JP7595798B2 - Toner for developing electrostatic images - Google Patents

Description

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

Toner containing polyester resin using highly reactive polyethylene terephthalate as a binder resin is being considered.

Patent Document 1 discloses a toner for developing electrostatic images, which comprises a binder resin and a colorant, and the binder resin comprises two types of resins with softening points differing by 10°C or more, and the resin with the lower softening point is a polyester obtained by reacting polyethylene terephthalate or modified polyethylene terephthalate with an alcohol component and a carboxylic acid component, or a hybrid resin having the polyester as one of the resin components.

JP 2004-280085 A

On the other hand, quaternary ammonium salt compounds have high positive charging properties, but have issues with charging stability.

The present invention relates to a toner for developing electrostatic images that has excellent charging stability.

The present invention relates to a toner for developing electrostatic images that contains an amorphous polyester resin A and a quaternary ammonium salt compound X, in which the amorphous polyester resin A is a polycondensate of an alcohol component, a carboxylic acid component, and polyethylene terephthalate, and the content of the quaternary ammonium salt compound X is 3 parts by mass or more and 30 parts by mass or less per 100 parts by mass of the amorphous polyester resin A.

The toner for developing electrostatic images of the present invention exhibits excellent effects in terms of charge stability.

The toner for developing electrostatic images of the present invention is characterized in that it contains amorphous polyester resin A, which is a polycondensation product of an alcohol component, a carboxylic acid component, and polyethylene terephthalate (PET), and a quaternary ammonium salt compound X. The reason why the toner for developing electrostatic images of the present invention has excellent charge stability is unclear, but is presumed to be as follows.

Because quaternary ammonium salt compounds are in a cationic state, they are incompatible with amorphous polyester resins, making them difficult to disperse in the amorphous polyester resin, and they pose problems with charge stability. In response to this, the present invention has found that the charge stability of the toner is improved by using a polycondensate (amorphous polyester resin A) of an alcohol component, a carboxylic acid component, and PET. This is because the ester group sandwiching the PET-derived ethylene glycol portion of amorphous polyester resin A is likely to interact with the quaternary ammonium salt compound, which is a cationic site, and in the polycondensation reaction of the alcohol component, the carboxylic acid component, and polyethylene phthalate, PET is incorporated into the polyester resin chain by an ester exchange reaction while undergoing depolymerization, but is not completely randomized, and exists in the amorphous polyester resin A as a unit of a certain length that can be called a polyethylene terephthalate component, so that the interaction with the quaternary ammonium salt compound is further increased, improving the dispersibility of the quaternary ammonium salt compound in the amorphous polyester resin, which is presumably resulting in a reduction in the conductive path and improved charge stability.

Amorphous polyester resin A is a polycondensation product of an alcohol component, a carboxylic acid component, and PET.

From the viewpoint of low-temperature fixability, the alcohol component is represented by formula (I):

(wherein ^OR1 and ^R1O are oxyalkylene groups, ^R1 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.)
Examples of the alkylene oxide adduct of bisphenol A represented by formula (I) include a polyoxypropylene adduct of 2,2-bis(4-hydroxyphenyl)propane, a polyoxyethylene adduct of 2,2-bis(4-hydroxyphenyl)propane, etc. It is preferable to use one or more of these.

The content of the alkylene oxide adduct of bisphenol A represented by formula (I) in the alcohol component is preferably 80 mol% or more, 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, trihydric or higher alcohols, etc.

Examples of aliphatic diols include ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,4-butenediol, 1,3-butanediol, and neopentyl glycol.

Examples of trihydric or higher alcohols include glycerin, trimethylolpropane, and pentaerythritol.

From the viewpoint of charging stability, it is preferable that the carboxylic acid component contains an aromatic dicarboxylic acid compound.

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 mol% or more, more preferably 70 mol% or more, and even more preferably 80 mol% or more. The carboxylic acid component also includes the terephthalic acid units contained in PET.

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

Aliphatic dicarboxylic acid compounds include fumaric acid, maleic acid, succinic acid, succinic acid derivatives substituted with a hydrocarbon group, glutaric acid, adipic acid, sebacic acid, anhydrides of these acids, and alkyl esters of these acids having 1 to 3 carbon atoms.

Specific examples of succinic acid derivatives substituted with a hydrocarbon group include dodecylsuccinic acid, dodecenylsuccinic acid, tetrapropenylsuccinic acid, decenylsuccinic acid, their acid anhydrides, and their alkyl esters having 1 to 3 carbon atoms. Among these, from the viewpoint of low-temperature fixability, dodecenylsuccinic acid, tetrapropenylsuccinic acid, or their acid anhydrides are preferred, and dodecenylsuccinic anhydride is more preferred.

From the viewpoint of hydrophobicity, the number of carbon atoms in the hydrocarbon group in the succinic acid derivative is preferably 8 or more, more preferably 10 or more, even more preferably 12 or more, and is preferably 20 or less, more preferably 18 or less, even more preferably 16 or less.

Examples of trivalent or higher carboxylic acid compounds include 1,2,4-benzenetricarboxylic acid (trimellitic acid), 2,5,7-naphthalenetricarboxylic acid, pyromellitic acid, anhydrides of these acids, and alkyl esters in which the alkyl group has 1 to 3 carbon atoms, and among these, trimellitic acid compounds are preferred.

The raw material monomer may contain trivalent or higher monomers (trivalent or higher alcohols and/or trivalent or higher carboxylic acid compounds) from the viewpoint of adjusting the softening point.

The content of trivalent or higher monomers is preferably 1 mol% or more, more preferably 3 mol% or more, and preferably 20 mol% or less, more preferably 15 mol% or less, of the total amount of the alcohol component and the carboxylic acid component. The alcohol component and the carboxylic acid component also include the ethylene glycol unit and the terephthalic acid unit contained in PET.

The alcohol component may appropriately contain a monohydric alcohol, and the carboxylic acid component may appropriately contain a monovalent carboxylic acid compound.

In addition, in this specification, macromonomers and hydroxycarboxylic acids are not included in the alcohol component and carboxylic acid component.

PET is produced by polycondensation of an alcohol component with a carboxylic acid component, and/or by depolymerization of a portion of PET. The ethylene glycol and terephthalic acid produced are then used as raw monomers in a polycondensation reaction and incorporated into polyester resin. PET is an equimolar polycondensation product of ethylene glycol and terephthalic acid, and the ethylene glycol and terephthalic acid that make up PET are regarded as the alcohol component and the carboxylic acid component, respectively.

