Toner for electrostatic charge image development

Abstract

To provide toner for electrostatic charge image development that is superior in suppression of fogging and stripes of an image which may be caused in a high-temperature, high-humidity environment.SOLUTION: The present invention relates to toner for electrostatic charge image development that contains toner base particles containing crystalline polyester resin C and noncrystalline polyester resin A, and external additives, wherein the crystalline polyester resin C is a polycondensation product of an alcohol component containing 80 mol% or more of ethylene glycol and a carboxylic acid component, and the external additives contain positively charged resin particulates P.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a toner for developing electrostatic images used in developing latent images formed in electrophotography, electrostatic recording, electrostatic printing, and the like. [Background technology]

[0002] As a binder resin for toner for developing electrostatic images, the use of a combination of an amorphous resin and a crystalline polyester resin has been studied from the viewpoint of low-temperature fixability and the like (see Patent Documents 1 and 2). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2010-224255 [Patent Document 2] Japanese Patent Application Publication No. 2023-13191 Summary of the Invention [Problem to be solved by the invention]

[0004] Toners usually contain external additives, which can easily cause fog and streaks after continuous printing. In particular, toners containing crystalline polyester resins have the problem of being prone to fog and streaks under high temperature and humidity conditions.

[0005] The present invention relates to a toner for developing electrostatic images that is excellent in suppressing image fog and streaks that occur under high temperature and high humidity conditions. [Means for solving the problem]

[0006] The present invention relates to a toner for developing electrostatic images, which contains toner base particles containing a crystalline polyester resin C and an amorphous polyester resin A, and an external additive, wherein the crystalline polyester resin C is a polycondensate of an alcohol component containing 80 mol % or more of ethylene glycol and a carboxylic acid component, and the external additive contains positively charged resin fine particles P. [Effects of the Invention]

[0007] The toner for developing electrostatic images of the present invention is highly effective in suppressing image fog and streaks that occur under high temperature and high humidity conditions. DETAILED DESCRIPTION OF THE INVENTION

[0008] The electrostatic image developing toner of the present invention is characterized in that it contains toner base particles containing crystalline polyester resin C and amorphous polyester resin A, and an external additive, the main component of the alcohol component of crystalline polyester resin C is ethylene glycol, and it contains positively charged resin fine particles P as an external additive. The reason why the electrostatic image developing toner of the present invention can suppress image fog and streaks that occur under high temperature and high humidity conditions is not clear, but is presumed as follows. Note that the following mechanism is presumed and is not limited thereto.

[0009] In a toner containing a crystalline polyester resin, the crystalline polyester resin melts in a high-temperature, high-humidity environment, becoming exposed to the toner particle surface, softening the particle surface, and causing aggregation between particles via moisture in the air, which tends to reduce the fluidity of the toner, resulting in significant degradation of image quality due to fog and streaks. However, in the present invention, the use of ethylene glycol having two carbon atoms in the crystalline polyester resin C brings the ester groups in the resin closer to each other, increasing the overlap of the molecular orbitals, and as a result, stabilizing the charge on the ester groups. Furthermore, since the ester group is generally a functional group that tends to be negatively charged, the negative chargeability of the crystalline polyester resin C is enhanced. By externally adding positively charged resin particles P to the surface of toner base particles containing this highly negatively charged crystalline polyester resin C, the resin particles P adhere strongly electrostatically, thereby exerting a spacer effect between toner particles and suppressing detachment from the toner base particles. As a result, detachment of the external additives from the toner is suppressed even under stress during printing, and it is thought that the occurrence of fog and streaks is suppressed.

[0010] The crystalline polyester resin C is a polycondensation product of an alcohol component and a carboxylic acid component, and the alcohol component contains ethylene glycol as a main component.

[0011] From the viewpoint of low-temperature fixability and hydrophilicity, the content of ethylene glycol in the alcohol component is 80 mol% or more, preferably 90 mol% or more, more preferably 95 mol% or more, and 100 mol% or less. When the alcohol component contains an aliphatic monoalcohol, the content is preferably 99 mol% or less, more preferably 98 mol% or less.

[0012] Examples of alcohol components other than ethylene glycol include aliphatic diols other than ethylene glycol such as 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, neopentyl glycol, 1,9-nonanediol, 1,10-decanediol, 1,11-undecanediol, and 1,12-dodecanediol; aromatic diols such as alkylene oxide adducts of bisphenol A; bisphenol A, hydrogenated bisphenol A, sorbitol, pentaerythritol, glycerin, and trimethylolpropane; and trihydric or higher alcohols.

[0013] The carboxylic acid component preferably contains an aliphatic dicarboxylic acid compound.

[0014] Examples of aliphatic dicarboxylic acid compounds include succinic acid (carbon number: 4), fumaric acid (carbon number: 4), adipic acid (carbon number: 6), suberic acid (carbon number: 8), azelaic acid (carbon number: 9), sebacic acid (carbon number: 10), dodecanedioic acid (carbon number: 12), tetradecanedioic acid (carbon number: 14), anhydrides of these acids, and alkyl esters of these acids having 1 to 3 carbon atoms. In the present invention, the carboxylic acid compounds include not only free acids but also anhydrides that decompose during the reaction to produce acids, and alkyl esters having 1 to 3 carbon atoms.

[0015] From the viewpoint of hydrophobicity, the carbon number of the aliphatic dicarboxylic acid compound is preferably 6 or more, more preferably 9 or more, and from the viewpoint of low-temperature fixability, it is preferably 14 or less, more preferably 12 or less. When the aliphatic dicarboxylic acid compound is an alkyl ester, the carbon number of the alkyl group is not included in the above carbon number.

[0016] The content of the aliphatic dicarboxylic acid compound in the carboxylic acid component is preferably 50 mol% or more, more preferably 60 mol% or more, even more preferably 70 mol% or more, and even more preferably 80 mol% or more, and is 100 mol% or less. When the carboxylic acid component contains an aliphatic monocarboxylic acid compound, the content is preferably 99 mol% or less, more preferably 98 mol% or less.

[0017] Examples of other carboxylic acid components include aromatic dicarboxylic acid compounds such as phthalic acid, isophthalic acid, and terephthalic acid, and trivalent or higher carboxylic acid compounds such as trimellitic acid and pyromellitic acid.

[0018] From the viewpoint of improving hydrophobicity, the alcohol component and / or the carboxylic acid component of the crystalline polyester resin C preferably further contains a monofunctional monomer.

[0019] From the viewpoint of improving crystallinity, the monofunctional monomer preferably contains an aliphatic monocarboxylic acid compound and / or an aliphatic monoalcohol, and more preferably contains an aliphatic monocarboxylic acid compound.

[0020] Examples of the aliphatic monoalcohol contained in the alcohol component include capryl alcohol, capric alcohol, lauryl alcohol, myristyl alcohol, palmityl alcohol, stearyl alcohol, and behenyl alcohol.

