Toner for electrostatic charge image development

Abstract

To provide a toner for electrostatic charge image development which is excellent in suppression of photoreceptor fogging.SOLUTION: A toner for electrostatic charge image development contains toner base particles containing a crystalline polyester resin C and an amorphous polyester-based resin A, and an external additive. The crystalline polyester resin C is a polycondensate of an alcohol component and a carboxylic acid component, the alcohol component containing short chain aliphatic diol having 2 or more and 6 or less carbon atoms and / or the carboxylic acid component containing a short chain aliphatic dicarboxylic acid-based compound having 4 or more and 8 or less carbon atoms. The external additive contains a positively chargeable external additive A having a number average primary particle diameter of 6 nm or more and 25 nm or less, and a negatively chargeable external additive B having a number average primary particle diameter of 30 nm or more and 250 nm or less.SELECTED DRAWING: None

Description

[Technical field]

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

[0002] In toners for electrostatic development, external additives are generally added to the toner particles from the viewpoints of fluidity and transferability, and toners using two or more types of particles as external additives are being investigated (see Patent Documents 1 and 2). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2019-12166 A [Patent Document 2] JP 2018-72453 A Summary of the Invention [Problem to be solved by the invention]

[0004] External additives are likely to cause photoreceptor fogging after continuous printing, and in particular, when a crystalline polyester resin is used as the binder resin to improve the low-temperature fixing properties of the toner, the degradation of image quality due to photoreceptor fogging is significant.

[0005] The present invention relates to a toner for developing electrostatic images, which is excellent in suppressing fogging on a photoreceptor. [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 and a carboxylic acid component, the alcohol component contains a short-chain aliphatic diol having from 2 to 6 carbon atoms and / or the carboxylic acid component contains a short-chain aliphatic dicarboxylic acid compound having from 4 to 8 carbon atoms, and the external additive contains a positively charged external additive A having a number-average primary particle diameter of from 6 nm to 25 nm and a negatively charged external additive B having a number-average primary particle diameter of from 30 nm to 250 nm. Effect of the Invention

[0007] The toner for developing electrostatic images of the present invention is highly effective in suppressing fogging on a photoreceptor. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] The toner for developing electrostatic images of the present invention contains toner base particles containing crystalline polyester resin C and amorphous polyester resin A, and external additives, and is characterized in that it contains crystalline polyester resin C obtained by using a short-chain aliphatic diol and / or a short-chain aliphatic dicarboxylic acid compound, small particle size positively charged external additive A, and medium to large particle size negatively charged external additive B. The reason why the toner for developing electrostatic images of the present invention can suppress the occurrence of photoreceptor fogging is not clear, but is presumed to be as follows. Note that the following mechanism is presumed and is not limited thereto.

[0009] In the toner of the present invention, the short-chain aliphatic diol and / or short-chain aliphatic dicarboxylic acid compound is used in the crystalline polyester resin C, so that the ester groups in the resin are close to each other and the overlap of the molecular orbitals increases, resulting in stabilization of the charge on the ester groups. Furthermore, since the ester group is generally a functional group that is easily negatively charged, the negative chargeability of the crystalline polyester resin C is enhanced. The positively charged external additive A is easily electrostatically attached to the surface of the toner base particles containing the highly negatively charged crystalline polyester resin C, and since the positively charged external additive A has a small particle size, it is easy to uniformly coat the surface of the toner base particles. Furthermore, when a negatively charged external additive B having a larger particle size than the positively charged external additive A is used in combination, the negatively charged external additive B adheres to the surface of the toner base particles due to the electrostatic action with the positively charged external additive A, and exerts a spacer effect between the toner particles, suppressing the detachment of the positively charged external additive A from the toner surface. As a result, the detachment of the external additive from the toner is suppressed even under the stress of printing, and it is considered that the occurrence of photoreceptor fogging is suppressed.

[0010] The crystalline polyester resin C is a polycondensation product of an alcohol component and a carboxylic acid component, in which the alcohol component contains a short-chain aliphatic diol and / or the carboxylic acid component contains a short-chain aliphatic dicarboxylic acid compound.

[0011] Examples of the short-chain aliphatic diols include ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, 1,2-pentanediol, 1,3-pentanediol, 1,4-pentanediol, 1,5-pentanediol, 2,3-pentanediol, 2,4-pentanediol, 1,6-hexanediol, 1,4-butenediol, and neopentyl glycol.

[0012] The short-chain aliphatic diol has 2 or more and 6 or less carbon atoms, and preferably 2 or more and 4 or less carbon atoms.

[0013] The content of the short-chain aliphatic diol in the alcohol component is preferably 80 mol % or more, more preferably 85 mol % or more, and even more preferably 90 mol % or more. When the alcohol component contains the following aliphatic monoalcohol, the content is preferably 98 mol % or less, more preferably 95 mol % or less, and even more preferably 93 mol % or less.

[0014] Examples of other alcohol components include aliphatic diols other than short-chain aliphatic diols, alkylene oxide adducts of bisphenol A, aromatic diols such as bisphenol A, hydrogenated bisphenol A, sorbitol, pentaerythritol, glycerin, trimethylolpropane, and other trivalent or higher alcohols.

