Toner binder resin composition

Abstract

The present invention relates to a binder resin composition for toner that can produce highly transparent images, and toner for electrostatic image development containing the binder resin composition. [Solution] A binder resin composition for toner containing an amorphous polyester resin A and an antioxidant, wherein the amorphous polyester resin A is an amorphous composite resin obtained by bonding amorphous polyester resin a and / or amorphous polyester resin a and a styrene resin, the alcohol component of the amorphous polyester resin a contains 20 mol% or more of an alkylene oxide adduct of bisphenol A, the oxidation-reduction potential of the antioxidant is -0.5V or more and 0.5V or less, and the acid value of the binder resin composition for toner is 5 mg KOH / g or more, and a toner for electrostatic image development containing the binder resin composition.

Description

Technical Field

[0001] The present invention relates to a binder resin composition for toner used for developing a latent image formed in, for example, an electrophotographic method, an electrostatic recording method, an electrostatic printing method, etc., and an electrostatic charge image developing toner containing the binder resin composition.

Background Art

[0002] Polyester resins are used as binder resins for electrophotographic toners by utilizing their chemical and physical properties.

[0003] Patent Document 1 discloses an invention relating to a toner binder for use in a toner having excellent durability and chargeability and a wide fixing width, which contains a polyester resin in which an alcohol component contains ethylene glycol and a carboxylic acid component contains terephthalic acid and isophthalic acid, and the polyester resin contains a predetermined amount of calcium.

[0004] Patent Document 2 discloses an invention relating to a method for producing a polyester resin, which is a method for producing a polyester resin by polycondensing an alcohol component (x) containing an alkylene oxide adduct (x1) of bisphenol A and a carboxylic acid component (y) containing an aromatic dicarboxylic acid (y1), and has a first polycondensation step of polycondensing until the acid value of the reactant becomes 2 mgKOH / g or less in the presence of a titanium compound and an amine compound having an acid dissociation constant (pKa) of 7 to 10, and a second polycondensation step of adding isophthalic acid to the reactant obtained in the first polycondensation step and further polycondensing.

[0005] Patent Document 3 discloses an invention relating to a polyester resin that has good heat resistance and stability, which is synthesized by containing at least a phenolic antioxidant, a trivalent or higher polycarboxylic acid or its anhydride, and / or a trivalent or higher polyhydric alcohol, and in which the ratio of ultra-high molecular weight to high molecular weight is controlled. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2023-10575 [Patent Document 2] Japanese Patent Publication No. 2022-111067 [Patent Document 3] Japanese Patent Application Publication No. 11-246747 [Overview of the project] [Problems that the invention aims to solve]

[0007] In recent years, printing on media other than paper, such as film and labels, has increased. Therefore, there is a need for toners that can produce highly transparent images that can widely represent images with high light transmittance on these media.

[0008] The present invention relates to a binder resin composition for toner that can produce highly transparent images, and toner for electrostatic image development containing the binder resin composition. [Means for solving the problem]

[0009] The present invention [1] A binder resin composition for toner containing amorphous polyester resin A and an antioxidant, wherein the amorphous polyester resin A is amorphous polyester resin a and / or amorphous composite resin obtained by bonding amorphous polyester resin a and a styrene resin, the alcohol component of the amorphous polyester resin a contains 20 mol% or more of an alkylene oxide adduct of bisphenol A, the oxidation-reduction potential of the antioxidant is -0.5V or more and 0.5V or less, and the acid value of the binder resin composition for toner is 5 mg KOH / g or more, and [2] A toner for developing electrostatic images containing the toner binder resin composition described in [1] above. Regarding. [Effects of the Invention]

[0010] The toner binder resin composition of the present invention exhibits the excellent effect of producing highly transparent images. [Modes for carrying out the invention]

[0011] The toner binder resin composition of the present invention (hereinafter also referred to as the "resin composition") has a specific acid value, contains a predetermined amount of an alkylene oxide adduct of bisphenol A as an alcohol component, and contains an antioxidant having a specific oxidation-reduction potential. The details of why the transparency of the image is improved are not clear, but it is presumed to be as follows.

[0012] When polyester resins are subjected to excessive heat during manufacturing, oxidative decomposition reactions occur, generating highly crystalline by-products derived from low-boiling point diols. These by-products cause clouding of printed materials, reducing image transparency. However, in this invention, an antioxidant with a low oxidation-reduction potential is strongly oxidized itself, thereby strongly suppressing the oxidative decomposition reaction during resin production and dramatically reducing the amount of by-products. Furthermore, by using a specific amount or more of an alkylene oxide adduct of bisphenol A as the alcohol component of the amorphous polyester resin, it is possible not only to create a state in which by-products are less likely to form, but also to disrupt the crystallinity of the by-products. Also, by setting the acid value of the binder resin composition for toner to a predetermined value or more, the resin composition becomes hydrophilic, and the compatibility with hydrophilic by-products is improved. Therefore, it becomes possible to suppress the crystallization of the by-products, and it is considered that the transparency of the image is improved.

[0013] Whether the resin is crystalline or amorphous is determined by the crystallinity index. The crystallinity index is defined as the ratio of the softening point of the resin to the maximum peak temperature of endotherm in the measurement method described in the examples below (softening point (°C) / maximum peak temperature of endotherm (°C)). A crystalline resin is one with a crystallinity index of 0.6 or more and 1.4 or less. An amorphous resin is one where no endothermic peak is observed, or if an endothermic peak is observed, the crystallinity index is less than 0.6 or more than 1.4. The crystallinity of the resin can be adjusted by the type and ratio of the raw material monomers, and manufacturing conditions (e.g., reaction temperature, reaction time, cooling rate), etc. The maximum peak temperature of endotherm refers to the temperature of the peak with the largest peak area among the observed endothermic peaks. In the case of a crystalline resin, the maximum peak temperature of endotherm is taken as the melting point.

[0014] The amorphous polyester resin A is an amorphous polyester resin a and / or an amorphous composite resin in which an amorphous polyester resin a and a styrene resin are bonded.

[0015] The alcohol component of the amorphous polyester resin a contains 20 mol% or more of an alkylene oxide adduct of bisphenol A. Therefore, the amorphous polyester resin a is preferably a polycondensate of an alcohol component containing 20 mol% or more of an alkylene oxide adduct of bisphenol A and a carboxylic acid component.

[0016] Examples of the alkylene oxide adduct of bisphenol A include formula (I):

[0017]

Chemical formula

[0018] (In the formula, OR and RO are oxyalkylene groups, R is an ethylene group and / or a propylene group, x and y represent the average number of moles of alkylene oxide added, and are positive numbers respectively. The value of the sum of x and y is 1 or more, preferably 1.5 or more, and 16 or less, preferably 8 or less, more preferably 6 or less, and even more preferably 4 or less.) The compound represented by is preferred.