[0021] The carbon number of the aliphatic monoalcohol is preferably 6 or more, more preferably 9 or more, even more preferably 10 or more, and even more preferably 12 or more from the viewpoint of hydrophobicity, and is preferably 24 or less, more preferably 23 or less, and even more preferably 22 or less from the viewpoint of low-temperature fixability.

[0022] Examples of the aliphatic monocarboxylic acid compounds contained in the carboxylic acid component include aliphatic monocarboxylic acids such as caproic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, and behenic acid, and alkyl esters of these acids in which the alkyl group has 1 to 3 carbon atoms.

[0023] From the viewpoint of hydrophobicity, the carbon number of the aliphatic monocarboxylic acid compound is preferably 6 or more, more preferably 9 or more, and even more preferably 10 or more, and from the viewpoint of low-temperature fixability, it is preferably 24 or less, more preferably 23 or less, and even more preferably 22 or less. When the aliphatic monocarboxylic acid compound is an alkyl ester, the carbon number of the alkyl group is not included in the above carbon number.

[0024] The content of the monofunctional monomer is preferably 2 mol% or more, more preferably 3 mol% or more, and even more preferably 5 mol% or more of the total amount of the alcohol component and the carboxylic acid component, and from the viewpoint of storage stability, it is preferably 30 mol% or less, more preferably 25 mol% or less, and even more preferably 20 mol% or less.

[0025] In this specification, macromonomers and hydroxycarboxylic acids are not included in the alcohol component and carboxylic acid component.

[0026] The equivalent ratio of the carboxyl groups of the carboxylic acid component to the hydroxyl groups of the alcohol component (COOH groups / OH groups) is preferably 0.8 or more, more preferably 0.9 or more, from the viewpoint of charging stability, and is preferably 1.2 or less, more preferably 1.1 or less, from the viewpoint of low-temperature fixability.

[0027] Crystalline polyester resin C 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, a polymerization inhibitor, etc., at a temperature preferably of 120°C or higher and 230°C or lower.

[0028] Examples of the esterification catalyst include tin compounds such as dibutyltin oxide and tin(II) 2-ethylhexanoate, and titanium compounds such as titanium diisopropoxybis(triethanolaminate). The amount of the esterification catalyst used is preferably 0.01 parts by mass or more, more preferably 0.1 parts by mass or more, and preferably 1.5 parts by mass or less, more preferably 1 part by mass or less, per 100 parts by mass of the total amount of the alcohol component and the carboxylic acid component. Examples of the co-catalyst for the esterification catalyst include gallic acid. The amount of the 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, more preferably 0.1 parts by mass or less, per 100 parts by mass of the total amount of the alcohol component and the carboxylic acid component. Examples of the polymerization inhibitor include tert-butylcatechol. The amount of the polymerization inhibitor used is preferably 0.001 part by mass or more, more preferably 0.01 part by mass or more, and preferably 0.5 part by mass or less, more preferably 0.1 part by mass or less, relative to 100 parts by mass of the total amount of the alcohol component and the carboxylic acid component.

[0029] In the present invention, the polyester resin may be modified to such an extent that its properties are not substantially impaired. Examples of modified polyester resins include polyester resins grafted or blocked with phenol, urethane, epoxy, or the like, by the methods described in JP-A Nos. 11-133668, 10-239903, and 8-20636. Among the modified polyester resins, urethane-modified polyester resins in which polyester resins are urethane-extended with a polyisocyanate compound are preferred.

[0030] The softening point of the crystalline polyester resin C is preferably 50°C or higher, more preferably 65°C or higher, and even more preferably 70°C or higher from the viewpoint of charging stability, and is preferably 120°C or lower, more preferably 110°C or lower from the viewpoint of low-temperature fixability.

[0031] The crystallinity of a resin is expressed by a crystallinity index defined as the ratio of the softening point to the maximum endothermic peak temperature measured by a differential scanning calorimeter, that is, the value of [softening point / maximum endothermic peak temperature]. The crystalline resin has a crystallinity index of 0.6 or more, preferably 0.7 or more, more preferably 0.9 or more, and 1.4 or less, preferably 1.2 or less, more preferably 1.1 or less. On the other hand, an amorphous resin is a resin in which no endothermic peak is observed, or if an endothermic peak is observed, the resin has a crystallinity index of more than 1.4, preferably more than 1.5, more preferably 1.6 or more, or less than 0.6, preferably 0.5 or less. The crystallinity of a resin can be adjusted by the types and ratios of raw material monomers, and production conditions (e.g., reaction temperature, reaction time, cooling rate), etc. The maximum endothermic peak temperature refers to the temperature of the peak with the largest peak area among the observed endothermic peaks. For crystalline resins, the maximum endothermic peak temperature is the melting point.

[0032] The melting point of the crystalline polyester resin C is preferably 60°C or higher, more preferably 70°C or higher, from the viewpoint of storage stability, and is preferably 130°C or lower, more preferably 120°C or lower, from the viewpoint of low-temperature fixability.

[0033] From the viewpoint of charging stability, the acid value of the crystalline polyester resin C is preferably 1 mgKOH / g or more, more preferably 3 mgKOH / g or more, and preferably 20 mgKOH / g or less, more preferably 15 mgKOH / g or less.

[0034] The content of crystalline polyester resin C is preferably 3% by mass or more, more preferably 5% by mass or more, and even more preferably 8% by mass or more, of the total amount of crystalline polyester resin C and amorphous polyester resin A, from the viewpoint of low-temperature fixability, and is preferably 30% by mass or less, more preferably 25% by mass or less, and even more preferably 20% by mass or less, from the viewpoint of heat-resistant storage stability and charging stability.

[0035] The amorphous polyester resin is preferably an amorphous polyester resin or an amorphous composite resin in which a polyester resin is bonded to a styrene resin.

[0036] As the amorphous polyester resin, a polycondensation product of an alcohol component and a carboxylic acid component, including an alkylene oxide adduct of bisphenol A, is preferred.

[0037] Examples of alkylene oxide adducts of bisphenol A include those represented by the formula (I):

[0038] [ka]

[0039] (wherein OR and RO are oxyalkylene groups, R is an ethylene group and / or a propylene group, x and y are the average number of moles of alkylene oxide added and are each a positive number, and the sum of x and y is 1 or more, preferably 1.5 or more, and 16 or less, preferably 8 or less, more preferably 6 or less, and even more preferably 4 or less.) A compound represented by the following formula is preferred.

[0040] From the viewpoint of low-temperature fixability, the content of the alkylene oxide adduct of bisphenol A in the alcohol component is preferably 70 mol% or more, more preferably 80 mol% or more, even more preferably 90 mol% or more, and even more preferably 95 mol% or more, but 100 mol% or less.

[0041] Examples of other alcohol components include diols such as aliphatic diols, bisphenol A, and hydrogenated bisphenol A, and trihydric or higher alcohols such as sorbitol, pentaerythritol, glycerin, and trimethylolpropane.

