JP5733038B2 - Toner for electrostatic image development - Google Patents

Description

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

  In recent years, electrophotographic image forming apparatuses have been increasingly demanded for higher speeds and higher image quality, and the development of toners that can meet the demands of the market for the electrostatic charge image developing toners used therefor has been rapidly increasing. It is being advanced in. 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, an emulsion dispersion of resin particles is mixed with a colorant particle dispersion or, if necessary, a wax dispersion, added with an aggregating agent while stirring, and each particle is aggregated by pH control or the like, and further heated. Thus, 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 point 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 property 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 point compared to styrene-acrylic resin. By using polyester resin for the shell layer, low-temperature fixability and heat-resistant storage are possible. 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). By using a urethane-modified polyester resin or an acrylic-modified polyester resin as the resin constituting the shell layer, a uniform shell layer can be formed to some extent even when a styrene-acrylic resin is used for the core. However, when the core resin is further imparted with a low-temperature fixability in order to further improve the low-temperature fixability, it has not been sufficient in terms of achieving both low-temperature fixability and heat-resistant storage stability.

  On the other hand, a core-shell toner having a crystalline polyester resin in the core and an amorphous polyester resin in the shell layer has been proposed (see, for example, Patent Documents 4, 5, and 6). Also disclosed is a technique for improving low-temperature fixability, offset property, and humidity dependency of charging by using, as a toner resin, a resin in which a radical polymer unit is bonded to a polyester resin via a divalent crosslinking group. (For example, refer to Patent Document 7).

JP 2005-221933 A JP 2005-338548 A JP 2005-173202 A Japanese Patent Laid-Open No. 2007-3840 JP 2009-229920 A JP 2010-61036 A JP 2011-28257 A

  Polyester resin has the advantage of being able to easily design a low softening point while maintaining a high glass transition point compared to styrene-acrylic resin. By using polyester resin for the shell layer, low-temperature fixability and heat-resistant storage are possible. Toner with good properties can be obtained. However, a toner containing a crystalline polyester resin in the core and an amorphous polyester resin in the shell layer is excellent in low-temperature fixability because of its low softening point. There is a problem in that the transfer paper is not separated from the fixing belt or the fixing roller, and the transfer paper is wound, resulting in poor separation performance.

  If the glass transition point of the resin is lowered or the molecular weight is lowered for fixing the toner at a low temperature, the mechanical strength of the formed toner image is lowered. Therefore, when another transfer paper overlaps the printed transfer paper, the toner layer that forms the image causes cohesive failure, and a phenomenon called so-called document offset occurs in which the toner partially transfers to the back surface. There was a problem that the back side of the paper was dirty. When a styrene-acrylic resin is used for the core and a polyester resin is used for the shell layer, the affinity between the styrene-acrylic resin for the core and the polyester resin for the shell is inferior. Formation was difficult, and sufficient heat-resistant storage property could not be obtained.

  The present invention has been made in order to solve the above-described problems. In a toner having a core-shell structure in which a thin, uniform and dense shell layer is provided on the surface of the core particles, the toner has good low-temperature fixing characteristics and is heat resistant An object of the present invention is to provide an electrostatic charge image developing toner that is excellent in storability, does not cause document offset, and has excellent fixing separation performance.

The above-described problems of the present invention are solved by the following configuration.
1. In an electrostatic charge image developing toner having a core-shell structure having core particles containing at least a binder resin and a wax and a shell layer formed by coating the core particles,
The binder resin contains at least a crystalline polyester resin and a styrene-acrylic resin,
Wherein the binder resin is the crystalline polyester resin containing less than 5% by weight to 30% by weight,
The styrene - a structural unit derived from methyl methacrylate to the total of the wax and the binder resin as an acrylic resin component contains 10 wt% or less than 1 wt%,
The surface of the core particle contains a styrene-acrylic resin containing a structural unit derived from the methyl methacrylate,
A toner for developing an electrostatic charge image, wherein the resin constituting the shell layer contains a styrene-acryl-modified polyester resin.
2. 2. The electrostatic image developing toner according to 1 above, wherein the crystalline polyester resin has a melting point of 65 ° C. or higher and 90 ° C. or lower.
3. 3. The electrostatic image developing toner according to 1 or 2 above, wherein the content 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.
4). Of the polyvalent carboxylic acid monomer constituting the polyester segment in the styrene-acrylic modified polyester resin, the content of the aliphatic unsaturated dicarboxylic acid structural unit is 25 mol% or more and 75 mol% or less. 4. The toner for developing an electrostatic charge image according to any one of 3 to 3.
5. 5. The electrostatic image developing toner according to 4 above, wherein the aliphatic unsaturated dicarboxylic acid is represented by the following general formula (A).
General formula (A): HOOC- (CR < ₁ > = CR _{< 2 >} ) _n- COOH
(In the formula, R _{1 and} R ₂ are a hydrogen atom, a methyl group or an ethyl group, and may be the same or different from each other. N is an integer of 1 or 2.)
6). 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 unreactive monomer having a polymerizable unsaturated group and a group capable of reacting with a polyvalent carboxylic acid monomer and / or a polyhydric alcohol monomer for forming a polyester segment of the styrene-acryl-modified polyester resin; 6. The electrostatic charge image developing toner according to any one of 1 to 5, which is obtained by polymerization in the presence of a polyester resin.

  According to the present invention, an electrostatic charge image developing toner having good low-temperature fixing characteristics, excellent heat-resistant storage stability, no occurrence of document offset, and excellent fixing separation performance 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.