[0015] Examples of the aliphatic diol other than the short chain aliphatic diol include 1,12-dodecanediol, 1,10-decanediol, etc. The number of carbon atoms is preferably 8 or more, more preferably 10 or more, and is preferably 16 or less, more preferably 14 or less.

[0016] Examples of the short-chain aliphatic dicarboxylic acid compounds include succinic acid (number of carbon atoms: 4), fumaric acid (number of carbon atoms: 4), adipic acid (number of carbon atoms: 6), suberic acid (number of carbon atoms: 8), anhydrides of these acids, and alkyl esters of these acids having 1 to 3 carbon atoms.

[0017] The short-chain aliphatic dicarboxylic acid compound has 4 or more and 8 or less carbon atoms, and preferably 4 or more and 6 or less carbon atoms.

[0018] The content of the short-chain aliphatic dicarboxylic acid compound in the carboxylic acid component is preferably 70 mol % or more, more preferably 80 mol % or more, and even more preferably 90 mol % or more. When the short-chain aliphatic monocarboxylic acid compound described below is contained, the content is preferably 98 mol % or less, more preferably 95 mol % or less, and even more preferably 93 mol % or less.

[0019] Examples of other carboxylic acid components include aliphatic dicarboxylic acid compounds other than short-chain aliphatic dicarboxylic acid compounds, 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.

[0020] Examples of the aliphatic dicarboxylic acid compounds other than the short-chain aliphatic dicarboxylic acid compounds include sebacic acid, dodecanedioic acid, tetradecanedioic acid, etc. The number of carbon atoms is preferably 9 or more, more preferably 10 or more, and is preferably 18 or less, more preferably 16 or less, and even more preferably 14 or less.

[0021] From the viewpoint of charging stability, the alcohol component and / or the carboxylic acid component of the crystalline polyester resin C preferably further contains a monofunctional monomer.

[0022] From the viewpoint of improving hydrophobicity, the monofunctional monomer preferably contains an aliphatic monocarboxylic acid compound and / or an aliphatic monoalcohol, and more preferably contains an aliphatic monocarboxylic acid compound.

[0023] Examples of monofunctional monomers contained in the alcohol component include aliphatic monoalcohols such as capryl alcohol, capric alcohol, lauryl alcohol, myristyl alcohol, palmityl alcohol, stearyl alcohol, and behenyl alcohol.

[0024] From the viewpoint of hydrophobicity, 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, and from the viewpoint of low-temperature fixability, the carbon number is preferably 24 or less, more preferably 23 or less, and even more preferably 22 or less.

[0025] Examples of monofunctional monomers 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 aliphatic monocarboxylic acid compounds such as alkyl esters of these acids in which the alkyl group has 1 to 3 carbon atoms.

[0026] 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. Here, 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.

[0027] The content of the monofunctional monomer in the total amount of the alcohol component and the carboxylic acid component is preferably 2 mol % or more, more preferably 3 mol % or more, and even more preferably 5 mol % or more, 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.

[0028] In this specification, macromonomers and hydroxycarboxylic acids are not included in the alcohol component and the carboxylic acid component.

[0029] In the present invention, a preferred embodiment of the crystalline polyester resin C is a polycondensate of an alcohol component containing 80 mol % or more of a short-chain aliphatic diol having 2 to 6 carbon atoms and a carboxylic acid component containing 70 mol % or more of an aliphatic dicarboxylic acid compound having 9 to 18 carbon atoms; A polycondensate of an alcohol component containing 80 mol% or more of an aliphatic diol having 8 to 16 carbon atoms and a carboxylic acid component containing 70 mol% or more of a short-chain aliphatic dicarboxylic acid compound having 4 to 8 carbon atoms. and the like, and it is preferable that the alcohol component and / or the carboxylic acid component further contain an aliphatic monocarboxylic acid compound in an amount of 2 mol % or more and 30 mol % or less based on the total amount of the alcohol component and the carboxylic acid component.

[0030] The equivalent ratio of the carboxy group of the carboxylic acid component to the hydroxyl group of the alcohol component (COOH group / OH group) 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 fixing property.

[0031] The 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 further, if necessary, 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.

[0032] 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, based on 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, based on 100 parts by mass of the total amount of the alcohol component and the carboxylic acid component. Examples of the polymerization inhibitor include tert-butylcatechol. The amount of 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, per 100 parts by mass of the total amount of the alcohol component and the carboxylic acid component.

[0033] In the present invention, the polyester resin may be modified to such an extent that its properties are not substantially impaired. Examples of modified polyester resins include polyester resins grafted or blocked with phenol, urethane, epoxy, or the like by the methods described in JP-A-11-133668, JP-A-10-239903, JP-A-8-20636, etc., and among the modified polyester resins, urethane-modified polyester resins in which polyester resins are urethane-extended with a polyisocyanate compound are preferred.

[0034] 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, and more preferably 110°C or lower from the viewpoint of low-temperature fixing property.