[0042] Examples of the carboxylic acid component include aromatic dicarboxylic acid compounds, aliphatic dicarboxylic acid compounds, and trivalent or higher carboxylic acid compounds.

[0043] Examples of aromatic dicarboxylic acid compounds include phthalic acid, isophthalic acid, terephthalic acid, anhydrides of these acids, and alkyl esters of these acids having 1 to 3 carbon atoms.

[0044] Examples of the aliphatic dicarboxylic acid compound include fumaric acid, maleic acid, succinic acid, succinic acid derivatives substituted with a hydrocarbon group, glutaric acid, adipic acid, sebacic acid, anhydrides of these acids, and alkyl esters of these acids having 1 to 3 carbon atoms.

[0045] Examples of the trivalent or higher carboxylic acid compound include trimellitic acid, pyromellitic acid, anhydrides of these acids, and alkyl esters of these acids having 1 to 3 carbon atoms.

[0046] The alcohol component may contain a monohydric alcohol, and the carboxylic acid component may contain a monocarboxylic acid compound, as appropriate.

[0047] The equivalent ratio of the carboxyl groups of the carboxylic acid component to the hydroxyl groups of the alcohol component (COOH groups / OH groups) is preferably 0.6 or more, more preferably 0.7 or more, even more preferably 0.8 or more, from the viewpoint of adjusting the softening point of the polyester resin, and is preferably 1.3 or less, more preferably 1.2 or less.

[0048] The polycondensation reaction conditions of the alcohol component and the carboxylic acid component of the amorphous polyester resin are the same as those of the crystalline polyester resin, except that the reaction temperature is preferably 160°C or higher, more preferably 180°C or higher, and 250°C or lower, more preferably 240°C or lower.

[0049] The polyester resin in the composite resin is similar to the amorphous polyester resin described above, and 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").

[0050] The content of the styrene compound, preferably styrene, in the raw material monomers of the styrene-based resin is preferably 50% by mass or more, more preferably 70% by mass or more, and even more preferably 80% by mass or more from the viewpoint of storage stability, and is preferably 95% by mass or less, more preferably 93% by mass or less, and even more preferably 90% by mass or less from the viewpoint of low-temperature fixability.

[0051] The styrene-based resin may also contain, as a raw material monomer, a (meth)acrylic acid alkyl ester having an alkyl group with 7 or more carbon atoms. Examples of (meth)acrylic acid alkyl 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 both the presence and absence of this group, and indicates normal when this group is not present. Furthermore, "(meth)acrylic acid" refers to acrylic acid, methacrylic acid, or both.

[0052] From the viewpoint of improving the low-temperature fixability of the toner, the number of carbon atoms in the alkyl group in the (meth)acrylic acid alkyl ester as a raw material monomer for the styrene-based resin is preferably 7 or more, more preferably 8 or more, and preferably 12 or less, more preferably 10 or less. The number of carbon atoms in the alkyl ester refers to the number of carbon atoms derived from the alcohol component constituting the ester.

[0053] The raw material monomers for styrene-based resins may include raw material monomers other than styrene compounds and (meth)acrylic acid alkyl esters, for example, ethylenically unsaturated monoolefins such as ethylene and propylene; diolefins such as butadiene; halovinyls such as vinyl chloride; vinyl esters such as vinyl acetate and vinyl propionate; ethylenic 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.

[0054] The addition polymerization reaction of raw material monomers for styrene-based resins can be carried out by a conventional method in the presence of a polymerization initiator such as dibutyl peroxide or dicumyl peroxide, a chain transfer agent, a crosslinking agent, 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.

[0055] When an organic solvent is used in the addition polymerization reaction, xylene, toluene, methyl ethyl ketone, acetone, etc. can be used. The amount of the organic solvent used is preferably 10 parts by mass or more and 50 parts by mass or less per 100 parts by mass of the raw material monomer of the styrene-based resin.

[0056] The composite resin is preferably a resin in which a polyester resin and a styrene-based resin are bonded together, and more preferably a resin in which a polyester resin and a styrene-based resin are chemically bonded together via a bireactive monomer that can react with both the raw material monomers of the polyester resin and the raw material monomers of the styrene-based resin.

[0057] The bireactive monomer is preferably a compound having at least one functional group selected from the group consisting of hydroxyl, carboxyl, epoxy, primary amino, and secondary amino groups, preferably a hydroxyl and / or carboxyl group, more preferably a carboxyl group, and an ethylenically unsaturated bond in the molecule, more preferably at least one selected from the group consisting of acrylic acid, methacrylic acid, fumaric acid, maleic acid, and maleic anhydride, and from the viewpoint of the reactivity of polycondensation reactions and addition polymerization reactions, even more preferably at least one selected from the group consisting of acrylic acid, methacrylic acid, and fumaric acid. However, when used together with a polymerization inhibitor, a polycarboxylic acid compound having an ethylenically unsaturated bond, such as fumaric acid, functions as a raw material monomer for polyester resin. In this case, fumaric acid, etc., is not a bireactive monomer but a raw material monomer for polyester resin.

[0058] The amount of the bireactive monomer used is preferably 1 mol or more, more preferably 2 mol or more, relative to 100 mol of the total alcohol components of the polyester resin, from the viewpoint of increasing the dispersibility of the styrene resin and the polyester resin and improving the dispersibility of the raw materials in the toner, and is preferably 30 mol or less, more preferably 20 mol or less, and even more preferably 10 mol or less, from the viewpoint of improving the low-temperature fixability of the toner.

[0059] Specifically, the composite resin is preferably produced by the following method: When a bireactive monomer is used, the bireactive monomer is preferably used together with a raw material monomer of a styrene-based resin, from the viewpoint of improving the dispersibility of the raw material in the toner and the low-temperature fixability of the toner.

[0060] (i) A method in which step (A) of polycondensation reaction of raw material monomers of polyester resin is followed by step (B) of addition polymerization reaction of raw material monomers of styrene-based resin. In this method, step (A) is carried out under reaction temperature conditions suitable for polycondensation reaction, and then the reaction temperature is lowered and step (B) is carried out under temperature conditions suitable for addition polymerization reaction. The raw material monomer for the styrene-based resin is preferably added to the reaction system at a temperature suitable for addition polymerization reaction. When a bireactive monomer is used together with the raw material monomer for the styrene-based resin, the bireactive monomer undergoes addition polymerization reaction and also reacts with the polyester resin. After step (B), the reaction temperature is raised again, and if necessary, a raw material monomer of a trivalent or higher polyester resin that serves as a crosslinking agent is added to the polymerization system, thereby further promoting the polycondensation reaction of step (A) and the reaction with the bireactive monomer.

[0061] (ii) A method in which step (B) of an addition polymerization reaction using raw material monomers for a styrene-based resin is followed by step (A) of a polycondensation reaction using raw material monomers for a polyester resin. In this method, step (B) is carried out under reaction temperature conditions suitable for an addition polymerization reaction, and then the reaction temperature is raised to carry out the polycondensation reaction in step (A) under temperature conditions suitable for a polycondensation reaction. When a bireactive monomer is used together with the raw material monomer for the styrene resin, the bireactive monomer participates 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 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.

