JP2012173303A - Toner for developing electrostatic charge image and method for manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a toner for developing an electrostatic charge image, the toner excellent in low-temperature fixability, releasing property from a fixing roller, and heat-resistant storage property.SOLUTION: A toner for developing an electrostatic charge image includes toner base particles in a core-shell structure comprising a shell layer containing a polyester resin formed on the surface of a core particle containing at least a styrene-acrylic resin and wax, where the toner base particles include higher alcohol represented by the general formula (1). The general formula (1): CH(CH)OH (In the formula, x represents an integer of 5 to 17.)

Description

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

  In recent years, in the field of electrostatic image developing toner (hereinafter also simply referred to as “toner”), in response to market demand, development of an electrophotographic apparatus suitable for it and toner usable therefor has been rapidly advanced. Yes. For example, a toner compatible with high image quality is required to have a sharp particle size distribution. When the toner particle size is uniform and the particle size distribution is sharpened, the development behavior of each individual toner particle is uniformed, so that the reproducibility of minute dots is remarkably improved. However, it is not easy to sharpen the particle size distribution of the toner by a conventional toner manufacturing method using a pulverization method.

  On the other hand, an emulsion aggregation method has been proposed as a production method capable of arbitrarily controlling the shape and particle size distribution of toner particles. In this method, a colorant particle dispersion and, if necessary, a wax dispersion are mixed with an emulsion dispersion of resin particles, and while stirring, each particle is aggregated by addition of a flocculant, pH control, and the like. The toner particles are obtained by fusing the particles.

  Further, from the viewpoint of energy saving, development of a low-temperature fixing toner that can be fixed with less energy is in progress. In order to lower the fixing temperature of the toner, it is necessary to lower the melting temperature and melt viscosity of the binder resin. However, if the glass transition temperature or molecular weight of the binder resin is lowered in order to lower the melting temperature or melt viscosity of the binder resin, new problems arise, such as the heat resistant storage 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). In other words, it is possible to achieve both low-temperature fixability and heat-resistant storage stability by forming a shell layer composed of particles with high glass transition point and softening point and excellent heat resistance on the surface of core particles excellent in low-temperature fixability. Become. 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 the shell layer has been proposed (see, for example, Patent Document 2). Polyester resin has the advantage of being able to easily design a low softening point while maintaining a high glass transition temperature as compared with styrene-acrylic resin. Styrene-acrylic resin is used as the core binder resin, and polyester is used for the shell layer. It is considered that a toner having good low-temperature fixability and heat-resistant storage can be obtained by using a resin.

  However, the affinity between styrene-acrylic resin and polyester resin is poor, 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. Sufficient heat storage stability 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, by using a core-shell toner using a urethane-modified polyester resin and / or an acrylic-modified polyester resin in the shell layer, the low-temperature fixability, heat-resistant storage property, and high-temperature offset resistance are improved. A technique has been proposed (see, for example, Patent Document 3).

JP 2005-221933 A JP 2005-338548 A JP 2005-173202 A

  Even when a styrene-acrylic resin is used for the core by using a urethane-modified polyester resin or an acrylic-modified polyester resin as a resin constituting the shell layer in order to improve the affinity between the styrene-acrylic resin and the polyester resin. A uniform shell layer can be formed to some extent. However, it is still sufficient in terms of achieving both low-temperature fixability and heat-resistant storage stability when the core resin is given further low-temperature fixability in response to market demand. It wasn't.

  The present invention has been made to solve the above-described problems. By forming a thin and uniform shell layer on the surface of the core particles, sufficient low-temperature fixability can be obtained even in a high-speed machine used in a production print region. An object of the present invention is to provide a toner for developing an electrostatic image having a core / shell structure having excellent heat resistance and storage stability while having fixing separation performance, and a method for producing the same.

1.
Toner base particles having a core / shell structure in which a shell layer containing a polyester resin is formed on the surface of core particles containing at least a styrene-acrylic resin and a wax, wherein the toner base particles have the following general formula ( 1. A toner for developing an electrostatic image, comprising a higher alcohol represented by 1).
General formula (1)
CH ₃ (CH ₂ ) _x OH
(Wherein x represents an integer of 5 to 17)
2.
2. The electrostatic image developing toner according to 1 above, wherein a higher alcohol represented by the general formula (1) is contained in the shell layer.
3.
In a method for producing an electrostatic charge image developing toner having a core / shell structure,
Producing an aqueous dispersion of core resin fine particles containing at least a styrene-acrylic resin and a wax;
Producing an aqueous dispersion of colorant fine particles;
A step of preparing an aqueous dispersion of resin fine particles for a shell containing a polyester resin and a higher alcohol represented by the following general formula (1);
Mixing the aqueous dispersion of the resin fine particles for core and the aqueous dispersion of the colorant fine particles, adding a flocculant and heating to produce core particles;
Next, a method for producing a toner for developing an electrostatic charge image, comprising mixing the resin fine particle dispersion for a shell, adding an aggregating agent, and heating to form toner base particles.
General formula (1)
CH ₃ (CH ₂ ) _x OH
(Wherein x represents an integer of 5 to 17)

  According to the present invention, it is possible to form a thin, uniform shell layer, and to obtain an electrostatic charge image developing toner excellent in low-temperature fixability and fixing separation performance and excellent in heat-resistant storage stability. be able to.