[0035] The crystallinity of a resin is represented by a crystallinity index defined as the ratio of the softening point to the maximum endothermic peak temperature measured by a differential scanning calorimeter, that is, the value of [softening point / maximum endothermic peak temperature]. The crystalline resin is a resin having a crystallinity index of 0.6 or more, preferably 0.7 or more, more preferably 0.9 or more, and 1.4 or less, preferably 1.2 or less, more preferably 1.1 or less. 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 the resin can be adjusted by the type and ratio of the raw material monomers, and the production conditions (e.g., reaction temperature, reaction time, cooling rate), etc. The maximum endothermic peak temperature refers to the temperature of the peak with the largest peak area among the observed endothermic peaks. In the case of a crystalline resin, the maximum endothermic peak temperature is the melting point.

[0036] 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.

[0037] 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 from the viewpoint of charging stability, it is preferably 20 mgKOH / g or less, more preferably 15 mgKOH / g or less.

[0038] The content of crystalline polyester resin C in the total amount of crystalline polyester resin C and amorphous polyester resin A is preferably 3 mass % or more, more preferably 5 mass % or more, and even more preferably 8 mass % or more from the viewpoint of low-temperature fixability, and is preferably 30 mass % or less, more preferably 25 mass % or less, and even more preferably 20 mass % or less from the viewpoint of heat-resistant storage stability and charging stability.

[0039] As the amorphous polyester resin, an amorphous polyester resin or an amorphous composite resin in which a polyester resin is bonded with a styrene resin is preferred.

[0040] As the amorphous polyester resin, a polycondensation product of an alcohol component containing an alkylene oxide adduct of bisphenol A and a carboxylic acid component containing an aromatic dicarboxylic acid compound is preferable.

[0041] Examples of the alkylene oxide adduct of bisphenol A include those represented by the formula (I):

[0042] [ka]

[0043] (In the formula, 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, each of which is a positive number, and the sum of x and y is 1 or more, preferably 1.5 or more, and 16 or less, preferably 8 or less, more preferably 6 or less, and even more preferably 4 or less.) Preferred is a compound represented by the following formula:

[0044] From the viewpoint of low-temperature fixing ability, 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, even more preferably 95 mol % or more, and even more preferably 100 mol %.

[0045] Examples of other alcohol components include aliphatic diols, diols such as bisphenol A and hydrogenated bisphenol A, and trihydric or higher alcohols such as sorbitol, pentaerythritol, glycerin, and trimethylolpropane.

[0046] Examples of the aromatic dicarboxylic acid compound include phthalic acid, isophthalic acid, terephthalic acid, anhydrides of these acids, and alkyl esters of these acids having 1 to 3 carbon atoms.

[0047] The content of the aromatic dicarboxylic acid compound in the carboxylic acid component is preferably 40 mol % or more, more preferably 50 mol % or more, even more preferably 60 mol % or more, and is preferably 98 mol % or less, more preferably 90 mol % or less.

[0048] Examples of other carboxylic acid components include fumaric acid, maleic acid, succinic acid, succinic acid derivatives substituted with a hydrocarbon group, aliphatic dicarboxylic acids such as glutaric acid, adipic acid, and sebacic acid, trivalent or higher carboxylic acids such as trimellitic acid and pyromellitic acid, anhydrides of these acids, and alkyl esters of these acids having 1 to 3 carbon atoms.

[0049] The content of the trivalent or higher carboxylic acid compound in the carboxylic acid component is preferably 1 mol % or more, more preferably 5 mol % or more, and even more preferably 10 mol % or more, and from the viewpoint of low-temperature fixability, it is preferably 30 mol % or less, more preferably 25 mol % or less, and even more preferably 20 mol % or less.

[0050] The alcohol component may appropriately contain a monohydric alcohol, and the carboxylic acid component may appropriately contain a monovalent carboxylic acid compound.

[0051] From the viewpoint of adjusting the softening point of the polyester resin, the equivalent ratio of the carboxy group of the carboxylic acid component to the hydroxyl group of the alcohol component (COOH group / OH group) is preferably 0.6 or more, more preferably 0.7 or more, even more preferably 0.75 or more, and is preferably 1.2 or less, more preferably 1.15 or less.

[0052] The polycondensation reaction conditions of the alcohol component and the carboxylic acid component of the amorphous polyester resin are similar to those of the crystalline polyester resin, except that the suitable reaction temperature is 160°C or more, more preferably 180°C or more, and 250°C or less, more preferably 240°C or less.

[0053] The polyester resin in the composite resin is similar to the amorphous polyester resin described above, and the styrene-based resin is an addition polymerization product 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").

[0054] The content of the styrene compound, preferably styrene, in the raw material monomer 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.

[0055] The styrene-based resin may also contain, as a raw material monomer, an alkyl (meth)acrylate ester having an alkyl group with 7 or more carbon atoms. Examples of the alkyl (meth)acrylate ester 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 both the case where this group is present and the case where it is not present are included, and when these groups are not present, it indicates that it is normal. Furthermore, "(meth)acrylic acid" refers to acrylic acid, methacrylic acid, or both.

[0056] From the viewpoint of improving the low-temperature fixing property of the toner, the number of carbon atoms in the alkyl group in the (meth)acrylic acid alkyl ester as a raw material monomer of 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.

[0057] The raw material monomers for the styrene-based resin 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 monocarboxylates 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.

[0058] The addition polymerization reaction of raw material monomers for the styrene-based resin 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, or the like, 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.

[0059] 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.

[0060] 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.