  In the toner for developing an electrostatic charge image having a core / shell structure (hereinafter also referred to as toner), the present invention contains a crystalline polyester resin and a styrene acrylic resin as a binder resin constituting the core particles, The binder resin contains 5% by mass or more and 30% by mass or less of a polyester resin, and the styrene-acrylic resin has a structural unit derived from methyl methacrylate as a constituent component in an amount of 1% by mass to 10% with respect to the total of the binder resin and the wax. It is characterized by containing not more than mass%.

  Crystalline polyester resin melts instantly when it is melted by heat, so when heat-fixed, it spreads instantly as a liquid between the toner on the transfer paper and the fixing belt or fixing roller, and can penetrate into the paper fiber. Since it is possible, it is possible to improve adhesiveness to a medium such as transfer paper, so-called fixing property. Further, it is possible to improve the document offset resistance by allowing crystalline polyester to be present on the image surface after fixing.

  On the other hand, when the crystalline polyester resin is melted at the time of fixing, the elasticity is extremely lowered, so that the transfer paper does not separate from the fixing belt or the fixing roller, and so-called fixing separation failure occurs.

  For this reason, if a styrene-acrylic resin, which has a higher elasticity than the polyester resin, is included as a constituent component of the binder resin that constitutes the core particles, it suppresses extremely low elasticity and maintains low-temperature fixability and heat-resistant storage stability. In addition, fixing separation can be improved.

  In the present invention, an amorphous polyester resin modified with a styrene-acrylic resin is used as the resin constituting the shell layer. Amorphous polyester resins generally have the advantage that a low softening point resin can be designed relatively easily while maintaining a high glass transition point. However, if an amorphous polyester resin is used as the resin for the shell layer, it is difficult to form a uniform shell layer with a thin layer because of poor affinity with the core styrene-acrylic resin.

  Therefore, the present inventors use a styrene-acrylic modified polyester resin in which a styrene-acrylic resin segment is bonded to an amorphous polyester resin segment used for a shell layer, and styrene as a binder resin constituting the core particle. -Containing an acrylic resin and a crystalline polyester resin, and containing a structural unit derived from methyl methacrylate in a styrene-acrylic resin constituting the core in an amount of 1% by mass to 10% by mass with respect to the total of the binder resin and the wax. As a result, the affinity between the styrene-acrylic resin constituting the core particles and the polyester resin of the shell layer can be increased, and a smooth, uniform and thin shell layer can be formed.

  Here, the reason why a uniform shell layer can be formed with a thin layer by including methyl methacrylate in the styrene-acrylic resin in the core portion will be considered as follows.

  That is, the core made of styrene-acrylic resin and the shell layer made of polyester resin differ greatly in the SP value (Solubility Parameter) of the resin, so it is difficult to form a thin, uniform and dense shell layer. Therefore, by adding methyl methacrylate having a higher SP value than styrene as a component constituting the styrene-acrylic resin, the affinity with the polyester resin of the shell layer is increased, and a thin and uniform shell layer is formed. It became possible to form. It is considered that the uniform shell layer allows the surface of the toner particles to become smooth and allows the external additive to adhere uniformly without being localized on the surface of the toner.

  This makes it possible to obtain a core-shell toner with a smooth, uniform and thin shell layer with an external additive evenly attached, good low-temperature fixing characteristics, and heat-resistant storage stability. It has become possible to obtain an electrostatic image developing toner that is excellent, has no document offset, and has excellent fixing separation performance.

≪Core particle≫
(Binding resin for core)
The toner for developing an electrostatic charge image of the present invention has a core-shell structure having a shell layer on the surface of the core particle, and the core particle contains a styrene-acrylic resin and a crystalline polyester resin as a binder resin. Yes.

(Styrene-acrylic resin)
Examples of the styrene monomer constituting the styrene-acrylic resin include styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, p-methoxystyrene, p-phenylstyrene, p-chlorostyrene, p- Ethyl styrene, pn-butyl styrene, p-tert-butyl styrene, pn-hexyl styrene, pn-octyl styrene, pn-nonyl styrene, pn-decyl styrene, pn-dodecyl Examples thereof include styrene monomers such as styrene, 2,4-dimethylstyrene, and 3,4-dichlorostyrene and derivatives thereof.

  As an acrylic monomer constituting the styrene-acrylic resin, methyl methacrylate is contained in an amount of 1% by mass to 10% by mass with respect to the total of the binder resin and the wax.

  When the content of methyl methacrylate is less than 1% by mass, the affinity between the core particles and the shell particles is insufficient, so that the surface smoothness is deteriorated and the heat resistant storage property is deteriorated. If it exceeds 10% by mass, the SP value of the styrene-acrylic resin will increase and the difference from the SP value of the release agent will increase, making it impossible to incorporate the release agent particles into the interior, fixing separation properties, and heat resistant storage stability. Will be inferior.

  Examples of other acrylic monomers that can be used in the styrene-acrylic resin of the present invention include acrylate monomers and methacrylate monomers, such as methyl acrylate, ethyl acrylate, butyl acrylate, acrylic acid- 2-ethylhexyl, cyclohexyl acrylate, phenyl acrylate, ethyl methacrylate, butyl methacrylate, hexyl methacrylate, 2-ethylhexyl methacrylate, ethyl β-hydroxyacrylate, propyl γ-aminoacrylate, stearyl methacrylate, methacryl Examples thereof include dimethylaminoethyl acid, diethylaminoethyl methacrylate and the like.

