner durability. This is probably because the reactivity between the monovalent vinyl-based carboxylic acid and the vinyl monomer is high, so that it can be easily hybridized. On the other hand, when a dicarboxylic acid such as fumaric acid is used as the bireactive monomer, the durability of the toner is slightly inferior. This is presumably because the reactivity between the dicarboxylic acid and the vinyl monomer is low and it is difficult to form a uniform hybrid, so that it takes a domain structure.

  The amount of the both reactive monomers used is preferably 1 to 10 parts by mass with respect to 100 parts by mass of the total amount of vinyl monomers from the viewpoint of improving the low temperature fixability, high temperature offset resistance and durability of the toner. -8 parts by mass is more preferable, 0.3-8 parts by mass is preferable, and 0.5-5 parts by mass is more preferable with respect to 100 parts by mass of the total amount of the polyvalent carboxylic acid and the polyhydric alcohol.

  The addition polymerization reaction can be performed by a conventional method in the presence of a radical polymerization initiator, a crosslinking agent, or the like, in an organic solvent or in the absence of a solvent, but the temperature condition is preferably 110 to 200 ° C., and 140 to 180. ° C is more preferred. Examples of the radical polymerization initiator include dialkyl peroxide, dibutyl peroxide, butyl peroxy-2-ethylhexyl monocarboxylic acid and the like, and these can be used alone or in combination of two or more.

  The condensation polymerization reaction can be performed, for example, in an inert gas atmosphere at a temperature of 180 to 250 ° C., but is preferably performed in the presence of an esterification catalyst, a polymerization inhibitor, or the like. Examples of the esterification catalyst include tin (II) compounds having no Sn—C bond, such as dibutyltin oxide, titanium compounds, and tin octylate, and these may be used alone or in combination. it can.

[Shell layer]
The shell layer constituting the toner particles according to the present invention contains a vinyl resin and may contain other resins.
This shell layer preferably has a structure in which the core particles are completely covered. By having such a structure, heat-resistant storage property can be obtained reliably.
The vinyl resin constituting the shell layer has low compatibility with the vinyl-modified crystalline polyester resin constituting the core particles in the temperature range during storage of the toner.

  The vinyl resin is formed using a vinyl monomer, and examples of the vinyl resin include styrene-acrylic copolymers, styrene polymers, and those made of acrylic polymers. It is preferable to use a combination.

As the vinyl monomer, it is necessary to use at least a polymerizable monomer having an acid group. In addition, the vinyl monomer is exemplified as a vinyl monomer for forming the vinyl polymerization segment of the above-described vinyl-modified crystalline polyester resin. Things can be used.
Since the vinyl resin is formed by using at least a polymerizable monomer having an acid group, a thin and highly uniform shell layer can be formed. Stability is obtained.

  As the polymerizable monomer having an acid group, those exemplified as the monomer having an ionic dissociation group can be used, and acrylic acid, methacrylic acid, and fumaric acid can also be used. As the polymerizable monomer having an acid group, those having a carboxy group such as acrylic acid, methacrylic acid, fumaric acid and maleic acid are particularly preferable, and acrylic acid and methacrylic acid are more preferable.

Content ratio of structural units derived from a polymerizable monomer having an acid group in the vinyl resin, that is, a polymerizable single amount having an acid group with respect to the total mass of the vinyl monomer used to form the vinyl resin The mass ratio of the body (hereinafter also referred to as “acid group amount”) is preferably 1 to 20 mass%, more preferably 5 to 15 mass%.
In particular, the amount of acid groups in the vinyl resin constituting the shell layer is preferably larger than the amount of acid groups in the vinyl polymerization segment of the vinyl-modified crystalline polyester resin constituting the core particles. When the amount of acid groups related to the shell layer is small, there is a possibility that a highly uniform shell layer cannot be formed.

When the vinyl polymer segment of the vinyl-modified crystalline polyester resin constituting the core particle contains a structural unit derived from the (meth) acrylate monomer represented by the general formula (1), the shell layer It is preferable to use the (meth) acrylic acid ester monomer represented by the above general formula (1) as the vinyl monomer for forming the vinyl resin constituting the resin, and in particular, the same (meth) acrylic It is preferable to use an acid ester monomer.
Each of the vinyl-modified crystalline polyester resin constituting the core particle and the vinyl resin constituting the shell layer has structural units derived from the (meth) acrylate monomer represented by the general formula (1). By being contained, it is possible to form toner particles having higher adhesion between the core particles and the shell layer.

  The above vinyl monomers can be used alone or in combination of two or more.

[Glass transition point of vinyl resin]
The glass transition point of the vinyl resin is preferably 50 to 65 ° C.
When the glass transition point is in the above range, sufficient low-temperature fixability can be obtained while ensuring heat-resistant storage stability.