[0061] The bireactive monomer is preferably a compound having at least one functional group selected from the group consisting of hydroxyl group, carboxyl group, epoxy group, primary amino group and secondary amino group, preferably hydroxyl group and / or carboxyl group, more preferably carboxyl group and 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 reactivity of polycondensation reaction and addition polymerization reaction, still 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 polyvalent carboxylic acid compound having an ethylenically unsaturated bond such as fumaric acid functions as a raw material monomer of polyester resin. In this case, fumaric acid etc. is not a bireactive monomer but a raw material monomer of polyester resin.

[0062] 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 of the 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 fixing property of the toner. The amount of the bireactive monomer used is preferably 1 part by mass or more, more preferably 2 parts by mass or more, relative to 100 parts by mass of the raw material monomers of the styrene 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 parts by mass or less, more preferably 20 parts by mass or less, and even more preferably 10 parts by mass or less, from the viewpoint of improving the low-temperature fixing property of the toner. Here, the total amount of the raw material monomers of the styrene resin includes the polymerization initiator.

[0063] 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.

[0064] (i) A method in which a step (A) of polycondensation reaction using raw material monomers for a polyester resin is followed by a step (B) of addition polymerization reaction using raw material monomers for a styrene-based resin. In this method, step (A) is carried out under reaction temperature conditions suitable for polycondensation reaction, and the reaction temperature is lowered to carry out step (B) under temperature conditions suitable for addition polymerization reaction. It is preferable that the raw material monomer of the styrene-based resin is 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 of 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 increased again, and if necessary, a raw material monomer of a polyester resin having a valence of 3 or more and serving as a crosslinking agent is added to the polymerization system, so that the polycondensation reaction of step (A) and the reaction with the bireactive monomer can be further promoted.

[0065] (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 addition polymerization reaction, and the reaction temperature is then raised to carry out the polycondensation reaction in step (A) under temperature conditions suitable for polycondensation reaction. When a bireactive monomer is used together with the raw material monomer of the styrene-based resin, the bireactive monomer is involved in both the addition polymerization reaction and the polycondensation reaction. The raw material monomers of 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.

[0066] (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-based resin are carried out under conditions in which they proceed in parallel. In this method, it is preferable to carry out step (A) and step (B) in parallel under reaction temperature conditions suitable for addition polymerization reaction, raise the reaction temperature, add a raw material monomer of a polyester resin having three or more valences as a crosslinking agent to the polymerization system as necessary under temperature conditions suitable for polycondensation reaction, and further carry out the polycondensation reaction of step (A). In this case, under temperature conditions suitable for polycondensation reaction, a polymerization inhibitor can be added to proceed with only the polycondensation reaction. When a bireactive monomer is used, the bireactive monomer is involved in both the addition polymerization reaction and the polycondensation reaction.

[0067] In the above method (i), a prepolymerized polycondensation resin may be used instead of the step (A) in which a polycondensation reaction is carried out. In the above method (iii), when the reaction is carried out under conditions in which the steps (A) and (B) proceed in parallel, a mixture containing raw material monomers for a styrene resin may be dropped into a mixture containing raw material monomers for a polyester resin to carry out the reaction.

[0068] The above methods (i) to (iii) are preferably carried out in the same container.

[0069] The mass ratio of the polyester resin to the styrene-based resin in the composite resin (polyester resin / styrene-based resin) is 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, and 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. In the above calculation, the mass of the polyester resin is the amount obtained by subtracting the amount of reaction water dehydrated by the polycondensation reaction (calculated value) from the mass of the raw material monomers of the polyester resin used, 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.

[0070] 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 fixing ability.

[0071] From the viewpoints of low-temperature fixability and fixing width, the amorphous polyester resin A may be composed of resins having 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 40° C. or less.

[0072] 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, and even more preferably 120°C or higher, from the viewpoint of fixing width, and is preferably 170°C or lower, more preferably 160°C or lower, and even more preferably 150°C or lower, from the viewpoint of low-temperature fixing ability.

[0073] 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 fixing ability.

[0074] The mass ratio of resin AH to resin AL (resin AH / resin AL) is preferably 10 / 90 or more, more preferably 20 / 80 or more, even more preferably 30 / 70 or more, and is preferably 90 / 10 or less, more preferably 80 / 20 or less, even more preferably 75 / 25 or less.

[0075] 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.

[0076] The acid value of the amorphous polyester resin A is preferably 1 mgKOH / g or more, more preferably 3 mgKOH / g or more, from the viewpoint of low-temperature fixing property, and is preferably 20 mgKOH / g or less, more preferably 18 mgKOH / g or less, from the viewpoint of charging stability.

[0077] The content of the amorphous polyester resin A in the total amount of the crystalline polyester resin C and the amorphous polyester resin A is, from the viewpoint of charging stability, 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.

[0078] 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.

[0079] In the toner, the crystalline polyester resin C and the amorphous polyester resin A are contained as binder resins.

[0080] Other examples of the binder resin include vinyl resins such as styrene-acrylic resin, epoxy resin, polycarbonate, polyurethane, and composite resins containing two or more of these resins.

[0081] 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, even more preferably 95% by mass or more, and even more preferably 100% by mass.

[0082] In addition, 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.

[0083] 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.

[0084] As the colorant, dyes, pigments, magnetic materials, etc. used as colorants for toners can be used. For example, 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. can be mentioned. In the present invention, the toner may be either a black toner or a color toner.