[0062] (iii) A method in which the step (A) of polycondensation reaction of raw material monomers for polyester resin and the step (B) of addition polymerization reaction of raw material monomers for styrene resin are carried out under conditions in which the reactions proceed in parallel. In this method, it is preferable to carry out steps (A) and (B) in parallel under reaction temperature conditions suitable for the addition polymerization reaction, raise the reaction temperature, and add a raw material monomer of the trivalent or higher polyester resin that serves as a crosslinking agent to the polymerization system as needed under temperature conditions suitable for the polycondensation reaction, and then further carry out the polycondensation reaction of step (A). In this case, under temperature conditions suitable for the polycondensation reaction, it is also possible to add a polymerization inhibitor and proceed with just the polycondensation reaction. When a bireactive monomer is used, the bireactive monomer participates in both the addition polymerization reaction and the polycondensation reaction.

[0063] In the above method (i), a prepolymerized polycondensation resin may be used instead of the polycondensation reaction in step (A). In the above method (iii), when the reaction is carried out under conditions in which steps (A) and (B) proceed in parallel, a mixture containing raw material monomers for the styrene resin may be added dropwise to a mixture containing raw material monomers for the polyester resin to cause the reaction.

[0064] The above methods (i) to (iii) are preferably carried out in the same container.

[0065] The mass ratio of the polyester resin to the styrene-based resin in the composite resin (polyester resin / styrene-based resin) is preferably 60 / 40 or more, more preferably 70 / 30 or more, and even more preferably 75 / 25 or more, from the viewpoint of low-temperature fixability. Also, from the viewpoint of improving the dispersibility of the raw materials in the toner, it is preferably 98 / 2 or less, more preferably 95 / 5 or less, and even more preferably 90 / 10 or less. In the above calculation, the mass of the polyester resin is the mass of the raw material monomers of the polyester resin used, minus the amount of reaction water (calculated value) dehydrated by the polycondensation reaction, and the amount of the bireactive monomer is included in the amount of raw material monomers of the polyester resin. The amount of the styrene-based resin is the total amount of the raw material monomers of the styrene-based resin.

[0066] The softening point of the amorphous polyester resin A is preferably 70°C or higher, more preferably 90°C or higher, and even more preferably 100°C or higher from the viewpoint of charging stability, and is preferably 170°C or lower, more preferably 160°C or lower, and even more preferably 150°C or lower from the viewpoint of low-temperature fixability.

[0067] From the viewpoint of low-temperature fixability and fixation width, the amorphous polyester resin A may be composed of resins with different softening points. The difference in softening point between the two resins is preferably 10°C or more, more preferably 20°C or more, and is preferably 60°C or less, more preferably 45°C or less.

[0068] The softening point of the amorphous polyester resin having a higher softening point (resin AH) is preferably 100°C or higher, more preferably 110°C or higher, even more preferably 120°C or higher, and even more preferably 130°C or higher, from the viewpoint of fixing width, and is preferably 170°C or lower, more preferably 160°C or lower, from the viewpoint of low-temperature fixability.

[0069] Furthermore, the softening point of the amorphous polyester resin (resin AL) having the lower softening point is preferably 70°C or higher, more preferably 90°C or higher, and even more preferably 100°C or higher, from the viewpoint of charging stability, and is preferably 130°C or lower, more preferably 125°C or lower, and even more preferably 120°C or lower, from the viewpoint of low-temperature fixability.

[0070] The mass ratio of resin AH to resin AL (resin AH / resin AL) is preferably 50 / 50 or more, more preferably 60 / 40 or more, even more preferably 65 / 35 or more, and preferably 90 / 10 or less, more preferably 80 / 20 or less, even more preferably 75 / 25 or less.

[0071] The glass transition temperature of the amorphous polyester resin A is preferably 40°C or higher, more preferably 50°C or higher, from the viewpoint of charging stability, and is preferably 80°C or lower, more preferably 70°C or lower, from the viewpoint of low-temperature fixability.

[0072] The acid value of the amorphous polyester resin A is preferably 10 mgKOH / g or more, more preferably 15 mgKOH / g or more, from the viewpoint of low-temperature fixability, and is preferably 40 mgKOH / g or less, more preferably 35 mgKOH / g or less, from the viewpoint of charging stability.

[0073] From the viewpoint of charging stability, the content of amorphous polyester resin A in the total amount of crystalline polyester resin C and amorphous polyester resin A is preferably 70% by mass or more, more preferably 75% by mass or more, even more preferably 80% by mass or more, and is preferably 97% by mass or less, more preferably 95% by mass or less, even more preferably 92% by mass or less.

[0074] From the viewpoint of charging stability, the mass ratio of crystalline polyester resin C to amorphous polyester resin A (crystalline polyester resin C / amorphous polyester resin A) is preferably 3 / 97 or more, more preferably 5 / 95 or more, even more preferably 8 / 92 or more, and is preferably 30 / 70 or less, more preferably 25 / 75 or less, even more preferably 20 / 80 or less.

[0075] In the toner, the crystalline polyester resin C and the amorphous polyester resin A are contained as binder resins.

[0076] Other binder resins include vinyl resins such as styrene acrylic resin, epoxy resin, polycarbonate, polyurethane, and composite resins containing two or more of these resins.

[0077] The total content of the crystalline polyester resin C and the amorphous polyester resin A in the binder resin is preferably 70% by mass or more, more preferably 80% by mass or more, even more preferably 90% by mass or more, and even more preferably 95% by mass or more, but 100% by mass or less.

[0078] The content of the binder resin in the toner is preferably 60% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, and is preferably less than 100% by mass, more preferably 98% by mass or less, even more preferably 95% by mass or less.

[0079] The toner for developing electrostatic images of the present invention may contain additives such as a colorant, a release agent, a charge control agent, a magnetic powder, a flowability improver, a conductivity adjuster, a reinforcing filler such as a fibrous substance, an antioxidant, and a cleaning property improver, in addition to the binder resin (binder).

[0080] As the colorant, dyes, pigments, magnetic materials, etc. used as toner colorants can be used. Examples include carbon black, phthalocyanine blue, permanent brown FG, brilliant fast scarlet, pigment red 122, pigment green B, rhodamine-B base, solvent red 49, solvent red 146, solvent blue 35, quinacridone, carmine 6B, isoindoline, disazo yellow, etc. In the present invention, the toner may be either a black toner or a color toner.

[0081] From the viewpoint of improving the image density and low-temperature fixability of the toner, the content of the colorant is preferably 1 part by mass or more, more preferably 2 parts by mass or more, and preferably 40 parts by mass or less, more preferably 20 parts by mass or less, and even more preferably 10 parts by mass or less, relative to 100 parts by mass of the binder resin.