The PET may be new virgin PET or recycled PET.
Recycled PET is made by collecting used PET, washing it as necessary and separating it from other materials, then crushing it, and depolymerizing the crushed material down to its monomer units, which are then used to resynthesize new PET.

In the present invention, the PET is preferably a PET having a relatively low IV value, i.e., a low molecular weight, compared to conventionally used PET. By introducing a PET having a low IV value (low molecular weight) into the polyester resin, the depolymerization of the PET proceeds more uniformly.

From the above viewpoints, the IV value of PET is preferably 0.40 or more, more preferably 0.45 or more, even more preferably 0.50 or more, and even more preferably 0.55 or more, and from the viewpoints of low-temperature fixability and uniform depolymerization, it is preferably 0.85 or less, more preferably 0.80 or less, even more preferably 0.75 or less, even more preferably 0.70 or less, and even more preferably 0.65 or less. The IV value is the intrinsic viscosity and is an index of molecular weight. The IV value of PET can be adjusted by the polycondensation time, etc.

Commercially available PET products with an IV value of 0.40 to 0.85 include RAMAPET L1 (Indorama Ventures, IV value: 0.60), RAMAPET BF3067 (Indorama Ventures, IV value: 0.65), RAMAPET N2G (Indorama Ventures, IV value: 0.75), TRN-NTJ (Teijin Limited, IV value: 0.53), TRN-RTJC (Teijin Limited, IV value: 0.64), RAMAPET S1 (Indorama Ventures, IV value: 0.84), and UK-31 (Utsumi Recycle Systems, IV value: 0.67).

The content of low IV PET is preferably 90% by mass or more, more preferably 95% by mass or more, even more preferably 98% by mass or more, and even more preferably 100% by mass, of the total amount of PET used in polycondensation.

The PET content is preferably 5 mol % or more, more preferably 10 mol % or more, and even more preferably 20 mol % or more, and is preferably 75 mol % or less, more preferably 50 mol % or less, and even more preferably 40 mol % or less, in the total amount of the alcohol component, the carboxylic acid component, and the PET, from the viewpoint of fixability. When the amorphous polyester resin A is composed of two or more resins, the weighted average of the PET contents of the respective resins is defined as the PET content of the amorphous polyester resin A.
In addition, since PET is an equimolar polycondensation product of ethylene glycol, terephthalic acid, dimethyl terephthalate, etc., the terephthalic acid-ethylene glycol unit (Mw: 192) is calculated as 1 mole. Therefore, the number of moles of PET = the number of moles of ethylene glycol units = the number of moles of terephthalic acid units.

The equivalent ratio (COOH groups/OH groups) of the carboxylic acid component (including the terephthalic acid units in PET) to the alcohol component (including the ethylene glycol units in PET) is preferably 0.6 or more, more preferably 0.7 or more, even more preferably 0.75 or more, and is preferably 1.2 or less, more preferably 1.15 or less.

Amorphous polyester resin A can be produced, 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 160°C or higher, more preferably 200°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 diisopropoxybis(triethanolaminate) and titanium dihydroxybis(triethanolaminate). 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, based on 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, based on 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 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.

In the present invention, the polyester resin may be modified to such an extent that its properties are not substantially impaired. Examples of modified polyester resins include polyester resins grafted or blocked with phenol, urethane, epoxy, or the like, by the methods described in JP-A-11-133668, JP-A-10-239903, JP-A-8-20636, and the like. Among the modified polyester resins, urethane-modified polyester resins in which polyester resins are urethane-extended with a polyisocyanate compound are preferred.

From the viewpoint of charging stability, 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 low-temperature fixability, it is preferably 170°C or lower, more preferably 160°C or lower, and even more preferably 150°C or lower.

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, that is, the value of [softening point/maximum endothermic peak temperature].
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.
On the other hand, the 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.
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.

From the viewpoint of low-temperature fixing property and fixing width, the amorphous polyester resin A may be composed of resins with different softening points. The difference in the softening points of the two types of resins is preferably 10°C or more, more preferably 20°C or more, and is preferably 60°C or less, more preferably 40°C or less.

The softening point of the amorphous resin with the higher softening point (resin AH) is preferably 100°C or higher, more preferably 110°C or higher, and even more preferably 120°C or higher, from the viewpoint of fixing width, and is preferably 170°C or lower, more preferably 160°C or lower, and even more preferably 150°C or lower, from the viewpoint of low-temperature fixing ability.

The softening point of the amorphous resin with the lower softening point (resin AL) is preferably 70°C or higher, more preferably 90°C or higher, and even more preferably 100°C or higher, from the viewpoint of charging stability, and is preferably 130°C or lower, more preferably 125°C or lower, and even more preferably 120°C or lower, from the viewpoint of low-temperature fixing ability.

The mass ratio of resin AH to resin AL (resin AH/resin AL) is preferably 10/90 or more, more preferably 20/80 or more, even more preferably 30/70 or more, and is preferably 90/10 or less, more preferably 80/20 or less, even more preferably 75/25 or less.

From the viewpoint of charge stability, the glass transition temperature of the amorphous polyester resin A is preferably 40°C or higher, more preferably 50°C or higher, and from the viewpoint of low-temperature fixability, it is preferably 80°C or lower, more preferably 70°C or lower.

From the viewpoint of low-temperature fixing ability, the acid value of the amorphous polyester resin A is preferably 1 mgKOH/g or more, more preferably 3 mgKOH/g or more, and from the viewpoint of charging stability, it is preferably 20 mgKOH/g or less, more preferably 18 mgKOH/g or less.

In the toner, amorphous polyester resin A is contained as a binder resin.

The content of amorphous polyester resin A in the binder resin is preferably 70% 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 even more preferably 100% by mass.

The content of the binder resin in the toner is preferably 60% by mass or more, more preferably 70% by mass or more, and even more preferably 80% by mass or more, and is preferably less than 100% by mass, more preferably 98% by mass or less, and even more preferably 95% by mass or less.

As the quaternary ammonium salt compound X, from the viewpoint of charging stability, a quaternary ammonium salt-containing resin, which is a polymeric quaternary ammonium salt compound, is preferred, and a quaternary ammonium salt-containing styrene-based resin is more preferred.