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

The present invention relates to a toner for developing an electrostatic charge image and a method for producing the same, and contains a polyester resin and a higher alcohol represented by the following general formula (1) on a core particle surface containing at least a styrene-acrylic resin and a wax. The present invention relates to an electrostatic charge image developing toner having a core / shell structure having a shell layer and a method for producing the same.
General formula (1)
CH ₃ (CH ₂ ) _x OH
(Wherein x represents an integer of 5 to 17)
The toner of the present invention is characterized in that the core particles contain styrene-acrylic resin and wax, and the shell layer contains polyester resin and higher alcohol. Here, the reason why the higher alcohol is contained in the shell layer is as follows.

  That is, the advantage of the polyester resin as a toner resin is that a low softening point design can be easily performed while maintaining a glass transition temperature higher than that of a styrene-acrylic resin. For this reason, the polyester resin is a preferable resin in order to achieve both low-temperature fixability, fixing separation performance, and heat-resistant storage stability. However, when a toner is prepared by an emulsion aggregation method, a shell made of a polyester resin can be formed by aggregation on a core made of styrene-acrylic resin. However, as described above, the polyester resin and core particles that constitute the shell layer The styrene-acrylic resin used as the main component of the resin has poor affinity and it is difficult to form a thin and uniform shell layer. In addition, a smooth shell layer having a large unevenness on the surface of the shell layer cannot be formed.

  In order to solve this problem, it is conceivable to contain a highly hydrophilic monomer such as methyl methacrylate as a constituent monomer of the core styrene-acrylic resin. However, when methyl methacrylate is contained, it has an affinity for polyester resin. Although the toner surface becomes smooth and the compatibility between the methyl methacrylate and the wax is poor, the wax is not taken into the toner base particles in the process of forming the shell layer on the core particle surface, so-called wax The phenomenon of spitting out (wax bleeds out) occurs. As a result, the content of wax in the toner is reduced, and the fixing separation performance is deteriorated.

  Therefore, by containing the higher alcohol represented by the general formula (1) in the polyester resin fine particles, the affinity with the styrene-acrylic resin is increased, and the film is a uniform and dense film while being a thin layer. In addition, a shell layer having a smooth surface can be formed, and a desired wax can be contained in the toner base particles.

  This is presumably because the hydrophobic part of the higher alcohol is oriented in the styrene-acrylic resin and the hydrophilic part is oriented in the polyester resin, whereby the activity at the interface between the two can be lowered and the affinity is improved. In addition, higher alcohol is present at the interface between the core made of styrene-acrylic resin and the shell layer made of polyester resin, and the hydrophobic part of the higher alcohol interacts with the wax, so that the wax is discharged in the shell layer forming process. It is considered that the wax was able to be taken into the core particles.

  By adopting the above configuration, the present invention makes it possible to form a shell layer made of a polyester resin that is thin and has a uniform film thickness on a core made of styrene-acrylic resin and wax. It is considered that it has become possible to provide a toner having good fixing property, fixing separation property, and heat resistance and security.

  The configuration of the present invention will be specifically described below.

(Shell layer resin: Polyester resin)
The polyester resin used in the shell layer in the present invention is produced by a polycondensation reaction using a polyester-forming composition comprising a polyvalent carboxylic acid (derivative) and a polyhydric alcohol (derivative) as raw materials. Examples of the polyvalent carboxylic acid derivatives include alkyl esters, acid anhydrides, and acid chlorides of polyvalent carboxylic acids. Examples of the polyhydric alcohol derivatives include ester compounds of polyhydric alcohols and hydroxycarboxylic acids.

  The polyvalent carboxylic acid is a compound containing two or more carboxyl groups in one molecule. Of these, divalent carboxylic acids are compounds containing two carboxyl groups in one molecule. For example, oxalic acid, succinic acid, maleic acid, adipic acid, β-methyladipic acid, azelaic acid, sebacic acid, nonane Dicarboxylic 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, hexahydroterephthalic acid , Malonic acid, pimelic acid, tartaric acid, mucous acid, phthalic acid, isophthalic acid, terephthalic acid, tetrachlorophthalic acid, chlorophthalic acid, nitrophthalic acid, p-carboxyphenylacetic acid, p-phenylenediacetic acid, m-phenylenediglycolic acid , P-phenylene diglycolic acid, o-phenylene diglycol Oxalic 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.

