JPH06128368A - Polyester resin for toner binder - Google Patents

Abstract

PURPOSE:To obtain the title resin excellent in grindability and storage stability and well balanced among offset resistance, blocking resistance and low- temperature fixability by using a specified aliphatic glycol and specifying the content of an at least tribasic carboxylic acid. CONSTITUTION:The polyester is prepared by polycondensing a carboxylic acid component comprising a dicarboxylic acid or its lower alkyl ester (A) and an at least tribasic carboxylic acid or its anhydride or lower alkyl ester (B) with a glycol component comprising a primary aliphatic glycol (C) having at least two side chains at least one of which is 2-4 C alkyl and an aromatic glycol (D) represented by the formula wherein R is 3 C or lower alkylene; x and y are each an integer of 1 or greater; and x+y is 2-7 on the average. The constitution ratio is such that 40-99mol%, based on the whole carboxylic acid component, component A, and 1-60mol%, based on the whole carboxylic acid component, component B are present. This polyester has a glass transition temperature of 50-75 deg.C and a gel fraction of below 3%.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyester resin useful as a binder for a dry toner used for developing an electrostatic latent image in electrophotography, electrostatic recording, electrostatic printing and the like. More specifically, the present invention relates to a polyester resin for a toner binder, which has excellent pulverizability, balances blocking resistance, low-temperature fixing property, and offset resistance in a good balance, has low hygroscopicity, and has excellent storage stability.

[0002]

2. Description of the Related Art In order to visualize an electrostatic latent image, an electrostatic latent image is created on a photoconductive photosensitive member or an electrostatic recording medium, and a charge having the opposite sign to the electrostatic latent image is previously formed by friction. After the applied toner is attached by Coulomb force, the toner image is transferred onto a paper or film, and the toner image is fused and fixed. The fusing of the toner image is performed by pressurizing or heating, and fixing by heating includes a non-contact heating method using an infrared lamp, a xenon lamp or an electric oven, and a pressure heating method using a heating roller.

When the toner is classified according to the developing method, there are a two-component developer that uses iron powder or ferrite particles as a carrier and a one-component developer that does not use a carrier.
The toner used for the two-component developer is prepared by melt-kneading a resin for a toner binder, a colorant, a charge control agent and other necessary additives to sufficiently disperse them, and then coarsely pulverizing and finely pulverizing them to obtain a predetermined particle size range. It is manufactured by classifying. The toner used for the one-component developer is manufactured in the same manner by adding magnetic iron powder in addition to the respective components of the above two-component toner.

Since the resin for the toner binder is the main component of the toner, it controls most of the performance required for the toner. Therefore, the toner binder resin has good dispersibility of the colorant and charge control agent in the melt-kneading step in the toner manufacturing step, good pulverizability in the pulverizing step, etc. In this case, it is required to have good fixing property, anti-offset property, anti-blocking property and electrical property, and to maintain stable quality due to environmental changes such as storage.

Epoxy resins, polyester resins, polystyrene resins, acrylic resins and the like are well known as resins for toner binders used in toner.
Styrene / (meth) acrylic acid ester copolymers have been mainly used for the pressure-bonding heat fixing system.

However, it is possible to fix the toner image at a lower temperature, and the toner image on which the toner image is fixed has excellent resistance to vinyl chloride plasticizer.
Recently, polyester resins have been used because of their excellent transparency and their ability to be colored.

The following are known examples of such polyester resins for toner binders. An aromatic glycol having a bisphenol A type skeleton, a divalent carboxylic acid or a lower alkyl ester thereof, and a trivalent or higher polyvalent carboxylic acid or an acid anhydride thereof are copolymerized to give a weak cross-linking structure. It is disclosed in Japanese Laid-Open Patent Publication No. 57-37353. In addition, trivalent or higher carboxylic acid,
JP-A-1-105957 discloses that a divalent carboxylic acid, an aliphatic glycol and an aromatic glycol are copolymerized and a crosslinked structure is defined by a gel fraction of 3 to 40%. Further, a copolymer of a trivalent or higher polyvalent carboxylic acid or a trivalent or higher polyhydric alcohol component, a divalent carboxylic acid component, and a secondary or tertiary diol component is disclosed in JP-A-3-54574. It is disclosed.