  These styrene monomers, acrylic monomers and other polymerizable vinyl monomers may be used alone or in combination of two or more. Peroxides, persulfides and azo compounds usually used for the polymerization of these monomers. An arbitrary polymerization initiator such as bulk polymerization, solution polymerization, emulsion polymerization method, miniemulsion method, suspension polymerization method, and dispersion polymerization method can be added to obtain a polymer by polymerization. it can. Moreover, the chain transfer agent generally used can be used in order to adjust molecular weight. The chain transfer agent is not particularly limited, and examples thereof include alkyl mercaptans and mercapto fatty acid esters.

(Crystalline polyester resin)
The crystalline polyester resin used as the resin constituting the core of the electrostatic image developing toner of the present invention will be described.

  “Crystallinity” of the crystalline polyester resin in the present invention means that it has a clear endothermic peak in differential scanning calorimetry (DSC) instead of a stepwise endothermic change. A crystalline polyester resin having a half-value width of an endothermic peak of less than 10 ° C when measured at ° C / min.

  The crystalline polyester resin is produced by a polycondensation reaction using a polyester-forming composition comprising a polyvalent carboxylic acid (derivative) and a polyhydric alcohol (derivative) as a raw material. Examples include carboxylic acid alkyl esters, acid anhydrides and acid chlorides. Examples of polyhydric alcohol derivatives include polyhydric alcohol ester compounds and hydroxycarboxylic acids.

  The polyvalent carboxylic acid is a compound containing two or more carboxyl groups in one molecule. Among these, divalent carboxylic acid is a compound containing two carboxyl groups in one molecule. For example, 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, citraconic acid, diglycolic acid, cyclohexane-3,5-diene-1,2-dicarboxylic acid, malic acid, citric acid, hexahydroterephrine Tar 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-phenylenedi Glycolic acid, p-phenylene diglycolic acid, o-phenylene di Recolic acid, diphenylacetic acid, diphenyl-p, p'-dicarboxylic acid, naphthalene-1,4-dicarboxylic acid, naphthalene-1,5-dicarboxylic acid, naphthalene-2,6-dicarboxylic acid, anthracene dicarboxylic acid, dodecenyl succinic acid, etc. Can be mentioned.

  Examples of the polyvalent carboxylic acid other than the divalent carboxylic acid include trimellitic acid, pyromellitic acid, naphthalenetricarboxylic acid, naphthalenetetracarboxylic acid, pyrenetricarboxylic acid, and pyrenetetracarboxylic acid.

  A polyhydric alcohol is a compound containing two or more hydroxyl groups in one molecule. Among these, a divalent polyol (diol) is a compound containing two hydroxyl groups in one molecule. For example, ethylene glycol, propylene glycol, butanediol, diethylene glycol, hexanediol, cyclohexanediol, octanediol, decanediol, Examples include dodecanediol, bisphenol A ethylene oxide adduct, and bisphenol A propylene oxide adduct. Examples of polyols other than divalent polyols include glycerin, pentaerythritol, hexamethylol melamine, hexaethylol melamine, tetramethylol benzoguanamine, and tetraethylol benzoguanamine.

  As the polymerization catalyst for the crystalline polyester resin of the present invention, a general known catalyst can be used.

  The melting point Tm of the crystalline polyester resin particles is preferably 65 ° C. or higher and 90 ° C. or lower, more preferably 70 ° C. or higher and 80 ° C. or lower. If Tm is 90 ° C. or higher, low-temperature fixability is hindered, causing problems, and if it is 65 ° C. or lower, heat-resistant storage stability is lowered.

(Measuring method of melting point of crystalline polyester resin)
The melting point of the crystalline polyester resin can be measured by a differential calorimeter (DSC), for example, using a DSC-7 differential scanning calorimeter (Perkin Elmer) or a TAC7 / DX thermal analyzer controller (Perkin Elmer). be able to. Specifically, 4.50 mg of a sample is sealed in an aluminum pan (KIT No. 0219-0041), which is set in a sample holder of “DSC-7”, and an empty aluminum pan is used for measuring the reference. Heat-Cool-Heat temperature control was performed at a measurement temperature of 0 to 200 ° C. under measurement conditions of a temperature increase rate of 10 ° C./min and a temperature decrease rate of 10 ° C./min. Get data in Heat. The melting point is the temperature at the peak top of the endothermic peak.

  Moreover, it is preferable that the weight average molecular weights of the crystalline polyester resin to be used are 3000 or more and 20000 or less, More preferably, it is the range of 5000 or more and 10,000 or less. When the weight average molecular weight is 20000 or more, the low temperature fixability is inhibited. On the other hand, if the weight average molecular weight is 3000 or less, the fixing separation property is deteriorated.

  In addition, the polycondensable monomer may have partial branching or crosslinking depending on selection of the carboxylic acid valence and alcohol valence.

  The crystalline polyester resin is contained in an amount of 5 to 30% by mass, preferably 10 to 20% by mass, based on the total mass of the core binder resin. Within this range, the low-temperature fixability and heat-resistant storage stability can be controlled within a preferable range.

  The core particles can contain a colorant, a charge control agent, and the like, if necessary, in addition to the binder resin and the wax.

