JP5639859B2 - Method for producing toner for electrophotography - Google Patents

Description

  The present invention relates to a method for producing an electrophotographic toner and an electrophotographic toner obtained thereby.

In the field of electrophotographic toner, with development of an electrophotographic system, development of a toner corresponding to high image quality and high speed is required.
In order to meet the demands for higher image quality and higher speed, toners are also required to have various performances. In addition, as a method capable of arbitrarily adjusting the surface property, a toner production method by an emulsion aggregation method has been proposed.

For example, Patent Document 1 discloses a toner for developing an electrostatic image containing a specific crystalline resin, an amorphous polymer, and a metal salt for the purpose of low-temperature fixing and chargeability improvement.
In Patent Document 2, composite resin particles formed from a polymerizable monomer and a crystalline organic compound are colored and colored for the purpose of storage stability, fixing characteristics, and suppression of fluctuations in charge amount and development density due to high and low humidity. An electrostatic latent image developing toner containing two or more inorganic salts having different valences obtained by salting out / fusing agent particles with a specific content is disclosed.
In Patent Document 3, for the purpose of obtaining a toner having a sharp particle size, particle size distribution, and charge distribution and having a stable charge amount, particle growth by salting out / aggregation is carried out on resin particles in a dispersion containing resin particles. For developing an electrostatic latent image having a step of adding a salting-out stopping agent composed of a salt having a valence smaller than that of the salting-out agent when the salting-out agent for starting is added and the particles grow to a predetermined particle size A method for producing toner is disclosed.
In Patent Document 4, a monovalent metal salt is added to an aqueous dispersion containing polymer fine particles and colorant fine particles for the purpose of obtaining a toner having excellent charging characteristics and fluidity by controlling the particle size and the like. In the method for producing a toner, in which an aggregating agent and a stabilizer are added and the associated particles are thermally fused at a temperature equal to or higher than the glass transition temperature of the polymer fine particles, at least one of the aggregating agent and the stabilizer during the thermal fusing A method for producing a toner for developing an electrostatic image, wherein the density is changed, is disclosed.
In Patent Document 5, for the purpose of obtaining a toner having high image density, low fog, good transfer rate and halftone uniformity, and excellent fine line reproducibility, An electrostatic charge image developing toner produced through a process of salting out, aggregating and fusing the resin particles in the presence of a specific surfactant is disclosed.

JP 2005-266317 A JP 2003-66646 A JP 2003-66648 A JP 2000-131882 A Japanese Patent Laid-Open No. 2002-131978

By using a release agent in the toner, the fixability of the resulting toner can be improved due to its melting characteristics. However, the release agent has poor compatibility with the binder resin and colorant of the toner, and in the toner by the emulsion aggregation method, the release agent may be released or exposed to the toner surface due to heat at a time. There's a problem. These are considered to be the cause of poor durability that causes phenomena such as filming and the cause of deterioration in storage stability such as the formation of massive aggregates during storage. In order to prevent the release agent from being exposed, contrivances such as providing a shell layer by a multi-stage emulsion aggregation method have been made, but it is still insufficient.
An object of the present invention is to provide an electrophotographic toner having both excellent durability and storage stability, and a method for producing the same.

  The inventors of the present invention considered that the factors affecting the fixability, durability, and storage stability are the state and location of the resin and release agent constituting the toner in the toner. As a result, the colored particles and release agent particles are used as the core part, the particles are aggregated so that the resin containing amorphous polyester becomes the shell part, and a salt having a cation having a higher valence than the aggregating agent is added. Thus, it has been found that by fusing in a specific temperature region, an electrophotographic toner having a core-shell type structure having excellent fixability and excellent durability and storage stability can be obtained.

That is, the present invention provides the following [1] and [2].
[1] A method for producing an electrophotographic toner comprising the following steps (1) to (4):
Step (1): A step of mixing a flocculant composed of colored particles, release agent particles, and an electrolyte in an aqueous medium to obtain an agglomerated particle dispersion Step (2): An amorphous polyester is added to the agglomerated particle dispersion. A step of adding a resin particle (B) containing (b) to obtain a core-shell particle dispersion (1) Step (3): A cation having a higher valence than the flocculant is added to the core-shell particle dispersion (1). Step of obtaining a core-shell particle dispersion (2) by adding a salt thereof Step (4): The core-shell particle dispersion (2) is not higher than the melting point of the release agent, and the glass transition point of the amorphous polyester (b) A process for obtaining a core-shell particle dispersion (3a) by maintaining the temperature at a temperature lower by 5 ° C. or higher [2] An electrophotographic toner obtained by the production method of [1].

  According to the present invention, it is possible to provide an electrophotographic toner that is excellent in fixability and can achieve both good durability and storage stability, and a method for producing the same.

<Method for producing electrophotographic toner>
The method for producing an electrophotographic toner of the present invention includes the following steps (1) to (4).
Step (1): A step of mixing a flocculant composed of colored particles, release agent particles, and an electrolyte in an aqueous medium to obtain an agglomerated particle dispersion Step (2): An amorphous polyester is added to the agglomerated particle dispersion. A step of adding a resin particle (B) containing (b) to obtain a core-shell particle dispersion (1) Step (3): A cation having a higher valence than the flocculant is added to the core-shell particle dispersion (1). Step of obtaining a core-shell particle dispersion (2) by adding a salt thereof Step (4): The core-shell particle dispersion (2) is not higher than the melting point of the release agent, and the glass transition point of the amorphous polyester (b) A step of obtaining a core-shell particle dispersion (3a) by maintaining the temperature at a temperature of 5 ° C. or lower.

The reason why the electrophotographic toner obtained by the production method of the present invention is excellent in fixability and can achieve both good durability and storage stability is not clear, but is considered as follows.
First, in the step (1), the core portion containing the colored particles and the release agent particles is formed by aggregating the colored particles and the release agent particles with an aggregating agent.
Next, in the step (2), the resin particles (B) containing the amorphous polyester (b) are added to form a shell portion, and core-shell structured particles are formed. Thereafter, when the toner has grown to an appropriate particle size, an aqueous solvent is added to lower the concentration of the flocculant, or a surfactant is added as an aggregation stopper to stop the aggregation.
In the present invention, a salt having a cation having a higher valence than the flocculant is further added in the step (3). It is considered that the aggregated state of the aggregated particles is strengthened by adding the salt.
In this state, in the fusion step of step (4), coloring is performed by maintaining the temperature at a temperature lower than the melting point of the release agent and 5 ° C. lower than the glass transition point of the amorphous polyester in the shell portion The fused state of the particles and resin particles is sufficient, and release of the release agent particles and exposure to the surface of the release agent particles are suppressed, and toner particles whose surface is uniformly covered with amorphous polyester can be obtained. It is considered a thing.
As a result, it is considered that the melting characteristics of the release agent contained in the core portion can be fully utilized, and the storage stability of the toner is improved while maintaining excellent fixing properties.
Further, since the core portion and the shell portion are sufficiently fused, the obtained toner is considered to have excellent durability without causing filming or the like even during long-time printing.

First, each component used in the present invention will be described.
[Colored particles]
The colored particles used in the present invention are particles containing a colorant. The colorant obtained by dispersing in an aqueous medium by subjecting the colorant to surface treatment or using a dispersant. Particles may be used, and colorant-containing resin particles obtained by adding a colorant to resin particles as described below may be used. Among these, from the viewpoint of suppressing the generation of coarse particles during aggregation, colorant-containing resin particles containing a colorant (hereinafter also referred to as “colorant-containing resin particles (A)”) are preferable.
When the color particles are colorant-containing resin particles (A), the content of the colorant is preferably from 100 parts by weight of the resin constituting the colorant-containing resin particles (A) from the viewpoint of the image density of the toner. Is 1 to 20 parts by weight, more preferably 3 to 15 parts by weight, still more preferably 5 to 10 parts by weight.

(Coloring agent)
As the colorant, pigments and dyes are used, and pigments are preferable from the viewpoint of image density of the toner.
Specific examples of the pigment include carbon black, inorganic composite oxide, chrome yellow, benzidine yellow, brilliantamine 3B, brilliantamine 6B, Bengal, aniline blue, ultramarine blue, copper phthalocyanine, phthalocyanine green, and the like. From the viewpoint of image density, copper phthalocyanine is preferable.
Specific examples of the dye include acridine series, azo series, benzoquinone series, azine series, anthraquinone series, indico series, phthalocyanine series, and aniline black series.
A coloring agent can be used individually or in combination of 2 or more types.

(Colorant-containing resin particles (A))
In the present invention, the resin constituting the colorant-containing resin particles (A) (hereinafter also simply referred to as “resin particles (A)”) contains a crystalline polyester (a) from the viewpoint of low-temperature fixability of the toner. It is preferable.
The content of the crystalline polyester (a) in the resin particles (A) is preferably 1 with respect to the resin constituting the resin particles (A) from the viewpoint of improving the low-temperature fixability of the toner and preventing hot offset. -50% by weight, more preferably 7-50% by weight, still more preferably 10-40% by weight, still more preferably 13-30% by weight.

The resin particles (A) preferably further contain an amorphous polyester (c) from the viewpoint of improving storage stability and durability while maintaining the low-temperature fixability of the toner and preventing hot offset.
The total amount of the crystalline polyester (a) and the amorphous polyester (c) in the resin particles (A) is the resin particles (from the viewpoint of improving storage stability and durability while maintaining the low-temperature fixability of the toner. In the resin constituting A), it is preferably 50 to 100% by weight, more preferably 80 to 100% by weight, still more preferably 90 to 100% by weight, still more preferably substantially 100% by weight.
The weight ratio ((a) / (c)) between the crystalline polyester (a) and the amorphous polyester (c) in the resin particles (A) is the storage stability and durability while maintaining the low-temperature fixability of the toner. From the viewpoint of improving the property and preventing hot offset, preferably 5/95 to 50/50, more preferably 5/95 to 40/60, more preferably 10/90 to 30/70, and still more preferably 13/87. ~ 20/80.

The resin particle (A) is a resin other than the crystalline polyester (a) and the amorphous polyester (c), for example, a styrene acrylic copolymer, an epoxy resin, a polycarbonate, a polyurethane, etc., as long as the effects of the present invention are not impaired. The resin may be contained.
In addition, the resin particles (A) may contain a release agent and a charge control agent as long as the effects of the present invention are not impaired. If necessary, reinforcing fillers such as fibrous substances, antioxidants, and the like. You may contain additives, such as an agent and an antioxidant.

(Crystalline polyester (a))
In the present invention, the crystalline polyester (a) is the ratio between the softening point and the maximum endothermic peak temperature measured by the differential scanning calorimeter (DSC) [(softening point (° C)) / (maximum endothermic peak temperature (° C)]. )] Is a crystallinity index defined by 0.6 to 1.4. This crystallinity index is preferably 0.8 to 1.3, more preferably 0.9 to 1.2, and still more preferably 0.9 to 1.1 from the viewpoint of low-temperature fixability of the toner.
The crystalline polyester (a) preferably has an acid group at the molecular end from the viewpoint of emulsifiability. Examples of the acid group include a carboxyl group, a sulfonic acid group, a phosphonic acid group, and a sulfinic acid. Among these, a carboxyl group is preferable from the viewpoints of resin dispersibility and toner storage stability.

