JP7686345B2 - Toner for developing electrostatic images - Google Patents

Description

The present invention relates to a toner for developing electrostatic images.

In image forming apparatuses such as electrophotographic apparatuses, electrostatic recording apparatuses, and electrostatic printing apparatuses, a technique is widely used in which a desired image is formed by developing an electrostatic latent image formed on a photoconductor with a toner for developing an electrostatic image. Such a technique is applied to copying machines, printers, facsimiles, and multifunction machines thereof.
In recent years, in response to the demand for forming images with higher definition and image quality, toners for developing electrostatic images using toner base particles having a high degree of circularity have been used.
Patent Document 1 describes a toner having a core-shell structure, with the aim of providing a toner that can exhibit excellent polishing performance and improve cleaning performance, characterized in that the shell layer of the toner contains fine abrasive particles having an average particle size of 0.1 to 1.0 μm in a ratio of 0.3 to 3.0 parts by weight per 100 parts by weight of the toner.
Furthermore, Patent Document 2 describes a toner for developing electrostatic images which is unlikely to cause filming on a photoreceptor, imparts toner particles with stable chargeability over time, and is unlikely to cause deterioration in image quality due to fogging or the like even when a large number of sheets are continuously printed, particularly in a high-temperature, high-humidity environment, and contains, as external additives, specific amounts of fatty acid zinc particles having a number-average primary particle size of 0.5 to 1.5 μm, silica fine particles (A) having a solid average primary particle size of 5 to 20 nm, and silica fine particles (B) having a number-average primary particle size of 25 to 80 nm.

JP 2007-187988 A JP 2011-203666 A

The toners for developing electrostatic images described in Patent Documents 1 and 2 have problems in that the toner charge amount is not sufficiently uniform, and the occurrence of fogging cannot be sufficiently suppressed. In addition, there has been no consideration on optimizing the amount of toner transported.
The present invention relates to providing a toner for developing electrostatic images, which suppresses the occurrence of fog even during continuous printing under conditions of low toner consumption, and further provides a highly stable image density.

The inventors have discovered that the above problem can be solved by externally adding small silica particles and large silica particles having specific particle sizes in a specific ratio to toner base particles having a high degree of circularity.

That is, the present invention relates to the following [1].
[1] Toner base particles having a circularity of 0.965 or more,
small-diameter silica particles having a particle size of 10 nm or more and 30 nm or less calculated from a specific surface area;
Large-diameter silica particles having a particle diameter of 70 nm or more and 190 nm or less calculated from the specific surface area are externally added,
the mass ratio of the large silica particles to the small silica particles (large silica particles/small silica particles) is 7 or more and 18 or less;
Toner for developing electrostatic images.

According to the present invention, it is possible to provide a toner for developing electrostatic images that suppresses the occurrence of fog even during continuous printing with low toner consumption, and that also provides highly stable image density.

[Toner for developing electrostatic images]
The toner for developing electrostatic images of the present invention (hereinafter, also simply referred to as "toner") comprises toner base particles having a circularity of 0.965 or more, to which small-sized silica particles having a particle size converted from the specific surface area of 10 nm or more and 30 nm or less, and large-sized silica particles having a particle size converted from the specific surface area of 70 nm or more and 190 nm or less, and the mass ratio of the amount of the large-sized silica particles to the small-sized silica particles (large-sized silica particles/small-sized silica particles) added is 7 or more and 18 or less.
In the following description, the toner for developing electrostatic images contains toner base particles and an external additive, and is preferably composed of toner base particles and an external additive. Each particle of the toner for developing electrostatic images is also referred to as a "toner particle."

In the non-magnetic one-component development method, the toner conveyed from the developing roller is required to be instantly and uniformly triboelectrically charged when passing through the developing blade, but with toner with high circularity, the friction between the developing blade and the toner particles is small, making it difficult to uniformly triboelectrically charge the toner, which can lead to the problem of fogging.In addition, the friction between the developing roller and the toner particles is also small, so the toner is less likely to get caught on the developing roller, making it impossible to ensure a stable conveyance amount, which can lead to problems such as the inability to guarantee image density.
According to the present invention, there is provided a toner for developing electrostatic images which suppresses fogging even during continuous printing under conditions of low toner consumption and further provides highly stable image density.
The reason why the above effect is obtained is not clear, but is thought to be as follows.
By combining small particle size silica, with a particle size converted from the specific surface area of 10 nm or more and 30 nm or less, and large particle size silica, with a particle size converted from the specific surface area of 70 nm or more and 190 nm or less, as external additives in a specific addition ratio, it is believed that the external additive creates minute surface irregularities on the toner surface, improving the effect of frictional charging between the developing blade and the toner particles, thereby improving the uniformity of the toner charging and suppressing fogging.
On the other hand, if the friction between the developing blade and the toner particles is improved, the friction between the developing roller and the toner particles also increases, and the amount of toner transported on the developing roller increases. If the friction between the developing roller and the toner particles increases excessively, toner leakage is likely to occur from the gap between the developing roller and the developing blade, but in the present invention, by applying the addition ratio of a specific external additive, the friction force between the developing roller and the toner particles does not increase more than necessary, so that the amount of toner transported is optimized and the occurrence of toner leakage is suppressed.
The above-mentioned mechanism regarding the effect of the present invention is merely a presumption, and the present invention is not limited thereto.

The definitions of various terms used in this specification are given below.
Whether a resin is crystalline or amorphous is determined by the crystallinity index. The crystallinity index is defined as the ratio of the softening point of the resin to the maximum endothermic peak temperature (softening point (°C)/maximum endothermic peak temperature (°C)) in the measurement method described in the examples below. A crystalline resin is one with a crystallinity index of 0.6 or more and 1.4 or less. An amorphous resin is one in which no endothermic peak is observed, or if an endothermic peak is observed, the crystallinity index is less than 0.6 or more than 1.4. The crystallinity index can be appropriately adjusted by the type and ratio of raw material monomers, as well as production conditions such as reaction temperature, reaction time, and cooling rate.
In the specification, the carboxylic acid component of the polyester resin includes not only the compound itself, but also anhydrides that decompose during the reaction to produce an acid, and alkyl esters of each carboxylic acid (alkyl groups having 1 to 3 carbon atoms).
The "volume median particle size (D ₅₀ )" is the particle size at which the cumulative volume frequency calculated as a volume fraction is 50%, calculated from the smallest particle size.
The coefficient of variation of particle size distribution (hereinafter, simply referred to as "CV value") is a value expressed by the following formula: In the following formula, the volume average particle size is a particle size obtained by multiplying the particle size of all measured particles by the volume of the particle, and dividing the sum by the total volume of the measured particles.
CV value (%) = [standard deviation of particle size distribution (μm) / volume average particle size (μm)] × 100

<Toner Base Particles>
In the present invention, the circularity of the toner base particles is 0.965 or more. When the circularity is 0.965 or more, a high-definition image can be obtained.
The circularity of the toner base particles is, from the viewpoint of obtaining a high-definition image, 0.965 or more, preferably 0.968 or more, more preferably 0.970 or more, and from the viewpoint of further suppressing the occurrence of fog, is preferably 0.995 or less, more preferably 0.990 or less, even more preferably 0.985 or less, and still more preferably 0.980 or less.
The circularity of the toner base particles is measured by the method described in the examples.

The toner base particles contain a binder resin, and preferably contain a colorant and a release agent in addition to the binder resin.
The toner base particles may be obtained by any known method such as a melt kneading method, an emulsion phase inversion method, a polymerization method, or an aggregation fusion method. From the viewpoint of obtaining a desired circularity, however, toner base particles obtained by an aggregation fusion method are preferred, and toner base particles having a core-shell structure are more preferred.
A preferred embodiment of the toner base particles will be described below, but in the present invention, the toner base particles are not particularly limited as long as they have the above-mentioned circularity.

[Binder Resin]
From the viewpoint of achieving excellent low-temperature fixing properties and a desired circularity, the toner base particles preferably contain a polyester resin as a binder resin, more preferably contain an amorphous polyester resin A, and even more preferably contain an amorphous polyester resin A and a crystalline polyester resin C.

<Amorphous polyester resin A>
In the present invention, the toner base particles preferably contain the amorphous polyester resin A as a binder resin, and more preferably the core portion contains the amorphous polyester resin A.
The amorphous polyester resin A is, for example, an amorphous polyester resin containing a polycondensate of an alcohol component and a carboxylic acid component.
Examples of the amorphous polyester resin include polyester resin and modified polyester resin. Examples of the modified polyester resin include urethane modified polyester resin, epoxy modified polyester resin, and composite resin containing polyester resin segment and addition polymerization resin segment. Among these, it is preferable to use an amorphous composite resin containing a polyester resin segment which is a polycondensation product of an alcohol component and a carboxylic acid component, and an addition polymerization resin segment which is an addition polymerization product of a raw material monomer containing a styrene-based compound.

Examples of the alcohol component include alkylene oxide adducts of aromatic diols, linear or branched aliphatic diols, alicyclic diols, and trihydric or higher polyhydric alcohols. Among these, alkylene oxide adducts of aromatic diols are preferred from the viewpoint of obtaining a toner having excellent low-temperature fixing properties.
The alkylene oxide adduct of an aromatic diol is preferably an alkylene oxide adduct of bisphenol A, more preferably represented by formula (I):

(wherein ^OR1 and ^R2O are oxyalkylene groups, ^R1 and ^R2 each independently represent an ethylene group or a propylene group, x and y each represent the average number of moles of alkylene oxide added and are positive numbers, and the sum of x and y is 1 or more and 16 or less).

Examples of the alkylene oxide adduct of bisphenol A include a propylene oxide adduct of bisphenol A [2,2-bis(4-hydroxyphenyl)propane] and an ethylene oxide adduct of bisphenol A. These may be used alone or in combination. Among these, the propylene oxide adduct of bisphenol A is preferred.
The content of the alkylene oxide adduct of bisphenol A in the alcohol component is preferably 70 mol % or more, more preferably 90 mol % or more, even more preferably 95 mol % or more, and is 100 mol % or less, even more preferably 100 mol %.

Examples of linear or branched aliphatic diols include ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, 2,2-dimethyl-1,3-propanediol, 1,6-hexanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, and 1,12-dodecanediol.
Examples of the alicyclic diol include hydrogenated bisphenol A [2,2-bis(4-hydroxycyclohexyl)propane] and alkylene oxide adducts of hydrogenated bisphenol A having 2 to 4 carbon atoms (average molar number added: 2 to 12).
Examples of trihydric or higher polyhydric alcohols include glycerin, pentaerythritol, trimethylolpropane, and sorbitol.
These alcohol components may be used alone or in combination of two or more.