[0085] 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.

[0086] Examples of the release agent include hydrocarbon waxes such as polypropylene wax, polyethylene wax, polypropylene-polyethylene 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. These may be used alone or in combination of two or more.

[0087] The melting point of the release agent is preferably 60° C. or higher, more preferably 70° C. or higher, from the viewpoint of charging 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 fixing ability.

[0088] 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.

[0089] 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.

[0090] Examples of the positively charged charge control agent 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 having 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 such resins include "VP435" (manufactured by Clariant), etc.; polyamine resins, such as "AFP-B" (manufactured by Orient Chemical Industry Co., Ltd.); imidazole derivatives, such as "PLZ-2001" and "PLZ-8001" (both manufactured by Shikoku Kasei Corporation); and styrene-acrylic resins, such as "FCA-701PT" and "FCA-201-PS" (manufactured by Fujikura Kasei Co., Ltd.).

[0091] Examples of the negatively chargeable charge control agent include metal-containing azo dyes such as "Varifast Black 3804", "Bontron S-31", "Bontron S-32", "Bontron S-34", and "Bontron S-36" (all manufactured by Orient Chemical Industry Co., Ltd.), "Aizenspiron Black TRH", and "T-77" (manufactured by Hodogaya Chemical Industry Co., Ltd.); metal compounds of benzilic acid compounds such as "LR-147" and "LR-297" (all 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 Industry Co., Ltd.), and "TN-105" (manufactured by Hodogaya Chemical Industry Co., Ltd.); copper phthalocyanine dyes; and quaternary ammonium salts such as "COPY CHARGE NX VP434 (Clariant), nitroimidazole derivatives, and organometallic compounds.

[0092] 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.

[0093] The toner base particles may be a toner obtained by any of the conventionally known methods such as a melt kneading method, an emulsion aggregation method, a suspension polymerization method, etc., but from the viewpoint of charge stability, a pulverized toner by a melt kneading method is preferred. In the case of a pulverized toner by a melt kneading method, for example, a binder resin containing a crystalline polyester resin C and an amorphous polyester resin A, and raw materials such as a colorant, a release agent, and a charge control agent, if necessary, are uniformly mixed in a mixer such as a Henschel mixer, and then melt kneaded in an internal kneader, a single-screw or twin-screw extruder, an open roll type kneader, etc., and cooled, pulverized, and classified to produce the toner.

[0094] 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.

[0095] The external additives include two types of external additives having different particle sizes, a positively charged external additive A (hereinafter also referred to as external additive A) and a negatively charged external additive B (hereinafter also referred to as external additive B).

[0096] The number average primary particle diameter of the positively charged external additive A is 6 nm or more, preferably 7 nm or more, more preferably 8 nm or more, and is 25 nm or less, preferably 22 nm or less, more preferably 20 nm or less.

[0097] The number average primary particle diameter of the negatively charged external additive B is 30 nm or more, preferably 35 nm or more, more preferably 40 nm or more, and 250 nm or less, preferably 230 nm or less, more preferably 200 nm or less.

[0098] From the viewpoint of enhancing the spacer effect, the external additive preferably further contains a positively charged external additive C (hereinafter, also referred to as external additive C) having a medium to large particle size.

[0099] The number average primary particle diameter of the positively charged external additive C is preferably 30 nm or more, more preferably 40 nm or more, even more preferably 50 nm or more, and is preferably 250 nm or less, more preferably 200 nm or less, even more preferably 150 nm or less.

[0100] Examples of the external additive include inorganic particles such as silica, alumina, titania, zirconia, strontium titanate, tin oxide, and zinc oxide, and organic particles such as melamine resin particles and polytetrafluoroethylene resin particles (PTFE). From the viewpoints of charge stability and fluidity, silica is preferable for all of the external additives A to C.

[0101] From the viewpoint of controlling the charge polarity, the inorganic particles are preferably treated with a surface treatment agent, and the charge polarity of the inorganic particles can be imparted with a charge polarity opposite to the charge polarity that the inorganic particles themselves have by the surface treatment agent. For example, silica particles are negatively chargeable, but they can also be used as positively chargeable inorganic particles by introducing a positively chargeable group into the surface treatment agent.

[0102] Examples of general-purpose surface treatment agents include hydrophobic treatment agents such as hexamethyldisilazane (HMDS), polydimethylsiloxane (PDMS), dimethyldichlorosilane (DMDS), cyclic silazane, aminosilane, alkylsilane, and silicone oil.

[0103] Hydrophobic treatment agents such as hexamethyldisilazane (HMDS) and polydimethylsiloxane (PDMS) do not themselves affect the chargeability of inorganic particles. However, by introducing a positive chargeability-imparting group into the hydrophobic treatment agent, it is possible to impart a positive chargeability to negatively charged inorganic particles, and by introducing a negative chargeability-imparting group into the hydrophobic treatment agent, it is possible to impart a negative chargeability to positively charged inorganic particles.

[0104] Examples of the positive charge imparting group include an amino group.