[0082] Examples of the release agent include hydrocarbon waxes such as polypropylene wax, polyethylene wax, ethylene-propylene copolymer wax, microcrystalline wax, paraffin wax, and Fischer-Tropsch wax, and oxides thereof; ester waxes such as carnauba wax, montan wax, and deacidified waxes thereof, and fatty acid ester wax; fatty acid amides, fatty acids, higher alcohols, and fatty acid metal salts, and these may be used alone or in combination of two or more.

[0083] The melting point of the release agent is preferably 60°C or higher, more preferably 70°C or higher, from the viewpoint of charge stability, and is preferably 160°C or lower, more preferably 140°C or lower, even more preferably 120°C or lower, and even more preferably 110°C or lower, from the viewpoint of low-temperature fixability.

[0084] From the viewpoint of the charge stability of the toner and the dispersibility in the binder resin, the content of the release agent is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, and even more preferably 1.5 parts by mass or more, relative to 100 parts by mass of the binder resin, and is preferably 10 parts by mass or less, more preferably 8 parts by mass or less, and even more preferably 7 parts by mass or less.

[0085] The charge control agent is not particularly limited, and may contain either a positively chargeable charge control agent or a negatively chargeable charge control agent.

[0086] Examples of positively chargeable 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 Co., Ltd.); triphenylmethane dyes containing a tertiary amine as a side chain; quaternary ammonium salt compounds such as "Bontron P-51" (manufactured by Orient Chemical Industries Co., Ltd.), cetyltrimethylammonium bromide, and "COPY CHARGE PX Examples of suitable resins include polyamine resins such as "AFP-B" (manufactured by Orient Chemical Industries Co., Ltd.); imidazole derivatives such as "PLZ-2001" and "PLZ-8001" (both manufactured by Shikoku Chemical Industry Co., Ltd.); and styrene-acrylic resins such as "FCA-701PT" and "FCA-201-PS" (manufactured by Fujikura Chemical Industries Co., Ltd.).

[0087] Examples of negatively chargeable charge control agents include metal-containing azo dyes such as "Balifast 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 benzilic acid compounds such as "LR-147" and "LR-297" (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 VP434 (manufactured by Clariant), nitroimidazole derivatives, etc.; organometallic compounds, etc.

[0088] 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, relative to 100 parts by mass of the binder resin. When the charge control agent is a resin (polymer type), the content is preferably 3 parts by mass or more, more preferably 5 parts by mass or more, and preferably 20 parts by mass or less, more preferably 15 parts by mass or less, relative to 100 parts by mass of the binder resin.

[0089] The toner base particles may be obtained by any conventionally known method such as a melt-kneading method, an emulsion aggregation method, or a suspension polymerization method, but from the viewpoint of charge stability, a pulverized toner obtained by a melt-kneading method is preferred. In the case of a pulverized toner obtained by a melt-kneading method, for example, raw materials such as a binder resin containing a crystalline polyester resin C and an amorphous polyester resin A, and, if necessary, a colorant, a release agent, and a charge control agent are uniformly mixed in a mixer such as a Henschel mixer, and then melt-kneaded in an internal kneader, a single-screw or twin-screw extruder, an open-roll kneader, or the like, followed by cooling, pulverization, and classification to produce the toner.

[0090] The volume median particle size of the toner base particles (D 50 ) is preferably 3 μm or more, more preferably 4 μm or more, and is preferably 15 μm or less, more preferably 10 μm or less. 50 ) means the particle size at which the cumulative volume frequency calculated by volume fraction is 50% calculated from the smallest particle size.

[0091] The external additive contains positively charged resin fine particles P.

[0092] From the viewpoint of suppressing fogging and streaks, the resin particles P preferably contain a polymethyl methacrylate resin.

[0093] Examples of polymethyl methacrylate resins include polymers of methyl methacrylate and copolymers of methyl methacrylate with other monomers. Examples of other monomers include styrene and butyl acrylate. The content of methyl methacrylate units in the polymethyl methacrylate resin is preferably 60 mol% or more, more preferably 80 mol% or more, and even more preferably 90 mol% or more, and 100 mol% or less, of the monomer units.

[0094] Other positively charged resin particles include melamine-formaldehyde resin, benzoguanamine-formaldehyde resin, benzoguanamine-melamine-formaldehyde resin, styrene (St) / methyl methacrylate (MMA) copolymer, St / butyl acrylate (BA) copolymer, MMA / BA copolymer, etc.

[0095] The number average particle diameter of the resin fine particles P is preferably 150 nm or more, more preferably 250 nm or more, and is preferably 600 nm or less, more preferably 500 nm or less.

[0096] The content of the resin particles P is preferably 0.01 parts by mass or more, more preferably 0.03 parts by mass or more, and even more preferably 0.07 parts by mass or more, relative to 100 parts by mass of the toner base particles, and from the viewpoint of low-temperature fixability, is preferably 2 parts by mass or less, more preferably 1 part by mass or less, even more preferably 0.5 parts by mass or less, even more preferably 0.3 parts by mass or less, and even more preferably 0.15 parts by mass or less.

[0097] Furthermore, the content of resin fine particles P relative to 100 parts by mass of crystalline polyester resin C is preferably 0.1 parts by mass or more, more preferably 0.4 parts by mass or more, even more preferably 0.8 parts by mass or more, and is preferably 50 parts by mass or less, more preferably 10 parts by mass or less, even more preferably 3 parts by mass or less.

[0098] From the viewpoint of toner fluidity, the external additive preferably further contains inorganic fine particles. The content of the resin fine particles P in the external additive is preferably 0.5% by mass or more, more preferably 1.5% by mass or more, and even more preferably 3% by mass or more, and is preferably 20% by mass or less, more preferably 10% by mass or less, and even more preferably 5% by mass or less.

[0099] Examples of inorganic fine particles include silica, alumina, titania, zirconia, strontium titanate, tin oxide, zinc oxide, etc. Among these, silica is preferred, and from the viewpoint of toner transferability, hydrophobic silica that has been subjected to a hydrophobic treatment is more preferred.

[0100] Examples of hydrophobic treatment agents for hydrophobizing the surfaces of silica particles include hexamethyldisilazane (HMDS), dimethyldichlorosilane (DMDS), cyclic silazanes, silicone oils, aminosilanes, octyltriethoxysilane (OTES), and methyltriethoxysilane.

[0101] The inorganic fine particles may be positively or negatively charged.

[0102] From the viewpoint of adhesive strength, the number average particle size of the inorganic fine particles is preferably 10 nm or more, more preferably 15 nm or more, and preferably 120 nm or less, more preferably 80 nm or less, and even more preferably 50 nm or less.

[0103] From the viewpoint of the chargeability, fluidity, and transferability of the toner, the content of the inorganic fine particles is preferably 0.05 parts by mass or more, more preferably 0.1 parts by mass or more, and even more preferably 0.3 parts by mass or more, relative to 100 parts by mass of the toner base particles, and is preferably 8 parts by mass or less, and more preferably 5 parts by mass or less.