Examples of the carboxylic acid component include dicarboxylic acids and polycarboxylic acids having three or more carboxylic acids.
Examples of the dicarboxylic acid include aromatic dicarboxylic acids, linear or branched aliphatic dicarboxylic acids, and alicyclic dicarboxylic acids. Among these, at least one selected from aromatic dicarboxylic acids and linear or branched aliphatic dicarboxylic acids is preferred.
Examples of aromatic dicarboxylic acids include phthalic acid, isophthalic acid, and terephthalic acid. Among these, isophthalic acid and terephthalic acid are preferred, and terephthalic acid is more preferred.
The amount of aromatic dicarboxylic acid in the carboxylic acid component is preferably 20 mol% or more, more preferably 30 mol% or more, even more preferably 40 mol% or more, even more preferably 50 mol% or more, and is preferably 90 mol% or less, more preferably 85 mol% or less, even more preferably 80 mol% or less.

The linear or branched aliphatic dicarboxylic acid preferably has 2 or more carbon atoms, more preferably 3 or more carbon atoms, and preferably has 30 or less, more preferably 20 or less carbon atoms.
Examples of linear or branched aliphatic dicarboxylic acids include oxalic acid, malonic acid, maleic acid, fumaric acid, citraconic acid, itaconic acid, glutaconic acid, succinic acid, adipic acid, sebacic acid, dodecanedioic acid, azelaic acid, and succinic acid substituted with an aliphatic hydrocarbon group having 1 to 20 carbon atoms. Examples of succinic acid substituted with an aliphatic hydrocarbon group having 1 to 20 carbon atoms include dodecylsuccinic acid, dodecenylsuccinic acid, and octenylsuccinic acid. Among these, fumaric acid, sebacic acid, and succinic acid substituted with an aliphatic hydrocarbon group having 1 to 20 carbon atoms are preferred, and fumaric acid and sebacic acid are more preferred.
The amount of the linear or branched aliphatic dicarboxylic acid in the carboxylic acid component is preferably 1 mol % or more, more preferably 3 mol % or more, even more preferably 10 mol % or more, and is preferably 80 mol % or less, more preferably 50 mol % or less, even more preferably 30 mol % or less.

The trivalent or higher polyvalent carboxylic acid is preferably a trivalent carboxylic acid, for example, trimellitic acid, preferably trimellitic acid or its anhydride.
When a trivalent or higher polycarboxylic acid is contained, the amount of the trivalent or higher polycarboxylic acid in the carboxylic acid component is preferably 3 mol % or more, more preferably 5 mol % or more, even more preferably 8 mol % or more, and is preferably 30 mol % or less, more preferably 25 mol % or less, even more preferably 20 mol % or less.
These carboxylic acid components may be used alone or in combination of two or more.

The equivalent ratio of the carboxyl groups of the carboxylic acid component to the hydroxyl groups of the alcohol component [COOH groups/OH groups] is preferably 0.7 or more, more preferably 0.8 or more, and is preferably 1.3 or less, more preferably 1.2 or less.

The addition polymerized resin segment is, for example, an addition polymer of raw material monomers including a styrene-based compound.
Examples of the styrene-based compound include unsubstituted or substituted styrene. Examples of the substituent substituted on the styrene include an alkyl group having 1 to 5 carbon atoms, a halogen atom, an alkoxy group having 1 to 5 carbon atoms, a sulfonic acid group, or a salt thereof.
Examples of styrene-based compounds include styrene, methylstyrene, α-methylstyrene, β-methylstyrene, tert-butylstyrene, chlorostyrene, chloromethylstyrene, methoxystyrene, styrenesulfonic acid, and salts thereof. Among these, styrene is preferred.
In the raw material monomers for the addition polymerization resin segment, the content of the styrene-based compound is preferably 50% by mass or more, more preferably 65% by mass or more, even more preferably 75% by mass or more, and is 100% by mass or less, preferably 95% by mass or less, more preferably 90% by mass or less, even more preferably 85% by mass or less.

Examples of raw material monomers other than styrene-based compounds include (meth)acrylic acid esters such as alkyl (meth)acrylate, benzyl (meth)acrylate, and dimethylaminoethyl (meth)acrylate; olefins such as ethylene, propylene, and butadiene; halovinyls such as vinyl chloride; vinyl esters such as vinyl acetate and vinyl propionate; vinyl ethers such as methyl vinyl ether; vinylidene halides such as vinylidene chloride; and N-vinyl compounds such as N-vinylpyrrolidone. Among these, (meth)acrylic acid esters are preferred, and alkyl (meth)acrylates are more preferred.
The number of carbon atoms in the alkyl group in the alkyl (meth)acrylate is preferably 1 or more, more preferably 4 or more, even more preferably 6 or more, and is preferably 24 or less, more preferably 22 or less, even more preferably 20 or less.
Examples of the alkyl (meth)acrylate include methyl (meth)acrylate, ethyl (meth)acrylate, (iso)propyl (meth)acrylate, (iso or tertiary)butyl (meth)acrylate, (iso)amyl (meth)acrylate, cyclohexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, (iso)octyl (meth)acrylate, (iso)decyl (meth)acrylate, (iso)dodecyl (meth)acrylate, (iso)palmityl (meth)acrylate, (iso)stearyl (meth)acrylate, and (iso)behenyl (meth)acrylate. Of these, 2-ethylhexyl (meth)acrylate or stearyl (meth)acrylate is preferred, 2-ethylhexyl acrylate and stearyl methacrylate are more preferred, and stearyl methacrylate is even more preferred.
In addition, "(iso or tertiary)" and "(iso)" refer to both the presence and absence of these prefixes, and the absence of these prefixes refers to normal. In addition, "(meth)acrylic acid" refers to acrylic acid or methacrylic acid.

In the raw material monomers for the addition polymerization resin segment, the content of the (meth)acrylic acid ester is preferably 5 mass% or more, more preferably 10 mass% or more, even more preferably 15 mass% or more, and is preferably 50 mass% or less, more preferably 35 mass% or less, even more preferably 25 mass% or less.
The total amount of the styrene-based compound and the (meth)acrylic acid ester in the raw material monomers of the addition polymerization resin segment is preferably 80 mass % or more, more preferably 90 mass % or more, even more preferably 95 mass % or more, and still more preferably 100 mass %.

The amorphous polyester resin A preferably has a constitutional unit derived from a bireactive monomer bonded to a polyester resin segment and an addition polymerization resin segment via a covalent bond.
The term "structural unit derived from a bireactive monomer" refers to a unit formed by reaction of a functional group and an addition polymerizable group of a bireactive monomer.
An example of the addition polymerizable group is a carbon-carbon unsaturated bond (ethylenically unsaturated bond).
Examples of the bireactive monomer include addition polymerizable monomers having at least one functional group selected from a hydroxyl group, a carboxyl group, an epoxy group, a primary amino group, and a secondary amino group in the molecule. Among these, from the viewpoint of reactivity, addition polymerizable monomers having at least one functional group selected from a hydroxyl group and a carboxyl group are preferred, and addition polymerizable monomers having a carboxyl group are more preferred.
Examples of the addition polymerizable monomer having a carboxy group include acrylic acid, methacrylic acid, fumaric acid, and maleic acid. Among these, from the viewpoint of reactivity in both the polycondensation reaction and the addition polymerization reaction, acrylic acid and methacrylic acid are preferred, and acrylic acid is more preferred.
When the bireactive monomer is an addition polymerizable monomer having a carboxy group, the amount of the constitutional units derived from the bireactive monomer is preferably 1 mol part or more, more preferably 5 mol parts or more, even more preferably 8 mol parts or more, and is preferably 30 mol parts or less, more preferably 25 mol parts or less, even more preferably 20 mol parts or less, relative to 100 mol parts of the alcohol component of the polyester resin segment of the amorphous polyester resin A.

The amorphous polyester resin A may further contain, in addition to the polyester resin segment and the addition polymerization resin segment, a structural unit derived from a hydrocarbon wax having at least one of a carboxy group and a hydroxyl group (structural unit derived from a hydrocarbon wax).

The content of the polyester resin segment in the amorphous polyester resin A is preferably 40% by mass or more, more preferably 45% by mass or more, and even more preferably 55% by mass or more, based on the total amount of the polyester resin segment and the addition polymerization resin segment, and is preferably 95% by mass or less, more preferably 85% by mass or less, and even more preferably 75% by mass or less. The structural unit derived from the bireactive monomer is a polyester resin segment.

The content of the addition polymerization resin segment in the amorphous polyester resin A is preferably 5% by mass or more, more preferably 15% by mass or more, and even more preferably 25% by mass or more, based on the total amount of the polyester resin segment and the addition polymerization resin segment, and is preferably 60% by mass or less, more preferably 55% by mass or less, and even more preferably 45% by mass or less. The structural unit derived from the bireactive monomer is a polyester resin segment.

The amount of the bireactive monomer-derived structural units in the amorphous polyester resin A is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, even more preferably 0.8% by mass or more, and is preferably 10% by mass or less, more preferably 7% by mass or less, even more preferably 4% by mass or less, based on the total amount of the polyester resin segment and the addition polymerization resin segment.

The amount of structural units derived from the hydrocarbon wax in the amorphous polyester resin A is preferably 10 parts by mass or less, more preferably 8 parts by mass or less, and even more preferably 6 parts by mass or less, per 100 parts by mass of the total amount of the polyester resin segment and the addition polymerization resin segment.

The above amounts are calculated based on the ratio of the amounts of the polyester resin segment, raw material monomer for the addition polymerization resin segment, bireactive monomer, and radical polymerization initiator, and are based on the mass excluding the amount of dehydration due to polycondensation in the polyester resin segment, etc. When a radical polymerization initiator is used, the mass of the radical polymerization initiator is included in the addition polymerization resin segment in the calculation.

The amorphous polyester resin A may be produced, for example, by a method including a step A of polycondensing an alcohol component and a carboxylic acid component, and a step B of addition polymerizing a raw material monomer for the addition polymerization resin segment and a bireactive monomer.
In the case where the amorphous polyester resin A further contains a structural unit derived from a hydrocarbon wax, in the above-mentioned step A, for example, a polycondensation reaction of an alcohol component and a carboxylic acid component is carried out in the presence of a hydrocarbon wax having at least one of a hydroxyl group and a carboxyl group.
Step B may be carried out after step A, step A may be carried out after step B, or step A and step B may be carried out simultaneously.
In the step A, a part of the carboxylic acid component is subjected to a polycondensation reaction, and then the step B is carried out, and thereafter the remainder of the carboxylic acid component is added to the polymerization system to further proceed with the polycondensation reaction of the step A and the polycondensation reaction with the carboxy group of the bireactive monomer or the constituent moiety derived from the bireactive monomer.

In step A, if necessary, polycondensation may be performed using an esterification catalyst such as tin(II) di(2-ethylhexanoate), dibutyltin oxide, or titanium diisopropoxybis(triethanolaminate) in an amount of 0.01 part by mass or more and 5 parts by mass or less per 100 parts by mass of the total amount of the alcohol component and the carboxylic acid component; or an esterification promoter such as gallic acid (equivalent to 3,4,5-trihydroxybenzoic acid) in an amount of 0.001 part by mass or more and 0.5 part by mass or less per 100 parts by mass of the total amount of the alcohol component and the carboxylic acid component.
When a monomer having an unsaturated bond such as fumaric acid is used in polycondensation, a radical polymerization inhibitor may be used, if necessary, in an amount of preferably 0.001 part by mass or more and 0.5 part by mass or less per 100 parts by mass of the total amount of the alcohol component and the carboxylic acid component. An example of the radical polymerization inhibitor is 4-tert-butylcatechol.
The temperature of the polycondensation reaction is preferably 120° C. or higher, more preferably 160° C. or higher, and even more preferably 180° C. or higher, and is preferably 250° C. or lower, and more preferably 240° C. or lower. The polycondensation may be carried out in an inert gas atmosphere.