The melting point of the crystalline polyester (a) is preferably from 50 to 150 ° C., more preferably from 55 to 130 ° C., still more preferably from 60 to 120 ° C., further preferably from the viewpoint of low-temperature fixability and storage stability of the toner. ~ 80 ° C.
The softening point of the crystalline polyester (a) is preferably from 50 to 140 ° C., more preferably from 55 to 130 ° C., still more preferably from 60 to 110 ° C., further preferably from the viewpoint of low-temperature fixability and storage stability of the toner. 60-85 ° C.
The number average molecular weight of the crystalline polyester (a) is preferably 1,500 to 50,000, more preferably 2,000 to 10,000, and still more preferably 3 from the viewpoint of low-temperature fixability and storage stability of the toner. , 500 to 8,000.
In addition, crystalline polyester (a) can be used individually or in combination of 2 or more types.
In the present invention, the melting point, softening point and number average molecular weight of the crystalline polyester (a) are determined by the methods described in the examples. When two or more crystalline polyesters (a) are used in combination, the melting point is the melting point of the crystalline polyester (a) having the largest weight ratio in the crystalline polyester (a) contained in the obtained toner. The melting point of the crystalline polyester (a) is set to the lowest value when all have the same ratio. A softening point and a number average molecular weight are calculated | required by the method as described in an Example as a mixture of crystalline polyester (a).

The crystalline polyester (a) can be obtained by polycondensation reaction between an acid component and an alcohol component. The polycondensation reaction is preferably performed at 140 to 200 ° C. in the presence of a catalyst.
Examples of the acid component include aliphatic dicarboxylic acids, alicyclic dicarboxylic acids, aromatic dicarboxylic acids, and trivalent or higher polyvalent carboxylic acids. Examples of carboxylic acids include acid anhydrides and alkyls (1 to 3 carbon atoms). Esters are also included. Among these, aliphatic dicarboxylic acids are preferable from the viewpoint of low-temperature fixability and storage stability of the toner.
Aliphatic dicarboxylic acids include oxalic acid, malonic acid, maleic acid, fumaric acid, citraconic acid, itaconic acid, glutaconic acid, succinic acid, adipic acid, sebacic acid, 1,12-dodecanedioic acid, azelaic acid, n- Examples thereof include dodecyl succinic acid and n-dodecenyl succinic acid. Among these, aliphatic dicarboxylic acids having 9 to 12 carbon atoms are preferable from the viewpoint of low-temperature fixability and storage stability of the toner, and sebacic acid and 1,12-dodecane are preferable. Diacid is more preferable, and sebacic acid is still more preferable.
These acid components can be used alone or in combination of two or more.

Examples of the alcohol component include aliphatic diols having 2 to 12 carbon atoms in the main chain, aromatic diols, hydrogenated products of bisphenol A, and trihydric or higher polyhydric alcohols. Among these, the crystallinity of polyester is promoted. From the viewpoint of improving the low-temperature fixability of the toner, an aliphatic diol having 2 to 12 main chain carbon atoms is preferred.
Among the aliphatic diols having 2 to 12 main chain carbon atoms, α, ω-linear alkanediols are preferable from the viewpoint of promoting the crystallinity of the polyester and improving the low-temperature fixability of the toner. 12 is more preferable.
Examples of the α, ω-linear alkanediol include ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1 , 7-heptanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 1,12-dodecanediol, etc. Among these, low-temperature fixability and storage stability of the toner From this viewpoint, 1,6-hexanediol and 1,9-nonanediol are preferable.
Examples of other aliphatic diols having 2 to 12 carbon atoms in the main chain include neopentyl glycol and 1,4-butenediol.

  These alcohol components can be used singly or in combination of two or more. From the viewpoint of promoting the crystallinity of the polyester, the alcohol component has an aliphatic diol having 2 to 12 carbon atoms in the main chain. It is preferably 100 mol%, more preferably 90 to 100 mol%, and still more preferably substantially 100 mol%.

As a catalyst, a tin compound, a titanium compound, etc. are preferable from a viewpoint of the efficiency of a condensation polymerization reaction, and a tin compound is more preferable. Examples of tin compounds include tin dioctanoate and dibutyltin oxide. Examples of the titanium compound include titanium diisopropylate bistriethanolamate.
Although there is no restriction | limiting in the usage-amount of a catalyst, Preferably it is 0.01-1 weight part with respect to 100 weight part of total amounts of an acid component and an alcohol component, More preferably, it is 0.1-0.6 weight part.

  The polycondensation reaction is preferably performed by adding an acid component and an alcohol component to a reaction vessel and maintaining at 140 to 200 ° C. for 5 to 15 hours, and then adding a catalyst and maintaining at 140 to 200 ° C. for 1 to 5 hours. More preferably, the reaction is allowed to proceed, and the pressure is reduced to 5.0 to 20 kPa and maintained for 1 to 10 hours.

(Amorphous polyester (c))
As the amorphous polyester (c) that can be contained in the resin particles (A), a resin having the same composition as the amorphous polyester (b) described later may be used, or a resin having a different composition may be used. From the viewpoint of control of the flocculant and durability, it is preferable to use resins having the same composition.

The amorphous polyester (c) can be produced by subjecting an acid component and an alcohol component to a polycondensation reaction. The acid component and the alcohol component are preferably the same components as the amorphous polyester (b).
Examples of the acid component include a dicarboxylic acid, a succinic acid substituted with an alkyl group having 1 to 20 carbon atoms or an alkenyl group having 2 to 20 carbon atoms, and a polyvalent carboxylic acid having 3 or more valences. Anhydrides and alkyl (C1-C3) esters are also included. Of these, dicarboxylic acids are preferred.
As the dicarboxylic acid, terephthalic acid is preferable, and as a specific example of succinic acid substituted with an alkyl group having 1 to 20 carbon atoms or an alkenyl group having 2 to 20 carbon atoms, dodecenyl succinic acid is preferable, and trivalent or higher polyvalent As the carboxylic acid, trimellitic acid is preferable.
These acid components can be used alone or in combination of two or more.

Examples of the alcohol component include aromatic diols such as polyoxypropylene-2,2-bis (4-hydroxyphenyl) propane and polyoxyethylene-2,2-bis (4-hydroxyphenyl) propane. An alkylene (2 to 3 carbon atoms) oxide adduct (average number of added moles 1 to 16) is preferred. Moreover, these alcohol components can be used individually or in combination of 2 or more types.
The glass transition point, softening point, number average molecular weight and acid value of the amorphous polyester (c) are preferably the same as the preferred range of the amorphous polyester (b).

  The amorphous polyester (c) may be used alone or in combination of two or more, and contains two types of polyesters having different softening points from the viewpoint of low-temperature fixability, offset resistance and durability of the toner. It is preferable to do. When two types of polyesters having different softening points are polyesters (c-1) and (c-2), respectively, the softening point of one polyester (c-1) is preferably 70 ° C. or higher and lower than 115 ° C., and the other polyester The softening point of (c-2) is preferably 115 ° C. or higher and 165 ° C. or lower. The weight ratio of polyester (c-1) to polyester (c-2) ((c-1) / (c-2)) is preferably 10/90 to 90/10, more preferably 50/50 to 90. / 10.

(Production of colorant-containing resin particles (A))
The colorant-containing resin particles (A) can be produced by a method in which a resin containing the crystalline polyester (a) and the above-mentioned optional components are dispersed in an aqueous medium to obtain a dispersion containing the resin particles (A). preferable.
Examples of a method for obtaining a dispersion include a method in which a resin or the like is added to an aqueous medium and a dispersion treatment is performed using a disperser or the like, and a method in which an aqueous medium is gradually added to a resin or the like to perform phase inversion emulsification. From the viewpoint of low-temperature fixability of the toner, a method using phase inversion emulsification is preferred. Hereinafter, a method by phase inversion emulsification will be described.

First, a resin containing crystalline polyester (a), an alkaline aqueous solution, and the above-mentioned optional components are melted and mixed to obtain a resin mixture.
When the resin containing the crystalline polyester (a) is composed of a plurality of resins, a mixture of the crystalline polyester (a) and other resins may be used in advance, but the alkaline aqueous solution and the optional components may be used. It may be obtained by adding at the same time when adding, melting and mixing. For example, when the resin containing the crystalline polyester (a) contains the amorphous polyester (c), from the viewpoint of low-temperature fixability of the toner, the crystalline polyester (a), the amorphous polyester (c), the alkali A method of obtaining a resin mixture by melting and mixing the aqueous solution and the above-mentioned optional components is preferable.
In mixing, it is preferable to add a surfactant from the viewpoint of the emulsion stability of the resin.

  Examples of the alkali in the alkaline aqueous solution include hydroxides of alkali metals such as potassium hydroxide and sodium hydroxide, and ammonia. From the viewpoint of improving the dispersibility of the resin, potassium hydroxide and sodium hydroxide are preferable. . The concentration of alkali in the aqueous alkali solution is preferably 1 to 30% by weight, more preferably 1 to 25% by weight, and still more preferably 1.5 to 20% by weight.

Examples of surfactants include nonionic surfactants, anionic surfactants, and cationic surfactants. Among these, nonionic surfactants are preferred, and nonionic surfactants and anionic surfactants are preferred. It is more preferable to use a surfactant or a cationic surfactant in combination, and it is more preferable to use a nonionic surfactant and an anionic surfactant in combination from the viewpoint of sufficiently emulsifying the resin.
When a nonionic surfactant and an anionic surfactant are used in combination, the weight ratio of the nonionic surfactant to the anionic surfactant (nonionic surfactant / anionic surfactant) is: From the viewpoint of sufficiently emulsifying the resin, it is preferably 0.3 to 10, more preferably 0.5 to 5.

Nonionic surfactants include polyoxyethylene nonyl phenyl ether, polyoxyethylene oleyl ether, polyoxyethylene alkyl aryl ethers such as polyoxyethylene lauryl ether, polyoxyethylene alkyl ethers, polyethylene glycol monolaurate , Polyoxyethylene fatty acid esters such as polyethylene glycol monostearate and polyethylene glycol monooleate, and oxyethylene / oxypropylene block copolymers. Among these, from the viewpoint of emulsion stability of the resin, polyoxyethylene Alkyl ethers are preferred.
Examples of the anionic surfactant include dodecyl benzene sulfonic acid, sodium dodecyl benzene sulfonate, sodium dodecyl sulfate, sodium alkyl ether sulfate, and dipotassium alkenyl succinate. Among these, from the viewpoint of emulsion stability of the resin, dodecyl Sodium benzenesulfonate and sodium alkyl ether sulfate are preferred.
Examples of the cationic surfactant include alkylbenzene dimethyl ammonium chloride, alkyl trimethyl ammonium chloride, distearyl ammonium chloride and the like.

  The content of the surfactant is preferably 20 parts by weight or less, more preferably 15 parts by weight or less, still more preferably 0.1 to 10 parts by weight with respect to 100 parts by weight of the resin constituting the resin particles (A). More preferably, it is 0.5 to 10 parts by weight.

As a method for obtaining a resin mixture, a resin containing crystalline polyester (a), an aqueous alkali solution, and the above optional components, preferably a surfactant, are placed in a container, and the resin is melted uniformly while stirring with a stirrer. It is preferable to mix them.
The temperature at which the resin is melted and mixed is preferably equal to or higher than the glass transition point of the amorphous polyester (c) when the resin containing the crystalline polyester (a) contains the amorphous polyester (c). From the viewpoint of obtaining homogeneous resin particles, the melting point of the crystalline polyester (a) is more preferable.

Next, an aqueous medium is added to the resin mixture and phase inversion is performed to obtain a dispersion containing resin particles (A).
The aqueous medium preferably contains water as a main component, and from the viewpoint of obtaining stable resin particles, the water content in the aqueous medium is preferably 80% by weight or more, more preferably 90% by weight or more, and still more preferably. Is 95% by weight or more, more preferably substantially 100% by weight. The water used is preferably deionized water or distilled water.
As components other than water, organic solvents that dissolve in water such as alkyl alcohols having 1 to 5 carbon atoms; dialkyl (carbon numbers 1 to 3) ketones such as acetone and methyl ethyl ketone; and cyclic ethers such as tetrahydrofuran are used. Among these, from the viewpoint of preventing mixing into the toner, an alkyl alcohol having 1 to 5 carbon atoms that does not dissolve the polyester is preferable, and methanol, ethanol, isopropanol, and butanol are more preferable.