  The glass transition point of the vinyl resin is a value measured in the same manner as described above except that a vinyl resin is used as a measurement sample.

[Molecular weight of vinyl resin]
The weight average molecular weight (Mw) calculated from the molecular weight distribution measured by GPC of the vinyl resin is preferably 5,000 to 50,000, more preferably 7,500 to 20,000.

  When the weight average molecular weight (Mw) of the vinyl resin is 5,000 or more, there is no compatibility between the vinyl resin and the vinyl-modified crystalline polyester resin constituting the core particle, and sufficient heat-resistant storage stability is ensured. Is obtained. Further, when the weight average molecular weight (Mw) of the vinyl resin is 50,000 or less, sufficient low-temperature fixability can be obtained.

  The molecular weight distribution measurement of the vinyl resin by GPC is performed in the same manner as described above except that the vinyl resin is used as a measurement sample.

[Ratio of core particle to shell layer in toner particles]
The mass ratio of the core particles to the shell layer (core particles: shell layer) in the toner particles according to the present invention is preferably in the range of 95: 5 to 75:25.
When the mass ratio of the core particles in the toner particles is 95% by mass or less, toner particles having a structure in which the core particles are completely covered with the shell layer can be obtained. As a result, excellent heat resistant storage stability and charging stability can be sufficiently obtained. On the other hand, when the mass ratio of the core particles in the toner particles is 75% by mass or more, the low temperature fixability by the vinyl-modified crystalline polyester resin constituting the core particles can be sufficiently obtained.

  The molecular weight distribution for each resin, the glass transition point of the vinyl resin, and the melting point of the vinyl-modified crystalline polyester resin should be measured using the vinyl resin extracted from the toner particles and the vinyl-modified crystalline polyester resin as measurement samples, respectively. Can do.

The ester group concentration of the vinyl-modified crystalline polyester resin is derived from the carbon at the alkyl site by ¹² C-NMR (nuclear magnetic resonance) measurement using, for example, deuterated chloroform from the vinyl-modified crystalline polyester resin extracted from the toner particles. From the hydrogen atom peak and the hydrogen atom peak derived from the carbon adjacent to the ester group, the monomer species and composition ratio can be specified and calculated according to the above.

[Extraction method of each resin]
As a method of extracting each resin from the toner particles, a method of separating using an appropriate solvent can be used.
Specifically, first, the toner is immersed in methyl ethyl ketone (MEK) at room temperature. At this time, since only the vinyl resin constituting the toner particles is dissolved in MEK, the vinyl resin is obtained from the supernatant liquid separated by centrifugation after dissolution. On the other hand, the solid content after centrifugation is similarly immersed in MEK and heated to near the boiling point. At this time, the vinyl-modified crystalline polyester resin is uniformly dissolved. Thereafter, only the vinyl-modified crystalline polyester resin can be precipitated by cooling. At this time, when the vinyl resin is present in the core particle of the toner particle, it remains dissolved in MEK, so that the vinyl resin present in the core particle is obtained from the supernatant.
Next, the solution in which the vinyl-modified crystalline polyester resin is precipitated is centrifuged, and the solid content after centrifugation is heated at 65 ° C. for 60 minutes and dissolved in tetrahydrofuran (THF). By filtration, a vinyl-modified crystalline polyester resin is obtained from the filtrate. In addition, since vinyl modified crystalline polyester resin will precipitate when temperature falls during filtration by the said operation, it operates in the state kept warm.

[Configuration of toner particles]
The toner particles according to the present invention contain internal additives such as a colorant, a release agent, and a charge control agent in addition to the resin (binder resin) constituting the core particles and the shell layer. May be.
The colorant, the release agent, and the charge control agent may each be contained in the core particle, may be contained in the shell layer, or may be contained in both. Is preferably contained in the core particles.

[Colorant]
As the colorant, generally known dyes and pigments can be used.
As a colorant for obtaining a black toner, various known materials such as carbon black such as furnace black and channel black, magnetic materials such as magnetite and ferrite, dyes, and inorganic pigments containing nonmagnetic iron oxide are arbitrarily selected. Can be used.
As the colorant for obtaining a color toner, known ones such as dyes and organic pigments can be arbitrarily used. Specifically, examples of the organic pigment include C.I. I. Pigment Red 5, 48: 1, 53: 1, 57: 1, 81: 4, 122, 139, 144, 149, 166, 177, 178, 222, 238 269, C.I. I. Pigment Yellow 14, 17, 74, 93, 94, 138, 155, 180, 185, C.I. I. Pigment Orange 31 and 43, C.I. I. Pigment Blue 15; 3, 60, 76, and the like. Examples of the dye include C.I. I. Solvent Red 1, 49, 52, 58, 68, 11, 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, 69, 70, 93, 95 and the like.
The colorant for obtaining the toner of each color can be used singly or in combination of two or more for each color.
It is preferable that the content rate of a coloring agent is 1-10 mass parts with respect to 100 mass parts of binder resin, More preferably, it is 2-8 mass parts.

