JP7846566B2 - Toner binder resin - Google Patents

Description

This invention relates to a binder resin used in toners used for developing latent images formed in electrophotography, electrostatic recording, electrostatic printing, and the like.

In recent years, in the field of electrophotography, the development of electrostatic image developing toners that support high-resolution and high-speed printing has been required as electrophotographic systems have advanced. To meet these demands, a composite resin, in which a polyester resin with excellent low-temperature fixability is covalently bonded to an addition polymerization resin, has been proposed as a binder resin for toners.
Patent Document 1 discloses a toner binder resin composition that contains an amorphous composite resin in which a polyester resin obtained by polycondensing a polycondensable monomer containing a carboxylic acid component and an alcohol component with polyethylene terephthalate and a vinyl resin obtained by addition polymerization of an addition polymerizable monomer are chemically bonded via reactive monomers that can react with either the polycondensable monomer or the addition polymerizable monomer, and the polyethylene terephthalate contains polyethylene terephthalate with an IV value of 0.40 or more and 0.75 or less, thereby obtaining a toner with excellent low-temperature fixability.
Furthermore, Patent Document 2 discloses a toner having toner particles containing a binder resin and a colorant, wherein the binder resin is a hybrid resin in which a vinyl polymer unit obtained by polymerizing a vinyl monomer in the absence of a polyester unit and its raw materials is chemically bonded with a polyester unit, thereby providing a toner with excellent low-temperature fixability, storage properties, and control over toner fusion to the photosensitive drum.

Japanese Patent Publication No. 2018-13523 Japanese Patent Publication No. 2018-10124

Generally, lowering the minimum fixing temperature and raising the temperature at which high-temperature offset occurs widens the fixing temperature range, thus meeting the demands for energy saving and high-speed fixing. Therefore, there is a high demand for binder resins and toners with a wide fixing temperature range.
Furthermore, toner is generally required to have heat resistance, meaning that the toner particles do not aggregate even when stored for a long period of time under high temperature and high humidity conditions.
However, in the toner disclosed in Patent Document 1, the vinyl resin constituting the composite resin is obtained by addition polymerization of a vinyl monomer in the presence of a polycondensable monomer containing a carboxylic acid component and an alcohol component and polyethylene terephthalate. Therefore, there are challenges in controlling the molecular weight and molecular weight distribution, as well as monomer copolymerizability. Consequently, it was later found that the composite resin obtained by polycondensation of the polycondensable monomer and polyethylene terephthalate does not have sufficient resistance to high temperature offset.
Furthermore, in the toner disclosed in Patent Document 2, the acid value of the vinyl polymer constituting the hybrid resin is low, resulting in insufficient resin compounding and inadequate resistance to high-temperature offset and heat storage.
Furthermore, because the increased molecular weight due to resin compounding leads to a decrease in the pulverability of the resin, improvements in productivity, such as pulverability, are also required.
The present invention relates to a binder resin for toner that maintains excellent low-temperature fixing properties while having a wide fixing temperature range, and is excellent in heat resistance for storage and productivity, a toner for electrostatic image development, and a method for manufacturing the binder resin for toner.

The present inventors have found that the above problem can be solved by providing a binder resin for toner containing a composite resin in which a polyester resin unit with excellent low-temperature fixability and an addition polymerization resin unit with excellent high-temperature offset resistance are bonded together via covalent bonds, wherein the addition polymerization resin constituting the addition polymerization resin unit of the composite resin contains 60% by mass or more of constituent units derived from (meth)acrylic monomers, and the acid value of the addition polymerization resin is set to a predetermined value or higher.
In other words, the present invention relates to the following embodiments [1] to [3].
[1] A binder resin for toner containing a composite resin in which an addition polymerization resin unit and a polyester resin unit are bonded together via covalent bonds,
The addition polymerization resin (A) constituting the addition polymerization resin unit contains 60% by mass or more of constituent units derived from (meth)acrylic monomers,
A binder resin for toner, wherein the acid value of the addition polymerization resin (A) is 40 mg KOH/g or more.
[2] A toner for developing electrostatic images, comprising the toner binder resin described in [1] above.
[3] A method for producing a binder resin for toner, which contains a composite resin in which an addition polymerization resin unit and a polyester resin unit are bonded together via covalent bonds,
The process includes: Step I: Polymerizing a raw material monomer (a) to obtain an addition polymerization resin (A); and Step II: Reacting an alcohol component (b-al) with a carboxylic acid component (b-ac), then adding the addition polymerization resin (A) obtained in Step I and carrying out the reaction to obtain the composite resin.
The raw material monomer (a) contains 60% by mass or more of a (meth)acrylic monomer,
A method for producing a binder resin for toner, wherein the acid value of the addition polymerization resin (A) is 40 mg KOH/g or more.

According to the present invention, it is possible to provide a toner binder resin, a toner for electrostatic image development, and a method for manufacturing the toner binder resin that maintain excellent low-temperature fixing properties while having a wide fixing temperature range, and that also exhibits excellent heat resistance for storage and productivity.

[Toner binder resin]
The toner binder resin of the present invention (hereinafter also referred to as "the binder resin of the present invention") contains a composite resin in which an addition polymerization resin unit and a polyester resin unit are bonded together via covalent bonds.
Furthermore, the addition polymerization resin (A) constituting the addition polymerization resin unit contains 60% by mass or more of constituent units derived from (meth)acrylic monomers, and the acid value of the addition polymerization resin (A) is 40 mg KOH/g or more.
The toner of the present invention exhibits excellent low-temperature fixing properties while having a wide fixing temperature range, as well as excellent heat resistance and productivity.

The reason why the effects of this invention are obtained is not entirely clear, but it is thought to be as follows.
The addition polymerization resin unit of the composite resin contained in the binder resin of the present invention contains 60% by mass or more of constituent units derived from (meth)acrylic monomers, and the acid value of the addition polymerization resin is 40 mg KOH/g or more. This facilitates the control of molecular motion at low temperatures and polymer chain entanglement at high temperatures, resulting in a resin that is low viscosity at low temperatures and highly elastic at high temperatures. This improves low-temperature fixability and high-temperature offset resistance, broadening the fixability temperature range, improving heat-resistant storage, and maintaining high viscosity during toner production. As a result, shear force is efficiently applied, improving mixability with other components such as colorants contained in the toner, and thus improving productivity.

The definitions of various terms used in this specification are shown below.
The crystallinity of a resin is expressed by the crystallinity index, which is defined as the ratio of the softening point to the maximum endothermic peak temperature measured by a differential scanning calorimeter (DSC), i.e., "softening point / maximum endothermic peak temperature". Generally, if this crystallinity index exceeds 1.4, the resin is amorphous, and if it is less than 0.6, the crystallinity is low and there is a large amorphous portion. In the present invention, "amorphous resin" refers to a resin whose crystallinity index exceeds 1.4 or is less than 0.6, and "crystalline resin" refers to a resin whose crystallinity index is 0.6 or higher, preferably 0.7 or higher, more preferably 0.9 or higher, and 1.4 or lower, preferably 1.2 or lower.
The "maximum endothermic peak temperature" mentioned above refers to the temperature of the peak with the largest peak area among the endothermic peaks observed under the measurement conditions described in the examples.
The crystallinity of the resin can be adjusted by the type and ratio of raw material monomers, as well as the manufacturing conditions (e.g., reaction temperature, reaction time, cooling rate).
"Polyester resin" may include a polyester resin that has been modified to the extent that its properties are not substantially impaired. Examples of modified polyester resins include urethane-modified polyester resin, in which the polyester resin is modified with urethane bonds, and epoxy-modified polyester resin, in which the polyester resin is modified with epoxy bonds.
"Bisphenol A" refers to 2,2-bis(4-hydroxyphenyl)propane.
Examples of "carboxylic acid compounds" include carboxylic acids, their anhydrides, and alkyl esters having 1 to 3 carbon atoms. Note that the number of carbon atoms in the alkyl group of an alkyl ester is not included in the number of carbon atoms in the carboxylic acid compound.
"Binding resin" refers to the resin component in toner, including the composite resin.

<Composite resin>
A composite resin is a resin in which addition polymerization resin units and polyester resin units are bonded together via covalent bonds.
Furthermore, the addition polymerization resin (A) constituting the addition polymerization resin unit (hereinafter also referred to as "addition polymerization resin (A)") contains 60% by mass or more of constituent units derived from (meth)acrylic monomers, and the acid value of the addition polymerization resin (A) is 40 mgKOH/g or more.

[Addition polymerization resin (A)]
(Raw material monomer (a))
The addition polymerization resin (A) constitutes the addition polymerization resin unit of the composite resin, from the viewpoint of broadening the fixing temperature range while maintaining excellent low-temperature fixing properties, and from the viewpoint of improving heat resistance, storage properties, and productivity, and is an addition polymerization product of the addition polymerization raw material monomer (a).
The raw material monomer (a) contains 60% by mass or more of (meth)acrylic monomers, from the same viewpoint as described above. One or more types of raw material monomer (a) may be used. That is, the addition polymerization resin (A) may be a homopolymer made using only one type of raw material monomer (a), or it may be a copolymer made using two or more types of raw material monomer (a), but it is preferable that it be a copolymer.

Examples of (meth)acrylic monomers include acrylic acid, methacrylic acid, and (meth)acrylic acid derivatives.
Examples of (meth)acrylic acid derivatives include (meth)acrylic acid esters such as methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, tert-butyl (meth)acrylate, amyl (meth)acrylate, cyclohexyl (meth)acrylate, n-octyl (meth)acrylate, isooctyl (meth)acrylate, decyl (meth)acrylate, lauryl (meth)acrylate, 2-ethylhexyl (meth)acrylate, stearyl (meth)acrylate, methoxyethyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, glycidyl (meth)acrylate, 2-chloroethyl (meth)acrylate, phenyl (meth)acrylate, 2-(dimethylamino)ethyl (meth)acrylate, 2-(diethylamino)ethyl (meth)acrylate, and methyl α-chloroacrylate. Furthermore, the (meth)acrylic acid ester may be one that has a hydroxyl group, such as 2-hydroxyethyl methacrylate.
Here, "(meth)acrylic acid" includes both acrylic acid and methacrylic acid. Similarly, "(meth)acrylic acid ester" includes both acrylic acid ester and methacrylic acid ester.
In particular, the (meth)acrylic monomer preferably contains one or more selected from acrylic acid and methacrylic acid, from the viewpoint of giving the addition polymerization resin (A) a desired acid value.