When the resin containing the crystalline polyester (a) contains the amorphous polyester (c), the temperature at which the aqueous medium is added is preferably equal to or higher than the glass transition point of the amorphous polyester (c), and is homogeneous. From the viewpoint of obtaining resin particles, the melting point of the crystalline polyester (a) is more preferable.
The addition rate of the aqueous medium is preferably 0.1 to 50 weights with respect to 100 parts by weight of the resin constituting the resin particles (A) until the phase inversion is completed from the viewpoint of making the resin particles have a small particle size. Part / minute, more preferably 0.1 to 30 parts by weight / minute, still more preferably 0.5 to 10 parts by weight / minute, still more preferably 0.5 to 5 parts by weight / minute. In addition, there is no restriction | limiting in the addition rate of the aqueous medium after completion | finish of phase inversion.

The amount of the aqueous medium used is preferably 100 to 2000 parts by weight, more preferably 150 to 100 parts by weight with respect to 100 parts by weight of the resin constituting the resin particles (A) from the viewpoint of obtaining uniform aggregated particles in the subsequent aggregation step. 1500 parts by weight, more preferably 150 to 500 parts by weight.
The solid content concentration is preferably 7 to 50% by weight, more preferably 10 to 40% by weight, still more preferably 20 to 40% by weight, from the viewpoint of the stability and ease of handling of the obtained resin particle dispersion. More preferably, it is 25 to 35% by weight. In addition, solid content is the total amount of non-volatile components, such as resin and surfactant.

The volume median particle size of the resin particles (A) in the dispersion containing the obtained resin particles (A) is preferably from 0.02 to 2 μm, more preferably from the viewpoint of obtaining a high-image toner. It is 02-1.5 micrometers, More preferably, it is 0.05-1 micrometer, More preferably, it is 0.05-0.5 micrometer. Here, the volume-median particle size is a particle size at which the cumulative volume frequency calculated by the volume fraction is 50% calculated from the smaller particle size.
The coefficient of variation (CV value) (%) of the particle size distribution of the resin particles is preferably 40% or less, more preferably 35% or less, still more preferably 30% or less, and still more preferably, from the viewpoint of obtaining a high-image toner. Is 28% or less. The CV value is a value represented by the following formula, and is specifically obtained by the method described in the examples.
CV value (%) = [standard deviation of particle size distribution (μm) / volume median particle size (μm)] × 100

[Releasing agent particles]
The release agent particles are preferably obtained by dispersing the release agent in an aqueous medium.
The release agent particles preferably contain a surfactant from the viewpoint of aggregation. The content of the surfactant is preferably 0.01 to 10 parts by weight, more preferably 0.1 to 5 parts by weight with respect to 100 parts by weight of the release agent, from the viewpoints of aggregability and chargeability of the obtained toner. Parts by weight.
The volume median particle size of the release agent particles is preferably 0.1 to 1 μm, more preferably 0.1 to 0.7 μm, and still more preferably 0.1 to 0.1 μm, from the viewpoint of preventing toner chargeability and hot offset. 0.5 μm.
The CV value of the release agent particles is preferably 15 to 50%, more preferably 15 to 40%, and further preferably 15 to 35%, from the viewpoint of the chargeability of the toner.

(Release agent)
As release agents, low molecular weight polyolefins such as polyethylene, polypropylene and polybutene; silicones having a softening point upon heating; fatty acid amides such as oleic acid amide and stearic acid amide; carnauba wax, rice wax and candelilla wax Plant waxes such as beeswax; animal waxes such as beeswax; mineral / petroleum waxes such as montan wax, paraffin wax, and Fischer-Tropsch wax. These release agents can be used alone or in combination of two or more. Among these, carnauba wax is preferable from the viewpoint of improving the durability and storage stability of the toner. Carnauba wax has an appropriate affinity with resin particles, so it is unlikely to come out on the toner surface even during fusing, and it is considered that the durability and storage stability of the toner are improved.
The melting point of the release agent is preferably from 65 to 100 ° C., more preferably from 75 to 95 ° C., further preferably from 75 to 90 ° C., more preferably from the viewpoint of low-temperature fixability, storage stability, and durability of the toner. 80-90 ° C.
In the present invention, the melting point of the release agent is determined by the method described in the examples. When two or more release agents are used in combination, the melting point of the release agent having the largest weight ratio among the release agents contained in the obtained toner is the melting point of the release agent in the present invention, and all have the same ratio. In this case, the lowest melting point is the melting point of the release agent.
The amount of the release agent used is preferably 1 to 20 parts by weight, more preferably 2 to 15 parts by weight, based on 100 parts by weight of the resin in the toner, from the viewpoint of toner releasability and chargeability.

(Manufacture of release agent particles)
The release agent particles are preferably obtained as a dispersion of release agent particles by dispersing the release agent in an aqueous medium. Furthermore, it is preferable that the dispersion of the release agent particles is obtained by dispersing the release agent and the aqueous medium using a disperser in the presence of a surfactant at a temperature equal to or higher than the melting point of the release agent. . As the disperser to be used, a homogenizer, an ultrasonic disperser or the like is preferable.
The aqueous medium and surfactant used in the production are preferably those used when obtaining the resin particles (A), and the aqueous medium is preferably one containing water as a main component. The content of water in the aqueous medium is preferably 90% by weight or more, more preferably 95% by weight or more, and still more preferably substantially 100% by weight from the viewpoint of obtaining stable release agent particles. The water used is preferably deionized water or distilled water. Further, as the surfactant, an anionic surfactant is preferable, and dipotassium alkenyl succinate is more preferable.

[Flocculant]
The flocculant used in the present invention comprises an electrolyte. An agglomerated particle dispersion can be efficiently obtained by mixing an aggregating agent made of an electrolyte with colored particles and releasing agent particles in an aqueous medium.
Examples of the electrolyte constituting the flocculant used in the present invention include cationic surfactants such as quaternary ammonium salts, inorganic salts such as inorganic metal salts and inorganic ammonium salts, and inorganic flocculants such as metal complexes. It is done. The cation valence of the electrolyte may be 1 or more, preferably 1 and / or 2, more preferably 1.
Examples of the inorganic salt include inorganic salts having a cation valence of 2 or more, and inorganic salts having a cation valence of 1, easy adjustment of cohesion, and storage stability and durability of the resulting toner. From the viewpoint of improving the above, an inorganic salt having a cation valence of 1 is preferred.
Examples of the inorganic salt having a cation valence of 2 or more include calcium salts such as calcium chloride and calcium nitrate; aluminum salts such as aluminum chloride, polyaluminum chloride and polyaluminum hydroxide.
Examples of the inorganic salt having a cation valence of 1 include inorganic sodium salts such as sodium sulfate and sodium chloride; inorganic ammonium salts such as ammonium sulfate, ammonium chloride and ammonium nitrate. From the above viewpoint, inorganic ammonium salts are preferred, and ammonium sulfate. Is more preferable.

[Resin Particles (B) Containing Amorphous Polyester (b)]
In the present invention, the resin particles (B) containing amorphous polyester (hereinafter also simply referred to as “resin particles (B)”) are prepared from amorphous polyester (b) from the viewpoint of storage stability and durability of the toner. ).
The glass transition point of the resin particle (B) is appropriately determined depending on the glass transition point of the resin such as the amorphous polyester (b) constituting the resin particle (B), the kind and amount of the additive, etc. From the viewpoint of durability, low-temperature fixability and storage stability, it is preferably 55 ° C. or higher, more preferably 55 to 75 ° C., still more preferably 55 to 70 ° C., still more preferably 55 to 65 ° C.

The content of the amorphous polyester (b) in the resin particles (B) is preferably 70% by weight or more, more preferably 80% by weight or more, and still more preferably 90%, from the viewpoint of storage stability and durability of the toner. -100% by weight, more preferably 95-100% by weight, still more preferably 100% by weight.
In addition to the amorphous polyester (b), the resin particles (B) are known resins usually used for toners, such as the above-mentioned crystalline polyester (a), styrene acrylic copolymer, epoxy resin, polycarbonate, polyurethane. A resin such as
The resin particles (B) are obtained by the same method as the method for producing the resin particles (A) described above, and the same alkaline aqueous solution, surfactant and aqueous medium can be suitably used.

(Amorphous polyester (b))
In the present invention, the amorphous polyester (b) is a polyester having a crystallinity index of more than 1.4 or less than 0.6.
From the viewpoint of storage stability and durability of the toner, the crystallinity index of the amorphous polyester (b) is preferably less than 0.6 or more than 1.4 and less than 4, more preferably less than 0.6 or 1. 5 or more and 4 or less, more preferably less than 0.6 or 1.5 or more and 3 or less, and further preferably less than 0.6 or 1.5 or more and 2 or less. The crystallinity index can be appropriately determined depending on the type and ratio of raw material monomers, production conditions (eg, reaction temperature, reaction time, cooling rate), and the like.
As the amorphous polyester (b), an amorphous polyester (b) having an acid group at the molecular end is preferable. Examples of the acid group include a carboxyl group, a sulfonic acid group, a phosphonic acid group, and a sulfinic acid. Among these, a carboxyl group is preferable from the viewpoint of promoting emulsification of the polyester.

The amorphous polyester (b) can be produced by a polycondensation reaction between an acid component and an alcohol component in the same manner as the crystalline polyester (a).
Examples of the acid component include a dicarboxylic acid, a succinic acid substituted with an alkyl group having 1 to 20 carbon atoms or an alkenyl group having 2 to 20 carbon atoms, and a polyvalent carboxylic acid having 3 or more valences. Anhydrides and alkyl (C1-C3) esters are also included. Of these, dicarboxylic acids are preferred.
Dicarboxylic acids include dicarboxylic acids containing aromatic rings such as phthalic acid, isophthalic acid and terephthalic acid, and aliphatics such as sebacic acid, fumaric acid, maleic acid, adipic acid, azelaic acid, succinic acid, and cyclohexanedicarboxylic acid. Among these, terephthalic acid is preferable.
Examples of the succinic acid substituted with an alkyl group having 1 to 20 carbon atoms or an alkenyl group having 2 to 20 carbon atoms include dodecyl succinic acid, dodecenyl succinic acid, and octenyl succinic acid.
Examples of the trivalent or higher polyvalent carboxylic acid include trimellitic acid, 2,5,7-naphthalenetricarboxylic acid, pyromellitic acid and the like. Among these, trimellitic acid is preferable from the viewpoint of offset resistance.
These acid components can be used alone or in combination of two or more.
The amorphous polyester (b) is an amorphous polyester (b) obtained by using an acid component containing a trivalent or higher polyvalent carboxylic acid, preferably trimellitic acid, from the viewpoint of offset resistance of the toner. It is preferable to use at least one kind.

As an alcohol component, the thing similar to the said alcohol component used for crystalline polyester (a) is mentioned. Among these, from the viewpoint of obtaining amorphous polyester, aromatic diols are preferable, and polyoxypropylene-2,2-bis (4-hydroxyphenyl) propane, polyoxyethylene-2,2-bis (4-hydroxy). More preferred are alkylene (carbon number 2-3) oxide adducts (average number of added moles 1-16) of bisphenol A such as phenyl) propane.
These alcohol components can be used alone or in combination of two or more.

The glass transition point of the amorphous polyester (b) is preferably 55 to 75 ° C., more preferably 55 to 70 ° C., and still more preferably 58 to 68, from the viewpoint of toner durability, low-temperature fixability and storage stability. ° C.
From the same viewpoint, the softening point of the amorphous polyester (b) is preferably 70 to 165 ° C, more preferably 70 to 140 ° C, still more preferably 90 to 140 ° C, still more preferably 100 to 130 ° C.
In addition, when using 2 or more types of amorphous polyesters (b) in mixture, the glass transition point and softening point are the methods described in the examples as a mixture of 2 or more types of amorphous polyesters (b). The glass transition point and softening point obtained by the above.