[0008]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
The polyester resin obtained by copolymerizing a divalent carboxylic acid or a lower alkyl ester thereof and a trivalent or higher polyvalent carboxylic acid or an acid anhydride thereof with a glycol having a bisphenol A type skeleton disclosed in Japanese Patent No. It supplies a toner that has a low temperature fixability, but does not undergo polycondensation due to a deglycol reaction because it does not use an aliphatic glycol, and it is difficult to efficiently produce a resin having a low acid value to some extent. . In addition, Japanese Patent Laid-Open No. 1-
The polyester resin having a gel fraction of 3 to 40%, which is disclosed in Japanese Patent No. 105957, is obtained by copolymerizing a trivalent or higher carboxylic acid, a divalent carboxylic acid, an aliphatic glycol, and an aromatic glycol. Although the problems of the polyester resin disclosed in JP-A-57-37353 are improved, not only the low-temperature fixability is insufficient, but also fine pulverization is difficult, and therefore, from the viewpoint of production efficiency. Was also desired to be improved. Further, a polyvalent carboxylic acid having a valence of 3 or more or a polyhydric alcohol component having a valence of 3 or more, a divalent carboxylic acid component, and a secondary or tertiary diol component disclosed in JP-A-3-54574 are copolymerized. Although a polyester resin can provide a toner with little odor, its pulverizability and charge stability are not sufficient, and improvement has been desired.

[0009]

The inventors of the present invention have made extensive studies in order to solve the above-mentioned drawbacks. As a result, as the aliphatic glycol, a compound having a limited structure was used, and a compound having a valence of 3 or more was used. By limiting the amount of carboxylic acid, keeping the glass transition temperature in the range of 50 to 75 ° C, and the gel fraction to less than 3%, excellent pulverizability, offset resistance, blocking resistance, and low temperature fixability can be obtained. It was found that a polyester resin for a toner binder having a good balance of properties, low hygroscopicity and excellent storage stability can be obtained, and the present invention has been completed.

That is, the present invention relates to a carboxylic acid component comprising a dicarboxylic acid or a lower alkyl ester (A) thereof and a polycarboxylic acid having a valence of 3 or more, or an acid anhydride thereof or a lower alkyl ester thereof (B), and 2 A primary aliphatic glycol (C) having one or more side chains, at least one of which is an alkyl group having 2 to 4 carbon atoms, and an aromatic glycol (D) represented by the formula (1) In the polyester obtained by polycondensing the glycol component, the dicarboxylic acid component accounts for 40 to 99 mol% and the polyvalent carboxylic acid component accounts for 1 to 60 mol% with respect to the total carboxylic acid component,
Moreover, the glass transition temperature is 50 to 75 ° C, and the gel fraction is 3%.
It is a polyester resin for a toner binder characterized by being less than.

[0011]

[Chemical 2] (R in the formula is an alkylene group having 3 or less carbon atoms, x,
y is an integer of 1 or more, and the average value of x + y is 2 to 7. )

As the dicarboxylic acid or the lower ester (A) thereof used in the present invention, a dicarboxylic acid having a molecular weight of 500 or less or an ester compound with an alcohol having 5 or less carbon atoms can be used. Examples include phthalic acid, terephthalic acid, isophthalic acid, sebacic acid, isodecylsuccinic acid, maleic acid, fumaric acid, itaconic acid,
Examples thereof include glutaconic acid, cyclohexanedicarboxylic acid, and their monomethyl, monoethyl, dimethyl, and diethyl esters, and terephthalic acid, isophthalic acid, and their dimethyl esters are particularly preferable. In addition, in order to improve fixability, aliphatic adipic acid, sebacic acid, azelaic acid, isodecyl succinic acid, maleic acid,
You may use fumaric acid etc. in combination.

The trivalent or higher polyvalent carboxylic acid or its acid anhydride or its lower ester (hereinafter referred to as polyvalent carboxylic acids) (B) used in the present invention has a molecular weight of 300.
Those having the following trivalent or higher functional groups can be used. Examples include 1,2,4-benzenetricarboxylic acid (trimellitic acid), 1,2,5-benzenetricarboxylic acid,
2,5,7-naphthalene tricarboxylic acid, 1,2,4-
Butanetricarboxylic acid, 1,2,5-hexanetricarboxylic acid, 1,3-dicarboxyl-2-methyl-2-methylenecarboxypropane, tetra (methylenecarboxyl) methane, 1,2,7,8-octanetetracarboxylic acid , Trimesic acid, pyromellitic acid, and their anhydrides, lower alkyl ester compounds, and the like,
Especially trimellitic acid, trimesic acid, pyromellitic acid,
Alternatively, their anhydrides, methyl ester compounds and ethyl ester compounds are preferable.