The raw material monomer (a) may also include a styrene compound as a monomer other than the (meth)acrylic monomer.
Examples of styrene compounds include styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, α-methylstyrene, p-ethylstyrene, 2,4-dimethylstyrene, p-chlorostyrene, vinylnaphthalene, and other styrene and styrene derivatives, with styrene and α-methylstyrene being preferred.

Furthermore, the raw material monomer (a) may also contain monomers other than (meth)acrylic monomers and styrene compounds.
Other monomers include, for example, ethylenically unsaturated monoolefins such as ethylene, propylene, butylene, and isobutylene; diolefins such as butadiene; halovinyls such as vinyl chloride, vinyl bromide, and vinyl fluoride; vinyl esters such as vinyl acetate, vinyl propionate, vinyl formate, and vinyl caproate; vinyl ethers such as vinyl methyl ether; vinylidene halides such as vinylidene chloride; and N-vinyl compounds such as N-vinylpyrrole and N-vinylpyrrolidone.

The raw material monomer (a) preferably comprises one or more selected from acrylic acid and methacrylic acid as (meth)acrylic monomers, and more preferably comprises one or more selected from acrylic acid and methacrylic acid as (meth)acrylic monomers and an alkyl (meth)acrylate ester.
The number of carbon atoms in the alkyl group of the (meth)acrylate is preferably 1 or more, preferably 22 or less, more preferably 18 or less, even more preferably 12 or less, and even more preferably 8 or less.
Furthermore, the number of carbon atoms in the alkyl group of (meth)acrylate alkyl ester refers to the number of carbon atoms derived from the alcohol component constituting the (meth)acrylate alkyl ester.
Specifically, the alkyl (meth)acrylate ester is preferably one or more selected from methyl acrylate, n-butyl acrylate, 2-ethylhexyl acrylate, stearyl acrylate, methyl methacrylate, n-butyl methacrylate, and 2-hydroxyethyl methacrylate.

The content of (meth)acrylic monomers in the raw material monomer (a) constituting the addition polymerization resin (A), or the content of constituent units derived from (meth)acrylic monomers in the addition polymerization resin (A), is 60% by mass or more, 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 preferably 100% by mass or less, from the viewpoint of broadening the fixing temperature range while maintaining excellent low-temperature fixing properties, and from the viewpoint of further improving heat resistance and productivity.
When the raw material monomer (a) constituting the addition polymerization resin (A) contains one or more selected from acrylic acid and methacrylic acid, the total content of acrylic acid and methacrylic acid in the raw material monomer (a) or the total content of acrylic acid-derived constituent units and methacrylic acid-derived constituent units in the addition polymerization resin (A) is preferably 0.5% by mass or more, more preferably 3% by mass or more, even more preferably 5% by mass or more, even more preferably 8% by mass or more, even more preferably 10% by mass or more, and preferably 40% by mass or less, more preferably 30% by mass or less, even more preferably 20% by mass or less, and even more preferably 15% by mass or less.
When the raw material monomer (a) constituting the addition polymerization resin (A) contains a styrene-based compound, the content of the styrene-based compound in the raw material monomer (a) constituting the addition polymerization resin (A) or the content of constituent units derived from the styrene-based compound in the addition polymerization resin (A) is preferably 0% by mass or more, more preferably 5% by mass or more, even more preferably 10% by mass or more, even more preferably 15% by mass or more, even more preferably 20% by mass or more, and preferably 40% by mass or less, more preferably 30% by mass or less, and even more preferably 25% by mass or less, from the viewpoint of broadening the fixing temperature range while maintaining excellent low-temperature fixing properties, and from the viewpoint of further improving heat resistance and productivity.

The total content of (meth)acrylic monomers and styrene compounds in the raw material monomer (a) constituting the addition polymerization resin (A), or the total content of constituent units derived from (meth)acrylic monomers and styrene compounds in the addition polymerization resin (A), is preferably 90% by mass or more, more preferably 95% by mass or more, even more preferably 99% by mass or more, and 100% by mass or less, and even more preferably 100% by mass, from the viewpoint of broadening the fixing temperature range while maintaining excellent low-temperature fixing properties, and from the viewpoint of further improving heat resistance and productivity.

In the present invention, the addition polymerization resin (A) constituting the addition polymerization resin unit can be formed by bulk polymerization, solution polymerization, suspension polymerization, or emulsion polymerization. Among these, the addition polymerization resin (A) is preferably formed by bulk polymerization in the absence of the polyester resin constituting the polyester resin unit or the polycondensation monomer constituting the polyester resin, from the viewpoint of controlling the molecular weight, molecular weight distribution, and copolymerizability of the monomers, widening the fixing temperature range while maintaining excellent low-temperature fixing properties, and improving heat resistance and productivity.
In this invention, "bulk polymerization" refers to addition polymerization carried out under conditions in which there is substantially no solvent in the reaction system, that is, under solvent-free conditions.

Bulk polymerization may also be carried out using a radical generator.
Examples of radical generators include peroxides such as di-tert-butyl peroxide, persulfates such as sodium persulfate, and azo compounds such as 2,2'-azobis(2,4-dimethylvaleronitrile).
In bulk polymerization, the concentration of the radical generator is preferably 10 parts by mass or less, more preferably 7 parts by mass or less, even more preferably 5 parts by mass or less, even more preferably 3 parts by mass or less, even more preferably 2 parts by mass or less, even more preferably 1 part by mass or less, even more preferably 0.5 parts by mass or less, and even more preferably 0 parts by mass or less, per 100 parts by mass of the raw material monomer (a) of the addition polymerization resin (A), from the viewpoint of controlling molecular weight, molecular weight distribution and copolymerizability, widening the fixing temperature range while maintaining excellent low-temperature fixing properties, and further improving heat resistance and productivity, that is, it is preferable to carry out the process under catalyst-free conditions.

Bulk polymerization is preferably carried out at high temperatures under pressure above atmospheric pressure, and more preferably as continuous bulk polymerization under high temperature and high pressure.
In this invention, a pressurized state refers to a state in which the contents are heated to a temperature above the boiling point under normal pressure in a sealed container such as an autoclave.
Under high pressure above atmospheric pressure and at high temperatures, radicals generated by the thermal initiation reaction of the raw material monomer (a) function as polymerization initiators. This allows addition polymerization to proceed even under conditions with relatively few radical generators, resulting in an addition polymerization resin (A) with a narrow molecular weight distribution.
Furthermore, in the case of continuous bulk polymerization under high temperature and high pressure, the monomer composition distribution can be controlled in addition to the molecular weight distribution, making it possible to obtain a more uniform addition polymerization resin (A) with a narrow monomer composition distribution. This allows for a wider fixing temperature range while maintaining excellent low-temperature fixing properties, and further improves heat resistance, storage properties, and pulverability.
From the above viewpoint, the temperature for bulk polymerization is preferably 140°C or higher, more preferably 180°C or higher, even more preferably 220°C or higher, even more preferably 260°C or higher, even more preferably 280°C or higher, and preferably 350°C or lower, more preferably 320°C or lower.

The acid value of the addition polymerization resin (A) is preferably 40 mg KOH/g or more, more preferably 43 mg KOH/g or more, more preferably 46 mg KOH/g or more, even more preferably 48 mg KOH/g or more, even more preferably 50 mg KOH/g or more, even more preferably 60 mg KOH/g or more, even more preferably 70 mg KOH/g or more, even more preferably 80 mg KOH/g or more, and preferably 300 mg KOH/g or less, more preferably 200 mg KOH/g or less, even more preferably 150 mg KOH/g or less, and even more preferably 100 mg KOH/g or less.

The weight-average molecular weight of the addition polymerization resin (A) is preferably 5,000 or more, more preferably 6,000 or more, even more preferably 7,000 or more, even more preferably 8,000 or more, even more preferably 9,000 or more, and also preferably 200,000 or less, more preferably 100,000 or less, even more preferably 50,000 or less, even more preferably 30,000 or less, even more preferably 20,000 or less, even more preferably 15,000 or less, and even more preferably 13,000 or less, from the viewpoint of broadening the fixing temperature range while maintaining excellent low-temperature fixing properties, and from the viewpoint of improving heat resistance and productivity.
The weight-average molecular weight of the addition polymerization resin (A) can be adjusted by the polymerization temperature and polymerization time.

The glass transition temperature of the addition polymerization resin (A) is preferably 45°C or higher, more preferably 50°C or higher, even more preferably 55°C or higher, even more preferably 60°C or higher, and preferably 120°C or lower, more preferably 90°C or lower, even more preferably 80°C or lower, and even more preferably 70°C or lower, from the viewpoint of broadening the fixing temperature range while maintaining excellent low-temperature fixing properties, and from the viewpoint of further improving heat resistance and productivity.
The softening point of the addition polymerization resin (A) is preferably 90°C or higher, more preferably 100°C or higher, even more preferably 105°C or higher, even more preferably 110°C or higher, and preferably 160°C or lower, more preferably 140°C or lower, and even more preferably 130°C or lower, from the viewpoint of broadening the fixing temperature range while maintaining excellent low-temperature fixing properties, and from the viewpoint of further improving heat resistance and productivity.
The acid value, weight-average molecular weight, glass transition temperature, and softening point of the addition polymerization resin (A) can be measured by the method described in the examples.

[Polyester resin (B)]
The polyester resin (B) is a polyester resin that constitutes a polyester resin unit of a composite resin, preferably containing a polycondensate of an alcohol component (b-al) and a carboxylic acid component (b-ac) as the raw material monomer (b), from the viewpoint of broadening the fixing temperature range while maintaining excellent low-temperature fixing properties, as well as improving heat resistance and pulverability.

