JP7575261B2 - Toner for developing electrostatic images - Google Patents

Description

The present invention relates to a toner for developing electrostatic images, which is used to develop latent images formed in, for example, electrophotography, electrostatic recording, electrostatic printing, etc.

Toners that have a core-shell structure in which crystalline polyester resin is introduced into the core are being considered for use in electrophotography in order to achieve both low-temperature fixability and storage stability.

Patent Document 1 discloses a toner for developing electrostatic images, comprising toner particles containing a polyester resin (I) and a colorant, the toner particles being particles having a volume average particle size of 3 to 10 μm formed through a process including a step of dispersing in water at least resin particles having a volume average particle size of 1 μm or less and a step of aggregating the resin particles, the polyester resin (I) being composed of a linear polyester (A) and a nonlinear polyester (B), a polycondensation polyester resin of a carboxylic acid component and an alcohol component containing 40 mol % or more of one or more selected from aliphatic polycarboxylic acids having 9 to 30 carbon atoms and their ester-forming derivatives, and containing 5 wt % or more of a crystalline polyester (A1) having an SP value of 9.0 to 10.5 (cal/cm ³ ) ^1/2 in (A).

Patent Document 2 discloses a toner for developing electrostatic images that contains toner particles with a core-shell structure having a core and a shell, in which the core contains a styrene-based resin (AS) and a crystalline resin (C) that is a polycondensation product of an alcohol component (C-al) containing 95 mol% to 100 mol% of 1,6-hexanediol and a carboxylic acid component (C-ac) containing 95 mol% to 100 mol% of an aliphatic dicarboxylic acid compound having 12 to 16 carbon atoms, and the shell contains an amorphous composite resin (AH) that contains a polyester segment (AH-1) that is a polycondensation portion of an alcohol component (A-al) containing an alkylene oxide adduct of bisphenol A and a carboxylic acid component (A-ac) containing 7 mol% to 40 mol% of succinic acid, and a vinyl resin segment (AH-2) that is an addition polymerization portion of a monomer component (A-st) containing a styrene-based compound.

Patent Document 3 discloses a toner for developing electrostatic latent images, which contains at least a binder resin and a release agent, and is characterized in that the binder resin contains at least a crystalline polyester resin, the endothermic peak top temperature during heating of the toner measured by differential scanning calorimetry is 70° C. or higher, and the heat generation amount ΔH _c (L) below (heat generation peak top temperature r _c -7° C.) is 15% or less of the total heat generation amount ΔH _c of the heat generation peak during cooling of the toner measured by differential scanning calorimetry.

JP 2010-38969 A JP 2020-76890 A JP 2018-5225 A

However, core-shell toners that incorporate crystalline polyester resin into the core are prone to regulation failure. Regulation failure is a phenomenon in which the toner regulation member is no longer able to adequately regulate the amount of toner loaded on the developing roller.

The present invention relates to a toner for developing electrostatic images that can suppress the occurrence of regulation failures.

The present invention relates to a toner for developing electrostatic images having a core-shell structure, the core of which contains a styrene-based resin S and a crystalline polyester resin CP which is a polycondensate of an alcohol component and a carboxylic acid component, the alcohol component of the crystalline polyester resin CP containing 2 mol % to 60 mol % of an aliphatic monoalcohol having 10 to 30 carbon atoms, and/or the carboxylic acid component containing 2 mol % to 60 mol % of an aliphatic monocarboxylic acid compound having 10 to 30 carbon atoms.

The toner for developing electrostatic images of the present invention is highly effective in preventing the occurrence of regulation failures.

The toner for developing electrostatic images of the present invention has a core-shell structure, and is characterized in that the core contains a crystalline polyester resin (crystalline polyester CP) obtained using a styrene-based resin (styrene-based resin S) and a monovalent long-chain aliphatic monomer. Although the details are unclear, it is presumed that the effects of the present invention are achieved through the following mechanism.

By including a crystalline polyester resin and a styrene-based resin in the core, low-temperature fixing property is improved, but on the other hand, regulation failure is likely to occur. This is because the compatibility between the crystalline polyester resin and the styrene-based resin is poor, and when forming the core particles, particles of only the crystalline polyester resin tend to be formed, and it is difficult to increase the circularity, which reduces the fluidity of the toner.
In contrast, in the present invention, by introducing a monovalent long-chain aliphatic monomer that acts as a locally hydrophobic portion into the crystalline polyester resin of the core, compatibility with the styrene-based resin improves and the circularity of the core particles can be increased, which is thought to improve the fluidity of the toner and suppress poor regulation.

The toner for developing electrostatic images of the present invention contains toner particles having a core-shell structure, and the core contains a styrene-based resin S and a crystalline polyester resin CP.

The crystallinity of a resin is represented by a crystallinity index defined as the ratio of the softening point to the maximum endothermic peak temperature measured by a differential scanning calorimeter, i.e., the value of [softening point/maximum endothermic peak temperature]. A crystalline resin is a resin having a crystallinity index of 0.6 or more, preferably 0.7 or more, more preferably 0.9 or more, and 1.4 or less, preferably 1.2 or less, more preferably 1.1 or less.
On the other hand, an amorphous resin is a resin in which no endothermic peak is observed, or if an endothermic peak is observed, the crystallinity index is greater than 1.4, preferably greater than 1.5, more preferably 1.6 or more, or less than 0.6, preferably 0.5 or less.
The crystallinity of the resin can be adjusted by the type and ratio of the raw material monomers, and the production conditions (e.g., reaction temperature, reaction time, cooling rate), etc. The maximum endothermic peak temperature refers to the temperature of the peak with the largest peak area among the observed endothermic peaks. In the case of a crystalline resin, the maximum endothermic peak temperature is the melting point.

Styrene-based resin S is an addition polymer of raw material monomers that contain at least styrene or styrene derivatives such as α-methylstyrene and vinyltoluene (hereinafter, styrene and styrene derivatives are collectively referred to as "styrene compounds").

The content of the styrene compound, preferably styrene, in the raw monomer of the styrene-based resin S is preferably 50% by mass or more, more preferably 70% by mass or more, and even more preferably 80% by mass or more, from the viewpoint of improving the heat-resistant storage stability of the toner, and is preferably 95% by mass or less, more preferably 93% by mass or less, and even more preferably 90% by mass or less, from the viewpoint of improving the low-temperature fixing property of the toner.

From the viewpoint of encapsulating the release agent in the toner, the styrene resin S is preferably an addition polymer of a styrene compound and an alkyl (meth)acrylate. Examples of alkyl (meth)acrylate include butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, and (iso)octyl (meth)acrylate. It is preferable to use one or more of these. In this specification, "(iso)" means that both the case where this group is present and the case where it is not present are included, and when these groups are not present, it indicates that it is normal. Furthermore, "(meth)acrylic acid" refers to acrylic acid, methacrylic acid, or both.

The number of carbon atoms in the alkyl group in the (meth)acrylic acid alkyl ester used as the raw material monomer for the styrene-based resin S is preferably 2 or more, more preferably 3 or more, from the viewpoint of improving the low-temperature fixing property of the toner, and is preferably 8 or less, more preferably 6 or less. The number of carbon atoms in the alkyl ester refers to the number of carbon atoms derived from the alcohol that constitutes the ester.

The raw material monomers for the styrene-based resin S may include raw material monomers other than styrene compounds and (meth)acrylic acid alkyl esters, for example, ethylenically unsaturated monoolefins such as ethylene and propylene; diolefins such as butadiene; halovinyls such as vinyl chloride; vinyl esters such as vinyl acetate and vinyl propionate; ethylenically monocarboxylic acid esters such as dimethylaminoethyl (meth)acrylate; vinyl ethers such as methyl vinyl ether; vinylidene halides such as vinylidene chloride; and N-vinyl compounds such as N-vinylpyrrolidone.

The addition polymerization reaction of the raw material monomers of the styrene-based resin S can be carried out in the presence of a polymerization initiator such as dicumyl peroxide or tert-butyl peroxide, a polymerization inhibitor, a crosslinking agent, etc., in the presence of an organic solvent or without a solvent, and the temperature conditions are preferably 110°C or higher, more preferably 130°C or higher, and preferably 200°C or lower, more preferably 170°C or lower.

When an organic solvent is used in the addition polymerization reaction, xylene, toluene, methyl ethyl ketone, acetone, etc. can be used. The amount of the organic solvent used is preferably 10 parts by mass or more and 50 parts by mass or less per 100 parts by mass of the raw material monomer of the styrene-based resin.