In the carboxylic acid component of the polyester resin of the present invention, the dicarboxylic acid component is 4 with respect to the total carboxylic acid component.
0 to 99 mol%, preferably 50 to 90 mol%, and particularly preferably 60 to 80 mol%, the polycarboxylic acid component is 1
-60 mol%, preferably 10-50 mol%, particularly preferably 20-40 mol%. If the proportion of the polycarboxylic acid is less than 1 mol%, the grindability and the offset resistance are insufficient. On the other hand, when the proportion of polyvalent carboxylic acids exceeds 60 mol%, it becomes extremely difficult to control the polymerization, and when the degree of polymerization is raised to a certain degree, gelation rapidly occurs and the glass transition temperature and gel fraction both increase, resulting in pulverization. Properties and low temperature fixability also deteriorate. If the polymerization is stopped at the stage where gelation does not occur, the glass transition temperature becomes low and the blocking resistance becomes insufficient.

The primary aliphatic glycol (C) having two or more side chains, one or more of which is an alkyl group having 2 to 4 carbon atoms, used in the present invention is a methyl group or an ethyl group. It is a primary aliphatic glycol having a side chain such as a propyl group, a propyl group, an n-butyl group and a t-butyl group, and is 2-methyl-2-ethyl-1,3-propanediol, 2,2.
-Diethyl-1,3-propanediol, 2-methyl-
2-propyl-1,3-propanediol, 2,2-dipropyl-1,3-propanediol, 2-methyl-2
-N-butyl-1,3-propanediol, 2-methyl-2-t-butyl-1,3-propanediol, 2-ethyl-2-n-butyl-1,3-propanediol, 2
-Ethyl-2-t-butyl-1,3-propanediol, 2,2-dibutyl-1,3-propanediol, 2
-Methyl-3-ethyl-1,4-butanediol, 2.
3-diethyl-1,4-butanediol, 2-methyl-
3-propyl-1,4-butanediol, 2-ethyl-
3-propyl-1,4-butanediol, 2-methyl-
3-n-butyl-1,4-butanediol, 2-ethyl-3-n-butyl-1,4-butanediol, 2-ethyl-3-t-butyl-1,4-butanediol, 2,3
-Di-n-butyl-1,4-butanediol, 2,3-
Di-t-butyl-1,4-butanediol, 2-methyl-4-ethyl-1,5-pentanediol, 2,4-diethyl-1,5-pentanediol, 2-ethyl-4-
n-butyl-1,5-pentanediol, 2-ethyl-
4-t-butyl-1,5-pentanediol, 2,4-
Di-n-butyl-1,5-pentanediol, 2,4-
Di-t-butyl-1,5-pentanediol, 2-methyl-5-ethyl-1,6-hexanediol, 2,5-
Diethyl-1,6-hexanediol, 2-ethyl-5
-N-butyl-1,6-hexanediol, 2-ethyl-5-t-butyl-1,6-hexanediol, 2,5
-Di-n-butyl-1,6-hexanediol, 2,5
-Di-t-butyl-1,6-hexanediol and the like can be mentioned. Among these, 2,2-diethyl-1,3-propanediol and 2-ethyl-2butyl-
1,3-Propanediol is preferable in terms of polymerization reactivity and physical properties. By using the aliphatic glycol having such a structure, the ester bond concentration and hygroscopicity of the resin are lowered, and the pulverizability and storage stability required for the toner binder resin are improved.