[0104] The external addition treatment by mixing the toner base particles with the external additives can be carried out according to a conventional method, and a mixer such as a Henschel mixer can be used. The resin fine particles P and the inorganic fine particles may be mixed with the toner base particles at the same time or separately, but the former is preferred from the viewpoint of charging stability.

[0105] The toner of the present invention can be used as a toner for one-component development as it is, or as a toner for two-component development mixed with a carrier, in an image forming apparatus of a one-component development system or a two-component development system, respectively. [Example]

[0106] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. Physical properties of resins and the like can be measured by the following methods.

[0107] [Softening point of resin] Using a flow tester "CFT-500D" (Shimadzu Corporation), 1 g of sample is heated at a temperature increase rate of 6°C / min while applying a load of 1.96 MPa with the plunger, and extruding it from a nozzle 1 mm in diameter and 1 mm in length. The plunger depression distance of the flow tester is plotted against the temperature, and the temperature at which half of the sample flows out is taken as the softening point.

[0108] [Maximum endothermic peak temperature of resin] Using a differential scanning calorimeter "Q-100" (TA Instruments Japan Co., Ltd.), 0.02 g of sample is weighed into an aluminum pan, cooled from room temperature (25°C) to 0°C at a rate of 10°C / min, and maintained at 0°C for 1 minute. Then, measurements are taken at a rate of 10°C / min. The temperature of the peak with the largest peak area among the observed endothermic peaks is taken as the maximum endothermic peak temperature. For crystalline resins, the maximum endothermic peak temperature is taken as the melting point.

[0109] [Glass transition temperature of resin] Using a differential scanning calorimeter "Q-100" (TA Instruments Japan), 0.02 g of sample is weighed into an aluminum pan, heated to 200°C, and cooled to 0°C at a rate of 10°C / min. The sample is then heated at a rate of 10°C / min, and the endothermic peak is measured. The glass transition temperature is the temperature at the intersection of an extension of the baseline below the maximum endothermic peak temperature and a tangent line showing the maximum slope from the rising part of the peak to the peak apex.

[0110] [Acid value of resin] Measurements are made based on the method of JIS K 0070:1992, except that the measurement solvent is changed from the ethanol and ether mixture specified in JIS K 0070 to a mixture of acetone and toluene (acetone:toluene = 1:1 (volume ratio)) for amorphous resins, and to a mixture of chloroform and dimethylformamide (chloroform:dimethylformamide = 7:3 (volume ratio)) for crystalline resins.

[0111] [Melting point of release agent] Using a differential scanning calorimeter "Q-100" (TA Instruments Japan), 0.02 g of 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. The sample is then heated at a rate of 10°C / min, the calorific value is measured, and the maximum endothermic peak temperature is taken as the melting point.

[0112] [Solid Content Concentration of Resin Dispersion, Colorant Dispersion, and Release Agent Dispersion] Using an infrared moisture meter "FD-230" (Kett Electric Laboratory Co., Ltd.), 5 g of the measurement sample is dried at a drying temperature of 150°C and measurement mode 96 (monitoring time 2.5 minutes, fluctuation range 0.05%), and the moisture content (mass%) of the dispersion is measured. The solid content concentration is calculated according to the following formula. Solid content concentration (mass%) = 100-moisture (mass%)

[0113] [Volume Median Particle Size and CV Value of Resin Particles, Colorant Particles, and Release Agent Particles] (1) Measuring device: Laser diffraction particle size measuring instrument "LA-920" (manufactured by Horiba, Ltd.) (2) Measurement conditions: Put the sample dispersion in a measurement cell, add distilled water, and measure the volume median particle size (D 50 ) is measured.

[0114] [Volume Median Particle Diameter of Agglomerated Particles] Measuring instrument: "Coulter Multisizer (registered trademark) III" (manufactured by Beckman Coulter, Inc.) Aperture diameter: 50 μm Analysis software: "Multisizer (registered trademark) III Version 3.51" (Beckman Coulter, Inc.) Electrolyte: "Isoton (registered trademark) II" (manufactured by Beckman Coulter, Inc.) 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, 30,000 particles are measured, and the volume median particle size (D 50 ) is found.

[0115] [Circularity of toner particles (fused particles)] Measurement equipment: Flow particle image analyzer "FPIA-3000" (Sysmex Corporation) Preparation of dispersion: A dispersion of toner particles is prepared by diluting it with deionized water so that the solid content concentration is 0.001 to 0.05% by mass. Measurement mode: HPF measurement mode

[0116] [Volume median particle size of toner base particles (D50 ) Measuring instrument: "Coulter Multisizer (registered trademark) III" (manufactured by Beckman Coulter, Inc.) Aperture diameter: 50 μm Analysis software: "Multisizer III (registered trademark) Version 3.51" (Beckman Coulter, Inc.) Electrolyte: "Isoton (registered trademark) II" (manufactured by Beckman Coulter, Inc.) Dispersion: Polyoxyethylene lauryl ether "Emulgen (registered trademark) 109P" (manufactured by Kao Corporation, HLB (Griffin) = 13.6) dissolved in the electrolyte to adjust the concentration to 5% by mass Dispersion conditions: 10 mg of the measurement sample was added to 5 mL of the dispersion, and the mixture was dispersed for 1 minute using an ultrasonic disperser (machine name: US-1 manufactured by SND Corporation, output: 80 W). 25 mL of electrolyte was then added, and the mixture was further dispersed for 1 minute using the ultrasonic disperser to prepare a sample dispersion. Measurement conditions: The sample dispersion was added to 100 mL of the electrolyte to adjust the concentration so that the particle size of 30,000 particles could be measured in 20 seconds. Then, 30,000 particles were measured, and the volume median particle size (D 50 ) is found.

[0117] [Number average particle size of external additives] The particle sizes (average values ​​of major and minor diameters) of 500 particles are measured from a scanning electron microscope (SEM) photograph, and the number average value is calculated.

[0118] Preparation Example 1 of Alkenyl Succinic Anhydride (1) Propylene tetramer (manufactured by Nippon Oil Corporation, trade name: "Light Tetramer") was fractionally distilled at a heating condition of 183 to 208°C to obtain an alkylene compound (a). The obtained alkylene compound (a) had 40 peaks in the gas chromatography mass spectrometry described below. The distribution of the alkylene compound was measured according to the analysis of alkylene compound A by mass spectrometry gas chromatography in JP 2014-013384 A, and the C9H 18 :0.5% by mass, C 10 H 20:4% by mass, C 11 H 22 :20% by mass, C 12 H 24 :66% by mass, C 13 H 26 :9% by mass, C 14 H 28 : 0.5% by mass (6 peaks corresponding to alkylene compounds having 9 to 14 carbon atoms).