The number average molecular weight of the amorphous polyester (b) is preferably 1,000 to 50,000, more preferably 1,000 to 10,000, from the viewpoint of toner durability, low-temperature fixability and storage stability. More preferably, it is 2,000-8,000.
The acid value of the amorphous polyester (b) is preferably 6 to 35 mg KOH / g, more preferably 10 to 35 mg KOH / g, and still more preferably 15 to 35 mg KOH / g, from the viewpoint of emulsification in the aqueous medium of the resin. is there.

  The amorphous polyester (b) preferably contains two kinds of polyesters having different softening points from the viewpoints of low-temperature fixability, offset resistance and durability of the toner. When two types of polyesters having different softening points are respectively used as polyesters (b-1) and (b-2), the softening point of one polyester (b-1) is preferably 70 ° C. or higher and lower than 115 ° C., and the other The softening point of the polyester (b-2) is preferably 115 ° C or higher and 165 ° C or lower. The weight ratio of polyester (b-1) to polyester (b-2) ((b-1) / (b-2)) is preferably 10/90 to 90/10, more preferably 50/50 to 90. / 10.

  In addition, in this invention, what modified | denatured each of crystalline polyester (a), amorphous polyester (b), and (c) can be used in the range which does not impair the effect. Examples of methods for modifying the polyester include grafting with phenol, urethane, epoxy, etc. by the methods described in JP-A-11-133668, JP-A-10-239903, JP-A-8-20636, and the like. Examples thereof include a method of forming a block and a method of forming a composite resin having two or more resin units including a polyester unit.

[Salt having a cation having a higher valence than the flocculant]
In the present invention, examples of the salt having a cation having a valence higher than that of the flocculant include inorganic metal salts having a cation valence of 2 or more, halogenated salts of polyamines, metal complexes having a cation valence of 2 or more, and the like. Among these, inorganic metal salts are preferable, and inorganic metal salts having a cation valence of 2 are more preferable.
When an electrolyte having a cation valence of 1 is used for the aggregating agent, the cation valence of the salt is preferably 2 or 3, and preferably 2 from the viewpoint of strengthening the aggregation state of the aggregated particles. More preferred.
Examples of the inorganic metal salt having a cation valence of 2 include calcium salts such as calcium chloride and calcium nitrate; magnesium salts such as magnesium chloride and magnesium sulfate. Among these, magnesium salts are preferred, and magnesium chloride and magnesium sulfate. Is more preferable, and magnesium sulfate is more preferable.
The inorganic metal salt having a cation valence of 3 is preferably an aluminum salt such as aluminum chloride, polyaluminum chloride, polyaluminum hydroxide, and more preferably aluminum chloride.

Next, each step in the method for producing an electrophotographic toner of the present invention will be described.
[Step (1)]
Step (1) is a step of obtaining an aggregated particle dispersion by mixing colored particles, release agent particles, and an aggregating agent composed of an electrolyte in an aqueous medium. There is no restriction on the order of mixing, and either of them may be added in order or simultaneously, but from the viewpoint of efficiently obtaining an aggregated particle dispersion, the colored particles and the release agent particles are mixed. After that, it is preferable to mix a flocculant. Hereinafter, a method of mixing in this order will be described.

In this step, first, colored particles and release agent particles are mixed in an aqueous medium to obtain a mixed dispersion.
In the step (1), the colorant-containing resin particles (A) may be mixed as the colored particles, or resin particles other than the resin particles (A) may be mixed. The resin particles other than the resin particles (A) are preferably resin particles containing amorphous polyester from the viewpoint of improving the storage stability of the toner, and the resin particles having the same components as the resin particles (B) described above. More preferably, the same composition ratio is more preferable.
There is no restriction | limiting in order of mixing, You may add any in order and may add simultaneously.

When the colored particles are colorant-containing resin particles (A), the content of the resin particles (A) is preferably 10 to 40 parts by weight, more preferably 12 to 35 parts by weight in the aggregated particle dispersion, More preferably, it is 12-20 weight part. The content of the aqueous medium is preferably 60 to 90 parts by weight, more preferably 70 to 88 parts by weight in the aggregated particle dispersion.
The content of the colorant is preferably 1 to 20 parts by weight, more preferably 3 to 15 parts by weight with respect to 100 parts by weight of the resin constituting the resin particles (A) from the viewpoint of image density.
The content of the release agent particles is preferably 1 to 20 parts by weight, more preferably 2 to 15 parts by weight, based on the total 100 parts by weight of the resin and the colorant, from the viewpoint of toner releasability and chargeability. Part.
The temperature of the mixed dispersion at the time of mixing is preferably 0 to 40 ° C. from the viewpoint of aggregation control.

Next, an aggregating agent made of an electrolyte is mixed with the mixed dispersion in an aqueous medium, and the particles in the mixed dispersion are aggregated to obtain a dispersion of aggregated particles.
From the viewpoint of storage stability and durability of the toner, the use amount of the flocculant is, based on 100 parts by weight of the resin constituting the resin particles (A), when the colored particles are the colorant-containing resin particles (A). Preferably it is 50 parts by weight or less, more preferably 40 parts by weight or less, still more preferably 30 parts by weight or less, and preferably 1 part by weight or more, more preferably 3 parts by weight or more from the viewpoint of cohesiveness of the resin particles. More preferably, it is 5 parts by weight or more. Considering the above points, the amount of the flocculant used is preferably 1 to 50 parts by weight, more preferably 3 to 40 parts by weight, and still more preferably 100 parts by weight of the resin constituting the resin particles (A). Is 5 to 30 parts by weight.

  As an aggregating method, it is preferable to add the aggregating agent as an aqueous solution dropwise to a container containing the mixed dispersion. The flocculant may be added at one time, or may be added intermittently or continuously. However, it is preferable to perform sufficient stirring at the time of addition and after completion of the addition. From the viewpoint of controlling aggregation and shortening the toner production time, the dropping time of the aggregating agent is preferably 1 to 120 minutes. The dropping temperature is preferably 0 to 40 ° C. from the viewpoint of controlling aggregation.

  The volume-median particle size of the obtained aggregated particles is preferably 1 to 10 μm, more preferably 2 to 9 μm, and further preferably 3 to 6 μm, from the viewpoint of reducing the reduction in toner particle size. The CV value is preferably 30% or less, more preferably 28% or less, and still more preferably 25% or less.

The concentration of the aggregating agent in the aggregated particle dispersion obtained in the step (1) is preferably 0.08 from the viewpoint of improving the storage stability of the toner when an electrolyte having a cation valence of 1 is used as the aggregating agent. It is -1.3 mol / L, More preferably, it is 0.1-1.1 mol / L, More preferably, it is 0.3-1.0 mol / L.
The preferred flocculant concentration depends on the valency of the flocculant used. When an electrolyte having a cation valence of 2 or more is used for the aggregating agent, the aggregating agent concentration is z from the viewpoint of obtaining an appropriate aggregating property for obtaining agglomerated particles having the above-mentioned particle diameter. , Preferably 0.08 × z ^{−6 to} 1.3 × z ⁻⁶ mol / L, more preferably 0.1 × z ^{−6 to} 1.1 × z ⁻⁶ mol / L, still more preferably 0.3. × a z ^-6 to 1.0 × z ^-6 mol / L.
As shown in the following formula, the coagulant equivalent is obtained by dividing the product of the cation valence of the coagulant and the number of moles of the coagulant by the number of moles of acid groups (carboxy groups) of the total resin contained in the toner. Is required. The number of moles of acid groups (carboxy groups) in all resins is calculated from the acid value and content of all resins.
Flocculant equivalent = (valence of cation of flocculant) × (mol number of flocculant) / (mol number of acid groups (carboxy groups) of all resins)
From the viewpoint of improving the storage stability of the toner, the equivalent of the aggregating agent in the aggregated particle dispersion is preferably 5 to 15 equivalents, more preferably 7 to 12 equivalents, and even more preferably 8 to 11 equivalents.

[Step (2)]
In the step (2), the resin particles (B) containing the amorphous polyester (b) are added to the aggregated particle dispersion obtained in the step (1) to obtain the core-shell particle dispersion (1). It is.
In this step, first, after preparing a dispersion of resin particles (B) containing amorphous polyester (b) (hereinafter also referred to as “resin particle (B) dispersion”), the resin particles (B It is preferable that the dispersion liquid is added to the dispersion liquid of the aggregated particles obtained in the step (1) to adhere the resin particles (B) to the aggregated particles, thereby obtaining core-shell structured particles.
From the viewpoint of more uniformly attaching the resin particles (B) to the aggregated particles, it is preferable to add an aqueous medium to the aggregated particle dispersion and dilute it before adding the resin particle (B) dispersion.
When the resin particle (B) dispersion is added, the aggregating agent may be used to efficiently attach the resin particles (B) to the aggregated particles.
As an addition method when adding the resin particle (B) dispersion, the coagulant and the resin particle (B) dispersion are added simultaneously, and the coagulant and the resin particle (B) dispersion are added alternately. A method, a method of adding the resin particle (B) dispersion while gradually raising the temperature of the core aggregated particle dispersion, and the like are preferable. According to such a method, it is possible to prevent a decrease in the cohesiveness of the aggregated particles and the resin particles (B) due to a decrease in the concentration of the coagulant. Among these, from the viewpoint of toner productivity and production simplicity, it is preferable to add the resin particle (B) dispersion while gradually raising the temperature of the aggregated particle dispersion.

In step (2), the temperature in the system at the time of addition and / or after completion of the addition of the resin particle (B) dispersion is less than the melting point of the release agent and from the glass transition point of the amorphous polyester (b). It is preferable that the temperature be 20 ° C. or lower.
By setting the temperature at the time of adding the resin particles (B) to be lower than the melting point of the release agent, the durability and storage stability of the obtained toner can be improved. The reason for this is not clear, but it is also considered that since the core-shell particles are not fused together, the generation of coarse particles is suppressed and the crystallinity of the release agent can be maintained.

  The addition amount of the resin particles (B) is a weight ratio of the resin particles (B) to the resin particles (A) (resin particles (B) / The amount of the resin particles (A)) is preferably 0.3 to 1.5, more preferably 0.3 to 1.0, and still more preferably 0.35 to 0.75.

The resin particle (B) dispersion may be added continuously over a certain period of time, or may be added at once, or may be added in multiple portions. From the viewpoint of facilitating selective aggregation on the aggregated particles, it is preferably added continuously over a certain period of time or divided into a plurality of times, and among them, the viewpoint of promoting selective aggregation Further, from the viewpoint of production efficiency, it is more preferable to add continuously over a certain time, and when continuously adding, it is further possible to raise the temperature in the system within the above temperature range. preferable.
The addition time in the case of continuous addition is preferably 1 to 10 hours, more preferably 3 to 8 hours, from the viewpoint of obtaining uniform core-shell structure particles and shortening of the production time.

The total amount of the resin particles (B) is added, and aggregation is stopped when the toner particles have grown to an appropriate particle size.
As the particle size for stopping the aggregation, the volume median particle size is preferably 1 to 10 μm, more preferably 2 to 8 μm, still more preferably 3 to 7 μm, and further preferably 4 to 6 μm.
Methods for stopping the aggregation include a method of cooling the dispersion and a method of adding an aggregation terminator. From the viewpoint of reliably preventing unnecessary aggregation, the aggregation is stopped by adding an aggregation terminator. The method of making it preferable is.
As the aggregation terminator, a surfactant is preferable, and an anionic surfactant is more preferable. Examples of the anionic surfactant include alkyl ether sulfates such as sodium alkyl ether sulfate, alkyl sulfates, and linear alkylbenzene sulfonates. The aggregation terminators can be used alone or in combination of two or more.
That is, in this step (2), after adding the resin particles (B) to the aggregated particle dispersion, an anionic surfactant as an aggregation terminator is added to obtain the core-shell particle dispersion (1). It is preferable to obtain.
The addition amount of the aggregation terminator is preferably 0.1 to 15 parts by weight with respect to 100 parts by weight of the total resin in the system, from the viewpoint of reducing the aggregation terminator and the residual of the aggregation terminator in the toner. Preferably it is 0.1-10 weight part, More preferably, it is 0.1-8 weight part. The aggregation terminator may be added in any form, but is preferably added in an aqueous solution from the viewpoint of productivity.