The aromatic glycol (D) represented by the formula (1) used in the present invention includes polyoxypropylene (2.0) -2,2-bis (4-hydroxyphenyl) propane and polyoxypropylene ( 2.2) -2,
2-bis (4-hydroxyphenyl) propane, polyoxypropylene (2.4) -2,2-bis (4-hydroxyphenyl) propane, polyoxypropylene (3.
3) -2,2-bis (4-hydroxyphenyl) propane, polyoxypropylene (6.0) -2,2-bis (4-hydroxyphenyl) propane, polyoxyethylene (2.0) -2,2 -Bis (4-hydroxyphenyl) propane, polyoxyethylene (2.2) -2,2
-Bis (4-hydroxyphenyl) propane, hydroxypropylene-hydroxyethylene-2,2-bis (4
-Hydroxyphenyl) propane, polyoxypropylene (2.0) -polyoxyethylene (2.0) -2,2
-Bis (4-hydroxyphenyl) propane, polyoxypropylene (4.4) -polyoxyethylene (1.
2) -2,2-bis (4-hydroxyphenyl) propane, polyoxypropylene (3.6) -polyoxyethylene (1.8) -2,2-bis (4-hydroxyphenyl) propane and the like. . These are used alone or in combination. Among these, polyoxypropylene (2.2) -2,2-bis (4-hydroxyphenyl) propane is used alone, or polyoxyethylene (2.2) -2,2-bis (4-hydroxy) is used. Phenyl) propane, polyoxypropylene (6.0)-
2,2-bis (4-hydroxyphenyl) propane, polyoxypropylene (4.4) -polyoxyethylene (1.2) -2,2-bis (4-hydroxyphenyl)
It is preferable to use a combination of propane, polyoxypropylene (3.6) -polyoxyethylene (1.8) -2,2-bis (4-hydroxyphenyl) propane and the like.

The glycol component of the polyester resin of the present invention comprises an aliphatic glycol component and an aromatic glycol component having a specific structure. The proportion of the aliphatic glycol component is 2 to 98 mol% with respect to the total glycol component. Preferably there is. From the viewpoint of polymerization reactivity and physical properties of the resin, it is particularly preferable that the content of the aliphatic glycol component is 10 to 70 mol% with respect to the total glycol component.

In order to enhance the polymerizability of the polyester resin of the present invention, ethylene glycol, 1,2-
A low boiling point glycol such as propylene glycol, 1,4-butanediol, diethylene glycol, dipropylene glycol or neopentyl glycol may be used up to about 10 mol% based on the total glycol component.

It should be noted that, for example, benzoic acid, naphthalenecarboxylic acid, salicylic acid, 4-methylbenzoic acid, 3-methylbenzoic acid, phenoxyacetic acid, biphenylcarboxylic acid, acetic acid, and propione, as long as the characteristics of the polyester resin of the present invention are not impaired. Acid, butyric acid, octanoic acid, decanoic acid, dodecanoic acid, stearic acid, and other monocarboxylic acids, and one or more monocarboxylic acid components such as alkyl esters of these monocarboxylic acids; and n-butanol, isobutanol, sec-butanol, n-hexanol, n-octanol, lauryl alcohol, 2-
One or more monofunctional monomers of monohydric alcohols such as ethylhexanol, decanol, cyclohexanol, benzyl alcohol and dodecyl alcohol can be added.

The polyester resin of the present invention is obtained by polycondensation of the above-mentioned monomers, and has a glass transition temperature of 50 to 50.
It is important that the polyester has a characteristic value of 75 ° C. and a gel fraction of less than 3%.

If the glass transition temperature is less than 50 ° C., the low temperature fixability will be good, but the blocking resistance will be extremely poor, while if it exceeds 75 ° C., the low temperature fixability will be poor. Therefore, Tg needs to be 50 to 75 ° C,
It is particularly preferably 55 to 70 ° C.

When the gel fraction is 3% or more, the offset resistance is improved, but not only the pulverizability is deteriorated, but also the low temperature fixing property is deteriorated.

The acid value of the resin is not particularly limited,
From the viewpoint of the environmental dependence of hygroscopicity and charge stability, it is not preferable that it is too large, and 0.5 to 10 mgKOH /
It is preferably about g.

The polyester resin of the present invention has a low boiling point after the glycol component and the carboxylic acid component as described above are subjected to an ordinary polyester synthesis method, that is, the acid component and the glycol component are esterified or transesterified. It is synthesized by a method of performing polycondensation by removing glycol out of the system under reduced pressure or normal pressure under nitrogen stream. Therefore, the value obtained by dividing the number of moles of the hydroxyl group derived from the glycol component by the number of moles of the carboxyl group derived from the carboxylic acid component is preferably 1.0 or more. At the time of this esterification or transesterification reaction, if necessary, a conventional esterification catalyst or transesterification catalyst such as titanium butoxide, dibutyltin oxide, zinc acetate, manganese acetate, etc. , For example, titanium butoxide, dibutyltin oxide, tin acetate, zinc acetate, antimony trioxide,
Germanium dioxide or the like can be used.