The quaternary ammonium salt-containing styrene-based resin is not particularly limited, but is preferably, for example, a copolymer of a styrene monomer (M1) and/or an (meth)acrylic acid alkyl ester monomer (M2) and a quaternary ammonium salt of a dialkylaminoalkyl (meth)acrylate monomer (M3).

The styrene monomer (M1) is styrene and does not include styrene derivatives such as α-methylstyrene, p-methylstyrene, and p-chlorostyrene.

Examples of (meth)acrylic acid alkyl ester monomers (M2) include methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, propyl (meth)acrylate, amyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, cyclohexyl (meth)acrylate, lauryl (meth)acrylate, and stearyl (meth)acrylate. The alkyl group preferably has 4 to 12 carbon atoms. Among these, butyl (meth)acrylate or 2-ethylhexyl (meth)acrylate is preferred, with butyl (meth)acrylate being more preferred, and butyl (meth)acrylate being more preferred.

The quaternary ammonium salt (M3) of a dialkylaminoalkyl (meth)acrylate monomer is represented by the formula (II):

(In the formula, ^R2 is a hydrogen atom or a methyl group, ^R3 is an alkylene group having 1 to 5 carbon atoms, and ^R4 to ^R6 each independently represent an alkyl group having 1 to 5 carbon atoms.)
Preferred is a compound represented by the following formula:

In formula (II), ^R2 is preferably a methyl group. ^R3 includes a methylene group, an ethylene group, a propylene group, a butylene group, etc., of which an ethylene group is preferred. ^R4 to ^R6 include a methyl group, an ethyl group, a propyl group, an n-butyl group, a tert-butyl group, etc., of which a methyl group or an ethyl group is preferred.

Examples of dialkylaminoalkyl (meth)acrylates include dimethylaminoethyl (meth)acrylate, diethylaminoethyl (meth)acrylate, dipropylaminoethyl (meth)acrylate, dibutylaminoethyl (meth)acrylate, etc., and among these, diethylaminoethyl (meth)acrylate is preferred because it is inexpensive.

A method for producing a styrene-based resin containing a quaternary ammonium salt includes, for example, quaternizing a dialkylaminoalkyl (meth)acrylate using an alkyl paratoluenesulfonate ester in a conventional manner to obtain a quaternary ammonium salt of a dialkylaminoalkyl (meth)acrylate monomer (M3), mixing this with a styrene monomer (M1) and/or an alkyl (meth)acrylate monomer (M2), and copolymerizing the mixture in the presence of a polymerization initiator.

Examples of alkyl esters of paratoluenesulfonic acid include methyl paratoluenesulfonate, ethyl paratoluenesulfonate, and propyl paratoluenesulfonate. Of these, methyl paratoluenesulfonate is preferred because it is easy to quaternize.

The amount of paratoluenesulfonic acid alkyl ester used is preferably 0.8 moles or more, more preferably 1 mole or more, and preferably 1.5 moles or less, more preferably 1.2 moles or less, per mole of dialkylaminoalkyl(meth)acrylate to be reacted with it.

As the copolymerization method, any method such as solution polymerization, suspension polymerization, bulk polymerization, emulsion polymerization, etc. may be used, but solution polymerization is preferred because it is relatively easy to control the molecular weight of the resulting copolymer and the reaction operation is easy.

Solvents used in solution polymerization include ketone-based solvents such as methyl ethyl ketone and methyl isobutyl ketone, alcohol-based solvents such as normal butanol and isobutanol, ester-based solvents such as ethyl acetate and isobutyl acetate, and aromatic hydrocarbon solvents such as toluene and xylene. Of these, ketone-based solvents and alcohol-based solvents are preferred from the viewpoint of the solubility of the copolymer.

Polymerization initiators that can be used include peroxide initiators such as tert-butylperoxy-2-ethylhexanoate, tert-amylperoxy-2-ethylhexanoate, 1,1-di(tert-butylperoxy)cyclohexane, and dibenzoyl peroxide, and azo initiators such as 2,2'-azobis(2-methylbutyronitrile).

The amount of polymerization initiator used is preferably 0.5 parts by mass or more and 10 parts by mass or less per 100 parts by mass of the total monomers.

In the quaternary ammonium salt-containing styrene-based resin, the content of styrene monomer (M1) units in the total amount of styrene monomer (M1) units, (meth)acrylic acid alkyl ester monomer (M2) units, and dialkylaminoalkyl (meth)acrylate quaternary ammonium salt (M3) units is preferably 40% by mass or more, more preferably 50% by mass or more, and preferably 80% by mass or less, more preferably 75% by mass or less.

In the quaternary ammonium salt-containing styrene-based resin, the content of (meth)acrylic acid alkyl ester monomer (M2) units in the total amount of styrene monomer (M1) units, (meth)acrylic acid alkyl ester monomer (M2) units, and dialkylaminoalkyl (meth)acrylate quaternary ammonium salt (M3) units is preferably 5% by mass or more, more preferably 10% by mass or more, and is preferably 40% by mass or less, more preferably 35% by mass or less.

In the quaternary ammonium salt-containing styrene-based resin, the content of the quaternary ammonium salt (M3) units of dialkylaminoalkyl (meth)acrylate in the total amount of the styrene monomer (M1) units, the (meth)acrylic acid alkyl ester monomer (M2) units, and the quaternary ammonium salt (M3) units of dialkylaminoalkyl (meth)acrylate is preferably 0.5% by mass or more, more preferably 1% by mass or more, and is preferably 35% by mass or less, more preferably 30% by mass or less.

Commercially available styrene-based resins containing quaternary ammonium bases include, for example, "FCA-201-PS" and "FCA-701-PT" (both manufactured by Fujikura Kasei Co., Ltd.).

The softening point of the quaternary ammonium salt-containing styrene resin is preferably 140°C or lower, more preferably 135°C or lower, and even more preferably 130°C or lower, from the viewpoint of improving the grindability of the toner to obtain small toner particles and from the viewpoint of low-temperature fixability, and is preferably 90°C or higher, more preferably 95°C or higher, and even more preferably 100°C or higher, from the viewpoint of storage stability.

The glass transition temperature of the quaternary ammonium salt-containing styrene resin is preferably 90°C or lower, more preferably 85°C or lower, and even more preferably 80°C or lower, from the viewpoint of improving the grindability of the toner to obtain small toner particles and from the viewpoint of low-temperature fixability, and is preferably 35°C or higher, more preferably 40°C or higher, and even more preferably 45°C or higher, from the viewpoint of storage stability.