(Raw material monomer (b))
The raw material monomer (b) is a component of the polyester resin (B), and preferably contains an alcohol component (b-al) and a carboxylic acid component (b-ac).

[Alcohol content (b-al)]
The alcohol component (b-al) includes diols such as aromatic diols, aliphatic diols, and alicyclic diols, as well as polyhydric alcohols with a valency of three or higher.
Examples of aromatic diols include alkylene oxide adducts of bisphenol A [2,2-bis(4-hydroxyphenyl)propane] (hereinafter also referred to as "BPA-AO"). Preferably, BPA-AO is of formula (I):

Examples of BPA-AOs include those represented by the formula [wherein OR ¹¹ and R ¹² O are alkylene oxy groups, R ¹¹ and R ¹² are each independently alkylene groups (preferably ethylene or propylene groups) having 1 to 4 carbon atoms, x and y are the average number of moles of alkylene oxide added, each independently being a positive number, and the average value of the sum of x and y is preferably 1 or more, more preferably 1.5 or more, even more preferably 2 or more, and preferably 16 or less, more preferably 8 or less, and even more preferably 4 or less.].

Examples of BPA-AO include polyoxypropylene (2,2)-2,2-bis(4-hydroxyphenyl)propane, polyoxypropylene (3.3)-2,2-bis(4-hydroxyphenyl)propane, polyoxyethylene (2.2)-2,2-bis(4-hydroxyphenyl)propane, polyoxyethylene (2.0)-2,2-bis(4-hydroxyphenyl)propane, polyoxypropylene (2.0)-polyoxyethylene (2.0)-2,2-bis(4-hydroxyphenyl)propane, and polyoxypropylene (6)-2,2-bis(4-hydroxyphenyl)propane.
The numbers in parentheses above correspond to the average value of the sum of x and y in equation (I) above.

The BPA-AO is preferably one or more selected from the propylene oxide adduct of bisphenol A (hereinafter also referred to as "BPA-PO") and the ethylene oxide adduct of bisphenol A (hereinafter also referred to as "BPA-EO"). One or more of these BPA-AOs may be used.
Furthermore, BPA-AO may be used in combination with BPA-PO and BPA-EO.

The aliphatic diol has two or more carbon atoms, preferably 18 or fewer, more preferably 14 or fewer, even more preferably 10 or fewer, and even more preferably 6 or fewer.
Examples of aliphatic diols include ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, neopentyl glycol, 1,4-butenediol, 1,5-pentanediol, 1,6-hexanediol, diethylene glycol, triethylene glycol, polyethylene glycol, dipropylene glycol, polypropylene glycol, and polytetramethylene glycol.

Examples of alicyclic diols include 1,4-cyclohexanedimethanol, hydrogenated bisphenol A, and alkylene oxide adducts of hydrogenated bisphenol A with 2 to 4 carbon atoms (average number of added moles: 2 to 12).

Examples of polyhydric alcohols with a valency of 3 or higher include sorbitol, 1,2,3,6-hexanetetrol, 1,4-sorbitan, pentaerythritol, dipentaerythritol, tripentaerythritol, 1,2,4-butanetriol, 1,2,5-pentanetriol, glycerol, 2-methylpropanetriol, 2-methyl-1,2,4-butanetriol, trimethylolethane, trimethylolpropane, and 1,3,5-trihydroxymethylbenzene.
Furthermore, from the viewpoint of adjusting the molecular weight and softening point of the resin, the alcohol component (b-al) may include a monohydric alcohol.
These alcohol components may be used individually or in combination of two or more types.

The alcohol component (b-al) preferably comprises one or more selected from among these: alkylene oxide adducts of bisphenol A, ethylene glycol, 1,2-propanediol, 1,3-propanediol, and neopentyl glycol, and more preferably comprises alkylene oxide adducts of bisphenol A (BPA-AO).
The amount of BPA-AO 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 100 mol% or less, and even more preferably 100 mol%, relative to the alcohol component (b-al).
When BPA-PO and BPA-EO are used in combination as BPA-AO, the amount of BPA-PO in the total amount of BPA-PO and BPA-EO is preferably 20 mol% or more, more preferably 30 mol% or more, even more preferably 40 mol% or more, even more preferably 50 mol% or more, and 100 mol% or less.

[Carboxylic acid component (b-ac)]
Examples of carboxylic acid components (b-ac) include dicarboxylic acid compounds and polycarboxylic acid compounds with a valency of three or more.

Examples of dicarboxylic acid compounds include aromatic dicarboxylic acid compounds, aliphatic dicarboxylic acid compounds, and alicyclic dicarboxylic acid compounds.
The number of carbon atoms in the dicarboxylic acid compound is preferably 2 or more, more preferably 3 or more, and preferably 30 or less, more preferably 20 or less.
Examples of aromatic dicarboxylic acid compounds include phthalic acid, isophthalic acid, and terephthalic acid. Among these, isophthalic acid and terephthalic acid are preferred, and terephthalic acid is more preferred.
Examples of aliphatic dicarboxylic acid compounds include oxalic acid, malonic acid, maleic acid, fumaric acid, citraconic acid, itaconic acid, glutaconic acid, succinic acid, pentaneoic acid, adipic acid, sebacic acid, dodecaneoic acid, azelaic acid, and succinic acid substituted with an aliphatic hydrocarbon group having 1 to 20 carbon atoms.
Examples of succinic acids substituted with aliphatic hydrocarbon groups having 1 to 20 carbon atoms include n-dodecenyl succinic acid, isododecenyl succinic acid, n-dodecyl succinic acid, isododecyl succinic acid, n-octenyl succinic acid, n-octyl succinic acid, isooctenyl succinic acid, and isooctyl succinic acid.
Examples of alicyclic dicarboxylic acids include cyclohexanedicarboxylic acid.

Examples of polycarboxylic acid compounds with three or more valent carboxylic acids include 1,2,4-benzenetricarboxylic acid (trimellitic acid), 2,5,7-naphthalentricarboxylic acid, and pyromellitic acid.

The carboxylic acid component (b-ac) preferably comprises one or more selected from terephthalic acid, isophthalic acid, maleic acid, fumaric acid, alkenyl succinic acid, and trimellitic acid, more preferably comprises one or more selected from terephthalic acid, isophthalic acid, fumaric acid, and trimellitic acid, and even more preferably comprises one or more aromatic dicarboxylic acid compounds selected from terephthalic acid and isophthalic acid.
The amount of aromatic dicarboxylic acid compound is preferably 50 mol% or more, more preferably 70 mol% or more, even more preferably 90 mol% or more, even more preferably 95 mol% or more, and 100 mol% or less, and even more preferably 100 mol%, in the carboxylic acid component (b-ac).

Furthermore, the carboxylic acid component (b-ac) may appropriately contain polycarboxylic acid compounds of trivalent or higher valentity, from the viewpoint of controlling the degree of polymerization of the resin.

The equivalent ratio [COOH group/OH group] of the carboxyl group (COOH group) of the carboxylic acid component (b-ac) to the hydroxyl group (OH group) of the alcohol component (b-al) is preferably 0.5 or higher, more preferably 0.6 or higher, even more preferably 0.7 or higher, and preferably 1.2 or lower, more preferably 1.0 or lower, and even more preferably 0.9 or lower.

(Polyethylene terephthalate)
The polyester resin (B) is preferably a condensate of polyethylene terephthalate (hereinafter also referred to as "PET") and raw material monomer (b), from the viewpoint of broadening the fixing temperature range while maintaining excellent low-temperature fixing properties, as well as improving heat resistance and pulverability.
PET is a polycondensate of ethylene glycol and terephthalic acid, dimethyl terephthalate, etc., and is a component incorporated into polyester resin (B) through condensation of the terminal functional groups of PET with the raw material monomer (b). During condensation with the raw material monomer (b), PET may depolymerize, potentially producing ethylene glycol, terephthalic acid, or decomposed polymer chains, which can become components of polyester resin (B).

The intrinsic viscosity of PET (hereinafter also referred to as "IV value") is preferably 0.4 or higher, more preferably 0.45 or higher, even more preferably 0.5 or higher, even more preferably 0.55 or higher, even more preferably 0.6 or higher, and preferably 0.8 or lower, more preferably 0.75 or lower, and even more preferably 0.7 or lower, from the viewpoint of further improving pulverability. The IV value is an indicator of molecular weight. The IV value of PET can be adjusted by the molar ratio of the raw material monomers, the polycondensation time, etc.
The IV value can be measured, for example, by dissolving the sample at a concentration of 0.4 g/dL in a phenol/tetrachloroethane = 60/40 (mass ratio) mixed solvent, measuring it with an Ubbelohde viscometer, and calculating it according to the following formula.

[In the formula, k is Huggins' constant, C is the concentration of the sample solution (g/dL), η = ( _t1 / _t0 ) - 1, _t0 is the number of seconds for the solvent only to fall, and _t1 is the number of seconds for the sample solution to fall. Assume k is 0.33.]

PET can be manufactured according to conventional methods or is a commercially available product.
Examples of commercially available PET products include "RAMAPET BF3067" (IV value: 0.64), "RAMAPET L1" (IV value: 0.60), and "RAMAPET N2G" (IV value: 0.75) from Indorama Ventures; and "TRN-NTJ" (IV value: 0.53) and "TRN-RTJC" (IV value: 0.64) from Teijin Limited.

In the polyester resin (B), the amount of PET component is preferably 5 moles or more, more preferably 7 moles or more, even more preferably 10 moles or more, and preferably 50 moles or less, more preferably 40 moles or less, and even more preferably 30 moles or less, based on 100 moles of the total amount of PET component and alcohol component (b-al), from the viewpoint of widening the fixing temperature range while maintaining excellent low-temperature fixing properties, and from the viewpoint of further improving heat resistance, storage properties, and pulverability.
The number of moles of the PET component is calculated as the number of moles of the condensation unit of ethylene glycol and terephthalic acid.