  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.

(Polyester resin polymerization catalyst)
As the catalyst for polymerization of the polyester resin of the present invention, generally known catalysts can be used. Specifically, titanium compounds such as dibutyltin oxide, titanium tetraisopropoxide, titanium tetra tert-butoxide, and octylic acid Examples thereof include tin (II) compounds having no Sn—C bond such as tin, and these are used singly or in combination.

(Glass transition point of polyester resin, molecular weight)
The glass transition point Tg of the polyester resin particles is preferably 40 ° C. or higher and 70 ° C. or lower, more preferably 50 ° C. or higher and 65 ° C. or lower. A Tg of 40 ° C. or higher is preferable because the cohesive strength of the resin itself in the high temperature region is appropriate and hot offset does not occur during fixing. Further, it is preferable that Tg is 70 ° C. or lower because sufficient melting can be obtained and a suitable minimum fixing temperature can be obtained. The glass transition point is a value measured by a method (DSC method) defined in ASTM (American Society for Testing and Materials) D3418-82. Moreover, it is preferable that the weight average molecular weights of the polyester resin to be used are 1500 or more and 60,000 or less, More preferably, it is the range of 3,000 or more and 40,000 or less. A weight average molecular weight of 1,500 or more is preferred because a cohesive force suitable as a binder resin can be obtained and hot offset properties are good. A weight average molecular weight of 60,000 or less is preferable because good hot offset properties and a suitable minimum fixing temperature can be obtained.

  The polyester resin constituting the shell layer of the present invention may be used alone or in combination with other resins. Moreover, you may use the modified polyester resin which combined the unit which consists of a urethane resin, an acrylic resin, etc. to the polyester resin.

  The resin used for the shell layer constituting the toner of the present invention is preferably 1% by mass to 40% by mass, more preferably 3% by mass to 32% by mass of the resin constituting the toner base particles. When the resin for the shell layer is within this range, the core particles can be uniformly covered, so that the heat-resistant storage stability can be satisfied without impairing the low-temperature fixability.

(Resin for core particles: Styrene-acrylic resin)
In the present invention, the core particles contain at least a binder resin and a wax (release agent). The binder resin constituting the core particle is not particularly limited as long as it is conventionally used as a binder resin for an electrophotographic toner, and various resins can be used, or a vinyl resin is used. In particular, styrene-acrylic resin is preferably used. As a method for forming the core particle, it can be produced by a known method, but an emulsion aggregation method in which resin particles dispersed in an aqueous medium and colored particles are aggregated to form core particles is preferably used. When the core particles have a configuration in which resin particles made of styrene-acrylic resin are aggregated / fused, the core particles are usually formed by an emulsion aggregation method. When the emulsion aggregation method is employed, in detail, resin particles and colorant particles obtained by emulsifying and dispersing a polymerizable monomer in an aqueous medium and polymerizing, if necessary, an offset preventive agent such as wax, a charge control agent, a magnetic material. The core particles may be formed by agglomeration / fusion in an aqueous medium together with an additive such as powder, or the polymerizable monomer is added in the presence of an emulsified offset preventive or charge control additive. The core particles may be formed by seed emulsion polymerization in an aqueous medium. The particle diameter of the resin particles is usually preferably in the range of 50 nm to 500 nm in terms of weight average particle diameter. When the shell layer is uniformly formed on the surface of the core particle, it is preferable to employ an emulsion aggregation method. When the emulsion aggregation method is employed, an emulsion dispersion of shell particles can be added to an aqueous dispersion of core particles, and the shell particles can be aggregated / fused on the surface of the core particles.