Other quaternary ammonium salt compounds X include, for example, compounds represented by formula (III):

(In the formula, R ⁷ to R ⁹ each independently represent an alkyl group having 1 to 5 carbon atoms, and R ¹⁰ represents an alkylene group having 1 to 5 carbon atoms.)
An example of a commercially available product of the quaternary ammonium salt compound represented by formula (III) is "Bontron P-51" (manufactured by Orient Chemical Industries, Ltd., R ⁷ to R ⁹ are butyl groups, R ¹⁰ is a methylene group).

The content of the quaternary ammonium salt compound X is 3 parts by mass or more, preferably 5 parts by mass or more, more preferably 8 parts by mass or more, based on 100 parts by mass of the amorphous polyester resin A, from the viewpoint of charging stability, and is 30 parts by mass or less, preferably 25 parts by mass or less, more preferably 20 parts by mass or less, based on the viewpoint of dispersibility in the binder resin.

The toner of the present invention may contain other charge control agents as long as the effects of the present invention are not impaired.

In addition to the binder resin and the quaternary ammonium salt compound X, the toner of the present invention may contain additives such as colorants, release agents, charge control agents, magnetic powders, flowability improvers, conductivity adjusters, reinforcing fillers such as fibrous substances, antioxidants, and cleaning improvers.

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 is preferably 1 part by mass or more, more preferably 2 parts by mass or more, and preferably 40 parts by mass or less, more preferably 20 parts by mass or less, and even more preferably 10 parts by mass or less, per 100 parts by mass of the binder resin.

Examples of release agents include hydrocarbon waxes such as polypropylene wax, polyethylene wax, ethylene propylene copolymer wax, microcrystalline wax, paraffin wax, and Fischer-Tropsch wax, and oxides thereof; ester waxes such as carnauba wax, montan wax, and deoxidized 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.

From the viewpoint of charge stability, the melting point of the release agent is preferably 60°C or higher, more preferably 70°C or higher, and from the viewpoint of low-temperature fixability, it 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.

The content of the release agent is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, and even more preferably 1.5 parts by mass or more, relative to 100 parts by mass of the binder resin, from the viewpoints of the low-temperature fixing property and charging stability of the toner and dispersibility in the binder resin, and is preferably 10 parts by mass or less, more preferably 8 parts by mass or less, and even more preferably 7 parts by mass or less.

The toner may be obtained by any of the conventionally known methods such as the melt kneading method, emulsion aggregation method, suspension polymerization method, etc., and may also be a toner having a core-shell structure, but from the viewpoint of charge stability, pulverized toner by the melt kneading method is preferred. In the case of pulverized toner by the melt kneading method, for example, raw materials such as a binder resin containing amorphous polyester resin A, a quaternary ammonium salt compound X, and, if necessary, a colorant, a release agent, and a charge control agent are uniformly mixed in a mixer such as a Henschel mixer, and then melt-kneaded in an internal kneader, a single-screw or twin-screw extruder, an open roll type kneader, etc., and cooled, pulverized, and classified to produce the toner.

In order to improve the transferability of the toner of the present invention, it is preferable to use an external additive. 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 melamine-based resin fine particles and polytetrafluoroethylene resin fine particles, and two or more types may be used in combination. Of these, silica is preferred, and from the viewpoint of the transferability of the toner, hydrophobic silica that has been hydrophobized is more preferred.

Examples of hydrophobic treatment agents for hydrophobizing the surface of silica particles include hexamethyldisilazane (HMDS), dimethyldichlorosilane (DMDS), cyclic silazane, silicone oil, aminosilane, octyltriethoxysilane (OTES), methyltriethoxysilane, etc.

From the viewpoint of the chargeability, fluidity, and transferability of the toner, the average particle diameter of the external additive is preferably 5 nm or more, more preferably 10 nm or more, and even 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.

The external addition process by mixing the toner particles with the external additives can be carried out according to conventional methods, and a mixer such as a Henschel mixer can be used.

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, relative to 100 parts by mass of the toner particles 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 the treatment with the external additive is taken as the volume median particle diameter of the toner.

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.

[PET IV value]
The viscosity is calculated from the following formula: A solution of the viscoelasticity at a concentration of 4 g/L is dissolved in a mixed solvent of phenol/tetrachloroethane (mass ratio) of 60/40, and the viscosity is measured using an Ubbelohde viscometer.
IV=(-1+√(1+4kη))/(2kC)
(wherein k=0.33, C=0.004 g/mL, and η=(t ₁ /t ₀ )−1 (t ₀ : number of seconds it takes for the solvent alone to fall, t ₁ : number of seconds it takes for the sample solution to fall).)

[Softening point of resin]
Using a flow tester "CFT-500D" (manufactured by Shimadzu Corporation), 1 g of the sample is heated at a temperature increase rate of 6°C/min while applying a load of 1.96 MPa with the plunger, and extruded from a nozzle with a diameter of 1 mm and a length of 1 mm. The plunger descent amount 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 a sample is weighed into an aluminum pan and cooled from room temperature (25°C) to 0°C at a temperature drop rate of 10°C/min, and maintained at 0°C for 1 minute. Thereafter, measurements are performed at a temperature increase rate of 10°C/min. The temperature of the peak with the largest peak area among the observed endothermic peaks is taken as the maximum endothermic peak temperature. For crystalline resins, the maximum endothermic peak temperature is taken as the melting point.

[Glass transition temperature of resin]
Using a differential scanning calorimeter "Q-100" (manufactured by TA Instruments Japan, Inc.), 0.01 to 0.02 g of a sample is 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 is then heated at a 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 apex of the peak.

[Acid value of resin]
Measurement is performed based on the method of JIS K 0070: 1992. However, the measurement solvent is changed from the mixed solvent of ethanol and ether specified in JIS K 0070 to a mixed solvent of acetone and toluene (acetone:toluene=1:1 (volume ratio)).

[Melting point of release agent]
Using a differential scanning calorimeter "Q-100" (manufactured by TA Instruments Japan, Inc.), 0.02 g of a sample is weighed into an aluminum pan, heated to 200°C, and then cooled from 200°C to 0°C at a temperature drop rate of 10°C/min. The sample is then heated at a temperature rise rate of 10°C/min, the amount of heat is measured, and the maximum endothermic peak temperature is taken as the melting point.