[0019] From the viewpoint of low-temperature fixing property, the content of the alkylene oxide adduct of bisphenol A is 20 mol% or more, preferably 30 mol% or more, more preferably 40 mol% or more, still more preferably 50 mol% or more, and 100 mol% or less in the alcohol component.

[0020] Examples of other alcohol components include aliphatic diols, diols such as bisphenol A and hydrogenated bisphenol A, and polyhydric alcohols having three or more valences such as sorbitol, pentaerythritol, glycerin, and trimethylolpropane. Among these, aliphatic diols are preferred from the viewpoint of the reactivity of the esterification reaction.

[0021] Examples of aliphatic diols include ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, 1,2-butanediol, 1,3-butanediol, 2,3-butanediol, 1,5-pentanediol, 1,2-pentanediol, 1,3-pentanediol, 2,3-pentanediol, 2,4-pentanediol, 1,6-hexanediol, 1,4-butenediol, 1,3-butanediol, 1,5-pentanediol, 1,7-heptanediol, 1,8-octanediol, neopentyl glycol, 1,9-nonanediol, 1,10-decanediol, 1,11-undecanediol, 1,12-dodecanediol, and the like.

[0022] The aliphatic diol has 2 or more carbon atoms, and preferably 5 or less, more preferably 4 or less, and even more preferably 3 or less.

[0023] The aliphatic diol content is 0 mol% or more and 80 mol% or less of the alcohol component, preferably 70 mol% or less, more preferably 60 mol% or less, and even more preferably 50 mol% or less.

[0024] From the viewpoint of low-temperature fixability, the carboxylic acid component preferably contains an aromatic dicarboxylic acid compound.

[0025] Examples of aromatic dicarboxylic acid compounds include phthalic acid, isophthalic acid, terephthalic acid, anhydrides of these acids, and alkyl esters of these acids with 1 to 3 carbon atoms.

[0026] The content of aromatic dicarboxylic acid compounds is preferably 10 mol% or more, more preferably 20 mol% or more, even more preferably 40 mol% or more, and 100 mol% or less, in the carboxylic acid component.

[0027] Furthermore, the carboxylic acid component may contain trivalent or higher carboxylic acid compounds from the viewpoint of productivity and storage under high humidity.

[0028] Examples of carboxylic acid compounds with a valency of 3 or higher include trimellitic acid, pyromellitic acid, anhydrides of these acids, and alkyl esters of these acids with 1 to 3 carbon atoms.

[0029] The content of trivalent or higher carboxylic acid compounds is 0 mol% or more of the carboxylic acid component, preferably 30 mol% or less, and more preferably 25 mol% or less.

[0030] Other carboxylic acid components include fumaric acid, maleic acid, succinic acid, succinic acid derivatives substituted with hydrocarbon groups, aliphatic dicarboxylic acids such as glutaric acid, adipic acid, and sebacic acid, anhydrides of these acids, and alkyl esters of these acids with 1 to 3 carbon atoms.

[0031] The alcohol component may contain a monohydric alcohol, and the carboxylic acid component may contain a monohydric carboxylic acid compound, as appropriate.

[0032] In this specification, macromonomers and hydroxycarboxylic acids are not included in the alcohol and carboxylic acid components.

[0033] The equivalent ratio (COOH group / OH group) of the carboxyl group of the carboxylic acid component to the hydroxyl group of the alcohol component is preferably 0.6 or higher, more preferably 0.7 or higher, even more preferably 0.8 or higher, and preferably 1.3 or lower, more preferably 1.2 or lower, from the viewpoint of adjusting the softening point of the polyester resin.

[0034] Amorphous polyester resin a can be produced, for example, by polycondensing an alcohol component and a carboxylic acid component in an inert gas atmosphere, preferably in the presence of an esterification catalyst, and optionally in the presence of a co-catalyst, polymerization inhibitor, etc., at a temperature preferably 160°C or higher, more preferably 200°C or higher, and preferably 250°C or lower, more preferably 240°C or lower.

[0035] Examples of esterification catalysts include tin compounds such as dibutyltin oxide and tin(II) 2-ethylhexanoate, and titanium compounds such as titanium diisopropoxybis(triethanolamine) and titanium dihydroxybis(triethanolamine). The amount of esterification catalyst used is preferably 0.01 parts by mass or more, more preferably 0.1 parts by mass or more, and preferably 1.5 parts by mass or less, and more preferably 1 part by mass or less, per 100 parts by mass of the total amount of alcohol and carboxylic acid components. Examples of co-catalysts for the esterification catalyst include gallic acid. The amount of co-catalyst used is preferably 0.001 parts by mass or more, more preferably 0.01 parts by mass or more, and preferably 0.5 parts by mass or less, and more preferably 0.1 parts by mass or less, per 100 parts by mass of the total amount of alcohol and carboxylic acid components. Examples of polymerization inhibitors include tert-butylcatechol. The amount of polymerization inhibitor used is preferably 0.001 parts by mass or more, more preferably 0.01 parts by mass or more, and preferably 0.5 parts by mass or less, and more preferably 0.1 parts by mass or less, based on 100 parts by mass of the total amount of alcohol and carboxylic acid components.

[0036] In this invention, the polyester resin may be a polyester resin that has been modified to such an extent that its properties are not substantially impaired. Examples of modified polyester resins include polyester resins that have been grafted or blocked with phenol, urethane, epoxy, etc., by methods described in Japanese Patent Publication No. 11-133668, Japanese Patent Publication No. 10-239903, Japanese Patent Publication No. 8-20636, etc.

[0037] In the amorphous composite resin, the styrene-based resin is an addition polymer of raw material monomers containing at least styrene, or a styrene derivative such as α-methylstyrene or vinyltoluene (hereinafter, styrene and styrene derivatives are collectively referred to as "styrene compounds").

[0038] The styrene compound, preferably styrene, content in the raw material monomer of the styrene resin is preferably 50% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, and 100% by mass or less, from the viewpoint of preservation, and preferably 95% by mass or less, more preferably 90% by mass or less, from the viewpoint of low-temperature fixability.

[0039] Furthermore, the styrene-based resin may contain an alkyl (meth)acrylate ester with an alkyl group having 7 or more carbon atoms as a raw material monomer. Examples of alkyl (meth)acrylate esters include 2-ethylhexyl (meth)acrylate, (iso)octyl (meth)acrylate, (iso)decyl (meth)acrylate, and (iso)stearyl (meth)acrylate. It is preferable to use one or more of these. In this specification, "(iso)" means that this group may or may not be present, and when these groups are not present, it indicates that it is normal. Also, "(meth)acrylic acid" refers to acrylic acid, methacrylic acid, or both.