The softening point of the styrene resin S is preferably 90°C or higher, more preferably 100°C or higher, and even more preferably 110°C or higher, from the viewpoint of improving the hot offset resistance of the toner, and is preferably 135°C or lower, more preferably 130°C or lower, and even more preferably 125°C or lower, from the viewpoint of improving the low-temperature fixing property of the toner.

From the viewpoint of improving the fluidity of the toner, the styrene-based resin S is preferably an amorphous resin.

The maximum endothermic peak temperature of the styrene resin S is preferably 40°C or higher, more preferably 50°C or higher, and even more preferably 55°C or higher, from the viewpoint of improving the heat-resistant storage stability of the toner, and is preferably 80°C or lower, more preferably 70°C or lower, and even more preferably 65°C or lower, from the viewpoint of improving the low-temperature fixing property of the toner.

The glass transition temperature of the styrene resin S is preferably 40°C or higher, more preferably 45°C or higher, and even more preferably 50°C or higher, from the viewpoint of improving the heat-resistant storage stability of the toner, and is preferably 75°C or lower, more preferably 65°C or lower, and even more preferably 60°C or lower, from the viewpoint of improving the low-temperature fixing ability of the toner.

From the viewpoint of improving the charging stability of the toner, the acid value of the styrene-based resin S is preferably 15 mgKOH/g or less, more preferably 10 mgKOH/g or less, and even more preferably 5 mgKOH/g or less.

The content of styrene-based resin S in the resin constituting the core is preferably 60% by mass or more, more preferably 70% by mass or more, even more preferably 75% by mass or more, and preferably 97% by mass or less, more preferably 90% by mass or less, even more preferably 85% by mass or less.

Crystalline polyester resin CP is a polycondensate of an alcohol component and a carboxylic acid component, in which the alcohol component contains 2 mol % to 60 mol % of an aliphatic monoalcohol having 10 to 30 carbon atoms, and/or the carboxylic acid component contains 2 mol % to 60 mol % of an aliphatic monocarboxylic acid compound having 10 to 30 carbon atoms.

Examples of aliphatic monoalcohols having 10 to 30 carbon atoms include capric alcohol, lauryl alcohol, myristyl alcohol, palmityl alcohol, stearyl alcohol, behenyl alcohol, and lignoceryl alcohol.

The carbon number of the aliphatic monoalcohol is 10 or more, preferably 12 or more, more preferably 14 or more, from the viewpoint of suppressing regulation failure, and is 30 or less, preferably 25 or less, more preferably 20 or less, from the viewpoint of improving the low-temperature fixing property of the toner.

When the alcohol component contains an aliphatic monoalcohol having 10 to 30 carbon atoms, the content of such aliphatic monoalcohol in the alcohol component is 2 mol% or more, preferably 3 mol% or more, more preferably 4 mol% or more, and 60 mol% or less, preferably 40 mol% or less, more preferably 20 mol% or less, and even more preferably 10 mol% or less.

Examples of aliphatic monocarboxylic acid compounds having 10 to 30 carbon atoms include aliphatic monocarboxylic acids such as capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, behenic acid, and lignoceric acid, and alkyl esters of these acids in which the alkyl group has 1 to 3 carbon atoms.

The carbon number of the aliphatic monocarboxylic acid compound is 10 or more, preferably 12 or more, more preferably 14 or more, from the viewpoint of suppressing poor regulation, and is 30 or less, preferably 25 or less, more preferably 20 or less, from the viewpoint of improving the low-temperature fixing property of the toner. Here, when the aliphatic monocarboxylic acid compound is an alkyl ester, the carbon number of the alkyl group is not included in the above carbon number.

When the carboxylic acid component contains an aliphatic monocarboxylic acid compound having 10 to 30 carbon atoms, the content of such aliphatic monocarboxylic acid compound in the alcohol component is 2 mol% or more, preferably 3 mol% or more, more preferably 4 mol% or more, and 60 mol% or less, preferably 40 mol% or less, more preferably 20 mol% or less, and even more preferably 10 mol% or less.

As an alcohol component other than the aliphatic monoalcohol, an aliphatic diol is preferred.

Examples of aliphatic diols include ethylene glycol, 1,4-butanediol, 1,6-hexanediol, 1,10-decanediol, 1,12-dodecanediol, and 1,14-tetradecanediol.

The carbon number of the aliphatic diol is preferably 2 or more, more preferably 4 or more, from the viewpoint of improving the heat-resistant storage stability of the toner, and is preferably 14 or less, more preferably 12 or less, even more preferably 10 or less, and even more preferably 8 or less, from the viewpoint of improving the low-temperature fixing property of the toner.

The aliphatic diol may be either saturated or unsaturated, but in the present invention, from the viewpoint of low-temperature fixability, it is preferable that the diol is saturated.

When the alcohol component contains an aliphatic monoalcohol, the content of the aliphatic diol in the alcohol component is preferably 40 mol% or more, more preferably 60 mol% or more, even more preferably 80 mol% or more, and preferably 98 mol% or less, more preferably 97 mol% or less, even more preferably 96 mol% or less.

When the alcohol component does not contain an aliphatic monoalcohol, the content of the aliphatic diol in the alcohol component is preferably 80 mol% or more, more preferably 90 mol% or more, even more preferably 95 mol% or more, even more preferably 98 mol% or more, and even more preferably 100 mol%.

Other alcohol components include aromatic diols such as alkylene oxide adducts of bisphenol A, and trihydric or higher alcohols such as sorbitol, pentaerythritol, glycerin, and trimethylolpropane.

As the carboxylic acid component other than the aliphatic monocarboxylic acid compound, an aliphatic dicarboxylic acid compound, more preferably a straight-chain aliphatic dicarboxylic acid compound, is preferred.

Examples of aliphatic dicarboxylic acid compounds include succinic acid (carbon number: 4), fumaric acid (carbon number: 4), adipic acid (carbon number: 6), suberic acid (carbon number: 8), azelaic acid (carbon number: 9), sebacic acid (carbon number: 10), dodecanedioic acid (carbon number: 12), tetradecanedioic acid (carbon number: 14), hexadecanedioic acid (carbon number: 16), succinic acid having an alkyl or alkenyl group on the side chain, anhydrides of these acids, and alkyl esters in which the alkyl group has 1 to 3 carbon atoms. Of these, dodecanedioic acid or tetradecanedioic acid is preferred, and tetradecanedioic acid is more preferred.

The carbon number of the aliphatic dicarboxylic acid compound is preferably 10 or more, more preferably 12 or more, from the viewpoint of improving the heat-resistant storage stability of the toner, and is preferably 16 or less, more preferably 14 or less, from the viewpoint of improving the low-temperature fixing property of the toner. Here, when the aliphatic monocarboxylic acid compound is an alkyl ester, the carbon number of the alkyl group is not included in the above carbon number.

When the carboxylic acid component contains an aliphatic monocarboxylic acid compound, the content of the aliphatic dicarboxylic acid compound, preferably a straight-chain aliphatic dicarboxylic acid compound having 10 to 16 carbon atoms, in the carboxylic acid component is preferably 40 mol% or more, more preferably 60 mol% or more, even more preferably 80 mol% or more, and preferably 98 mol% or less, more preferably 97 mol% or less, even more preferably 96 mol% or less.

When the carboxylic acid component does not contain an aliphatic monocarboxylic acid compound, the content of the aliphatic dicarboxylic acid compound, preferably a straight-chain aliphatic dicarboxylic acid compound having 10 to 16 carbon atoms, in the carboxylic acid component is preferably 60 mol% or more, more preferably 70 mol% or more, even more preferably 80 mol% or more, and even more preferably 100 mol%.

Other carboxylic acid components include aromatic dicarboxylic acid compounds such as phthalic acid, isophthalic acid, and terephthalic acid, trivalent or higher carboxylic acids such as trimellitic acid and pyromellitic acid, anhydrides of these acids, and alkyl esters in which the alkyl group has 1 to 3 carbon atoms.

The equivalent ratio (COOH group/OH group) of the carboxylic acid component to the alcohol component in the crystalline polyester resin CP is preferably 0.6 or more, more preferably 0.7 or more, even more preferably 0.75 or more, from the viewpoint of adjusting the softening point of the polyester resin, and is preferably 1.2 or less, more preferably 1.15 or less.

Crystalline polyester resin CP can be obtained, for example, by polycondensing an alcohol component and a carboxylic acid component in an inert gas atmosphere, preferably in the presence of an esterification catalyst, and, if necessary, in the presence of an esterification promoter, a polymerization inhibitor, etc., at a temperature of preferably 130°C or higher, more preferably 170°C or higher, and preferably 250°C or lower, more preferably 240°C or lower.