  Examples of the polymerizable monomer (hereinafter also referred to as a monomer) used in the core particle of the present invention include styrenes such as styrene, methylstyrene, methoxystyrene, ethylstyrene, propylstyrene, butylstyrene, phenylstyrene, and chlorostyrene. Monomer, methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, pentyl acrylate, dodecyl acrylate, stearyl acrylate, ethyl hexyl acrylate, lauryl acrylate, methyl methacrylate, ethyl methacrylate, propyl methacrylate, Acrylic ester monomers such as butyl methacrylate, pentyl methacrylate, dodecyl methacrylate, stearyl methacrylate, ethylhexyl methacrylate, lauryl methacrylate, methacrylate esters Monomer, and the like. Among these, it is preferable to use a styrene monomer in combination with an acrylic acid monomer and a methacrylic acid monomer. A third vinyl monomer can also be used as the polymerizable monomer. Examples of the third vinyl monomer include acid monomers such as acrylic acid, methacrylic acid, maleic anhydride, and vinyl acetate, acrylamide, methacrylamide, acrylonitrile, ethylene, propylene, butylene vinyl chloride, N-vinyl pyrrolidone, and butadiene. It is done. The copolymerization ratio of these polymerizable monomers may be selected so that the glass transition temperature of the resin constituting the obtained core particle is 30 ° C. to 60 ° C., preferably 30 ° C. to 50 ° C. The softening point is 80 ° C to 110 ° C, preferably 90 ° C to 100 ° C. A polyfunctional vinyl monomer may be further used as the polymerizable monomer. Examples of the polyfunctional vinyl monomer include diacrylates such as ethylene glycol, propylene glycol, butylene glycol, and hexylene glycol, and dimethacrylates and trimethacrylates of tertiary or higher alcohols such as divinylbenzene, pentaerythritol, and trimethylolpropane. Etc. The copolymerization ratio of the polyfunctional vinyl monomer to the entire polymerizable monomer is usually 0.001 to 5% by mass, preferably 0.003 to 2% by mass, and more preferably 0.01 to 1% by mass. It is. Although the gel component insoluble in tetrahydrofuran is generated by using the polyfunctional vinyl monomer, the proportion of the gel component in the whole polymer is usually 40% by mass or less, preferably 20% by mass or less.

(Chain transfer agent)
In the present invention, a chain transfer agent may be added together with the polymerizable monomer. The molecular weight of the polymer can be controlled by adding a chain transfer agent. Known chain transfer agents can be used, and examples thereof include alkyl mercaptans and mercapto fatty acid esters. The addition amount of the chain transfer agent varies depending on the desired molecular weight and molecular weight distribution, but specifically, it is preferably added in the range of 0.1 to 5% by mass with respect to the polymerizable monomer.

(Polymerization initiator)
As the polymerization initiator used for the polymerization of the polymerizable monomer in the present invention, a water-soluble polymerization initiator is preferably used. Specifically, for example, hydrogen peroxide, acetyl peroxide, cumyl peroxide, tert-butyl peroxide, propionyl peroxide benzoyl peroxide, chlorobenzoyl peroxide, dichlorobenzoyl peroxide, bromomethylbenzoyl peroxide, peroxide Lauroyl, 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 Oxides; 2, 2 -Azobis (2-aminodipropane) hydrochloride, 2,2'-azobis- (2-aminodipropane) nitrate, 1,1'-azobis (sodium 1-methylbutyronitrile-3-sulfonate), 4 , 4'-azobis-4-cyanovaleric acid, poly (tetraethylene glycol-2,2'-azobisisobutyrate) and other azo compounds.

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

  Specific examples of nonionic surfactants include dodecyl polyoxyethylene ether, hexadecyl polyoxyethylene ether, norylphenyl polyoxyethylene ether, lauryl polyoxyethylene ether, sorbitan monooleate polyoxyethylene ether, styrylphenyl poly Examples thereof include oxyethylene ether and monodecanoyl sucrose.

  Specific examples of the anionic surfactant include aliphatic soaps such as sodium stearate and sodium laurate, sodium lauryl sulfate, sodium dodecylbenzene sulfonate, polyoxyethylene (2) sodium lauryl ether sulfate and the like. it can.

(wax)
Examples of the wax contained in the core particles constituting the toner of the present invention include hydrocarbon waxes such as low molecular weight polyethylene wax, low molecular weight polypropylene wax, Fischer-Tropsch wax, microcrystalline wax, and paraffin wax, and carnauba wax. And ester waxes such as pentaerythritol behenate, behenyl behenate and behenyl citrate. 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, more preferably 4 to 15% by mass, based on the total mass of the core. 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.

(Higher alcohol)
The higher alcohol used in the present invention is an aliphatic alcohol having 6 or more carbon atoms and is represented by the following formula (1).

General formula (1)
CH ₃ (CH ₂ ) _x OH
In the formula, x is 5 or more and 17 or less, preferably 11 or more and 17 or less. If it is less than 5, the affinity is insufficient and a shell layer cannot be formed. If it is larger than 17, the toner surface becomes smooth, but the compatibility proceeds so much that heat-resistant storage stability cannot be ensured. Although it may be contained in the core, it is preferably contained in the shell. Moreover, as content, 0.5 mass%-10 mass% are preferable in resin for shell layers, More preferably, it is 0.5 mass%-5 mass%. Within this range, the affinity is sufficient, a uniform and smooth shell layer can be formed, and low temperature fixability and heat resistant storage stability can be ensured, which is preferable. Specific examples of the higher alcohol represented by the general formula (1) include hexanol, heptanol, octanol, lauryl alcohol, stearyl alcohol, and the like.

(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. Although the toner base particles can be used as toners as they are, it is usually preferable to use them as toner particles by adding an external additive. The toner is an aggregate of toner particles.