The amount of addition polymerization resin (A) in the composite resin according to the present invention is preferably 1 part by mass or more, more preferably 2 parts by mass or more, even more preferably 3 parts by mass or more, even more preferably 4 parts by mass or more, per 100 parts by mass of polyester resin (B), from the viewpoint of broadening the fixing temperature range while maintaining excellent low-temperature fixing properties, and from the viewpoint of further improving heat resistance, storage properties, and productivity.

The softening point of the composite resin according to the present invention is preferably 70°C or higher, more preferably 80°C or higher, even more preferably 90°C or higher, even more preferably 100°C or higher, and preferably 170°C or lower, more preferably 150°C or lower, even more preferably 140°C or lower, even more preferably 135°C or lower, even more preferably 130°C or lower, even more preferably 120°C or lower, and even more preferably 115°C or lower.
The glass transition temperature of the composite resin according to the present invention is preferably 50°C or higher, more preferably 53°C or higher, and preferably 80°C or lower, more preferably 70°C or lower, and even more preferably 60°C or lower.
The acid value of the composite resin according to the present invention is preferably 50 mg KOH/g or less, more preferably 40 mg KOH/g or less, even more preferably 30 mg KOH/g or less, even more preferably 20 mg KOH/g or less, even more preferably 15 mg KOH/g or less, and preferably 2 mg KOH/g or more, more preferably 3 mg KOH/g or more.
The hydroxyl value of the composite resin according to the present invention is preferably 10 mg KOH/g or more, more preferably 20 mg KOH/g or more, even more preferably 30 mg KOH/g or more, even more preferably 40 mg KOH/g or more, and preferably 80 mg KOH/g or less, more preferably 70 mg KOH/g or less, even more preferably 60 mg KOH/g or less, and even more preferably 55 mg KOH/g or less.
The softening point, glass transition temperature, acid value, and hydroxyl value of the composite resin according to the present invention can be easily adjusted to these ranges by adjusting the type and amount of raw material monomers, the amount of radical generator, the amount of catalyst, etc., or by selecting reaction conditions.
The softening point, glass transition temperature, acid value, and hydroxyl value of the composite resin according to the present invention can be measured by the method described in the examples.

From the viewpoint of broadening the fixing temperature range while maintaining excellent low-temperature fixing properties, and from the viewpoint of further improving heat resistance, storage properties, and productivity, it is preferable that the binder resin of the present invention contains the composite resin as an amorphous polyester resin.

The binder resin of the present invention preferably contains two or more amorphous polyester resins with different softening points, preferably 5°C or higher, more preferably 10°C or higher, from the viewpoint of broadening the fixing temperature range while maintaining excellent low-temperature fixing properties, and from the viewpoint of further improving heat resistance, storage properties, and productivity, and it is even more preferable that the composite resin is contained as an amorphous polyester resin having a low softening point.
Among two or more amorphous polyester resins, the polyester resin having the lowest softening point is preferably 70°C or higher, more preferably 80°C or higher, even more preferably 90°C or higher, and even more preferably 100°C or higher, from the viewpoint of improving heat-resistant storage properties, and preferably 135°C or lower, more preferably 120°C or lower, and even more preferably 115°C or lower, from the viewpoint of improving low-temperature fixing properties.
Among two or more amorphous polyester resins, the polyester resin having the highest softening point is preferably 110°C or higher, more preferably 120°C or higher, from the viewpoint of improving high-temperature offset resistance, and preferably 170°C or lower, more preferably 150°C or lower, and even more preferably 140°C or lower, from the viewpoint of improving low-temperature fixation.
From the viewpoint of improving toner productivity, it is preferable to use two types of binder resins in the present invention: an amorphous polyester resin with a high softening point and an amorphous polyester resin with a low softening point.
From the viewpoint of high-softening-point polyester resin and low-softening-point polyester resin, the difference in softening points is preferably 5°C or higher, more preferably 7°C or higher, and even more preferably 10°C or higher. From the viewpoint of low-temperature fixability and heat-resistant storage, it is preferably 60°C or lower, more preferably 50°C or lower, even more preferably 40°C or lower, even more preferably 30°C or lower, and even more preferably 25°C or lower.

The content of the composite resin in the binder resin of the present invention is preferably 50% by mass or more, more preferably 55% by mass or more, even more preferably 60% by mass or more, and also 100% by mass or less, preferably 90% by mass or less, more preferably 80% by mass or less, and even more preferably 70% by mass or less, from the viewpoint of broadening the fixing temperature range while maintaining excellent low-temperature fixing properties, and further improving heat resistance and productivity.

<Amorphous polyester resin>
The binder resin of the present invention preferably further contains an amorphous polyester resin, from the viewpoint of broadening the fixing temperature range while maintaining excellent low-temperature fixing properties, and from the viewpoint of further improving heat resistance and productivity.
The amorphous polyester resin preferably has a softening point different from that of the composite resin, and more preferably has a softening point higher than that of the composite resin. That is, the binder resin of the present invention preferably contains the composite resin as an amorphous polyester resin with a low softening point and the amorphous polyester resin as an amorphous polyester resin with a high softening point. In this case, the difference between the softening point of the composite resin and the softening point of the amorphous polyester resin is preferably within the same range as the difference between the softening points of the high softening point polyester resin and the low softening point polyester resin.

The amorphous polyester resin is preferably an amorphous polyester resin which is a condensate of an alcohol component and a carboxylic acid component.
Examples of alcohol and carboxylic acid components in amorphous polyester resins are the same as the examples of alcohol (b-al) and carboxylic acid components (b-ac) in the polyester resin (B) described above.
BPA-AO is preferred as the alcohol component of the amorphous polyester resin.
BPA-AO is preferably one or more selected from BPA-PO and BPA-EO.
As the carboxylic acid component of amorphous polyester resins, aromatic dicarboxylic acid compounds, aliphatic dicarboxylic acid compounds, and polycarboxylic acid compounds with a valency of three or higher are preferred.
As aromatic dicarboxylic acid compounds, terephthalic acid and isophthalic acid are preferred, with terephthalic acid being more preferred.
The amount of aromatic dicarboxylic acid compound is preferably 20 mol% or more, more preferably 40 mol% or more, even more preferably 60 mol% or more, and preferably 90 mol% or less, more preferably 80 mol% or less, and even more preferably 70 mol% or less, in the carboxylic acid component.
Preferred aliphatic dicarboxylic acid compounds include maleic acid, fumaric acid, and alkenyl succinic acid, with alkenyl succinic acid being more preferred.
The amount of aliphatic dicarboxylic acid compound is preferably 1 mol% or more, more preferably 3 mol% or more, even more preferably 5 mol% or more, and preferably 20 mol% or less, more preferably 15 mol% or less, and even more preferably 10 mol% or less, relative to the carboxylic acid component.
As the polycarboxylic acid compound with a valency of 3 or higher, trimellitic acid or its anhydride is preferred.
The amount of trivalent or higher polycarboxylic acid compounds is preferably 5 mol% or more, more preferably 10 mol% or more, even more preferably 20 mol% or more, and preferably 40 mol% or less, more preferably 35 mol% or less, and even more preferably 30 mol% or less, in the carboxylic acid component.

(Physical properties of amorphous polyester resins)
The softening point of amorphous polyester resin is preferably 90°C or higher, more preferably 100°C or higher, even more preferably 110°C or higher, even more preferably 120°C or higher, even more preferably above 120°C, and preferably 170°C or lower, more preferably 150°C or lower, and even more preferably 130°C or lower.
When the softening point of the composite resin is 80°C or higher and 120°C or lower, the softening point of the amorphous polyester resin is preferably above 120°C, more preferably above 123°C, and preferably below 170°C, more preferably below 150°C, and even more preferably below 130°C.

The glass transition temperature of amorphous polyester resins is preferably 40°C or higher, more preferably 45°C or higher, even more preferably 50°C or higher, and preferably 90°C or lower, more preferably 80°C or lower, and even more preferably 70°C or lower.

The acid value of the amorphous polyester resin is preferably 2 mg KOH/g or more, more preferably 5 mg KOH/g or more, even more preferably 10 mg KOH/g or more, and preferably 40 mg KOH/g or less, more preferably 30 mg KOH/g or less, and even more preferably 20 mg KOH/g or less.
The hydroxyl value of the amorphous polyester resin is preferably 10 mg KOH/g or more, more preferably 20 mg KOH/g or more, even more preferably 30 mg KOH/g or more, and preferably 50 mg KOH/g or less, more preferably 45 mg KOH/g or less, and even more preferably 40 mg KOH/g or less.

The softening point, glass transition temperature, acid value, and hydroxyl value of amorphous polyester resins can be appropriately adjusted depending on the type of raw material monomer, its molar ratio, and manufacturing conditions such as reaction temperature, reaction time, and cooling rate. These values can be determined by the method described in the examples below. When using two or more amorphous polyester resins in combination, it is preferable that the physical properties obtained from the mixture are within the aforementioned ranges.

The content of amorphous polyester resin in the binder resin of the present invention is preferably 10% by mass or more, more preferably 20% by mass or more, even more preferably 30% by mass or more, and preferably 50% by mass or less, more preferably 45% by mass or less, and even more preferably 40% by mass or less.
The mass ratio [composite resin/amorphous polyester resin] of the composite resin to the amorphous polyester resin contained in the binder resin of the present invention is preferably 0.5 or more, more preferably 1.0 or more, even more preferably 1.5 or more, even more preferably 1.7 or more, and preferably 4.0 or less, more preferably 3.0 or less, and even more preferably 2.0 or less.

<Crystalline polyester resin>
The binder resin of the present invention preferably further contains a crystalline polyester resin, from the viewpoint of broadening the fixing temperature range while maintaining excellent low-temperature fixing properties, and from the viewpoint of further improving heat resistance and productivity.
Examples of crystalline polyester resins include crystalline composite resins having a crystalline polyester resin, a polyester resin segment, and a vinyl resin segment. Examples of crystalline polyester resins include polycondensates of an alcohol component containing an α,ω-aliphatic diol having 2 to 16 carbon atoms and a carboxylic acid component containing an aliphatic dicarboxylic acid compound having 2 to 14 carbon atoms. Specifically, examples of crystalline polyester resins include those described in Japanese Patent Application Publication No. 2016-45358.