[0040] In alkyl (meth)acrylate esters used as raw material monomers for styrene-based resins, the number of carbon atoms in the alkyl group is preferably 7 or more, more preferably 8 or more, and preferably 12 or less, and more preferably 10 or less, from the viewpoint of improving the low-temperature fixability of the toner. Note that the number of carbon atoms in the alkyl ester refers to the number of carbon atoms derived from the alcohol component constituting the ester.

[0041] The raw material monomers for styrene-based resins may also include raw material monomers other than styrene compounds and alkyl (meth)acrylates, such as ethylenically unsaturated monoolefins such as ethylene and propylene; diolefins such as butadiene; halovinyls such as vinyl chloride; vinyl esters such as vinyl acetate and vinyl propionate; ethylenically monocarboxylic acid esters such as dimethylaminoethyl (meth)acrylate; vinyl ethers such as methyl vinyl ether; vinylidene halides such as vinylidene chloride; and N-vinyl compounds such as N-vinylpyrrolidone.

[0042] The addition polymerization reaction of the raw material monomers for styrene-based resins can be carried out by conventional methods in the presence of polymerization initiators such as dibutyl peroxide and dicumyl peroxide, chain transfer agents, crosslinking agents, etc., in the presence of an organic solvent or without a solvent. The temperature conditions are preferably 110°C or higher, more preferably 140°C or higher, and preferably 200°C or lower, more preferably 170°C or lower.

[0043] When using an organic solvent during the addition polymerization reaction, xylene, toluene, methyl ethyl ketone, acetone, etc., can be used. The amount of organic solvent used is preferably 10 to 50 parts by mass per 100 parts by mass of the raw material monomer of the styrene resin.

[0044] The amorphous composite resin is preferably a resin in which amorphous polyester resin a and a styrene-based resin are bonded together, and more preferably a resin in which amorphous polyester resin a and a styrene-based resin are chemically bonded together via reactive monomers that can react with either the raw material monomer of amorphous polyester resin a (hereinafter also referred to as the raw material monomer of the polyester resin) or the raw material monomer of the styrene-based resin.

[0045] The reactive monomers are preferably compounds having at least one functional group selected from the group consisting of hydroxyl groups, carboxyl groups, epoxy groups, primary amino groups, and secondary amino groups, preferably a hydroxyl group and / or a carboxyl group, more preferably a carboxyl group, and an ethylenically unsaturated bond within the molecule. More preferably, at least one selected from the group consisting of acrylic acid, methacrylic acid, fumaric acid, maleic acid, and maleic anhydride is preferred, and even more preferably, at least one selected from the group consisting of acrylic acid, methacrylic acid, and fumaric acid is preferred from the viewpoint of reactivity in polycondensation and addition polymerization reactions. However, when used together with a polymerization inhibitor, polycarboxylic acid compounds having an ethylenically unsaturated bond, such as fumaric acid, function as raw material monomers for polyester resins. In this case, fumaric acid, etc., are not the reactive monomers, but raw material monomers for polyester resins.

[0046] The amount of both reactive monomers used is preferably 1 mole or more, more preferably 2 moles or more, per 100 moles of the alcohol component of the polyester resin, from the viewpoint of improving the dispersibility of the styrene resin and amorphous polyester resin a, and improving the dispersibility of the raw materials in the toner. Furthermore, from the viewpoint of improving the low-temperature fixability of the toner, the amount of both reactive monomers used is preferably 30 moles or less, more preferably 20 moles or less, and even more preferably 15 moles or less.

[0047] Amorphous composite resins are preferably manufactured by the following method. When both reactive monomers are used, it is preferable to use both reactive monomers together with styrene-based resin raw material monomers from the viewpoint of improving the dispersibility of the raw materials in the toner and the low-temperature fixability.

[0048] (i) A method comprising a polycondensation reaction step (A) of polyester resin using raw material monomers, followed by an addition polymerization reaction step (B) of styrene resin using raw material monomers. In this method, step (A) is carried out under reaction temperature conditions suitable for polycondensation, the reaction temperature is lowered, and step (B) is carried out under temperature conditions suitable for addition polymerization. It is preferable to add the styrene resin raw material monomer to the reaction system at a temperature suitable for addition polymerization. When both reactive monomers are used together with the styrene resin raw material monomer, both reactive monomers undergo addition polymerization and also react with the polyester resin. After step (B), the reaction temperature can be raised again, and if necessary, trivalent or higher polyester resin raw material monomers that act as crosslinking agents can be added to the polymerization system to further advance the polycondensation reaction in step (A) and the reaction with both reactive monomers.

[0049] (ii) A method in which a polycondensation reaction (A) is carried out using polyester resin raw material monomers after an addition polymerization reaction (B) using styrene resin raw material monomers. In this method, step (B) is carried out under reaction temperature conditions suitable for the addition polymerization reaction, and then the reaction temperature is increased to carry out the polycondensation reaction in step (A) under temperature conditions suitable for the polycondensation reaction. When both reactive monomers are used together with the raw material monomers of the styrene resin, both reactive monomers participate in both the addition polymerization reaction and the polycondensation reaction. The raw material monomers for the polyester resin may be present in the reaction system during the addition polymerization reaction, or they may be added to the reaction system under temperature conditions suitable for the polycondensation reaction. In the former case, the progress of the polycondensation reaction can be controlled by adding an esterification catalyst at a temperature suitable for the polycondensation reaction.

[0050] (iii) A method in which the polycondensation reaction of polyester resin using raw material monomers (A) and the addition polymerization reaction of styrene resin using raw material monomers (B) proceed in parallel under conditions. In this method, steps (A) and (B) are carried out in parallel under reaction temperature conditions suitable for addition polymerization, the reaction temperature is increased, and under temperature conditions suitable for polycondensation, a raw material monomer of a trivalent or higher polyester resin that acts as a crosslinking agent is added to the polymerization system as needed, and the polycondensation reaction of step (A) is carried out further. At that time, under temperature conditions suitable for polycondensation, a polymerization inhibitor can be added to allow only the polycondensation reaction to proceed. When both reactive monomers are used, both reactive monomers participate in both the addition polymerization reaction and the polycondensation reaction.

[0051] In method (i) above, a pre-polymerized polyester resin may be used instead of step (A) in which the polycondensation reaction is carried out. In method (iii) above, when the reaction is carried out under conditions in which steps (A) and (B) proceed in parallel, a mixture containing the raw material monomer of a styrene-based resin can be added dropwise to a mixture containing the raw material monomer of a polyester resin and the reaction can be carried out.

[0052] Methods (i) to (iii) described above are preferably carried out in the same container.