(Circularity of toner base particles)
First, the average circularity of the toner base particles used in the present invention will be described. The average circularity of the toner base 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 base particles are moistened in a surfactant aqueous solution, and ultrasonic dispersion is performed for 1 minute. After dispersion, the HPF is used in the measurement condition HPF (high magnification imaging) mode using “FPIA-2100”. Measurement is performed at an appropriate concentration of 3000 to 10,000 detections. Within this range, reproducible measurement values can be obtained. The circularity is calculated by the following formula (1).

Formula (1)
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 base particles)
Next, the particle diameter of the toner base particles used in the present invention will be described. The toner particles used in the present invention preferably have a volume-based median diameter (D ₅₀ ) of 3 μm or more and 10 μm or less. By setting the volume reference median diameter in the above range, for example, it is possible to faithfully reproduce a very minute dot image at a level of 1200 dpi (dpi; number of dots per inch (2.54 cm)). The volume-based median diameter (D ₅₀ ) of the toner base particles can be measured and calculated using, for example, an apparatus 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 and 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 base particles) Then, 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.

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

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

  In the agglomeration step, an aqueous dispersion of resin particles is mixed with a dispersion of colorant particles, wax particles, charge control agent particles, and other toner constituent particles to prepare an agglomeration dispersion liquid 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.

  Moreover, in the fusion | melting process, it is preferable to raise temperature rapidly by heating, and it is preferable that a temperature increase rate shall be 1 degree-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.

  The toner particles having a core / shell structure of the present invention can be obtained by an emulsion aggregation method. First, the binder resin fine particles for the core particles and the colorant fine particles are aggregated and fused to produce core particles, and then the binder resin fine particles for the shell layer are added to the core particle dispersion to obtain the core. It can be obtained by aggregating and fusing the binder resin fine particles for the shell layer on the particle surface to form a shell layer covering the core particle surface.

Next, a method for producing toner particles having a core / shell structure will be described.
(1) Step of preparing a core resin fine particle dispersion in which core binder resin fine particles containing wax are dispersed in an aqueous medium (2) Colorant dispersion in which colorant fine particles are dispersed in an aqueous medium Step of preparing liquid (3) Step of preparing resin fine particle dispersion for shell layer in which resin fine particles for shell layer are dispersed in an aqueous medium (4) Resin fine particle dispersion for core and colorant dispersion Then, a coagulant is added to produce core particles, and then a resin fine particle dispersion for shell layer is added to form a shell layer on the surface of the core particles to produce core-shell toner base particles. Step (5) Step of filtering and washing the toner base particles having the core / shell structure (6) Step of drying the toner base particles and adding an external additive to prepare a toner The resin fine particles for core of (1) Make dispersion As a method for dispersing the core binder resin fine particles in the process, it is preferable to use an emulsion polymer particle dispersion obtained by emulsion polymerization. The core binder resin fine particles may have a multilayer structure of two layers or three or more layers made of binder resins having different compositions. For the binder resin fine 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).

  A method of preparing a resin fine particle dispersion for a shell layer dispersed in an aqueous medium of a polyester resin is as follows. A polyester resin is dissolved in an organic solvent such as ethyl acetate, and then dispersed in water to which a surfactant is added, and then the organic solvent is stored. Can be obtained by leaving.

  In this step, a solution in which a polyester resin and a higher alcohol are dissolved in an organic solvent is added to an aqueous medium, and then a dispersion treatment is performed by the action of mechanical energy by a known method to form polyester resin oil droplets. The dispersion device for dispersing oil droplets by mechanical energy is not particularly limited. For example, a commercially available stirring device “CLEARMIX” (manufactured by M Technique Co., Ltd.) equipped with a rotor that rotates at high speed, etc. Is a typical device. In addition to the agitation device described above, examples include an ultrasonic disperser, a mechanical homogenizer, a manton gourin, and a pressure homogenizer. With these devices, dispersed particles of oil droplets of around 100 nm can be formed in an aqueous medium, and then the organic solvent is distilled off to obtain a fine particle dispersion of polyester resin.

  The “aqueous medium” as used in the present invention is a liquid composed of water and an organic solvent soluble in water, and contains at least 50% by mass of water. Here, examples of the organic solvent that can be dissolved in water that is a component other than water constituting the aqueous medium include methanol, ethanol, isopropanol, butanol, acetone, methyl ethyl ketone, and tetrahydrofuran. Among these, alcohol-based organic solvents such as methanol, ethanol, isopropanol, and butanol, which are organic solvents that do not dissolve the resin, are preferable.