The concentration of the flocculant in the core-shell particle dispersion (1) obtained in the step (2) is preferably from the viewpoint of improving the storage stability of the toner when an electrolyte having a cation valence of 1 is used as the flocculant. It is 0.05-0.85 mol / L, More preferably, it is 0.10-0.75 mol / L, More preferably, it is 0.20-0.70 mol / L.
The suitable flocculant concentration varies depending on the valence of the flocculant used, but when an electrolyte having a cation valence of 2 or more is used as the flocculant, the flocculant concentration is appropriate for obtaining core-shell particles having the above-mentioned particle diameter. From the viewpoint of obtaining cohesiveness, when the valence of the coagulant is z, it is preferably 0.05 × z ^{−6 to} 0.85 × z ⁻⁶ mol / L, more preferably 0.10 × z ^{−6 to} 0 .75 × z ⁻⁶ mol / L, more preferably 0.20 × z ^{−6 to} 0.70 × z ⁻⁶ mol / L.
The flocculant equivalent in the core-shell particle dispersion (1) obtained from the above formula is preferably 3.3 to 10 equivalents, more preferably 4.7 to 8 from the viewpoint of improving the storage stability of the toner. Equivalent, more preferably 5.3 to 7.3 equivalent.

[Step (3)]
Step (3) is a step of obtaining a core-shell particle dispersion (2) by adding a salt having a cation having a higher valence than the flocculant to the core-shell particle dispersion (1) obtained in step (2). It is.
The addition of the salt is preferably performed in a state where aggregation in the step (2) is stopped from the viewpoint of preventing excessive aggregation of the core-shell particles, that is, aggregation between the core-shell particles. Specifically, it is preferable to add the salt after adding the above-mentioned aggregation terminator in step (2) or after cooling the dispersion (1) to stop aggregation, The temperature is preferably 30 ° C. or lower, more preferably 28 ° C. or lower.
As a method for adding the salt, it may be added at one time, or may be added intermittently or continuously. However, from the viewpoint of preventing excessive aggregation, it is preferable to add the salt continuously. When adding as an aqueous solution containing, it is preferable to add continuously by dripping.
It is preferable to perform sufficient stirring during and after the addition.
From the viewpoint of preventing excessive aggregation, the salt is preferably added as an aqueous solution previously dissolved in deionized water or the like, and the concentration of the salt in the aqueous solution is preferably 2 to 15% by weight.
The concentration of the salt in the aqueous solution containing the salt is 0.01 mol / L to 0.1 mol / L from the viewpoint of improving the storage stability of the toner when a salt having a cation valence of 2 is used. When a salt having a cation valence of 3 or more is used, the concentration is preferably obtained by dividing the concentration value by the valence and multiplying by two.
The equivalent of the salt relative to the resin in the core-shell particle dispersion (2) is determined by the same method as the above-mentioned flocculant equivalent, and is preferably 0.1 to 1 equivalent from the viewpoint of improving the storage stability of the toner.

[Step (4)]
In step (4), the core-shell particle dispersion (2) is maintained at a temperature not higher than the melting point of the release agent and not less than 5 ° C. lower than the glass transition point of the amorphous polyester (b). In this step, the liquid (3a) is obtained.

In this step, the core-shell particle dispersion (2) obtained in the previous step is held at the above temperature (hereinafter also referred to as holding temperature). By maintaining the holding temperature below the melting point of the release agent, preferably below 5 ° C. below the melting point of the release agent, more preferably below 10 ° C. below the melting point of the release agent, toner durability and storage Stability can be improved.
Further, the holding temperature is at least 5 ° C lower than the glass transition point of the amorphous polyester (b), preferably at least 3 ° C lower than the glass transition point, more preferably at least 2 ° C lower than the glass transition point. As a result, the fusing property, the storage stability of the toner, the charging property and the toner productivity can be improved.
By satisfying these conditions, exposure of the release agent to the toner surface that causes a decrease in toner durability and storage stability while maintaining the crystalline state of the release agent that exhibits high fixability at low temperatures Can be suppressed, and the shell portion can be uniformly fused. As a result, it is considered that a toner satisfying all of excellent low-temperature fixability, durability and storage stability can be obtained.
Further, the holding temperature is preferably higher than the glass transition point of the resin particles (B), more preferably 2 ° C. higher than the glass transition point of the resin particles (B). Storage stability, chargeability and toner productivity can be further improved.
In view of the above points, the holding temperature in the step (4) is preferably 58 to 69 ° C, more preferably 59 to 67 ° C, and further preferably 60 to 65 ° C.
In the step (4), the holding time at the above temperature is preferably 1 to 24 hours, more preferably 1 to 12 hours, from the viewpoints of particle fusing property, toner storage stability, durability and toner productivity. More preferably, it is 2 to 6 hours.

The concentration of the flocculant in the core-shell particle dispersion (3a) obtained in the step (4) is preferably from the viewpoint of improving the storage stability of the toner when an electrolyte having a cation valence of 1 is used as the flocculant. It is 05-0.40 mol / L, More preferably, it is 0.10-0.30 mol / L, More preferably, it is 0.10-0.20 mol / L. The flocculant concentration here refers to the molar concentration of the flocculant added in the step (1) contained in the core-shell particle dispersion (3a).
When an electrolyte having a cation valence of 2 or more is used as the flocculant, the flocculant concentration is preferably 0.05 × z ^{−6 to} 0.40 × z ^{−6, where} z is the valency of the flocculant. Mol / L, more preferably 0.10 × z ^{−6 to} 0.30 × z ⁻⁶ mol / L, and still more preferably 0.10 × z ^{−6 to} 0.20 × z ⁻⁶ mol / L.
Further, the concentration of the flocculant in the core-shell particle dispersion (3a) after addition of the aqueous solution in this step is the concentration of the flocculant in the core-shell particle dispersion (1) from the viewpoint of improving the storage stability of the toner. It is preferable to be 0.65 times or less.

  In this step, it is preferable to confirm the progress of fusion by monitoring the circularity of the generated core-shell particles. Circularity is monitored by the method described in the examples. When the circularity reaches 0.920 or more, the cooling is performed and the fusion is stopped. The circularity of the core-shell particles contained in the finally obtained core-shell particle dispersion (3a) is preferably 0.920 to 0.970, more preferably 0.930, from the viewpoint of reducing toner scattering. ˜0.965, more preferably 0.940 to 0.960.

BET specific surface area by nitrogen adsorption method of the core-shell particles contained in the core-shell particle dispersion (3a), from the viewpoint of improving the storage stability of the toner, preferably 1.0 m ² / g or more 4.0m below ² / g More preferably, it is 1.0-3.0 m < ² > / g, More preferably, it is 1.0-2.7 m < ² > / g, More preferably, it is 1.0-2.5 m < ² > / g.
The volume-median particle size of the core-shell particles in the core-shell particle dispersion (3a) is preferably 1 to 10 μm, more preferably 2 to 10 μm, still more preferably 3 to 9 μm, from the viewpoint of improving the image quality of the toner. More preferably, it is 4-6 micrometers.
Furthermore, the ratio of the core-shell particles having a particle size of 2 μm or less is preferably 8.0% or less, more preferably 5.0% or less, more preferably the total number of core-shell particles in the core-shell particle dispersion (3a). Preferably it is 3.5% or less.

[Step (5)]
The core-shell particle dispersion (3a) obtained in the step (4) is subjected to a post-treatment step described later, whereby a toner having both excellent durability and storage stability can be obtained. However, the step (4) Thereafter, the storage stability of the obtained toner can be further improved by performing this step (5).
In step (5), after step (4), at least a part of the flocculant and the aqueous medium is removed from the core-shell particle dispersion (3a) to obtain a slurry, and the slurry has a higher valence than the flocculant. A salt having a cation is added, and held at a temperature not higher than the melting point of the release agent and not less than 5 ° C. lower than the glass transition point of the amorphous polyester (b) to obtain a core-shell particle dispersion (3b). It is a process. Hereinafter, the core-shell particle dispersions (3a) and (3b) are collectively referred to as the core-shell particle dispersion (3).

In this step, first, at least a part of the flocculant and the aqueous medium is removed from the core-shell particle dispersion (3a) to obtain a slurry having a high solid content concentration (hereinafter also simply referred to as “slurry”). In this step, all of the flocculant and the aqueous medium may be removed, but from the viewpoint of controlling the particle size distribution during redispersion and preventing secondary aggregation of the particles, it is preferable to leave a part and obtain a slurry. .
As a method for removing at least a part of the flocculant and the aqueous medium, a method used for general solid-liquid separation such as a suction filtration method, a centrifugal dehydration method, and a pressure filtration method can be used. From the viewpoint of workability, suction filtration is preferred.
As long as the suction filtration method is a filter used for normal filtration, the filter is not limited, but from the viewpoint of maintaining the aggregation of particles and adjusting the solid content concentration of the slurry to a predetermined value, the suction bottle It is preferable to use a filter having a shape equipped with a Buchner funnel.
The solid content of the slurry is preferably 10 to 60% by weight, more preferably 20 to 50% by weight, based on the whole slurry, from the viewpoint of controlling the particle size distribution during redispersion and preventing secondary aggregation of the particles. More preferably, it is 30 to 40% by weight.

Next, a salt having a cation having a higher valence than the flocculant used in step (1) is added to the obtained slurry.
From the viewpoint of preventing unnecessary aggregation, the salt is preferably added as an aqueous solution, as in the step (3). Similarly, when adding as an aqueous solution containing a salt, it is preferable to add dropwise continuously.
Examples of the aqueous solution containing the salt to be added include the aqueous solutions described above.
A surfactant can be further added when the aqueous solution is added. Examples of the surfactant include those described above for the step (2). Among these, an anionic surfactant is preferable, and sodium alkyl ether sulfate is more preferable.
Moreover, in order to re-disperse the particles in the slurry after the addition of the aqueous medium, stirring is preferably performed. Examples of the stirring method include a method of rotating a stirring blade in a liquid using a stirrer and a method of using a disperser such as a homomixer. From the viewpoint of maintaining particle aggregation, a method using a stirrer is preferable. .

In this step, step (5) may be repeated once more after adding the salt. Specifically, an operation of removing at least a part of the flocculant and the aqueous medium from the core-shell particle dispersion (3a) obtained in the step (4) to obtain a slurry, and adding the aqueous medium to the slurry is 1 It is a method of performing more than once. By doing in this way, it becomes possible to reduce a coagulant | flocculant density | concentration efficiently and to promote the fusion | melting of each particle | grain performed next.
The flocculant concentration in the core-shell particle dispersion (3b) after addition of the aqueous solution in this step is preferably less than 0.50 mol / L, more preferably 0.05 mol from the viewpoint of improving the storage stability of the toner. / L, more preferably less than 0.03 mol / L. Here, the flocculant concentration refers to the molar concentration of the flocculant added in the step (1) included in the core-shell particle dispersion (3b).
When an electrolyte having a cation valence of 2 or more is used as the flocculant, the flocculant concentration is preferably less than 0.50 × z ⁻⁶ mol / L, more preferably, where z is the valency of the flocculant. It is less than 0.05 × z ⁻⁶ mol / L, more preferably less than 0.03 × z ⁻⁶ mol / L.
Further, the concentration of the flocculant in the core-shell particle dispersion after addition of the aqueous solution in this step is 0.1 from the concentration of the flocculant in the core-shell particle dispersion (1) from the viewpoint of improving the storage stability of the toner. It is preferable to be less than or equal to twice, more preferably less than or equal to 0.07 times, and even more preferably less than or equal to 0.05 times.