[0119] (2) A 1-liter autoclave manufactured by Nitto Koatsu Co., Ltd. was charged with 542.4 g of alkylene compound (a), 157.2 g of maleic anhydride, 0.4 g of the antioxidant "Cherex-O" (triisooctyl phosphite manufactured by SC Organic Chemical Co., Ltd.), and 0.1 g of butylhydroquinone as a polymerization inhibitor. Pressure and nitrogen substitution (0.2 MPaG) were repeated three times. After stirring was initiated at 60°C, the mixture was heated to 230°C over one hour and reacted for six hours. The pressure at the time the reaction temperature was reached was 0.3 MPaG. After the reaction was completed, the mixture was cooled to 80°C, returned to atmospheric pressure (101.3 kPa), and transferred to a 1-liter four-neck flask. The mixture was heated to 180°C with stirring, and the remaining alkylene compound was distilled off at 1.3 kPa over one hour. Subsequently, the mixture was cooled to room temperature (25°C) and then returned to normal pressure (101.3 kPa) to obtain 406.1 g of the target product, alkenyl succinic anhydride A. The average molecular weight of alkenyl succinic anhydride A calculated from the acid value was 268.

[0120] Resin manufacturing example 1 The alcohol component, carboxylic acid components other than trimellitic anhydride, esterification catalyst, and polymerization inhibitor shown in Table 1 were placed in a 10-liter four-neck flask equipped with a dehydration tube equipped with a nitrogen inlet tube, a stirrer, and a thermocouple, and the temperature was raised to 230°C in a mantle heater under a nitrogen atmosphere, followed by polycondensation for 7 hours. The temperature was then lowered to 200°C, trimellitic anhydride was added, and the temperature was raised to 210°C to carry out the polycondensation reaction until the softening point reached the temperature shown in Table 1, yielding amorphous polyester resins (resins A1 and A2).

[0121] [Table 1]

[0122] Resin manufacturing example 2 The raw material monomers and esterification catalyst for the polyester resin other than trimellitic anhydride shown in Table 2 were placed in a 10-liter four-neck flask equipped with a dehydration tube with a nitrogen inlet, a stirrer, and a thermocouple. The flask was heated to 160°C in a mantle heater under a nitrogen atmosphere, and then a mixture of the raw material monomers for the styrene resin, the bireactive monomer, and the polymerization initiator was added dropwise over 1 hour to polymerize. The temperature was raised to 200°C and the reaction was allowed to mature for 1 hour to produce the styrene resin. The temperature was then raised to 230°C over 1 hour to confirm that all solid monomers had melted and reacted. The pressure was then reduced to 8 kPa and the reaction was allowed to proceed for 1 hour. The mixture was then cooled to 210°C, trimellitic anhydride was added, and the reaction was allowed to continue for another 1 hour. The pressure was then reduced to 8 kPa, and the reaction was allowed to proceed until the softening point reached the temperature shown in Table 2, yielding an amorphous composite resin (Resin B1).

[0123] [Table 2]

[0124] Resin manufacturing example 3 The alcohol components and carboxylic acid components shown in Table 3 were placed in a 10-liter four-neck flask equipped with a dehydration tube equipped with a nitrogen inlet tube, a stirrer, and a thermocouple, and the temperature was raised to 200°C over 8 hours in a mantle heater under a nitrogen atmosphere. Then, an esterification catalyst was added, and the reaction was carried out at 8 kPa until the softening point reached the temperature shown in Table 3, yielding crystalline polyester resins (resins C1 to C6).

[0125] Resin manufacturing example 4 The alcohol component, carboxylic acid component, and polymerization inhibitor shown in Table 3 were placed in a 10-liter four-neck flask equipped with a thermometer, a stainless steel stirring rod, a downflow condenser, and a nitrogen inlet tube, and the temperature was raised to 200°C over 8 hours in a nitrogen atmosphere in a mantle heater. Then, an esterification catalyst was added, and the reaction was carried out at 8 kPa until the softening point reached the temperature shown in Table 3, yielding a crystalline polyester resin (resin C7).

[0126] [Table 3]

[0127] Examples 1 to 9, 11 and Comparative Examples 1 to 3 100 parts by weight of the binder resin shown in Table 4, 5 parts by weight of the colorant "Mogul-L" (carbon black, manufactured by Cabot Corporation), 1 part by weight of the charge control agent "T-77" (Hodogaya Chemical Co., Ltd.), and 3 parts by weight of the release agent "WAX-C1" (carnauba wax, melting point: 83°C, manufactured by Kato Yoko Co., Ltd.) were thoroughly stirred in a Henschel mixer and then melt-kneaded using a co-rotating twin-screw extruder "PCM-30" (manufactured by Ikegai Corporation). The operating conditions of the co-rotating twin-screw extruder were a barrel setting temperature of 100°C, a shaft rotation speed of 200 r / min (circumferential speed of shaft rotation: 0.30 m / sec), and a mixture feed rate of 10 kg / h. The resulting kneaded product was cooled and the volume median particle size (D 50 The particles were pulverized and classified so that the particle size became 7.0 μm, thereby obtaining toner base particles.

[0128] To 100 parts by mass of the obtained toner base particles, 1.2 parts by mass of the resin microparticles shown in Table 4, "Aerosil R-972" (hydrophobic silica, manufactured by Nippon Aerosil Co., Ltd., hydrophobic treatment agent: DMDS, number average particle diameter: 16 nm) and 1.4 parts by mass of "RY-50" (hydrophobic silica, manufactured by Nippon Aerosil Co., Ltd., hydrophobic treatment agent: silicone oil, number average particle diameter: 40 nm) were added as external additives, and the mixture was mixed in a Henschel mixer at 3000 r / min for 3 minutes to perform external additive treatment, thereby obtaining a toner.

[0129] Example 10 [Preparation of Resin Dispersion] A 3-liter vessel equipped with a stirrer, reflux condenser, dropping funnel, thermometer, and nitrogen inlet tube was charged with 130 g (65 parts by mass) of Resin A2, 50 g (25 parts by mass) of Resin B1, 20 g (10 parts by mass) of Resin C4, and 200 g of methyl ethyl ketone, and dissolved at 73° C. for 2 hours. A 5% by mass aqueous solution of sodium hydroxide was added to the resulting solution so that the degree of neutralization relative to the acid value of the resin was 60 mol%, and the mixture was stirred for 30 minutes. Next, while maintaining the temperature at 73°C, 700 g of deionized water was added over 50 minutes while stirring at 200 r / min to cause phase inversion emulsification. While maintaining the temperature at 73°C, the resulting solution was distilled off under reduced pressure to obtain a dispersion. Thereafter, while continuing to stir, the dispersion was cooled to 30°C, and deionized water was added to obtain a resin dispersion such that the solids concentration was 20% by mass.

[0130] <Preparation of Colorant Dispersion> In a 1-liter beaker, 116.2 g of colorant "Mogul-L" (carbon black, manufactured by Cabot Corporation), 154.9 g of anionic surfactant "Neopelex (registered trademark) G-15" (15% by mass aqueous solution of sodium dodecylbenzenesulfonate, manufactured by Kao Corporation), and 260 g of deionized water were mixed and dispersed using a homogenizer at room temperature for 3 hours. Deionized water was then added to obtain a colorant dispersion so that the solids concentration became 20% by mass. The volume median particle diameter (D 50 ) was 118 nm.