(Coloring agent)
As the colorant to be used, carbon black, magnetic substance, dye, pigment, etc. can be arbitrarily used, and as channel black, furnace black, acetylene black, thermal black, lamp black, etc. are used as carbon black. . As the magnetic material, ferromagnetic metals such as iron, nickel and cobalt, alloys containing these metals, and compounds of ferromagnetic metals such as ferrite and magnetite can be used. As the dye, C.I. I. Solvent Red 1, 49, 52, 58, 63, 111, 122, C.I. I. Solvent Yellow 19, 44, 77, 79, 81, 82, 93, 98, 103, 104, 112, 162, C.I. I. Solvent Blue 25, 36, 60, 70, 93, 95, etc. can be used, and mixtures thereof can also be used. Examples of the pigment include C.I. I. Pigment Red 5, 48: 1, 48: 3, 53: 1, 57: 1, 81: 4, 122, 139, 144, 149, 166, 177, 178, 222, C.I. I. Pigment Orange 31 and 43, C.I. I. Pigment Yellow 14, 17, 74, 93, 94, 138, 155, 180, 185, C.I. I. Pigment green 7, C.I. I. Pigment Blue 15: 3, 15: 4, 60, and the like, and a mixture thereof can also be used. The number average primary particle diameter varies depending on the type, but is preferably about 10 to 200 nm.

(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.

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

(External additive)
In the present invention, an external additive can be added for the purpose of improving the fluidity and charging characteristics of the toner. Examples of the external additive used in the present invention include inorganic oxide fine particles such as silica fine particles, alumina fine particles, and titanium oxide fine particles, inorganic stearate compound fine particles such as aluminum stearate fine particles and zinc stearate fine particles, or strontium titanate. And inorganic fine particles such as inorganic titanic acid compound fine particles such as zinc titanate. These inorganic fine particles are preferably those subjected to surface treatment with a silane coupling agent, a titanium coupling agent, a higher fatty acid, silicone oil, or the like from the viewpoint of heat-resistant storage stability and environmental stability. The addition amount of the external additive is 0.05 to 5 parts by mass, preferably 0.1 to 3 parts by mass with respect to 100 parts by mass of the toner base particles. Various external additives may be used in combination. Examples of the method for adding the external additive include a dry method in which the external additive is added in powder form to the dried toner base particles. Examples of the mixing device include mechanical mixing devices such as a Henschel mixer and a coffee mill. It is done.

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

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

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples. The toner of the present invention was prepared by the following procedure.
(1) Preparation of core resin particle A dispersion (2) Adjustment of shell resin particle B dispersion (3) Aggregation / fusion-external additive treatment step
(1) Adjustment of core resin particle A1 dispersion (1-1) First stage polymerization An anionic surfactant “in advance” in a reaction vessel equipped with a stirrer, a temperature sensor, a temperature controller, a cooling pipe and a nitrogen introducing device. An anionic surfactant solution prepared by dissolving 2.0 parts by mass of sodium lauryl sulfate in 2900 parts by mass of ion-exchanged water was added, and the internal temperature was raised to 80 ° C. while stirring at a stirring speed of 230 rpm under a nitrogen stream. It was. After adding 9.0 parts by mass of a polymerization initiator “potassium persulfate: KPS” to this surfactant solution and adjusting the internal temperature to 78 ° C.,
Solution (1)
Styrene 540 parts by weight n-butyl acrylate 270 parts by weight Methacrylic acid 65 parts by weight n-octyl mercaptan 17 parts by weight of solution (1) was added dropwise over 3 hours, and after completion of the addition, heating and stirring at 78 ° C. for 1 hour Thus, polymerization (first stage polymerization) was performed to prepare a dispersion of “resin fine particles (a1)”.

(1-2) Second-stage polymerization: formation of intermediate layer In a flask equipped with a stirrer,
Solution (2)
Styrene 94 parts by weight n-butyl acrylate 60 parts by weight Methacrylic acid 11 parts by weight n-octyl mercaptan 5 parts by weight Paraffin wax (melting point: 73 ° C.) 51 parts by weight is added as a release agent, A monomer solution (2) was prepared by heating to 85 ° C. and dissolving. On the other hand, a surfactant solution in which 2 parts by mass of the anionic surfactant “sodium lauryl sulfate” was dissolved in 1100 parts by mass of ion-exchanged water was heated to 90 ° C., and “resin fine particles (a1)” was added to this surfactant solution. Is added in an amount of 28 parts by mass in terms of solid content of the resin fine particles (a1), and then the monomer solution (Cleamix) (manufactured by M Technique Co., Ltd.) having a circulation path is used. 2) is mixed and dispersed for 4 hours to prepare a dispersion containing emulsified particles having a dispersed particle diameter of 350 nm. In this dispersion, 2.5 parts by mass of the polymerization initiator “KPS” is dissolved in 110 parts by mass of ion-exchanged water. The initiator aqueous solution was added, and this system was heated and stirred at 90 ° C. for 2 hours to perform polymerization (second stage polymerization) to prepare a dispersion of “resin fine particles (a11)”.