[0053] The amorphous composite resin preferably contains 55% by mass or more of a structure derived from amorphous polyester resin a. Therefore, the mass ratio of amorphous polyester resin a to styrene-based resin in the composite resin (amorphous polyester resin a / styrene-based resin) is preferably 55 / 45 or more, more preferably 60 / 40 or more, from the viewpoint of low-temperature fixability, and preferably 98 / 2 or less, more preferably 95 / 5 or less, and even more preferably 90 / 10 or less, from the viewpoint of improving the dispersibility of the raw materials in the toner. In the above calculation, the mass of amorphous polyester resin a is the amount obtained by subtracting the amount of reaction water (calculated value) dehydrated by the polycondensation reaction from the mass of the raw material monomers of amorphous polyester resin a used, and the amounts of both reactive monomers are included in the amount of raw material monomers of amorphous polyester resin a. The amount of styrene-based resin is the total amount of raw material monomers of styrene-based resin and polymerization initiator.

[0054] The content of amorphous polyester resin A in the toner binder resin composition is preferably 90% by mass or more, more preferably 95% by mass or more, even more preferably 98% by mass or more, even more preferably 99% by mass or more, even more preferably 99.5% by mass or more, and preferably 99.995% by mass or less, more preferably 99.99% by mass or less, even more preferably 99.8% by mass or less, and even more preferably 99.7% by mass or less.

[0055] The antioxidant is not particularly limited as long as its oxidation-reduction potential is within a predetermined range, but examples include phosphorus-based antioxidants, sulfur-based antioxidants, triazine-based antioxidants, benzotriazole-based antioxidants, phenol-based antioxidants, and amine-based antioxidants. Among these, phosphorus-based antioxidants having a phosphate group are preferred from the viewpoint of transparency.

[0056] Phosphorus-based antioxidants are not limited to the following, but include, for example, tris(2,4-di-tert-butylphenyl) phosphite, bis(2,4-bis(1,1-dimethylethyl)-6-methylphenyl) ethyl ester phosphorous acid, tetrakis(2,4-di-tert-butylphenyl)(1,1-biphenyl)-4,4'-diylbisphosphonate, bis(2,4-di-tert-butylphenyl) pentaerythritol diphosphite, bis(2,6-di-tert-butyl-4-methylphenyl) pentaerythritol diphosphite, bis(2,4-dicumylphenyl) pentaerythritol diphosphite, tetraki Examples include (2,4-tert-butylphenyl)(1,1-biphenyl)-4,4'-diylbisphosphonate, di-tert-butyl-m-cresyl-phosphonate, 4-[3-[(2,4,8,10-tetra-tert-butyldibenzo[d,f][1,3,2]dioxaphosphepin)-6-yloxy]propyl]-2-methyl-6-tert-butylphenol, tris[2-[[2,4,8,10-tetra-tert-butyldibenzo[d,f][1,3,2]dioxaphosphefin-6-yl]oxy]ethyl]amine, and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide. Among these, it is preferable that the phosphorus-based antioxidant has a phenyl group in addition to a phosphate group, and more preferably has two or more di-tert-butylphenyl structures, preferably two or three. For example, phosphorus-based antioxidants having a phosphate group and a phenyl group include 4-[3-[(2,4,8,10-tetra-tert-butyldibenzo[d,f][1,3,2]dioxaphosfepin)-6-yloxy]propyl]-2-methyl-6-tert-butylphenol and tris(2,4-di-tert-butylphenyl) phosphite, and is preferably 4-[3-[(2,4,8,10-tetra-tert-butyldibenzo[d,f][1,3,2]dioxaphosfepin)-6-yloxy]propyl]-2-methyl-6-tert-butylphenol.

[0057] Commercial phosphorus antioxidants may be used as phosphorus-based antioxidants, and such commercial phosphorus-based antioxidants are not limited to the following, but include, for example, Irgafos 168 (tris(2,4-di-tert-butylphenyl) phosphite, manufactured by BASF), Irgafos 12 (tris[2-[[2,4,8,10-tetra-tert-butyldibenzo[d,f][1,3,2]dioxaphosphephine-6-yl]oxy]ethyl]amine, manufactured by BASF), Irgafos 38 (bis(2,4-bis(1,1-dimethylethyl)-6-methylphenyl) ethyl ester phosphorous acid, manufactured by BASF), and Sumilizer GP. Examples include GP:4-[3-[(2,4,8,10-tetra-tert-butyldibenzo[d,f][1,3,2]dioxaphosfepine)-6-yloxy]propyl]-2-methyl-6-tert-butylphenol (manufactured by Sumitomo Chemical Co., Ltd.) and HCA (9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (manufactured by Sanko Co., Ltd.)).

[0058] From the viewpoint of developability, the oxidation-reduction potential of the antioxidant is -0.5V or higher, preferably -0.1V or higher, more preferably -0.05V or higher, and from the viewpoint of transparency, it is 0.5V or lower, preferably 0.1V or lower, more preferably 0V or lower.

[0059] The antioxidant content in the toner binder resin composition is preferably 0.005% by mass or more, more preferably 0.1% by mass or more, even more preferably 0.2% by mass or more, and even more preferably 0.3% by mass or more, and from the viewpoint of transparency, it is preferably 2% by mass or less, more preferably 1% by mass or less, and even more preferably 0.5% by mass or less.

[0060] The toner binder resin composition of the present invention may be obtained by mixing amorphous polyester resin A and an antioxidant, or it may be obtained by adding an antioxidant at the start or during the polycondensation of the alcohol component and carboxylic acid component when synthesizing amorphous polyester resin A.

[0061] The toner binder resin composition of the present invention may contain components other than amorphous polyester resin A and antioxidants, as long as the effects of the present invention are not impaired.

[0062] The softening point of the toner binder resin composition is preferably 70°C or higher, more preferably 90°C or higher, from the viewpoint of electrostatic stability, and preferably 150°C or lower, more preferably 135°C or lower, and even more preferably 125°C or lower, from the viewpoint of low-temperature fixation.

[0063] The glass transition temperature of the toner binder resin composition is preferably 40°C or higher, more preferably 50°C or higher, from the viewpoint of storage properties, and preferably 80°C or lower, more preferably 75°C or lower, from the viewpoint of low-temperature fixing properties.

[0064] The acid value of the toner binder resin composition is preferably 5 mg KOH / g or more, more preferably 8 mg KOH / g or more, from the viewpoint of developability, and preferably 40 mg KOH / g or less, more preferably 20 mg KOH / g or less, from the viewpoint of storage under high humidity.

[0065] Furthermore, the present invention provides a toner for electrostatic image development that contains the toner binder resin composition of the present invention as part or all of the binder resin.