(Coloring agent)
As the colorant used in the toner of the present invention, carbon black, a magnetic material, a dye, a pigment, and the like can be arbitrarily used. As carbon black, channel black, furnace black, acetylene black, thermal black, lamp black, and the like can be used. Etc. are used. As the magnetic material, ferromagnetic metals such as iron, nickel and cobalt, alloys containing these metals, and compounds of ferromagnetic metals such as ferrite and magnetite can be used.

  As the 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.

≪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. 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, 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.

  In the present invention, the content ratio 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. In particular, the content is preferably 5% by mass or more and 20% by mass or less.

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

  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.

  The styrene-acrylic resin unit may be bonded to the terminal of the polyester main chain, or may be grafted as a side chain. However, the styrene-acrylic modified polyester resin in which the styrene-acrylic resin unit is bonded to the end of the polyester resin is easier to form the domains of the polyester resin unit and the styrene-acrylic resin unit. Therefore, in the aggregation / fusion process, the polyester resin unit is easily oriented on the toner surface layer and the styrene-acrylic resin unit is easily oriented on the core made of styrene-acrylic resin. can do. In contrast, when the styrene-acrylic resin unit is grafted as a side chain on the main chain of the polyester resin unit, the polyester domain and the styrene-acrylic domain are relatively mixed. There is a fear.

  In the toner of the present invention, an aliphatic unsaturated dicarboxylic acid is used as a polyvalent carboxylic acid monomer to form a polyester segment of a styrene-acryl-modified polyester resin, and the aliphatic unsaturated dicarboxylic acid is added to the polyester segment. It is preferable that a structural unit derived from an acid is contained. The aliphatic unsaturated dicarboxylic acid refers to a chain dicarboxylic acid having a vinylene group in the molecule.

  According to the styrene-acryl-modified 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 one represented by the following general formula (A).

General formula (A): HOOC- (CR < ₁ > = CR _{< 2 >} ) _n- COOH
(Wherein R ₁ and R ₂ are a hydrogen atom, a methyl group or an ethyl group and may be the same or different from each other. N is an integer of 1 or 2)
By 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. Moreover, in this invention, when using aliphatic unsaturated dicarboxylic acid represented by general formula (A) for a polymerization reaction, it can also be used with the form of an anhydride.

  By increasing the hydrophilicity of the polyester resin, when the toner particles are produced by an emulsion aggregation method in an aqueous medium, the effect of the polyester resin segment being oriented to the outside, that is, the aqueous medium side with respect to the core particles is increased. 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 more uniform and dense shell layer due to the hydrophilic effect by the carbon-carbon double bond in the polyester resin segment, while keeping the affinity of Inferred.

  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 left flat for 12 hours or more. Then, a molding machine “SSP-10A” (Shimadzu Corporation) Pressure) 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.

(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.

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
(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.

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.

  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 the two reactive monomers when the total mass of is 100% by mass is 0.1% by mass or more and 10.0% by mass or less, and particularly 0.5% by mass or more and 3.0% by mass or less. It is preferable.

(Aromatic vinyl monomers and (meth) acrylic acid ester monomers)
The aromatic vinyl monomer and (meth) acrylic acid ester monomer for forming the styrene-acrylic polymer segment have an ethylenically unsaturated bond capable of performing radical polymerization.

  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.

  Examples of (meth) acrylic acid ester monomers include methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, cyclohexyl acrylate, phenyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, Examples include hexyl methacrylate, 2-ethylhexyl methacrylate, ethyl β-hydroxyacrylate, propyl γ-aminoacrylate, stearyl methacrylate, dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate, and the like. These (meth) acrylic acid ester monomers can be used alone or in combination of two or more.

  As 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 and methacrylic acid as both reactive monomers.

(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 a polyvalent carboxylic acid monomer (derivative) and a 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 above general formula (A) is used. It is preferable. In the present invention, an anhydride of a dicarboxylic acid 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 (A), the obtained styrene-acryl-modified polyester resin is more surely a thin layer with a more uniform film thickness and 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, and the like. And trivalent or higher polyols such as glycerin, pentaerythritol, hexamethylol melamine, hexaethylol melamine, tetramethylol benzoguanamine, and tetraethylol benzoguanamine.

  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 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, the chain transfer generally used for the purpose of adjusting the molecular weight of the styrene-acrylic polymer segment. An agent 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 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.

(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 of toner particles)
First, the circularity of the toner particles used in the present invention will be described. The 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.

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 _50V ) 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 _50V ) of 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.

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

  Examples of the method for producing the toner base particles include a pulverization method, 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, it is possible to easily reduce the size of the toner base particles from the viewpoint of production cost and production stability.

  Here, the emulsion aggregation method refers to a dispersion of binder resin particles produced by emulsification (hereinafter also referred to as “binder resin particles”) as colorant particles (hereinafter referred to as “colorant particles”). ), And agglomerated until a desired toner base particle size is obtained, and further, the shape control is performed by fusing the binder resin particles to produce toner base particles. 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 base particles ( 4) A step of filtering the toner base particles from the dispersion of the toner base particles (aqueous medium) and removing the surfactant, etc. (5) A step of drying the toner base particles (6) An external additive is added to the toner base particles. Step of Adding Toner 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.

  As a method for dispersing the binder resin particles in the step (2), an emulsion polymer particle dispersion obtained by emulsion polymerization is preferably used. 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). Furthermore, similarly, a polymerization initiator and a polymerizable monomer are added to this dispersion, and this system can be polymerized (third-stage polymerization) to form a three-layer structure.