Examples of the radical polymerization initiator for the addition polymerization in step B include peroxides such as dibutyl peroxide, persulfates such as sodium persulfate, and azo compounds such as 2,2'-azobis(2,4-dimethylvaleronitrile).
The amount of the radical polymerization initiator used is preferably 1 part by mass or more and 20 parts by mass or less based on 100 parts by mass of the raw material monomer of the addition polymerization resin segment.
The temperature of the addition polymerization is preferably 110° C. or higher, more preferably 130° C. or higher, and preferably 230° C. or lower, more preferably 220° C. or lower, and further preferably 210° C. or lower.

(Physical Properties of Amorphous Polyester Resin A)
The softening point of the amorphous polyester resin A is preferably 70° C. or higher, more preferably 90° C. or higher, and even more preferably 100° C. or higher, and from the viewpoint of further improving low-temperature fixability, is preferably 150° C. or lower, more preferably 140° C. or lower, and even more preferably 125° C. or lower.
The glass transition temperature of the amorphous polyester resin A is preferably 30° C. or higher, more preferably 35° C. or higher, and even more preferably 40° C. or higher, and from the viewpoint of further improving the low-temperature fixability, is preferably 80° C. or lower, more preferably 70° C. or lower, and even more preferably 60° C. or lower.

The acid value of the amorphous polyester resin A is preferably 5 mgKOH/g or more, more preferably 10 mgKOH/g or more, even more preferably 15 mgKOH/g or more, and is preferably 40 mgKOH/g or less, more preferably 35 mgKOH/g or less, even more preferably 30 mgKOH/g or less.
The softening point, glass transition temperature and acid value of the amorphous polyester resin A can be appropriately adjusted by the types and amounts of raw material monomers used, as well as production conditions such as reaction temperature, reaction time and cooling rate, and these values can be determined by the methods described in the examples.
When two or more kinds of amorphous polyester resins A are used in combination, the softening point, glass transition temperature and acid value of the mixture are preferably within the above-mentioned ranges.

The content of amorphous polyester resin A is preferably 40% by mass or more, more preferably 50% by mass or more, even more preferably 60% by mass or more, even more preferably 65% by mass or more, and is 100% by mass or less, preferably 95% by mass or less, more preferably 90% by mass or less, even more preferably 87% by mass or less, based on the total amount of the resin components in the core portion.

<Crystalline polyester resin C>
In the present invention, the toner base particles preferably contain crystalline polyester resin C, more preferably the toner base particles have a core-shell structure and contain crystalline polyester resin C in the core portion, and further preferably contain crystalline polyester resin C only in the core portion.

The crystalline polyester resin C is, for example, a crystalline polyester resin which is a polycondensation product of an alcohol component and a carboxylic acid component.
The alcohol component is preferably an α,ω-aliphatic diol.
The α,ω-aliphatic diol preferably has 2 or more carbon atoms, more preferably 4 or more, and even more preferably 6 or more carbon atoms, and preferably has 16 or less, more preferably 14 or less, and even more preferably 12 or less carbon atoms.
Examples of α,ω-aliphatic diols include ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 1,11-undecanediol, 1,12-dodecanediol, 1,13-tridecanediol, and 1,14-tetradecanediol. Among these, 1,4-butanediol, 1,6-hexanediol, 1,8-octanediol, 1,10-decanediol, and 1,12-dodecanediol are preferred, and 1,10-decanediol is more preferred.

The amount of α,ω-aliphatic diol in the alcohol component is preferably 80 mol% or more, more preferably 85 mol% or more, even more preferably 90 mol% or more, even more preferably 95 mol% or more, and is 100 mol% or less, even more preferably 100 mol%.

The alcohol component may contain other alcohol components different from the α,ω-aliphatic diol. Examples of other alcohol components include aliphatic diols other than α,ω-aliphatic diols, such as 1,2-propanediol and neopentyl glycol; aromatic diols such as alkylene oxide adducts of bisphenol A; and trihydric or higher alcohols, such as glycerin, pentaerythritol, and trimethylolpropane. These alcohol components may be used alone or in combination.

The carboxylic acid component is preferably an aliphatic dicarboxylic acid, more preferably a straight-chain aliphatic dicarboxylic acid.
The aliphatic dicarboxylic acid preferably has 4 or more carbon atoms, more preferably 8 or more, and even more preferably 10 or more carbon atoms, and preferably has 14 or less, and more preferably 12 or less carbon atoms.
Examples of the aliphatic dicarboxylic acid include fumaric acid, sebacic acid, dodecanedioic acid, and tetradecanedioic acid. Among these, sebacic acid and tetradecanedioic acid are preferred, and sebacic acid is more preferred. These carboxylic acid components may be used alone or in combination.

The amount of aliphatic dicarboxylic acid in the carboxylic acid component is preferably 80 mol% or more, more preferably 85 mol% or more, even more preferably 90 mol% or more, even more preferably 95 mol% or more, and is 100 mol% or less, even more preferably 100 mol%.

The carboxylic acid component may contain other carboxylic acid components different from the aliphatic dicarboxylic acid. Examples of other carboxylic acid components include aromatic dicarboxylic acids such as terephthalic acid and isophthalic acid; and polyvalent carboxylic acids having three or more valences. These carboxylic acid components may be used alone or in combination.

The equivalent ratio of the carboxyl groups of the carboxylic acid component to the hydroxyl groups of the alcohol component [COOH groups/OH groups] is preferably 0.7 or more, more preferably 0.8 or more, and is preferably 1.3 or less, more preferably 1.2 or less.

The crystalline polyester resin C is produced, for example, by a method of polycondensing an alcohol component and a carboxylic acid component.
In the polycondensation, if necessary, an esterification catalyst such as tin(II) di(2-ethylhexanoate), dibutyltin oxide, or titanium diisopropoxybis(triethanolaminate) may be used in an amount of 0.01 part by mass or more and 5 parts by mass or less per 100 parts by mass of the total amount of the alcohol component and the carboxylic acid component; or an esterification promoter such as gallic acid (same as 3,4,5-trihydroxybenzoic acid) may be used in an amount of 0.001 part by mass or more and 0.5 part by mass or less per 100 parts by mass of the total amount of the alcohol component and the carboxylic acid component.
When a monomer having an unsaturated bond such as fumaric acid is used in polycondensation, a radical polymerization inhibitor may be used, if necessary, in an amount of preferably 0.001 part by mass or more and 0.5 part by mass or less per 100 parts by mass of the total amount of the alcohol component and the carboxylic acid component. An example of the radical polymerization inhibitor is 4-tert-butylcatechol.
The temperature of the polycondensation reaction is preferably 120° C. or higher, more preferably 160° C. or higher, and even more preferably 180° C. or higher, and is preferably 250° C. or lower, and more preferably 240° C. or lower. The polycondensation may be carried out in an inert gas atmosphere.

(Physical Properties of Crystalline Polyester Resin C)
The softening point of the crystalline polyester resin C is preferably 60° C. or higher, more preferably 70° C. or higher, and even more preferably 80° C. or higher, from the viewpoint of the storage stability of the toner, and is preferably 150° C. or lower, more preferably 120° C. or lower, more preferably 100° C. or lower, and even more preferably 95° C. or lower, from the viewpoint of further improving the low-temperature fixing ability.
The melting point of the crystalline polyester resin C is preferably 50° C. or higher, more preferably 60° C. or higher, and even more preferably 70° C. or higher, from the viewpoint of the storage stability of the toner, and is preferably 100° C. or lower, more preferably 90° C. or lower, more preferably 85° C. or lower, and even more preferably 80° C. or lower, from the viewpoint of further improving the low-temperature fixing ability.

The acid value of the crystalline polyester resin C is preferably 5 mgKOH/g or more, more preferably 10 mgKOH/g or more, even more preferably 15 mgKOH/g or more, and is preferably 35 mgKOH/g or less, more preferably 25 mgKOH/g or less, even more preferably 20 mgKOH/g or less.

The softening point, melting point, and acid value of the crystalline polyester resin C can be appropriately adjusted by the type and amount of the raw material monomer, as well as the manufacturing conditions such as the reaction temperature, reaction time, and cooling rate, and are determined by the method described in the Examples below. When two or more types of crystalline polyester resin C are used in combination, it is preferable that the softening point, melting point, and acid value obtained as a mixture of these are each within the above ranges.

When amorphous polyester resin A and crystalline polyester resin C are used in combination, the mass ratio of amorphous polyester resin A to crystalline polyester resin C [amorphous polyester resin A/crystalline polyester resin C] is preferably 40/60 or more, more preferably 50/50 or more, even more preferably 60/40 or more, even more preferably 65/35 or more, and is preferably 95/5 or less, more preferably 90/10 or less, even more preferably 85/15 or less, even more preferably 75/25 or less.

[Core-shell structure]
The toner of the present invention preferably has a core-shell structure, and the core portion preferably contains the crystalline polyester resin C and the amorphous polyester resin A. The core portion preferably contains a colorant and a release agent in addition to the crystalline polyester resin C and the amorphous polyester resin A.

In the present invention, from the viewpoint of obtaining a high-definition image, the content of the shell in the toner particles is preferably 3 parts by mass or more, more preferably 5 parts by mass or more, even more preferably 7 parts by mass or more, even more preferably 10 parts by mass or more, and is preferably 30 parts by mass or less, more preferably 25 parts by mass or less, even more preferably 20 parts by mass or less, relative to 100 parts by mass of the toner base particles.
The shell in the toner preferably contains the amorphous polyester resin B described below, and more preferably the shell is made of the amorphous polyester resin B.
From the viewpoint of obtaining a high-definition image, the amount of the shell binder resin in 100 parts by mass of the toner binder resin is 5 parts by mass or more, preferably 7 parts by mass or more, more preferably 10 parts by mass or more, and is 30 parts by mass or less, preferably 25 parts by mass or less, more preferably 20 parts by mass or less.

<Amorphous polyester resin B>
In the present invention, the toner base particles preferably contain, as a binder resin, amorphous polyester resin B in addition to the above-mentioned crystalline polyester resin C and amorphous polyester resin A, and it is more preferable that the shell contains amorphous polyester resin B.
The amorphous polyester resin B is preferably, for example, an amorphous polyester resin containing a polycondensate of an alcohol component and a carboxylic acid component.
Examples of the polyester resin include polyester resin and modified polyester resin. Examples of the modified polyester resin include urethane modified polyester resin, epoxy modified polyester resin, and composite resin containing polyester resin segment and addition polymerization resin segment. Among these, amorphous polyester resin, which is a polycondensation product of alcohol component and carboxylic acid component, is preferable.