[0066] The content of the toner binder resin composition is preferably 50% by mass or more, more preferably 60% by mass or more, even more preferably 70% by mass or more, and preferably 100% by mass or less, more preferably 95% by mass or less, and even more preferably 90% by mass or less, in the binder resin.

[0067] The toner of the present invention may contain a resin other than the toner binder resin composition of the present invention as a binder resin, as long as it does not impair the effects of the present invention.

[0068] Other binder resins include crystalline polyester resins, vinyl resins such as styrene-acrylic resins, polyamide resins, epoxy resins, polycarbonate resins, polyurethane resins, and composite resins containing two or more of these resins. In the present invention, from the viewpoint of high-temperature separation properties, amorphous polyester resin B, which has a higher softening point than amorphous polyester resin A, is preferred.

[0069] Amorphous polyester resin B is obtained in the same manner as amorphous polyester resin A.

[0070] The difference in softening points between amorphous polyester resin A and amorphous polyester resin B is preferably 5°C or higher, more preferably 15°C or higher, even more preferably 25°C or higher, and preferably 70°C or lower, more preferably 50°C or lower, and even more preferably 45°C or lower.

[0071] The softening point of amorphous polyester resin B is preferably 120°C or higher, more preferably 130°C or higher, even more preferably 140°C or higher, and preferably 170°C or lower, more preferably 160°C or lower, and even more preferably 150°C or lower.

[0072] The glass transition temperature of amorphous polyester resin B is preferably 50°C or higher, more preferably 55°C or higher, even more preferably 60°C or higher, and preferably 85°C or lower, more preferably 80°C or lower, and even more preferably 75°C or lower.

[0073] The acid value of amorphous polyester resin B is preferably 5 mg KOH / g or more, more preferably 10 mg KOH / g or more, even more preferably 15 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.

[0074] The content of amorphous polyester resin B in the binder resin is preferably 0% by mass or more, more preferably 5% by mass or more, even more preferably 10% by mass or more, and preferably 50% by mass or less, more preferably 40% by mass or less, and even more preferably 30% by mass or less.

[0075] The binder resin content in the toner is preferably 50% by mass or more, more preferably 60% by mass or more, even more preferably 70% by mass or more, even more preferably 80% by mass or more, and preferably less than 100% by mass, more preferably 99% by mass or less, even more preferably 98% by mass or less, and even more preferably 95% by mass or less.

[0076] The electrostatic image developing toner of the present invention may contain additives other than the binder resin, such as colorants, release agents, charge control agents, magnetic powders, flowability enhancers, conductivity modifiers, reinforcing fillers such as fibrous materials, antioxidants, and cleaning properties enhancers.

[0077] As colorants, dyes, pigments, magnetic materials, etc., used as colorants for toners can be used. Examples include carbon black, phthalocyanine blue, permanent brown FG, brilliant first scarlet, pigment green B, rhodamine-B base, solvent red 49, solvent red 146, solvent blue 35, quinacridone, carmine 6B, isoindoline, disazo yellow, etc. In this invention, the toner may be either black toner or color toner.

[0078] From the viewpoint of improving the image density of the toner and its low-temperature fixability, the amount of colorant is preferably 1 part by mass or more, more preferably 2 parts by mass or more, and preferably 40 parts by mass or less, more preferably 20 parts by mass or less, and even more preferably 10 parts by mass or less, per 100 parts by mass of the binder resin.

[0079] Examples of mold release agents include hydrocarbon waxes and their oxides, such as polypropylene wax, polyethylene wax, ethylene propylene copolymer wax, microcrystalline wax, paraffin wax, and Fischer-Tropsch wax; ester waxes such as carnauba wax, montane wax and their deoxidizing waxes, and fatty acid ester waxes; and fatty acid amides, fatty acids, higher alcohols, fatty acid metal salts, etc., which can be used individually or in combination of two or more.

[0080] The melting point of the release agent is preferably 60°C or higher, more preferably 70°C or higher, from the viewpoint of toner transferability, and preferably 160°C or lower, more preferably 140°C or lower, even more preferably 120°C or lower, and even more preferably 110°C or lower, from the viewpoint of low-temperature fixation.

[0081] The release agent content is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, even more preferably 1.5 parts by mass or more, and preferably 10 parts by mass or less, more preferably 8 parts by mass or less, and even more preferably 7 parts by mass or less, per 100 parts by mass of binder resin, from the viewpoint of low-temperature fixation and offset resistance of the toner and dispersibility in the binder resin.

[0082] The charge control agent is not particularly limited and may contain either a positively charged charge control agent or a negatively charged charge control agent.

[0083] Positively charged charge control agents include nigrosine dyes, such as "Nigrosine Base EX," "Oil Black BS," "Oil Black SO," "Bontron N-01," "Bontron N-04," "Bontron N-07," "Bontron N-09," "Bontron N-11," and "Bontron N-79" (all manufactured by Orient Chemical Industries, Ltd.); triphenylmethane-based dyes containing tertiary amines as side chains; quaternary ammonium salt compounds, such as "Bontron P-51" (manufactured by Orient Chemical Industries, Ltd.), cetyltrimethylammonium bromide, and "COPY CHARGE PX." Examples include VP435 (manufactured by Clariant), polyamine resins such as AFP-B (manufactured by Orient Chemical Industries, Ltd.), imidazole derivatives such as PLZ-2001 and PLZ-8001 (both manufactured by Shikoku Chemicals, Ltd.), and styrene-acrylic resins such as FCA-701PT and FCA-201-PS (manufactured by Fujikura Chemicals, Ltd.).

[0084] Furthermore, as negative charge control agents, metal-containing azo dyes, such as "Barifast Black 3804," "Bontron S-31," "Bontron S-32," "Bontron S-34," and "Bontron S-36" (all manufactured by Orient Chemical Industries, Ltd.), "Eisenspiron Black TRH," and "T-77" (manufactured by Hodogaya Chemical Co., Ltd.); metal compounds of benzyl acid compounds, such as "LR-147" and "LR-297" (both manufactured by Nippon Carlit Co., Ltd.); metal compounds of salicylic acid compounds, such as "Bontron E-81," "Bontron E-84," "Bontron E-88," and "Bontron E-304" (all manufactured by Orient Chemical Industries, Ltd.), and "TN-105" (manufactured by Hodogaya Chemical Co., Ltd.); copper phthalocyanine dyes; and quaternary ammonium salts, such as "COPY CHARGE NX" Examples include VP434 (manufactured by Clariant), nitroimidazole derivatives, organometallic compounds, etc.

[0085] From the viewpoint of the charge stability of the toner, the content of the charge control agent is preferably 0.01 parts by mass or more, more preferably 0.2 parts by mass or more, and preferably 10 parts by mass or less, more preferably 5 parts by mass or less, even more preferably 3 parts by mass or less, and even more preferably 2 parts by mass or less, per 100 parts by mass of the binder resin.