Further, the polymerization temperature and the amount of catalyst are not particularly limited, and may be arbitrarily set as required.

The glass transition temperature (Tg) of the present invention is the temperature at the intersection of the tangent to the base line of the chart and the tangent of the endothermic curve near Tg measured with a differential scanning calorimeter at a heating rate of 10 ° C. .

The acid value is the number of mg of KOH required for neutralization when neutralized and titrated with a KOH solution by a usual titration method.

The gel fraction was obtained by placing 1 g of the sample in 100 ml of tetrahydrofuran and heating and dissolving at 50 ° C. for 3 hours.
It is a value obtained by dividing the weight when it is filtered through a 0.45 μm Teflon filter and sufficiently dried at 60 ° C. in a vacuum dryer by the initial weight.

Next, a test method peculiar to the polyester resin for the toner binder will be described.

(1) Pulverization test The resin that has undergone the usual pulverization process is sifted, and the mesh size is 1
to obtain a resin powder which does not pass through a sieve having an opening of 0.5 mm. Add the above classified resin powder to 10.0
0 g is precisely weighed, crushed with an Aika analysis crusher (manufactured by Shibata Kagaku Kikai Kogyo Co., Ltd.) for 60 seconds, then passed through a sieve having a mesh of 125 μm, and the weight W (g) of the resin that does not pass is precisely weighed. W
The ratio of (g) to the weight before crushing of 10.00 g is represented by the residual ratio (%), and the residual ratio of 0 to 40.0% is ◯, 40.1.
.About.50.0% is indicated by .DELTA., 50.1 to 100% is indicated by X.

(2) Measurement of Fixing Rate A simple fixing test was conducted at a roller temperature of 160 ° C. by using a heat roller type fixing tester capable of freely changing the roller temperature and the roller pressure. After a simple fixing property test was performed, the print density was measured, and after the scotch mending tape was applied, a load of 500 g was applied, and the print density was measured after the tape was peeled off 5 times. The ratio of the print density before and after applying the tape is shown by the fixing rate (%). The print density was measured using a reflection densitometer.

(3) Hot Offset Property Test A simple fixing property test was conducted at a roller temperature of 200 ° C. to confirm whether or not the hot offset phenomenon occurred. The case where the hot offset phenomenon does not occur is shown as ◯, and the case where it occurs is shown as x.

(4) Blocking resistance test A powder sample was filled in a container, left standing in an atmosphere of 50 ° C. for 24 hours, and then the container was turned upside down. However, the state of redispersion when tapped was Δ, and the state of non-redispersion was X. Also,
The same test was performed under high humidity conditions of 40 ° C. and 80% RH, and the same evaluation was performed.

(5) Hygroscopicity test After being left at 40 ° C. and 80% RH for 24 hours, 25 ° C. and 5
The moisture content of a sample left for 2 hours in an environment of 0% RH was measured by a Karl Fischer moisture meter (MKC manufactured by Kyoto Electronics Manufacturing Co., Ltd.).
-3P) to determine the moisture absorption rate of the resin.

[0035]

EXAMPLES Examples of the present invention will be described below, but the present invention is not limited to these examples.

The weight average molecular weight shown in the examples is
It was calculated from the value measured by gel permeation chromatography (GPC). The values were measured under the GPC conditions described below, and the values are used as converted into polystyrene. Tetrahydrofuran was used as a solvent at a temperature of 40 ° C. at a flow rate of 1 ml / min to obtain a sample concentration of 0.5 wt.
/ Mole% tetrahydrofuran sample solution 0.2 m
It was measured by injecting 1 l. As the column, a plurality of commercially available polystyrene gel columns were used in combination. In measuring the molecular weight of the sample, the molecular weight distribution of the sample was calculated from the relationship between the logarithmic value and the count number of a calibration curve prepared from several kinds of monodisperse polystyrene standard samples. An RI (refractive index) detector was used as the detector.