[0105] Commercially available positively charged external additives A include "TG 820F" (8 nm), "TG 7120" (16 nm) (both manufactured by Cabot Specialty Chemicals, Inc., hydrophobic silica), "NA 380SH" (6 nm), "REA 200" (12 nm) (both manufactured by Nippon Aerosil Co., Ltd., hydrophobic silica), etc. The numbers in parentheses indicate the number-average primary particle size.

[0106] Commercially available negatively charged external additives B include "NAX 50" (50 nm) (manufactured by Nippon Aerosil Co., Ltd., hydrophobic silica), "MSN 005L" (80 nm) (manufactured by Teika Co., Ltd., hydrophobic silica), "Lubron L 5F" (200 nm) (manufactured by Daikin Industries, Ltd., PTFE), and "X-24-9600A-100" (100 nm) (manufactured by Shin-Etsu Chemical Co., Ltd., sol-gel silica).

[0107] Commercially available products of the positively charged external additive C include "MSP016" (80 nm) (manufactured by Teika Co., Ltd., hydrophobic silica) and "HDK H05TA" (50 nm) (manufactured by Wacker Co., Ltd., hydrophobic silica).

[0108] The content of the positively charged external additive A is, relative to 100 parts by mass of the toner base particles, preferably 0.2 parts by mass or more, more preferably 0.3 parts by mass or more, even more preferably 0.4 parts by mass or more, and preferably 1.2 parts by mass or less, more preferably 1.0 part by mass or less, even more preferably 0.8 parts by mass or less.

[0109] The content of the negatively charged external additive B is, relative to 100 parts by mass of the toner base particles, preferably 0.5 parts by mass or more, more preferably 0.6 parts by mass or more, even more preferably 0.7 parts by mass or more, and preferably 1.6 parts by mass or less, more preferably 1.4 parts by mass or less, even more preferably 1.2 parts by mass or less.

[0110] From the viewpoint of suppressing fogging of the photoreceptor, it is preferable that the content of the negatively chargeable external additive B is greater than that of the positively chargeable external additive A, and the mass ratio of the positively chargeable external additive A to the negatively chargeable external additive B (positively chargeable external additive A / negatively chargeable external additive B) is preferably 25 / 75 or more, more preferably 30 / 70 or more, even more preferably 33 / 67 or more, and is preferably less than 50 / 50, more preferably 45 / 55 or less, even more preferably 40 / 60 or less.

[0111] The content of the positively charged external additive C is, relative to 100 parts by mass of the toner base particles, preferably 0.5 parts by mass or more, more preferably 0.8 parts by mass or more, even more preferably 1.0 part by mass or more, and is preferably 4.0 parts by mass or less, more preferably 3.0 parts by mass or less, even more preferably 2.0 parts by mass or less.

[0112] From the viewpoint of charging stability, it is preferable that the content of the positively chargeable external additive C is greater than that of the negatively chargeable external additive B, and the mass ratio of the negatively chargeable external additive B to the positively chargeable external additive C (negatively chargeable external additive B / positively chargeable external additive C) is preferably 25 / 75 or more, more preferably 30 / 70 or more, even more preferably 33 / 67 or more, and is preferably less than 50 / 50, more preferably 48 / 52 or less, even more preferably 45 / 55 or less.

[0113] The external addition process by mixing the toner base particles and the external additives can be carried out according to a conventional method, and a mixer such as a Henschel mixer can be used. The external additives A to C 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.

[0114] The toner of the present invention can be used as it is as a toner for one-component development, 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. EXAMPLES

[0115] The present invention will be described in 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.

[0116] [Softening point of resin] Using a flow tester "CFT-500D" (Shimadzu Corporation), 1g of sample is heated at a temperature increase rate of 6℃ / min while applying a load of 1.96MPa with the plunger, and extruding the sample from a nozzle with a diameter of 1mm and a length of 1mm. The amount of plunger descent of the flow tester is plotted against the temperature, and the temperature at which half of the sample has flowed out is taken as the softening point.

[0117] [Maximum endothermic peak temperature of resin] Using a differential scanning calorimeter "Q-100" (manufactured by TA Instruments Japan, Inc.), weigh 0.01 to 0.02 g of sample into an aluminum pan, cool from room temperature (25°C) to 0°C at a rate of 10°C / min, and maintain at 0°C for 1 minute. Then, measure at a rate of 10°C / min. The temperature of the peak with the largest peak area among the observed endothermic peaks is regarded as the maximum endothermic peak temperature. For crystalline resins, the maximum endothermic peak temperature is regarded as the melting point.

[0118] [Glass transition temperature of resin] Using a differential scanning calorimeter "Q-100" (manufactured by TA Instruments Japan Co., Ltd.), 0.01 to 0.02 g of sample is weighed into an aluminum pan, heated to 200°C, and cooled from that temperature 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 the extension of the baseline below the maximum endothermic peak temperature and the tangent line showing the maximum slope from the rising part of the peak to the top of the peak.

[0119] [Acid value of resin] Measurements are performed 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.

[0120] [Melting point of release agent] Using a differential scanning calorimeter "Q-100" (manufactured by TA Instruments Japan Co., Ltd.), 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 amount of heat is measured, and the maximum endothermic peak temperature is taken as the melting point.