Examples of the esterification catalyst include tin compounds such as dibutyltin oxide and tin(II) 2-ethylhexanoate, and titanium compounds such as titanium diisopropylate bistriethanolamine, with tin compounds being preferred. The amount of the esterification catalyst used is preferably 0.01 parts by mass or more, more preferably 0.1 parts by mass or more, and preferably 1.5 parts by mass or less, more preferably 1 part by mass or less, relative to 100 parts by mass of the total amount of the alcohol component and the carboxylic acid component. Examples of the esterification promoter include gallic acid. The amount of the esterification promoter used is preferably 0.001 parts by mass or more, more preferably 0.01 parts by mass or more, and preferably 0.5 parts by mass or less, more preferably 0.1 parts by mass or less, relative to 100 parts by mass of the total amount of the alcohol component and the carboxylic acid component. Examples of the polymerization inhibitor include tert-butylcatechol. The amount of the polymerization inhibitor used is preferably 0.001 parts by mass or more, more preferably 0.01 parts by mass or more, and preferably 0.5 parts by mass or less, more preferably 0.1 parts by mass or less, per 100 parts by mass of the total amount of the alcohol component and the carboxylic acid component.

The softening point of the crystalline polyester resin CP is preferably 60°C or higher, more preferably 65°C or higher, and even more preferably 70°C or higher, from the viewpoint of improving the heat-resistant storage stability of the toner, and is preferably 120°C or lower, more preferably 100°C or lower, and even more preferably 90°C or lower, from the viewpoint of improving the low-temperature fixing property of the toner.

The maximum endothermic peak temperature of the crystalline polyester resin CP is preferably 55°C or higher, more preferably 60°C or higher, and even more preferably 65°C or higher, from the viewpoint of improving the heat-resistant storage stability of the toner, and is preferably 100°C or lower, more preferably 90°C or lower, and even more preferably 85°C or lower, from the viewpoint of improving the low-temperature fixing property of the toner.

From the viewpoint of improving the charging stability of the toner, the acid value of the crystalline polyester resin CP 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 hydroxyl value of the crystalline polyester resin CP is preferably 0.5 mgKOH/g or more, and from the viewpoint of improving the charging stability of the toner, is preferably 20 mgKOH/g or less, more preferably 15 mgKOH/g or less, and even more preferably 10 mgKOH/g or less.

The content of crystalline polyester resin CP in the resin constituting the core is preferably 3% by mass or more, more preferably 10% by mass or more, even more preferably 15% by mass or more, and preferably 40% by mass or less, more preferably 30% by mass or less, even more preferably 25% by mass or less.

The mass ratio of the styrene resin S to the crystalline polyester resin CP in the core (styrene resin S/crystalline polyester resin CP) is preferably 60/40 or more, more preferably 65/35 or more, even more preferably 70/30 or more, and even more preferably 75/25 or more, from the viewpoint of encapsulating the release agent in the toner, and is preferably 97/3 or less, more preferably 95/5 or less, even more preferably 90/10 or less, and even more preferably 85/15 or less, from the viewpoint of improving the low-temperature fixing property of the toner.

The proportion of the resin constituting the core in the binder resin is preferably 60% by mass or more, more preferably 70% by mass or more, even more preferably 75% by mass or more, and preferably 95% by mass or less, more preferably 93% by mass or less, even more preferably 90% by mass or less.

Examples of the shell include amorphous polyester resins and amorphous composite resins in which polyester resins and styrene-based resins are bonded together. In the present invention, from the viewpoint of improving compatibility with the core, the shell preferably contains an amorphous composite resin AC in which a polyester resin ACP obtained by polycondensing raw material monomers consisting of an alcohol component and a carboxylic acid component is bonded to a styrene-based resin ACS obtained by addition polymerization of a raw material monomer containing a styrene compound.

The alcohol component of polyester resin ACP is represented by formula (I):

(In the formula, OR and RO are oxyalkylene groups, R is an ethylene group and/or a propylene group, x and y are the average number of moles of alkylene oxide added, each of which is a positive number, and the sum of x and y is 1 or more, preferably 1.5 or more, and 16 or less, preferably 8 or less, more preferably 6 or less, and even more preferably 4 or less.)
It is preferable that the alkylene oxide adduct of bisphenol A represented by the following formula is contained.

The content of the alkylene oxide adduct of bisphenol A represented by formula (I) in the alcohol component is preferably 70 mol% or more, more preferably 80 mol% or more, even more preferably 90 mol% or more, even more preferably 95 mol% or more, and even more preferably 100 mol%.

Other alcohol components include aliphatic diols, bisphenol A, hydrogenated bisphenol A, trihydric or higher alcohols, etc.

Carboxylic acid components include aromatic dicarboxylic acid compounds, aliphatic dicarboxylic acid compounds, trivalent or higher carboxylic acid compounds, etc.

Examples of aromatic dicarboxylic acid compounds include phthalic acid, isophthalic acid, terephthalic acid, anhydrides of these acids, and alkyl esters of these acids having 1 to 3 carbon atoms.

The content of the aromatic dicarboxylic acid compound in the carboxylic acid component is preferably 60% by mass or more, more preferably 70% by mass or more, and preferably 95% by mass or less, more preferably 90% by mass or less.

Aliphatic dicarboxylic acid compounds include succinic acid (carbon number: 4), fumaric acid (carbon number: 4), adipic acid (carbon number: 6), suberic acid (carbon number: 8), azelaic acid (carbon number: 9), sebacic acid (carbon number: 10), dodecanedioic acid (carbon number: 12), tetradecanedioic acid (carbon number: 14), succinic acid having an alkyl or alkenyl group on the side chain, anhydrides of these acids, and alkyl esters of these acids having 1 to 3 carbon atoms.

The carbon number of the aliphatic dicarboxylic acid compound is preferably 4 or more from the viewpoint of low-temperature fixability, and is preferably 14 or less, more preferably 12 or less, from the viewpoint of storage stability.

Examples of trivalent or higher carboxylic acid compounds include trimellitic acid, pyromellitic acid, anhydrides of these acids, and alkyl esters of these acids having 1 to 3 carbon atoms.

In addition, the alcohol component may contain a monohydric alcohol, and the carboxylic acid component may contain a monovalent carboxylic acid compound, as appropriate, from the viewpoint of adjusting the molecular weight and softening point of the polyester resin.

The styrene-based resin ACS is an addition polymer of raw material monomers that contain at least styrene or styrene derivatives such as α-methylstyrene and vinyltoluene (hereinafter, styrene and styrene derivatives are collectively referred to as "styrene compounds").

The content of the styrene compound, preferably styrene, in the raw monomer of the styrene-based resin ACS is preferably 50% by mass or more, more preferably 70% by mass or more, and even more preferably 80% by mass or more, from the viewpoint of improving the heat-resistant storage stability of the toner, and is preferably 95% by mass or less, more preferably 93% by mass or less, and even more preferably 90% by mass or less, from the viewpoint of improving the low-temperature fixing property of the toner.

In addition, from the viewpoint of suppressing regulation failure, the styrene-based resin ACS is preferably an addition polymer of a styrene compound and an alkyl (meth)acrylate ester having an alkyl group with 7 to 20 carbon atoms. Examples of the alkyl (meth)acrylate ester include 2-ethylhexyl (meth)acrylate, (iso)octyl (meth)acrylate, (iso)decyl (meth)acrylate, and (iso)stearyl (meth)acrylate. It is preferable to use one or more of these. In this specification, "(iso)" means both the case where this group is present and the case where it is not, and when this group is not present, it indicates that it is normal. Furthermore, "(meth)acrylic acid" refers to acrylic acid, methacrylic acid, or both.

The number of carbon atoms in the alkyl group in the (meth)acrylic acid alkyl ester used as the raw material monomer for the styrene-based resin ACS is preferably 7 or more, more preferably 8 or more, from the viewpoint of improving the low-temperature fixing property of the toner, and is preferably 14 or less, more preferably 12 or less. The number of carbon atoms in the alkyl ester refers to the number of carbon atoms derived from the alcohol that constitutes the ester.

The raw material monomers for the styrene-based resin ACS may include raw material monomers other than styrene compounds and (meth)acrylic acid alkyl esters, for example, ethylenically unsaturated monoolefins such as ethylene and propylene; diolefins such as butadiene; halovinyls such as vinyl chloride; vinyl esters such as vinyl acetate and vinyl propionate; ethylenically monocarboxylic acid esters such as dimethylaminoethyl (meth)acrylate; vinyl ethers such as methyl vinyl ether; vinylidene halides such as vinylidene chloride; and N-vinyl compounds such as N-vinylpyrrolidone.