Example 1 The carboxylic acid component was 55 mol% terephthalic acid and 45 mol% trimellitic anhydride, and the glycol component was
To obtain a polyester composed of 10 mol% of 2,2-diethyl-1,3-propanediol and 90 mol% of polyoxypropylene (2.2) -2,2-bis (4-hydroxyphenyl) propane, a monoester was prepared. Adjust the weight of the body,
Charged to a reaction vessel equipped with a stirrer and a rectification tube together with 0.3 wt% of dibutyltin oxide based on the total monomer weight,
Esterification was carried out at 200 to 240 ° C. for 3 hours under a nitrogen stream. Then, it was transferred to a reaction vessel equipped with a depressurizing device, and polycondensation was performed under a reduced pressure of 1.5 Torr at a reaction temperature of 200 ° C. while removing glycol outside the system to obtain a polyester resin for a toner binder. Here, the value obtained by dividing the number of moles of hydroxyl groups derived from the glycol component by the number of moles of carboxyl groups derived from the carboxylic acid component was set to 1.6.

Next, 5 parts by weight of carbon black and 1 part of a charge control agent were added to 94 parts by weight of the obtained polyester resin, melt-kneaded using a twin-screw extruder, cooled, and then coarsely pulverized by a sample mill and jetted. The toner was finely pulverized with a mill and classified with a classifier to obtain a toner having a particle size of 10 to 15 μm. A series of evaluations were performed using a material to which 0.5 wt% of silica was added as an external additive.

Table 2 shows the evaluation results of the polyester resin for toner binder and the toner obtained by the above method.

Examples 2 to 6 and Comparative Examples 1 to 8 The procedure is basically the same as that of Example 1, but the pressure of the polymerization system and the polymerization temperature are appropriately changed as shown in Tables 1 and 3. Then, polyester resins having the compositions shown in Tables 1 and 3 were produced. The evaluation results of the obtained polyester resin for toner binder and toner are shown in Tables 2 and 4.

[0041]

[Table 1]

[0042]

[Table 2]

[0043]

[Table 3]

[0044]

[Table 4]

As is clear from Tables 1 and 2, polyvalent carboxylic acids having a valence of 3 or more are contained in an amount of 1 to 60 mol% based on the total carboxylic acid components, and the glass transition temperature is 50 to 75 ° C. When the ratio is less than 3%, the pulverizability and the fixability are excellent, and the hot-offset and blocking do not occur, and the physical properties are well balanced.

On the other hand, in Comparative Examples 1 and 2 of Tables 3 and 4, the copolymerization amount of the trivalent or higher polyvalent carboxylic acid was as high as 65 mol% in the total carboxylic acid component, and therefore, in Comparative Example 1 When the polymerization time is short, the glass transition temperature is low and the offset resistance and blocking resistance are poor. In addition, Comparative Example 2
As described above, when the degree of polymerization is increased, it rapidly gels, and the pulverizability and low temperature fixability deteriorate. Since Comparative Example 3 does not contain a polycarboxylic acid, the pulverizability and hot offset resistance are insufficient. In Comparative Examples 4 to 6, the resin composition is included in the present invention, but in Comparative Example 4, the glass transition temperature is low and Comparative Example 5
Has a high glass transition temperature and Comparative Example 7 has a high gel fraction, so that the balance of physical properties is insufficient. Furthermore, Comparative Examples 7 and 8 use different aliphatic glycols from those specified in the present invention, and therefore their pulverizability and blocking resistance are insufficient.

[0047]

EFFECTS OF THE INVENTION According to the present invention, it is possible to provide a polyester resin for a toner binder having excellent pulverizability and low hygroscopicity.

By using the resin as a toner binder, it is possible to provide a toner binder having good pulverizability in a pulverizing step and low hygroscopicity and having excellent storage stability and charge stability.

Further, it has low-temperature fixing property and anti-offset property and is excellent in storage stability.

Therefore, the polyester resin of the present invention is useful as a resin for a toner binder.

Claims (1)

[Claims] 1. A carboxylic acid component comprising a dicarboxylic acid or its lower alkyl ester (A) and a trivalent or higher polycarboxylic acid or its acid anhydride or its lower alkyl ester (B), and two or more carboxylic acid components. A glycol component comprising a primary aliphatic glycol (C) having a side chain, at least one of which is an alkyl group having 2 to 4 carbon atoms, and an aromatic glycol (D) represented by the formula (1). In a polyester obtained by polycondensation of 40 to 99 mol% of dicarboxylic acid component and 1 to 60 mol% of polyvalent carboxylic acid component with respect to the total carboxylic acid component, and a glass transition temperature of 50 to A polyester resin for a toner binder, which has a gel fraction of less than 3% at 75 ° C. [Chemical 1] (R in the formula is an alkylene group having 3 or less carbon atoms, x,
y is an integer of 1 or more, and the average value of x + y is 2 to 7. )