[0121] [Volume median particle size of toner base particles (D 50 )〕 Measuring instrument: "Coulter Multisizer (registered trademark) III" (manufactured by Beckman Coulter, Inc.) Aperture diameter: 50μm Analysis software: "Multisizer (registered trademark) III version 3.51" (Beckman Coulter, Inc.) Electrolyte: "Isoton (registered trademark) II" (manufactured by Beckman Coulter, Inc.) Dispersion liquid: Polyoxyethylene lauryl ether "Emulgen (registered trademark) 109P" (manufactured by Kao Corporation, HLB (Griffin) = 13.6) was dissolved in the electrolyte to adjust the concentration to 5% by mass. Dispersion conditions: 10 mg of the measurement sample is added to 5 mL of the dispersion liquid, and dispersed for 1 minute using an ultrasonic disperser (machine name: US-1, manufactured by SND Co., Ltd., output: 80 W). Then, 25 mL of electrolyte is added, and the mixture is further dispersed for 1 minute using the ultrasonic disperser to prepare a sample dispersion liquid. 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 required.

[0122] [Number average primary particle size of external additives] The average particle size refers to the number-average particle size, and is calculated by measuring the particle sizes (average of major and minor diameters) of 500 particles in a scanning electron microscope (SEM) photograph and averaging these by number.

[0123] Preparation of alkenyl succinic anhydride 1 (1) Propylene tetramer (manufactured by Nippon Oil Corporation, trade name: "Light Tetramer") was used and fractionated under heating conditions of 183 to 208°C to obtain an alkylene compound (a). The obtained alkylene compound (a) had 40 peaks in the gas chromatography mass spectrometry described below. The distribution of the alkylene compounds was measured according to the analysis of alkylene compound A by mass spectrometry gas chromatography in JP 2014-013384 A, and the distribution was CH 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).

[0124] (2) 542.4 g of alkylene compound (a), 157.2 g of maleic anhydride, 0.4 g of antioxidant "Chelex-O" (SC Organic Chemical Co., Ltd., Triisooctyl phosphite), and 0.1 g of butyl hydroquinone as a polymerization inhibitor were charged into a 1 L autoclave manufactured by Nitto Koatsu Co., Ltd., and pressurized nitrogen replacement (0.2 MPaG) was repeated three times. After stirring was started at 60 ° C, the temperature was raised to 230 ° C over 1 hour and the reaction was carried out for 6 hours. The pressure when the reaction temperature was reached was 0.3 MPaG. After the reaction was completed, the mixture was cooled to 80 ° C, returned to normal pressure (101.3 kPa), and transferred to a 1 L four-neck flask. The mixture was heated to 180 ° C with stirring, and the remaining alkylene compound was distilled off at 1.3 kPa for 1 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.

[0125] Resin manufacturing example 1 The alcohol component, carboxylic acid component other than trimellitic anhydride, esterification catalyst and cocatalyst shown in Table 1 were placed in a 10-liter four-neck flask equipped with a nitrogen inlet tube, a stirrer and a thermocouple, and the temperature was raised to 235°C under a nitrogen atmosphere, and polycondensation was carried out at 235°C for 6 hours. The temperature was then lowered to 210°C, trimellitic anhydride shown in Table 1 was added, and the mixture was reacted at 210°C for 1 hour, and then the reaction was continued at 210°C under a reduced pressure of 10 kPa until the softening point shown in Table 1 was reached, to obtain an amorphous polyester resin (resin AH1). The physical properties are shown in Table 1.

[0126] Resin manufacturing example 2 The alcohol component, carboxylic acid component other than trimellitic anhydride, esterification catalyst and cocatalyst shown in Table 1 were placed in a 10-liter four-neck flask equipped with a nitrogen inlet tube, a stirrer and a thermocouple, and the temperature was raised to 235°C under a nitrogen atmosphere, and then polycondensation was carried out at 235°C for 6 hours. The temperature was then lowered to 160°C, and a mixture of the bireactive monomer, raw material monomer of the styrene resin and polymerization initiator shown in Table 1 was dropped over 1 hour using a dropping funnel. After the dropwise addition, the temperature was kept at 160°C and the addition polymerization reaction was matured for 1 hour, then the temperature was raised to 200°C and reduced pressure at 10 kPa for 1 hour. After the pressure was released, trimellitic anhydride shown in Table 1 was added, and the mixture was kept at 200°C for 1 hour, and then the temperature was raised from 200°C to 210°C at 10°C / h, and the reaction was carried out at 210°C for 1 hour. Furthermore, the reaction was continued at 210° C. under a reduced pressure of 10 kPa until the softening point shown in Table 1 was reached, to obtain an amorphous composite resin (Resin AL1).

[0127] [Table 1]

[0128] Resin manufacturing example 3 The alcohol component and carboxylic acid component shown in Table 2 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 shown in Table 2 was added, and the reaction was carried out at 8.0 kPa until the softening point shown in Table 2 was reached, obtaining crystalline polyester resins (resins C1 to C3, C5 to C8). The physical properties are shown in Table 2.

[0129] Resin manufacturing example 4 The alcohol component, carboxylic acid component, and polymerization inhibitor shown in Table 2 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, the esterification catalyst shown in Table 2 was added, and the reaction was carried out at 8.0 kPa until the softening point shown in Table 2 was reached, obtaining a crystalline polyester resin (resin C4). The physical properties are shown in Table 2.