[0086] The toner of the present invention may be obtained by any known method such as melt-kneading, emulsification-coagulation, or polymerization, but from the viewpoint of productivity and dispersibility of colorants, pulverized toner obtained by melt-kneading is preferred. In the case of pulverized toner obtained by melt-kneading, for example, raw materials such as binder resin, colorant, release agent, and charge control agent can be uniformly mixed in a mixer such as a Henschel mixer, then melt-kneaded, cooled, pulverized, and classified to produce the toner.

[0087] The mixture to be subjected to melt kneading may be kneaded all at once or in portions, but it is preferable to mix it beforehand in a mixer such as a Henschel mixer or ball mill before supplying it to the kneader. The amorphous polyester resin A and the antioxidant may be used as a toner binder resin composition obtained by mixing them beforehand, or they may be used individually or mixed with other raw materials.

[0088] For melt mixing, known mixing machines such as closed-type kneaders, single-screw or twin-screw extruders, and open-roll type mixers can be used.

[0089] The melt-mixing temperature is not particularly limited as long as it is the temperature at which the resin melts and the raw materials mix together.

[0090] After the melt-kneading process, it is preferable to cool the kneaded material appropriately until it reaches a hardness that allows for pulverization, and then, if necessary, perform a pulverization process and a classification process to obtain toner particles. Here, cooling refers to cooling the kneaded material to a temperature between 0°C and 50°C, or to a temperature below the glass transition temperature of the binder resin in the kneaded material.

[0091] The toner of the present invention preferably contains an external additive to improve transferability. Examples of external additives include inorganic fine particles such as silica, alumina, titania, zirconia, tin oxide, and zinc oxide, and organic fine particles such as melamine resin fine particles and polytetrafluoroethylene resin fine particles, and two or more may be used in combination. Among these, silica is preferred, and from the viewpoint of toner transferability, hydrophobic silica that has been hydrophobicized is more preferred.

[0092] Examples of hydrophobic agents used to hydrophobize the surface of silica particles include hexamethyldisilazane (HMDS), dimethyldichlorosilane (DMDS), cyclic silazane, silicone oil, aminosilane, octyltriethoxysilane (OTES), and methyltriethoxysilane.

[0093] The average particle size of the external additive is preferably 10 nm or larger, more preferably 15 nm or larger, and more preferably 250 nm or smaller, more preferably 200 nm or smaller, and even more preferably 90 nm or smaller, from the viewpoint of the toner's chargeability, fluidity, and transferability.

[0094] External additive treatment, which involves mixing toner particles with external additives, can be carried out according to conventional methods, and a mixer such as a Henschel mixer can be used.

[0095] From the viewpoint of the toner's electrostatic properties, fluidity, and transferability, the content of the external additive is preferably 0.05 parts by mass or more, more preferably 0.1 parts by mass or more, even more preferably 0.3 parts by mass or more, and preferably 5 parts by mass or less, and more preferably 3 parts by mass or less, per 100 parts by mass of toner particles before treatment with the external additive.

[0096] The volume-intermediate particle size (D) of the toner of the present invention 50 The volume median particle size (D) is preferably 3 μm or more, more preferably 4 μm or more, and preferably 15 μm or less, more preferably 10 μm or less. 50) refers to the particle size at which the cumulative volume frequency calculated using volume fractions accounts for 50% when calculated from the smallest particle size. Furthermore, if the toner is treated with an external additive, the volume median particle size of the toner particles before treatment with the external additive is taken as the volume median particle size of the toner.

[0097] The toner of the present invention can be used as is as a one-component developing toner, or as a two-component developing toner used in combination with a carrier, in image forming apparatuses using either a one-component developing method or a two-component developing method, respectively. [Examples]

[0098] The present invention will be specifically described below with reference to examples, but the present invention is not limited in any way by these examples. The physical properties of resins, etc., can be measured by the following methods.

[0099] [Softening point of resins and resin compositions] Using a flow tester "CFT-500EX" (manufactured by Shimadzu Corporation), 1 g of sample is heated at a heating rate of 6°C / min while a load of 1.96 MPa is applied by a plunger, and the sample is 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 is plotted against temperature, and the temperature at which half of the sample has flowed out is defined as the softening point.

[0100] [Maximum peak temperature of endothermic reactions in resins and resin compositions] Using a differential scanning calorimeter "Q-100" (manufactured by T.A. Instruments Japan Co., Ltd.), 4.0-5.0 mg of the sample was weighed into an aluminum pan and cooled from room temperature (20°C) to 0°C at a rate of 10°C / min. The sample was then maintained at this temperature for 5 minutes. Subsequently, the endothermic peaks were measured while the temperature was increased to 180°C at a rate of 10°C / min. Among the observed endothermic peaks, the temperature of the peak with the largest peak area was defined as the maximum endothermic peak temperature.

[0101] [Glass transition temperature of resins and resin compositions] Using a differential scanning calorimeter "Q-100" (manufactured by T.A. Instruments Japan Co., Ltd.), 4.0 to 5.0 mg of the sample is weighed into an aluminum pan and heated from room temperature (20°C) to 200°C at a heating rate of 10°C / min, and then cooled to 0°C at a cooling rate of 10°C / min. Next, the sample is heated to 180°C at a heating rate of 10°C / min and the endothermic peak is measured. The temperature at the intersection of the baseline extension below the maximum endothermic peak temperature and the tangent line showing the maximum slope from the rise of the peak to the peak apex is defined as the glass transition temperature.

[0102] [Acid value of resins and resin compositions] The measurement will be performed according to the method of JIS K0070:1992. However, the measurement solvent will be changed from the mixed solvent of ethanol and ether specified in JIS K0070:1992 to a mixed solvent of acetone and toluene (acetone:toluene = 1:1 (volume ratio)).

[0103] [Oxidation-reduction potential of antioxidants] Cyclic voltammetry measurements will be performed using a WaveNano potentiostat (manufactured by Pine Research Instrumentation). The following materials will be used as the reference electrode, counter electrode, and working electrode. • Reference electrode: Silver / silver nitrate (As the electrolyte, use a 0.1 mol / L tetraalkylammonium tetrafluoroborate anhydrous acetonitrile solution (Solution A). Also, prepare a fresh 5 mmol / L silver nitrate anhydrous acetonitrile solution (Solution B). Place Solution B in a narrow glass tube with a glass filter at the bottom, and seal it with a rubber stopper into which a 0.5 mm diameter silver wire is inserted. Insert this into a 15 mm diameter glass tube with a glass filter at the bottom containing Solution A, and use this as the reference electrode.) • Counter electrode: Platinum wire • Working electrode: Platinum disc (1.6 mm in diameter) The oxidation potential of antioxidants is measured using a tetrahydrofuran (THF) solution (5 mmol / L) of the antioxidant. A 1 mol / L solution of tetrabutylammonium perchlorate (TBAP) is used as the supporting electrolyte. The reduction scan is performed using a 0.1 mol / L solution of TBAP in acetonitrile for each antioxidant's THF solution (5 mmol / L). Typically, three cycles (six divisions) are performed at a sweep rate of 20 mV / sec. Energy levels are corrected by a 4.7 V offset to convert them to vacuum levels. Using the method described above, a voltammogram is measured for a tetrahydrofuran (THF) solution (5 mmol / L) containing an antioxidant, and the resulting half-wave potential is defined as the redox potential.