The alcohol component may be an alkylene oxide adduct of an aromatic diol, a linear or branched aliphatic diol, an alicyclic diol, or a trihydric or higher polyhydric alcohol, similar to the alcohol component of the polyester resin segment of the amorphous polyester resin A described above. Among these, from the viewpoint of obtaining a toner having excellent low-temperature fixing properties, an alkylene oxide adduct of an aromatic diol is preferred, an alkylene oxide adduct of bisphenol A is more preferred, and a propylene oxide adduct of bisphenol A [2,2-bis(4-hydroxyphenyl)propane] or an ethylene oxide adduct of bisphenol A is even more preferred. These may be used alone or in combination. Among these, an ethylene oxide adduct of bisphenol A is more preferred.

Examples of the carboxylic acid component include the same dicarboxylic acids and trivalent or higher polyvalent carboxylic acids as the carboxylic acid component of the polyester resin segment of the amorphous polyester resin A described above.
Examples of the dicarboxylic acid include aromatic dicarboxylic acids, linear or branched aliphatic dicarboxylic acids, and alicyclic dicarboxylic acids. Among these, at least one selected from aromatic dicarboxylic acids and linear or branched aliphatic dicarboxylic acids is preferred.
The amount of aromatic dicarboxylic acid in the carboxylic acid component is preferably 40 mol% or more, more preferably 50 mol% or more, even more preferably 60 mol% or more, even more preferably 70 mol% or more, and is preferably 95 mol% or less, more preferably 90 mol% or less, even more preferably 85 mol% or less.

The amount of linear or branched aliphatic dicarboxylic acid in the carboxylic acid component is preferably 1 mol% or more, more preferably 3 mol% or more, even more preferably 5 mol% or more, and preferably 60 mol% or less, more preferably 30 mol% or less, even more preferably 20 mol% or less, even more preferably 15 mol% or less.

When a trivalent or higher polycarboxylic acid is contained, the amount of the trivalent or higher polycarboxylic acid in the carboxylic acid component is preferably 3 mol % or more, more preferably 5 mol % or more, even more preferably 8 mol % or more, and is preferably 30 mol % or less, more preferably 25 mol % or less, even more preferably 20 mol % or less.
These carboxylic acid components may be used alone or in combination of two or more.

The equivalent ratio of the carboxyl groups of the carboxylic acid component to the hydroxyl groups of the alcohol component [COOH groups/OH groups] is preferably 0.7 or more, more preferably 0.8 or more, and is preferably 1.3 or less, more preferably 1.2 or less.

The polyester resin B may be produced, for example, by a step A in which an alcohol component and a carboxylic acid component are polycondensed.
Step A is the same as step A described in the method for producing amorphous polyester resin A, and the preferred ranges are also the same.

(Physical Properties of Amorphous Polyester Resin B)
The softening point of the amorphous polyester resin B is preferably 70° C. or higher, more preferably 90° C. or higher, and even more preferably 100° C. or higher, and from the viewpoint of further improving the low-temperature fixability, it is preferably 150° C. or lower, more preferably 140° C. or lower, and even more preferably 125° C. or lower.
The glass transition temperature of the amorphous polyester resin B is preferably 30° C. or higher, more preferably 40° C. or higher, and even more preferably 50° C. or higher, and from the viewpoint of further improving the low-temperature fixability, is preferably 90° C. or lower, more preferably 80° C. or lower, and even more preferably 70° C. or lower.

The acid value of the amorphous polyester resin B is preferably 5 mgKOH/g or more, more preferably 10 mgKOH/g or more, even more preferably 15 mgKOH/g or more, and is preferably 40 mgKOH/g or less, more preferably 30 mgKOH/g or less, even more preferably 25 mgKOH/g or less.
The softening point, glass transition temperature and acid value of the amorphous polyester resin B can be appropriately adjusted by the types and amounts of raw material monomers used, as well as production conditions such as reaction temperature, reaction time and cooling rate, and these values can be determined by the methods described in the examples.
When two or more kinds of amorphous polyester resins B are used in combination, the softening point, glass transition temperature and acid value of the mixture are preferably within the above-mentioned ranges.

The content of the amorphous polyester resin B is preferably 60% by mass or more, more preferably 80% by mass or more, even more preferably 90% by mass or more, even more preferably 95% by mass or more, and is 100% by mass or less, even more preferably 100% by mass, based on the total amount of the resin components of the resin particles Y for the shell layer.

[Coloring Agent]
In the present invention, the toner base particles preferably contain a colorant, and the core portion preferably contains the colorant.
As the colorant, any of the dyes, pigments, etc. used as toner colorants can be used.
Examples of colorants include carbon black, phthalocyanine blue (e.g., pigment blue 15:3), permanent brown FG, brilliant fast scarlet, pigment green B, rhodamine B base, solvent red 49, solvent red 146, solvent blue 35, quinacridone, carmine 6B, and disazo yellow. The toner may be either a black toner or a color toner other than black.
The content of the colorant in the toner particles is preferably 1% by mass or more, more preferably 3% by mass or more, even more preferably 5% by mass or more, and is preferably 25% by mass or less, more preferably 20% by mass or less, even more preferably 15% by mass or less.

[Release Agent]
In the present invention, the toner base particles preferably contain a release agent, and more preferably contain a release agent in the core portion.
Examples of the release agent include polypropylene wax, polyethylene wax, polypropylene-polyethylene copolymer wax, hydrocarbon waxes such as microcrystalline wax, paraffin wax, Fischer-Tropsch wax, and Sasol wax, or oxides thereof, ester waxes such as carnauba wax, montan wax, or deacidified waxes thereof, and fatty acid ester wax, fatty acid amides, fatty acids, higher alcohols, and fatty acid metal salts. These may be used alone or in combination of two or more.

The melting point of the release agent is preferably 60° C. or higher, more preferably 70° C. or higher, and preferably 160° C. or lower, more preferably 140° C. or lower, even more preferably 120° C. or lower, and even more preferably 100° C. or lower.
The content of the release agent in the toner particles is preferably 0.1% by mass or more, more preferably 1% by mass or more, even more preferably 3% by mass or more, and even more preferably 5% by mass or more, and is preferably 20% by mass or less, more preferably 15% by mass or less.

<Method of Manufacturing Toner Base Particles>
The method for producing the toner base particles is not particularly limited as long as the toner base particles have a desired circularity. From the viewpoint of obtaining a desired circularity of 0.965 or more, it is preferable to adopt a chemical method such as an emulsion polymerization method or a suspension method. Furthermore, from the viewpoint of obtaining a toner having excellent toner physical properties such as low-temperature fixing property, it is preferable to obtain the toner base particles by emulsion aggregation having the following steps 1 to 3.
Step 1: A step of aggregating resin particles X, which contain a crystalline polyester resin C and an amorphous polyester resin A in the same or different particles, in an aqueous medium to obtain aggregated particles 1;
Step 2: A step of aggregating resin particles Y containing a non-crystalline polyester-based resin B to the aggregated particles 1 obtained in step 1 to obtain aggregated particles 2;
Step 3: A step of heating the aggregated particles 2 obtained in step 2 to fuse them to obtain fused particles. As a method for producing toner base particles by steps 1 to 3, for example, steps 1, 1', and 2 described in JP-A-2021-012242 and steps 1, 1', and 2 described in JP-A-2021-026129 can be referenced.

In the above step 1, it is preferable to aggregate colorant particles containing a colorant and release agent particles containing a release agent together with the resin particles X.
The dispersion of the resin particles X is preferably obtained by a phase inversion emulsification method.
In addition, the colorant particles are preferably mixed with resin particles as a dispersion of the colorant particles, and then aggregated to be contained in the aggregated particles, and the colorant and the aqueous medium are preferably dispersed using a dispersing machine such as a homogenizer or an ultrasonic dispersing machine. From the viewpoint of improving the dispersion stability of the colorant, the dispersion is preferably carried out in the presence of an addition polymer (hereinafter, the addition polymer used for dispersing the colorant is also referred to as "addition polymer E") or a surfactant.
Examples of the surfactant include a nonionic surfactant, an anionic surfactant, and a cationic surfactant.
The addition polymer E preferably has a constituent unit derived from an addition polymerizable monomer a having an aromatic group, and further preferably contains at least one selected from an addition polymerizable monomer b having an ionic group, an addition polymerizable monomer c having a polyalkylene oxide group, and a macromonomer d. For the colorant particle dispersion and the addition polymer E, reference is made to the addition polymer E described in JP-A-2021-026129.
Furthermore, it is preferable that the release agent particles are mixed with the resin particle dispersion and the colorant particle dispersion as a dispersion liquid of the release agent particles, and then aggregated, so that the release agent particles are contained in the aggregated particles.
The dispersion of release agent particles can be obtained using a surfactant, but is preferably obtained by mixing the release agent with resin particles Z. By preparing the release agent particles using the release agent and resin particles Z, the release agent particles are stabilized by the resin particles Z, and it becomes possible to disperse the release agent in an aqueous medium without using a surfactant. It is considered that the dispersion of release agent particles has a structure in which a large number of resin particles Z are attached to the surfaces of the release agent particles.
The resin constituting the resin particles Z in which the release agent is dispersed is preferably a polyester resin, and it is more preferable to use a composite resin D having a polyester resin segment and an addition polymerization resin segment. For the release agent particle dispersion and the composite resin D, reference is made to JP 2021-026129 A.
In addition, a post-treatment step may be performed after the above step 3, and it is preferable to obtain toner base particles by isolation. Since the particles obtained in step 3 are present in an aqueous medium, it is preferable to first perform solid-liquid separation, and then wash and dry them as necessary.

[Volume Average Particle Size of Toner Base Particles]
It is preferable to add an external additive, which will be described later, to the surface of the toner base particles obtained by drying or the like, and use the resulting toner as a toner for developing electrostatic images.
The volume median particle size ( _D50 ) of the toner base particles is preferably 2 μm or more, more preferably 3 μm or more, even more preferably 4 μm or more, and is preferably 10 μm or less, more preferably 8 μm or less, even more preferably 6 μm or less, from the viewpoints of improving the productivity of the toner, obtaining a desired circularity, and improving the low-temperature fixing ability of the toner.
The CV value of the toner base particles is preferably 12% or more, more preferably 14% or more, and even more preferably 16% or more, from the viewpoint of improving the productivity of the toner, and is preferably 32% or less, more preferably 30% or less, and even more preferably 29% or less, from the viewpoint of obtaining high-quality images.