  In the emulsion aggregation method, toner base particles having a core-shell structure can also be obtained. Specifically, the toner base particles having a core-shell structure are prepared by first binding resin particles for core particles and a colorant. The core particles are prepared by agglomerating and fusing the particles, and then the binder resin particles for the shell layer are added to the core particle dispersion to aggregate the binder resin particles for the shell layer on the surface of the core particles It can be obtained by forming a shell layer that covers the surface of the core particles by fusing.

  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.

  The step of aggregating and assembling the resin particles in the emulsion aggregation method will be described.

  In the aggregation process, an aqueous dispersion of resin particles is mixed with a dispersion of colorant particles and, if necessary, wax particles, 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 flocculation step, it is preferable that the standing time (time until heating is started) to be left after adding the flocculant 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 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.

(Dispersion of colorant)
The dispersion of the colorant particles used in the aggregation process can be prepared by dispersing the 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.

(External additive)
In the present invention, an external additive can be added to the toner base particles 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 core resin particle dispersion [A] (2) Preparation of colorant dispersion [1] (3) Preparation of resin particle dispersion [B] for shell (4) Preparation of toner (aggregation / melting) Adhesion to external additive treatment process)
The following will be described in order.

<Production of toner>
(1) Production of core resin particle dispersion [A1] (a) Production of crystalline polyester resin [P1] 1,4-butanediol 459 parts by mass, 1,6-hexanediol 1404 parts by mass, fumaric acid 1972 parts by mass Was added to 4 parts by mass of dibutyltin oxide and 2 parts by mass of hydroquinone as a catalyst and reacted at 160 ° C. for 5 hours in a nitrogen gas atmosphere. Furthermore, it was made to react until a resin with a desired melting point was obtained at 8.3 kPa to obtain a crystalline polyester resin [A1]. When this crystalline polyester resin [P1] was measured at 10 ° C./min by DSC, it had a clear peak, and the peak top temperature was 80.6 ° C. The half width was 5 ° C.

(B) Synthesis of crystalline polyester resins [P2] to [P5] Crystalline polyester resins [P2] to [P5] were synthesized in the same manner using the alcohol components and acidic components shown in Table 1.

(C) Preparation of core resin particle dispersion [A1] (c-1) First stage polymerization (preparation of resin particles [1H])
A reaction vessel equipped with a stirrer, a temperature sensor, a condenser, and a nitrogen introducing device was charged with a solution prepared by dissolving 0.64 parts by mass of sodium dodecyl sulfate in 103.5 parts by mass of ion-exchanged water, and stirred at 230 rpm under a nitrogen stream. The internal temperature was raised to 80 ° C. while stirring at a speed. After the temperature rise, a solution in which 0.47 parts by mass of potassium persulfate was dissolved in 18.5 parts by mass of ion-exchanged water was added, the liquid temperature was again 80 ° C., and the following monomer mixture was added dropwise over 1 hour. After heating at 80 ° C. for 2 hours, polymerization was carried out by stirring to prepare resin particles [1H].

Styrene (St) 28.5 parts by mass n-butyl acrylate (BA) 7.1 parts by mass Methacrylic acid (MAA) 1.9 parts by mass (c-2) Second stage polymerization (preparation of resin particles [1HM])
The following monomer mixture is heated to 90 ° C. with stirring, 80 parts by mass of pentaerythritol tetrabehenate and 160 parts by mass of the crystalline polyester resin [P1] are dissolved in the mixture as wax, and the wax and the crystalline polyester resin are dissolved. A monomer mixture containing was prepared.

Styrene 156.3 parts by mass n-butyl acrylate 43.3 parts by mass n-octyl-3-mercaptopropionate 2.9 parts by mass A reaction vessel equipped with a stirrer, a temperature sensor, a condenser, and a nitrogen introduction unit A solution prepared by dissolving 5.05 parts by mass of sodium oxyethylene (2) dodecyl ether sulfate in 790 parts by mass of ion-exchanged water was added, and after heating to 98 ° C., a monomer mixture containing the wax and the crystalline polyester resin was added. Then, it was mixed and dispersed for 1 hour by a mechanical disperser “CLEARMIX” (manufactured by M Technique Co., Ltd.) having a circulation path to prepare a dispersion containing emulsified particles (oil droplets). The dispersion was added with 37.5 parts by mass of the resin particles [1H] and 1500 parts by mass of ion-exchanged water. The reaction vessel equipped with the apparatus was charged.

  Next, an initiator solution in which 4.54 parts by mass of potassium persulfate was dissolved in 86.3 parts by mass of ion-exchanged water was added to this dispersion, and this system was heated and stirred at 82 ° C. for 1 hour. Polymerization was performed to obtain resin particles [1HM].

(C-3) Third-stage polymerization (preparation of core resin particle dispersion [A1])
Furthermore, a solution in which 6.07 parts by mass of potassium persulfate was dissolved in 118 parts by mass of ion-exchanged water was added, and under a temperature condition of 82 ° C.,
Styrene 205.1 parts by weight Methyl methacrylate 22.8 parts by weight n-butyl acrylate 77.3 parts by weight Methacrylic acid 17.8 parts by weight n-octyl-3-mercaptopropionate 4.39 parts by weight of monomer mixture Was added dropwise over 1 hour. After completion of the dropwise addition, polymerization was carried out by heating and stirring for 2 hours, followed by cooling to 28 ° C. to obtain a resin particle dispersion for core [A1] containing crystalline polyester resin particles and styrene-acrylic resin particles. It was.