The content of crystalline polyester resin in the binder resin of the present invention is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, even more preferably 1% by mass or more, even more preferably 3% by mass or more, and preferably 20% by mass or less, more preferably 10% by mass or less, and even more preferably 7% by mass or less.

The total content of the composite resin, amorphous polyester resin, and crystalline polyester resin in the binder resin of the present invention is preferably 80% by mass or more, more preferably 90% by mass or more, even more preferably 98% by mass or more, and 100% by mass or less, from the viewpoint of broadening the fixing temperature range while maintaining excellent low-temperature fixing properties, and from the viewpoint of further improving heat resistance and pulverability.
The mass ratio of the total content of composite resin and amorphous polyester resin to the content of crystalline polyester resin in the binder resin of the present invention [(total content of composite resin and amorphous polyester resin) / (content of crystalline polyester resin)] is preferably 70/30 or more, more preferably 80/20 or more, even more preferably 90/10 or more, and from the viewpoint of low-temperature fixation, it is preferably 98/2 or less, more preferably 97/3 or less, and even more preferably 96/4 or less.

[Manufacturing method for binder resin for toner]
The binder resin of the present invention can be manufactured by a method that includes the step of compounding an addition polymerization resin (A) constituting an addition polymerization resin unit and a polyester resin (B) constituting a polyester resin unit by covalent bonding to obtain the composite resin.

<Manufacturing of composite resins>
The compounding of the addition polymerization resin (A) and the polyester resin (B) is preferably carried out by forming a covalent bond via a compound that can react with either resin (A) or resin (B) (hereinafter also referred to as "both reactive compounds"), from the viewpoint of ensuring sufficient compounding, widening the fixing temperature range while maintaining excellent low-temperature fixing properties, and further improving heat resistance and productivity. The both reactive compounds are preferably compounds that can react with either the raw material monomers constituting the addition polymerization resin (A) or the polyester resin (B), and examples include those represented by the following general formulas (II-1) and (II-2).

[In the formula, R ²¹ , R ²² , and R ²³ are the same or different and represent a hydrogen atom, a hydroxyl group, an optionally substituted alkyl group, an alkoxy group, an aryl group, a vinyl group, or a halogen atom, which may be bonded to each other to form a ring. A and B are the same or different and represent a group represented by the following general formula (III-1), general formula (III-2), or general formula (III-3). X and Y are the same or different and represent -COOR ⁴ (where R ⁴ represents a hydrogen atom or an optionally substituted lower alkyl group).]

[In the formula, R ³¹ , R ³² , and R ³³ are the same or different and represent a hydrogen atom, a hydroxyl group, an optionally substituted alkyl group, alkoxy group, aryl group, vinyl group, or halogen atom, which may be bonded to each other to form a ring. m represents a number between 0 and 5, and n represents a number between 0 and 2.]

Here, it is preferable that both reactive compounds can react with either the raw material monomers of the addition polymerization resin (A) or the polyester resin (B). However, if there are two or more raw material monomers for each of the addition polymerization resin (A) and the polyester resin (B), it is sufficient that they can react with at least one of them.

In general formulas (II-1), (II-2), and (III-1) to (III-3), specific examples or preferred embodiments of alkyl groups, alkoxy groups, aryl groups, vinyl groups, and halogen atoms represented by R ²¹ to R ²³ and R ³¹ to R ³³ are as follows.
The alkyl group is a linear or branched group having 1 to 6 carbon atoms, preferably 1 to 4 carbon atoms. Examples include methyl, ethyl, n-propyl, i-propyl, n-butyl, and tert-butyl groups. These alkyl groups may be substituted with phenyl, naphthyl, or hydroxyl groups.
Examples of alkoxy groups include methoxy groups, ethoxy groups, n-propoxy groups, i-propoxy groups, and t-butoxy groups, and these groups may be substituted with hydroxyl groups, carboxyl groups, etc.
Examples of aryl groups include phenyl, benzyl, and naphthyl groups, and these groups may be substituted with methyl, ethyl, methoxy, ethoxy, carboxyl, or hydroxyl groups.
The vinyl group may be substituted with, for example, a hydroxyl group, a phenyl group, an alkyl group, an alkoxy group, or a carboxyl group.
Examples of halogen atoms include fluorine, chlorine, bromine, and iodine atoms, with chlorine and bromine atoms being preferred.
The lower alkyl group represented by ^R4 preferably has 1 to 4 carbon atoms, and examples include methyl groups and ethyl groups, and these groups may be substituted with hydroxyl groups or the like.

When X is a carboxyl group in general formula (II-2), examples of compounds represented by general formula (II-2) include the ethylenically unsaturated monocarboxylic acid compounds represented by the following general formulas (IV-1) to (IV-3).

[In the formula, R ⁴¹ and R ⁴² represent a hydrogen atom, an optionally substituted alkyl group, aryl group, vinyl group, or halogen atom, similar to R ²¹ to R ^23. R ⁴³ and R ⁴⁴ are the same or different, similar to R ²¹ to R ²³ , representing an optionally substituted alkyl group, aryl group, vinyl group, or halogen atom. A is the same as described above.]

Specific examples of ethylenically unsaturated monocarboxylic acid compounds represented by general formulas (IV-1) to (IV-3) include acrylic acid, methacrylic acid, crotonic acid, cinnamic acid, and their lower alkyl esters and anhydrides.

When X and Y are carboxyl groups in general formula (II-1), examples of compounds represented by general formula (II-1) include ethylenically unsaturated dicarboxylic acid compounds represented by the following general formulas (V-1) and (V-2).

[In the formula, R ⁵¹ and R ⁵² represent a hydrogen atom, an optionally substituted alkyl group, aryl group, vinyl group, or halogen atom, similar to R ²¹ to R ^23. A and B are the same as described above.]

Specific examples of ethylenically unsaturated dicarboxylic acid compounds represented by general formulas (V-1) and (V-2) include maleic acid, fumaric acid, itaconic acid, mesaconic acid, citraconic acid, and their lower alkyl esters and anhydrides.

The reactive compounds are preferably ethylenically unsaturated monocarboxylic acid compounds, and more preferably one or more selected from acrylic acid and methacrylic acid, from the viewpoint of ensuring sufficient compounding, broadening the fixing temperature range while maintaining excellent low-temperature fixing properties, and further improving heat resistance, storage properties, and productivity.
It is preferable to introduce both reactive compounds into the polymer backbone as raw material monomers for either the addition polymerization resin (A) or the polyester resin (B) before compounding, and then compound them with the other resin via the reactive compounds. From the viewpoint of ensuring sufficient compounding, it is even more preferable to introduce them into the polymer backbone as raw material monomer (a) for the addition polymerization resin (A) before compounding, and then compound them with the polyester resin (B) via the reactive compounds.

The amount of both reactive compounds, which can react with either the addition polymerization resin (A) or the polyester resin (B), is preferably 0.5% by mass or more, more preferably 3% by mass or more, even more preferably 5% by mass or more, and preferably 40% by mass or less, more preferably 30% by mass or less, even more preferably 20% by mass or less, and even more preferably 15% by mass or less, in the raw material monomer (a) of the addition polymerization resin (A) constituting the addition polymerization resin unit.

Methods for compounding an addition polymerization resin (A) and a polyester resin (B) include: (i) a polymer reaction between the addition polymerization resin (A) and the polyester resin (B); (ii) a reaction of the components of the polyester resin (B) in the presence of the addition polymerization resin (A); and (iii) a reaction in which a portion of the components of the polyester resin (B) are reacted, and then the remaining components of the addition polymerization resin (A) and polyester resin (B) are added to carry out the reaction.

In method (i), it is preferable that the polymerization reactions of the addition polymerization resin (A) and the polyester resin (B) are carried out in independent reaction systems. It is preferable that the polymerization system for the addition polymerization resin (A) is of the addition polymerization type, and the polymerization system for the polyester resin (B) is of the polycondensation type. As long as the polymerization reactions of the addition polymerization resin (A) and the polyester resin (B) are in independent reaction systems, the progress and completion of the two polymerization reactions do not need to be simultaneous in time; the reaction temperature and time can be appropriately selected according to the respective reaction mechanisms to allow the reactions to proceed and be completed.
Furthermore, in the polymer reaction of method (i), there are no particular restrictions on the method of mixing the addition polymerization resin (A) and the polyester resin (B). For example, one method is to isolate the polyester resin (B) obtained by condensing the raw material monomer (b) and optionally PET, and then mix the polyester resin (B) with the addition polymerization resin (A). Another method is to add and mix the addition polymerization resin (A) without isolating the polyester resin (B) obtained by condensing the raw material monomer (b) and optionally PET. In method (i), PET may be produced in the reaction system by polycondensation of ethylene glycol with terephthalic acid, dimethyl terephthalate, etc., or the aforementioned commercially available product may be used.

In method (ii), the components of the polyester resin (B) reacted in the presence of the addition polymerization resin (A) may be the raw material monomer (b), or the raw material monomer (b) and PET.

In method (iii), a method is used in which the alcohol component (b-al) is reacted with a portion of the carboxylic acid component (b-ac), and then the addition polymerization resin (A) and the remainder of the carboxylic acid component (b-ac) are added to carry out the reaction. If the polyester resin (B) is a condensate of PET and the raw material monomer (b), it is preferable to add PET during either the reaction between the alcohol component (b-al) and a portion of the carboxylic acid component (b-ac), or the reaction between the addition polymerization resin (A) and the remainder of the carboxylic acid component (b-ac). Furthermore, in method (iii), PET may be produced in the reaction system by polycondensation of ethylene glycol with terephthalic acid, dimethyl terephthalate, etc., or the aforementioned commercially available product may be used.