<External Additives>
In the present invention, the toner for developing electrostatic images is composed of toner base particles having a circularity of 0.965 or more, small silica particles having a particle size calculated from the specific surface area of 10 nm to 30 nm, and large silica particles having a particle size calculated from the specific surface area of 70 nm to 190 nm. The mass ratio of the amount of the large silica particles to the amount of the small silica particles (large silica particles/small silica particles) is 7 to 18.
When the mass ratio is 7 or more, the surface unevenness of the toner is appropriate, friction with the developing blade is appropriately generated, and the toner is uniformly charged, so that the occurrence of fogging is suppressed. Also, friction with the developing roller is appropriately generated, and the necessary amount of toner is obtained, so that good image density is obtained. Also, when the mass ratio is 18 or less, friction between the developing roller and the toner for developing electrostatic images is not excessively large, and the amount of toner to be conveyed does not increase too much, so that the amount of toner scraped off by the developing blade is within an appropriate range, and the occurrence of toner leakage from the end of the developing roller is suppressed.
The mass ratio of the amount of the large silica particles to the small silica particles added (large silica particles/small silica particles) is 7 or more, preferably 8 or more, more preferably 9 or more, even more preferably 10 or more, and is 18 or less, preferably 16 or less, more preferably 15 or less, even more preferably 14 or less.

The amount of small-diameter silica particles added relative to 100 parts by mass of the toner base particles is, from the viewpoints of improving transferability, suppressing the occurrence of fogging, and further improving the stability of image density, preferably 0.4 parts by mass or more, more preferably 0.45 parts by mass or more, and preferably 1.2 parts by mass or less, more preferably 1.0 part by mass or less, even more preferably 0.7 parts by mass or less, still more preferably 0.65 parts by mass or less, and even more preferably 0.6 parts by mass or less.
From the same viewpoint, the amount of large-diameter silica particles added per 100 parts by mass of the toner base particles is preferably 5 parts by mass or more, more preferably 6 parts by mass or more, and is preferably 18 parts by mass or less, more preferably 14 parts by mass or less, and even more preferably 10 parts by mass or less.
From the same viewpoint, the total amount of the large-diameter silica particles and the small-diameter silica particles added relative to 100 parts by mass of the toner base particles is preferably 5.5 parts by mass or more, more preferably 6 parts by mass or more, even more preferably 6.5 parts by mass or more, and is preferably 19 parts by mass or less, more preferably 15 parts by mass or less, even more preferably 12 parts by mass or less.

The small particle size silica particles have a particle size calculated from the specific surface area of 10 nm or more, preferably 12 nm or more, more preferably 14 nm or more, even more preferably 16 nm or more, and still more preferably 20 nm or more, and are 30 nm or less, preferably 28 nm or less.
In addition, the large-diameter silica particles have a particle size calculated from the specific surface area of 70 nm or more, preferably 90 nm or more, more preferably 100 nm or more, and 190 nm or less, preferably 150 nm or less, more preferably 140 nm or less, and even more preferably 125 nm or less.
The "particle size calculated from the specific surface area" of the small-particle size silica particles and the large-particle size silica particles is measured by the method described in the Examples.

A toner to which the above-mentioned small-diameter silica particles and large-diameter silica particles are externally added has two peaks in particle diameters of 10 nm or more and 30 nm or less, and a peak in particle diameters of 70 nm or more and 190 nm or less, when the particle diameter is plotted on the horizontal axis and the mass of particles having the same particle diameter on the vertical axis, for the entire external additive.
In addition, when the mass ratio of particles in the external additive having a particle size of 10 nm or more and 70 nm or less, calculated from the specific surface area, is W _S , and the mass ratio of particles having a particle size of more than 70 nm and 400 nm or less, calculated from the specific surface area, is W _L , W _L /W _S is preferably 7 or more, more preferably 8 or more, even more preferably 9 or more, still more preferably 10 or more, and preferably 18 or less, more preferably 16 or less, even more preferably 15 or less, and still more preferably 14 or less.

From the viewpoint of improving the toner transferability, the small particle size silica particles and the large particle size silica particles are preferably hydrophobic silica that has been subjected to a hydrophobic treatment.
Examples of hydrophobizing agents that make the surfaces of silica particles hydrophobic include silane coupling agents and silicone oils.
Examples of silane coupling agents include disilazanes such as hexamethyldisilazane (HMDS); cyclic silazanes; trimethylsilane; trimethylchlorosilane; dimethyldichlorosilane, methyltrichlorosilane, allyldimethylchlorosilane, benzyldimethylchlorosilane, methyltrimethoxysilane, methyltriethoxysilane, isobutyltrimethoxysilane, dimethyldimethoxysilane, dimethyldiethoxysilane, trimethylmethoxysilane, octyltriethoxysilane, hydroxypropyltrimethoxysilane, phenyltrimethoxysilane, n-octadecyltrimethoxysilane, vinyltrimethoxysilane, alkylsilane compounds such as dimethylsilane, vinyltriethoxysilane, γ-methacryloxypropyltrimethoxysilane, and vinyltriacetoxysilane; and aminosilane compounds such as γ-aminopropyltriethoxysilane, γ-(2-aminoethyl)aminopropyltrimethoxysilane, γ-(2-aminoethyl)aminopropylmethyldimethoxysilane, N-phenyl-3-aminopropyltrimethoxysilane, N-(2-aminoethyl)3-aminopropyltrimethoxysilane, and N-β-(N-vinylbenzylaminoethyl)-γ-aminopropyltrimethoxysilane.
Examples of the silicone oil include polydimethylsiloxane, polymethylhydrogensiloxane, polymethylphenylsiloxane, and amino-modified silicone oil.
Of these, hexamethyldisilazane (HMDS), dimethyldichlorosilane (DMDS), polydimethylsiloxane, octyltriethoxysilane (OTES), and polydimethylsiloxane are preferred.
These may be used alone or in combination of two or more.

A mixer such as a Henschel mixer can be used to mix the toner base particles and external additives.

In addition to the small and large silica particles, charged particles (charging assistant) may be added to the toner base particles.
It is preferable to externally add charged particles having a charging polarity different from the charging polarity of the toner base particles. When the toner base particles are positively charged, it is preferable to externally add negatively charged particles, and when the toner base particles are negatively charged, it is preferable to externally add positively charged particles.
Here, when the toner base particles are those having the above-mentioned polyester resin as a binder resin, since the toner base particles are negatively charged, it is preferable to externally add positively charged particles.
The number average primary particle diameter of the charged particles is preferably 0.10 μm or more and 1.50 μm or less, and more preferably 0.150 μm or more and 1.00 μm or less.
The use of such charged particles is preferable because it provides good transfer efficiency through continuous use, and it is believed that the reason for this is that the charged particles of this size are capable of rolling on the toner particle surface, promoting toner charging and, as a result, suppressing the decrease in charge caused by the application of a transfer bias.

Examples of positively charged particles include hydrotalcite particles, titanium oxide particles, benzoguanamine resin particles, benzoguanamine-melamine resin particles, melamine resin particles, melamine-formaldehyde resin particles, etc. Among these, melamine-formaldehyde resin particles are particularly preferred.
Examples of negatively charged particles include polytetrafluoroethylene particles, trifluoroethylene particles, vinylidene fluoride particles, and fluoroethylene resin particles.

The amount of charged particles added per 100 parts by weight of toner base particles is preferably 0.005 parts by weight or more, more preferably 0.01 parts by weight or more, even more preferably 0.03 parts by weight or more, and is preferably 1.0 part by weight or less, more preferably 0.3 parts by weight or less, even more preferably 0.1 part by weight or less.

<Toner for developing electrostatic images>
The toner for developing electrostatic images obtained as described above can be used as a one-component developer, or mixed with a carrier to form a two-component developer. Among these, the toner is suitable as a one-component developer, and more suitable as a non-magnetic one-component developer.

The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples. Each property value was measured and evaluated by the following methods.
In the notation "alkylene oxide (X)", the number X in parentheses means the average number of moles of alkylene oxide added.

[measurement]
[Acid value of resin]
Measurement was performed in accordance with JIS K0070:1992, except that the measurement solvent was chloroform.

[Resin softening point, crystallinity index, melting point, glass transition temperature]
(1) Softening point Using a flow tester "CFT-500D" (manufactured by Shimadzu Corporation), 1 g of a sample was extruded from a nozzle having a diameter of 1 mm and a length of 1 mm under a load of 1.96 MPa applied by a plunger while heating the sample at a temperature increase rate of 6°C/min. The plunger descent amount of the flow tester was plotted against the temperature, and the temperature at which half of the sample flowed out was taken as the softening point.

(2) Crystallinity Index Using a differential scanning calorimeter "Q100" (manufactured by TA Instruments Japan Co., Ltd.), 0.02 g of a sample was weighed into an aluminum pan and cooled to 0°C at a temperature drop rate of 10°C/min. The sample was then left to stand for 1 minute, and then heated to 180°C at a temperature increase rate of 10°C/min to measure the amount of heat. The temperature of the peak with the largest peak area among the observed endothermic peaks was defined as the endothermic maximum peak temperature (1), and the crystallinity index was calculated by (softening point (°C))/(endothermic maximum peak temperature (1) (°C)).

(3) Melting point and glass transition temperature Using a differential scanning calorimeter "Q100" (manufactured by TA Instruments Japan Co., Ltd.), 0.02 g of a sample was weighed into an aluminum pan, heated to 200°C, and cooled from that temperature to 0°C at a rate of 10°C/min. The sample was then heated at a rate of 10°C/min, and the amount of heat was measured. Among the endothermic peaks observed, the temperature of the peak with the largest peak area was taken as the maximum endothermic peak temperature (2). In the case of a crystalline resin, this peak temperature was taken as the melting point.
In the case of an amorphous resin, when a peak was observed, the temperature of the peak was taken as the glass transition temperature. When no peak was observed but a step was observed, the temperature at the intersection of the tangent showing the maximum slope of the curve at the step and an extension of the baseline on the low temperature side of the step was taken as the glass transition temperature.

[Weight average molecular weight of addition polymer]
The measurement was performed by gel permeation chromatography (GPC apparatus "HLC-8320GPC" (manufactured by Tosoh Corporation), columns "TSKgel SuperAWM-H", "TSKgel SuperAW3000", "TSKgel guardcolumn Super AW-H" (manufactured by Tosoh Corporation), flow rate: 0.5 mL/min) using a solution of phosphoric acid and lithium bromide dissolved in N,N-dimethylformamide to concentrations of 60 mmol/L and 50 mmol/L, respectively, as an eluent, and using a monodisperse polystyrene kit with known molecular weights (PStQuick B (F-550, F-80, F-10, F-1, A-1000), PStQuick C (F-288, F-40, F-4, A-5000, A-500), manufactured by Tosoh Corporation) as a standard substance.

[Melting point of release agent]
Using a differential scanning calorimeter "Q100" (manufactured by TA Instruments Japan Co., Ltd.), 0.02 g of a sample was weighed into an aluminum pan, heated to 200°C, and cooled from that temperature at a rate of 10°C/min to 0°C. The sample was then heated at a rate of 10°C/min, the amount of heat was measured, and the maximum endothermic peak temperature was taken as the melting point.