(1-3) Third-stage polymerization: formation of outer layer Start of dissolving 2.5 parts by mass of polymerization initiator “KPS” in 110 parts by mass of ion-exchanged water in the dispersion of “resin fine particles (a11)” Aqueous agent aqueous solution is added and under the temperature condition of 80 ° C.
Solution (3)
Styrene 230 mass parts n-butyl acrylate 100 mass parts n-octyl mercaptan Solution (3) which consists of 5.2 mass parts was dripped over 1 hour. After completion of the dropwise addition, polymerization (third stage polymerization) was carried out by heating and stirring for 3 hours. Then, it cooled to 28 degreeC and produced "the dispersion liquid of core resin particle A1" in which the resin particle A for cores disperse | distributed in the anionic surfactant solution.
(2) Adjustment of Shell Resin Particle B1 Dispersion (2-1) Adjustment of Shell Resin Particle B1 Dispersion << Preparation of Polyester Resin >>
In a reaction vessel equipped with a cooling pipe, a stirrer and a nitrogen introduction pipe, 316 parts by mass of a bisphenol A propylene oxide 2-mole adduct, 80 parts by mass of terephthalic acid, 34 parts by mass of maleic anhydride, and titanium tetraisosodium as a polycondensation catalyst. 2 parts by mass of propoxide was divided into 10 portions and reacted at 200 ° C. for 10 hours while distilling off the water generated under a nitrogen stream. Subsequently, it was made to react under reduced pressure of 13.3 kPa (100 mmHg), and it took out when the softening point became 104 degreeC, and obtained resin B1 for shells. The shell resin B1 had a Tg of 65 ° C., a number average molecular weight of 4500, and a weight average molecular weight of 13500.

≪Preparation of polyester resin particle dispersion≫
100 parts by mass of the obtained “resin B1 for shell” and 1 part by mass of lauryl alcohol were dissolved in 400 parts by mass of ethyl acetate (manufactured by Kanto Chemical Co., Inc.), and a 0.26 mass% sodium lauryl sulfate solution prepared in advance was prepared. After mixing with 638 parts by mass and ultrasonically dispersing with V-LEVEL 300 μA for 30 minutes with an ultrasonic homogenizer “US-150T” (manufactured by Nippon Seiki Seisakusho) with stirring, the diaphragm vacuum pump is heated to 40 ° C. Using V-700 (manufactured by BUCHI), ethyl acetate was completely removed while stirring under reduced pressure for 3 hours, and the average particle diameter (median diameter (D ₅₀ ) based on volume) containing lauryl alcohol was 160 nm. A “polyester resin particle dispersion (shell resin particle B1 dispersion)” having a solid content of 13.5% by mass was obtained.

(2-2) Adjustment of Shell Resin Particles B2 to B10 Dispersion A shell resin particle B2 to B10 dispersion was prepared in the same manner except that the higher alcohol species and amount used were changed as shown in Table 1.
(3) Aggregation / Fusion to External Additive Processing Step << Production of Toner >>
<Preparation of colorant dispersion>
90 parts by mass of sodium dodecyl sulfate was dissolved in 1600 parts by mass of ion-exchanged water with stirring. While stirring this solution, 420 parts by mass of carbon black “Mogal L” (manufactured by Cabot) is gradually added, and then dispersed using a stirrer “Claremix” (manufactured by M Technique). A colorant dispersion having dispersed colorant particles was prepared. The particle diameter of this dispersion was measured using a Microtrac particle size distribution analyzer UPA-150 (manufactured by Nikkiso Co., Ltd.) and found to be 117 nm.

<Preparation of Toner 1>
Into a reaction vessel equipped with a stirrer, a temperature sensor, and a cooling tube, 288 parts by mass of the dispersion of “core resin particles A1” and 2000 parts by mass of ion-exchanged water in terms of solid content are added, and then 5 mol / liter of water is added. An aqueous sodium oxide solution was added to adjust the pH to 10. Thereafter, 40 parts by mass of “colorant dispersion” was added in terms of solid content. Next, an aqueous solution in which 60 parts by mass of magnesium chloride was dissolved in 60 parts by mass of ion-exchanged water was added over 10 minutes at 30 ° C. with stirring. Thereafter, the temperature was raised after being allowed to stand for 3 minutes, and the temperature of the system was raised to 80 ° C. over 60 minutes, and the particle growth reaction was continued while maintaining 80 ° C. In this state, the particle size of the associated particles was measured with “Coulter Multisizer 3” (manufactured by Coulter Beckman). When the median diameter (D ₅₀ ) on the volume basis became 6.0 μm, “resin particles for shell” When 72 parts by mass of the dispersion of “B1” was added over 30 minutes in terms of solid content, and the supernatant of the reaction solution became transparent, an aqueous solution in which 190 parts by mass of sodium chloride was dissolved in 760 parts by mass of ion-exchanged water was added. Addition to stop grain growth. Further, the temperature is raised and the mixture is heated and stirred in a state of 90 ° C. to advance the fusing of the particles, and the average circularity measurement apparatus “FPIA-2100” (manufactured by Sysmex) is used (HPF detection). When the average circularity reached 0.945, the mixture was cooled to 30 ° C. to prepare “Toner Base Particle Dispersion 1”.