  Next, the obtained core-shell particle dispersion is maintained at a temperature not higher than the melting point of the release agent and not less than 5 ° C. lower than the glass transition point of the amorphous polyester (b), and the core-shell particle dispersion (3b) Get. However, the circularity of the particles contained in the core-shell particle dispersion (3b) is preferably 0.005 or more larger than the circularity of the particles contained in the core-shell particle dispersion (1).

In this step, the temperature of the core-shell particle dispersion after addition of the salt is maintained at the above temperature (holding temperature) from the viewpoint of improving the storage stability of the toner. The preferred range of the holding temperature is the same as the holding temperature used for obtaining the core-shell particle dispersion (3a) in the above-mentioned step (4).
The specific holding temperature in the step (5) is preferably 58 to 69 ° C, more preferably 59 to 67 ° C, still more preferably 60 to 64 ° C.
In the step (5), the holding time at the above temperature is preferably 0.1 to 24 hours, more preferably 0.5 from the viewpoints of particle fusion property, storage stability, chargeability and toner productivity. -12 hours, more preferably 1-6 hours.

  Also in the step (5), it is preferable to confirm the progress of fusion by monitoring the circularity of the generated core-shell particles. Circularity is monitored by the method described in the examples. When the circularity is 0.950 or higher and the circularity of the particles contained in the core-shell particle dispersion liquid (1) is 0.005 or higher, cooling is performed when the target circularity is reached, and the fusion is stopped. preferable. The circularity of the core-shell particles contained in the finally obtained core-shell particle dispersion (3) is preferably 0.950 to 0.980 from the viewpoint of improving the storage stability of the toner and reducing the scattering of the toner. More preferably, it is 0.950-0.975, More preferably, it is 0.955-0.970.

The BET specific surface area by the nitrogen adsorption method of the core-shell particles contained in the core-shell particle dispersion (3b) is preferably 1.0 m ² / g or more from the viewpoint of improving the storage stability of the toner and suppressing the scattering of the toner. 4.0m less than ² / g, more preferably 1.0~3.0m ² / g, more preferably 1.0~2.5m ² / g, further preferably 1.0~2.0m ² / g is there.
The volume-median particle size of the core-shell particles in the core-shell particle dispersion (3b) is preferably 2 to 10 μm, more preferably 2 to 8 μm, more preferably 2 to 7 μm, from the viewpoint of improving the image quality of the toner. More preferably, it is 3-8 micrometers, More preferably, it is 4-6 micrometers.
Furthermore, the ratio of the core-shell particles having a particle size of 2 μm or less is preferably 8.0% or less, more preferably 5.0% or less, more preferably the total number of core-shell particles in the core-shell particle dispersion (3b). Preferably it is 3.3% or less.

[Post-processing process]
In the present invention, a post-treatment step may be performed after step (4) or step (5), and it is preferable to obtain toner particles by isolating the core-shell particles.
Since the core-shell particles obtained in the step (4) or the step (5) are present in the aqueous medium, it is preferable to first perform solid-liquid separation. For solid-liquid separation, a suction filtration method or the like is preferably used.
In addition, it is preferable to wash after solid-liquid separation. As a cleaning method, for the purpose of ensuring sufficient charging characteristics and reliability as a toner, it is preferable to perform cleaning with an acid in order to remove metal ions on the toner surface. Moreover, since it is preferable to remove the added nonionic surfactant, it is preferable to wash with an aqueous solution below the cloud point of the nonionic surfactant. The washing is preferably performed a plurality of times.
Next, it is preferable to perform drying. As the drying method, a vibration type fluidized drying method, a spray drying method, a freeze drying method, a flash jet method or the like is preferable. The water content after drying is preferably adjusted to 1.5% by weight or less, more preferably 1.0% by weight or less, from the viewpoint of reducing the amount of toner scattered and charging properties.

<Toner for electrophotography>
(toner)
The particles obtained by drying and the like can be used as they are as the toner of the present invention, but those surface-treated as described below are preferably used as electrophotographic toners.
The softening point of the obtained toner is preferably 60 to 140 ° C., more preferably 65 to 130 ° C., and still more preferably 70 to 120 ° C., from the viewpoint of low temperature fixability and hot offset resistance of the toner. The glass transition point is preferably 30 to 80 ° C., more preferably 40 to 70 ° C. from the viewpoints of low-temperature fixability, durability, and storage stability.
The circularity of the toner is preferably 0.955 to 0.980, more preferably 0.958 to 0.980, and still more preferably 0.960 to 0, from the viewpoints of storage stability, chargeability and cleaning properties of the toner. .975. The circularity of the toner can be measured by the method described later. The circularity of the toner is a value obtained by the ratio of the circumference of the circle equal to the projected area / the circumference of the projected image. The more circular the particles are, the closer the circularity is to 1.
The volume median particle size of the toner is preferably 1 to 10 μm, more preferably 2 to 8 μm, still more preferably 3 to 7 μm, and still more preferably 4 to 6 μm, from the viewpoint of high image quality and productivity of the toner.
The CV value of the toner is preferably 30% or less, more preferably 27% or less, still more preferably 25% or less, and further preferably 22% or less, from the viewpoint of high image quality and productivity.

(External additive)
In the electrophotographic toner of the present invention, the toner particles can be used as the toner as they are, but it is preferable to use a toner obtained by adding a fluidizing agent or the like to the toner particle surface as an external additive. Examples of external additives include hydrophobic silica, titanium oxide fine particles, alumina fine particles, cerium oxide fine particles, inorganic fine particles such as carbon black, acrylic resin such as polycarbonate and polymethyl methacrylate, and polymer fine particles such as silicone resin. Among these, polymer fine particles and hydrophobic silica are preferable, and hydrophobic silica is more preferable.
When the surface treatment of toner particles is performed using an external additive, the amount of the external additive added is preferably 1 to 10 parts by weight, more preferably 100 parts by weight of the toner particles before the treatment with the external additive. 2 to 8 parts by weight, more preferably 3 to 6 parts by weight.
The electrophotographic toner obtained by the present invention can be used as a one-component developer or as a two-component developer mixed with a carrier.

Each property value of polyester, resin particles, toner, etc. was measured and evaluated by the following method.
[Acid value of polyester]
It measured according to JIS K0070. However, the measurement solvent was chloroform.

[Polyester softening point, endothermic maximum peak temperature, melting point and glass transition point]
(1) Softening point Using a flow tester (manufactured by Shimadzu Corporation, trade name: CFT-500D), a load of 1.96 MPa was applied by a plunger while heating a 1 g sample at a heating rate of 6 ° C / min. And extruded from a nozzle with a diameter of 1 mm and a length of 1 mm. The amount of flow tester drop by the flow tester was plotted against the temperature, and the temperature at which half the sample flowed out was taken as the softening point.
(2) Maximum peak temperature of endotherm, melting point and glass transition point The temperature was raised to 200 ° C. using a differential scanning calorimeter (manufactured by Parkin Elmer, trade name: Pyris 6 DSC), and the temperature lowering rate was 50 ° C./min. The sample cooled to 0 ° C. was measured at a heating rate of 10 ° C./min. Among the observed endothermic peaks, the temperature of the peak having the maximum peak area was defined as the maximum endothermic peak temperature. In the case of crystalline polyester, the peak temperature was taken as the melting point. In the case of an amorphous polyester, when an endothermic peak is observed, the temperature of the peak is measured, and when a step is observed without a peak being observed, the tangent indicating the maximum slope of the curve of the step and the step The glass transition point was defined as the temperature at the intersection with the base line extension line on the high temperature side.

[Glass transition point of resin particles]
First, the solvent was removed from the resin particle dispersion by freeze-drying to obtain a solid.
The lyophilization of the resin particle dispersion was carried out using a freeze dryer (manufactured by Tokyo Rika Kikai Co., Ltd., trade names: FDU-2100 and DRC-1000) with 30 g of the resin particle dispersion at −25 ° C. for 1 hour. Vacuum drying was performed at −10 ° C. for 10 hours and at 25 ° C. for 4 hours, and the moisture content was dried to 1% by weight or less. The moisture content was determined by using an infrared moisture meter (trade name: FD-230, manufactured by Kett Scientific Laboratory), drying 5 g of the sample at a drying temperature of 150 ° C. and a measurement mode 96 (monitoring time 2.5 minutes). / Fluctuation range 0.05%).
About the solid substance obtained after removing a solvent, the glass transition point of the resin particle was measured by the method similar to the measuring method of the glass transition point of the above-mentioned polyester.

[Number average molecular weight of polyester]
The molecular weight distribution was measured by gel permeation chromatography and the number average molecular weight was calculated by the following method.
(1) Preparation of sample solution Polyester was dissolved in chloroform so that the concentration was 0.5 g / 100 ml. Subsequently, this solution was filtered using a fluororesin filter having a pore size of 2 μm (manufactured by Sumitomo Electric Industries, Ltd., trade name: “FP-200”) to remove insoluble components to obtain a sample solution.
(2) Molecular weight distribution measurement Chloroform was allowed to flow as a lysis solution at a flow rate of 1 ml / min, and the column was stabilized in a constant temperature bath at 40 ° C. Measurement was performed by injecting 100 μl of the sample solution. The molecular weight of the sample was calculated based on a calibration curve prepared in advance. The calibration curve at this time includes several types of monodisperse polystyrene (monodisperse polystyrene manufactured by Tosoh Corporation; 2.63 × 10 ³ , 2.06 × 10 ⁴ , 1.02 × 10 ⁵ (weight average molecular weight), A monodisperse polystyrene manufactured by GL Sciences Inc .; 2.10 × 10 ³ , 7.00 × 10 ³ , 5.04 × 10 ⁴ (weight average molecular weight)) was used as a standard sample.
Measuring device: CO-8010 (trade name, manufactured by Tosoh Corporation)
Analytical column: GMHXL + G3000HXL (both trade names, manufactured by Tosoh Corporation)

[Volume Median Particle Size (D ₅₀ ) and Particle Size Distribution of Colored Particles, Resin Particles, and Release Agent Particles]
(1) Measuring device: Laser diffraction particle size measuring machine (Horiba, Ltd., trade name: LA-920)
(2) Measurement conditions: Distilled water was added to the measurement cell, and the volume-median particle size (D ₅₀ ) was measured at a temperature at which the absorbance falls within an appropriate range. The CV value was calculated according to the following formula.
CV value (%) = (standard deviation of particle size distribution / volume median particle size (D ₅₀ )) × 100

[Solid content concentration of colored particles and resin particle dispersion]
Using an infrared moisture meter (trade name: FD-230, manufactured by Ketto Scientific Laboratory Co., Ltd.), 5 g of colored particles or resin particle dispersion was measured at a drying temperature of 150 ° C., measurement mode 96 (monitoring time 2.5 minutes / variation) The moisture% was measured at a width of 0.05%. The solid content concentration was calculated according to the following formula.
Solid content concentration (% by weight) = 100-M
M: moisture (%) = [(W−W ₀ ) / W] × 100
W: Sample weight before measurement (initial sample weight)
W ₀ : Sample weight after measurement (absolute dry weight)

[Volume-median particle size (D ₅₀ ) of toner (particle), aggregated particle, and core-shell particle, number% of particle size of 2 μm or less, and particle size distribution]
The volume median particle size of the toner (particles) was measured as follows.
Measuring instrument: Coulter Multisizer III (trade name, manufactured by Beckman Coulter)
・ Aperture diameter: 50μm
・ Analysis software: Multisizer III version 3.51 (trade name, manufactured by Beckman Coulter)
Electrolyte: Isoton II (trade name, manufactured by Beckman Coulter)
-Dispersion: Polyoxyethylene lauryl ether (trade name, Emulgen 109P, HLB: 13.6, manufactured by Kao Corporation) was dissolved in the electrolytic solution to obtain a dispersion having a concentration of 5% by weight.
-Dispersion condition: 10 mg of a toner measurement sample is added to 5 mL of the dispersion, and dispersed for 1 minute with an ultrasonic disperser, and then 25 mL of electrolyte is added, and further dispersed for 1 minute with an ultrasonic disperser. A sample dispersion was prepared.
Measurement conditions: The sample dispersion is added to 100 mL of the electrolytic solution to adjust the particle size of 30,000 particles to a concentration that can be measured in 20 seconds, and then 30,000 particles are measured and the particle size distribution thereof. The volume-median particle size (D ₅₀ ) and the number percent of the particle size of 2 μm or less were determined.
The CV value (%) was calculated according to the following formula.
CV value (%) = (standard deviation of particle size distribution / volume median particle size (D ₅₀ )) × 100
The volume-median particle size of the agglomerated particles and the core-shell agglomerated particles was measured in the same manner by using the agglomerated particle dispersion and the core-shell particles as the sample dispersion in the measurement of the volume-median particle size of the toner (particles).