[Volume Median Particle Size _D50 and CV Value of Resin Particles, Release Agent Particles, and Colorant Particles]
(1) Measuring device: Laser diffraction type particle size measuring instrument "LA-920" (manufactured by Horiba, Ltd.)
(2) Measurement conditions: Distilled water was added to the measurement cell, and the volume median particle size _D50 and the volume average particle size were measured at a concentration that brought the absorbance into an appropriate range. The CV value (coefficient of variation of particle size distribution, %) was calculated according to the following formula.
CV value (%) = (standard deviation of particle size distribution/volume average particle size) x 100

[Solid Content Concentration of Resin Particle Dispersion, Release Agent Particle Dispersion, and Colorant Particle Dispersion]
Using an infrared moisture meter "FD-230" (Kett Electric Laboratory Co., Ltd.), the moisture (mass%) of 5 g of the measurement sample was measured at a drying temperature of 150°C and measurement mode 96 (monitoring time 2.5 min/fluctuation range 0.05%). The solid content concentration was calculated according to the following formula.
Solid content concentration (mass%) = 100 - water (mass%)

[Volume Median Particle Size _D50 and CV Value of Agglomerated Particles]
The volume median particle diameter _D50 of the agglomerated particles was measured as follows.
・Measuring instrument: "Coulter Multisizer (registered trademark) III" (manufactured by Beckman Coulter, Inc.)
Aperture diameter: 50 μm
Analysis software: "Multisizer (registered trademark) III version 3.51" (Beckman Coulter, Inc.)
・Electrolyte: "Isoton (registered trademark) II" (Beckman Coulter, Inc.)
Measurement conditions: The sample dispersion was added to 100 mL of the electrolyte to adjust the concentration so that the particle size of 30,000 particles could be measured in 20 seconds, and then the 30,000 particles were measured, and the volume median particle size _D50 and the volume average particle size were calculated from the particle size distribution. The CV value (coefficient of variation of particle size distribution, %) was calculated according to the following formula.
CV value (%) = (standard deviation of particle size distribution/volume average particle size) x 100

[Circularity of Fused Particles and Toner Base Particles]
The circularity of the fused particles and the toner base particles was measured under the following conditions.
・Measuring device: Flow type particle image analyzer "FPIA-3000" (manufactured by Sysmex Corporation)
Preparation of dispersion: A dispersion of fused particles or toner base particles was prepared by diluting with deionized water so that the solid content concentration was 0.001 to 0.05% by mass.
Measurement mode: HPF measurement mode

[Volume Median Particle Size _D50 and CV Value of Toner Particles]
The volume median particle diameter _D50 of the toner particles was measured as follows.
The measuring device, aperture diameter, analysis software, and electrolyte used were the same as those used to measure the volume median particle diameter D ₅₀ of the agglomerated particles.
Dispersion: Polyoxyethylene lauryl ether "EMULGEN (registered trademark) 109P" (manufactured by Kao Corporation, HLB: 13.6) was dissolved in the electrolytic solution to obtain a dispersion having a concentration of 5% by mass.
Dispersion conditions: 10 mg of a toner measurement sample was added to 5 mL of the dispersion liquid, and dispersed for 1 minute using an ultrasonic disperser. Thereafter, 25 mL of electrolyte was added, and the mixture was further dispersed for 1 minute using an ultrasonic disperser to prepare a sample dispersion liquid.
Measurement conditions: The sample dispersion was added to 100 mL of the electrolyte to adjust the concentration to a level that would allow the particle sizes of 30,000 particles to be measured in 20 seconds. The 30,000 particles were then measured, and the volume median particle size _D50 and volume average particle size were determined from the particle size distribution.
The CV value (coefficient of variation of particle size distribution, %) was calculated according to the following formula.
CV value (%) = (standard deviation of particle size distribution/volume average particle size) x 100

[Particle size of external additive]
The particle diameter of the external additive was calculated from the specific surface area according to the following formula, assuming that the particle shape of the external additive was a perfect sphere and that the density of the silica particles as the external additive was 2.2 g/cm ² .
Particle size (m) = 6/(specific surface area (m ² /g) x density (g/m ³ ))
The specific surface area (m ² /g) used in the above formula was obtained using a BET multipoint method with a specific surface area measuring device. In the BET multipoint method, the adsorption amount was measured at three or more points within the equilibrium relative pressure range of the adsorbed gas (nitrogen) of 0.05 to 0.30, and the specific surface area was calculated. Specifically, the analysis was performed under the following measurement conditions.
・Measuring instrument: Multi-sample high-performance specific surface area/pore distribution measuring instrument 3Flex-3MP (manufactured by Micromeritics)
Dispersed adsorbent: Nitrogen Pretreatment: 40°C, 4 hours or more Equilibrium relative pressure: 0.05 to 0.30 (in 0.05 increments)
Equilibrium interval: 10 seconds

[Evaluation method]
[Fog test conditions]
The toner was loaded into a commercially available printer "COREFIDO C712dnw" (manufactured by Oki Data Corporation), and 2,000 sheets of images with a print density of 0.3% were printed continuously on high-quality paper "Excellent White Paper A4 Size" (manufactured by Oki Data Corporation) under an environment with a temperature of 25°C and a humidity of 50% (NN environment), and then the printer was left to stand for 12 hours under an environment with a temperature of 27°C and a humidity of 80% (HH environment), and another 1,000 sheets were printed continuously under the HH environment, resulting in a total of 3,000 sheets printed under the NN and HH environments. Fog was measured when the first sheet was printed, and then every 500 sheets. Measurements were also performed on the first sheet when the environment was changed from the NN environment to the HH environment.

[Measurement of Fog]
Fog was measured as follows.
First, blank printing was performed, and the printer was stopped during the blank printing. The developing unit was removed from the printer, and "Scotch (registered trademark) Mending Tape 810" (manufactured by 3M Japan Ltd., width: 18 mm) was attached to the photoconductor, and the toner on the photoconductor was peeled off with the tape.
The tape peeled off from the photoreceptor and the unused tape were attached to high-quality paper "Excellent White Paper A4 size" (manufactured by Oki Data Corporation), and the tape peeled off from the photoreceptor and the unused tape were each measured using a colorimeter "SpectroEye" (manufactured by GretagMacbeth, light irradiation conditions: standard light source D50, observation field of view 2°, density standard DINNB, absolute white standard). The color difference (ΔE) between the tape peeled off from the photoreceptor and the unused tape was taken as fog. The smaller the fog value, the better the image without fog. The results are shown in Table 5. The fog value was the average value of the measured value when the number of printed sheets was the first sheet, the measured values every 500 sheets until the total number of sheets reached 3,000 sheets under the NN environment and the HH environment, and the measured value of the first sheet when the NN environment was changed to the HH environment.

[Conveyance amount test conditions]
The toner was loaded into a commercially available printer "COREFIDO C712dnw" (manufactured by Oki Data Corporation), and 2,000 sheets of images with a print density of 0.3% were printed continuously on high-quality paper "Excellent White Paper A4 Size" (manufactured by Oki Data Corporation) in an environment with a temperature of 25°C and a humidity of 50% (NN environment), and then the printer was left to stand for 12 hours in an environment with a temperature of 27°C and a humidity of 80% (HH environment), and another 1,000 sheets were printed continuously in the HH environment, resulting in a total of 3,000 sheets printed in the NN and HH environments. The conveying amount was measured every 1,000 sheets after the first sheet was printed. The conveying amount was also measured for the first sheet when the environment was changed from the NN environment to the HH environment.

[Measurement of conveyance amount]
First, a solid image was printed, and the printer was stopped when the image was transferred to half of the A4 size. A 1 cm x 2 cm jig was attached to each of three locations on the developing roller, 3 cm from both ends and the central part of the developing roller, and the toner on the developing roller was sucked up using a Q/m meter "210HS" (manufactured by Trek). The amount of toner per unit area on the developing roller was calculated by dividing the amount of sucked toner by the area of the developer, and this was used as the transport amount. As for the value of the transport amount, if it is 0.20 mg/cm2 or ^more , the image density after printing can be guaranteed, and in addition, if it is 0.30 mg/cm2 or ^more , toner leakage occurs from the end of the developing unit, so a transport amount less than this is desirable. In addition, it is desirable that the transport amount is stable regardless of the number of printed sheets and the printing environment. The results are shown in Table 5. The transport amount was the average of the measured value when the first sheet was printed, the measured value every 1,000 sheets until a total of 3,000 sheets was printed under the NN and HH environments, and the measured value for the first sheet when the environment was changed from the NN environment to the HH environment. The standard deviation is also shown in Table 5 to determine whether the transport amount is stable.

[Production of resin]
[Production of amorphous resin]
Production Example A1 (Production of Resin A-1)
The inside of a 10L four-neck flask equipped with a nitrogen inlet tube, a dehydration tube, a stirrer, and a thermocouple was replaced with nitrogen, and 3356g of propylene oxide (2.2) adduct of bisphenol A, 955g of terephthalic acid, 385g of Paracol 6490 (manufactured by Nippon Seiro), 25g of tin (II) di(2-ethylhexanoate), and 2.5g of 3,4,5-trihydroxybenzoic acid were added, and the mixture was heated to 235°C under a nitrogen atmosphere while stirring, and then held at 235°C for 5 hours, after which the pressure in the flask was reduced and held at 8kPa for 1 hour. After that, the mixture was returned to atmospheric pressure, cooled to 160°C, and a mixture of 2198g of styrene, 550g of stearyl methacrylate, 110g of acrylic acid, and 330g of dibutyl peroxide was added dropwise over 1 hour while the mixture was held at 160°C. After that, the mixture was kept at 160°C for 30 minutes, and then heated to 200°C. The pressure in the flask was further reduced and kept at 8 kPa for 1 hour. After that, the pressure was returned to atmospheric pressure, and the mixture was cooled to 190°C. 200g of fumaric acid, 194g of sebacic acid, 184g of trimellitic anhydride, and 2.5g of 4-tert-butylcatechol were added, and the mixture was heated to 210°C at 10°C/hr. Then, the mixture was reacted at 4 kPa until the desired softening point was obtained, to obtain Resin A-1. The physical properties are shown in Table 1.

Production Example A2 (Production of Resin B-1)
The inside of a four-neck flask equipped with a nitrogen inlet tube, a dehydration tube, a stirrer, and a thermocouple was replaced with nitrogen, and 3265 g of ethylene oxide (2.2) adduct of bisphenol A, 1334 g of terephthalic acid, 25 g of tin (II) di(2-ethylhexanoate), and 2.5 g of 3,4,5-trihydroxybenzoic acid were added, and the temperature was raised to 235°C while stirring under a nitrogen atmosphere, and after maintaining at 235°C for 6 hours, the pressure in the flask was further reduced and maintained at 8.3 kPa for 1 hour. After that, the pressure was returned to atmospheric pressure, and the flask was cooled to 180°C, and 73 g of adipic acid, 135 g of dodecenylsuccinic anhydride, and 193 g of trimellitic anhydride were added, and the temperature was raised to 220°C at 10°C/hr, and then the pressure in the flask was reduced and the reaction was carried out at 10 kPa until the desired softening point, and resin B-1 was obtained. The physical properties are shown in Table 1.