The addition polymerization reaction of the raw material monomers of the styrene-based resin ACS can be carried out by a conventional method, for example, in the presence of a radical polymerization initiator, a polymerization inhibitor, a crosslinking agent, etc., in the presence of an organic solvent or without a solvent, and the temperature conditions are preferably 110°C or higher, more preferably 140°C or higher, and preferably 200°C or lower, more preferably 170°C or lower.

When an organic solvent is used in the addition polymerization reaction, xylene, toluene, methyl ethyl ketone, acetone, etc. can be used. The amount of the organic solvent used is preferably 10 parts by mass or more and 50 parts by mass or less per 100 parts by mass of the raw material monomer of the styrene-based resin.

It is more preferable that the amorphous composite resin AC is a resin in which the polyester resin ACP and the styrene-based resin ACS are covalently bonded together via a bireactive monomer that can react with both the raw material monomers of the polyester resin ACP and the raw material monomers of the styrene-based resin ACS.

The bireactive monomer is preferably a compound having at least one functional group selected from the group consisting of hydroxyl group, carboxyl group, epoxy group, primary amino group, and secondary amino group, preferably a hydroxyl group and/or a carboxyl group, more preferably a carboxyl group, and an ethylenically unsaturated bond in the molecule, more preferably at least one selected from the group consisting of acrylic acid, methacrylic acid, fumaric acid, maleic acid, and maleic anhydride, and from the viewpoint of the reactivity of the polycondensation reaction and the addition polymerization reaction, at least one selected from the group consisting of acrylic acid, methacrylic acid, and fumaric acid is even more preferable, and acrylic acid is even more preferable. However, when used together with a polymerization inhibitor, a polyvalent carboxylic acid compound having an ethylenically unsaturated bond such as fumaric acid functions as a raw material monomer for polyester resin. In this case, fumaric acid, etc. is not a bireactive monomer, but a raw material monomer for polyester resin.

The amount of the bireactive monomer used is preferably 1 mol or more, more preferably 2 mol or more, and even more preferably 3 mol or more, based on a total of 100 mol of the alcohol components of the polyester resin ACP, from the viewpoint of low-temperature fixing property, and is preferably 30 mol or less, more preferably 20 mol or less, and even more preferably 10 mol or less, from the viewpoint of improving the dispersibility of the styrene-based resin and the polyester resin and improving the durability of the toner.
The amount of the bireactive monomer used is preferably 1 part by mass or more, more preferably 2 parts by mass or more, based on 100 parts by mass of the total of the raw material monomers of the styrene-based resin ACS from the viewpoint of low-temperature fixability, and is preferably 30 parts by mass or less, more preferably 20 parts by mass or less, and even more preferably 10 parts by mass or less, from the viewpoint of improving the dispersibility of the styrene-based resin and the polyester resin and improving the durability of the toner. Here, the polymerization initiator is included in the total of the raw material monomers of the styrene-based resin.

Specifically, the amorphous composite resin AC is preferably produced by the following method. When a bireactive monomer is used, it is preferable to use the bireactive monomer in an addition polymerization reaction together with the raw material monomer of the styrene resin from the viewpoint of improving the durability of the toner and improving the low-temperature fixing property and heat-resistant storage stability of the toner.

(i) A method in which step (A) of polycondensation reaction with raw material monomers of polyester resin is followed by step (B) of addition polymerization reaction with raw material monomers of styrene resin and bireactive monomers. In this method, step (A) is carried out under reaction temperature conditions suitable for polycondensation reaction, the reaction temperature is lowered, and step (B) is carried out under temperature conditions suitable for addition polymerization reaction. It is preferable that raw material monomers of styrene resin and bireactive monomers are added to the reaction system at a temperature suitable for addition polymerization reaction. Bireactive monomers carry out addition polymerization reaction and also react with polyester resin.
After step (B), the reaction temperature is increased again, and if necessary, a raw material monomer of a polyester resin having a valence of three or more and serving as a crosslinking agent is added to the polymerization system, so that the polycondensation reaction of step (A) and the reaction with the bireactive monomer can be further promoted.

(ii) A method in which step (B) of an addition polymerization reaction of raw material monomers of a styrene-based resin and a bireactive monomer is followed by step (A) of a polycondensation reaction of raw material monomers of a polyester resin. In this method, step (B) is carried out under reaction temperature conditions suitable for an addition polymerization reaction, and the reaction temperature is raised to carry out the polycondensation reaction of step (A) under temperature conditions suitable for a polycondensation reaction. The bireactive monomer is involved in both the addition polymerization reaction and the polycondensation reaction.
The raw material monomers of the polyester resin may be present in the reaction system during the addition polymerization reaction, or may be added to the reaction system under temperature conditions suitable for the polycondensation reaction. In the former case, the progress of the polycondensation reaction can be controlled by adding an esterification catalyst at a temperature suitable for the polycondensation reaction.

(iii) A method of carrying out the reaction under conditions in which the step (A) of the polycondensation reaction of the raw material monomer of the polyester resin and the step (B) of the addition polymerization reaction of the raw material monomer of the styrene resin and the bireactive monomer proceed in parallel. In this method, it is preferable to carry out the steps (A) and (B) in parallel under reaction temperature conditions suitable for the addition polymerization reaction, raise the reaction temperature, add a raw material monomer of the polyester resin having a valence of 3 or more as a crosslinking agent to the polymerization system as necessary under temperature conditions suitable for the polycondensation reaction, and further carry out the polycondensation reaction of step (A). At that time, under temperature conditions suitable for the polycondensation reaction, it is also possible to add a polymerization inhibitor to proceed with only the polycondensation reaction. The bireactive monomer is involved in the polycondensation reaction as well as the addition polymerization reaction.

In the above method (i), a prepolymerized polycondensation resin may be used instead of step (A) in which a polycondensation reaction is carried out. In the above method (iii), when the reaction is carried out under conditions in which steps (A) and (B) proceed in parallel, a mixture containing raw material monomers for a styrene resin may be dripped into a mixture containing raw material monomers for a polyester resin to cause the reaction.

The above methods (i) to (iii) are preferably carried out in the same container.

The mass ratio of polyester resin ACP to styrene-based resin ACS in the amorphous composite resin AC (polyester resin ACP/styrene-based resin ACS) is preferably 60/40 or more, more preferably 70/30 or more, and even more preferably 80/20 or more from the viewpoint of low-temperature fixability, and is preferably 98/2 or less, more preferably 95/5 or less, and even more preferably 90/10 or less from the viewpoint of grindability. In the above calculation, the mass of the polyester resin is the mass of the raw material monomer of the polyester resin used minus the amount of reaction water dehydrated by the polycondensation reaction (calculated value), and the amount of the bireactive monomer is included in the amount of raw material monomer of the polyester resin. The amount of the styrene-based resin is the total amount of the raw material monomer of the styrene-based resin and the polymerization initiator.

The softening point of the amorphous composite resin AC is preferably 80°C or higher, more preferably 90°C or higher, and even more preferably 100°C or higher, from the viewpoint of improving the hot offset resistance of the toner, and is preferably 140°C or lower, more preferably 130°C or lower, and even more preferably 120°C or lower, from the viewpoint of improving the low-temperature fixing property of the toner.

The maximum endothermic peak temperature of the amorphous composite resin AC is preferably 45°C or higher, more preferably 50°C or higher, and even more preferably 55°C or higher, from the viewpoint of improving the heat-resistant storage stability of the toner, and is preferably 80°C or lower, more preferably 75°C or lower, and even more preferably 70°C or lower, from the viewpoint of improving the low-temperature fixing property of the toner.

The glass transition temperature of the amorphous composite resin AC is preferably 40°C or higher, more preferably 50°C or higher, and even more preferably 55°C or higher, from the viewpoint of improving the heat-resistant storage stability of the toner, and is preferably 75°C or lower, more preferably 70°C or lower, and even more preferably 65°C or lower, from the viewpoint of improving the low-temperature fixing property of the toner.

From the viewpoint of improving the aggregation stability during toner production, the acid value of the amorphous composite resin AC is preferably 5 mgKOH/g or more, more preferably 8 mgKOH/g or more, even more preferably 10 mgKOH/g or more, and is preferably 30 mgKOH/g or less, more preferably 27 mgKOH/g or less, even more preferably 25 mgKOH/g or less.

The content of the amorphous composite resin AC in the resin constituting the shell is preferably 80% by mass or more, more preferably 90% by mass or more, even more preferably 95% by mass or more, even more preferably 98% by mass or more, and even more preferably 100% by mass.