The volume-based median diameter (D _50V ) of the resin particles in the core resin particle dispersion [A1] was 178 nm, and the weight average molecular weight (Mw) was 33,500.

  Similarly, the resin composition for cores [A2] to [A13] were obtained by changing the monomer composition as shown in Table 2 by the above method. The core resin particle dispersion [A14] was prepared in the same manner as in the preparation of the core resin particle dispersion [A1] except that the crystalline polyester resin [P1] was not added.

  Table 3 shows the methyl methacrylate content, crystalline polyester content, particle size, and weight average molecular weight of the core resin particle dispersion obtained by the above method.

(2) Preparation of Colorant Dispersion Liquid [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 “Regal 330R” (Cabot Corp.) is gradually added, and then dispersed using a stirring device “Cleamix” (M Technique Corp.). A colorant dispersion liquid [1] having the colorant particles dispersed therein was prepared. The particle diameter of this dispersion was measured using UPA (manufactured by Microtrac) and found to be 117 nm.
(3) Preparation Step of Resin Particle Dispersion [B1] for Shell (3-1) Synthesis of Resin for Shell (Styrene-Acrylic Modified Polyester Resin [B1]) Equipped with nitrogen introduction tube, dehydration tube, stirrer and thermocouple In the four-necked flask
Bisphenol A propylene oxide 2-mole adduct 285.7 parts by mass Terephthalic acid 66.9 parts by mass Fumaric acid 47.4 parts by mass Esterification catalyst (tin octylate) 1.43 parts by mass were added, and condensation polymerization was carried out at 230 ° C for 8 hours. Reaction, further reaction at 8 kPa for 1 hour, cooling to 160 ° C.,
Acrylic acid 10 parts by weight Styrene 80 parts by weight Butyl acrylate 20 parts by weight Polymerization initiator (di-t-butyl peroxide) A mixture of 16 parts by weight was added dropwise with a dropping funnel over 1 hour, and then maintained at 160 ° C. After continuing the addition polymerization reaction for 1 hour, the temperature was raised to 200 ° C. and held at 10 kPa for 1 hour, and then styrene and butyl acrylate were removed to obtain a styrene-acryl-modified polyester resin [B1]. .

This styrene-acryl-modified polyester resin [B1] had a glass transition point of 60 ° C. and a softening point of 105 ° C.
(3-2) Preparation of Resin Particle Dispersion Liquid [B1] for Shell 100 parts by mass of the obtained styrene-acrylic modified polyester resin [B1] was pulverized with “Landel mill type: RM” (manufactured by Tokuju Kogakusha Co., Ltd.) It is mixed with 638 parts by mass of a sodium lauryl sulfate solution having a concentration of 0.26% by mass prepared in advance and stirred for more than 30 minutes at V-LEVEL of 300 μA using an ultrasonic homogenizer “US-150T” (manufactured by Nippon Seiki Seisakusho). A “resin particle dispersion liquid for shell [B1]” in which styrene-acryl-modified polyester [B1] having a volume-based median diameter (D _50V ) of 180 nm is dispersed was produced by sonic dispersion.
(3-3) Preparation of Resin Particle Particle Dispersions [B2] to [B10] for Shells In the same manner, the composition of the monomer is changed as shown in Table 4 and the shell particles composed of styrene-acryl-modified polyester resin particles are used. Resin particle dispersions [B2] to [B10] were obtained.
(3-4) Step of preparing resin particle dispersion for shell [B11] (Preparation of polyester resin (a))
In a reaction vessel equipped with a cooling tube, a stirrer and a nitrogen introducing tube, 285.7 parts by mass of bisphenol A propylene oxide 2-mol adduct, 66.9 parts by mass of terephthalic acid, 47.4 parts by mass of fumaric acid, and polycondensation As a catalyst, 2 parts by mass of titanium tetraisopropoxide was added in 10 portions and reacted at 200 ° C. for 10 hours while distilling off the water produced in a nitrogen stream. Next, the reaction was carried out under reduced pressure of 13.3 kPa (100 mmHg), and the mixture was taken out when the softening point reached 104 ° C. This is designated as polyester resin (a). The polyester resin (a) had a Tg of 58 ° C., a number average molecular weight of 4500, and a weight average molecular weight of 13500.

(Production of styrene-acrylic modified polyester resin [B11])
In an autoclave reaction vessel equipped with a thermometer and a stirrer, 430 parts by mass of xylene and the polyester resin (a) obtained above were placed and dissolved, and after substitution with nitrogen, 80 parts by mass of styrene, 20 parts by mass of butyl acrylate, A mixed solution of 40 parts by mass of t-butyl peroxide and 100 parts by mass of xylene was dropped and polymerized at 170 ° C. for 3 hours, and further maintained at this temperature for 30 minutes. Subsequently, distilled water was added to remove the solvent to obtain a styrene-acrylic modified polyester resin [B11].