〔Release agent〕
The release agent is not particularly limited, and various known waxes can be used. For example, polyolefin waxes such as polyethylene wax and polypropylene wax, branched hydrocarbon waxes such as microcrystalline wax, and paraffins. Long-chain hydrocarbon waxes such as wax and sazol wax, dialkyl ketone waxes such as distearyl ketone, carnauba wax, montan wax, behenate behenate, trimethylolpropane tribehenate, pentaerythritol tetrabehenate, penta Ester wacks such as erythritol diacetate dibehenate, glycerin tribehenate, 1,18-octadecanediol distearate, tristearyl trimellitic acid, distearyl maleate , Ethylenediamine behenyl amide, an amide-based waxes such as trimellitic acid tristearyl amide.
The content ratio of the release agent is usually 1 to 30 parts by mass, more preferably 5 to 20 parts by mass with respect to 100 parts by mass of the binder resin. When the content ratio of the release agent is within the above range, sufficient fixing separation property can be obtained.

[Charge control agent]
Various known compounds can be used as the charge control agent.
The content ratio of the charge control agent is usually 0.1 to 5.0 parts by mass with respect to 100 parts by mass of the binder resin.

[Average toner particle size]
The average particle diameter of the toner of the present invention is preferably 3 to 9 μm, and more preferably 3 to 8 μm, for example, on a volume basis median diameter. This particle size can be controlled by the concentration of the coagulant used, the amount of organic solvent added, the fusing time, and the composition of the polymer, for example, when the emulsion polymerization aggregation method described later is employed.
When the volume-based median diameter is in the above range, the transfer efficiency is increased, the image quality of halftone is improved, and the image quality of fine lines and dots is improved.

  The volume-based median diameter of the toner particles is measured and calculated using a measuring device in which “Multisizer 3” (manufactured by Beckman Coulter) is connected to a computer system equipped with data processing software “Software V3.51”. Is. Specifically, 0.02 g of toner is added to 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). Then, ultrasonic dispersion is performed for 1 minute to prepare a toner dispersion, and this toner dispersion is placed in a beaker containing “ISOTON II” (manufactured by Beckman Coulter) in a sample stand. Pipet until the indicated concentration is 8%. Here, a reproducible measurement value can be obtained by setting the concentration range. In the measurement apparatus, the measurement particle count is 25000, the aperture diameter is 50 μm, the frequency value is calculated by dividing the measurement range of 1 to 30 μm into 256, and the volume integrated fraction is 50 % Particle diameter is defined as the volume-based median diameter.

[Average circularity of toner particles]
The toner of the present invention preferably has an average circularity of 0.930 to 1.000, more preferably 0.950 to 0, from the viewpoint of improving the transfer efficiency of the individual toner particles constituting the toner. .995.

In the present invention, the average circularity of toner particles is measured using “FPIA-2100” (manufactured by Sysmex).
Specifically, the sample (toner particles) is blended with an aqueous solution containing a surfactant, subjected to ultrasonic dispersion treatment for 1 minute to disperse, and then subjected to measurement conditions HPF by “FPIA-2100” (manufactured by Sysmex). In the (high-magnification imaging) mode, photographing is performed at an appropriate density of 3,000 to 10,000 HPF detections, and the circularity of each toner particle is calculated according to the following formula (T). Calculated by adding the degree and dividing by the total number of toner particles.
Formula (T): Circularity = (perimeter of a circle having the same projection area as the particle image) / (perimeter of the particle projection image)

[Toner Production Method]
The toner of the present invention can be produced by a kneading / pulverization method, a suspension polymerization method, an emulsion aggregation method, an emulsion polymerization aggregation method, and other various known methods, but the shell layer is uniformly formed on the surface of the core particles. It is preferable to use an emulsion aggregation method because it can be formed.
Specifically, vinyl-modified crystalline polyester resin fine particles dispersed in an aqueous medium are aggregated and fused to form aggregated particles that become core particles, and a shell layer is formed on the surface of the aggregated particles that become the core particles It is preferable to produce by an emulsion aggregation method in which toner particles are obtained by agglomerating and fusing the fine particles of vinyl resin to be fused.

  A dispersion (emulsion) in which fine particles of vinyl-modified crystalline polyester resin are dispersed in an aqueous medium can be prepared by various known emulsification methods such as a mechanical emulsification method and a phase inversion emulsification method.

When the toner particles contain a colorant, a release agent, a charge control agent, etc., when these are contained in the core particles, the fine particles of the colorant are aggregated together when forming the agglomerated particles as the core particles. When these are contained in the shell layer, they may be added and aggregated at the same timing as the vinyl resin fine particles.
In the case of producing a toner using an emulsion polymerization aggregation method, the toner is prepared by dissolving or dispersing in a monomer solution for forming a vinyl resin in advance when forming the vinyl resin fine particles. It can also be introduced into the particles.