The proportion of the resin constituting the shell in the binder resin is preferably 5% by mass or more, more preferably 7% by mass or more, even more preferably 10% by mass or more, and is preferably 40% by mass or less, more preferably 30% by mass or less, even more preferably 25% by mass or less.

The toner of the present invention may contain additives such as colorants, release agents, charge control agents, magnetic powders, flowability improvers, conductivity regulators, reinforcing fillers such as fibrous substances, antioxidants, and cleaning improvers in the core and/or shell, preferably in the core.

As the colorant, dyes, pigments, magnetic materials, etc., which are used as colorants for toners, can be used. In the present invention, the toner may be either a black toner or a color toner.

As colorants, dyes, pigments, magnetic materials, etc. used as toner colorants can be used. Examples include carbon black, phthalocyanine blue, permanent brown FG, brilliant fast scarlet, pigment red 122, pigment green B, rhodamine B base, solvent red 49, solvent red 146, solvent blue 35, quinacridone, carmine 6B, isoindoline, disazo yellow, etc. In the present invention, the toner may be either a black toner or a color toner.

From the viewpoint of improving the image density and low-temperature fixability of the toner, the content of the colorant in the toner is preferably 1% by mass or more, more preferably 2% by mass or more, and is preferably 40% by mass or less, more preferably 20% by mass or less, and even more preferably 10% by mass or less.

Examples of release agents include hydrocarbon waxes such as polypropylene wax, polyethylene wax, polypropylene-polyethylene copolymer wax, microcrystalline wax, paraffin wax, Fischer-Tropsch wax, and Sasol wax, and oxides thereof; ester waxes such as carnauba wax, montan wax, and deacidified waxes thereof, and fatty acid ester wax; fatty acid amides, fatty acids, higher alcohols, and fatty acid metal salts; and the like, which can 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, from the viewpoint of toner transferability, and is preferably 160°C or lower, more preferably 140°C or lower, even more preferably 120°C or lower, and even more preferably 110°C or lower, from the viewpoint of low-temperature fixability.

From the viewpoint of the low-temperature fixing property and offset resistance of the toner, the content of the release agent in the toner is preferably 1% by mass or more, and preferably 15% by mass or less, more preferably 10% by mass or less, and even more preferably 8% by mass or less.

The charge control agent is not particularly limited, and may contain either a positively charged charge control agent or a negatively charged charge control agent.

Positively charged charge control agents include nigrosine dyes such as "Nigrosine Base EX", "Oil Black BS", "Oil Black SO", "Bontron N-01", "Bontron N-04", "Bontron N-07", "Bontron N-09", and "Bontron N-11" (all manufactured by Orient Chemical Industries Co., Ltd.); triphenylmethane dyes containing a tertiary amine as a side chain; quaternary ammonium salt compounds such as "Bontron P-51" (manufactured by Orient Chemical Industries Co., Ltd.), cetyltrimethylammonium bromide, and "COPY CHARGE PX VP435 (Clariant), etc.; polyamine resins, such as AFP-B (Orient Chemical Industries, Ltd.); imidazole derivatives, such as PLZ-2001 and PLZ-8001 (both manufactured by Shikoku Chemical Industries, Ltd.); styrene-acrylic resins, such as FCA-701PT and FCA-201-PS (Fujikura Chemical Industries, Ltd.), etc.

Examples of negatively chargeable charge control agents include metal-containing azo dyes, such as "Varifast Black 3804", "Bontron S-31", "Bontron S-32", "Bontron S-34", and "Bontron S-36" (all manufactured by Orient Chemical Industry Co., Ltd.), "Aizen Spiron Black TRH", and "T-77" (manufactured by Hodogaya Chemical Co., Ltd.); metal compounds of benzilic acid compounds, such as "LR-147" and "LR-297" (both manufactured by Nippon Carlit Co., Ltd.); metal compounds of salicylic acid compounds, such as "Bontron E-81", "Bontron E-84", "Bontron E-88", and "Bontron E-304" (all manufactured by Orient Chemical Industry Co., Ltd.), and "TN-105" (manufactured by Hodogaya Chemical Co., Ltd.); copper phthalocyanine dyes; and quaternary ammonium salts, such as "COPY CHARGE NX VP434 (Clariant), nitroimidazole derivatives, etc.; organometallic compounds, etc.

From the viewpoint of the charge stability of the toner, the content of the charge control agent in the toner is preferably 0.01% by mass or more, more preferably 0.2% by mass or more, and preferably 10% by mass or less, more preferably 5% by mass or less, even more preferably 3% by mass or less, and even more preferably 2% by mass or less.

The toner having the core-shell structure of the present invention is preferably produced by the emulsion aggregation method. When the core is formed by the suspension polymerization method, the resin is originally well dispersed, so the effect of suppressing poor regulation by the monovalent long-chain aliphatic monomer is not observed.

The method for producing the toner of the present invention by the emulsion aggregation method preferably includes, for example, the following steps 1 to 5.
Step 1-1: A step of mixing a styrene-based resin S and an organic solvent to obtain a styrene-based resin-containing liquid. Step 1-2: A step of mixing an aqueous medium with the styrene-based resin-containing liquid obtained in step 1-1 to perform phase inversion emulsification and obtain an aqueous dispersion of resin particles (X1) containing the styrene-based resin S. Step 2-1: A step of mixing a crystalline polyester resin CP, an organic solvent and a neutralizing agent to obtain a crystalline polyester resin-containing liquid. Step 2-2: A step of mixing an aqueous medium with the crystalline polyester resin-containing liquid obtained in step 2-1 to perform phase inversion emulsification and obtain an aqueous dispersion of resin particles (X2) containing the crystalline polyester resin CP. Step 3: A step of mixing the resin particles (X1) obtained in step 1-2 and the resin particles (X2) obtained in step 2-2 and aggregating them in an aqueous medium to obtain aggregated particles (1). Step 4: A step of aggregating resin particles (Y) containing a shell resin to the aggregated particles (1) obtained in step 3 to obtain aggregated particles (2). Step 5: A step of fusing the aggregated particles (2) obtained in step 4 to obtain core-shell particles.

<Step 1-1>
(Organic solvent)
From the viewpoint of solubility, preferred examples of the organic solvent include alcohol-based solvents such as isopropanol and isobutanol; ketone-based solvents such as methyl ethyl ketone, methyl isobutyl ketone and diethyl ketone; ether-based solvents such as dibutyl ether and dioxane; and acetate-based solvents such as ethyl acetate and isopropyl acetate.

(Surfactant)
In step 1-1, it is preferable to use a surfactant in order to ensure the dispersion stability of the resulting resin particles.
The surfactant may be a nonionic, anionic or cationic surfactant. Among these, from the viewpoint of emulsion stability of the resin, one or more selected from the group consisting of a nonionic surfactant and an anionic surfactant are preferred, and an anionic surfactant is more preferred.
In step 1-1, any additive may be added, such as the above-mentioned colorant, charge control agent, release agent, magnetic powder, flowability improver, conductivity adjuster, reinforcing filler such as a fibrous substance, antioxidant, antiaging agent, cleaning property improver, etc.

<Step 1-2>
In the phase inversion emulsification method, a water-based medium is added to a styrene-based resin-containing liquid, and a W/O phase is first formed, which is then inverted to an O/W phase. Whether or not the phase inversion has occurred can be confirmed, for example, by visual inspection or electrical conductivity.
The aqueous medium is a liquid containing at least water, and is preferably one containing water as the main component.
Examples of components other than water that the aqueous medium may contain include organic solvents that dissolve in water, such as methanol, ethanol, acetone, and cyclic ethers such as tetrahydrofuran.
In step 1-2, it is preferable to remove the organic solvent used in step 1-1 from the obtained aqueous dispersion. The method for removing the organic solvent is not particularly limited and any method can be used, but distillation is preferable since the organic solvent is dissolved in water.

<Step 2-1>
As the organic solvent used in step 2-1, the same organic solvent as described above in step 1-1 can be used, and the preferred embodiments thereof are also the same.

(Neutralizing agent)
Examples of the neutralizing agent used in step 2-1 include metal hydroxides such as lithium hydroxide, sodium hydroxide, and potassium hydroxide; ammonia; and organic bases such as trimethylamine, ethylamine, diethylamine, triethylamine, triethanolamine, and tributylamine.
In step 2-1, it is preferable to use a surfactant from the viewpoint of ensuring the dispersion stability of the resulting resin particles. As the surfactant used in step 2-1, the same surfactant as that described above in step 1-1 can be used, and the preferred embodiments thereof are also the same.
In step 2-1, any of the above-mentioned additives may be added.