[Volume Median Particle Size and CV Value of Resin Particles, Quaternary Ammonium Salt Compound Particles, Colorant Particles, and Release Agent Particles]
(1) Measuring device: Laser diffraction type particle size measuring device "LA-920" (manufactured by Horiba, Ltd.)
(2) Measurement conditions: Put a sample dispersion in a measurement cell, add distilled water, and measure the volume median particle size ( _D50 ) and volume average particle size at a temperature where the absorbance is in the appropriate range. The CV value is 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, Quaternary Ammonium Salt Compound Particle Dispersion, Colorant Particle Dispersion, and Release Agent Particle Dispersion]
Using an infrared moisture meter "FD-230" (Kett Electric Laboratory Co., Ltd.), 5 g of the measurement sample is dried under conditions of a drying temperature of 150°C and measurement mode 96 (monitoring time 2.5 minutes, fluctuation range 0.05%), and the moisture content (mass%) of the dispersion is measured. The solid content concentration is calculated according to the following formula.
Solid content concentration (mass%) = 100 - water (mass%)

[Volume Median Particle Size of Agglomerated Particles]
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" (manufactured by Beckman Coulter, Inc.)
Electrolyte: "Isoton (registered trademark) II" (manufactured by Beckman Coulter, Inc.)
Measurement conditions: A sample dispersion is added to 100 mL of the electrolyte to adjust the concentration to a level that allows the particle size of 30,000 particles to be measured in 20 seconds. The 30,000 particles are then measured, and the volume median particle size ( _D50 ) is determined from the particle size distribution.

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

[Volume Median Particle Size ( _D50 ) of Toner]
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" (manufactured by Beckman Coulter, Inc.)
Dispersion: Polyoxyethylene lauryl ether "EMULGEN (registered trademark) 109P" [manufactured by Kao Corporation, 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, 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 was added, and the mixture was further dispersed for 1 minute using the ultrasonic disperser to prepare a sample dispersion.
Measurement conditions: The sample dispersion is added to 100 mL of the electrolyte to adjust the concentration to a level that allows the particle size of 30,000 particles to be measured in 20 seconds. The 30,000 particles are then measured, and the volume median particle size ( _D50 ) is determined from the particle size distribution.

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

Preparation of alkenyl succinic anhydride 1
(1) Propylene tetramer (manufactured by Nippon Oil Corporation, trade name: "Light Tetramer") was used and fractionated under heating conditions of 183 to 208 ° C. to obtain an alkylene compound (a). The obtained alkylene compound (a) had 40 peaks in gas chromatography mass spectrometry described later. The distribution of the alkylene compounds was measured according to the analysis of alkylene compound A by mass spectrometry gas chromatography in JP 2014-013384 A, and was C ₉ H ₁₈ : 0.5 mass%, C ₁₀ H ₂₀ : 4 mass%, C ₁₁ H ₂₂ : 20 mass%, C ₁₂ H ₂₄ : 66 mass%, C ₁₃ H ₂₆ : 9 mass%, C ₁₄ H ₂₈ : 0.5 mass% (6 peaks corresponding to alkylene compounds having 9 to 14 carbon atoms).

(2) 542.4 g of alkylene compound (a), 157.2 g of maleic anhydride, 0.4 g of antioxidant "Chelex-O" (SC Organic Chemical Co., Ltd., Triisooctyl phosphate), and 0.1 g of butyl hydroquinone as a polymerization inhibitor were charged into a 1 L autoclave manufactured by Nitto Koatsu Co., Ltd., and pressurized nitrogen replacement (0.2 MPaG) was repeated three times. After stirring was started at 60 ° C, the temperature was raised to 230 ° C over 1 hour and the reaction was carried out for 6 hours. The pressure when the reaction temperature was reached was 0.3 MPaG. After the reaction was completed, the mixture was cooled to 80 ° C, returned to normal pressure (101.3 kPa), and transferred to a 1 L four-neck flask. The temperature was raised to 180 ° C with stirring, and the remaining alkylene compound was distilled off at 1.3 kPa for 1 hour. The mixture was then cooled to room temperature (25°C) and returned to normal pressure (101.3 kPa) to obtain 406.1 g of the target alkenyl succinic anhydride A. The average molecular weight of alkenyl succinic anhydride A calculated from the acid value was 268.

Resin Production Example 1
The alcohol component, the carboxylic acid component other than trimellitic anhydride, PET, the esterification catalyst, and the esterification promoter shown in Tables 1 to 3 were placed in a 10-liter four-neck flask equipped with a nitrogen inlet tube, a stirrer, and a thermocouple, and the temperature was raised to 235° C. under a nitrogen atmosphere, and then polycondensed at 235° C. for 6 hours. The temperature was then lowered to 210° C., and trimellitic anhydride shown in Tables 1 to 3 was added, and the mixture was reacted at 210° C. for 1 hour, and then further reacted at 210° C. under a reduced pressure of 10 kPa until the softening point shown in Tables 1 to 3 was reached, to obtain amorphous polyester resins (resins AH1 to AH5, AH8, AH11 to AH14). The physical properties are shown in Tables 1 to 3.

Resin Production Example 2
The alcohol component, carboxylic acid component, PET, esterification catalyst, and esterification promoter shown in Tables 2 and 5 were placed in a 10-liter four-neck flask equipped with a nitrogen inlet tube, a stirrer, and a thermocouple, and the mixture was kept at 180° C. for 1 hour under a nitrogen atmosphere, then heated from 180° C. to 235° C. at a rate of 10° C./h, and polycondensed at 235° C. for 5 hours. The temperature was then lowered to 210° C., and the reaction was continued under a reduced pressure of 10 kPa until the softening points shown in Tables 2 and 5 were reached, to obtain amorphous polyester resins (resins AH6, AH7, resins AL6, AL7). The physical properties are shown in Tables 2 and 5.

Resin Production Example 3
The alcohol component, carboxylic acid component other than trimellitic anhydride and fumaric acid, PET, esterification catalyst, and esterification promoter shown in Table 2 were placed in a 10-liter four-neck flask equipped with a nitrogen inlet tube, a stirrer, and a thermocouple, and heated to 235 ° C. under a nitrogen atmosphere, and then polycondensed at 235 ° C. for 6 hours. The temperature was then lowered to 180 ° C., and trimellitic anhydride, fumaric acid, and a polymerization inhibitor shown in Table 2 were added, and reacted at 180 ° C. for 1 hour, and then the temperature was raised from 180 ° C. to 210 ° C. at 10 ° C. / h, and polycondensed at 210 ° C. for 1 hour. Then, the reaction was carried out at 210 ° C. under a reduced pressure of 10 kPa until the softening point shown in Table 2 was reached, and an amorphous polyester resin (resin AH9) was obtained. The physical properties are shown in Table 2.