(External additive)
The above toner particles can constitute the toner of the present invention as they are, but in order to improve fluidity, chargeability, cleaning properties, etc., a fluidizing agent that is a so-called post-treatment agent is added to the toner particles. An external additive such as a cleaning aid may be added to constitute the toner of the present invention.

As the post-treatment agent, for example, inorganic oxide fine particles composed of silica fine particles, alumina fine particles, titanium oxide fine particles, etc., inorganic stearate compound fine particles such as aluminum stearate fine particles, zinc stearate fine particles, or strontium titanate, titanium Inorganic titanic acid compound fine particles such as zinc acid are listed. These can be used individually by 1 type or in combination of 2 or more types.
These inorganic fine particles are preferably subjected to a gloss treatment with a silane coupling agent, a titanium coupling agent, a higher fatty acid, a silicone oil or the like in order to improve heat-resistant storage stability and environmental stability.

  The total amount of these various external additives added is 0.05 to 5 parts by mass, preferably 0.1 to 3 parts by mass with respect to 100 parts by mass of the toner. In addition, various external additives may be used in combination.

  According to the toner of the present invention, the toner particles of the core-shell structure comprising core particles made of vinyl-modified crystalline polyester resin and a shell layer made of vinyl resin covering the core particles, The heat storage stability, the high temperature offset resistance and the charging stability can be achieved at the same time.

(Developer)
The toner of the present invention can be used as a magnetic or non-magnetic one-component developer, but may be mixed with a carrier and used as a two-component developer.
As the carrier, for example, magnetic particles made of conventionally known materials such as metals such as iron, ferrite and magnetite, and alloys of these metals with metals such as aluminum and lead can be used. Among these, ferrite particles Is preferably used. As the carrier, a coated carrier in which the surface of magnetic particles is coated with a coating agent such as a resin, a resin-dispersed carrier in which magnetic fine powder is dispersed in a binder resin, and the like may be used.
The carrier preferably has a volume average particle diameter of 15 to 100 μm, more preferably 25 to 80 μm.

[Image forming apparatus]
The toner of the present invention can be used in a general electrophotographic image forming method. As an image forming apparatus in which such an image forming method is performed, for example, a photosensitive member that is an electrostatic latent image carrier, A charging means for applying a uniform potential to the surface of the photoconductor by corona discharge having the same polarity as that of the toner, and an electrostatic latent image by performing image exposure on the surface of the uniformly charged photoconductor based on image data. An exposure means for forming an image; a developing means for conveying the toner to the surface of the photoreceptor to visualize the electrostatic latent image to form a toner image; and passing the toner image through an intermediate transfer member as necessary. For example, a transfer unit that transfers to a recording material and a fixing unit that heat-fixes the toner image on the recording material can be used.
The toner of the present invention can be suitably used at a relatively low temperature where the fixing temperature (the surface temperature of the fixing member) is 100 to 200 ° C.

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

For example, the core particles constituting the toner particles according to the present invention have a domain-matrix structure in which a vinyl resin is dispersed as a domain phase in a matrix phase composed of the above-mentioned vinyl-modified crystalline polyester resin. Also good.
The vinyl resin constituting the domain phase is preferably made of a styrene-acrylic copolymer.
According to the toner composed of toner particles having such a configuration, the highly elastic component of the vinyl resin exhibits elasticity at the time of heat-fixing, so that a further excellent high-temperature offset resistance can be obtained.

  As a vinyl resin which comprises a domain phase, what was formed using what was illustrated as a vinyl monomer for forming the vinyl resin which comprises the above-mentioned shell layer can be used.

[Molecular weight of the vinyl resin constituting the domain phase]
The weight average molecular weight (Mw) calculated from the molecular weight distribution measured by gel permeation chromatography (GPC) of the vinyl resin constituting the domain phase is preferably 20,000 to 500,000, more preferably 100. , 350,000 to 350,000.
When the vinyl resin constituting the domain phase has a weight average molecular weight (Mw) of 20,000 or more, sufficient elasticity is obtained at the time of heat fixing, and excellent high temperature offset resistance is obtained. On the other hand, when the weight average molecular weight (Mw) is 500,000 or less, sufficient low-temperature fixability can be reliably obtained.

  The molecular weight distribution measurement by GPC of the vinyl resin constituting the domain phase is performed in the same manner as described above except that the vinyl resin constituting the domain phase is used as a measurement sample.

[Glass transition point of vinyl resin constituting the domain phase]
It is preferable that the glass transition point of the vinyl resin which comprises a domain phase is 30-70 degreeC, More preferably, it is 45-60 degreeC.
When the glass transition point is in the above range, sufficient low-temperature fixability can be obtained.