<Step 2-2>
As the aqueous medium, the same ones as those described above in step 1-2 can be used, and the preferred embodiments thereof are also the same.
In step 2-2, it is preferable to remove the organic solvent used in step 2-1 from the obtained aqueous dispersion. The method for removing the organic solvent is not particularly limited and any method can be used, but examples thereof include the same methods as those described above in step 1-2, and the preferred embodiments thereof are also the same.

<Step 3>
In step 3, it is preferable to add a flocculant to efficiently carry out the flocculation.
The flocculant may be an organic flocculant such as a cationic surfactant of a quaternary salt, polyethyleneimine, etc., or an inorganic flocculant such as an inorganic metal salt, inorganic ammonium salt, etc. From the viewpoint of the particle size distribution of the toner obtained, an inorganic flocculant is preferred, and among them, an inorganic metal salt is preferred.
Examples of inorganic metal salts include sodium sulfate, sodium chloride, calcium chloride, calcium nitrate, barium chloride, magnesium chloride, zinc chloride, and aluminum chloride.
In step 3, the additives such as a colorant, a release agent, and a charge control agent may be added before the aggregation.

[Colorant Particle Dispersion]
The colorant is preferably added as an aqueous dispersion containing colorant particles.
For dispersing the colorant, it is preferable to use a dispersant, and a nonionic surfactant is preferable.
Examples of the nonionic surfactant include polyoxyethylene lauryl ether, polyoxyethylene stearyl ether, and polyoxyethylene oleyl ether.

From the viewpoint of obtaining a high-quality image, the volume median particle diameter ( _D50 ) of the colorant particles in the colorant particle dispersion is preferably 50 nm or more, more preferably 80 nm or more, even more preferably 100 nm or more, and is preferably 500 nm or less, more preferably 300 nm or less, even more preferably 200 nm or less.

[Release Agent Particle Dispersion]
The release agent is preferably added as an aqueous dispersion containing release agent particles.
The release agent particle dispersion liquid is obtained by dispersing the release agent in an aqueous medium, and is preferably obtained by dispersing the release agent at a temperature equal to or higher than the melting point of the release agent using a dispersing machine. Examples of the dispersing machine include a homogenizer and an ultrasonic dispersing machine.
The preferred embodiment of the aqueous medium used in the release agent particle dispersion is the same as that used in obtaining the resin particle dispersion.

For dispersing the release agent, a dispersant is preferably used, and a cationic surfactant is preferred.
Examples of the cationic surfactant include alkylbenzyldimethylammonium chloride, lauryltrimethylammonium chloride, and stearyltrimethylammonium chloride.

The volume median particle diameter (D ₅₀ ) of the release agent particles in the release agent particle dispersion is preferably 100 nm or more, more preferably 300 nm or more, and is preferably 1 μm or less, more preferably 700 nm or less.

When adding other components such as a charge control agent, it is preferable to add them as an aqueous dispersion in the same manner as the colorant particle dispersion and the release agent particle dispersion.

<Step 4>
The resin particles (Y) are preferably obtained as an aqueous dispersion of the resin particles (Y), and can be produced by using the amorphous composite resin AC as the shell resin in the same manner as in the aqueous dispersion of the resin particles (X2).
In step 4, it is preferable to add an aqueous dispersion of resin particles (Y) to the aqueous dispersion of aggregated particles (1) obtained in step 3, thereby causing the resin particles (Y) to adhere to the aggregated particles (1) to obtain a dispersion of aggregated particles (2).
In step 4, the entire amount of resin particles (Y) is added, and aggregation may be stopped when the toner particles have grown to an appropriate particle size. Methods for stopping aggregation include cooling the dispersion, adding an aggregation terminator, diluting the dispersion, etc. From the viewpoint of reliably preventing unnecessary aggregation, the method of stopping aggregation by adding an aggregation terminator is preferred.
As the aggregation terminator, a surfactant is preferably used, and an anionic surfactant is more preferably used. The aggregation terminator may be added in the form of an aqueous solution.

<Step 5>
The temperature in the system in step 5 is preferably 70° C. or higher, more preferably 75° C. or higher, and is preferably 100° C. or lower, more preferably 90° C. or lower, and even more preferably 85° C. or lower, from the viewpoints of the target toner particle size, particle size distribution, shape control, and particle fusion properties.
The core-shell particles obtained in step 5 are suitably subjected to a solid-liquid separation step such as filtration, a washing step, and a drying step, whereby the toner particles can be suitably obtained.
In the washing step, it is preferable to completely remove the added surfactant by washing.

The toner of the present invention may be surface-treated with an external additive to improve transferability. Examples of external additives include inorganic fine particles such as silica, alumina, titania, zirconia, tin oxide, and zinc oxide, and organic fine particles such as resin particles such as melamine-based resin fine particles and polytetrafluoroethylene resin fine particles, and two or more of these may be used in combination.

From the viewpoint of the chargeability, fluidity, and transferability of the toner, the average particle size of the external additive is preferably 10 nm or more, more preferably 15 nm or more, and is preferably 250 nm or less, more preferably 200 nm or less, and even more preferably 90 nm or less.

From the viewpoint of the chargeability, fluidity, and transferability of the toner, the content of the external additive is preferably 0.05 parts by mass or more, more preferably 0.1 parts by mass or more, and even more preferably 0.3 parts by mass or more, per 100 parts by mass of the toner before treatment with the external additive, and is preferably 5 parts by mass or less, and more preferably 3 parts by mass or less.

The volume median particle diameter ( _D50 ) of the toner of the present invention is preferably 3 μm or more, more preferably 4 μm or more, and preferably 15 μm or less, more preferably 10 μm or less. In this specification, the volume median particle diameter ( _D50 ) means a particle diameter at which the cumulative volume frequency calculated by volume fraction is 50% calculated from the smallest particle diameter. In addition, when the toner is treated with an external additive, the volume median particle diameter of the toner particles before treatment with the external additive is regarded as the volume median particle diameter of the toner.

From the viewpoint of fluidity, the average circularity of the toner of the present invention is preferably 0.965 or more, more preferably 0.970 or more, and is preferably 0.990 or less, more preferably 0.980 or less.

The toner of the present invention can be used as it is as a single-component developing toner, or mixed with a carrier as a two-component developing toner, in image forming devices using either a single-component developing method or a two-component developing method.

The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples. The physical properties of the resins and the like can be measured by the following methods.

[Softening point of resin]
Using a flow tester "CFT-500D" (Shimadzu Corporation), 1g of sample is heated at a temperature increase rate of 6℃/min while applying a load of 1.96MPa with the plunger, and extruding the sample from a nozzle with a diameter of 1mm and length of 1mm. The plunger descent distance of the flow tester is plotted against the temperature, and the temperature at which half of the sample flows out is taken as the softening point.

[Maximum endothermic peak temperature of resin]
Using a differential scanning calorimeter "Q-100" (manufactured by TA Instruments Japan, Inc.), 0.01 to 0.02 g of sample is weighed into an aluminum pan and cooled from room temperature (20°C) to 0°C at a rate of 10°C/min. The sample is then maintained at that temperature for 1 minute. The endothermic peak is then measured while increasing the temperature to 180°C at a rate of 10°C/min. The temperature of the endothermic peak with the largest peak area is regarded as the maximum endothermic peak temperature.

[Glass transition temperature of resin]
Using a differential scanning calorimeter "Q-100" (manufactured by TA Instruments Japan), 0.01 to 0.02 g of sample is weighed into an aluminum pan and heated from room temperature (20°C) to 200°C at a heating rate of 10°C/min, then cooled from that temperature to 0°C at a heating rate of 10°C/min. The sample is then heated to 180°C at a heating rate of 10°C/min, and the endothermic peak is measured. The glass transition temperature is the temperature at the intersection of an extension of the baseline below the maximum endothermic peak temperature and a tangent line showing the maximum slope from the rising part of the peak to the top of the peak.

[Acid value and hydroxyl value of crystalline resin]
Measure based on the method of JIS K0070:1992, except that the measurement solvent is changed from the mixed solvent of ethanol and ether specified in JIS K0070:1992 to tetrahydrofuran.

[Acid value of amorphous resin and styrene-based resin]
Measure based on the method of JIS K0070:1992, except that the measurement solvent is changed from the ethanol and ether mixture specified in JIS K0070:1992 to a mixture of acetone and toluene (acetone:toluene = 1:1 (volume ratio)).

[Melting point of release agent]
Using a differential scanning calorimeter "DSC Q-100" (manufactured by TA Instruments Japan Co., Ltd.), 0.01 to 0.02 g of sample is weighed into an aluminum pan, heated to 200°C at a heating rate of 10°C/min, and cooled from that temperature to -10°C at a heating rate of 5°C/min. The sample is then heated to 180°C at a heating rate of 10°C/min and measured. The maximum endothermic peak temperature observed from the melting endothermic curve obtained is taken as the melting point of the wax.