[0104] [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 is 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 is heated at a rate of 10°C / min and the heat quantity is measured, with the maximum endothermic peak temperature being defined as the melting point.

[0105] [Average particle size of external additives] The average particle diameter refers to the number-average particle diameter, which is calculated by measuring the particle size (average of the major and minor axes) of 500 particles from scanning electron microscope (SEM) images and using the number-average value of these measurements.

[0106] [Medium particle size in toner volume] • Measuring instrument: "Coulter Multisizer (Registered Trademark) III" (manufactured by Beckman Coulter, Inc.) • Aperture diameter: 100 μm • Analysis software: "Multisizer III (registered trademark) Version 3.51" (manufactured by Beckman Coulter, Inc.) • Electrolyte: "Isoton (registered trademark) II" (manufactured by Beckman Coulter, Inc.) • Dispersion: Prepared by dissolving polyoxyethylene lauryl ether "Emulgen (registered trademark) 109P" [manufactured by Kao Corporation, HLB (Griffin) = 13.6] in the electrolyte to adjust the concentration to 5% by mass. • Dispersion conditions: Add 10 mg of the sample to 5 mL of the dispersion and disperse for 1 minute using an ultrasonic disperser (machine name: US-1 manufactured by SND Corporation, output: 80W). Then, add 25 mL of electrolyte and disperse for another minute using the ultrasonic disperser to prepare the sample dispersion. • Measurement conditions: The sample dispersion is added to 100 mL of the electrolyte to adjust the concentration so that the particle size of 30,000 particles can be measured in 20 seconds. Then, the 30,000 particles are measured, and the volume median particle size (D) is determined from the particle size distribution. 50 )

[0107] Manufacturing Example 1 of Resin Composition A 10-liter four-necked flask equipped with a thermometer, stainless steel stirring rod, a drop-flow condenser with a dehydration tube, and a nitrogen inlet tube contained the alcohol component, carboxylic acid components other than trimellitic anhydride, esterification catalyst, and co-catalyst shown in Tables 2, 3, and 5. Under a nitrogen atmosphere, the mixture was heated to 235°C with stirring and held for 4 hours. The pressure inside the flask was then reduced and held at 8 kPa for 1 hour. After that, the mixture was cooled to 210°C and returned to atmospheric pressure. The trimellitic anhydride and antioxidant shown in Tables 2, 3, and 5 were added, and the mixture was held at 210°C for 3 hours. The pressure inside the flask was then reduced further and the mixture was reacted at 16.7 kPa until the softening point reached the temperature shown in Tables 2, 3, and 5, yielding resin compositions (resin compositions A1-A7, A9, A11-A12, A19-A22) containing amorphous polyester resin and antioxidants. The physical properties of the obtained resin compositions are shown in Tables 2, 3, and 5.

[0108] Manufacturing Example 2 of Resin Composition A 10-liter four-necked flask equipped with a thermometer, stainless steel stirring rod, a drop-flow condenser with a dewatering tube, and a nitrogen inlet tube contained the alcohol component, carboxylic acid component, esterification catalyst, and co-catalyst shown in Table 3. Under a nitrogen atmosphere, the mixture was heated to 235°C with stirring and held for 4 hours. After that, it was cooled to 210°C and returned to atmospheric pressure. Then, the antioxidant shown in Table 3 was added, and the mixture was held at 210°C for 3 hours. Subsequently, the pressure in the flask was reduced, and the reaction was carried out at 16.7 kPa until the softening point reached the temperature shown in Table 3, yielding a resin composition (resin composition A8) containing amorphous polyester resin and antioxidant. The physical properties of the obtained resin composition are shown in Table 3.

[0109] Manufacturing Example 3 of Resin Composition A 10-liter four-necked flask equipped with a thermometer, stainless steel stirring rod, a drop-flow condenser with a dewatering tube, and a nitrogen inlet tube contained the alcohol component, carboxylic acid component, esterification catalyst, and co-catalyst shown in Table 3. Under a nitrogen atmosphere, the mixture was heated to 235°C with stirring and held for 2 hours. After that, it was cooled to 210°C and returned to atmospheric pressure. Then, the fumaric acid, polymerization inhibitor, and antioxidant shown in Table 3 were added, and the mixture was held at 210°C for 3 hours. Subsequently, the pressure in the flask was reduced, and the reaction was carried out at 16.7 kPa until the softening point reached the temperature shown in Table 3, yielding a resin composition (resin composition A10) containing amorphous polyester resin and antioxidant. The physical properties of the obtained resin composition are shown in Table 3.

[0110] Manufacturing example of resin composition 4 A 10-liter four-necked flask equipped with a thermometer, stainless steel stirring rod, a drop-flow condenser with a dehydration tube, and a nitrogen inlet tube contained the alcohol components shown in Table 4. The mixture was heated to 100°C, then terephthalic acid (shown in Table 4) was added, and the mixture was heated to 160°C while stirring under a nitrogen atmosphere. The two reactive monomers shown in Table 4, along with the styrene resin raw material monomers and polymerization initiator, were weighed in separate containers, stirred, and then added dropwise over 1 hour using a dropping funnel. After addition, the addition polymerization reaction was carried out for 1 hour while maintaining the temperature at 160°C. After further aging for 1 hour, the temperature was raised to 200°C and stirred at 8 kPa for 1 hour. Subsequently, the esterification catalyst and co-catalyst (shown in Table 4) were added, and polycondensation and addition polymerization reactions were carried out at 235°C for 10 hours. The pressure in the flask was then reduced and maintained at 8 kPa for 1 hour. Subsequently, the mixture was cooled to 210°C and returned to atmospheric pressure. The antioxidants shown in Table 4 were then added, and the mixture was maintained at 210°C for 3 hours. After that, the pressure in the flask was further reduced, and the mixture was reacted at 16.7 kPa until the softening point reached the temperature shown in Table 4, thereby obtaining a resin composition (resin composition A13) containing an amorphous composite resin and an antioxidant. The physical properties of the obtained resin composition are shown in Table 4.