Resin Production Example 4
The alcohol component, the carboxylic acid component other than trimellitic anhydride, the esterification catalyst, and the esterification promoter shown in Table 2 were placed in a 10-liter four-neck flask equipped with a nitrogen inlet tube, a stirrer, and a thermocouple, and the temperature was raised to 235° C. under a nitrogen atmosphere, and then polycondensed at 235° C. for 6 hours. The temperature was then lowered to 210° C., and trimellitic anhydride shown in Table 2 was added, and the mixture was reacted at 210° C. for 1 hour, and then further reacted at 210° C. under a reduced pressure of 10 kPa until the softening point shown in Table 2 was reached, to obtain an amorphous polyester resin (resin AH10). The physical properties are shown in Table 2.

Resin Production Example 5
The alcohol component, carboxylic acid component, PET, esterification catalyst, and esterification promoter shown in Tables 4 to 6 were placed in a 10-liter four-neck flask equipped with a nitrogen inlet tube, a stirrer, and a thermocouple, and the temperature was raised to 235° C. under a nitrogen atmosphere, and polycondensation was carried out at 235° C. for 6 hours. The temperature was then lowered to 210° C., and the reaction was carried out under a reduced pressure of 10 kPa until the softening points shown in Tables 4 to 6 were reached, thereby obtaining amorphous polyester resins (resins AL1 to AL5, AL8, and AL11 to AL14). The physical properties are shown in Tables 4 to 6.

Resin Production Example 6
The alcohol component, carboxylic acid component other than fumaric acid, PET, esterification catalyst, and esterification promoter shown in Table 5 were placed in a 10-liter four-neck flask equipped with a nitrogen inlet tube, a stirrer, and a thermocouple, and heated to 235 ° C. under a nitrogen atmosphere, and then polycondensed at 235 ° C. for 6 hours. The temperature was then lowered to 180 ° C., and fumaric acid and a polymerization inhibitor shown in Table 5 were added, and reacted at 180 ° C. for 1 hour, and then the temperature was raised from 180 ° C. to 210 ° C. at 10 ° C. / h, and polycondensed at 210 ° C. for 1 hour. Then, the reaction was carried out at 210 ° C. under a reduced pressure of 10 kPa until the softening point described in Table 5 was reached, and an amorphous polyester resin (resin AL9) was obtained. The physical properties are shown in Table 5.

Resin Production Example 7
The alcohol component, carboxylic acid component, esterification catalyst, and esterification promoter shown in Table 5 were placed in a 10-liter four-neck flask equipped with a nitrogen inlet tube, a stirrer, and a thermocouple, and the temperature was raised to 235° C. under a nitrogen atmosphere, and then polycondensation was carried out at 235° C. for 6 hours. The temperature was then lowered to 210° C., and the reaction was carried out under a reduced pressure of 10 kPa until the softening point shown in Table 5 was reached, to obtain an amorphous polyester resin (resin AL10). The physical properties are shown in Table 5.

Example 1, Examples 5 to 12, Examples 16 to 19, Comparative Example 2 [Melt-kneading method]
100 parts by mass of the binder resin shown in Table 7, 5 parts by mass of a colorant "ECB-301" (manufactured by Dainichiseika Color & Chemicals Mfg. Co., Ltd., phthalocyanine blue (P.B.15:3)), 3 parts by mass of a release agent "Carnauba Wax C1" (manufactured by Kato Yoko Co., Ltd., melting point: 83°C), and 10 parts by mass of a positively charged charge control agent "FCA-201-PS" (manufactured by Fujikura Kasei Co., Ltd., softening point: 119°C, glass transition temperature: 65°C), which is a quaternary ammonium salt-containing styrene-based resin, were mixed in a Henschel mixer.

The resulting mixture was melt-kneaded using a co-rotating twin-screw extruder with a kneading section total length of 1,560 mm, a screw diameter of 42 mm, and a barrel inner diameter of 43 mm at a screw rotation speed of 200 r/min and a barrel set temperature of 100°C to obtain a molten kneaded product. The mixture was fed at a rate of 20 kg/h and had an average residence time of approximately 18 seconds.

The resulting molten kneaded product was cooled, coarsely pulverized, pulverized in a jet mill, and classified using an air classifier (manufactured by Nippon Pneumatic Mfg. Co., Ltd.) to obtain toner particles having a volume median particle size (D ₅₀ ) of 7.0 μm.

100 parts by mass of the obtained toner particles were mixed with 0.5 parts by mass of hydrophobic silica "TG820F" (manufactured by Cabot Corporation, hydrophobic treatment agent: HMDS and cyclic silazane, average particle size 8 nm) and 1.0 part by mass of hydrophobic silica "NA50Y" (manufactured by Nippon Aerosil Co., Ltd., hydrophobic treatment agent: silicone oil and aminosilane, average particle size 40 nm) as external additives in a Henschel mixer (manufactured by Nippon Coke and Engineering Co., Ltd.) at a rotation speed of 3000 r/min (circumferential speed 32 m/sec) for 3 minutes to obtain a toner.

Examples 2 to 4, Comparative Example 1
A toner was obtained in the same manner as in Example 1, except that the amount of the positively charged charge control agent ("FCA-201-PS") used was changed to the number of parts shown in Table 7.

Example 13
A toner was obtained in the same manner as in Example 1, except that 10 parts by mass of "BONTRON P-51" (manufactured by Orient Chemical Industries Co., Ltd.) was used instead of "FCA-201-PS" as the positively charged charge control agent.