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

[Volume Median Particle Size (D ₅₀ ) of Resin Particles, Colorant Particles, Release Agent Particles, and Charge Control Agent Particles]
(1) Measuring device: Laser diffraction type particle size measuring device "LA-920" (manufactured by Horiba, Ltd.)
(2) Measurement conditions: Distilled water was added to the measurement cell, and the volume median particle size was measured at a concentration that brought the absorbance into an appropriate range.

[Average particle size of external additives]
The average particle size refers to the number-average particle size, and is calculated by measuring the particle sizes (average of major and minor axes) of 500 particles in a scanning electron microscope (SEM) photograph and averaging these by number.

[Volume Median Particle Size of Toner]
Measuring device: Coulter Multisizer II (manufactured by Beckman Coulter, Inc.)
Aperture diameter: 50μm
Analysis software: Coulter Multisizer AccuComp version 1.19 (Beckman Coulter, Inc.)
Electrolyte: Isoton II (Beckman Coulter, Inc.)
Dispersion solution: Emulgen 109P (Kao Corporation, polyoxyethylene lauryl ether, HLB (Griffin): 13.6) was dissolved in the electrolyte to adjust the concentration to 5% by mass. Dispersion conditions: 10 mg of a measurement sample was added to 5 mL of the dispersion solution, and the mixture was dispersed for 1 minute using an ultrasonic disperser (machine name: US-1, manufactured by SND Corporation, output: 80 W). Thereafter, 25 mL of the electrolyte solution was added, and the mixture was further dispersed for 1 minute using the ultrasonic disperser to prepare a sample dispersion solution.
Measurement conditions: The sample dispersion is added to 100 mL of the electrolyte so as to reach a concentration at which the particle sizes of 30,000 particles can be measured in 20 seconds, and 30,000 particles are measured, and the volume median particle size (D ₅₀ ) is determined from the particle size distribution.

[Average Circularity of Toner]
Measuring instrument: FPIA-3000 (Sysmex Corporation)
Standard unit (10x objective lens)
Measurement mode HPF mode version 00-10
Dispersion liquid: EMULGEN 109P (Kao Corporation, polyoxyethylene lauryl ether, HLB 13.6) 5 mass% electrolyte Dispersion conditions: 10 mg of a measurement sample was added to 10 ml of dispersion liquid, and dispersed for 1 minute using an ultrasonic disperser. Then, 10 ml of distilled water was added, and the mixture was further dispersed for 2 minutes using an ultrasonic disperser.
Measurement conditions: The circularity of the toner dispersed in the dispersion liquid is measured at 20° C. at a particle concentration of 1,800 to 2,200 particles, and the number average value is calculated.

Crystalline polyester resin production example 1
The raw material monomers shown in Table 1 were placed in a 10-liter four-neck flask equipped with a thermometer, a stainless steel stirring rod, a downflow condenser, and a nitrogen inlet tube, and the temperature was raised from 130°C to 200°C over 8 hours in a nitrogen atmosphere in a mantle heater, and then the reaction was carried out at 200°C for 2 hours. An esterification catalyst was then added, and the reaction was carried out under a reduced pressure of 8 kPa until the desired softening point was reached, thereby obtaining crystalline polyester resins (resins C1 to C10).

Amorphous Resin Production Example 1
2 liters of xylene was placed in a 10 liter four-neck flask equipped with a thermometer, a stainless steel stirring rod, a flow-down condenser, a dropping funnel and a nitrogen inlet tube, and the raw material monomers and radical polymerization initiator of the styrene resin shown in Table 2 were placed in the dropping funnel equipped on the four-neck flask. Then, the xylene in the four-neck flask was heated to 135°C under a nitrogen atmosphere, and the mixture of the raw material monomers and the radical polymerization initiator was dropped into the xylene from the dropping funnel over 1 hour. The temperature was further raised to 200°C and maintained at 200°C for 2 hours. Then, the xylene was removed by maintaining it under a reduced pressure of 8 kPa for 1 hour, to obtain an amorphous styrene resin (resin A1).

Amorphous Resin Production Example 2
BPA-PO, BPA-EO, terephthalic acid, esterification catalyst and esterification promoter shown in Table 3 were placed in a 10-liter four-neck flask equipped with a thermometer, a stainless steel stirring rod, a downflow condenser and a nitrogen inlet tube, and the temperature was raised to 235°C over 2 hours in a mantle heater in a nitrogen atmosphere. After that, it was confirmed that the reaction rate reached 95% or more at 235°C, and the mixture was cooled to 180°C. Adipic acid was then added, and the mixture was heated to 210°C over 2 hours. After that, the mixture was reacted at 210°C for 1 hour, and then reacted at 40 kPa until the softening point shown in Table 3 was reached, to obtain an amorphous polyester resin (resin A2). The reaction rate in the present invention refers to the value of the amount of water produced by reaction (mol)/theoretical amount of water produced (mol) x 100.

Amorphous Resin Production Example 3
Among the raw material monomers of the polyester resin shown in Table 3, raw material monomers other than succinic acid, an esterification catalyst and an esterification promoter were placed in a 10-liter four-neck flask equipped with a thermometer, a stainless steel stirring rod, a downflow condenser and a nitrogen inlet tube, and the temperature was raised to 235°C over 2 hours in a mantle heater in a nitrogen atmosphere. After confirming that the reaction rate reached 90% or more at 235°C, the mixture was cooled to 160°C and a mixed solution of raw material monomers of the styrene resin shown in Table 3, both reactive monomers and radical polymerization initiator was dropped over 1 hour. After keeping at 160°C for 30 minutes, the mixture was heated to 200°C, reacted for 1 hour under a reduced pressure of 8 kPa, and then cooled to 180°C. Then, succinic acid was added and the mixture was heated to 210°C over 2 hours. After reacting at 210°C for 1 hour, the mixture was reacted under a reduced pressure of 40 kPa until the desired softening point was obtained, and an amorphous resin (resin A3) was obtained.

Production Example 1 of Resin Particle Dispersion
In a 3-liter vessel equipped with a stirrer, reflux condenser, dropping funnel, thermometer, and nitrogen inlet tube, 100 g of the resin shown in Table 4, 100 g of methyl ethyl ketone, and 16.7 g (4.5% by mass relative to 100 g of resin) of an anionic surfactant "EMAL E27C" (Kao Corporation) were placed and dissolved at 73° C. for 2 hours. A 5% by mass aqueous solution of sodium hydroxide was added to the resulting solution so that the degree of neutralization was 70 mol% relative to the acid value of the resin, and the mixture was stirred for 30 minutes.
While maintaining the temperature at 73°C, 475 g of ion-exchanged water was added over 77 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, and water was further distilled off until the desired resin content was reached. Thereafter, the aqueous dispersion was cooled to 30°C while stirring at 280 r/min (circumferential speed 88 m/min) to obtain aqueous dispersions (resin particle dispersions C1 to C10, A2, A3) (resin content 17% by mass) in which resin particles were dispersed in an aqueous medium.

Production Example 2 of Resin Particle Dispersion
100g of resin A1, 100g of methyl ethyl ketone, and 16.7g of anionic surfactant "EMAL E27C" (Kao Corporation) (4.5% by mass relative to 100g of resin) were mixed at 25°C and dissolved at 73°C for 2 hours. 600g of ion-exchanged water at 73°C was mixed with the resulting solution, and the mixture was dispersed for 30 minutes at 350W using an ultrasonic homogenizer (Dr. Hielscher, product name: "UP-400S"). Then, methyl ethyl ketone was distilled off under reduced pressure at 70°C to obtain an aqueous dispersion of resin particles (resin particle dispersion a1) (resin content 14% by mass).

Production Example of Colorant Dispersion 50 g of copper phthalocyanine "ECB-301" (manufactured by Dainichiseika Color & Chemicals Mfg. Co., Ltd.), 5 g of nonionic surfactant "EMULGEN 150" (polyoxyethylene lauryl ether, manufactured by Kao Corporation) and 200 g of ion-exchanged water were mixed and dispersed for 10 minutes using a homogenizer to obtain a colorant dispersion containing colorant fine particles. The volume median particle diameter ( _D50 ) of the colorant fine particles was 120 nm and the solid content was 22 mass%.