[0131] <Preparation of release agent dispersion> 50 g of release agent "WAX-C1" (manufactured by Kato Yoko Co., Ltd., carnauba wax, melting point: 83°C), 5 g of cationic surfactant (manufactured by Kao Corporation, trade name: Sanizol B50) and 200 g of deionized water were heated to 95°C, and the release agent was dispersed using a homogenizer. The mixture was then dispersed using a pressure discharge homogenizer, and deionized water was added to obtain a release agent dispersion with a solids concentration of 20% by mass. The volume median particle diameter (D 50 ) was 550 nm.

[0132] <Agglomeration process> 549 g of resin dispersion, 23 g of colorant dispersion, 16 g of release agent dispersion, and 3.3 g of 15% by mass sodium dodecylbenzenesulfonate aqueous solution "Neopelex G-15" (Kao Corporation, anionic surfactant) were placed in a 3-liter four-neck flask equipped with a dehydration tube, a stirrer, and a thermocouple, and mixed at a temperature of 25°C. Next, while stirring the resulting mixture, a solution prepared by dissolving 43 g of ammonium sulfate in 980 g of deionized water and adding a 4.8% by mass potassium hydroxide aqueous solution to adjust the pH to 8.2 was added dropwise over 10 minutes at 25°C, and the temperature was then raised to 58°C over 2 hours to measure the volume median particle diameter (D 50 The temperature was maintained at 58°C until the particle diameter reached 7.0 µm, thereby obtaining a dispersion of aggregated particles.

[0133] <Fusing process> To the obtained dispersion of aggregated particles, 22 g of sodium polyoxyethylene lauryl ether sulfate "EMAL E-27C" (manufactured by Kao Corporation, anionic surfactant, effective concentration 27% by mass) and 1,100 g of deionized water were added. The temperature was then raised to 75°C over 1 hour and maintained at 75°C until the circularity reached 0.970, thereby obtaining a dispersion of fused particles in which the aggregated particles were fused together.

[0134] The resulting dispersion of fused particles was cooled to 30°C, and the dispersion was subjected to suction filtration to separate the solids. The solids were then washed with deionized water at 25°C and suction filtered at 25°C for 2 hours. The solids were then vacuum dried at 33°C for 24 hours using a vacuum constant temperature dryer "DRV622DA" (manufactured by ADVANTEC) to determine the volume median particle diameter (D 50) toner base particles of 7.0 μm were obtained.

[0135] To 100 parts by mass of the obtained toner base particles, 1.2 parts by mass of the resin microparticles shown in Table 4, "Aerosil R-972" (hydrophobic silica, manufactured by Nippon Aerosil Co., Ltd., hydrophobic treatment agent: DMDS, number average particle diameter: 16 nm) and 1.4 parts by mass of "RY-50" (hydrophobic silica, manufactured by Nippon Aerosil Co., Ltd., hydrophobic treatment agent: silicone oil, number average particle diameter: 40 nm) were added as external additives, and the mixture was mixed in a Henschel mixer at 3000 r / min for 3 minutes to perform external additive treatment, thereby obtaining a toner.

[0136] Test Example 1 [Evaluation of fogging under high temperature and high humidity environment (HH fogging)] A non-magnetic, single-component developer, "Monochrome LED Printer B432dnw" (manufactured by Oki Electric Industry Co., Ltd.), modified to allow for variable print speed, was loaded with 50 g of toner. 2,000 images with a coverage rate of 0.3% were printed at a speed equivalent to 30 A4 sheets per minute under an environment of 35°C and 80% relative humidity. A solid white image was printed every 500 sheets, and the power was turned off midway through printing. The toner on the photoreceptor surface was then adhered to the tape with "Scotch® Mending Tape 810" (manufactured by 3M Japan Ltd., width: 18 mm), and the color density was measured using an "exact" image densitometer (manufactured by X-Rite). The difference in color density between the tape itself before and after toner application was calculated, and the average of four measurements from the 500th to 2,000th sheets was calculated. The results are shown in Table 4. The smaller the value, the more suppressed the fogging.

[0137] Test Example 2 [Evaluation of streaks under high temperature and humidity conditions (HH streaks)] A non-magnetic single-component developer, Monochrome LED Printer B432dnw (manufactured by Oki Electric Industry Co., Ltd.), was filled with 50 g of toner, and a printing durability test was conducted at a temperature of 35°C, a relative humidity of 80%, and a print coverage rate of 0.3%. A solid image was printed every 500 sheets, and the sheets were visually inspected for the occurrence of white streaks due to blade filming, and a streak evaluation was conducted. The test was stopped when the occurrence of streaks was confirmed, and was continued up to a maximum of 9,000 sheets. The results are shown in Table 4. In the table, ">9,000" means that no streaks occurred even after 9,000 sheets.

[0138] [Table 4]

[0139] From the above results, it is clear that the toners of Examples 1 to 11 suppress the occurrence of fog and streaks under high temperature and high humidity conditions. In contrast, in Comparative Example 1, in which butanediol, which has four carbon atoms, was used instead of ethylene glycol as the alcohol component of the crystalline polyester resin, and in Comparative Example 2, in which fumaric acid, which has a short carbon chain, was used as the carboxylic acid component, the occurrence of streaks was particularly noticeable, demonstrating the importance of using ethylene glycol, which has two carbon atoms, as the alcohol component.Furthermore, in Comparative Example 3, in which negatively charged resin particles were used, both fog and streaks occurred. [Industrial Applicability]

[0140] The toner for developing electrostatic images of the present invention is suitably used for developing latent images formed in electrophotography, electrostatic recording, electrostatic printing and the like.

Claims

1. A toner for developing electrostatic images, comprising toner base particles containing a crystalline polyester resin C and an amorphous polyester resin A, and an external additive, wherein the crystalline polyester resin C is a polycondensate of an alcohol component containing 80 mol% or more of ethylene glycol and a carboxylic acid component, and the external additive comprises positively charged resin fine particles P.

2. 2. The toner for developing electrostatic images according to claim 1, wherein the content of the fine resin particles P is 0.01 parts by mass or more and 2 parts by mass or less per 100 parts by mass of the toner base particles.

3. 3. The toner for developing electrostatic images according to claim 1, wherein the fine resin particles P contain a polymethyl methacrylate resin.

4. 3. The toner for developing electrostatic images according to claim 1, wherein the content of the resin fine particles P in the external additive is 0.5% by mass or more and 20% by mass or less.

5. 3. The toner for developing electrostatic images according to claim 1, wherein the content of the resin fine particles P is 0.1 parts by mass or more and 50 parts by mass or less based on 100 parts by mass of the crystalline polyester resin C.

6. 3. The toner for developing electrostatic images according to claim 1, wherein the alcohol component and / or the carboxylic acid component of the crystalline polyester resin C contains a monofunctional monomer.

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