Among these methods, method (i) described above is preferred from the viewpoint of controlling molecular weight, molecular weight distribution, and copolymerizability of monomers, widening the fixing temperature range while maintaining excellent low-temperature fixing properties, and improving heat resistance and pulverability. In other words, the binder resin of the present invention is preferably produced by a method comprising the following steps I and II.
Step I: A step in which raw material monomer (a) is polymerized to obtain an addition polymerization resin (A). Step II: A step in which an alcohol component (b-al) and a carboxylic acid component (b-ac) are reacted, and then the addition polymerization resin (A) obtained in Step I is added and the reaction is carried out to obtain the composite resin.

Step I is as described above for the addition polymerization resin (A).
In step II, the reaction between the alcohol component (b-al) and the carboxylic acid component (b-ac) is preferably a transesterification reaction and a condensation reaction.
Furthermore, if the polyester resin (B) is a condensate of PET and raw material monomer (b), it is preferable that step II is a step in which PET, an alcohol component (b-al), and a carboxylic acid component (b-ac) are reacted, and then the addition polymerization resin (A) obtained in step I is added and the reaction is carried out to obtain the composite resin (hereinafter also referred to as "step II'").
In step II', a transesterification reaction occurs between ethylene glycol and terephthalic acid, which are the raw material monomers for PET, and the alcohol component (b-al) and the carboxylic acid component (b-ac). This improves the compatibility between the PET chains constituting the polyester resin (B) and the polymer chains formed by the polycondensation of the alcohol component (b-al) and the carboxylic acid component (b-ac).

In step II or step II', the reaction of the alcohol component (b-al), the carboxylic acid component (b-ac), and PET used as needed, and the reaction after the addition polymerization resin (A), may optionally involve the use of an esterification catalyst such as tin(II) 2-ethylhexanoate, dibutyltin oxide, or titanium diisopropylate bistriethanolamine in an amount of 0.01 to 5 parts by mass per 100 parts by mass of the total amount of components of the polyester resin (B); and an esterification co-catalyst such as gallic acid (same as 3,4,5-trihydroxybenzoic acid) in an amount of 0.001 to 0.5 parts by mass per 100 parts by mass of the total amount of components of the polyester resin (B).
Furthermore, when using a monomer having an unsaturated bond, such as fumaric acid, as the raw material monomer (b), a radical polymerization inhibitor may be used, preferably in an amount of 0.001 parts by mass or more and 0.5 parts by mass or less, per 100 parts by mass of the total amount of components of the polyester resin (B), as needed. An example of a radical polymerization inhibitor is 4-tert-butylcatechol.
The reaction temperature in step II or step II' is preferably 120°C or higher, more preferably 160°C or higher, even more preferably 180°C or higher, and preferably 260°C or lower, more preferably 240°C or lower. The reaction in step II or step II' may be carried out in an inert gas atmosphere.

If the binder resin of the present invention further contains the amorphous polyester resin and the crystalline polyester resin in addition to the composite resin, it is preferable to include a step of adding and mixing these resins to the composite resin obtained in step II.

[Toner for developing electrostatic images]
The electrostatic image developing toner of the present invention (hereinafter also referred to as "the toner of the present invention") contains the binder resin, and preferably contains a colorant and the binder resin.
The toner of the present invention contains, for example, toner particles and an external additive.
The toner particles include the binder resin, and preferably include a colorant and the binder resin.
Furthermore, the toner particles may contain, for example, colorant derivatives, charge control agents, release agents such as waxes, and other additives.
The content of the binder resin in the toner is preferably 80% by mass or more, more preferably 85% by mass or more, even more preferably 87% by mass or more, and 100% by mass or less.
The content of the composite resin in the toner is preferably 40% by mass or more, more preferably 45% by mass or more, even more preferably 50% by mass or more, and preferably 80% by mass or less, more preferably 70% by mass or less, and even more preferably 60% by mass or less.

<Coloring agents>
The coloring agent may be either a pigment or a dye.
Examples of colorants include various types of carbon black produced by methods such as the thermal black method, acetylene black method, channel black method, and lamp black method; grafted carbon black, in which the surface of carbon black is coated with resin; nigrosine dyes; phthalocyanine blue, permanent brown FG, brilliant first scarlet, pigment green B, pigment blue 15:3, rhodamine-B base, solvent red 49, solvent red 146, solvent blue 35, and mixtures thereof.
From the viewpoint of improving the image density of the toner, the amount of colorant is preferably 1 part by mass or more, more preferably 2 parts by mass or more, and preferably 20 parts by mass or less, and more preferably 17 parts by mass or less, per 100 parts by mass of the binder resin.

<Charge Control Agent>
The toner of the present invention may contain a charge control agent. The charge control agent may contain either a positively charged charge control agent or a negatively charged charge control agent.
These charge control agents may be used individually or in combination of two or more types.

Examples of positively charged charge control agents include nigrosine dyes, triphenylmethane-based dyes containing tertiary amines as side chains, quaternary ammonium salt compounds, polyamine resins, imidazole derivatives, and styrene-acrylic resins.
Examples of nigrosine dyes include "Nigrosine Base EX,""Oil Black BS,""Oil Black SO,""BontronN-01,""BontronN-07," and "Bontron N-11" (all manufactured by Orient Chemical Industry Co., Ltd.). Examples of quaternary ammonium salt compounds include "Bontron P-51" (manufactured by Orient Chemical Industry Co., Ltd.), cetyltrimethylammonium bromide, and "COPY CHARGE PX VP435" (manufactured by Hoechst). An example of a polyamine resin is "AFP-B" (manufactured by Orient Chemical Industry Co., Ltd.). Examples of imidazole derivatives include "PLZ-2001" and "PLZ-8001" (both manufactured by Shikoku Chemicals, Inc.). An example of a styrene-acrylic resin is "FCA-701PT" (manufactured by Fujikura Chemicals, Inc.).

Specific examples of negatively charged charge control agents include, for example, metal-containing azo dyes, metal compounds of benzyl acid compounds, metal compounds of salicylic acid compounds, copper phthalocyanine dyes, quaternary ammonium salts, nitroimidazole derivatives, and organometallic compounds.
Examples of metal-containing azo dyes include "Barifast Black 3804" and "Bontron S-31" (both manufactured by Orient Chemical Co., Ltd.), "T-77" (manufactured by Hodogaya Chemical Co., Ltd.), "Bontron S-32", "Bontron S-34", and "Bontron S-36" (all manufactured by Orient Chemical Co., Ltd.), and "Eisenspiron Black TRH" (manufactured by Hodogaya Chemical Co., Ltd.). Examples of metal compounds of salicylic acid compounds include "Bontron E-81", "Bontron E-82", "Bontron E-84", and "Bontron E-85" (all manufactured by Orient Chemical Co., Ltd.). An example of a quaternary ammonium salt is "COPY CHARGE NX VP434" (manufactured by Hoechst). An example of an organometallic compound is "TN105" (manufactured by Hodogaya Chemical Co., Ltd.).

The charge control agent content is preferably 0.1 parts by mass to 8 parts by mass, more preferably 0.2 parts by mass to 5 parts by mass, per 100 parts by mass of the binder resin.

<Wax>
The toner of the present invention preferably contains a wax such as polyolefin or paraffin wax as an offset prevention agent.
The wax content is preferably 0.5 parts by mass or more and 5 parts by mass or less per 100 parts by mass of the binder resin.
Examples of polyolefins include polyethylene and polypropylene, and those with relatively low molecular weights, particularly those with a molecular weight of 3,000 to 15,000 as determined by vapor permeation, are preferred. Furthermore, those with a softening point of 70°C to 150°C as determined by the ring-spherical method, particularly those with a softening point of 120°C to 150°C, are preferred.

<Other additives>
The toner particles may also contain, as appropriate, other additives such as magnetic powder, fluidity enhancers, conductivity modifiers, reinforcing fillers such as fibrous materials, antioxidants, anti-aging agents, and cleaning performance enhancers.

In the toner of the present invention, the toner particle content is preferably 80% by mass or more, more preferably 90% by mass or more, even more preferably 95% by mass or more, and 100% by mass or less, preferably 99% by mass or less.

The volume median particle size (D ₅₀ ) of the toner particles is preferably 2 μm or larger, more preferably 3 μm or larger, even more preferably 5 μm or larger, and preferably 20 μm or smaller, more preferably 15 μm or smaller, and even more preferably 10 μm or smaller. In this specification, the volume median particle size (D ₅₀ ) means the particle size at which the cumulative volume frequency calculated by volume fraction accounts for 50% when calculated from the smallest particle size.

<External Additives>
The toner of the present invention may contain, for example, toner particles and an external additive, by treating the surface of the toner particles with a property-improving agent such as an external additive in order to improve fluidity. Examples of external additives include fine particles of inorganic materials such as silica, alumina, titania, zirconia, tin oxide, and zinc oxide, and organic fine particles such as resin particles such as melamine resin fine particles and polytetrafluoroethylene resin fine particles. One or more of these may be used. Among these external additives, silica is preferred, and hydrophobic silica treated with a hydrophobic treatment agent is more preferred.

Examples of hydrophobic treatment agents include hexamethyldisilazane (HMDS), dimethyldichlorosilane (DMDS), silicone oil, octyltriethoxysilane (OTES), and methyltriethoxysilane. Among these, hexamethyldisilazane is preferred.

When surface treatment of toner particles is performed using an external additive, the content of the external additive is preferably 0.05 parts by mass or more, more preferably 0.08 parts by mass or more, even more preferably 0.1 parts by mass or more, and preferably 5 parts by mass or less, more preferably 3 parts by mass or less, and even more preferably 2 parts by mass or less, per 100 parts by mass of toner particles, from the viewpoint of the toner's chargeability and fluidity.

[Toner manufacturing method]
The toner of the present invention may be obtained by any known method such as melt-kneading, emulsion-phase inversion, suspension polymerization, or emulsion-coagulation, but from the viewpoint of productivity and dispersibility of colorants, pulverized toner obtained by melt-kneading is preferred.
In the melt-kneading method, after uniformly dispersing the binder resin, colorant, and optionally a property improver, toner can be obtained by melt-kneading, cooling, grinding, and classifying using a known method, with a volume median particle size (D ₅₀ ) of 5 μm or more and 15 μm or less.