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

(External additive treatment process)
1% by mass of hydrophobic silica (number average primary particle size = 12 nm) and 0.3% by mass of hydrophobic titania (number average primary particle size = 20 nm) are added to the “toner base particle [1]”, and Henschel is added. “Toner 1” was prepared by mixing with a mixer.

<Preparation of Toners 2-14>
“Toners 2 to 14” were produced in the same manner except that the types and parts by mass of “core resin particles A” and “shell resin particles B” used in the production of toner 1 were changed as shown in Table 1. .

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

  Toner was added to the carrier so that the toner concentration would be 6% by mass, and the toner was put into a micro V-type mixer (Tsujii Chemical Co., Ltd.) and mixed at a rotational speed of 45 rpm for 30 minutes to produce a developer.

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

A: Lower limit fixing temperature is less than 150 ° C. O: Lower limit fixing temperature is 150 ° C. or higher and lower than 160 ° C. Δ: Lower limit fixing temperature is 160 ° C. or higher and lower than 170 ° C. X: Lower limit fixing temperature is 170 ° C. or higher. .5 g in a 10 ml glass bottle with an inner diameter of 21 mm, the lid closed, shaken 600 times at room temperature with Tap Denser KYT-2000 (manufactured by Seishin Enterprise), and the environment removed at 55 ° C. and 35% RH with the lid removed. Left for 2 hours. 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 equation (2).

Formula (2)
Toner aggregation rate (%) = residual toner mass on sieve (g) /0.5 (g) × 100
The heat resistant storage stability of the toner was evaluated according to the criteria described below.

A: The toner aggregation rate is less than 10% by mass (the 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: Toner aggregation rate of 15% by mass or more and less than 20% by mass (toner heat-resistant storage stability is somewhat poor) ×: Toner aggregation rate of 20% by mass or more (toner heat-resistant storage stability is poor and cannot be used)
(3) Fixing Separation Image The fixing roller on the image side when the surface temperature of the fixing heat roller is 180 ° C. and an A4 image having a solid black belt image having a width of 5 cm in the direction perpendicular to the conveying direction is conveyed by vertical feeding. Separability between paper and paper was determined according to the following evaluation criteria.

◎: Paper separates from fixing roller without curling ○: Paper separates from fixing roller and separation claw, but traces of separation claw are hardly noticeable on image △: Paper separates from fixing roller and separation claw However, separation nail marks remain on the image. X: The paper is wound around the fixing roller and cannot be separated from the fixing roller. Table 2 shows the above evaluation results.

  As is apparent from the results in Table 2, the toners (toners 1 to 11) of the present invention have extremely excellent characteristics in terms of low-temperature fixing properties, heat-resistant storage properties, and fixing separation properties as compared with comparative toners (toners 12 to 14). It can be seen that

Claims (3)

Toner base particles having a core / shell structure in which a shell layer containing a polyester resin is formed on the surface of core particles containing at least a styrene-acrylic resin and a wax, wherein the toner base particles have the following general formula ( 1. A toner for developing an electrostatic image, comprising a higher alcohol represented by 1).
General formula (1)
CH ₃ (CH ₂ ) _x OH
(Wherein x represents an integer of 5 to 17)   The electrostatic image developing toner according to claim 1, wherein the higher alcohol represented by the general formula (1) is contained in the shell layer. In a method for producing an electrostatic charge image developing toner having a core / shell structure,
Producing an aqueous dispersion of core resin fine particles containing at least a styrene-acrylic resin and a wax;
Producing an aqueous dispersion of colorant fine particles;
A step of preparing an aqueous dispersion of resin fine particles for a shell containing a polyester resin and a higher alcohol represented by the following general formula (1);
Mixing the aqueous dispersion of the resin fine particles for core and the aqueous dispersion of the colorant fine particles, adding a flocculant and heating to produce core particles;
Next, a method for producing a toner for developing an electrostatic charge image, comprising mixing the resin fine particle dispersion for a shell, adding an aggregating agent, and heating to form toner base particles.
General formula (1)
CH ₃ (CH ₂ ) _x OH
(Wherein x represents an integer of 5 to 17)