[Core shell particle, toner circularity]
-Preparation of dispersion: The dispersion of core-shell particles was diluted with deionized water so that the solid content concentration of the core-shell particles was 0.001 to 0.05%, and used as a sample dispersion. The toner dispersion was prepared by adding 50 mg of toner to 5 ml of 5 wt% polyoxyethylene lauryl ether (Emulgen 109P) aqueous solution, dispersing for 1 minute with an ultrasonic disperser, adding 20 ml of distilled water, A toner dispersion was obtained by dispersing for 1 minute using an ultrasonic disperser.
Measurement device: Flow-type particle image analyzer (manufactured by Sysmex Corporation, trade name: FPIA-3000)
・ Measurement mode: HPF measurement mode

[BET specific surface area of toner particles]
The BET specific surface area was measured using Micromeritics FlowSorbIII (trade name, manufactured by Shimadzu Corporation) under the following conditions.
Toner sample amount: 0.09 to 0.11 g
・ Deaeration condition: 40 ° C., 10 minutes ・ Adsorption gas: Nitrogen gas

[Toner fixability evaluation]
Using a commercially available printer (trade name: ML5400, manufactured by Oki Data Co., Ltd.), in which high-quality paper (manufactured by Fuji Xerox Co., Ltd., J paper A4 size) was loaded with the toner obtained in the examples and comparative examples. A solid image in which the toner adhesion amount on the paper is 0.45 ± 0.03 mg / cm ² is output as an unfixed image with a length of 50 mm, leaving a 5 mm margin from the top of the A4 paper. . The fixing device mounted on the printer was modified to have a variable temperature, and fixed at a temperature fixing speed of 34 sheets / minute (A4 vertical direction). The fixability of the obtained fixed image was evaluated by the following tape peeling method, and the fixable temperature range was measured.

(Tape peeling method)
Cut a mending tape (product name: Scotch mending tape 810, width 18 mm) to a length of 50 mm, and lightly affix it to the margin at the top of the fixed image. One reciprocal pressing was performed at 10 mm / sec. Thereafter, the applied tape is peeled off from the lower end side at a peeling angle of 180 degrees and at a speed of 10 mm / sec, and the reflected image density before and after the tape application is measured by a colorimeter (manufactured by Gretag-Macbeth, trade name: SpectroEye, lighting conditions; Measurement was performed using a standard light source D50, an observation visual field of 2 °, a density reference DINNB, and an absolute white reference), and the fixing rate was calculated from the following formula.
Fixing rate (%) = (image density after tape peeling / image density before tape application) × 100
When the image density after peeling becomes the same value as the image density before sticking the tape, the fixing rate is 100%, and the lower the value, the lower the fixability. A fixing rate of 90% or more is determined to be good fixability.

(Fixable temperature range)
The fixability test by the tape peeling method was performed at each fixing temperature in increments of 5 ° C., and the test was performed from a temperature at which a cold offset occurs or a temperature at which the fixing rate is less than 90% to a temperature at which a hot offset occurs. The cold offset is a phenomenon in which the toner on the unfixed image is not sufficiently melted and the toner adheres to the fixing roller when the fixing temperature is low. On the other hand, the hot offset is a temperature at which the fixing temperature is increased. In this case, the phenomenon is that the toner adheres to the fixing roller due to a decrease in the viscoelasticity of the toner on the unfixed image. The occurrence of cold offset or hot offset can be judged by whether or not toner adheres to the paper again when the fixing roller makes one round. In this test, whether toner adheres to the area 87 mm from the top of the solid image. Judged by no.
The toner fixability in the present invention was evaluated based on the minimum fixing temperature and the toner fixing temperature range (minimum fixing temperature to maximum fixing temperature). The wider the fixable temperature range, the better the fixing property, and the lower the minimum fixing temperature, the better the low temperature fixing property. Here, the minimum fixing temperature refers to the minimum temperature among the temperatures at which cold offset does not occur or the fixing rate is 90% or more, and the maximum fixing temperature is the temperature at which the hot offset occurs at −5 ° C. Say. The hot offset generation temperature is a temperature at which hot offset starts to occur.

[Toner durability evaluation]
A commercially available printer (Oki Data Co., Ltd., “ML5400”) is loaded with 80 g of toner, and an image with 1% printing information is printed up to 10,000 sheets using plain paper (Xerox Co., Ltd., J paper A4 size). The state of toner adhesion on the developing roller was observed every 1000 sheets, the presence or absence of blade filming was determined based on whether vertical stripes were observed, and the number of printed sheets until blade filming occurred was measured. The larger the number of printed sheets, the better the durability of the toner.

[Evaluation of storage stability of toner]
10 g of toner was put into a cylindrical polypropylene bottle (Nikko Corporation) having an internal volume of 20 ml, and left in an open state in an environment of a temperature of 50 ° C. and a relative humidity of 40% for 12 hours. After standing, set three sieves in the order of 250 μm upper opening, 150 μm middle opening and 75 μm lower opening on a powder tester (made by Hosokawa Micron Corporation), and put 2 g of toner on it for 60 seconds. Vibration was performed, and the weight of toner remaining on each sieve was measured. The measured toner weight was applied to the following equation to calculate the degree of aggregation [%].
Aggregation degree [%] = a + b + c
a = (weight of residual toner on upper stage) / 2 [g] × 100
b = (middle stage residual toner weight) / 2 [g] × 100 × (3/5)
c = (lower stage residual toner weight) / 2 [g] × 100 × (1/5)
The storage stability of the toner was evaluated according to the following criteria. The smaller the degree of aggregation, the better the storage stability of the toner.

Production Example 1
(Production of crystalline polyester (1))
The inside of a four-necked flask equipped with a nitrogen introduction tube, a dehydration tube, a stirrer, and a thermocouple was purged with nitrogen, and 3936 g of 1,9-nonanediol and 4848 g of sebacic acid were added. While stirring, the temperature was raised to 140 ° C., maintained at 140 ° C. for 3 hours, and then heated from 140 ° C. to 200 ° C. over 10 hours. Then, after adding 50 g of tin dioctanoate and maintaining at 200 ° C. for 1 hour, the pressure in the flask was lowered and maintained at 8.3 kPa for 4 hours to obtain a crystalline polyester (1). The melting point was 72 ° C. and the crystallinity index was 1.1. The acid value was 3.1 mgKOH / g, and the number average molecular weight was 6.1 × 10 ³ .

Production Example 2
(Production of amorphous polyester (1))
The inside of a four-necked flask equipped with a nitrogen introduction tube, a dehydration tube, a stirrer, and a thermocouple was replaced with nitrogen, and 1750 g of polyoxypropylene (2.2) -2,2-bis (4-hydroxyphenyl) propane, A nitrogen atmosphere containing 1625 g of polyoxyethylene (2.0) -2,2-bis (4-hydroxyphenyl) propane, 1145 g of terephthalic acid, 161 g of dodecenyl succinic anhydride, 480 g of trimellitic anhydride, and 10 g of dibutyltin oxide Under stirring, the temperature was raised to 220 ° C. and maintained at 220 ° C. for 5 hours. After confirming that the softening point measured according to ASTM D36-86 reached 120 ° C., the temperature was lowered to stop the reaction. Amorphous polyester (1) was obtained. The glass transition point was 65 ° C., the softening point was 122 ° C., and the crystallinity index was 1.6. The acid value was 21.0 mgKOH / g, and the number average molecular weight was 2.9 × 10 ³ .

Production Example 3
(Production of amorphous polyester (2))
The inside of a four-necked flask equipped with a nitrogen introduction tube, a dehydration tube, a stirrer, and a thermocouple was replaced with nitrogen, and 3374 g of polyoxypropylene (2.2) -2,2-bis (4-hydroxyphenyl) propane, Polyoxyethylene (2.0) -2,2-bis (4-hydroxyphenyl) propane (33 g), terephthalic acid (672 g) and dibutyltin oxide (10 g) were added, and the temperature was raised to 230 ° C. with stirring in a nitrogen atmosphere. After maintaining the time, the pressure in the flask was further reduced and maintained at 8.3 kPa for 1 hour. Then, after cooling to 210 ° C. and returning to atmospheric pressure, 696 g of fumaric acid and 0.49 g of tert-butylcatechol were added and maintained at a temperature of 210 ° C. for 5 hours. The amorphous polyester (2) was obtained by maintaining at 3 kPa for 4 hours. The glass transition point was 65 ° C., the softening point was 107 ° C., and the crystallinity index was 1.5. The acid value was 24.4 mgKOH / g, and the number average molecular weight was 3.0 × 10 ³ .

Production Example 4
(Production of colorant-containing resin particles (A) dispersion)
In a flask equipped with a stirrer, 90 g of crystalline polyester (1), 210 g of amorphous polyester (1), 300 g of amorphous polyester (2), copper phthalocyanine pigment (trade name: ECB301, Dainichi Seika Kogyo Co., Ltd.) 45 g, polyoxyethylene alkyl ether (nonionic surfactant, trade name: Emulgen 150, manufactured by Kao Corp.) 8.5 g, 15 wt% sodium dodecylbenzenesulfonate aqueous solution (anionic surfactant, product) Name: Neoperex G-15, manufactured by Kao Corporation) 80 g, 5 wt% aqueous potassium hydroxide solution 235 g was added, and the mixture was stirred and heated to 98 ° C., melted, and mixed at 98 ° C. for 2 hours. A resin mixture was obtained.
Next, 1146 g of deionized water was added dropwise at a rate of 6 g / min while stirring to obtain an emulsion. Next, the obtained emulsion was cooled to 25 ° C., and a colorant-containing resin particle (A) dispersion was obtained through a 200-mesh (mesh 105 μm) wire mesh. The solid content concentration of the obtained dispersion was 32% by weight, the volume median particle size of the resin particles (A) in the dispersion was 0.227 μm, and the CV value was 27%.

Production Example 5
(Production of resin particle (B) dispersion containing amorphous polyester)
In a reaction vessel having an internal volume of 5 liters, in a flask, 200 g of amorphous polyester (1), 390 g of amorphous polyester (2), polyoxyethylene alkyl ether (nonionic surfactant, trade name: Emulgen 430, Kao 6 g, 15 wt% sodium dodecylbenzenesulfonate aqueous solution (Neopelex G-15) 40 g and 5 wt% potassium hydroxide 268 g were added, and the mixture was heated to 95 ° C and melted with stirring. The mixture was mixed at 0 ° C. for 2 hours to obtain a resin mixture.
Next, 1145 g of deionized water was added dropwise at a rate of 6 g / min while stirring to obtain an emulsion. Next, the obtained emulsion was cooled to 25 ° C., passed through a 200-mesh wire mesh, deionized water was added to adjust the solid content to 23% by weight, and resin particles containing amorphous polyester ( B) A dispersion was obtained. The volume median particle size of the resin particles (B) in the dispersion was 0.158 μm, the CV value was 24%, and the glass transition point was 60 ° C.