The toner of the present invention is used for developing latent images formed in electrophotography, electrostatic recording, electrostatic printing, and the like. This toner can be used as a non-magnetic one-component developer, or as a dry two-component developer by mixing it with carriers such as iron oxide carriers, spherical iron oxide carriers, and ferrite carriers, either directly or coated with resin.

[measurement]
[Acid value and hydroxyl value of resins]
The acid value and hydroxyl value of the resins were measured according to the method of JIS K0070:1992. However, the measurement solvent was changed from the ethanol and ether mixture specified in JIS K0070:1992 to an acetone and toluene mixture [acetone:toluene = 1:1 (volume ratio)] for amorphous resins, and to chloroform for crystalline polyester resins.

[Weight-average molecular weight of resins]
The molecular weight distribution was measured by gel permeation chromatography (GPC), obtained using the following method, and the weight-average molecular weight was determined.
(1) Preparation of sample solution The sample was dissolved in tetrahydrofuran (in the case of amorphous resin) or chloroform (in the case of crystalline polyester resin) at 25°C to a concentration of 0.5 g/100 mL. Then, this solution was filtered using a fluoropolymer filter "DISMIC-25JP" (manufactured by ADVANTEC) with a pore size of 0.2 μm to remove undissolved material and obtain the sample solution.
(2) Molecular weight measurement Using the following measuring apparatus and analytical column, tetrahydrofuran (amorphous resin) or chloroform (crystalline polyester resin) was flowed as the eluent at a flow rate of 1 mL per minute, and the column was stabilized in a constant temperature bath at 40°C. 100 μL of the sample solution was injected into the column and the measurement was performed. The molecular weight of the sample was calculated based on a calibration curve prepared in advance. The calibration curve used in this study was prepared using several types of monodisperse polystyrene as standard samples: "A-500" (5.0 × ^10⁻² ), "A-1000" (1.01 × ^10⁻³ ), "A-2500" (2.63 × ^10⁻³ ), "A-5000" (5.97 × ^10⁻³ ), "F-1" (1.02 × ^10⁴ ), "F-2" (1.81 × ^10⁴ ), "F-4" (3.97 × ^10⁴ ), "F-10" (9.64 × ^10⁴ ), "F-20" (1.90 × ^10⁵ ), "F-40" (4.27 × ^10⁵ ), "F-80" (7.06 × ^10⁵ ), and "F-128" (1.09 × ^10⁶ ) (all manufactured by Tosoh Corporation). The values in parentheses indicate the molecular weight.
Measuring device: "HLC-8220CPC" (manufactured by Tosoh Corporation)
Analysis columns: "GMHXL" + "G3000HXL" (manufactured by Tosoh Corporation)

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

[Maximum peak temperature for endothermic heating]
Using a differential scanning calorimeter "Q-20" (manufactured by T.A. Instruments Japan Co., Ltd.), a sample was cooled from room temperature (20°C) to 0°C at a rate of 10°C/min. The sample was maintained at this temperature for 1 minute, and then measured while the temperature was increased to 180°C at a rate of 10°C/min. The temperature of the largest observed endothermic peak was defined as the maximum endothermic peak temperature.

[Glass transition temperature of amorphous resins]
Using a differential scanning calorimeter "Q-20" (manufactured by T.A. Instruments Japan Co., Ltd.), 0.01 to 0.02 g of the sample was weighed into an aluminum pan, heated to 200°C, and then cooled to 0°C at a rate of 10°C/min. Next, the sample was heated at a rate of 10°C/min, and the temperature at the intersection of the extension of the baseline below the highest endothermic peak temperature and the tangent line showing the maximum slope from the rise of the peak to the peak apex was defined as the glass transition temperature.

[Melting point of crystalline polyester resin]
Using a differential scanning calorimeter "Q-100" (manufactured by T.A. Instruments Japan Co., Ltd.), 0.01 to 0.02 g of the sample was weighed into an aluminum pan and cooled from room temperature to -10°C at a rate of 10°C/min, holding the temperature for 1 minute. Next, the sample was heated to 200°C at a rate of 10°C/min, and then cooled from that temperature to -30°C at a rate of 10°C/min. Next, the sample was heated again at a rate of 10°C/min, and the peak temperature on the highest endothermic side of the observed endothermic peaks was defined as the melting point.

[Melting point of release agent]
Using a differential scanning calorimeter "Q-100" (manufactured by T.A. Instruments Japan Co., Ltd.), 0.02 g of the sample was weighed into an aluminum pan, heated to 200°C, and then cooled from 200°C to 0°C at a rate of 10°C/min. Next, the sample was heated again at a rate of 10°C/min, and the amount of heat was measured. The maximum peak temperature of the obtained endothermic reaction was defined as the melting point.

[Medium volume particle size of toner particles (D ₅₀ )]
The median volume particle size (D ₅₀ ) of the toner particles was measured as follows:
• Measuring device: "Coulter Multisizer (registered trademark) III" (manufactured by Beckman Coulter, Inc.)
Aperture diameter: 50 μm
• Analysis software: "Coulter Multisizer (registered trademark) III version 3.51" (manufactured by Beckman Coulter, Inc.)
• Electrolyte: "Isoton (registered trademark) II" (manufactured by Beckman Coulter, Inc.)
- Dispersion: "Emulgen (registered trademark) 109P" [polyoxyethylene lauryl ether, manufactured by Kao Corporation, HLB (Hydrophile-Lipophile Balance, Griffin method) = 13.6] was dissolved in the electrolyte to obtain a dispersion with a concentration of 5% by mass.
Dispersion conditions: 10 mg of the sample was added to 5 mL of the dispersion, dispersed for 1 minute using an ultrasonic disperser, then 25 mL of electrolyte was added, and dispersed again for 1 minute using an ultrasonic disperser to prepare the sample dispersion.
Measurement conditions: The sample dispersion was added to 100 mL of the electrolyte in a beaker to adjust the concentration to one that could measure the particle size of 30,000 particles in 20 seconds. Then, the 30,000 particles were measured, and the median volume particle size (D ₅₀ ) was determined from the resulting particle size distribution.

[Manufacturing of addition polymerization resin (A) and addition polymerization resin (A')]

Manufacturing Examples A1-A3 and A5 (Manufacturing of resins A-1, A-2, A'-3, and A'-5)
The raw material monomer (a) for the addition polymerization resin, which contains either acrylic acid or methacrylic acid as the reactive compounds shown in Table 1, was placed in an autoclave equipped with a stainless steel stirring rod, and polymerized under pressurized heating conditions (300°C) for 2 hours. By returning to atmospheric pressure and room temperature, the precipitated addition polymerization resin was recovered to obtain addition polymerization resins A-1, A-2, A'-3, and A'-5. The physical properties of each are shown in Table 1.

Manufacturing Example A4 (Manufacturing of Resin A'-4)
The raw material monomer (a) of the addition polymerization resin containing acrylic acid, as shown in Table 1, and a radical generator were placed in a stainless steel reaction vessel equipped with a thermometer, stainless steel stirring rod, fall-flow condenser, and nitrogen inlet tube, and the raw material monomer (a) was polymerized at 150°C for 2 hours. The addition polymerization resin that precipitated after returning to room temperature was recovered to obtain the addition polymerization resin A'-4. Various physical properties are shown in Table 1.

[Manufacturing of amorphous polyester resins]
Manufacturing example AH1 (Manufacturing of resin AH-1)
The alcohol components, terephthalic acid, dodecenyl succinic anhydride, esterification catalyst, and esterification co-catalyst shown in Table 2 were placed in a 10-liter four-necked flask equipped with a thermometer, stainless steel stirring rod, fractionation column, dehydration tube, condenser, and nitrogen inlet tube. The mixture was heated to 235°C in a mantle heater under a nitrogen atmosphere and reacted at atmospheric pressure for 2.5 hours, followed by a reaction under reduced pressure of 8 kPa for 1 hour. After cooling to 190°C at atmospheric pressure, trimellitic anhydride shown in Table 2 was added, and the mixture was heated to 210°C at a rate of 10°C/h. The reaction was then carried out at 8 kPa until the desired softening point was reached, yielding amorphous polyester resin AH-1. Various physical properties are shown in Table 2.

[Manufacturing of crystalline polyester resin]
Manufacturing Example C1 (Manufacturing of Resin C-1)
The alcohol component, carboxylic acid component, esterification catalyst, and polymerization inhibitor shown in Table 3 were placed in a 10-liter four-necked flask equipped with a thermometer, stainless steel stirring rod, fractionation column, dehydration tube, condenser, and nitrogen inlet tube. The mixture was heated to 140°C in a mantle heater under a nitrogen atmosphere and reacted for 5 hours, after which the temperature was increased to 200°C at a rate of 10°C/h. The reaction was then carried out at 8 kPa until the desired softening point was reached to obtain crystalline polyester resin C-1. Various physical properties were measured and are shown in Table 3. Since resin C-1 was insoluble in the measurement solvent, the acid value and weight-average molecular weight were not measured.

[Manufacturing of composite resins]
Manufacturing Examples 1 and 2 (Manufacturing of Composite Resins AL-1 and AL-2)
The alcohol component (b-al), carboxylic acid component (b-ac), esterification catalyst, and esterification co-catalyst shown in Table 4 were placed in a 10-liter four-necked flask equipped with a thermometer, stainless steel stirring rod, fractionation column, dehydration tube, condenser, and nitrogen inlet tube. The mixture was heated to 235°C in a mantle heater under a nitrogen atmosphere and reacted at atmospheric pressure for 3 hours. After cooling to 180°C, the addition polymerization resin (A) shown in Table 4 was added, and the mixture was heated to 230°C at a rate of 10°C/h. The reaction was then carried out at 67 kPa until the desired softening point was reached to obtain composite resins AL-1 and AL-2. The various physical properties are shown in Table 4.