[0111] Manufacturing Example 5 of Resin Compositions A 10-liter four-necked flask equipped with a thermometer, stainless steel stirring rod, a drop-flow condenser with a dewatering tube, and a nitrogen inlet tube contained the alcohol component, carboxylic acid components other than trimellitic anhydride, antioxidant, esterification catalyst, and co-catalyst shown in Table 4. Under a nitrogen atmosphere, the mixture was heated to 235°C with stirring and held for 4 hours. The pressure inside the flask was then reduced and held at 8 kPa for 1 hour. After that, the mixture was cooled to 210°C and returned to atmospheric pressure. Trimellitic anhydride as shown in Table 4 was added, and the mixture was held at 210°C for 3 hours. The pressure inside the flask was then reduced further and the mixture was reacted at 16.7 kPa until the softening point reached the temperature shown in Table 4, yielding amorphous polyester resin and resin compositions (resin compositions A14-A16) containing antioxidants. The physical properties of the obtained resin compositions are shown in Table 4.

[0112] Manufacturing example of resin composition 6 A 10-liter four-necked flask equipped with a thermometer, stainless steel stirring rod, a drop-flow condenser with a dewatering tube, and a nitrogen inlet tube contained the alcohol component, carboxylic acid component, antioxidant, esterification catalyst, and co-catalyst shown in Table 4. Under a nitrogen atmosphere, the mixture was heated to 235°C while stirring and held for 4 hours. Then, the pressure inside the flask was reduced to 16.7 kPa and the mixture was reacted until the softening point reached the temperature shown in Table 4, thereby obtaining a resin composition (resin composition A17) containing amorphous polyester resin and an antioxidant. The physical properties of the obtained resin composition are shown in Table 4.

[0113] Resin manufacturing example 1 A 10-liter four-necked flask equipped with a thermometer, stainless steel stirring rod, a drop-flow condenser with a dewatering tube, and a nitrogen inlet tube contained the raw material monomers other than trimellitic anhydride, the esterification catalyst, and the co-catalyst shown in Tables 4 and 5. Under a nitrogen atmosphere, the mixture was heated to 235°C with stirring and held for 4 hours. After that, the pressure in the flask was reduced and held at 8 kPa for 1 hour. Subsequently, the mixture was cooled to 210°C to return to atmospheric pressure. Then, trimellitic anhydride shown in Tables 4 and 5 was added, and the mixture was held at 210°C for 3 hours. After that, the pressure in the flask was further reduced to 16.7 kPa and the reaction was allowed to proceed until the softening point reached the temperature shown in Tables 4 and 5, yielding amorphous polyester resins (resin A18, resin B). The physical properties of the obtained resins are shown in Tables 4 and 5.

[0114] Details of the antioxidants used in the manufacture of the resin composition are shown in Table 1.

[0115] [Table 1]

[0116] [Table 2]

[0117] [Table 3]

[0118] [Table 4]

[0119] [Table 5]

[0120] Examples 1-17 and Comparative Examples 1-5 100 parts by mass of the binder resin shown in Table 6, 1 part by mass of the negative charge control agent "Bontron E-81" (manufactured by Orient Chemical Industry Co., Ltd.), 5 parts by mass of the coloring agent "Pigment blue 15:3" (manufactured by Dainichi Seika Kogyo Co., Ltd., phthalocyanine blue), and 2 parts by mass of the release agent "HNP-9" (manufactured by Nippon Seiro Co., Ltd., paraffin wax, melting point: 80°C) were thoroughly mixed in a Henschel mixer. Then, using a twin-screw extruder with a total length of 1560 mm in the mixing section, a screw diameter of 42 mm, and a barrel inner diameter of 43 mm, the mixture was melt-kneaded 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 resulting kneaded material was cooled and coarsely ground, then ground in a jet mill and classified to obtain the medium volume particle size (D 50 ) yielded toner particles with a diameter of 8 μm.

[0121] Toner was obtained by adding 1.0 part by mass of hydrophobic silica "AEROSIL NAX 50" (manufactured by Nippon Aerosil Co., Ltd., hydrophobic treatment agent: HMDS, average particle size: approximately 30 nm) as an external additive to 100 parts by mass of the obtained toner particles and mixing them in a Henschel mixer.

[0122] Test example [Transparency] A solid image was printed on an A4-sized OHP sheet (manufactured by Nakabayashi Co., Ltd., OHP film, double-sided dry copy for LBP). The resulting solid image was cut into 4cm x 5cm sections, and the light transmittance was measured using a spectrophotometer (manufactured by Nippon Denshoku Industries Co., Ltd., SE2000) to evaluate the transparency of the image. Transmittance was measured by first cutting an unprinted OHP sheet to 4cm x 5cm and fixing it to a jig with a measurement area of ​​30mmΦ. Background measurements were then taken of the unprinted OHP sheet, and then the absorbance of an OHP sheet with a solid image printed on it was measured using the same method. During this process, the OHP sheet was positioned so that the light was shone from the back of the printed side of the solid image. Measurement conditions were set to wavelength output intervals of 10nm in the range of 380~780nm. The absorbance at 480nm was evaluated as the transmittance of cyan. Transmittance was evaluated as transmittance = (absorbance at 480nm of the printed OHP sheet) / (absorbance at 480nm of the unprinted OHP sheet) × 100 (%). The results are shown in Table 6. Higher transmittance indicates higher transparency.

[0123] [Table 6]

[0124] From the above results, it can be seen that, in comparison with Comparative Examples 1 to 3, which do not contain antioxidants or whose oxidation-reduction potential is outside the specified range, and Comparative Examples 4 and 5, in which the acid value of the amorphous polyester resin or the content of the alkylene oxide adduct of bisphenol A is outside the specified range, highly transparent images were obtained in all of Examples 1 to 17. [Industrial applicability]

[0125] The toner for electrostatic image development containing the toner binder resin composition of the present invention is suitably used for developing latent images formed in electrostatic image development methods, electrostatic recording methods, electrostatic printing methods, and the like.

Claims

1. A toner binder resin composition comprising an amorphous polyester resin A and an antioxidant, wherein the amorphous polyester resin A is an amorphous composite resin obtained by bonding amorphous polyester resin a and / or amorphous polyester resin a and a styrene resin, the alcohol component of the amorphous polyester resin a contains 20 mol% or more of an alkylene oxide adduct of bisphenol A, the oxidation-reduction potential of the antioxidant is -0.5 V or more and 0.5 V or less, and the acid value of the toner binder resin composition is 5 mg KOH / g or more.

2. The binder resin composition for toner according to claim 1, wherein the antioxidant is a phosphorus-based antioxidant.

3. A toner for developing electrostatic images, comprising the toner binder resin composition described in claim 1 or 2.

Images