  The glass transition point of the vinyl resin constituting the domain phase is a value measured in the same manner as described above except that the vinyl resin constituting the domain phase is used as a measurement sample.

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

[Preparation example A1 of vinyl-modified crystalline polyester resin fine particle dispersion for core]
(1) Synthesis of vinyl-modified crystalline polyester resin for core: To a 10-liter four-necked flask equipped with a nitrogen introduction tube, a dehydration tube, a stirrer and a thermocouple,
Polyhydric carboxylic acid: 202 parts by mass of sebacic acid Polyhydric alcohol: 202 parts by mass of 1,12-dodecanediol was added, heated to 160 ° C. and dissolved. to this,
-Styrene 57 mass parts-N-butyl acrylate 15 mass parts-Dicumyl peroxide 4.9 mass parts-Acrylic acid 3.7 mass parts is dripped over 1 hour with a dropping funnel, 170 degreeC after dripping. And stirring for 1 hour to polymerize the vinyl monomer,
-Tin (II) 2-ethylhexanoate 2.5 mass parts-0.2 mass part of gallic acid was added, and it heated up at 210 degreeC, and reacted for 8 hours. Furthermore, by reacting at 8.3 kPa for 1 hour, a vinyl-modified crystalline polyester resin [A1] for core was obtained.
The obtained vinyl-modified crystalline polyester resin for core [A1] had a melting point (Tm) of 83 ° C. and a weight average molecular weight (Mw) of 28,000.
(2) Production of vinyl modified crystalline polyester resin fine particles for core 30 parts by mass of the obtained vinyl modified crystalline polyester resin [A1] for core was melted and left in the melted state as an emulsifying disperser “Cabitron CD1010” The product was transferred at a transfer rate of 100 parts by mass per minute. Simultaneously with the transfer of the molten vinyl-modified crystalline polyester resin [A1] for the core, 70 parts by mass of reagent ammonia water was diluted with ion-exchanged water in an aqueous solvent tank with respect to the emulsifying disperser. .37% by mass of dilute aqueous ammonia was transferred at a transfer rate of 0.1 liter per minute while being heated to 100 ° C. with a heat exchanger. Then, by operating this emulsification disperser under the conditions of a rotor rotational speed of 60 Hz and a pressure of 5 kg / cm ^2, a vinyl-modified crystalline polyester for core having a volume-based median diameter of 200 nm and a solid content of 30% by mass. A resin fine particle dispersion [A1] was prepared.

[Preparation Examples A2 to A6, B1 of Vinyl Modified Crystalline Polyester Resin Fine Particle Dispersion for Core]
In the preparation example A1 of the vinyl-modified crystalline polyester resin fine particle dispersion for core, the vinyl-modified crystalline polyester resin fine particles for core in the aqueous medium are the same except that the monomer formulation shown in Table 1 below is followed. The core-modified vinyl-modified crystalline polyester resin fine particle dispersions [A2] to [A6] and [B1] in which A2] to [A6] and [B1] are dispersed were prepared.
Table 2 shows the melting point, weight average molecular weight (Mw), and ester group concentration of the vinyl-modified crystalline polyester resin constituting each dispersion.

[Preparation Example C1 of Unmodified Crystalline Polyester Resin Fine Particle Dispersion for Core]
(1) Synthesis of unmodified crystalline polyester resin for core In a four-necked flask with a capacity of 10 liters equipped with a nitrogen introduction tube, a dehydration tube, a stirrer and a thermocouple,
Polyhydric carboxylic acid: 202 parts by mass of sebacic acid Polyhydric alcohol: 202 parts by mass of 1,12-dodecanediol was added, heated to 160 ° C. and dissolved. to this,
-Tin (II) 2-ethylhexanoate 2.5 mass parts-0.2 mass part of gallic acid was added, and it heated up at 210 degreeC, and reacted for 8 hours. Furthermore, by reacting at 8.3 kPa for 1 hour, an unmodified crystalline polyester resin for core [C1] was obtained.
The resulting core unmodified crystalline polyester resin [C1] had a melting point (Tm) of 82.8 ° C. and a weight average molecular weight (Mw) of 20,000.
(2) Preparation of Core Unmodified Crystalline Polyester Resin Fine Particles 30 parts by mass of the core unmodified crystalline polyester resin [C1] was melted and left in the melted state as an emulsifying disperser “Cabitron CD1010” The product was transferred at a transfer rate of 100 parts by mass per minute. Simultaneously with the transfer of the unmodified crystalline polyester resin for core [C1] in the molten state, 70 parts by mass of reagent ammonia water was diluted with ion-exchanged water in an aqueous solvent tank with respect to the emulsification disperser. .37% by mass of dilute aqueous ammonia was transferred at a transfer rate of 0.1 liter per minute while being heated to 100 ° C. with a heat exchanger. Then, by operating this emulsifier / disperser under the conditions of a rotor rotation speed of 60 Hz and a pressure of 5 kg / cm ² , the core-based unmodified obtained with a volume-based median diameter of 200 nm and a solid content of 30 parts by mass. A crystalline polyester resin fine particle dispersion [C1] was prepared.