Manufacturing Examples 3-7 (Manufacturing of Composite Resins AL-3 to AL-7)
The PET, alcohol component (b-al), carboxylic acid component (b-ac), esterification catalyst, and esterification co-catalyst shown in Table 4 were placed in a 10-liter four-necked flask equipped with a thermometer, stainless steel stirring rod, fractionation column, dehydration tube, condenser, and nitrogen inlet tube. The mixture was heated to 235°C in a mantle heater under a nitrogen atmosphere and reacted at atmospheric pressure for 3 hours. After cooling to 180°C, the addition polymerization resin (A) shown in Table 4 was added, and the mixture was heated to 230°C at a rate of 10°C/h. The reaction was then carried out at 67 kPa until the desired softening point was reached, yielding composite resins AL-3 to AL-7. The various physical properties are shown in Table 4.

Comparative manufacturing examples 1, 2, and 4 (manufacturing of composite resins AX-1, AX-2, and AX-4)
The alcohol and carboxylic acid components, esterification catalyst, and esterification co-catalyst shown in Table 5 were placed in a 10-liter four-necked flask equipped with a thermometer, stainless steel stirring rod, fractionation column, dehydration tube, condenser, and nitrogen inlet tube. The mixture was heated to 235°C in a mantle heater under a nitrogen atmosphere and reacted at atmospheric pressure for 2.5 hours, followed by a reaction under reduced pressure of 8 kPa for 1 hour. After cooling to 190°C at atmospheric pressure, the addition polymerization resin (A') shown in Table 5 was added, and the mixture was heated to 235°C. The reaction was then carried out to the desired softening point to obtain composite resins AX-1, AX-2, and AX-4. The various physical properties are shown in Table 5.

Comparative manufacturing examples 3 and 5 (manufacturing of composite resins AX-3 and AX-5)
The alcohol and carboxylic acid components shown in Table 5, the addition polymerization resin (A'), the esterification catalyst, and the esterification co-catalyst were placed in a 10-liter four-necked flask equipped with a thermometer, stainless steel stirring rod, fractionation column, dehydration tube, condenser, and nitrogen inlet tube. The mixture was heated to 190°C in a mantle heater under a nitrogen atmosphere and reacted at atmospheric pressure for 2.0 hours, after which the temperature was increased to 235°C at a rate of 10°C/h. The reaction was then carried out to the desired softening point to obtain composite resins AX-3 and AX-5. The various physical properties are shown in Table 5.

Examples 1-1 to 1-7 and Comparative Examples 1-1 to 1-5
The composite resins obtained in Production Examples 1-7 and Comparative Production Examples 1-5 were evaluated as binder resins using the following method.
[Solution viscosity]
1.5 g of the binder resin shown in Table 6 was dissolved in 8.5 g of chloroform to prepare a solution with a concentration of 15%. Using an E-type viscometer "TVE-25L" (manufactured by Toki Sangyo Co., Ltd.), after stabilizing the temperature of the cone plate at 20°C, 1030 μL of the above solution was collected using a chemical pipette and measured. The results are shown in Table 6.
The higher the solution viscosity, the more efficiently shear force can be applied to the resin during toner manufacturing, improving the mixability with other components such as colorants contained in the toner, and thus increasing toner productivity. Toner productivity is excellent when the solution viscosity is 4.0 mPa·s or higher.

[Crushability Index]
Approximately 1000 mL of the binder resin shown in Table 6 was prepared. Using a sieve shaker (manufactured by Verder Scientific Co., Ltd.), the sample was sieved through 16-mesh and 22-mesh filters, and 20 g of the sample remaining between the 16-mesh and 22-mesh filters was accurately weighed.
Next, the precisely weighed 20g sample was ground in a coffee grinder for 10 seconds, then sieved through a 30-mesh sieve until no more sample fell through, and the sample remaining on the 30-mesh sieve was precisely weighed.
The pulverizability index was calculated using the following formula, and the average of three measurements was used. The results are shown in Table 6.
A higher pulverability index indicates superior resin pulverization capabilities, which can improve toner productivity. A pulverability index of 95.0% or higher indicates excellent toner productivity.
Grinding index (%) = [[20 (g) - Mass of sample remaining on 30 mesh (g)] / 20 (g)] × 100

As shown in Table 6, the examples using specific binder resins exhibit higher solution viscosity, higher pulverability index, and superior toner productivity compared to the comparative examples.

[Toner Manufacturing]
Examples 2-1 to 2-7 and Comparative Examples 2-1 to 2-5
105 parts by mass of binder resin in the proportions shown in Table 7, 1 part by mass of negative charge control agent "Bontron E-81" (manufactured by Orient Chemical Industry Co., Ltd.), 10 parts by mass of coloring agent "Cyanine Blue 4927" (manufactured by Dainichi Seika Kogyo Co., Ltd., C.I. Pigment Blue 15:3), and 1 part by mass of release agent "HNP-9" (manufactured by Nippon Seiro Co., Ltd., paraffin wax, melting point: 80°C) were thoroughly mixed in a Henschel mixer. Then, the mixture was melt-kneaded using a co-rotating twin-screw extruder with a total length of 1560 mm, a screw diameter of 42 mm, and a barrel inner diameter of 43 mm, at a roll rotation speed of 200 r/min and a heating temperature of 100°C inside the rolls. The feed rate of the mixture was 20 kg/h, and the average residence time was approximately 18 seconds. The obtained molten mixture was cooled and coarsely ground, then ground in a jet mill and classified to obtain toner particles with a median volume particle size (D ₅₀ ) of 8 μm.
To 100 parts by mass of the obtained toner particles, 1 part by mass of the external additive "AEROSIL NAX 50" (manufactured by Nippon Aerosil Co., Ltd., hydrophobic silica, hydrophobic treatment agent: HMDS, number average particle size: approximately 30 nm) was added, and the mixture was mixed in a Henschel mixer at 3,600 r/min for 5 minutes to perform the external additive treatment and obtain toners 1-7 and 51-55.

[Toner Evaluation]
[Heat-resistant storage stability]
Four grams of toner were placed in a 20 mL container (approximately 3 cm in diameter) and left for 48 hours at a temperature of 55°C and a relative humidity of 60%. The degree of toner aggregation was then visually observed every 6 hours until 72 hours had passed. A higher time value at which aggregation was observed indicates better heat resistance to high temperature and humidity. The results are shown in Table 7. In Table 7, ">72" indicates that no aggregation was observed even after 72 hours.

[Minimum fixing temperature and hot offset temperature]
Each toner was mounted on a modified fuser unit of the AR-505 copier (manufactured by Sharp Corporation) that allowed for fixing outside the unit, and printed materials were obtained in an unfixed state (print area: 2 cm x 12 cm, adhesion amount: 0.5 mg/ ^cm² ). Subsequently, using a fuser unit adjusted to a total fixing pressure of 40 kgf (fixing speed 300 mm/sec), fixing tests were performed on the unfixed printed materials at each temperature while sequentially increasing the temperature of the fuser roll from 80°C to 240°C in 5°C increments. Cellophane adhesive tape "Uni Cellophane Tape" (manufactured by Mitsubishi Pencil Co., Ltd., width: 18 mm, JIS Z1522) was attached to the image area of the obtained printed materials, passed through a fuser roller set to 30°C, and then the tape was removed. The optical reflectance density before and after tape application was measured using a reflectance densitometer "RD-915" (manufactured by Gretag Macbeth). The minimum fixing temperature was defined as the temperature of the fixing roller at which the ratio of the two (after peeling / before application × 100) first exceeded 90%. A lower minimum fixing temperature indicates superior low-temperature fixing performance.
Furthermore, the lowest temperature at which hot offset was observed on the fixing roll, based on a visual inspection of the fixing images obtained above, was defined as the hot offset temperature. A higher hot offset temperature indicates superior resistance to high-temperature offset.
Furthermore, the difference between the minimum fixing temperature and the hot offset temperature was defined as the fixing temperature range. A wider fixing temperature range expands the usable temperature range, thus meeting the requirements for energy saving and high-speed fixing.
For the fixing paper, we used "CopyBond SF-70NA" (manufactured by Sharp Corporation, 75 g/ ^m² ).
These results are shown in Table 7.

As shown in Table 7, the toners in the examples using binder resins containing specific composite resins exhibit excellent heat resistance and storage properties. Because they have a low minimum fixing temperature and a high hot offset temperature, they have a wide fixing temperature range, demonstrating that they can achieve both excellent heat resistance and a wide usable temperature range.
On the other hand, the comparative toner, compared to the toner in the example, has inferior heat resistance, a higher minimum fixing temperature, or a narrower fixing temperature range, indicating that it fails to achieve both excellent heat resistance and a wide usable temperature range.

Claims (5)

A binder resin for toner containing a composite resin in which an addition polymerization resin unit and a polyester resin unit are bonded together via covalent bonds,
The addition polymerization resin (A) constituting the addition polymerization resin unit contains 80% by mass or more of constituent units derived from (meth)acrylic monomers,
The acid value of the addition polymerization resin (A) is 80 mgKOH/g or more .
A binder resin for toners, in which the (meth)acrylic monomer contains methacrylic acid . The toner binder resin according to claim 1, wherein the weight-average molecular weight of the addition polymerization resin (A) is 5,000 or more. A toner for developing electrostatic images, comprising the toner binder resin described in claim 1 or 2 . A method for producing a binder resin for toner, comprising a composite resin in which an addition polymerization resin unit and a polyester resin unit are bonded together via covalent bonds,
The process includes: Step I: Polymerizing raw material monomer (a) to obtain an addition polymerization resin (A); and Step II: Reacting an alcohol component (b-al) and a carboxylic acid component (b-ac), then adding the addition polymerization resin (A) obtained in Step I and carrying out the reaction to obtain the composite resin.
The raw material monomer (a) contains 80% by mass or more of a (meth)acrylic monomer,
The acid value of the addition polymerization resin (A) is 80 mgKOH/g or more .
A method for producing a binder resin for toner, wherein the (meth)acrylic monomer contains methacrylic acid . The method for producing a binder resin for toner according to claim 4, wherein step II is a step in which polyethylene terephthalate, an alcohol component (b-al), and a carboxylic acid component (b-ac) are reacted, and then the addition polymerization resin (A) obtained in step I is added and the reaction is carried out to obtain the composite resin.