[0130] [Table 2]

[0131] Examples 1 to 11 and Comparative Examples 1 to 6 100 parts by mass of the binder resin shown in Table 4, 2.0 parts by mass of a release agent "WE-14" (manufactured by NOF Corporation, ester wax, melting point: 79°C), 10 parts by mass of a polymer type positively charged charge control agent "FCA-201-PS" (manufactured by Fujikura Chemical Industries, Ltd., softening point: 119°C, glass transition temperature: 65°C), 1.0 part by mass of a positively charged charge control agent "Bontron N-79" (manufactured by Orient Chemical Industries Co., Ltd.), and 6 parts by mass of a colorant "REGAL 330" (manufactured by Cabot Specialty Chemicals, Inc., carbon black) were mixed for 1 minute using a Henschel mixer, and then melt-kneaded under the conditions shown below.

[0132] For melt mixing, a co-rotating twin screw extruder "PCM-30" (manufactured by Ikegai Corporation, shaft diameter 2.9 cm, shaft cross-sectional area 7.06 cm) was used. 2The operating conditions were: barrel temperature 100°C, shaft rotation speed 200 r / min (shaft rotation peripheral speed 0.30 m / sec), mixture supply speed 10 kg / h (mixture supply amount per unit cross-sectional area of ​​the shaft 1.42 kg / h cm 2 ) was.

[0133] The kneaded product obtained was cooled and coarsely pulverized using a pulverizer "Rotoplex" (manufactured by Hosokawa Micron Co., Ltd.) and sieved using a sieve with 2 mm openings to obtain a coarsely pulverized product with a volume median particle size of 2 mm or less. The coarsely pulverized product obtained was finely pulverized using a DS2 type air classifier (impingement plate type, manufactured by Nippon Pneumatic Co., Ltd.) by adjusting the pulverization pressure so that the volume median particle size became 8.0 μm. The finely pulverized product obtained was then classified into a volume median particle size (D 50 The static pressure (internal pressure) was adjusted so that the particle diameter became 7.5 μm, and classification was performed to obtain toner base particles.

[0134] 100 parts by weight of the obtained toner base particles and 0.45 parts by weight of external additive A and 0.8 parts by weight of external additive B shown in Table 4 were mixed in a Henschel mixer (manufactured by Mitsui Mining Co., Ltd.) at a rotation speed of 3000 r / min (circumferential speed of 32 m / sec) for 3 minutes to obtain a toner.

[0135] Example 12 A toner was obtained in the same manner as in Example 1, except that 0.45 parts by mass of external additive A, 0.8 parts by mass of external additive B, and 1.2 parts by mass of external additive C shown in Table 4 were used as the external additives.

[0136] Table 3 shows the external additives used in the examples and comparative examples.

[0137] [Table 3]

[0138] Test Example [Photoreceptor Fog] The toner was mounted on a printer "HL-2040" (manufactured by Brother Industries, Ltd.) equipped with a cleanerless development system, and left in an environment of 25°C / 50% RH for 15 hours. Then, under the same environment, 1,000 images with a print rate of 1% were printed under the condition of 20 seconds per page (after printing one page, the next page was printed after a 20-second pause). Next, a solid white print (print rate of 0%) was performed, and the printer was stopped midway through, and the toner in the non-image area on the photoreceptor after development was attached with "Scotch (registered trademark) Mending Tape 810" (manufactured by Sumitomo 3M, Ltd., width: 18 mm), which was then pasted onto a blank sheet of paper. The whiteness of the pasted portion was measured at five equally spaced points in color density using X-Rite eXact (manufactured by X-Rite), and the difference from the color density of the tape itself before the toner was attached was calculated, and the average of the measured values ​​was calculated. The results are shown in Table 4. The smaller the value, the more the photoreceptor fogging was suppressed. The target value for photoreceptor fog was set at 1.5 or less.

[0139] [Table 4]

[0140] From the above results, it is found that the occurrence of photoreceptor fogging is suppressed in the toners of Examples 1 to 12, in comparison with Comparative Examples 1 to 6. It is considered that the external additive is removed from the toners of Comparative Examples 1 to 6, which increases the adhesive force between the toner and the photoreceptor, causing photoreceptor fogging. [Industrial Applicability]

[0141] 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 matrix 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 and a carboxylic acid component, the alcohol component contains a short-chain aliphatic diol having 2 to 6 carbon atoms and / or the carboxylic acid component contains a short-chain aliphatic dicarboxylic acid compound having 4 to 8 carbon atoms, and the external additive comprises a positively charged external additive A with a number average primary particle diameter of 6 nm to 25 nm and a negatively charged external additive B with a number average primary particle diameter of 30 nm to 250 nm.

2. The electrostatic image developing toner according to claim 1, wherein the content of negatively charged external additive B is greater than that of positively charged external additive A.

3. The toner for developing electrostatic images according to claim 1, wherein the short-chain aliphatic dicarboxylic acid compound has 4 to 6 carbon atoms.

4. The electrostatic image developing toner according to claim 1, wherein the number-average primary particle size of the positively charged external additive A is 8 nm or more and 25 nm or less.

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

6. The electrostatic image developing toner according to claim 1, wherein the external additive further contains a positively charged external additive C having a number average primary particle diameter of 30 nm or more and 250 nm or less.