Example 14
A toner was obtained in the same manner as in Example 1, except that the melt-kneading was performed using a continuous open-roll type twin-screw kneader "Kneedex" (manufactured by Nippon Coke & Engineering Co., Ltd.) instead of the same-rotation twin-screw extruder. The continuous open-roll type twin-screw kneader had a roll outer diameter of 0.14 m and an effective roll length of 0.8 m, and the operating conditions were a rotation speed of the high-rotation roll (front roll) of 75 r/min (circumferential speed 33 m/min), a rotation speed of the low-rotation roll (rear roll) of 50 r/min (circumferential speed 22 m/min), and a roll gap of 0.1 mm. The heating and cooling medium temperatures in the rolls were set as follows: the temperature of the raw material input side of the high-rotation roll was set to 140°C, and the temperature of the kneaded material discharge side was set to 110°C, and the temperature of the raw material input side of the low-rotation roll was set to 65°C, and the temperature of the kneaded material discharge side was set to 30°C. The supply rate of the raw material mixture was 10 kg/h, and the average residence time was about 5 minutes.

Example 15 [Emulsion aggregation method]
<Preparation of Aqueous Dispersion of Core Resin Particles>
600 g of methyl ethyl ketone was added to a 5-liter container equipped with a stirrer, a reflux condenser, a dropping funnel, a thermometer, and a nitrogen inlet tube, and 150 g of resin AH1 was added at 60 ° C. and dissolved. A 5% by mass aqueous solution of sodium hydroxide was added to the obtained solution so that the degree of neutralization was 60 mol% with respect to the acid value of the resin, and the mixture was stirred for 30 minutes to obtain a mixture. Subsequently, 675 g of deionized water was added over 77 minutes. Next, while stirring at 250 r / min, methyl ethyl ketone and a part of the water were distilled off at a temperature of 50 ° C. or less under reduced pressure, and the solid content concentration of the aqueous dispersion was measured, and the solid content concentration of the aqueous dispersion was adjusted to 20% by mass with deionized water to obtain a core resin dispersion. The volume median particle size (D ₅₀ ) of the resin particles in the dispersion was 200 nm, and the CV value was 24%.

<Preparation of Aqueous Dispersion of Shell Resin Particles>
600 g of methyl ethyl ketone was added to a 5-liter container equipped with a stirrer, a reflux condenser, a dropping funnel, a thermometer, and a nitrogen inlet tube, and 150 g of resin AL1 was added at 60 ° C. and dissolved. A 5% by mass aqueous solution of sodium hydroxide was added to the obtained solution so that the degree of neutralization was 60 mol% with respect to the acid value of the resin, and the mixture was stirred for 30 minutes to obtain a mixture. Subsequently, 675 g of deionized water was added over 77 minutes. Next, while stirring at 250 r / min, methyl ethyl ketone and a part of the water were distilled off at a temperature of 50 ° C. or less under reduced pressure, and then the solid content concentration of the aqueous dispersion was measured, and the solid content concentration of the aqueous dispersion was adjusted to 20% by mass with deionized water to obtain a shell resin dispersion. The volume median particle size (D ₅₀ ) of the resin particles in the dispersion was 110 nm, and the CV value was 20%.

<Preparation of Quaternary Ammonium Salt Compound Dispersion>
In a 1-liter beaker, 100.0 g of a positively charged charge control agent "FCA-201-PS" (manufactured by Fujikura Chemical Co., Ltd.), which is a quaternary ammonium salt-containing styrene-based resin, 133.3 g of an anionic surfactant "Neopelex (registered trademark) G-15" (manufactured by Kao Corporation, 15% by mass sodium dodecylbenzenesulfonate aqueous solution), and 268.5 g of deionized water were mixed and dispersed at room temperature for 1 hour at a rotation speed of 8000 r/min of the stirring blade using a homogenizer "T.K.AGI HOMOMIXER 2M-03" (manufactured by Primix Corporation). Thereafter, the mixture was treated with a homogenizer "Microfluidizer M-110EH" (manufactured by Microfluidics Co., Ltd.) at a pressure of 150 MPa for 12 passes. The mixture was then passed through a 200 mesh filter, and deionized water was added to give a solid content of 12% by mass, to obtain a quaternary ammonium salt compound dispersion. The volume median particle size ( _D50 ) of the quaternary ammonium salt compound particles in the dispersion was 150 nm, and the CV value was 30%.

<Preparation of Colorant Dispersion>
Into a 1-liter beaker, 116.2 g of colorant "ECB-301" (Dainichiseika Color & Chemicals Mfg. Co., Ltd., phthalocyanine blue (P.B.15:3)), 154.9 g of anionic surfactant "Neopelex (registered trademark) G-15" (Kao Corporation, 15% by mass aqueous solution of sodium dodecylbenzenesulfonate) and 260 g of deionized water were mixed and dispersed using a homogenizer at room temperature for 3 hours, and then deionized water was added so that the solids concentration became 24% by mass, thereby obtaining a colorant dispersion. The volume median particle diameter (D ₅₀ ) of the colorant particles in the dispersion was 118 nm, and the CV value was 27%.

<Preparation of release agent dispersion>
50 g of Fischer-Tropsch wax (manufactured by Nippon Seiro Co., Ltd., trade name: FNP0090, melting point: 90° C.), 5 g of a cationic surfactant (manufactured by Kao Corporation, trade name: Sanisol B50) and 200 g of deionized water were heated to 95° C., and the paraffin wax was dispersed using a homogenizer. The resultant was then dispersed using a pressure discharge homogenizer, and deionized water was added to obtain a release agent dispersion having a solid content concentration of 20 mass %. The volume median particle diameter (D ₅₀ ) of the release agent particles in the dispersion was 550 nm, and the CV value was 26%.

<Preparation of Toner Particles>
In a 3-liter four-neck flask equipped with a dehydration tube, a stirrer, and a thermocouple, 500 g of the core resin dispersion, 143 g of the quaternary ammonium salt compound dispersion, 36 g of the colorant dispersion, 33 g of the release agent dispersion, and 3.3 g of a 15% by mass aqueous solution of sodium dodecylbenzenesulfonate "Neopelex G-15" (manufactured by Kao Corporation, an anionic surfactant) were mixed at a temperature of 25° C. Next, while stirring the resulting mixture, a solution obtained by dissolving 40 g of ammonium sulfate in 570 g of deionized water and adding a 4.8% by mass aqueous solution of potassium hydroxide to adjust the pH to 8.2 was dropped over 10 minutes at 25° C., and the temperature was raised to 62° C. over 2 hours, and the temperature was maintained at 62° C. until the volume median particle size (D ₅₀ ) of the aggregated particles became 6.9 μm, thereby obtaining a dispersion of aggregated particles (I).