[Preparation Example 1 of vinyl resin fine particle dispersion for core]
A polymerization initiator solution in which 8.0 parts by mass of potassium persulfate was dissolved in 195 parts by mass of ion-exchanged water was added to 1400 parts by mass of ion-exchanged water.
-Styrene 288 mass parts-N-butyl acrylate 92 mass parts-Methacrylic acid 25 mass parts-n-octyl mercaptan 7.5 mass parts monomer liquid mixture was dripped over 2 hours. After completion of the dropwise addition, polymerization is carried out by heating and stirring for 2 hours. After completion of the polymerization, by cooling to 28 ° C., fine particles of styrene-acrylic resin are dispersed in an aqueous medium having a solid content of 20% by mass. The core St-Ac dispersion [1] was prepared.
The styrene-acrylic resin had a weight average molecular weight (Mw) of 15,000. Moreover, the glass transition point (Tg) was 50.2 degreeC.

[Preparation Example 2 of vinyl resin fine particle dispersion for core]
A polymerization initiator solution in which 2.5 parts by mass of potassium persulfate was dissolved in 195 parts by mass of ion-exchanged water was added to 1400 parts by mass of ion-exchanged water.
-Styrene 288 mass parts-N-butyl acrylate 92 mass parts-The monomer liquid mixture which consists of methacrylic acid 25 mass parts was dripped over 2 hours. After completion of the dropwise addition, polymerization is carried out by heating and stirring for 2 hours. After completion of the polymerization, by cooling to 28 ° C., fine particles of styrene-acrylic resin are dispersed in an aqueous medium having a solid content of 20% by mass. The core St-Ac dispersion [2] was prepared.
The styrene-acrylic resin had a weight average molecular weight (Mw) of 250,000. The glass transition point (Tg) was 53.0 ° C.

[Preparation Example 1 of Vinyl Resin Fine Particle Dispersion for Shell]
A polymerization initiator solution prepared by dissolving 8.5 parts by mass of potassium persulfate in 200 parts by mass of ion-exchanged water was added to 1390 parts by mass of ion-exchanged water.
-Styrene 280 mass parts-N-butyl acrylate 90 mass parts-Methacrylic acid 50 mass parts-N-octyl mercaptan 8.2 mass parts monomer liquid mixture was dripped over 2 hours. After completion of the dropwise addition, polymerization is carried out by heating and stirring for 2 hours. After completion of the polymerization, by cooling to 28 ° C., fine particles of styrene-acrylic resin are dispersed in an aqueous medium having a solid content of 20% by mass. St-Ac dispersion [1] for the shell was prepared.
The styrene-acrylic resin had a weight average molecular weight (Mw) of 9,800. The glass transition point (Tg) was 59.8 ° C.

[Preparation Example 2 of vinyl resin fine particle dispersion for shell]
A polymerization initiator solution in which 8.5 parts by mass of potassium persulfate was dissolved in 200 parts by mass of ion-exchanged water was added to 1400 parts by mass of ion-exchanged water.
-Styrene 336 mass parts-n-butyl acrylate 64 mass parts-n-octyl mercaptan 8.2 mass parts monomer liquid mixture was dripped over 2 hours. After completion of the dropwise addition, polymerization is carried out by heating and stirring for 2 hours. After completion of the polymerization, by cooling to 28 ° C., fine particles of styrene-acrylic resin are dispersed in an aqueous medium having a solid content of 20% by mass. St-Ac dispersion [2] for the shell was prepared.
The styrene-acrylic resin had a weight average molecular weight (Mw) of 9,500. The glass transition point (Tg) was 60.5 ° C.

[Preparation Example of Release Agent Fine Particle Dispersion]
A solution in which behenate behenate (melting point: 71 ° C.) 60 parts by mass, ionic surfactant “Neogen RK” (Daiichi Kogyo Seiyaku Co., Ltd.) 5 parts by mass, and ion-exchanged water 240 parts by mass was heated to 95 ° C. , After sufficiently dispersing using “Ultra Turrax T50” (manufactured by IKA), by performing dispersion treatment with a pressure discharge type gorin homogenizer, a mold release having a volume-based median diameter of 240 nm and a solid content of 20% by mass A fine agent particle dispersion [W] was prepared.