(Preparation of shell resin particle dispersion [B11])
100 parts by mass of styrene-acryl-modified polyester resin [B11] was dissolved in 400 parts by mass of ethyl acetate (manufactured by Kanto Chemical Co., Inc.) while stirring. Next, the mixture was mixed with 401 parts by mass of a 0.26% by mass sodium lauryl sulfate solution prepared in advance, and ultrasonicated with an ultrasonic homogenizer “US-150T” (manufactured by Nippon Seiki Seisakusho) at V-LEVEL 300 μA for 30 minutes 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, and the median diameter on a volume basis ( A “resin particle dispersion for shell [B11]” composed of styrene-acryl-modified polyester resin particles [B11] having a D _50V ) of 180 nm and a solid content of 20% by mass was obtained.
(3-5) Preparation of Resin Particle Liquid Dispersion [B12] for Shell Similarly, by changing the composition of the polyester segment and the styrene-acrylic polymer segment as shown in Table 4 below, the styrene-acrylic modified polyester A resin particle dispersion for shells [B12] comprising resin particles [B12] was obtained.
(3-6) Synthesis of polyester resin [B13] In a four-necked flask equipped with a nitrogen introduction tube, a dehydration tube, a stirrer, and a thermocouple,
Bisphenol A propylene oxide 2-mole adduct 285.7 parts by mass Terephthalic acid 66.9 parts by mass Fumaric acid 47.4 parts by mass Esterification catalyst (tin octylate) 1.43 parts by mass were added, and condensation polymerization was carried out at 230 ° C for 8 hours. The mixture was further reacted at 8.3 kPa for 1 hour. This was designated as polyester resin [B13].

(4) Preparation of toner (aggregation / fusion-external additive treatment process)
<Preparation of Toner 1>
(Aggregation / fusion process)
In a 5 liter stainless steel reactor equipped with a stirrer, a cooling tube, and a temperature sensor, 244 parts by mass (in terms of solid content) of “core resin particle dispersion [A1]”, 1695 parts by mass of ion-exchanged water, “coloring” 27 parts by mass (in terms of solid content) of the agent dispersion [1] was charged, and the pH was adjusted to 10 using a 5 (mol / liter) aqueous sodium hydroxide solution while stirring.

  Next, with stirring, an aqueous magnesium chloride solution in which 56 parts by mass of magnesium chloride hexahydrate was dissolved in 56 parts by mass of ion-exchanged water was added dropwise over 10 minutes, the internal temperature was raised to 75 ° C., and the multisizer 3 ( The particle diameter was measured using a Beckman Coulter Co., Ltd. aperture diameter; 50 μm. When the average particle diameter reached 5.8 μm, “shell resin particle dispersion [B1]”, 61 parts by mass (solid Minute conversion) was added dropwise, and heating and stirring were continued until the styrene-acryl-modified polyester resin particles adhered to the surface of the aggregated particles.

  When a small amount of the reaction solution is centrifuged with a centrifuge and the supernatant becomes transparent, a sodium chloride aqueous solution in which 73 parts by mass of sodium chloride is dissolved in 292 parts by mass of ion-exchanged water is added, and the heating and stirring are continued. Using a flow type particle image measuring device “FPIA-2100” (manufactured by Sysmex Corporation), when the average circularity reached 0.960, the internal temperature was cooled to 25 ° C., and a dispersion of “toner base particle 1” was obtained. Obtained.

(Washing and drying)
The dispersion of toner base particles 1 produced in the aggregation / fusion process was subjected to solid-liquid separation using a basket-type centrifuge to form a wet cake of toner base particles. The wet cake was washed with ion exchange water at 35 ° C. until the electric conductivity of the filtrate reached 5 μS / cm with the basket-type centrifuge, and then transferred to “flash jet dryer (manufactured by Seishin Enterprise Co., Ltd.)”. The toner was dried until the amount became 0.5% by mass to prepare “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 a Henschel mixer is used. The toner 1 was prepared by mixing.

<Preparation of Toner 2 to Toner 24>
In the same manner as in the toner 1, the configurations of the core and the shell were changed as shown in Table 5 to prepare toners 2 to 24.

<Preparation of Toner 25>
Toner 25 was prepared in the same manner as toner 1 except that polyester resin [B13] not modified with styrene-acryl was used as the shell resin.

<Preparation of Toner 26>
A toner 26 was prepared in the same manner as the toner 1 except that the crystalline polyester resin [P1] was used as the binder resin for the core and no styrene-acrylic resin was contained.

<Preparation of Toner 27>
Toner 27 was prepared in the same manner as toner 1 except that the core resin particle dispersion [A14] made of styrene-acrylic resin not containing crystalline polyester was used as the core binder resin.

  Here, toner 1 to toner 14 and toner 19 to toner 24 are toners of the present invention, and toner 15 to toner 18 and toner 25 to toner 27 are comparative toners.

<Production 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 40 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 27 are added to the carrier so that the toner concentration is 7% by mass, and the mixture is put into a micro-type V-type mixer (Tsujii Chemical Co., Ltd.) and mixed at a rotational speed of 45 rpm for 30 minutes. 1 to Developer 27 were prepared.

<Evaluation>
(Fixing separation)
Fixing separation evaluation: Kanfuji 85g / m ² T, which was conditioned at room temperature and humidity overnight (NN environment: 25 ° C, 50% RH) using a modified "bizhub C6500" (manufactured by Konica Minolta Business Technologies). A solid image with a margin of 5 mm at the end of the eye (made by Oji Paper Co., Ltd.) and a fixing temperature of 195 ° C./120° C. was produced by changing the amount of adhesion, and the amount of adhesion of the solid image immediately before the occurrence of a paper jam (jam) ( g / m ² ) was measured and used as a separation limit adhesion amount, which was a measure of fixing separation performance. The larger this value, the better the separation performance. In addition, it implements in normal temperature normal humidity environment (NN environment: 25 degreeC, 50% RH).