Production Example 6
(Production of release agent particle dispersion)
In a beaker having an internal volume of 1 liter, 480 g of deionized water, 4.29 g of an alkenyl (mixture of hexadecenyl group and octadecenyl group) dipotassium succinate (trade name: Latemulu ASK, Kao Corporation, effective concentration 28% by weight), 120 g of carnauba wax (produced by Hiroyuki Kato, melting point 85 ° C., acid value 5 mgKOH / g) was added and stirred. While maintaining the mixture at 90 to 95 ° C., the mixture was subjected to a dispersion treatment for 30 minutes using an ultrasonic disperser (trade name: Ultrasonic Homogenizer 600W, manufactured by Nippon Seiki Seisakusho Co., Ltd.), and then cooled to 25 ° C. Then, deionized water was added to adjust the solid content to 20% by weight to obtain a release agent particle dispersion. The volume median particle size of the release agent particles was 0.494 nm, and the CV value was 34%.

Example 1
(Preparation of Toner A)
<Step (1): Production of Aggregated Particle Dispersion>
In a 10-liter four-necked flask equipped with a dehydrating tube, a stirrer and a thermocouple, 200 g of the colorant-containing resin particle (A) dispersion, 52 g of deionized water, and 33 g of the release agent particle dispersion are placed. Mixed at 25 ° C. Next, while stirring the mixture, an aqueous solution in which 16.7 g of ammonium sulfate was dissolved in 174 g of deionized water was dropped at 25 ° C. over 10 minutes, and then the temperature was raised to 48 ° C. over 2 hours. The mixture was kept at 48 ° C. until the median particle size became 4.2 μm to obtain an aggregated particle dispersion. The aggregating agent concentration in the aggregated particle dispersion was 0.65 mol / L.
<Process (2): Preparation of core-shell particle dispersion (1)>
The aggregated particle dispersion obtained in step (1) was kept at 48 ° C., and 50 g of resin particle (B) dispersion containing amorphous polyester was added dropwise at a rate of 0.3 g / min. After completion of dropping, 75 g of resin particle (B) dispersion containing amorphous polyester was added dropwise at a rate of 0.3 g / min while raising the temperature to 55 ° C. over 4 hours. A 5.1 μm core-shell particle dispersion (1) was obtained. The resulting core-shell particle dispersion (1) had a flocculant concentration of 0.52 mol / L. Furthermore, an aqueous solution obtained by dissolving 16 g of sodium alkyl ether sulfate (trade name: EMAL E27C, manufactured by Kao Corporation, solid content 28 wt%) in 1252 g of deionized water was added to the core-shell particle dispersion (1) and mixed. .
<Process (3): Preparation of core-shell particle dispersion (2)>
The dispersion obtained in step (2) was cooled to 25 ° C., and an aqueous magnesium sulfate solution in which 0.83 g of magnesium sulfate was dissolved in 10 g of deionized water was continuously added dropwise, and the mixture was sufficiently stirred and mixed. . As a result, a core-shell particle dispersion (2) containing a salt having a cation having a higher valence than the flocculant was obtained.
<Process (4): Preparation of core-shell particle dispersion (3)>
The dispersion obtained in step (3) was heated to 65 ° C. over 2 hours and then held at 65 ° C. for 3 hours to obtain a core-shell particle dispersion (3) having a circularity of 0.959. Then, it cooled to 25 degreeC. The concentration of the flocculant in the system was 0.14 mol / L.
<Post-processing process>
The core-shell particle dispersion (3) obtained in the step (4) was suction filtered, washed with deionized water, and dried at 33 ° C. to obtain toner particles. 100 parts by weight of the toner particles, 2.5 parts by weight of hydrophobic silica (trade name: RY50, manufactured by Nippon Aerosil Co., Ltd., average particle size: 0.04 μm), and hydrophobic silica (trade name: Cabo Seal TS720, Cabot Corporation) Manufactured, average particle size: 0.012 μm) was put in a Henschel mixer, stirred, and passed through a 150-mesh sieve to obtain toner A. The volume-median particle diameter of the obtained toner A was 5.1 μm, and the number percent of 2 μm or less was 3.4%. Table 1 shows the physical properties and evaluation results of Toner A.

Example 2
(Preparation of Toner B)
In the step (3) of Example 1, the magnesium sulfate aqueous solution was changed to a magnesium chloride aqueous solution in which 1.4 g of magnesium chloride hexahydrate was dissolved in 9.3 g of deionized water. Thus, Toner B was obtained. Table 1 shows the physical properties and evaluation results of Toner B.

Example 3
(Preparation of toner C)
Toner C is obtained in the same manner as in Example 1 except that in step (3) of Example 1, the magnesium sulfate aqueous solution is changed to an aluminum chloride aqueous solution in which 0.34 g of aluminum chloride is dissolved in 5 g of deionized water. It was. Table 1 shows the physical properties and evaluation results of Toner C.

Comparative Example 1 (Production of Toner D)
In Example 1, Toner D was prepared in the same manner as in Example 1 except that the magnesium sulfate aqueous solution was not added in Step (3). Table 1 shows the physical properties and evaluation results of Toner D.

Comparative Example 2 (Production of Toner E)
Toner E was obtained in the same manner as in Example 1 except that in step (3) of Example 1, the magnesium sulfate aqueous solution was changed to an ammonium sulfate aqueous solution in which 16.7 g of ammonium sulfate was dissolved in 174 g of deionized water. Table 1 shows the physical properties and evaluation results of Toner E.

Example 4
(Production of Toner F)
The same procedure was performed up to step (3) in Example 1.
<Step (4): Preparation of core-shell particle dispersion (3a)>
The dispersion obtained in step (3) was heated to 65 ° C. over 2 hours and then held at 65 ° C. for 2 hours to obtain a core-shell particle dispersion (3) having a circularity of 0.953. Then, it cooled to 25 degreeC.
<Step (5): Preparation of core-shell particle dispersion (3b)>
Attach the Buchner funnel to a 10L suction bottle, place a filter paper of diameter 285mm (Tokyo Glass Instrument Co., Ltd., circular qualitative filter paper # 2) on the Buchner funnel, and suck the core-shell particle dispersion (3) while pulling a vacuum. Filtration was performed to remove an aqueous medium containing a flocculant as a filtrate to obtain a slurry having a solid content of 35%.
After adding deionized water at 25 ° C. to 270 g of this slurry to make the total weight 601 g, an aqueous solution in which 16 g of sodium alkyl ether sulfate (Emar E27C, solid content 28%) was dissolved in 1252 g of deionized water was added. Further, a magnesium sulfate aqueous solution in which 0.83 g of magnesium sulfate was dissolved in 10 g of deionized water was added, mixed, and mixed at 25 ° C. using a stirrer.
As a result, a core-shell particle dispersion (3b) having a flocculant concentration of 0.026 mol / L was obtained.
The obtained core-shell particle dispersion (3b) was heated to 65 ° C. over 1 hour and then held at 65 ° C. When the circularity reached 0.967, the heating was terminated and cooled to 25 ° C.
Thereafter, the same process as the <post-treatment process> in Example 1 was performed to obtain toner F. Table 1 shows the physical properties and evaluation results of Toner F.

Example 5
(Preparation of toner G)
In the same manner as in Example 4 except that the magnesium sulfate aqueous solution was changed to a magnesium chloride aqueous solution in which 1.4 g of magnesium chloride hexahydrate was dissolved in 9.3 g of deionized water in the step (3) of Example 4. Thus, toner G was obtained. Table 1 shows the physical properties and evaluation results of Toner G.

Example 6
(Preparation of Toner H)
Toner H is obtained in the same manner as in Example 4, except that in step (3) of Example 4, the magnesium sulfate aqueous solution is changed to an aluminum chloride aqueous solution in which 0.34 g of aluminum chloride is dissolved in 5 g of deionized water. It was. Table 1 shows the physical properties and evaluation results of Toner H.

Comparative Example 2 (Production of Toner I)
In Example 4, Toner I was prepared in the same manner as in Example 4 except that the magnesium sulfate aqueous solution was not added during the process. Table 1 shows the physical properties and evaluation results of Toner I.

Comparative Example 4 (Production of Toner J)
Toner J was obtained in the same manner as in Example 4, except that in step (3) of Example 4, the magnesium sulfate aqueous solution was changed to a magnesium chloride aqueous solution in which 16.7 g of ammonium sulfate was dissolved in 174 g of deionized water. . Table 1 shows the physical properties and evaluation results of Toner J.

  From Table 1, the electrophotographic toners of the examples obtained by the electrophotographic toner manufacturing method of the present invention are excellent in fixability, and are excellent in durability and storage stability as compared with the toners of the comparative examples. It can be seen that both of these can be achieved.

Claims (11)

A method for producing an electrophotographic toner comprising the following steps (1) to (4):
Step (1): A step of mixing a flocculant composed of colored particles, release agent particles, and an electrolyte in an aqueous medium to obtain an agglomerated particle dispersion Step (2): An amorphous polyester is added to the agglomerated particle dispersion. After adding the resin particles (B) containing (b) , an anionic surfactant is added to obtain the core-shell particle dispersion (1) Step (3): In the core-shell particle dispersion (1), A step of adding a salt having a cation having a valence higher than that of the flocculant to obtain a core-shell particle dispersion (2) Step (4): A step of obtaining a core-shell particle dispersion (3a) by holding at a temperature of 5 ° C. lower than the glass transition point of the crystalline polyester (b) 2. The method for producing an electrophotographic toner according to claim 1 , wherein in step (4), the temperature at which the core-shell particle dispersion liquid (2) is retained is less than a temperature that is 10 ° C. lower than the melting point of the release agent .   The method for producing an electrophotographic toner according to claim 1, wherein the cation valence of the electrolyte constituting the flocculant is 1.   The method for producing an electrophotographic toner according to claim 1, wherein the electrolyte constituting the flocculant is an inorganic ammonium salt.   The method for producing an electrophotographic toner according to any one of claims 1 to 4, wherein the cation valence of the salt is 2 or 3.   The method for producing an electrophotographic toner according to claim 1, wherein the salt used in the step (3) is a magnesium salt. The method for producing an electrophotographic toner according to claim 1, comprising the following step (5) after the step (4).
Step (5): Removing at least a part of the flocculant and the aqueous medium from the core-shell particle dispersion (3a) to obtain a slurry, and adding a salt having a cation having a valence higher than that of the flocculant to the slurry. And a step of obtaining a core-shell particle dispersion (3b) by holding at a temperature not higher than the melting point of the release agent and not lower than 5 ° C. from the glass transition point of the amorphous polyester (b).   The method for producing an electrophotographic toner according to any one of claims 1 to 7, wherein the amorphous polyester (b) has a glass transition point of 55 to 75 ° C.   The method for producing an electrophotographic toner according to claim 1, wherein the colored particles are colorant-containing resin particles (A) containing a colorant.   The toner for electrophotography according to any one of claims 1 to 9, wherein the concentration of the flocculant in the core-shell particle dispersion (3a) is not more than 0.65 times the concentration of the flocculant in the core-shell particle dispersion (1). Manufacturing method.   The temperature at which the core-shell particle dispersion (2) is maintained in the step (4) is at least the glass transition point of the resin particles (B) containing the amorphous polyester (b). A process for producing an electrophotographic toner as described in 1 above.