[Preparation Example of Colorant Fine Particle Dispersion]
While stirring and dissolving 90 g of sodium dodecyl sulfate in 1600 g of ion-exchanged water, 420 g of carbon black “Regal 330R” (manufactured by Cabot) is gradually added, and then the stirring device “Claremix” (M A colorant fine particle dispersion [Bk] in which the colorant fine particles [Bk] are dispersed was prepared by performing a dispersion treatment using a technique manufactured by Technic Co., Ltd. The volume-based median diameter of the colorant fine particles [Bk] in the colorant fine particle dispersion [Bk] was measured using an electrophoretic light scattering photometer “ELS-800” (manufactured by Otsuka Electronics Co., Ltd.) and found to be 110 nm. .

[Example 1: Toner Production Example 1]
In a separable flask equipped with a thermometer, a cooling tube, a nitrogen introducing device, and a stirring device, 400 parts by mass of vinyl-modified crystalline polyester resin fine particle dispersion [A1] for core (solid content conversion), 1500 masses of ion-exchanged water Part, 165 parts by mass of the colorant fine particle dispersion [Bk] and 170 parts by mass of the release agent fine particle dispersion [W]. Further, a sodium hydroxide aqueous solution (25% by mass) was added while maintaining the temperature in the system at 30 ° C., and the pH was adjusted to 10.
Next, an aqueous solution in which 54.3 parts by mass of magnesium chloride hexahydrate is dissolved in 54.3 parts by mass of ion-exchanged water is added, and then the temperature in the system is raised to 90 ° C. The aggregation reaction of the release agent fine particles and the colorant fine particles was started.
After the start of the agglutination reaction, sampling is performed periodically, and the volume-based median diameter of the agglomerated particles becomes 6.3 μm using a particle size distribution analyzer “Coulter Multisizer 3” (manufactured by Beckman Coulter) Then, 200 parts by mass of the St / Ac dispersion for shell [1] was added.
Further, an aqueous solution in which 2 parts by mass of magnesium chloride hexahydrate was dissolved in 2 parts by mass of ion-exchanged water was added over 10 minutes. Stirring was continued until the volume-based median diameter of the particles reached 6.5 μm.
When the circularity of the associated particles was measured using a flow type particle image analyzer “FPIA-2100” (manufactured by Sysmex Corporation), the circularity of the toner particles at this time was 0.92. Stirring was continued for 3 hours at a temperature of 88 ° C., and when the degree of circularity of the associated particles reached 0.940, the mixture was cooled to 30 ° C. at 6 ° C./min to complete the reaction.
Next, the produced toner particle dispersion was subjected to solid-liquid separation with a basket-type centrifuge “MARK III model number 60 × 40” (manufactured by Matsumoto Kikai Kogyo Co., Ltd.) to form a toner wet cake. Thereafter, the toner washing and solid-liquid separation were repeated until the electric conductivity of the filtrate reached 15 μS / cm or less.
Next, the wet cake was transferred to an air-flow dryer “flash jet dryer” (manufactured by Seishin Enterprise Co., Ltd.) and dried until the water content was 0.5 mass%. The drying treatment was performed by blowing an air stream having a temperature of 40 ° C. and a humidity of 20% RH. The dried toner was allowed to cool to 24 ° C., and 1.0 part by mass of hydrophobic silica was mixed with 100 parts by mass of the toner using a Henschel mixer. Toner [1] was obtained by setting the peripheral speed of the rotary blade to 24 m / s, mixing for 20 minutes, and passing through a 400-mesh sieve.

[Examples 2-8, Comparative Examples 1-6: Toner Production Examples 2-14]
Toners [2] to [14] were prepared in the same manner as in Toner Production Example 1 except that the formulation shown in Table 3 was followed.

[Developer Production Examples 1 to 14]
(1) Production of carrier 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) were put into a high-speed mixer equipped with stirring blades at 120 ° C. A carrier having a volume-based median diameter of 50 μm was obtained by stirring and mixing for 30 minutes to form a resin coat layer on the surface of the ferrite core by the action of mechanical impact force.
The volume-based median diameter of the carrier was measured with a laser diffraction particle size distribution measuring apparatus “HELOS” (manufactured by Sympathic) equipped with a wet disperser.

(2) Mixing of toner and carrier To each of the toners [1] to [14], the above carrier is added so that the toner concentration becomes 6%. The developer [1] to [14] was manufactured by mixing at a rotational speed of 45 rpm for 30 minutes.

  Using the developers [1] to [14], the high temperature offset resistance, the crease fixing property, the heat resistant storage property and the charging stability were evaluated.

(1) High-temperature offset resistance In the copying machine “bizhub PRO C6550” (manufactured by Konica Minolta Co., Ltd.), the surface temperature (fixing temperature) of the heating roller can be changed within a range of 100 to 200 ° C. A fixing experiment was conducted to fix a solid image with a toner adhesion amount of 8 mg / cm ² on high-quality A4 size paper in a normal temperature and humidity environment (temperature 20 ° C., humidity 50% RH). The fixing temperature was repeatedly increased from 100 ° C. to 200 ° C. while being increased in increments of 5 ° C.
Among fixing experiments in which image staining due to high temperature offset is not visually observed, the fixing temperature of the fixing experiment relating to the highest fixing temperature was evaluated as the maximum fixing temperature. The results are shown in Table 4. A sample having a maximum fixing temperature of 170 ° C. or higher is determined to be acceptable.