A: 3.5 g / m ² or more B: 2.0 g / m ² or more and less than 3.5 g / m ² Δ: 1.0 g / m ² or more and less than 2.0 g / m ² ×: 1.0 g / m ²
(Low-temperature fixability (under offset property))
Under offset refers to an image defect that peels from a transfer material such as recording paper because the toner layer is not sufficiently melted by the heat applied when passing through the fixing machine.

The image evaluation was performed by sequentially loading the toner and the developer prepared above in 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. Using NPI 128 g / m ² (manufactured by Nippon Paper Industries) as an evaluation paper, a solid image with a toner adhesion amount of 11.3 g / m ² is fixed at a fixing speed of 300 mm / sec, the temperature of the fixing upper belt is 110 to 200 ° C., and the temperature of the fixing lower roller Was set at 100 ° C., and when fixing was performed at a level of 5 ° C., the lower limit fixing temperature of the upper fixing belt where no under-offset occurred was evaluated and used as an index for low temperature fixing property. The lower this fixing minimum temperature is, the better the fixing property is, and a temperature lower than 160 ° C. is considered acceptable.

◎: Less than 130 ° C ○: 130 ° C or more and less than 140 ° C △: 140 ° C or more and less than 160 ° C ×: 160 ° C or more (heat-resistant storage property)
0.5 g of toner is placed in a 10 ml glass bottle with an inner diameter of 21 mm, the lid is closed, shaken 600 times at room temperature with a tap denser KYT-2000 (manufactured by Seishin Enterprise), and then removed at 57.5 ° C., 35 It was left for 2 hours in an environment of% RH. Next, place the toner on a 48-mesh (mesh 350 μm) sieve, taking care not to crush the toner aggregates, set the powder tester (manufactured by Hosokawa Micron), and fix it with a press bar and knob nut. After adjusting the vibration strength to a feed width of 1 mm and applying vibration for 10 seconds, the 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 and used as an index for storage stability.

A: The toner aggregation rate is less than 10% by mass (the heat-resistant storage stability of the toner is extremely good).
○: The toner aggregation rate is 10% by mass or more and less than 15% by mass (good heat-resistant storage property of the toner)
Δ: The toner aggregation rate is 15% by mass or more and less than 20% by mass (the heat-resistant storage property of the toner is slightly inferior but is acceptable)
X: The toner aggregation rate is 20% by mass or more (the toner has poor heat storage stability and cannot be used).

(Document offset resistance evaluation)
Using the above-mentioned remodeling machine, the fixing conditions were changed so that the gloss was 60 to 70 on a solid patch with an adhesion amount of 10.0 g / m ² on POD128 (Oji Paper), and a fixed image was output. The gloss was measured with a microgloss 75 ° manufactured by Gardner. In addition, a sheet of white POD128 paper that was passed under the identification condition was prepared, and temperature and pressure were applied to the image portion and the image portion, and the image portion and the non-image portion bonded together. The conditions of temperature and pressure are two levels of 60 ° C./10 g / m ² and 50 ° C./80 g / m ² . After these samples were exposed for one week, the images were slowly peeled off, and the document offset resistance was evaluated visually according to the degree of transfer to one side by the following rank, and used as an index of image storage stability.

◎: Level where there is no transition to one side and no problem ○: There is no transition to one side of the image and there is uneven glossiness △: There is a slight transition to one side of the image, but acceptable level ×: Difficult to separate, There is a great deal of transition to one side. Any of the above evaluation criteria also pass Δ or better.

  The evaluation results are shown in Table 6 below.

  From the results shown in Table 6, toners 1 to 14 and toners 19 to 24, which are the toners of the present invention, can be put into practical use with any of the following characteristics: fixing separation, low temperature fixing, document offset resistance, and heat storage stability. The toner 15 to the toner 17 and the toner 25 to the toner 27 for comparison outside the present invention have problems in at least one of the characteristics and are not at a practically usable level. Recognize.

Claims (6)

In an electrostatic charge image developing toner having a core-shell structure having core particles containing at least a binder resin and a wax and a shell layer formed by coating the core particles,
The binder resin contains at least a crystalline polyester resin and a styrene-acrylic resin,
Wherein the binder resin is the crystalline polyester resin containing less than 5% by weight to 30% by weight,
The styrene - a structural unit derived from methyl methacrylate to the total of the wax and the binder resin as an acrylic resin component contains 10 wt% or less than 1 wt%,
The surface of the core particle contains a styrene-acrylic resin containing a structural unit derived from the methyl methacrylate,
A toner for developing an electrostatic charge image, wherein the resin constituting the shell layer contains a styrene-acryl-modified polyester resin.
  The toner for developing an electrostatic charge image according to claim 1, wherein the crystalline polyester resin has a melting point of 65 ° C. or higher and 90 ° C. or lower.   3. 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 structural unit in the polyvalent carboxylic acid monomer 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 any one of claims 1 to 3. The electrostatic image developing toner according to claim 4, wherein the aliphatic unsaturated dicarboxylic acid is represented by the following general formula (A).
General formula (A): HOOC- (CR < ₁ > = CR _{< 2 >} ) _n- COOH
(Wherein R ₁ and R ₂ are a hydrogen atom, a methyl group or an ethyl group and may be the same or different from each other. N is an integer of 1 or 2) 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 unreactive monomer having a polymerizable unsaturated group and a group capable of reacting with a polyvalent carboxylic acid monomer and / or a polyhydric alcohol monomer for forming a polyester segment of the styrene-acryl-modified polyester resin; 6. The electrostatic image developing toner according to claim 1, wherein the toner is obtained by polymerization in the presence of a polyester resin.