Production Example A3 (Production of Resin A-2)
The inside of a four-neck flask equipped with a nitrogen inlet tube, a dehydration tube, a stirrer, and a thermocouple was replaced with nitrogen, and 3558 g of a propylene oxide (2.2) adduct of bisphenol A, 1416 g of an ethylene oxide (2.2) adduct of bisphenol A, 1229 g of terephthalic acid, 1518 g of dodecenylsuccinic anhydride, and 40 g of di(2-ethylhexanoate)tin (II) were added, and the mixture was heated to 230°C under a nitrogen atmosphere while stirring, and then held at 230°C for 6 hours, after which the pressure in the flask was further reduced and held at 8.3 kPa for 1 hour. Thereafter, the mixture was cooled to 215°C and returned to atmospheric pressure, after which 279 g of trimellitic anhydride was added, and held at 215°C for 1 hour, and then the pressure in the flask was further reduced and held at 8.3 kPa for 3 hours to obtain resin A-2. The physical properties are shown in Table 1.

Production Example A4 (Production of Resin D-1)
Resin D-1 was obtained in the same manner as in Production Example A1, except that the raw material composition was changed as shown in Table 1. The physical properties are shown in Table 1.

[Production of crystalline polyester resin]
Production Example C1 (Production of Resin C-1)
The inside of a 10 L four-neck flask equipped with a nitrogen inlet tube, a dehydration tube, a stirrer, and a thermocouple was replaced with nitrogen, 3416 g of 1,10-decanediol and 4084 g of sebacic acid were added, and the temperature was raised to 135° C. with stirring, and the mixture was maintained at 135° C. for 3 hours, and then the temperature was raised from 135° C. to 200° C. over 10 hours. Then, 23 g of tin(II) di(2-ethylhexanoate) was added, and the mixture was further maintained at 200° C. for 1 hour, after which the pressure in the flask was reduced and the mixture was maintained under a reduced pressure of 8.3 kPa for 1 hour to obtain Resin C-1. The physical properties are shown in Table 2.

[Production of Resin Particle Dispersion]
Production Example X1 (Production of Resin Particle Dispersion X-1)
210 g of Resin A-1, 90 g of Resin C-1, and 360 g of methyl ethyl ketone were placed in a 3 L vessel equipped with a stirrer, a reflux condenser, a dropping funnel, a thermometer, and a nitrogen inlet tube, and the resins were dissolved over 2 hours at 73° C. A 5% by mass aqueous solution of sodium hydroxide was added to the resulting solution so that the degree of neutralization with respect to the acid value of the resin was 60 mol%, and the mixture was stirred for 30 minutes.
Next, while maintaining the temperature at 73°C, 600 g of deionized water was added over 60 minutes while stirring at 280 r/min (circumferential speed 88 m/min) to cause phase inversion emulsification. While continuing to maintain the temperature at 73°C, methyl ethyl ketone was distilled off under reduced pressure to obtain an aqueous dispersion. Thereafter, the aqueous dispersion was cooled to 30°C while stirring at 280 r/min (circumferential speed 88 m/min), and deionized water was added so that the solid content concentration became 20 mass%, thereby obtaining a resin particle dispersion X-1. The volume median particle diameter _D50 and CV value of the obtained resin particles are shown in Table 3.

Production Example X2 (Production of Resin Particle Dispersion X-2)
300 g of Resin A-2, 360 g of methyl ethyl ketone, and 59 g of deionized water were placed in a 3 L vessel equipped with a stirrer, a reflux condenser, a dropping funnel, a thermometer, and a nitrogen inlet tube, and the resin was dissolved over 2 hours at 73° C. A 5% by mass aqueous solution of sodium hydroxide was added to the resulting solution so that the degree of neutralization with respect to the acid value of the resin was 60 mol%, and the mixture was stirred for 30 minutes.
Next, while maintaining the temperature at 73°C, 600 g of deionized water was added over 60 minutes while stirring at 280 r/min (circumferential speed 88 m/min) to cause phase inversion emulsification. While continuing to maintain the temperature at 73°C, methyl ethyl ketone was distilled off under reduced pressure to obtain an aqueous dispersion. Thereafter, while continuing to stir at 280 r/min (circumferential speed 63 m/min), the aqueous dispersion was cooled to 30°C, and deionized water was added so that the solid content concentration was 20 mass%, thereby obtaining a resin particle dispersion X-2. The volume median particle diameter _D50 and CV value of the obtained resin particles are shown in Table 3.

Production Example Y1 (Production of Resin Particle Dispersion Y-1)
300 g of Resin B-1 and 360 g of methyl ethyl ketone were placed in a 3 L vessel equipped with a stirrer, a reflux condenser, a dropping funnel, a thermometer, and a nitrogen inlet tube, and the resin was dissolved over 2 hours at 40° C. A 5% by mass aqueous solution of sodium hydroxide was added to the resulting solution so that the degree of neutralization with respect to the acid value of the resin was 60 mol%, and the mixture was stirred for 30 minutes.
Next, while maintaining the temperature at 40°C, 600 g of deionized water was added over 60 minutes while stirring at 280 r/min (circumferential speed 88 m/min), and phase inversion emulsification was performed. The temperature was raised to 73°C, and methyl ethyl ketone was distilled off under reduced pressure to obtain an aqueous dispersion. Thereafter, the aqueous dispersion was cooled to 30°C while stirring at 280 r/min (circumferential speed 88 m/min), and deionized water was added so that the solid content concentration became 20 mass%, thereby obtaining a resin particle dispersion Y-1. The volume median particle diameter _D50 and CV value of the obtained resin particles are shown in Table 3.

Production Example Z1 (Production of Resin Particle Dispersion Z-1)
200 g of Resin D-1 and 200 g of methyl ethyl ketone were placed in a 3 L vessel equipped with a stirrer, a reflux condenser, a dropping funnel, a thermometer, and a nitrogen inlet tube, and the resin was dissolved over 2 hours at 73° C. A 5% by mass aqueous solution of sodium hydroxide was added to the resulting solution so that the degree of neutralization with respect to the acid value of Resin D-1 was 60 mol %, and the mixture was stirred for 30 minutes.
Next, while maintaining the temperature at 73°C, 700 g of deionized water was added over 50 minutes while stirring at 280 r/min (circumferential speed 88 m/min), and phase inversion emulsification was performed. While continuing to maintain the temperature at 73°C, methyl ethyl ketone was distilled off under reduced pressure to obtain an aqueous dispersion. Thereafter, while stirring at 280 r/min (circumferential speed 88 m/min), the aqueous dispersion was cooled to 30°C, and deionized water was added so that the solid content concentration was 20 mass%, thereby obtaining a resin particle dispersion Z-1. The volume median particle diameter _D50 of the obtained resin particles was 0.09 μm, and the CV value was 23%.

[Preparation of release agent particle dispersion]
Production Example W1 (Production of Release Agent Particle Dispersion W-1)
Into a 1 L beaker were added 120 g of deionized water, 86 g of resin particle dispersion Z-1, and 40 g of paraffin wax "HNP-9" (manufactured by Nippon Seiro Co., Ltd., melting point 75°C), and the mixture was melted by maintaining the temperature at 90 to 95°C and stirred to obtain a molten mixture.
The obtained molten mixture was dispersed for 20 minutes using an ultrasonic homogenizer "US-600T" (manufactured by Nippon Seiki Seisakusho Co., Ltd.) while maintaining the temperature at 90 to 95°C, and then cooled to room temperature (20°C). Deionized water was added to adjust the solid content to 20 mass%, to obtain release agent particle dispersion W-1. The volume median particle diameter _D50 of the release agent particles in the dispersion was 0.47 μm, and the CV value was 27%.

Production Example W2 (Production of Release Agent Particle Dispersion W-2)
A release agent particle dispersion W-2 was obtained in the same manner as in Production Example W1, except that the type of release agent used was changed to Fischer-Tropsch wax "FNP-0090" (manufactured by Nippon Seiro Co., Ltd., melting point 90°C). The volume median particle diameter _D50 of the release agent particles in the dispersion was 0.45 μm, and the CV value was 28%.

[Production of Addition Polymer]
Production Example E1 (Synthesis of Addition Polymer E-1)
16 parts by mass of methacrylic acid (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd.), 44 parts by mass of styrene (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd.), 30 parts by mass (15 parts by mass as solids) of styrene macromonomer "AS-6S" (manufactured by Toagosei Co., Ltd., number average molecular weight 6,000, solids content 50%), and 25 parts by mass of methoxypolyethylene glycol methacrylate "BLEMMER PME-200" (NOF Corporation) were mixed to prepare 115 parts by mass of a monomer mixed solution.
Into a reaction vessel, 18 parts by mass of methyl ethyl ketone, 0.03 parts by mass of 2-mercaptoethanol as a chain transfer agent, and 10% (11.5 parts by mass) of the monomer mixture were placed and mixed, and the atmosphere was thoroughly replaced with nitrogen gas.
On the other hand, the remaining 90% (103.5 parts by mass) of the monomer mixture was mixed with 0.27 parts by mass of the chain transfer agent, 42 parts by mass of methyl ethyl ketone, and 3 parts by mass of the polymerization initiator 2,2'-azobis(2,4-dimethylvaleronitrile) "V-65" (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) and placed in a dropping funnel, and the mixed solution in the reaction vessel was heated to 75°C under a nitrogen atmosphere while stirring, and the mixed solution in the dropping funnel was dropped over 3 hours. After 2 hours at 75°C from the end of the dropping, a solution in which 3 parts by mass of the polymerization initiator was dissolved in 5 parts by mass of methyl ethyl ketone was added, and the mixture was further aged at 75°C for 2 hours and at 80°C for 2 hours. Thereafter, methyl ethyl ketone was distilled off under reduced pressure drying to obtain an addition polymer E-1. The weight average molecular weight of the obtained addition polymer is shown in Table 4.

[Preparation of Colorant Particle Dispersion]
Production Example F1 (Production of Colorant Particle Dispersion F-1)
In a 5L container equipped with a stirrer equipped with a dispersing blade, a reflux condenser, a dropping funnel, a thermometer and a nitrogen inlet tube, 75 g of the addition polymer E-1 was dissolved in 620 g of methyl ethyl ketone, and then 96 g of a 5% by mass aqueous sodium hydroxide solution and 942 g of deionized water were added as a neutralizing agent, and the mixture was stirred with a dispersing blade at 20 ° C. for 10 minutes. Thereafter, 300 g of copper phthalocyanine pigment "ECB-301" (manufactured by Dainichi Seikagaku Kogyo Co., Ltd., Pigment Blue 15:3) was added, and the mixture was stirred with a dispersing blade at 6400 rpm at 20 ° C. for 2 hours. Thereafter, the mixture was passed through a 200 mesh filter and treated with a homogenizer "Microfluidizer M-110EH" (manufactured by Microfluidics Co., Ltd.) at a pressure of 150 MPa for 15 passes. The resulting dispersion was stirred at 70 ° C. under reduced pressure to remove methyl ethyl ketone and some water. The mixture was then passed through a 200 mesh filter, and deionized water was added to adjust the solid content to 20% by mass, to obtain colorant particle dispersion F-1. The colorant particles in the dispersion had a volume median particle size _D50 of 0.12 μm and a CV value of 21%.