(2) Crease fixing property The crease fixing rate of the test print obtained in the fixing experiment at each fixing temperature used for the evaluation of the above (1) high-temperature offset resistance was measured, and the crease fixing rate exceeded 80%. Among the fixing experiments, the fixing temperature of the fixing experiment relating to the lowest fixing temperature was evaluated as the minimum fixing temperature. The results are shown in Table 4. It is determined that the minimum fixing temperature is 125 ° C. or lower.
Specifically, the crease fixing rate is obtained by bending the test print, rubbing the bent end with a finger three times, then opening the test print, and wiping the solid image three times with “JK Wiper” (manufactured by Crecia). The image density of the solid image at the bent portion was measured and calculated according to the following formula (1). The image density was measured with a Macbeth reflection densitometer “RD-918”. The image density of the solid image of each test print before folding was 0.8.
Formula (1): Fold fixing ratio (%) = {(Image density after folding) / (Image density before folding)} × 100

(3) Heat-resistant storage stability Take 0.5 g of toner in a 10 mL glass bottle with an inner diameter of 21 mm, close the lid, and shake it 600 times at room temperature using a tap denser “KYT-2000” (manufactured by Seishin Enterprise Co., Ltd.). The sample was left for 2 hours in an environment of a temperature of 55 ° C. and a humidity of 35% RH. Next, the toner is placed on a 48-mesh (mesh 350 μm) sieve while being careful not to disintegrate the toner aggregates, set in a powder tester (manufactured by Hosokawa Micron), and fixed with a press bar and knob nut. After adjusting the vibration intensity to a feed width of 1 mm and applying vibration for 10 seconds, the amount of residual toner remaining on the sieve was measured, and the toner aggregation rate, which is the ratio of the residual toner amount, was calculated by the following equation (3). In addition, if it is 20 mass% or less, there is no problem practically and it is judged that it is a pass. The results are shown in Table 4.
Formula (3): toner aggregation rate (mass%) = {residual toner amount (g) /0.5 (g)} × 100

(4) Charging stability Measure the charge amount of the developer before mounting on the image forming apparatus and after printing on 50,000 sheets after mounting on the image forming apparatus. evaluated. The charge amount is a value determined by the following blow-off method.
That is, the developer to be measured is set in a blow-off charge measuring device “TB-200” (manufactured by Toshiba Chemical) equipped with a 400 mesh stainless steel screen, and blown with nitrogen gas for 10 seconds under the condition of a blow pressure of 50 kPa. Then, the charge was measured, and the charge (μC / g) was calculated by dividing the measured charge by the mass of the flying toner.
The results are shown in Table 4. If the charge amount difference is 5 μC / g or less, there is no problem.

Claims (5)

A core-shell structure toner particle composed of a crystalline resin core particle formed by bonding a vinyl polymer segment and a polyester polymer segment, and a shell layer made of a vinyl resin covering the core particle;
The content ratio of the crystalline resin constituting the core particle in the total amount of the resin constituting the core particle is 70 to 100% by mass,
The content ratio of the vinyl polymerization segment in the crystalline resin constituting the core particle is 5 to 30% by mass,
A toner for developing electrostatic images, wherein the vinyl resin constituting the shell layer is a polymerization reaction product of a polymerizable monomer having at least an acid group.   The electrostatic charge image according to claim 1, wherein the vinyl polymer segment in the crystalline resin constituting the core particle and the vinyl resin constituting the shell layer are each made of a styrene-acrylic copolymer. Development toner. The styrene-acrylic copolymer constituting the vinyl polymerization segment in the crystalline resin has a structural unit derived from a (meth) acrylic acid ester monomer represented by the following general formula (1). Item 3. The electrostatic image developing toner according to Item 2.
Formula _{(1): H 2 C =} CR 1 -COOR 2
[Wherein, R ¹ represents a hydrogen atom or a methyl group, and R ² represents an alkyl group having 1 to 8 carbon atoms. ]   The styrene-acrylic copolymer constituting the vinyl resin has a structural unit derived from a (meth) acrylic acid ester monomer represented by the general formula (1). Toner for developing electrostatic images. A vinyl resin (however, the vinyl resin is not the vinyl polymerization segment) is contained in a matrix phase composed of a crystalline resin in which the core particles are formed by bonding a vinyl polymerization segment and a polyester polymerization segment . 5. The electrostatic image developing toner according to claim 1, wherein the toner has a domain-matrix structure dispersed as a domain phase.