While maintaining the temperature of the obtained dispersion of aggregated particles (I) at 62° C., 215 g of the shell resin dispersion was added dropwise at a rate of 0.6 mL/min (0.6 g/min) to obtain a dispersion of aggregated particles (II). The volume median particle size (D ₅₀ ) of the aggregated particles (II) was 7.0 μm.

To the obtained dispersion of aggregated particles (II), an aqueous solution of 20 g of sodium polyoxyethylene lauryl ether sulfate "EMAL E-27C" (Kao Corporation, anionic surfactant, effective concentration 27% by mass), 280 g of deionized water, and 40 g of 0.1 mol/L aqueous sulfuric acid solution was added. The temperature was then raised to 80°C over 1 hour, and the mixture was held at 80°C for 30 minutes, after which 10 g of 0.1 mol/L aqueous sulfuric acid solution was added and the mixture was held at 80°C for a further 15 minutes. Then, 15 g of 0.1 mol/L aqueous sulfuric acid solution was added again, and the mixture was held at 80°C until the circularity reached 0.970, thereby obtaining a dispersion of fused particles (core-shell particles) in which the aggregated particles were fused.

The obtained core-shell particle dispersion was cooled to 30°C, and the dispersion was suction filtered to separate the solids, which were then washed with deionized water at 25°C and suction filtered at 25°C for 2 hours. The toner particles were then vacuum dried at 33°C for 24 hours using a vacuum constant temperature dryer "DRV622DA" (manufactured by ADVANTEC) to obtain toner particles. The particle size of the obtained toner particles was 7.0 μm and the circularity was 0.970. The composition ratio (mass ratio) of the binder resin of the obtained toner particles was resin AH1/resin AL1 = 70/30.

100 parts by mass of the obtained toner particles were mixed with 0.5 parts by mass of hydrophobic silica "TG820F" (manufactured by Cabot Corporation, hydrophobic treatment agent: HMDS and cyclic silazane, average particle size 8 nm) and 1.0 part by mass of hydrophobic silica "NA50Y" (manufactured by Nippon Aerosil Co., Ltd., hydrophobic treatment agent: silicone oil and aminosilane, average particle size 40 nm) as external additives in a Henschel mixer (manufactured by Nippon Coke and Engineering Co., Ltd.) at a rotation speed of 3000 r/min (circumferential speed 32 m/sec) for 3 minutes to obtain a toner.

Test Example [Charging Stability of Toner]
Under conditions of a temperature of 25° C. and a relative humidity of 50%, 0.6 g of toner and 19.4 g of silicone ferrite carrier (manufactured by Kanto Denka Kogyo Co., Ltd., average particle size 90 μm) were placed in a 50 mL polyethylene container and mixed at 250 rpm using a ball mill. The charge amount of the toner was measured using a Q/M meter (manufactured by EPPING Corporation) by the following method.

After 60 or 600 seconds of mixing, a specified amount of toner and carrier mixture was put into a cell attached to the Q/M meter, and only the toner was sucked through a 32 μm mesh sieve (stainless steel, twill weave, wire diameter: 0.0035 mm) for 90 seconds. The voltage change on the carrier that occurred at that time was monitored, and the value of [total amount of electricity after 90 seconds (μC) / amount of sucked toner (g)] was taken as the charge amount (μC/g). The ratio of the charge amount after 60 seconds of mixing to the charge amount after 600 seconds of mixing (charge amount after 60 seconds of mixing / charge amount after 600 seconds of mixing) was calculated to evaluate the charge stability. The results are shown in Table 7. The larger the value, the better the charge stability.

The above results show that the toners of Examples 1 to 19 have good charge stability compared to Comparative Example 1, which contains a low amount of quaternary ammonium salt compound, and Comparative Example 2, which contains an amorphous polyester resin without using PET. In particular, a comparison between Example 1 and Example 13 shows that the charge stability of the toner is further improved by including a polymeric quaternary ammonium salt compound.

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

Claims (12)

A toner for developing electrostatic images containing an amorphous polyester resin A and a quaternary ammonium salt compound X, wherein the amorphous polyester resin A is a polycondensate of an alcohol component, a carboxylic acid component, and polyethylene terephthalate, and the content of the quaternary ammonium salt compound X is 3 parts by mass or more and 30 parts by mass or less per 100 parts by mass of the amorphous polyester resin A. The toner for developing electrostatic images according to claim 1, wherein the content of polyethylene terephthalate is 5 mol % or more and 75 mol % or less of the total amount of the alcohol component, the carboxylic acid component, and the polyethylene terephthalate, with terephthalic acid-ethylene glycol units being 1 mol. The toner for developing electrostatic images according to claim 1, wherein the content of polyethylene terephthalate is 20 mol % or more and 50 mol % or less of the total amount of the alcohol component, the carboxylic acid component, and the polyethylene terephthalate, with 1 mol of a terephthalic acid-ethylene glycol unit. The toner for developing electrostatic images according to any one of claims 1 to 3, wherein the quaternary ammonium salt compound X is a resin containing a quaternary ammonium salt. The toner for developing electrostatic images according to any one of claims 1 to 3, wherein the content of the quaternary ammonium salt compound X is 8 parts by mass or more and 20 parts by mass or less per 100 parts by mass of the amorphous polyester resin A. The toner for developing electrostatic images according to any one of claims 1 to 3, wherein the IV value of the polyethylene terephthalate is 0.40 or more and 0.85 or less. The toner for developing electrostatic images according to any one of claims 1 to 3, wherein the amorphous polyester resin A contains amorphous resins having different softening points with a difference of 10°C or more. The toner for developing electrostatic images according to claim 7, wherein the softening point of the amorphous resin having the higher softening point is 100°C or higher and 170°C or lower. The toner for developing electrostatic images according to claim 7, wherein the softening point of the amorphous resin having the lower softening point is 70°C or higher and 130°C or lower. The toner for developing electrostatic images according to claim 7, wherein the mass ratio of the amorphous resin having a higher softening point to the amorphous resin having a lower softening point is 10/90 or more and 90/10 or less. The toner for developing electrostatic images according to any one of claims 1 to 3, wherein amorphous polyester resin A is contained as a binder resin, and the content of the amorphous polyester resin A in the binder resin is 70% by mass or more. The toner for developing electrostatic images according to any one of claims 1 to 3, wherein the quaternary ammonium salt compound X is a styrene-based resin containing a quaternary ammonium salt.