Production Example of Release Agent Dispersion 50 g of paraffin wax "HNP9" (manufactured by Nippon Seiro Co., Ltd., melting point: 79°C), 5 g of cationic surfactant "Sanisol (registered trademark) B50" (manufactured by Kao Corporation, alkylbenzyldimethylammonium chloride) and 200 g of ion-exchanged water were heated to 95°C and dispersed for 30 minutes using an ultrasonic homogenizer (manufactured by Dr. Hielcher Co., Ltd., product name: "UP-400S") at an output of 350 W to obtain a release agent dispersion containing release agent particles. The volume median particle diameter ( _D50 ) of the paraffin wax (release agent particles) was 550 nm and the solid content was 22 mass%.

Production example of charge control agent dispersion 50g of salicylic acid compound "Bontron E-84" (manufactured by Orient Chemical Industry Co., Ltd.) as charge control agent, 5g of "Emulgen 150" (manufactured by Kao Corporation) as nonionic surfactant, and 200g of ion-exchanged water were mixed, and dispersed for 10 minutes using glass beads and a sand grinder to obtain a charge control agent dispersion containing charge control agent fine particles. The volume median particle diameter ( _D50 ) of the charge control agent fine particles was 400nm, and the solid content was 22% by mass.

Examples 1 to 9 and Comparative Examples 1 and 2
45g of the resin particle dispersion of the crystalline resin for core shown in Table 5, 210g of the resin particle dispersion of the amorphous resin for core, 8g of the colorant dispersion, 20g of the release agent dispersion, 2g of the charge control agent dispersion, and 52g of deionized water were placed in a 2-liter container, and 150g of a 0.1% by mass calcium chloride aqueous solution at 20°C was dropped over 30 minutes while stirring with an anchor-type stirrer at 100r/min (circumferential speed 31m/min), and the temperature was raised to 50°C while stirring. After maintaining at 50°C until the volume median particle diameter ( _D50 ) reached 5μm, 45g of resin dispersion a3 was immediately added and dispersed by stirring. Then, a dilution solution obtained by diluting 4.2g of anionic surfactant "EMAL E27C" (manufactured by Kao Corporation, solid content 27% by mass) with 37g of deionized water was added as an aggregation stopper. The temperature was then raised to 80° C., and once it reached 80° C., it was maintained at 80° C. for 1 hour, after which the heating was terminated. In this way, fused particles were formed, which were then gradually cooled to 20° C., filtered through a 150 mesh (150 μm opening) wire screen, suction filtered, washed, and dried to obtain toner particles having the volume median particle size (D ₅₀ ) and average circularity shown in Table 5.

For 100 parts by mass of the obtained toner particles, 1.0 part by mass of hydrophobic silica "NAX-50" (manufactured by Nippon Aerosil Co., Ltd., average particle size 40 nm), 0.6 part by mass of hydrophobic silica "R972" (manufactured by Nippon Aerosil Co., Ltd., average particle size 16 nm), and 0.5 part by mass of titanium oxide "JMT-150IB" (manufactured by Teika Co., Ltd., average particle size 15 nm) were added to a 10-liter Henschel mixer (manufactured by Nippon Coke and Engineering Co., Ltd.) equipped with ST and A0 stirring blades, and the mixture was stirred at 3000 rpm for 2 minutes to obtain a toner.

Comparative Example 3
To a 1-liter glass beaker, 150 g of ion-exchanged water, 500 g of a 10 mass% slurry of calcium phosphate tribasic (3[ _Ca3 ( _PO4 ) ₂ ].Ca(OH) ₂ ) "TCP-10.U" (manufactured by Matsuo Pharmaceutical Industry Co., Ltd.), and 0.004 g of the anionic surfactant "Neopelex G-15" (manufactured by Kao Corporation, sodium dodecylbenzenesulfonate) were added and stirred to prepare an aqueous medium (surfactant concentration: 1.1 x ^10-5 M).

In a 300 mL glass beaker, 10 g of resin C1, 10 g of resin A2, 64 g of styrene and 16 g of n-butyl acrylate as raw monomers for styrene-based resins, 5 g of copper phthalocyanine "ECB-301" (manufactured by Dainichiseika Color & Chemicals Co., Ltd.) as a coloring agent, 1 g of salicylic acid compound "Bontron E-84" (manufactured by Orient Chemical Industry Co., Ltd.) as a charge control agent, and 15 g of paraffin wax "HNP9" (manufactured by Nippon Seiro Co., Ltd.) as a release agent were mixed with stirring and heated to 60°C to dissolve uniformly. Then, 4 g of polymerization initiator "V-65" (manufactured by Wako Pure Chemical Industries, Ltd., 2,2'-azobis(2,4-dimethylvaleronitrile), 10-hour half-life temperature: 51°C) was added to prepare a resin solution.

The aqueous medium was heated to 60°C, and while maintaining the temperature at 60°C, the resin solution was added all at once. The mixture was stirred at 12,000 rpm for 4 minutes using a homomixer MARKII 2.5 (Primix Corporation) to obtain a suspension.

The suspension was transferred to a separable flask and polymerized for 7 hours at 70°C while stirring at 200 rpm. The temperature was then raised to 80°C, and the remaining monomers were distilled off under reduced pressure. The mixture was cooled to 20°C while continuing to stir, and hydrochloric acid was added until the pH of the system was 1 or less. After washing and drying, toner particles were obtained.

For 100 parts by mass of the obtained toner particles, 1.0 part by mass of hydrophobic silica "NAX-50" (manufactured by Nippon Aerosil Co., Ltd., average particle size 40 nm), 0.6 part by mass of hydrophobic silica "R972" (manufactured by Nippon Aerosil Co., Ltd., average particle size 16 nm), and 0.5 part by mass of titanium oxide "JMT-150IB" (manufactured by Teika Co., Ltd., average particle size 15 nm) were added to a 10-liter Henschel mixer (manufactured by Nippon Coke and Engineering Co., Ltd.) equipped with ST and A0 stirring blades, and the mixture was stirred at 3000 rpm for 2 minutes to obtain a toner.

Test example [Regulation failure suppression]
Using a commercially available printer "Microline (registered trademark) 5400" (manufactured by OKI Data Corporation), 20,000 sheets of images with a print rate of 1% were printed on high-quality paper "J paper A4 size" (manufactured by Fuji Xerox Co., Ltd.). Then, one halftone image was printed. The amount of spot-like streaks and toner clumps that appeared on the obtained halftone image was visually observed, and the degree of occurrence of regulation failure was evaluated according to the following evaluation criteria. The results are shown in Table 5.

[Evaluation criteria for streaks]
A: Not observed B: There are some spot-like streaks on the edge.
C: Spot-like streaks are present over the entire surface.

[Evaluation Criteria for Toner Agglomerates]
A: Not occurred B: There are small toner clumps in two or three places.
C: There are small toner clumps in 4 or 5 places.
D: Small or obvious toner clumps are present in 6 or more places.

From the above results, it is understood that in Examples 1 to 9, the circularity of the toner is high, and the occurrence of regulation failure is suppressed.
In contrast, in Comparative Example 1, which contains a crystalline polyester resin not using a monovalent long-chain aliphatic monomer, and Comparative Example 2, which uses an amorphous polyester resin without a styrene-based resin in the core, the toner has a low circularity and poor regulation. Also, in the toner of Comparative Example 3, which is produced by suspension polymerization and does not have a core-shell structure, the crystalline polyester resin is easily exposed due to the absence of a shell, so the toner has a low circularity and poor regulation.

The toner for developing electrostatic images of the present invention is suitable for use in developing latent images formed in electrostatic image developing methods, electrostatic recording methods, electrostatic printing methods, etc.

Claims (3)

The toner for developing electrostatic images has a core-shell structure, the core comprising a crystalline polyester resin CP which is a polycondensation product of a styrene-based resin S and an alcohol component and a carboxylic acid component, the alcohol component of the crystalline polyester resin CP containing from 2 mol % to 60 mol % of an aliphatic monoalcohol having from 10 to 30 carbon atoms and/or the carboxylic acid component containing from 2 mol % to 60 mol % of an aliphatic monocarboxylic acid compound having from 10 to 30 carbon atoms, and the shell comprising an amorphous composite resin AC in which a polyester resin ACP obtained by polycondensing raw material monomers composed of an alcohol component and a carboxylic acid component containing succinic acid is bonded to a styrene-based resin ACS obtained by addition polymerization of a raw material monomer containing a styrene compound. The toner for developing electrostatic images according to claim 1, wherein the carboxylic acid component of the crystalline polyester resin CP contains 40 mol % or more of a linear aliphatic dicarboxylic acid compound having 10 to 16 carbon atoms. 3. The toner for electrostatic charge development according to claim 1, which is obtained by an emulsion aggregation method.