[Toner Production]
Production Example 1 (Preparation of Toner Base Particles 1)
Into a 3 L four-neck flask equipped with a dehydration tube, a stirrer, and a thermocouple, 500 g of resin particle dispersion X-1, 35 g of release agent particle dispersion W-1, 35 g of release agent particle dispersion W-2, 63 g of colorant particle dispersion F-1, 10 g of a 10 mass% aqueous solution of polyoxyethylene (50) lauryl ether "EMULGEN 150" (manufactured by Kao Corporation, nonionic surfactant), and 10 g of a 15 mass% aqueous solution of sodium dodecylbenzenesulfonate "NEOPELEX G-15" (manufactured by Kao Corporation, anionic surfactant) were mixed at a temperature of 25° C. Next, while stirring the mixture, a solution prepared by dissolving 35 g of ammonium sulfate in 519 g of deionized water and adding 26 g of a 4.8 mass % aqueous potassium hydroxide solution was added dropwise at 25° C. over 10 minutes, and the temperature was then raised to 65° C. over 2 hours and maintained at 65° C. until the volume median particle size D ₅₀ of the aggregated particles reached 5.9 μm, thereby obtaining a dispersion of aggregated particles 1.
Subsequently, the dispersion of aggregated particles 1 was cooled to 59° C., and while maintaining the temperature at 59° C., 75 g of resin particle dispersion Y-1 was added over 90 minutes to obtain a dispersion of aggregated particles 2 in which resin particles were aggregated to aggregated particles 1.
To the obtained dispersion of aggregated particles 2, an aqueous solution obtained by mixing 41 g of sodium polyoxyethylene lauryl ether sulfate "EMAL E-27C" (manufactured by Kao Corporation, anionic surfactant, effective concentration 27% by mass), 1396 g of deionized water, and 26 g of a 0.1 mol/L aqueous sulfuric acid solution was added. Thereafter, the temperature was raised to 75°C over 1 hour, and the mixture was held at 75°C for 30 minutes, after which 75 g of a 0.1 mol/L aqueous sulfuric acid solution was added, and the mixture was further held at 75°C for 15 minutes. Thereafter, 25 g of a 0.1 mol/L aqueous sulfuric acid solution was added again, and the mixture was held at 75°C until the circularity reached 0.970, thereby obtaining a dispersion of fused particles in which aggregated particles were fused.
The obtained dispersion of fused particles was cooled to 30° C., and the solid content was separated by suction filtration, and then washed with deionized water at 25° C. and vacuum dried at 30° C. for 48 hours to obtain toner base particles 1. The physical properties of the obtained toner base particles 1 are shown in Table 5.

Production Examples 2 and 3 (Preparation of Toner Base Particles 2 and 3)
Toner base particles 2 and 3 were produced in the same manner as in Production Example 1, except that the circularity during the fusion step was changed as shown in Table 5. The physical properties of the obtained toner base particles 2 and 3 are shown in Table 5.

Production Example 4 (Preparation of Toner Base Particles 4)
In a 3 L four-neck flask equipped with a dehydration tube, a stirrer, and a thermocouple, 500 g of resin particle dispersion X-2, 84 g of release agent particle dispersion W-1, 72 g of colorant particle dispersion F-1, 15 g of a 10 mass % aqueous solution of polyoxyethylene (50) lauryl ether "EMULGEN 150" (manufactured by Kao Corporation, nonionic surfactant), and 17 g of a 15 mass % aqueous solution of sodium dodecylbenzenesulfonate "NEOPELEX G-15" (manufactured by Kao Corporation, anionic surfactant) were mixed at a temperature of 25° C. Next, while stirring the mixture, a solution prepared by dissolving 40 g of ammonium sulfate in 568 g of deionized water and adding a 4.8 mass % aqueous potassium hydroxide solution to adjust the pH to 8.6 was added dropwise at 25° C. over 10 minutes, and the temperature was raised to 63° C. over 2 hours and maintained at 63° C. until the volume median particle size D ₅₀ of the aggregated particles reached 5.9 μm, thereby obtaining a dispersion of aggregated particles 3.
Subsequently, the dispersion of aggregated particles 3 was cooled to 59° C., and while maintaining the temperature at 59° C., 75 g of resin particle dispersion Y-1 was added over 90 minutes to obtain a dispersion of aggregated particles 4 in which the resin particles were aggregated into aggregated particles 3.
To the obtained dispersion of aggregated particles 4, an aqueous solution obtained by mixing 48 g of sodium polyoxyethylene lauryl ether sulfate "EMAL E-27C" (manufactured by Kao Corporation, anionic surfactant, effective concentration 27% by mass), 600 g of deionized water, and 50 g of a 0.1 mol/L aqueous sulfuric acid solution was added. Thereafter, the temperature was raised to 75°C over 1 hour, and the mixture was held at 75°C for 30 minutes, after which 10 g of a 0.1 mol/L aqueous sulfuric acid solution was added, and the mixture was further held at 75°C for 15 minutes. Thereafter, 10 g of a 0.1 mol/L aqueous sulfuric acid solution was added again, and the mixture was held at 75°C until the circularity reached 0.970, thereby obtaining a dispersion of fused particles in which aggregated particles were fused.
The obtained dispersion of fused particles is cooled to 30° C., and the solid content is separated by suction filtration, and then washed with deionized water at 25° C. and vacuum dried at 30° C. for 48 hours to obtain toner base particles 4. The physical properties of the obtained toner base particles 4 are shown in Table 5.

Example 1 (Preparation of Toner 1)
Relative to 100 parts by mass of toner base particles 1, 6.4 parts by mass of hydrophobic large particle size silica "RY50" (manufactured by Nippon Aerosil Co., Ltd., hydrophobic treatment agent: polydimethylsiloxane, particle size converted from specific surface area: 119 nm) and 0.5 parts by mass of hydrophobic small particle size silica "R972" (manufactured by Nippon Aerosil Co., Ltd., hydrophobic treatment agent: dimethyldichlorosilane, particle size converted from specific surface area: 25 nm) were added to a Henschel mixer and stirred, and passed through a 150 mesh sieve to obtain toner 1. The evaluation results of the obtained toner 1 are shown in Table 5.

Examples 2 to 5, 8, 10, and 11 (Preparation of Toners 2 to 5, 8, 10, and 11)
Toners 2 to 5 were prepared in the same manner as in Example 1, except that the types and amounts of the external additives used were changed as shown in Table 5. The evaluation results of the obtained toners are shown in Table 5.

Example 6 (Preparation of Toner 6)
Relative to 100 parts by mass of toner base particles 2, 6.4 parts by mass of hydrophobic large particle size silica "RY50" (manufactured by Nippon Aerosil Co., Ltd., hydrophobic treatment agent: polydimethylsiloxane, particle size converted from specific surface area: 119 nm) and 0.5 parts by mass of hydrophobic small particle size silica "R972" (manufactured by Nippon Aerosil Co., Ltd., hydrophobic treatment agent: dimethyldichlorosilane, particle size converted from specific surface area: 25 nm) were added to a Henschel mixer and stirred, and passed through a 150 mesh sieve to obtain toner 6. The evaluation results of the obtained toner 6 are shown in Table 5.

Example 7 (Preparation of Toner 7)
Relative to 100 parts by mass of toner base particles 3, 6.4 parts by mass of hydrophobic large particle size silica "RY50" (manufactured by Nippon Aerosil Co., Ltd., hydrophobic treatment agent: polydimethylsiloxane, particle size converted from specific surface area: 119 nm) and 0.5 parts by mass of hydrophobic small particle size silica "R972" (manufactured by Nippon Aerosil Co., Ltd., hydrophobic treatment agent: dimethyldichlorosilane, particle size converted from specific surface area: 25 nm) were added to a Henschel mixer and stirred, and passed through a 150 mesh sieve to obtain toner 7. The evaluation results of the obtained toner 7 are shown in Table 5.

Example 9 (Preparation of Toner 9)
Relative to 100 parts by mass of toner base particles 4, 6.4 parts by mass of hydrophobic large particle size silica "RY50" (manufactured by Nippon Aerosil Co., Ltd., hydrophobic treatment agent: polydimethylsiloxane, particle size converted from specific surface area: 119 nm) and 0.5 parts by mass of hydrophobic small particle size silica "R972" (manufactured by Nippon Aerosil Co., Ltd., hydrophobic treatment agent: dimethyldichlorosilane, particle size converted from specific surface area: 25 nm) were added to a Henschel mixer, stirred, and passed through a 150 mesh sieve to obtain toner 9. The evaluation results of the obtained toner 9 are shown in Table 5.

Comparative Examples 1 and 2 (Preparation of Toners 14 and 15)
Toners 14 and 15 were prepared in the same manner as in Example 1, except that the types and amounts of the external additives used were changed as shown in Table 5. The evaluation results of the obtained toners are shown in Table 5.

From the results of the Examples and Comparative Examples, it is evident that by using the toner for developing electrostatic images of the present invention, the occurrence of fog is suppressed, and furthermore, the image density of the obtained image is highly stable.
In Example 8, which had charged particles, fog was further suppressed.
In Comparative Example 1, in which the mass ratio of the large silica particles to the small silica particles is less than 7, fogging occurred and the conveying amount decreased. In Comparative Example 2, in which the mass ratio of the large silica particles to the small silica particles is more than 18, toner leakage occurred.

Claims (7)

Toner base particles having a circularity of 0.965 or more,
small-diameter silica particles having a particle size of 10 nm or more and 30 nm or less calculated from a specific surface area;
and a step of externally adding large -diameter silica particles having a particle size of 70 nm or more and 190 nm or less, calculated based on the specific surface area,
the mass ratio of the large silica particles to the small silica particles (large silica particles/small silica particles) is 7 or more and 18 or less;
A method for producing a toner for developing electrostatic images. 2. The method for producing a toner for developing electrostatic images according to claim 1, wherein the amount of the small silica particles added is 0.4 parts by mass or more and 1.2 parts by mass or less, and the amount of the large silica particles added is 5 parts by mass or more and 18 parts by mass or less, relative to 100 parts by mass of the toner base particles. 3. The method for producing a toner for developing electrostatic images according to claim 1, wherein the toner base particles have a circularity of 0.995 or less. 4. The method for producing a toner for developing an electrostatic image according to claim 1, wherein the toner base particles contain a polyester resin as a binder resin. 5. The method for producing a toner for developing an electrostatic image according to claim 1, wherein the toner base particles contain a crystalline polyester resin and an amorphous polyester resin A as binder resins. 6. The method for producing a toner for developing electrostatic images according to claim 5, wherein the amorphous polyester resin A comprises a polyester resin segment which is a polycondensate of an alcohol component and a carboxylic acid component, and an addition polymerization resin segment which is an addition polymerization product of a raw material monomer containing a styrene compound. 7. The method for producing a toner for developing an electrostatic image according to claim 1, wherein the small silica particles and the large silica particles are hydrophobic silica particles.